|PEC-1||Input/ Output Current Ripple Cancellation and RHP Zero Elimination in a Boost Converter using an Integrated Magnetic Technique||This paper presents a novel integrated magnetic boost converter (IMBC) with both input/output current ripple cancellation and right-half-plane (RHP) zero elimination. The input inductor, output inductor, and the ripple cancellation network auxiliary inductor of the proposed IMBC have been integrated in one magnetic core. Two extra capacitors were added to achieve input and output current ripple cancellation. Therefore, the input current ripple of the IMBC dropped to one-twelfth of the original in a conventional boost converter, and the output current worked in continuous-conduction-mode with very small ripple. Meanwhile, the proposed IMBC has eliminated the RHP zero of the boost converter, which means higher bandwidth can be reached. The using of the integrated magnetic technique not only performs above advantages but also shows great potential for reducing the weight and volume of dc–dc converter. Finally, three 36 V input, 50 V output and 500 W prototypes operating at 100 kHz are implementedto verify the expected performance. The experimental results show that the proposed IMBC can achieve both input and output current ripple cancellation and RHP zero elimination with the maximum efficiency of 96.8%. All these advantages of the IMBC are very important especially in high dynamic response, high efficiency, and high-power application.||2015|
|PEC-2||High Step-Up Converter With Three-Winding Coupled Inductor for Fuel Cell Energy Source Applications||This paper presents a high step-up converter for fuel cell energy source applications. The proposed high step-up dc–dc converter is devised for boosting the voltage generated from fuel cell to be a 400-V dc-bus voltage. Through the three-winding coupled inductor and voltage doublers circuit, the proposed converter achieve high step-up voltage gain without large duty cycle. The passive lossless clamped technology not only recycles leakage energyto improve efficiency but also alleviates large voltage spike to limit the voltage stress. Finally, the fuel cell as input voltage source 60–90 V integrated into a 2-kW prototype converter was implemented for performance verification. Under output voltage 400-V operation, the highest efficiency is up to 96.81%, and the full-load efficiency is 91.32%.||2015|
|PEC-3||Derivation, Analysis, and Comparison of Nonisolated Single-Switch High Step-up Converters With LowVoltage Stress||This paper presents no isolated single-switch high step-up converters with low voltage stress. Based on the conventional fly back converter, one single-switch high step-up converter is derived. The voltage stresses on the switch and diodes are limited by using a clamping diode and voltage doublers structure. Also, to further reduce the voltage stresses of them, another single-switch high step-up converter is proposed simply by using one additional capacitor and rearranging the components. Thus, lower voltage rated switch and diodes can be used, which results in higher efficiency. The operational principle, analysis and design considerations of each converter are presented in this paper. The validity of this study is confirmed by the experimental results from24 V input and 250 V/125 W output prototype.||2015|
|PEC-4||The Worst Conducted EMI Spectrum of Critical Conduction Mode Boost PFC Converter||The switching frequency of the boost power factor correction (PFC) converter operating in critical conduction mode(CRM) varies in a line cycle, making the conducted electromagnetic interference (EMI) spectra of the converter appear great differences under different input voltage and load conditions. The EMI filter should be designed according to the worst conducted EMI spectrum of the converter, so as to suppress the conducted EMI of the converter to be lower than the standard limits under all working conditions. This paper analyzes the characteristics of the common-mode (CM) and differential-mode (DM) noise spectra of the CRM boost PFC converter, and discusses the effects of the varied switching frequency on the peak, quasi-peak (PK), and average (AV) conducted EMI spectra. It is revealed that, for the conducted EMI limits defined in EN55022 class B, which are specified within 150 kHz to 30 MHz, the EMI filters required for suppressing the QP spectra of the conducted EMI of the CRM boost PFC converter are larger than that for suppressing the AV spectra, and the QP values of the conducted EMI under all working conditions are lower than a certain maximum boundary. The input voltage and load conditions for the worst CM and DM noise spectra of the converter are derived in this paper, thus the repetitive measurements and numerical calculations are avoided. A CRM boost PFC converter prototype is fabricated, and the evaluation of the measured conducted EMI spectra and the EMI filter design example verified the theoretical analysis||2015|
|PEC-5||Robust Sliding-Mode Control Design for a Voltage Regulated Quadratic Boost Converter||A robust controller design to obtain output voltage regulation in a quadratic boost converter with high dc gain is discussed in this paper. The proposed controller has an inner loop based on sliding-mode control whose sliding surface is defined for the input inductor current. The current reference value of the sliding surface is modified by a proportional-integral compensator in an outer loop that operates over the output voltage error. The stability of the two-loop controller is proved by using the Rout– Hurwitz criterion, which determines a region in the Kp − KiPlane, where the closed-loop system is always stable. The analysis of the sliding-mode-based control loop is performed by means of the equivalent control method, while the outer loop compensator is derived by means of the Nyquist-based Robust Loop Shaping approach with the M-constrained Integral Gain Maximization technique. Robustness is analyzed in depth taking into account the parameter variation related with the operation of the converter in different equilibrium points. Simulations and experimental results are presented to validate the approach for a 20–100-W quadratic boost converter stepping-up a low dc voltage (15–25-V dc) to a 400-V dc level.||2015|
|PEC-6||A Non isolated Multiinput Multioutput DC–DC Boost Converter for Electric Vehicle Applications||A new nonisolated multiinput multioutput dc–dc boost converter is proposed in this paper. This converter is applicable in hybridizing alternative energy sources in electric vehicles. In fact, by hybridization of energy sources, advantages of different sources are achievable. In this converter, the loads power can be flexibly distributed between input sources. Also, charging or discharging of energy storages by other input sources can be Controlled properly. The proposed converter has several outputs with different voltage levels which makes it suitable for interfacing to multilevel inverters. Using of a multilevel inverter leads to reduction of voltage harmonics which, consequently, reduces torque ripple of electric motor in electric vehicles. Also, electric vehicleswhich using dc motor have at least two different dc voltage levels,one for ventilation system and cabin lightening and other for supplying electric motor. The proposed converter has just one inductor. Depending on charging and discharging states of the energy storage system (ESS), two different power operation modes are defined for the converter. In order to design the converter control system, small-signal model for each operation mode is extracted. The validity of the proposed converter and its control performance are verified by simulation and experimental results for different operation conditions.||2015|
|PEC-7||High-Frequency-Fed Unity Power-Factor AC–DC Power Converter With One Switching Per Cycle||This paper presents a power converter and its control circuit for high-frequency-fed ac to dc conversion. Based on the resonant technique, the input current is shaped to be sinusoidal and is forced to follow the high-frequency sinusoidal input voltage so as to achieve unity power factor. With the proper selection of the characteristic impedance of the resonant tank, the converter is able to perform the function of a buck, boost, or buck–boost converter. The initial condition of the resonant tank is used to control the output voltage gain of the converter. Since all the switches are operated at the fundamental frequency of the input ac source, the switching loss of the converter is small. A control scheme is also proposed for the converter. proof-of-concept prototype operating at 400 kHz is constructed and its performance is experimentally measured. Results show that the proposed converter operates as theoretically anticipated.||2015|
|PEC-8||Multicell Switched-Inductor/Switched-Capacitor Combined Active-Network Converters||High step-up voltage gain dc/dc converters are widely used in renewable energy power generation, uninterruptible power system, etc. In order to avoid the influence of leakage inductor in coupled inductors based converters, switched-inductor boost converter (SL-boost), switched-capacitor boost converter (SC-boost) and active-network converter (ANC) have been developed. With the transition in series and parallel connection of the inductors andcapacitors, high step-up voltage conversion ratio can be achieved. This paper discusses the characteristics of the switched inductor and switched-capacitor cell; makes some comparisons between the ANC and boost converter. Based on the aforementioned analysis, this paper proposed the multicell switched-inductor/ switched capacitorcombined active network converters (MSL/SC-ANC). The proposed converters combine the advantages of SL/SC unit
and active-network structure. Compared with previous high step-up converters, the novel converter provides a higher voltage conversion ratio with a lower voltage/current stress on the power devices, moreover, the structure of proposed SL/SC-ANC is very flexible, which means the quantity of SL and SC cells can be adjusted according to required voltage gain. A 20 times gain prototype is designed as an example to show the design procedure. Theoretical
analysis and experimental results are presented to demonstrate the feature of the proposed converter.
