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This article investigates upon partial resonance in current-fed converter using series LC resonant circuit to attain zero-current-switching (ZCS) of the semiconductor devices. A resonance pulse appears during overlap conduction time of the semiconductor devices causing natural current reduction in an outgoing device to zero before the gating signal is forced-off achieving ZCS commutation of the devices. Soft device turn-off eliminates the turn-off switching losses and more importantly, avoids the traditional requirement of additional snubber to clamp the voltage across the semiconductor devices in current-fed converters. Partial resonance reduces the circulating current and so rms current through the devices limiting the conduction losses. The proposed idea is analyzed and implemented on current-fed half-bridge isolated voltage doubler topology. It has been experimentally demonstrated to achieve wide range ZCS operation along with high efficiency. [ABSTRACT FROM AUTHOR]

A current-fed full-bridge converter availing series resonance pulse to enable zero-current switching (ZCS) and voltage clamping of the semiconductor devices is proposed. Overlap in switching states of the devices enforces a short resonance pulse, due to series tank which naturally reduces the current to zero in the outgoing semiconductor devices. It causes zero-current commutation of the devices eliminating voltage spike across the semiconductor devices. Essentially, pulse-resonance offers reduced circulating current resulting in lower conduction losses and not demanding over-rated components. The proposed converter enables ZCS for wide variation in source voltage by implementing variable frequency fixed duty modulation eliminating the traditional requirement for additional clamping circuitry in conventional current-fed converters. Detailed experimental results on proof-of-concept hardware prototype rated at 500 W are demonstrated to verify the proposed claims and converter performance. With all other merits, proposed converter maintains high efficiency. [ABSTRACT FROM AUTHOR]

Due to its voltage-fed nature and a capacitive output filter, the rear-end rectifier of parallel and series–parallel resonant converters with capacitive filters draw discontinuous currents. Not only simple and elegant techniques such as fundamental harmonic approximation (FHA) analysis, but also time-domain, state-space, and state-plane approaches fail to model such converters with reduced labor. This letter presents a technique to restore the simplicity of FHA analysis about such converters. Authenticity and accuracy of the proposed technique is demonstrated through PSIM 11.0 simulation platform. Furthermore, a detailed comparison with the existing modeling techniques is also provided. [ABSTRACT FROM AUTHOR]

The aim of this article is to develop a real-time computational method that determines switching angles of selective harmonic elimination (SHE) for operating nine-level (9 L) current-fed multilevel converter (MLC). The computation algorithm for SHE conventionally requires huge calculation time to identify switching angles of the inverter, and hence, a truth table based modulation is applied for operating the converter in real time. To overcome this, a new analytical method has been proposed in this article that minimizes the computation time to calculate the switching angles. However, these switching angles cannot be directly applied to current-fed MLCs. Unlike voltage fed converters, the current-fed converters have additional operational constraints on the modulation technique. Hence, in this article, a conversion technique has been utilized to convert the unconstraint SHE angles into constraint angles in order to operate current-fed MLCs. A low-power prototype of 9 L current source inverter has been set-up to experiment and validate the proposed real-time calculation method at the fundamental frequency of 50 Hz. [ABSTRACT FROM AUTHOR]

This article analyzes a three-phase single-stage isolated flyback-based power factor correction converter and presents a novel clamping circuit to capture the transformers leakage inductance energy. The converter unity power factor operation is obtained by using the inherent resistance property of discontinuous conduction mode. Thus, the input current shaping circuit is eliminated and resulted in a single-loop control system. Therefore, the converter control circuit requires only one sensor, which decreases the system cost, and also increases the system robustness to high-frequency noise. With the proposed clamping circuit, the transformers leakage inductance energy is successfully captured in clamping capacitor, and thereby, it is fed to the dc load by using an auxiliary two-switch forward converter which enhanced the overall operating efficiency of a converter. The converter detailed steady-state operation and the design considerations are presented. Each power component voltage stress expressions are derived to simplify the converter design, and the converter small-signal model is presented to help the controller design. The novelty and performance of the converter is verified by both simulation and experimentation. [ABSTRACT FROM AUTHOR]

A three-phase-isolated current-fed dc–dc converter with LCC-T resonant tank to achieve an efficient and compact design is proposed. Traditional dc–dc converters require an external parallel inductor to increase the transformer magnetizing current to realize soft switching under light-load conditions. The proposed LCC-T configuration eliminates this requirement and realizes light-load soft switching with reduced circulating current. In addition, the proposed topology maintains zero-voltage switching (ZVS) turn-ON of primary switches, ZVS turn-ON and zero-voltage-zero-current switching turn-OFF of secondary diodes for all load conditions. Steady-state operation, analysis, and design of the proposed converter are reported. Experimental results of 1-kW hardware prototype to verify the claims of the proposed analysis and design are presented. [ABSTRACT FROM AUTHOR]

This paper proposes an “isolated soft switching current fed LCC-T resonant dc–dc converter for PV/fuel cell applications.” This converter is able to achieve zero voltage switching for front-end inverter switches and zero-current switching for voltage doubler diodes. The majority of dc–dc converters have compact capacitive (C) filter in output, but high harmonic currents through transformer makes them bulky. The proposed converter attempts to improve harmonic content through a transformer under wide load and input variations as well as it can significantly reduce required turns ratio of transformer to achieve required output voltage. For the above reasons, the proposed converter can offer better footprints and therefore it can be a potential candidate for PV/fuel cell applications. This paper presents basic operating principal, detailed analysis, control, and design of the proposed converter with the help of an example. This converter operates in two modes, i.e., constant duty cycle mode and constant frequency mode, depending on load demand, and is explained through operating curves. Finally, experimental results are included for justifying the proposed theory. [ABSTRACT FROM AUTHOR]