|PEBC||Robust Control for PWM-Based DC–DC Buck Power Converters With Uncertainty ViaSampled-Data Output Feedback||This paper investigates the sampled-data output feedback control problem for dc–dc buck power converters taking consideration of components uncertainties. A reduced-order observer and a robust output feedback controller, both in the sampled-data form, have been explicitly constructed with strong robustness in the presence of uncertain parameters. A delicate stability analysis process is presented to show that, by carefully selecting the design gains and the tunable sampling period, the output voltage of the hybrid closed-loop dc–dc buck converter system will globally asymptotically tend to the desired value even though the separation principle is out of reach and the controller is only switched at the sampling points. The proposed controller consists of a set of linear difference equations which will lead to direct and easier digital implementation. Numerical simulations and experimental results are shown to illustrate the performance of the proposed control scheme.||2015|
DC -DC CONVERTER
|PEDC-1||Modular Multilevel DC/DC Converters With Phase-Shift Control Scheme for High-Voltage DC-Based Systems||In this paper, by investigating the topology derivation principle of the phase-shift-controlled three-level dc/dc converters, the modular multilevel dc/dc converters, by integrating the full bridge converters and three-level flying capacitor circuit, are proposed for the high step-down and high power dc-based systems. The high switch voltage stress in the primary side is effectively reduced by the full-bridge modules in series. Therefore, the low-voltage rated power devices can be employed to obtain the benefits of low conduction losses. More importantly, the voltage auto balance ability among the cascaded modules is achieved by the inherent flying capacitor, which removes the additional possible active components or control loops. In addition, zero-voltage-switching performance for all the active switches can be provided due to the phase-shift control scheme, which can reduce the switching losses. The circuit operation and converter performance are analyzed in detail. Finally, the performance of the presented converter is verified by the simulation and experimental results from a 2-kW prototype.||2015|
|PEDC-2||Analysis and Design Considerations of LLCC Resonant Multioutput DC/DC LED Driver With Charge Balancing and Exchanging of Secondary Series Resonant Capacitors||A new rectifier for multi output LED driver is proposed based on a charge exchanging and balancing principle in the secondary resonant capacitors. Combined with common ground rectifier and LLCC resonant topology, a four-output dc–dc LED driver is proposed with minimum quantity of secondary charge balancing capacitors. In the LLCC topology, the secondary side resonant capacitors can be used as dc blocking and charge balancing capacitors. The proposed LED driver can automatically share the average output currents by the charge balancing and exchanging among secondary resonant capacitors. The operating principle and the brief design guidelines for the four-output LLCC resonant dc–dc converter are presented. The guaranteed current sharing capability of the proposed four-output LED driver is also analyzed thoroughly. Finally, a 150 W four outputs LLCC resonant dc–dc LED driver is built-up to verify the theoretical analysis.||2015|
|PEDC-3||Naturally Clamped Zero-Current Commutated Soft-Switching Current-Fed Push–Pull DC/DC Converter: Analysis, Design, and Experimental Results||The proposed converter has the following features: 1) zero-current commutation (ZCC) and natural voltage clamping(NVC) eliminate the need for active-clamp circuits or passive snubbers required to absorb surge voltage in conventional current-fed topologies. 2) Switching losses are reduced significantly owing to zero-current switching of primary-side devices and zero-voltage switching of secondary-side devices. Turn-on switching transition loss of primary devices is also negligible. 3) Soft switching and NVC are inherent and load independent. 4) The voltage across primary-side device is independent of duty cycle with varying input voltage and output power and clamped at rather low reflected output voltage enabling the use of low-voltage semiconductor devices. These merits make the converter good candidate for interfacing low-voltage dc bus with high-voltage dc bus for higher current applications. Steady state, analysis, design, simulation, and experimental results are presented.||2015|
|PEDC-4||A High Gain Input-Parallel Output-Series DC/DC Converter With Dual Coupled Inductors||High voltage gain dc–dc converters are required in many industrial applications such as photovoltaic and fuel cellEnergy systems, high-intensity discharge lamp (HID), dc back-up energy systems, and electric vehicles. This paper presents a novel input-parallel output-series boost converter with dual coupled inductors and a voltage multiplier module. On the one hand, the primary windings of two coupled inductors are connected in parallel to share the input current and reduce the current ripple at the input. On the other hand, the proposed converter inherits the meritsof interleaved series-connected output capacitors for high voltage gain, low output voltage ripple, and low switch voltage stress. Moreover, the secondary sides of two coupled inductors are connected in series to a regenerative capacitor by a diode for extending the voltage gain and balancing the primary-parallel currents. In addition, the active switches are turned on at zero current and the reverse recovery problem of diodes is alleviated by reasonable leakage inductances of the coupled inductors. Besides, the energy of leakage inductances can be recycled. A prototype circuit rated 500-W output power is implemented in the laboratory, and the experimental results shows satisfactory agreement with the theoretical analysis.||2015|
|PEDC-5||A Novel Load Adaptive ZVS Auxiliary Circuit for PWM Three-Level DC–DC Converters||Three-level PWM dc–dc converters convert high dc voltage (>500 V) generally at the output of a three-phaseac–dc PWM rectifier in ac–dc converters to an isolated dc output voltage which can be used to power data center loads. Strict efficiency requirements at loads from 20% to 50% of full load of ac–dc converters for telecom applications have been introduced by energy star enforcing industries to improve efficiency of the dc–dc converter in an ac–dc converter powering data-center loads at those loads. High-efficiency requirements at low and mid loadsin high switching frequency PWM dc–dc three-level converters implemented with MOSFETs can be achieved by reducing switching losses through optimized load adaptive ZVS for the entire load range. In this paper, a simple yet novel load adaptive ZVS auxiliary circuit for three-level converter is proposed for so that the resulting three-phase ac–dc converter can meet energy star platinum efficiency standard. The operation of the proposed dc–dc converter is described, analyzed, and validated by experimental results from an industrial prototype of a three-phase ac–dc converter comprising of a front-end three-phase boost PWM rectifier followed by the proposed converter.||2015|
|PEDC-6||Hybrid Transformer ZVS/ZCS DC–DC Converter With Optimized Magnetics and Improved Power Devices Utilization for Photovoltaic Module Applications||This paper presents a no isolated, high boost ratio dc–dc converter with the application for photovoltaic (PV) modules. The proposed converter utilizes a hybrid transformer to incorporate the resonant operation mode into a traditional high boost ratio active-clamp coupled-inductor pulse-width-modulation dc– dc converter, achieving zero-voltage-switching (ZVS) turn-on of active switches and zero-current-switching turn-off of diodes. Asa result of the inductive and capacitive energy being transferred simultaneously within the whole switching period, power device utilization (PDU) is improved and magnetic utilization (MU) is optimized. The improved PDU allows reduction of the silicon area required to realize the power devices of the converter. The optimized MU reduces the dc-bias of magnetizing current in the magnetic core, leading to smaller sized magnetic. Since the magnetizing current has low dc-bias, the ripple magnetizing current can be utilized to assist ZVS of main switch, while maintaining low root mean- square (RMS) conduction loss. The voltage stresses on the active switches and diodes are maintained at a low level and are ndependent of the wide changing PV voltages as a result of the resonant capacitor in series in the energy transfer loop. The experimental results based on 250Wprototype circuit show 97.7% peak efficiency and system CEC efficiencies greater than 96.7% over 20 to 45 V input voltages. Due to the high efficiency over wide power range, the ability to operate with a wide variable input voltage and compact size, the proposed converter is an attractive design for PV module applications.||2015|
|PEDC-7||Hybrid-Type Full-Bridge DC/DC Converter With High Efficiency||This paper presents a hybrid-type full-bridge dc/dc converter with high efficiency. Using a hybrid control scheme with a simple circuit structure, the proposed dc/dc converter has a hybrid operation mode. Under a normal input range, the proposed converter operates as a phase-shift full-bridge series-resonant converter that provides high efficiency by applying soft switching on all switches and rectifier diodes and reducing conduction losses.When the input is lower than the normal input range, the converter operates as an active-clamp step-up converter that enhances an operation range. Due to the hybrid operation, the proposed converter operates with larger phase-shift value than the conventional converters under the normal input range. Thus, the proposed converter is capable of being designed to give high power conversion efficiency and its operation range is extended. A 1-kW prototype is implemented to confirm the theoretical analysis and validity of the proposed converter.||2015|
|PEI-1||Universal Integrated Synchronization and Control for Single-Phase DC/AC Converters||The universal integrated synchronization and control (UISC) is proposed to operate a single-phase dc/ac converter inboth grid-connected (GC) and stand-alone (SA) modes and offer seamless transition between these modes without any reconfiguration of control structure. As a matter of fact, the UISC does not need to use an islanding detection algorithm in the conventional sense. In GC mode, the UISC controls the real and reactive powers independently. In SA mode, it provides voltage and frequency support. The UISC is not based on direct current control or direct output voltage control. It adjusts the internal converter voltage through a nonlinear mechanism that amounts to the control of the current in GC mode and the voltage in SA mode. The UISC does not require a separate synchronization unit such as a phase-locked loop (PLL). In principle, the UISC is analogous to the combined governor and automatic voltage regulator controls in a synchronous machine (SM). In this sense, it may be considered among the converters that mimic the SMs such as the synchronverter. The proposed UISC is arguably the most unified method that can address different modes of operation of a converter within a micro grid environment without control switching actions. This paper presents the derivations, stability analysis, and numerical results to illustrate the performance of the proposed controller in a single phase situation. A mathematical analysis on the analogies and differences between the UISC and some similar methods is also presented.||2015|