Resonant converters with capacitive output filters are quite popular for their higher voltage gain and compact designs. But the majority of the converters underutilize the transformer as they are subjected to discontinuous currents. This discontinuous current possesses huge current ripples that produce huge core losses and aggravate the temperature rise of the transformer. This often leads to saturation of the transformer. This paper presents an LCC-T resonant dc–dc converter with a capacitive output filter operating all switches in the zero current switching (ZCS) switching mode and whose transformer current is a continuous sinusoidal with minimum stress on resonant tank components. This is achieved by bringing the transformer in series to a resonant inductor. The proposed converter is simulated in power simulation (PSIM) 11.0.1. A proof-of-concept model rated 288 W is designed and developed, and hardware results are presented as verification to theory. [ABSTRACT FROM AUTHOR]

In this paper, analysis and design of a three-phase-isolated Cuk-based power factor correction (PFC) converter have been proposed. The proposed converter is operated in discontinuous output inductor current mode to achieve PFC at ac input. This avoids the inner current control loop which further eliminates the sensing of current. This makes the system more reliable and robust. The converter requires only one simple voltage control loop for output voltage regulation, and all the power switches are driven by the same gate signal which simplifies the gate driver circuit. The detailed operation of the converter and design calculations are presented. And also a small-signal model of the converter by using current injected equivalent circuit approach is presented to aid the controller design. The experimental results from a 2-kW laboratory prototype with 208-V line-to-line input voltage, 400-V output voltage are presented to confirm the operation of the proposed converter. An input power factor of 0.999, an input current total harmonic distortion of as low as 4.06%, and a high conversion efficiency of 95.1% are achieved from laboratory prototype. [ABSTRACT FROM AUTHOR]

Usually, the parallel-compensated inductive power transfer (IPT) topology fed by a current-source inverter is controlled through variable switching frequency and fixed 50% duty cycle method. This enables the system to operate at resonance frequency, which drifts due to load and other parameter variations. Owing to this control constraint, the load requirements are fulfilled by adding extra dc–dc chopper at the output. This paper presents a new control technique for a parallel–series/series IPT network, fed from a full-bridge current-source inverter to meet the load demand directly by an inverter. Therefore, the extra chopper stage at the output side of the converter is eliminated. The control goals are achieved through a two-loop control method, where the inner input current loop controls the source current and the outer output current loop meets the load requirements. The detailed steady-state operation, converter design, small-signal modeling, and control are reported, and experimental results obtained from a 1.6-kW lab prototype are included to verify the mathematical analysis. [ABSTRACT FROM AUTHOR]

The zero-phase-angle (ZPA) operation at inverter output of parallel-compensated inductive power transfer (IPT) topologies is frequently reported to be load dependent. Therefore, either the operating inverter switching frequency or the compensation capacitors are modified dynamically with load variation to reach new ZPA point. This letter proposes a novel design technique of compensation capacitors for several IPT topologies to obtain load-independent ZPA. The proposed method is based on the passive selection of tank network parameters; therefore, it obviates the requirement of dynamic tuning and complexities associated with it. A detailed mathematical analysis is reported, and experimental results obtained from a 1-kW lab-prototype are demonstrated to verify the analysis and performance. [ABSTRACT FROM AUTHOR]

Generally, in wireless inductive power transfer (IPT) system, the power is processed through multiple power transfer stages and this leads to lower efficiency and higher cost of the system. Recent research shows that the use of a direct ac–ac converter in an IPT system compensates these limitations significantly. However, one of the major challenges of the IPT circuit with direct ac–ac converter is to achieve multiple control goals through a single converter. These include load power requirement, maintaining high-quality source current and achieving soft switching of inverter switches, etc. In the existing literatures, the research is more focused on meeting load power requirement and soft switching of inverter switches. The major focus of this paper is to propose, analyze, and control a new IPT power converter topology using current-fed direct ac–ac converter. Compare with existing buck derived, i.e., voltage source ac–ac converter topologies, the proposed topology is boost derived; therefore, active source current waveshaping is easily obtained. The complete control is carried out through two loops, where the outer output current loop ensures load requirements and inner loop maintains the high-quality grid current. The detail of steady-state and dynamic analysis and design procedure of the converter is presented. Experimental results obtained from a 1.2-kW lab-build prototype are included to verify the analysis and proposed control. [ABSTRACT FROM PUBLISHER]

This paper studies and analyzes the effect of reconfiguration and network type (mesh/radial) on the small-signal stability margin of a droop-based islanded microgrid. Eigenvalue analysis is performed on three systems: a low-voltage microgrid, the standard IEEE 33-bus islanded system with three and five sources, and the standard IEEE 69-bus islanded system with three sources. From eigenvalue analysis, it is observed that the reconfiguration and network type have notable impact on the small-signal stability margin. The analysis and analytical results are initially verified and confirmed through time-domain simulations using MATLAB/SIMULINK for the system considered. Experimental results are demonstrated on the developed microgrid prototype to support the claims and validate the proposed analysis and results. [ABSTRACT FROM PUBLISHER]

This paper proposes a current-fed single-phase inverter without constant intermediate DC link. It eliminates electrolytic capacitor from the DC-link and introduces an intermediate pulsating DC bus. The proposed topology is modular with three full-bridges making it scalable for high-power applications. New pulsating-DC-modulation for back-end pulsating DC-link inverter and secondary modulation (SM) for front-end DC-to-pulsating DC converter is proposed. Soft-switching and device voltage clamping of both primary side and secondary side devices of front-end current-fed full-bridge converter is realized. A rotating partial hybrid pulsewidth modulation has been introduced. One leg of inverter is commutated at a low switching frequency, while the other leg is operated at a high switching frequency for partial period of a line frequency cycle. Thus, switching losses of the back-end inverter are considerably reduced. Rotating mechanism is used to equalize the switching losses of four switches of the inverter. This paper presents detailed operation and analysis of the topology with a proposed modulation scheme. Simulation and experimental results validate the effectiveness and accuracy of the proposed modulation scheme as well as soft-switching and performance of the converter. [ABSTRACT FROM PUBLISHER]

Current-fed converters offer enormous potential as power conditioning units for fuel cell applications, owing to precise fuel cell stack current control, short-circuit protection, voltage gain, and stiff fuel cell dc current. Aspects such as low current ripple and smaller input current slope ensure energy efficient operation and better fuel utilization, and enhance the lifetime of the fuel cell stack. However, the demerits of turn-off voltage spike across semiconductor devices limits the operating frequency. This paper proposes, analyzes, and implements a simple and cost-effective impulse commutated modular three-phase circuit to eliminate and solve the associated turn-off spike problem. Impulse commutation permits soft turn-off of devices and clamps the device voltage. The converter efficiently handles the variations in the fuel cell stack voltage and current with variable frequency modulation. Detailed steady-state operation, analysis, and performance of the proposed modular converter with impulse commutation are reported. The proposed impulse commutated three-phase circuit is a potential candidate for high-current applications. The validation of the converter operation on a 1-kW proof-of-concept hardware prototype is performed to substantiate the claims. [ABSTRACT FROM AUTHOR]

This paper contributes to the analysis and development of a new power electronics system for bidirectional wireless power transfer (WPT). The major focus is the analysis and implementation of a new current-fed resonant topology with current-sharing and voltage-doubling features. A new bidirectional WPT system with current-fed half-bridge voltage-doubler circuit is proposed and analyzed with series–parallel and series resonant networks. Traditionally used parallel L–C resonant tank in transmitter circuit with current-fed WPT topology causes higher voltage stress across the inverter devices to compensate the reactive power consumed by the loosely coupled coil. In the proposed topology, this is mitigated by adding a suitably designed capacitor in series with the transmitter coil; thus, developing a series–parallel CLC tank. Detailed analysis and design is reported for both grid-to-vehicle and vehicle-to-grid operations. The power flow is controlled through variable frequency modulation. Soft switching of the devices is obtained irrespective of the load current. A proof-of-concept experimental hardware prototype rated at 1.2 kW is developed and tested. Experimental results are presented to verify the analysis and demonstrate the performance of the system with bidirectional power flow. [ABSTRACT FROM AUTHOR]

This paper proposes and analyzes a new power electronics circuit topology for wireless inductive power transfer application using current-fed half-bridge converter with CCL-LC resonant network. The major focus is analysis and implementation of a new current-fed resonant topology with current-sharing and voltage doubling features. Generally, inductive power transfer circuits with current fed converter use parallel CL resonant tank to transfer power effectively through air gap. However, in medium power application, this topology suffers from a major limitation of high voltage stress across the inverter semiconductor devices owing to high reactive power consumed by loosely coupled coil. In proposed topology, this is mitigated by adding a capacitor in series with the coil developing series-parallel CCL tank. The power flow is controlled through variable frequency modulation. Soft-switching of the devices is obtained irrespective of the load current. For grid-to-vehicle or solar-to-vehicle, the converter is analyzed and detailed design procedure is illustrated. Experimental results are presented to verify the analysis and demonstrate the performance. [ABSTRACT FROM AUTHOR]

Multilevel converters (MLCs) have emerged as standard power electronic converters in high power as well as quality demanding applications. They are classified into current-fed MLCs and voltage-fed MLCs. Voltage-fed MLCs have widely researched whereas the current-fed MLCs are the recent topic of research. Based on the principle of duality between voltage and current sources, several current-fed MLCs analogous to voltage-fed MLCs have been identified. Current-fed MLCs offer several advantages in terms of high power capability, transformerless operation, short-circuit protection, and excellent quality of output current waveform. The goal of this paper is: 1) to present review of circuit topologies, modulation schemes, and applications of current-fed MLCs; and 2) to review an emerging low-device switching frequency modulation technique known as synchronous optimal pulsewidth modulation for current-fed MLCs. The circuit configuration and advantages of each topology along with various modulation techniques are discussed in detail. Compared to voltage-fed MLCs, the operation of current-fed MLCs need to satisfy additional switching constraints. A survey of classical methods for realization of these operational constraints has been done and a new generalized method has been proposed. Finally, future scope of research has been presented to encourage further development of topologies and modulation techniques for current-fed MLCs. [ABSTRACT FROM AUTHOR]