|PEI-2||Predictive Control Method With Future Zero-Sequence Voltage to Reduce Switching Losses in Three-Phase Voltage Source Inverters||This paper proposes a predictive control method with zero-sequence voltage injection to efficiently reduce the switching losses of three-phase voltage source inverters (VSIs). In the proposed predictive control method, three-phase future voltage references modified by a zero-sequence voltage injection are generatedto clamp one of the three legs with the largest load current. Furthermore, the future zero-sequence voltage, which is produced online with the future voltage and current references in every sampling period, optimally adjusts the clamping duration on each leg, depending on the load angle. In addition, the proposed method selects the zero vector on the basis of the polarity of the future zero sequence voltage to reduce the switching losses. Using a predefined cost function, the proposed predictive control scheme chooses one optimal voltage state closest to the future voltage references modified by the zero-sequence voltage injection. Therefore, the proposed predictive control method can perform load current control and minimize the switching losses of the VSI under any load condition regardless of the load angle.||2015|
|PEI-3||An Adaptive Droop DC-Bus Voltage Controller for a Grid-Connected Voltage Source Inverter With LCL Filter||This paper presents a very fast dc-bus voltage controller for a single-phase grid-connected voltage-source inverter(VSI) with an LCL output filter used in renewable energy applications. In single-phase grid-connected inverters, the design of the dc-bus voltage control scheme is very challenging due to the presence of a second harmonic ripple across the dc-bus voltage. The proposed dc-bus voltage control scheme is able to address the difficulties introduced by the second-harmonic ripple. The dc-bus voltage controller is based on an adaptive droop control technique, which is able to provide a very fast transient response for the closed-loop system and ensures the optimal operation of the VSI during steady-state conditions. Also, the simple structure of the controller makes it very practical for grid-connected VSIs used in renewable energy power conditioning systems. Theoretical analysis and experimental results demonstrate the superior performance of the proposed control approach compared to conventional dc-bus voltage control schemes.||2015|
|PEI-4||Swinging Bus Operation of Inverters for Fuel Cell Applications With Small DC-Link Capacitance||For reliability reasons, the employment of small film capacitors instead of electrolytic ones is an interesting alternative for the dc-link in single-phase inverters for fuel cell applications. Due to the low capacitance that can be accomplished at an acceptable cost using this technology, there are large low-frequency voltage fluctuations (100/120 Hz and harmonics) in the dc-link caused by the double-frequency power transfer. By allowing these variations in the bus, the capacitor bank absorbs the current ripple from the inverter to avoid detrimental oscillations in the fuel cell. Traditional control strategies for inverters are usually designed to operate with nearly constant input voltage and are not able to effectively handle large (e.g., > 10%) low-frequency input voltage fluctuations. This paper introduces the analysis of a swinging bus in the context of fuel cell standalone applications (i.e., voltage–Source inverters) and proposes a nonlinear control approach to operate inverters with very large input voltage swing: the natural switching surface (NSS). Under the proposed scheme, the inverter presents excellent dynamic and steady-state characteristics, even at moderate switching frequency (e.g., 3.6 kHz). In order to illustrate the superior performance of the NSS, a comparison to a proportional-resonant (PR) controller is performed. Unlike the linear compensator, the NSS is able to reject the large bus voltage oscillations and achieve high-quality output voltage with low total harmonic distortion (THD). Simulation and experimental results are provided to illustrate the behavior of the swinging bus and to validate the NSS control scheme under the proposed demanding operating conditions.||2015|
|PEI-5||Power Controllability of a Three-Phase Converter With an Unbalanced AC Source||Three-phase dc–ac power converters suffer from power oscillation and over current problems in case of the unbalancedac source voltage that can be caused by grid/generator faults. Existing solutions to handle these problems are properly selecting and controlling the positive- and negative-sequence currents. In this paper, a new series of control strategies which utilize the zero sequence components are proposed to enhance the power control ability under this adverse condition. It is concluded that by introducing proper zero-sequence current controls and corresponding circuit configurations, the power converter can enable more flexible control targets, achieving better performances in the delivered power and the load current when suffering from the unbalanced ac voltage.|
|PEI-6||A Novel Control Strategy of Suppressing DC Current Injection to the Grid for Single-Phase PV Inverter||Photovoltaic (PV) inverters without the isolation transformer become more attractive due to higher efficiency andlower weight. However, it may have dc offset current problem and is critical to the power system. In this paper, a novel control strategy of suppressing dc current injection to the grid for PV inverters is investigated. It is based on the idea of accurately sensing the dc offset voltage of PV inverter output. Since dc component of the inverter output can be eliminated, dc injection to the grid can be effectively suppressed. Finally, the control scheme is verified by the experiment.||2015|
|PEI-7||Switching State Vector Selection Strategies for Paralleled Multilevel Current-Fed Inverter Under Unequal DC-Link Currents Condition||A paralleled multilevel inverter topology consists of n three-phase three-level current-fed inverters (CFIs) connected in parallel on ac side. AC currents with (2n + 1) levels can be generated utilizing redundant switching states when all three-level inverters have equal dc-link currents. However, the multilevel space vector diagram gets modified, redundancy in the switching states is lost and the multilevel current pattern changes when the dclink current of all inverters is not the same. This introduces low frequency harmonics in output current, thereby deteriorating total harmonic distortion (THD). The presence of low-frequency components in the output current could be avoided by selecting suitable switching state vectors and ensuring proper time sharing among these vectors. Two methods to select such switching state vectors are proposed in this paper. In the first method, a reference current space vector is realized using the nearest switching state vectors. However, this method results in low-frequency pulsation in dc-link voltage of each inverter. In the second method, the switching state vectors are chosen to eliminate this low-frequency pulsation. Effectiveness of these methods is experimentally validated for a five-level CFI. Further, performance of these methods is compared based on efficiency, THD, and dc-link voltage ripple for various inequality ratios in dc-link currents.||2015|
|PEI-8||A High-Efficiency MOSFET Transformer less Inverter for Non isolated Micro inverter Applications||State-of-the-art low-power-level metal–oxide–semiconductor field-effect transistor (MOSFET)-based transformer lessphotovoltaic (PV) inverters can achieve high efficiency by using latest super junction MOSFETs. However, theseMOSFET-based inverter topologies suffer from one or more of these drawbacks: MOSFET failure risk from body diode reverse recovery, increased conduction losses due to more devices, or low magnetic utilization. By splitting the conventional MOSFET based phase leg with an optimized inductor, this paper proposes a novel MOSFET-based phase leg configuration to minimize these drawbacks. Based on the proposed phase leg configuration, a high efficiency single-phase MOSFET transformer less inverter is presented for the PV micro inverter applications. The pulse width modulation (PWM) modulation and circuit operation principle are then described. The common-mode and differential-mode voltage model is then presented and analyzed for circuit design. Experimental results of a 250Whardware prototype are shown to demonstrate the merits of the proposed transformer less inverter on non isolated two-stage PV micro inverter application.||2015|
|PEI-9||Frequency Adaptive Selective Harmonic Control for Grid-Connected Inverters||A frequency adaptive selective harmonic control (FA-SHC) scheme is proposed. The FA-SHC method is developed from a hybrid SHC scheme based on the internal model principle, which can be designed for grid-connected inverters to optimally mitigate feed-in current harmonics. The hybrid SHC scheme consists of multiple parallel recursive (nk ±m)-order (k=0, 1, 2, . . ., andm ≤ n/2) harmonic control modules with independent control gains, which can be optimally weighted in accordance with the harmonic distribution. The hybrid SHC, thus, offers an optimal tradeoff among cost, complexity, and also performance in terms of high accuracy, fast response, easy implementation, and compatible design. The analysis and synthesis of the hybrid SHC are addressed. More important, in order to deal with the harmonics in the presence of grid frequency variations, the hybrid SHC is transformed into the FA-SHC, being the proposed fractional order controller, when it is implemented with a fixed sampling rate. The FA-SHC is implemented by substituting the fractional order elements with the Lagrange-polynomial-based interpolation filters. The proposed FA-SHC scheme provides fast on-line computation and frequency adaptability to compensate harmonics in grid-connected applications, where the grid frequency is usually varying within a certain range (e.g., 50 ± 0.5 Hz). Experimentaltests have demonstrated the effectiveness of the proposed FA-SHC scheme in terms of accurate frequency adaptability and also fast transient response.||2015|