Impulse commutation obtains zero current commutation of devices in a circuit with a short resonance impulse using a simple resonant tank. This concept has been studied, extended, and implemented for a three-phase push–pull current-fed single-inductor topology to achieve soft commutation and device voltage clamping solving the traditional issue of device turn-off voltage overshoot. The push–pull topology is attractive owing to single inductor, all common source devices connected to common supply ground, and reduced gate driving requirements. Detailed operation, analysis, and design of this topology have been reported with impulse commutation. With a small resonant tank and partial resonance, impulse commutation procures merits of voltage clamping, low circulating current, and load adaptive zero-current switching of the devices. Variable-frequency modulation regulates load voltage and maintains the impulse commutation with source voltage variation. Experimental results on a 1-kW proof-of-concept hardware prototype are demonstrated to observe the operation, performance, and verify the proposed concept and claims. [ABSTRACT FROM PUBLISHER]

Multilevel converter topologies for open-end stator winding medium-voltage (MV) induction motor drives have been researched from the last two decades. In this paper, a dual $n$ -level modular multilevel converter (MMC) topology has been proposed for open-end stator winding MV induction motor drives. The control requirements of the proposed system are low device switching frequency, minimal harmonic distortion of machine stator currents, elimination of common-mode voltages in machine stator windings, and maintaining floating capacitor voltages around their nominal value. Based on these requirements, an emerging modulation technique for MV induction motor drives known as synchronous optimal pulsewidth modulation has been developed for the proposed dual $n$L-MMC topology. The laboratory measurements from a dual three-level MMC fed 1.5-kW open-end stator winding induction motor drive demonstrate the performance of proposed technique. [ABSTRACT FROM PUBLISHER]

Modular multilevel converter (MMC) is now the state-of-the-art converter topology for high-voltage dc transmission (HVDC) systems. Another potential application for MMC is medium-voltage (MV) high-power industrial ac drives. In high-power applications, thermal constraints of power semiconductor devices limit device switching frequency to a few hundred hertz. However, there exists a tradeoff between device switching frequency and harmonic distortion of converter output currents. Synchronous optimal pulsewidth (SOP) modulation is an emerging low-device switching-frequency-modulation technique for high-power converters, which maintains the quality of converter output currents. SOP technique has been successfully demonstrated for classical multilevel topologies and it has been proved that maximum-device switching frequency can be limited to rated fundamental frequency for seven or higher level inverters without compromising on the quality of output currents. However, implementation of SOP technique for MMC topology is still pending. One of the main challenges for control of MMC is to maintain floating-capacitor voltages around their nominal value. The goal of our study is to propose, analyze, and implement enhanced SOP technique for MMCs to achieve low-device switching-frequency operation, better quality of converter output currents, and maintain capacitor voltages around their nominal value. The proposed technique has been validated using low-power prototype of five-level MMC feeding an 1.5-kW induction motor. [ABSTRACT FROM PUBLISHER]

This paper proposes a current-fed non-isolated soft-switching bidirectional dc/dc converter for interfacing energy storage to dc microgrid. The proposed converter employs a current-fed half-bridge boost converter at front-end followed by an LCL resonant circuit to aid in soft-switching of semiconductor devices. A voltage doubler at output is selected to enhance the gain by $2 \times $. The LCL resonant circuit also adds a suitable voltage gain. Therefore, the topology offers overall high voltage gain without transformer or large number of multiplier circuits. For buck operation, high side voltage is first divided by half with capacitor divider to gain higher stepdown ratio. Converter operates at high switching frequency to realize merits of reduced magnetics and filters. Zero voltage turn-on is achieved for all switches and zero current turn-on and turn-off is achieved for all diodes for both buck/boost operation. Voltage across switches and diode is clamped naturally without any external snubber circuit. Detailed analysis and design have been proposed. A proof-of-concept experimental prototype rated at 350 W has been designed, developed, and tested in the laboratory to demonstrate the performance and validate the claims of the converter for wide load variation. [ABSTRACT FROM AUTHOR]

A current-fed three-phase push–pull bidirectional dc–dc converter is proposed with unique features of natural zero current commutation and natural device voltage clamping. The proposed topology is suitable for uninterruptible power supply, storage, renewable energy sources, and interfacing two dc buses of 48- and 380-V dc buses in a dc microgrid. The proposed converter implements a novel and innovative modulation that results in natural commutation with zero current switching (ZCS) and device voltage clamping of low voltage side (LVS) current-fed devices, and zero voltage switching (ZVS) turn-on of high voltage side (HVS) voltage-fed devices. It eliminates the use of passive/active clamp circuits to mitigate the turnoff voltage spike across the devices, a traditional problem associated with current-fed topologies. Additionally, the higher ripple frequency reduces the volume of the transformer and the input inductor, making it suitable for high-power applications. The detailed modulation scheme, steady-state operation, and analysis, design, and soft-switching conditions have been explained. Simulation results obtained using PSIM 9.3 have been illustrated to verify the modulation, analysis, and proposed design. Experimental results have been demonstrated for full load (1 kW), half-load (500 W), and 20% load conditions on a proof-of-concept hardware prototype to validate the claims and performance. The efficiency is plotted against various load conditions for a wide range of battery voltage variation (40–59 V). Peak efficiencies of 95.8% and 93.8% are obtained at half-load condition for an input voltage of 59 V and nominal voltage (48 V), respectively. The experimental results for battery charging (reverse direction) using dual phase-shift plus pulsewidth modulation are given. The ZVS of HVS switches and the synchronous rectification of LVS active switches are shown through experimental results. [ABSTRACT FROM AUTHOR]