|PEI-10||An Extended Lyapunov-Function-Based Control Strategy for Single-Phase UPS Inverters||In this study, an extended Lyapunov-function-based control strategy that assures global asymptotic stability is proposed for single-phase UPS inverters. The Lyapunov function is formed from the energy stored in the inductor and capacitor due to the fact that the system states converge to the equilibrium point if the total energy is continuously dissipated. It is shown analytically that the classical Lyapunov-function-based control leads to a globally asymptotically stable system at the expense of steady-state errors in the output voltage, which exist due to the lack of outer voltage loop in the control input. Therefore, an extended Lyapunovfunction-based control strategy is proposed, which eliminates the steady-state error without destroying the global stability of the closed-loop system. The steady state and dynamic performance of the proposed control strategy has been tested by simulations and experiments under resistive and diode bridge rectifier loads. The results obtained from a 1-kW inverter demonstrate that the developed control strategy not only offers global stability, but also leads to good quality sinusoidal voltage with a reasonably low THD, almost zero steady-state error in the output voltage, and fast dynamicresponse under linear and nonlinear loads.||2015|
|PED-1||A High Power Factor, Electrolytic Capacitor-Less AC-Input LED Driver Topology With High Frequency Pulsating Output Current||Light emitting diode (LED) lamps with ac-input (50or 60 Hz) usually require an electrolytic capacitor as the dc-linkcapacitor in the driver circuit to: 1) balance the energy between the input and output power, and 2) to minimize the low-frequency component of the output ripple across the LEDs. The lifetime of this capacitor, however, is much shorter than that of a LED. To maximize the potential lifetime of the LED lighting system, a new pulsating current driving LED driver that does not require any electrolytic capacitors or complicated control circuits to minimizethe low-frequency (i.e., 100 or 120 Hz) output ripple is proposed in this paper. The proposed circuit is simple and a single-switch topology is designed to simplify the controller design. The proposed circuit is able to reduce the energy storage capacitance to a few microfarads range, so that film capacitor can be used to replace the unreliable electrolytic capacitor. The circuit operating principles and its theoretical analysis are provided in this paper. Simulation and experimental results are given on a 9-W LED lamp to highlight the merits of the proposed circuit.||2015|
|PED-2||Design and Implementation of a Single-Stage Driver for Supplying an LED Street-Lighting Module WithPower Factor Corrections||This paper proposes a novel single-stage light emitting diode (LED) driver for street-lighting applications with power factor corrections (PFC). The presented driver integrates a modified bridgeless PFC ac–dc converter with a half-bridge-type LLC dc–dc resonant converter into a single-stage conversion circuit topology. The proposed ac–dc resonant driver provides input current shaping, and it offers attributes of lowered switching losses to the soft-switching functions obtained on two power switches and two output-rectifier diodes. The proposed driver features cost effectiveness, high circuit efficiency (>92%), high power factor (>0.99) and low input current total harmonics distortion (<8%). A prototype driver is developed for supplying a 144-W-rated LED street-lighting module with utility-line input voltages ranging from 100 to 120 V, and experimental results demonstrate the functionalitiesof the proposed LED driver.||2015|
|PED-3||Power Flow Analysis and Critical Design Issues of Retrofit Light-Emitting Diode (LED) Light Bulb||For retrofit applications, some high-brightness light-emitting diode (LED) products have the same form factorrestrictions as existing incandescent light bulbs. Such form factor constraints may restrict the design and optimal erformance of the LED technology. In this paper, some critical design issues for commercial LED bulbs designed for replacing E27 incandescent lamps are quantitatively analyzed. The analysis involves power audits on such densely packed LED systems so that the amounts of power consumption in: 1) the LED wafer; 2) the phosphor coating; and 3) the lamp translucent cover are quantified. The outcomes of such audits enable R&D engineers to identify the critical areas that need further improvements in a compact LED bulb design. The strong dependence of the luminous output of the compact LED bulb on ambient temperature is also highlighted.||2015|
|PED-4||Proportional-Integral (PI) Compensator Design ofDuty-Cycle-Controlled Buck LED Driver||A discrete time-domain modeling and design for the duty-cycle-controlled buck light-emitting diode (LED) driver ispresented in this paper. The discrete time-domain equation representing the buck LED driver is derived and linearized about the equilibrium state. Also the switching control law, the proportional integral (PI) compensator is used here as an example of the error amplifier, is liberalized about the equilibrium state. The liberalized buck LED driver and the control law are then combined to arrive at a liberalized duty-cycle-controlled buck LED driver. The root locus method is employed to analyze the dynamic performance of the closed-loop system. Based on the modeling result, a practical design equation for the PI compensator is derived. Experimental results are presented to verify the validity of the proposed PI compensator design.||2015|
|PED-5||A Current-Sourced LED Driver Compatible With Fluorescent Lamp Ballasts||A light-emitting diode (LED) driver compatible with fluorescent lamp (FL) ballasts is presented for a lamp-only replacement without rewiring the existing lamp fixture. Ballasts have a common function to regulate the lamp current, despite widely different circuit topologies. In this paper, magnetic and electronic ballasts are modeled as non ideal current sources and a current sourced boost converter, which is derived from the duality, is adopted for the power conversion from ballasts. A rectifier circuit with capacitor filaments is proposed to interface the converter with the four-wire output of the ballast. A digital controller emulates the high-voltage discharge of the FL and operates adaptively with various ballasts. A prototype 20- W LED driver for retrofitting T8 36-W FL is evaluated with both magnetic and electronic ballasts. In addition to wide compatibility, accurate regulation of the LED current within 0.6% error and high driver efficiency over 89.7% are obtained.||2015|
|PED-6||Filter Capacitor Minimization in a Flyback LED Driver Considering Input Current Harmonics and Light Flicker Characteristics||In this paper, a comprehensive study is conducted on reducing the size of output filter capacitor in an ac–dc fly back converter for driving high-brightness LED strings. To this end, a relationship between the input current harmonics, LED light flicker, and the magnitude of filter capacitor is obtained. It is shown that the size of the filter capacitor is mostly affected by the amplitude of the third and fifth harmonics of input current and the outputlight flicker. Considering the EN61000-3-2 standard for input current harmonics content and ENERGY STAR standard for flicker requirement, a procedure for obtaining the minimum value of filter capacitance is presented. Experimental studies are performed on an ac–dc fly back LED driver using the proposed method and tested on Cree X Lamp XP-G and CR22-32L LED strings.||2015|
|PED-7||A Novel Primary-Side Controlled Universal-Input AC–DC LED Driver Based on a Source-DrivingControl Scheme||A novel primary-side controlled universal-input ac–dc LED driver based on the source-driving control scheme is proposed in this paper, which employs low-voltage control MOSFETM2 to drive high-voltage power MOSFETM1 without an auxiliary winding commonly used in the conventional primary-side controlled scheme. The proposed control IC adopts minimum voltage detection circuit to monitor the zero crossing information of secondary winding current. The demagnetization time signal is generated by demagnetization time detection circuit. In addition, the ratio betweenthe secondary winding demagnetization time TDemag and switching period TS is maintained constant by adopting the intelligent charging and discharging circuit, finally achieving highprecision constant output current. A control IC for the proposed LED driver has been fabricated in TSMC 0.35 μm 5 V/600 V CMOS/LDMOS process. Experimental results of a 3-W circuit prototype show that the constant current precision is within ±1% in a wide range of universal-input ac voltage from 85 to 264 V, and that above 80% efficiency is obtained when driving three 1-W LEDs. The start-up time is only 46 ms under 90 Vac and 60 Hzinput, and the standby power is tested to be lower than 142 mW under 220 Vac and 50 Hz-input.||2015|
|PEST||A Novel Control Method for Transformer less H-Bridge Cascaded STATCOM With Star Configuration||This paper presents a transformer less static synchronous compensator (STATCOM) system based on multilevelH-bridge converter with star configuration. This proposed control methods devote themselves not only to the current loop control but also to the dc capacitor voltage control. With regards to the current loop control, a nonlinear controller based on the passivity-based control (PBC) theory is used in this cascaded structure STATCOM for the first time. As to the dc capacitor voltage control, overall voltage control is realized by adopting a proportional resonant controller. Clustered balancing control is obtained by using an active disturbances rejection controller. Individual balancing control is achieved by shifting the modulation wave vertically which can be easily implemented in a field-programmable gate array. Two actual H-bridge cascaded STATCOMs rated at 10 kV 2 MVA are constructed and a series of verification tests are executed. The experimental results prove that H-bridge cascaded STATCOM with the proposed control methods has excellent dynamic performance and strong robustness. The dc capacitor voltage can be maintained at the given value effectively.||2015|
|SNO||High-Power-Factor Rectifier Using the Modified SEPIC Converter Operating in DiscontinuousConduction Mode||The theoretical and experimental analysis of a modified version of the SEPIC dc–dc converter used as pre regulatorOperating in discontinuous conduction mode (DCM) is presented in this paper. The proposed converter presents a low input current ripple operating in DCM, and the switch voltage is lower than the output voltage. The switch voltage reduction increases the converter reliability and a low drain-to-source on-resistance (RDSon ) MOSFET can be used depending on the converter specification. Moreover, a digital control technique is applied to theproposed converter in order to reduce the third-harmonic input current distortion resultant of the operation in DCM. Finally, a
100-W prototype was developed operating with efficiency equal to 95.6%.
|PER-1||Infinity-Norm of Impedance-Based Stability Criterion for Three-Phase AC Distributed Power Systems With Constant Power Loads||This paper presents a stability criterion for three phase AC distributed power system (DPS). While the source outputimpedance and the load input admittance under synchronous reference frame are generally investigated to predict the stability of the three-phase AC DPS, the infinity-norms of the impedance and admittance are innovatively adopted in the proposed criterion to improve the computational complexity and the conservatism. Meanwhile, the computational complexity and the conservatism of the proposed criterion are analyzed and compared with existing ones. Furthermore, the terminal characteristics of the studied three-phase AC DPS composed of an LC filter and a three-phaseboost rectifier, which cover the source output impedance and the load input admittance, are comprehensively modeled. Finally, the effectiveness of the proposed criterion is validated by experimental results.||2015|
|PER-2||Improved Selective Harmonics Elimination Scheme With Online Harmonic Compensationfor High-Power PWM Converters||To reduce the low-order harmonics produced by the high-power pulse width-modulated (PWM) converters, selectiveHarmonic elimination (SHE) scheme is commonly used due to its superior harmonic performance at low switching frequency. However, as an off-line modulation technique, the SHE scheme itself lacks the capability to realize the active compensation of the grid background harmonics. To enable the active compensation ability of the SHE-modulated PWM converters, this paper proposes an active compensation method through the jittering of SHE phase angle. The proposed method can realize the real-time compensation of the preexisting system background harmonics in high-power PWM converters’ system. An application example on a high-power PWM current-source rectifier (CSR) system is provided in this paper. Experimental results show that the proposed method can effectively attenuate the line current harmonics caused by the grid background harmonics in the high-power PWM CSR systems.||2015|
|PER-3||Direct Power Control Based on Natural Switching Surface for Three-PhasePWM Rectifiers||In this letter, the natural trajectories of the output voltage and the inductor currents for three-phase pulse width modulation rectifiers are presented. On this basis, a novel direct power control (DPC) using the natural switching surface is proposed by combining DPC with the boundary control. Compared to the conventional DPC, the proposed control considers the output voltage when selecting the switching states. Therefore, the proposed control does not need an outer voltage control loop and can highly improve the dynamic performance of the dc output voltage. TheExperimental results on a 1.5-kW prototype confirm the correctness of the theoretical analysis. They verify the feasibility and the validity of the proposed control and show the excellent dynamic performance.||2015|
|PER-4||A Family of Soft-Switching DC–DC Converters Based on a Phase-Shift-Controlled Active Boost Rectifier||High efficiency and high power density can be achieved with a dc–dc transformer by operating all the switchesat a fixed 50% duty cycle. However, the output voltage of the dc–dc transformer cannot be regulated. Novel rectifiers named active boost rectifiers (ABRs) are proposed in this paper. Basically, an ABR is composed of a traditional diode rectifier and a bidirectional switch. By adopting phase-shift control between the primary- and secondary-side switches, the output voltage regulation can be achieved when introducing the ABR to a dc–dc transformer. As a result, a family of novel soft-switching dc–dc converters is harvested. When the proposed converter operates in the soft-switching continuous conduction mode, zero-voltage switching (ZVS) performance for all the primary- and secondary side switches is achieved. When the converter operates in the iscontinuous conduction mode, zero current switching (ZCS) for the primary-side switches and ZVS for the secondary-side switches are achieved. Furthermore, the diode reverse-recovery problem is alleviated by employing the ABR and phase-shift control scheme. As an example, the full-bridge converter with voltage-doublers ABR is analyzed to verify the proposed ABR concept and converters. The operation principles, voltage conversion ratio, and output characteristics are analyzed in depth. Finally, experimental results are provided to verify the feasibility and effectiveness.||2015|
|PER-1||Rotating Switching Surface Controlof Series-Resonant Converter Basedon a Piecewise Affine Model||In this paper, the control signal of the series-resonant converter is considered as a slope of a switching surface. The outputCharacteristic of the converter, for an ideal case and above the resonant frequency, is achieved based on the slope of the switching surface. This output haracteristic leads us to find the related slope for a specific converter gain. Nonlinear state equations of the series-resonant converter with new control input are represented inwidely used class of hybrid systems that have been called piecewise affine systems. Considering the effects of the slope variations in the switching surface, a simple and efficient control law is achieved. The main advantage of the proposed method is the absence of microcontroller and frequency modulator integrated circuits in hardware implementation. This property makes the proposed method more beneficial in high-frequency applications. Experimental results confirm our theoretical investigations.||2015|
|PER-2||Analysis and Design of LLC Resonant Converters With Capacitor–Diode Clamp Current Limiting||This paper presents a design methodology for LLC resonant converters with capacitor–diode clamp for current limiting in overload conditions. A new fundamental harmonicApproximation-based equivalent circuit model is obtained through the application of describing function techniques, by examining the fundamental behavior of the capacitor–diode clamp. An iterativeProcedure to determine the conduction point of the diode clamp is also given. The behavior of this type of converter is analyzed and guidelines for designing the current limiting characteristics are discussed. The characterization of a 90 W converter design using the proposed methodology is presented. The converter voltage gain and the voltage–current characteristics under different overload conditions and operating frequencies are predicted using the proposed model, which accuracies are validated against the prototype with good correlation.||2015|
|PER-3||A Bidirectional LLC Resonant Converter With Automatic Forward and Backward Mode Transition||This paper proposes an improved bidirectional LLC resonant topology with a new control scheme. All the switchesin the proposed topology can achieve soft switching. Compared with traditional isolated bidirectional dc–dc converters such as dual active bridge converter, the reverse energy and turn-off loss are reduced dramatically, and the conversion efficiency can be much improved. With the proposed new control scheme, the power flow direction and output power of the proposed converter can be changed automatically and continuously, which is attractive for energy storage systems to balance the energy and to keep the dc-busVoltage constant. Performance of the proposed circuit is validated by the experimental results from a 1-kW prototype. Over 97% efficiency is achieved at full load condition based on the prototype.||2015|
Z SOURCE INVERTER
|PEZ-1||Analysis of Critical Inductance and Capacitor Voltage Ripple for a Bidirectional Z-Source Inverter||An analysis of the critical inductance and capacitor voltage ripple of bidirectional Z-source was presented in this paper.Varying inductances were found to lead to different operational modes of the inverter. The critical inductance was derived. While the Z-source capacitor voltage ripple is traditionally consideredto be independent of the inductance with large inductance, it was found that dependence exists when small inductors are used. The capacitor voltage ripple was also derived. These theoretical findingshave been verified using both simulations and experimental results.||2015|
|PEZ-2||Impedance-Source Networks for Electric Power Conversion Part II: Review of Control and Modulation Techniques||Impedance-source networks cover the entire spectrum of electric power conversion applications (dc–dc, dc–ac,ac–dc, ac–ac) controlled and modulated by different modulation strategies to generate the desired dc or ac voltage and current at the output. A comprehensive review of various impedance-source network- based power converters has been covered in a previous paper and main topologies were discussed from an application point of view. Now Part II provides a comprehensive review of themost popular control and modulation strategies for impedance source
network-based over converters/inverters. These methods are compared in terms of theoretical complexity and performance,
when applied to the respective switching topologies. Further, this paper provides as a guide and quick reference for researchers and practicing engineers in deciding which control and modulation
method to consider for an application in a given topology at a certain power level, switching frequency and demanded dynamic response.