An impulse-commutated current-fed three-phase dc/dc converter is proposed. It is a three-inductor current divider topology that reduces the current stress of the components. The proposed converter attains zero current switching (ZCS) of the semiconductor devices via impulse commutation utilizing the circuit paracitics. The devices' voltage is clamped at Vo/n. Voltage clamping and zero-current commutation of devices are load independent. Load voltage is regulated by employing variable-frequency modulation. The current-fed topology with inherent boost ability simplifies the transformer design by reducing the required turns ratio. Rectifier diodes also commutate with ZCS without ringing and eliminate the need for a secondary snubber. A comprehensive study of the proposed converter together with the experimental results obtained from a laboratory prototype of 1 kW have been presented to validate the claims and to evaluate the converter's performance. The proposed converter is suitable for low-voltage high-current applications requiring high voltage gain. It inherently offers short-circuit protection. [ABSTRACT FROM AUTHOR]

A non-isolated impulse commutated current-fed voltage doubler based non-isolated inverter for a solar photovoltaic, battery or fuel cell application is proposed in this paper. Impulse commutation enables device voltage clamping with zero current commutation of the semiconductor devices. It eliminates the traditional problem of turn-off voltage spike across the devices in current-fed converters. Unlike resonant converters, resonance pulse appears for a very short interval leading to zero current turn-off of devices. It therefore, limits peak and circulating currents through the components. Voltage doubler is selected to achieve 2 $\times$ gain. Variable frequency modulation ensures output voltage regulation with input and load variations. Steady-state operation and analysis of front-end converter is explained. A 500 W prototype has been designed and developed to demonstrate the performance and verify the proposed operation, analysis, and claims. [ABSTRACT FROM AUTHOR]

Multilevel converters (MLCs) have emerged as standard power electronic converters for medium-voltage high-power industrial applications. Owing to dominating device switching losses in high-power applications, it is preferable to use low device switching frequency (LDSF) modulation techniques. Then, it is possible to achieve higher device utilization, higher converter efficiency, and reduced cooling requirements. However, there exists a tradeoff between device switching frequency and harmonic distortion of converter output currents. Therefore, the main challenge for LDSF modulation techniques is to minimize the harmonic distortion of the output currents. The goal of this paper is to provide a review of various LDSF modulation techniques proposed in the literature and also discuss in detail about one of the emerging LDSF control techniques known as synchronous optimal pulsewidth modulation. Finally, challenges to LDSF modulation techniques for emerging multilevel topologies and future trends in applications of MLCs are discussed to motivate further research, to enhance the proposed LDSF techniques, and to explore for new alternatives. [ABSTRACT FROM PUBLISHER]

The multilevel topology with dual inverters feeding both ends of an open-end stator winding of an induction motor has been introduced around two decades ago. A common-mode inductor is usually required in series with motor windings to suppress zero-sequence or common-mode currents. In case of medium voltage high-power drives, low device switching frequency operation is preferred to improve the overall system efficiency. However, it increases the harmonic distortion of machine stator currents. Therefore, the goal of our study is to propose new optimal pulse width modulation to achieve: low device switching frequency, minimal harmonic distortion of machine stator currents, and elimination of zero-sequence currents. The main idea is to select the switching angles of two inverters such that zero-sequence components are eliminated and, then, perform optimization to determine switching angles thatminimize the harmonic distortion of machine stator currents. The experimental results obtained from dual two-level and dual three-level inverter fed 1.5-kW open-end stator winding IM drive demonstrated the effectiveness of a proposed modulation technique. [ABSTRACT FROM AUTHOR]

Multilevel converters (MLCs) emerged as standard solutions for medium voltage (MV) high-power industrial ac drives. MV drives require low device switching frequency operation due to the higher switching losses of semiconductor devices. However, low device switching frequency operation leads to an increase in the harmonic distortion of machine stator currents. Therefore, there is a need to implement low switching frequency modulation technique for MLCs, which does not compromise on the harmonic distortion of machine currents. The goal of this paper is to propose a new optimal pulsewidth modulation technique for a cascaded seven level (7L) inverter such that the maximum device switching frequency is limited to the rated fundamental frequency (50/60 Hz) and all power semiconductor devices operate at identical switching frequency. Optimal switching patterns were determined offline assuming steady-state conditions. Later, switching angles for each semiconductor device are determined and stored in an FPGA controller. A low-power prototype of the 7L cascade inverter has been developed to demonstrate the proposed modulation technique. The experimental results demonstrated that the proposed optimal modulation technique maintains the quality of machine stator currents while the device switching frequency is limited to the rated fundamental frequency. [ABSTRACT FROM PUBLISHER]

A low device switching frequency operation is essential in medium-voltage (MV) high-power drives to increase semiconductor device utilization as well as to achieve higher overall system efficiency. However, there exists a tradeoff between device switching frequency and harmonic distortion of machine currents. Synchronous optimal pulsewidth modulation (SOP) is an evolving technique for controlling multilevel inverters of MV ac drives at low device switching frequency without compromising the quality of machine currents. The state-of-the-art generalized SOP algorithm for five or higher level inverters leads to unequal device switching frequency, and also, transients in machine currents are possible due to the change in the number of switching instants at higher modulation index values. The goal of our study is to propose a new SOP technique that ensures equal device switching frequency and further reduces device switching frequency compared to the generalized SOP method. Also, it is expected that machine current transients at higher modulation index values will be reduced. The proposed SOP technique has been verified experimentally on a cascade nine-level inverter-fed 1.5-kW induction motor drive. [ABSTRACT FROM PUBLISHER]

A soft-switching extended secondary universal current-fed converter (ESUC) has been proposed, analyzed, and designed. The proposed converter accommodates a wide source voltage range to cover several sources to interface through extended secondary-circuit and hybrid modulation. Proposed fixed frequency hybrid modulation and design achieves soft-switching of semiconductor devices under all operating conditions. It is therefore suitable to be universally adopted for solar photovoltaic (PV), fuel cell, and battery applications. Current-fed technology is suitable for such sources (low voltage, high current). Experimental results are illustrated to verify the claims and to show the performance of the converter over a wide input voltage range of 20–60 V with load variation. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

Impulse commutated current-fed push–pull (ICCPP) converter has been analyzed and designed. The topology maintains zero-current switching (ZCS) of the semiconductor devices. Variable frequency modulation has been adopted to regulate load voltage and achieve ZCS over variable input voltage. At fixed input voltage, ZCS and load voltage are load independent. Natural clamping of devices is achieved via impulse commutation. Push–pull converters have only two devices with common ground with source requiring simple gate drive circuitry. A comprehensive study of the proposed converter, including steady-state analysis and design, has been reported. A 500-W prototype was developed in the laboratory to evaluate and demonstrate the performance of the converter. [ABSTRACT FROM PUBLISHER]

This paper presents a soft-switching current-fed full-bridge front-end-converter-based bidirectional inverter for residential photovoltaic (PV) applications. The proposed converter is an intrinsic isolated boost converter with a high-step-up voltage conversion ratio. The device voltage is naturally clamped owing to proposed secondary modulation. Zero-current commutation of current-fed devices is novel and makes the converter snubberless and fully soft-switched with natural clamping of the devices' voltage. Zero-current switching of primary devices and zero-voltage switching of secondary devices are achieved. Soft switching is inherent and is maintained during wide variation of input voltage and load independent. Steady-state operation, analysis, and design have been explained. A 200-W laboratory prototype of the inverter is developed and tested to demonstrate the performance over wide variations in input voltage and output power for PV applications. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) residential power system is an important application of renewable energy. The parallel-connected configuration of PV modules rather than the series-connected configuration become popular considering the safety requirements and making full use of the PV generated power for the PV residential generation system. In this paper, a novel soft-switching current-fed push-pull front-end converter-based inverter is proposed. Push-pull converter has only two primary devices with common ground to supply and results in simple and reduced gating requirement. The device voltage is clamped naturally by secondary modulation without active clamping circuit or passive snubbers. Zero-current switching of primary devices and zero-voltage switching of secondary devices is achieved. Soft-switching is inherent owing to proposed secondary modulation, load independent, and is maintained during wide variation of input voltage and power transfer capacity, and thus is suitable for PV applications. A 250-W laboratory prototype of the converter is built and tested to demonstrate the converter performance over wide variations in input voltage and output power for PV applications. [ABSTRACT FROM AUTHOR]

This article proposes a novel single-phase bridgeless Cuk-derived power factor corrected (PFC) converter with reduced component count for on-board EV charging application. The unique feature of this proposal is to design and operate the output inductor of the converter in discontinuous current mode for the complete power range to attain PFC naturally at ac mains, thereby not requiring the input voltage and input current sensing, which reduces the converter cost, and improves the power density as well as converter robustness to high-frequency noise. The converter control is very simple in operation and easy in implementation with only a single sensor-based voltage control loop. The semiconductor components voltage stress of the proposed power converter is lower when compared to the traditional Cuk converter. The simulation results from PSIM 11 and experimental results are given by testing a proof-of-concept hardware laboratory prototype to demonstrate the high performance of PFC operation of the proposed converter. [ABSTRACT FROM AUTHOR]

Summary: This paper proposes a new buck‐boost integrated multilevel inverter with reduced capacitors and capacitor size. The proposed multilevel inverter consists of a 5‐level basic unit formed by two interleaved buck‐boost converters, whose outputs are cascaded with the source to achieve a voltage gain of five. The capacitors present in the buck‐boost converters are charged at the high switching frequency; therefore, the proposed multilevel inverter utilizes small capacitors compared to the existing switched capacitor multilevel inverter (SCMLI) topologies. Moreover, capacitors presented in the conventional SCMLI are limited to fixed voltage charging, whereas the capacitors of the proposed inverter can be charged to desired voltages by adjusting respective buck‐boost converter duty cycles. Hence, the proposed inverter requires a relatively less number of compact capacitors to produce the higher number of voltage levels. In this paper, the design and operation of the proposed 11‐level inverter are presented. A 500 W proof‐of‐concept is developed and the experimental results are presented for linear and nonlinear loads under static and dynamic load conditions. In addition, a comprehensive comparative study of the proposed inverter and the recent SCMLIs is presented. [ABSTRACT FROM AUTHOR]