|PEMD1||PFC Cuk Converter-Fed BLDC Motor Drive||This paper deals with a power factor correction (PFC)-based Cuk converter-fed brushless dc motor (BLDC) driveas a cost-effective solution for low-power applications. The speed of the BLDC motor is controlled by varying the dc-bus voltage of a voltage source inverter (VSI) which uses a low frequency switching of VSI (electronic commutation of the BLDC motor) for low switching losses. A diode bridge rectifier followed by a Cuk converter working in a discontinuous conduction mode (DCM) is used for control of dc-link voltage with unity power factor at ac mains. Performance of the PFC Cuk converter is evaluated under four different operating conditions of discontinuous and continuous conduction modes (CCM) and a comparison is made to select a best suited mode of operation. The performance of the proposed system is simulated in a MATLAB/Simulink environment and a hardware prototype of the proposed drive is developed to validate its performance over a wide range of speed with unity power factor at ac mains.||2015|
|PEMD2||Investigation and Suppression of Harmonics Interaction in High-Power PWM Current-SourceMotor Drives||For high-power PWM current-source drive systems, the distortion of dc-link current cannot be ignored due to the low converter switching frequency and the relative small dc choke for reduced cost/weight. The distorted dc-link current may introduce inter harmonics in the grid side and the motor side through the rectifier and the inverter, and may give rise to the system resonance at certain motor speeds. When resonance occurs, significant inter harmonics are introduced in the drive system, which will degrade the grid-side power quality and produce the excessive torque ripples on the motor side. In this paper, the harmonics interaction in a high-power PWM current-source drive system is investigated, and a method for the system resonance estimation is proposed. Based on the estimation of resonance conditions, a dc-link virtual impedance-based control method is developed to mitigate the resonance resulted from the harmonics interaction. The investigation of harmonics interaction, the proposed resonance estimation method, and the dc-link virtual impedance-based suppression method are verified through both simulations and experiments.||2015|
|PEMD3||Predictive Torque Control Scheme for Three-Phase Four-Switch Inverter-Fed Induction Motor Drives With DC-Link Voltages Offset Suppression||The four-switch three-phase (B4) inverter, having a lower number of switches, was first presented for the possibility of reducing the inverter cost, and it became very attractive as it can be utilized in fault-tolerant control to solve the open/short-circuit fault of the six-switch three-phase (B6) inverter. However, the balance among the phase currents collapses due to the fluctuation of the two dc-link capacitor voltages; therefore, its application is limited. This paper proposes a predictive torque control (PTC) scheme for the B4 inverter-fed induction motor (IM) with the dc-link voltage offset suppression. The voltage vectors of the B4 inverter under the fluctuation of the two dc-link capacitor voltages are derived for precise prediction and control of the torque and stator flux. The three-phase currents are forced to stay balance by directly controlling the stator flux. The voltage offset of the two dc-link capacitors is modeled and controlled in the predictive point of view. A lot of simulation and experimental results are presented to validate the proposed control scheme.||2015|
|PEMD4||Deterioration Monitoring of DC-Link Capacitors in AC Machine Drivesby Current Injection||This letter proposes a novel condition monitoring scheme of dc-link capacitors in PWM inverter-fed induction machineDrives with front-end diode rectifiers, which is based on the online capacitance estimation scheme. While the motor is operating in the regenerative mode for the estimation process, a regulatedac component is injected into the stator winding, which causes a dclink
Voltage ripple at the same frequency. From the ac components of the dc-link voltage and current, the capacitance is estimated with a recursive least squares algorithm. With this method, experimental results have shown that the estimation error of the capacitance
is less than 1%, from which the deterioration condition of the capacitors
can be diagnosed reliably.
|PERS1||Three-Port DC–DC Converter for Stand-Alone Photovoltaic Systems||System efficiency and cost effectiveness are of critical importance for photovoltaic (PV) systems. This paper addresses the two issues by developing a novel three-port dc–dc converterfor stand-alone PV systems, based on an improved Flyback-Forward topology. It provides a compact single-unit solution with a combined feature of optimized maximum power point tracking(MPPT), high step-up ratio, galvanic isolation, and multiple operating modes for domestic and aerospace applications. A theoretical analysis is conducted to analyze the operating modes followed by simulation and experimental work. This paper is focused on a comprehensive modulation strategy utilizing both PWM and
phase-shifted control that satisfies the requirement of PV power systems to achieve MPPT and output voltage regulation. A 250-W converter was designed and prototyped to provide experimental verification in term of system integration and high conversion
|PERS2||An Interleaved High-Power Fly back Inverter for Photovoltaic Applications||This paper presents analysis, design, and implementation of an isolated grid-connected inverter for photovoltaic (PV)applications based on interleaved fly back converter topology operatingin discontinuous current mode. In today’s PV inverter technology, the simple and the low-cost advantage of the fly back topology is promoted only at very low power as micro inverter. Therefore, the primary objective of this study is to design the fly back converter
at high power and demonstrate its practicality with good performance as a central-type PV inverter. For this purpose, an inverter system rated at 2 kW is developed by interleaving of only
three flyback cells with added benefit of reduced size of passive filtering elements. A simulation model is developed in the piecewise linear electrical circuit simulator. Then, the design is verified and optimized for the best performance based on the simulation results. Finally, a prototype at rated power is built and evaluated
under the realistic conditions. The efficiency of the inverter, the total harmonic distortion of the grid current, and the power factor are measured as 90.16%, 4.42%, and 0.998, respectively. Consequently, it is demonstrated that the performance of the proposed
system is comparable to the commercial isolated PV inverters in the market, but it may have some cost advantage.
|PERS3||A Quasi-Uni polar SPWM Full-BridgeTransformer less PV Grid-Connected Inverter with Constant Common-Mode Voltage||The unipolar sinusoidal pulse width modulation (SPWM) full-bridge transformer less photovoltaic inverter with ac bypass brings low conduction loss and low leakage current. In orderto better eliminate the leakage current induced by the common modevoltage, the clamping technology can be adopted to hold the common-mode voltage on a constant value in the freewheeling period. A full-bridge inverter topology with constant common-mode voltage (FB-CCV) has been derived and proposed in this paper, two unidirectional freewheeling branches are added into the ac
side of the FB-CCV, and the split structure of the proposed freewheeling
branches does not lead itself to the reverse-recovery issues for the freewheeling power switches and as such super junction MOSFETs can be utilized without any efficiency penalty. The passive clamping branches consist of a capacitor divider and two diodes, is added into the dc side of the FB-CCV, therefore, the weakness of active damping branch has been overcome, and the better clamping performance has been achieved in the freewheeling
period. In the dead time between the main switches and the freewheeling switches, the ant parallel diodes of diagonal main switches of the FB-CCV form the freewheeling path to clamp the
common-mode voltage at a constant value, and a quasi-unipolar SPWM strategy is presented. The operation principle, differential mode, and common-mode characteristics of the FB-CCV, Heric, H6, and HB-ZVR topologies are analyzed and compared in detail.