Conventional droop control is widely used for achieving proportional power sharing in islanded microgrids. The active power sharing becomes proportional to the ratings of the inverters by applying the conventional droop control. However, reactive power sharing is not proportional because of resistive feeder impedance, unequal feeder lengths, and asymmetric load distribution in the network. In this article, an existing control strategy that has been proposed for improving reactive power sharing is enhanced by removing its dependency on communication. The required synchronization for executing the correction is generated by each inverter locally using a load change detection algorithm. This modification also makes the original control strategy immune to load changes happening during the correction process. An almost accurate reactive power sharing is achieved by applying the proposed modification even for highly resistive networks. Also, a tradeoff required in tuning the controller gain is discussed. The efficacy of the proposed modification has been validated by performing detailed simulation studies and by carrying out exhaustive experimental studies on a laboratory prototype. [ABSTRACT FROM AUTHOR]

In this article, an agent-based transactive energy (TE) trading platform to integrate energy storage systems (ESSs) into the microgrids’ energy management system is proposed. Using this platform, two different types of energy storage market models are proposed to promote local-level (within the microgrid) and communal- or global-level ESSs’ participation in the intra- and intermicrogrid TE markets. Also, a reinforcement learning algorithm known as simulated-annealing-based $Q$ -learning is used to develop bidding strategies for ESSs to participate in the TE markets. Besides energy trading, the proposed system also accounts for the losses caused by energy transactions between ESSs and microgrids using a complex current-tracing-based loss allocation method. The overall efficacy of the proposed energy market management system is demonstrated using a modified IEEE 123-bus distribution system with multiple microgrids and ESSs. Based on simulation results, it is observed that the proposed model can effectively reinforce the balance between the supply and the demand in the microgrids using the mix of local and global ESSs. [ABSTRACT FROM AUTHOR]

This paper presents a novel insulated gate bipolar transistor (IGBT) behavioral model on the field programmable gate array (FPGA), which is suitable for the real-time simulation of fast transients in power electronics circuits. In this model, the static and dynamic behaviors of the IGBT switch are described and modeled separately. The static IGBT model is represented by the saturation region of output characteristic and is a part of the circuit network model. The dynamic IGBT model is combined with the static one to describe the fast switching transient behaviors by using the IGBT equivalent circuit model. The presented dynamic model in this paper does not involve any iterative solving algorithm and can be designed with highly pipelined structures on FPGA. Therefore, the IGBT switching transient waveforms can be generated precisely with a 5 ns resolution. The proposed model is tested with two cases—a four-phase floating interleaved boost converter and a three-phase five-level modular multilevel converter. The effectiveness and accuracy of the model are validated by comparing the real-time simulation results with offline simulation software. [ABSTRACT FROM AUTHOR]

The goal of the paper is to develop a hybrid modulation technique to combine space vector modulation (SVM) scheme and synchronous optimal pulsewidth modulation (SOPWM) technique for current source inverter (CSI). SVM provides better dynamic performance, but is unable to produce less total harmonic distortion (THD) on inverter current at low device switching frequency ($< $ 1 kHz). SOPWM provides less THD even at low device switching frequency, however it needs a conversion technique to operate CSI and it needs an additional control technique to improve dynamic performance. Hence to overcome these limitations, this paper develops a single modulation technique called optimal SVM technique that can achieve less THD as well as better dynamic performance. To develop optimal SVM technique, three methods have been proposed in this paper. These three methods do not require an additional conversion technique to operate CSI and they provide less THD even under low device switching frequency of 450 Hz. Experimental results prove that the proposed modulation technique can provide better steady-state performance as well as dynamic performance. [ABSTRACT FROM AUTHOR]

The emulation of virtual resistance finds various applications in the power processing industry. This paper proposes a novel notion of adaptive sliding mode based loss free resistor (ASLFR). This is achieved by allowing the input power of the power-out power-in (POPI) system to vary, in order to accommodate the load demands. In this paper, the concept is illustrated for power-factor correction (PFC) applications. The ASLFR is used to achieve the dual purpose of harmonics-free rectification along with excellent system response under load and line transients. The scheme serves itself as an efficient single-stage PFC solution. A generic mathematical formulation of the scheme is presented, which can be used for different converters. Then on, a boost topology, operating in continuous conduction mode, is chosen to demonstrate theoretical developments and to showcase the effectiveness of the scheme. The robustness of the proposed controller to any line or load variation is established. A fast voltage recovery with almost no undershoot/overshoot is achieved at transients by using the proposed controller. Additionally, a qualitative analysis is provided to demonstrate the expediency of the proposed ASLFR. The theoretical claims are well supported by simulation as well as experimental results. [ABSTRACT FROM AUTHOR]