Finally, the viability of the FB-CCV is verified by a universal prototype inverter rated at 5 kW.
|PERS4||A Novel High Step-up DC/DC Converter Based on Integrating Coupled Inductor and Switched-Capacitor Techniques for Renewable Energy Applications||In this paper, a novel high step-up dc/dc converter is presented for renewable energy applications. The suggested structure consists of a coupled inductor and two voltage multiplier cells,in order to obtain high step-up voltage gain. In addition, two capacitorsare charged during the switch-off period, using the energy stored in the coupled inductor which increases the voltage transfer gain. The energy stored in the leakage inductance is recycled
with the use of a passive clamp circuit. The voltage stress on the main power switch is also reduced in the proposed topology. Therefore, a main power switch with low resistance RDS(ON) can
be used to reduce the conduction losses. The operation principle and the steady-state analyses are discussed thoroughly. To verify the performance of the presented converter, a 300-W laboratory prototype circuit is implemented. The results validate the theoretical analyses and the practicability of the presented high step-up converter.
|PERS5||Interleaved Boost-Integrated LLC Resonant Converter With Fixed-Frequency PWM Control for Renewable Energy Generation Applications||This paper proposes a current-fed LLC resonant converter that is able to achieve high efficiency over a wide inputvoltage range. It is derived by ntegrating a two-phase interleaved boost circuit and a full-bridge LLC circuit together by virtue of sharing the same full-bridge switching unit. Compared with conventional full-bridge LLC converter, the gain characteristic is improvedin terms of both gain range and optimal operation area, fixed-frequency pulse width-modulated(PWM)control is employed to achieve output voltage regulation, and the input current ripple
is minimized as well. The voltage across the turned-off primary side
switch can be always clamped by the bus voltage, reducing the switch voltage stress. Besides, its other distinct features, such as single-stage configuration, and soft switching for all switches also contribute to high power conversion efficiency. The operation principles are presented, and then the main characteristics regarding gain, input current ripple, and zero-voltage switching (ZVS) considering the nonlinear output capacitance of MOSFET are investigated and compared with conventional solutions. Also, the design procedure for some key parameters is presented, and two kinds of interleaved boost integrated resonant converter topologies are generalized. Finally, experimental results of a converter prototype with 120–240 V input and 24 V/25 A output verify all considerations.
|PERS6||A Step-up Resonant Converter for Grid-Connected Renewable Energy Sources||With the rapid development of large-scale renewable energy sources and HVDC grid, it is a promising option to connect the renewable energy sources to the HVDC grid with a pure dc system,in which high-power high-voltage step-up dc–dc converters are the key equipment to transmit the electrical energy. This paper proposes a resonant converter which is suitable for grid-connected renewable energy sources. The converter can achieve high voltagegain using an LC parallel resonant tank. It is characterized by zero-voltage-switching (ZVS) turn-on and nearly ZVS turn-off of main switches as well as zero-current-switching turn-off of rectifier diodes; moreover, the equivalent voltage stress of the semiconductor devices is lower than other resonant step-up converters. The
operation principle of the converter and its resonant parameter selection is presented in this paper. The operation principle of the proposed converter has been successfully verified by simulation
and experimental results.
|PERS7||Frequency-Coordinating Virtual Impedance for Autonomous Power Management of DC Micro grid||In this paper, the concept of frequency-coordinating virtual impedance is proposed for the autonomous control of a dc micro grid. This concept introduces another degree of freedom in the conventional droop control scheme, to enable both time-scale and power-scale coordination in a distributed micro grid system. As an example, the proposed technique is applied to the coordinatingregulation of a hybrid energy storage system composed of batteries and super capacitors. With an effective frequency-domain shaping of the virtual output impedances, the battery and super capacitor converters are designed to absorb low-frequency andhigh-frequency power fluctuations, respectively. In this way, their
complementary advantages in energy and power density can be effectively
exploited. Furthermore, the proposed concept can be integrated into a mode-adaptive power management framework with autonomous mode transitions. The entire solution features highly versatile functions based on fully decentralized control. Therefore,
both flexibility and reliability can be enhanced. The effectiveness of the presented solution is verified by experimental results.
|PERS8||A Photovoltaic Array Transformer-Less Inverter With Film Capacitors and SiliconCarbide Transistors||A new photovoltaic (PV) array power converter circuit is presented. This inverter is a transformer-less topology with grounded PV array and only film capacitors. The motivations are to reduce circuit complexity, eliminate leakage ground currents, and improve reliability. The use of silicon carbide (SiC) transistors is the key enabling technology for this particular circuit to attain reasonable (>97%) efficiency. Some background about the challengesof ground currents and power decoupling to be addressed is first discussed. The proposed solution of a bidirectional buck boost converter, dynamically varying dc link, and half-bridge inverters is then presented along with details on the basic functionality. Some aspects of selecting passive components for the circuit are discussed. The average dynamic model and control system are then presented. Finally, simulation and experiment results are shown demonstrating that the proposed topology is a viable solution.||2015|
WIRELESS POWER TRANSFER
|PEWL1||A Fast Method for Generating Time-Varying Magnetic Field Patterns of Mid-Range Wireless Power Transfer Systems||Visualizing the magnetic flux paths for wireless power transfer systems enables researchers and engineers to understand the operations and design the geometrical dimensions of the practical systems. However, time-domain transient simulations of 3-D electromagnetic fields of complex wireless power transfer systemswith multiple coil-resonators are extremely time-consuming. Thispaper describes a fast hybrid approach that combines the time domain
coupled circuit modeling and the magneto static analysis to form a fast time-domain analytical tool for studying complex wireless power transfer systems. The proposed methodology has been successfully applied to several wireless domino-resonator systems.
For the first time, the time-varying magnetic flux variations of wireless power domino-resonator systems can be visualized in computer simulations.
|PEWL2||Analysis and Tracking of Optimal Load in Wireless Power Transfer Systems||All the wireless power transfer (WPT) systems share a similar configuration including a power source, a coupling system, a rectifying circuit, a power regulating, and charging managementCircuit and a load. For such a system, both a circuit- and system-level analyses are important to derive requirements for high overall system efficiency. Besides, unavoidable uncertainties in a real WPT system require a feedback mechanism to improve the robustness of the performance. Based on the above basic considerations, this paper first provides a detailed analysis on the efficiency of a WPT system at both circuit and system levels. Under a specific mutual inductance between the emitting and receiving coils, an optimal load resistance is shown to exist for a maximum overall system efficiency. Then, a perturbation-and-observation based tracking system is developed through additional hardwaresuch as a cascaded boost-buck dc–dc converter, an efficiency sensing
System and a controller. Finally, a 13.56-MHz WPT system is demonstrated experimentally to validate the efficiency analysis and the tracking of the optimal load resistances. At a power level
of 40 W, the overall efficiency from the power source to the final load is maintained about 70% under various load resistances and relative positions of coils.
|PEWL3||A Methodology for Making a Three-Coil Wireless Power Transfer System More Energy Efficient Than a Two-Coil Counterpart for Extended Transfer Distance||A new methodology for ensuring that a three-coil wireless power transfer system is more energy efficient than a two coil counterpart is presented in this paper. The theoretical proof and the conditions for meeting the objective are derived and practically verified in a practical prototype. The key features of the magnetic design are to: 1) shift the current stress from the primary driving circuit to the relay resonator; and 2) generate a large relay current for maximizing magnetic coupling with the receiver coil for efficient power transfer. Consequently, the current rating andcost of the driving circuit can be reduced and the overall quality factor and system energy efficiency are improved. This approach utilizes the combined advantages of the maximum efficiency principle and the use of relay resonator to overcome the energy efficiencyProblem for applications with extended energy transfer distances.||2015|
POWER FACTOR CORRECTION
|PEPF1||Optimal Lowest-Voltage-Switching for Boundary Mode Power Factor Correction Converters||This paper presents an optimal lowest-voltage switching technique for boundary mode power factor correction (PFC) converters. The proposed approach minimizes the switching loss of the power MOSFET without additional discrete components. Optimal zero-voltage-switching or valley-switching canbe achieved for universal input range. The gate driver delay canalso be taken into account. A boundary mode boost PFC converter with the proposed optimal switching technique has been implemented using a 0.5-μm N-well process. Experimental results show
that the proposed approach can realize optimal soft switching, and improve the efficiency of the boost PFC converter. The proposed lowest-voltage-switching technique can be applied to other resonant converters as well.
|PEPF2||A Three-Level Quasi-Two-Stage Single-Phase PFC Converter with Flexible Output Voltage and Improved Conversion Efficiency||This paper presents a three-level quasi-two-stage single-phase power factor correction (PFC) converter that hasFlexible output voltage and improved conversion efficiency. The proposed PFC converter features sinusoidal input current, three level output characteristic, and a wide range of output dc voltages,and it will be very suitable for high-power applications where the output voltage can be either lower or higher than the peak ac input voltage, e.g., plug-in hybrid electric vehicle charging systems. Moreover, the involved dc/dc buck conversion stage may only need
to process partial input power rather than full scale of the input power, and therefore the system overall efficiency can be much improved. Through proper control of the buck converter, it is also
Possible to mitigate the double-line frequency ripple power that is inherent in a single-phase ac/dc system and the resulting load end voltage will be fairly constant. The dynamic response of this
regulation loop is also very fast and the system is therefore insensitive
to external disturbances. Both simulation and experimental results are presented to show the effectiveness of this converter as well as its efficiency improvement against a conventional two-stage solution.
|PEPF3||A Stepping On-Time Adjustment Methodfor Interleaved Multichannel PFC Converters||A simple and effective stepping on-time adjustment (SOTA) method with status judgment for interleaved multichannelCritical mode (CRM) boost-type power factor correction (PFC) converters is proposed. The boost-type PFC converter with CRM operation is commonly used for ac–dc conversion because of itsCircuit simplicity and high efficiency. The interleaved multichannel PFC converter becomes the trend for high-power applications. However, conventional interleaved methods are complicated and
Difficult to implement when more than two channels are required. Also, noise disturbances or on-time mismatching can easily lead to continuous conduction mode operation which will increase current distortion, reduce power conversion efficiency, or even damage the converter. The proposed SOTA method with status judgment can
Greatly simplify the control complexity of the interleaved multichannel operation. A prototype 600-W three-channel interleaved CRM boost PFC converter is built to verify the performance of the proposed SOTA method.
|PEPF4||Three-Level Single-Phase Bridgeless PFC Rectifiers||This paper presents new three-level unidirectional single-phase PFC rectifier topologies well suited for applicationsTargeting high efficiency and/or high power density. The characteristicsOf a selected novel rectifier topology including its principles of operation, modulation strategy, feedback control scheme, and a power circuit design related analysis are presented. Finally, a
220-V/3-kW laboratory prototype is constructed and used in order to verify the characteristics of the new converter, which include remarkably low switching losses and single ac-side boost inductor that allow for 98.6% peak efficiency with a switching frequency of 140 kHz.
|PEPF5||A Fully Integrated Three-Level IsolatedSingle-Stage PFC Converter||For low-cost isolated ac/dc power converters adopting high-voltage dc-link, research efforts focus on single-stage multilevel topologies. This paper ro poses a new single-stage three-level isolated ac/dc PFC converter for high dc-link voltage low-power applications,achieved through an effective integration of ac/dc and dc/dc stages, where all of the switches are shared between two operations. With the proposed converter and switching scheme, input current shaping and output voltage regulation can be achieved simultaneously without introducing additional switches or switching actions. In addition, the middle two switches are turned on underzero current in discontinuous conduction mode operation, and the upper and bottom switches are turned on under zero voltage. Due to the flexible dc-link voltage structure, high power factor can be achieved at high line voltage.A500 W/48Vprototype is designed to
serve as the proof of concept, which exhibits 90.8% peak efficiency
at low input line voltage.
|PEPF6||A Digitally Controlled Critical Mode Boost Power Factor Corrector With Optimized Additional On Time and Reduced Circulating Losses||In many low-to-mid power applications, critical mode boost power factor corrector converters are widely used because of its low switching loss and simple control. However, near the zeroCrossing of the input line voltage, an input current distortion and a low power factor are caused by delayed switching period and negative input currents. Generally, an additional on-time methodAccording to the input voltage is used to compensate the input current distortion. However, a detailed quantitative analysis for the exact additional on time has not been studied till now. In this paper, the explicit form of the optimized additional on time has been obtained using a quantitative analysis and the advantage of the digital control. From a state trajectory and “net input charge”
Analysis, it is shown that the optimized on time should be related to not only the input voltage, but also the output power. Also, in order to improve the efficiency in a high input and light load condition, circulating currents are reduced in the inevitable dead angle with a gate turning-off technique. By using digital control, the
Optimized additional on time and the gate turn-off technique have been implemented with the 90–230 Vrms input and 380 V/200 W output prototype.
|PEPF7||Bridgeless PFC-Modified SEPIC Rectifier With Extended Gain for Universal InputVoltage Applications||In this paper, a new single-phase ac–dc PFC bridgeless rectifier with multiplier stage to improve the efficiency at lowInput voltage and reduce the switch-voltage stress is introduced. The absence of an input rectifier bridge in the proposed rectifier and the presence of only two semiconductor switches in the current flowing path during each switching cycle result in less conductionlosses and improved thermal management compared to the conventional full bridge topology. Lower switch voltage stress allows utilizing a MOSFET with lower RDS-on. The proposed topology is designed to operate in discontinuous conduction mode (DCM) to achieve almost a unity power factor and low total harmonic distortion (THD) of the input current. The DCM operation gives additional advantages such as zero-current turn-on in the power switches and simple control circuitry. The proposed topology is compared with modified full-bridge SEPIC rectifier in terms of efficiency, THD, and power factor. Detailed converter analysis, small
Signal model, and closed-loop analysis are presented. Experimental
Results for a 200 W/400 Vdc at universal line voltage range to evaluate the performance of the proposed bridgeless PFC rectifiers are detailed.
|PEPF8||Time-Varying Compensation for PeakCurrent-Controlled PFC Boost Converter||In this paper, an optimal time-varying compensation method with zero eigenvalue is first put forward for peak current controlled power factor correction (PFC) boost converter, which can eliminate the fast-scale instability without zero current dead zone and achieve unity power factor. First, a time-varying mathematic model of a peak current-controlled PFC boost converterunder continuous conduction mode is established. Then, based on the theoretical and experimental analyses of the traditional ramp compensation, a time-varying dynamic compensation model and method are presented to obtain zero eigenvalue during thewhole life cycle. Therefore, the PFC boost converter occupies the strongest stability control during each switching cycle and can run into stable operation in one switching cycle under any external interference. Finally, the proposed compensation method is verified
with experiments. Results show that a unity power factor and the stability in the whole line cycle can be obtained simultaneously.
MULTILEVEL INVERTER & CONVERTER
|PEML1||Optimal Low Switching Frequency Pulse width Modulation of Nine-Level Cascade Inverter||Synchronous optimal pulse width modulation (SOP) permits low switching frequency modulation of multilevel inverter for medium-voltage high-power industrial ac drives without compromising on total harmonic distortion (THD). An aim of our experiment was to operate a nine-level cascade inverter of an induction motor drive at an average device switching frequency limited to rated fundamental frequency by using SOP technique. To reduce the number of separate dc sources, a three-level diode clamped converter was used as a cell in the nine-level cascade inverter. Using SOP technique, optimal nine-level waveforms were obtained by offline optimization assuming steady-state operation of the induction machine. The switching angles for each semiconductor switch are then obtained from optimal nine-level waveforms based on the criteria to minimize the switching frequency as well as unbalance in dc-link capacitor voltages. experimental results obtainedfrom the 1.5-kW induction motor drive show THD < 5% for stator currents. The results indicate that SOP technique reduces the switching frequency of operation without compromising on THD.||2015|
|PEML2||Modular Multilevel Converter With an Adaptive Observer of Capacitor Voltages||A modular multilevel converter (MMC) is an attractive solution for power conversion without informers. The MMC consists of cascade connections of floating dc capacitors. In this paper,an adaptive observer design has been proposed to estimate the capacitor voltages from the measurement of arm currents. This work introduces the capacitance value of the cell capacitors as a parameter uncertainty for making the system performance robust with unknown constant parameters. It may be used for predictive control, condition monitoring for capacitors, and diagnosis check for capacitor health. In addition, a pulse width modulation (PWM) technique for MMChas been explored. The PWM technique is performedUsing a carrier-based level-shifted PWM strategy. It does not necessitate the calculation of duty cycles, and can be easily implemented in a DSP. By using the PWM technique, harmonics in the phase voltage is shifted to twice the switching frequency. Theoretical analysis is included in this paper for showing stability and convergence of the proposed observer. Analytical expressions are verified by simulation and experimental results.|
|PEML3||Hybrid Multicarrier Modulation to Reduce Leakage Current in a Transformer less Cascaded Multilevel Inverter for Photovoltaic Systems||This letter proposes a hybrid multicarrier pulse width modulation (H-MCPWM) technique to reduce leakage current in aTransformer less cascaded multilevel inverter for photovoltaic (PV) systems. The transformer less PV inverter topology has the advantages of simple structure, low weight and provides higher efficiency. However, the topology makes a path for leakage current to flow through parasitic capacitance formed between the PV module and the ground. A modulation technique has significant impact to reduce the leakage current without adding any extra component. The propose DH- MCPWM technique ensures low leakage current in the transformer less PV inverter system with simplicity in implementation of the modulation technique using lesser number of carriers. Experimental prototype developed in the laboratory demonstrates the performance of the proposed modulation technique in reducing the leakage current.||2015|