This paper proposes dual phase shift modulation (DPSM) for active commutated current-fed dual active bridge for low-voltage (LV) high-power application to improve the performance of the converter at light loads. The proposed DPSM uses an additional control variable to actively control the peak current in the converter that helps to improve the performance as compared to simpler single variable but unregulated peak current control, phase shift modulation (PSM). The control variables are chosen such that the excess current is just enough to achieve zero current switching (ZCS) turn-off of the LV devices. In the reverse direction, the converter is a full-bridge converter with LC filter. The implementation of the conventional PSM to the full bridge, popularly known as phase-shift full bridge is simple but restricted by the zero voltage switching (ZVS) range. The proposed DPSM is implemented in the reverse direction to maintain the ZVS turn-on of the high-voltage (HV) devices even at very light loads by utilizing the LV devices instead of using them only for synchronous rectification. At higher loads where achieving ZVS is relatively easy, the modulation shifts to conventional PSM to reduce the circulating current and the associated duty cycle loss. The improvement in the performance is validated experimentally with a 1-kW prototype developed for a 30 $\%$ variation in the LV voltage (42–56 V) for both directions of operation. The control of the peak current improved the efficiency by 12 $\%$ from the conventional PSM at 10 $\%$ load at the highest current (42 V) in the forward operation. In the reverse direction, the ZVS turn-on for the HV devices is achieved even at 6 $\%$ load by the proposed modulation at the highest voltage (56 V). Thus, the proposed DPSM is a software-only solution that does not require any additional active or passive components, offering an improved performance while maintaining a low component count and simplicity of the power electronics circuit. [ABSTRACT FROM AUTHOR]

Large-scale photovoltaic (LSPV) energy conversion systems have been installed at many places across the world. The essential component of the LSPV system is the dc–ac conversion stage. The usage of multilevel converters is one of the recent advances in the dc–ac conversion stage of the LSPV system to enable transformer-less inversion. Current-fed multilevel inverter has been chosen in this paper as it provides high power inversion with inherent voltage boosting, and thus, avoids the usage of transformer. High power conversion necessitates low device switching frequency operation in order to satisfy thermal constraint of semiconductor devices and also to improve efficiency. However, low device switching frequency operation leads to higher harmonic distortion of inverter output currents. Synchronous optimal pulsewidth modulation (SOP) technique is an emerging low device switching frequency modulation technique that has been successfully implemented for voltage-source multilevel inverters. However, the state-of-the-art SOP technique cannot be directly applied to modulate current-source multilevel inverter topologies due to additional constraints on the switching commutations. Therefore, the purpose of our study was to propose a modified SOP technique to achieve: low device switching frequency and minimal harmonic distortion of inverter output currents. The topology of current-fed five-level inverter was used for demonstrating the performance of proposed technique. A generalized conversion method was introduced in the modified SOP technique for including switching constraints of the current-fed inverter. In addition, a state-sequencing machine was developed by utilizing redundant inverter states to produce equal switching commutation among all semiconductor devices at minimal switching frequency of 350 Hz. The experimental results obtained from the five-level current-source inverter of 1.2 kW demonstrated the effectiveness of the proposed SOP technique. [ABSTRACT FROM AUTHOR]

A current-fed full-bridge bidirectional voltage doubler with secondary-assisted device voltage clamping and zero-current commutation (ZCC) is proposed for fuel cell vehicles (FCVs). The proposed topology is suitable for interfacing energy storage and/or fuel cell stack with a dc bus in FCVs. A voltage doubler on the secondary side is selected to enhance the gain by 2 $\times$, reduce transformer size, and efficiently reduce the low-frequency dc current harmonics. Parasitics-based zero-voltage switching (ZVS), secondary-based zero-current switching of low-voltage-side devices, and ZVS of secondary devices are achieved. The proposed secondary modulation technique naturally clamps the voltage across the primary-side devices with ZCC, thus eliminating the necessity for traditional active-clamp or passive snubbers. Switching losses are reduced, owing to the soft-switching of all semiconductor devices. Steady-state analysis and design are studied and explained. The experimental results of a 1-kW proof-of-concept hardware prototype are shown to demonstrate the performance and confirm the proposed claims. [ABSTRACT FROM PUBLISHER]

Large-scale photovoltaic energy conversion systems have been installed at many places across the world and they handle higher power levels. In high power conversion, low device switching frequency operation is preferred in order to satisfy the thermal constraints of semiconductor devices and also to improve efficiency. However, low device switching frequency operation leads to higher total harmonic distortion (THD) of the converter output currents. Synchronous optimal pulsewidth modulation (SOP) is an emerging low device switching frequency modulation technique, which has been successfully implemented for voltage source inverters without compromising on THD. The goal of our research is to propose, analyze, and implement a modified SOP technique for current source inverter topologies. The additional switching constraints for these inverter topologies have been included in the modified SOP technique. The experimental results obtained from a low-power prototype demonstrated its effectiveness. [ABSTRACT FROM AUTHOR]

Efficient power conversion technologies are strategic to the advancement of fuel cell vehicles (FCVs). This paper presents an overview of power conditioning system (PCS) architectures for an FCV propulsion system. Two new power conversion topologies to obtain variable ac from the fuel cell system are proposed. The switching of the power devices are based on the proposed hybrid modulation technique that minimizes the switching losses in the inverter. The proposed converters do not use the dc-link filter capacitors. Elimination of the dc-link capacitor not only reduces the size and volume but also helps in retaining the sine wave modulated information at the input of a three-phase inverter. Bidirectional converter topologies are proposed for interfacing low-voltage battery and fuel cell dc bus. Experimental results are presented for the proposed topologies. [ABSTRACT FROM AUTHOR]

This article presents detailed small-signal modeling and closed-loop control design for transient performance evaluation of a high-frequency snubberless isolated current-fed push–pull dc–dc converter. The topology attains the natural commutation of semiconductor devices through zero current switching. The state-space averaging technique is employed to derive the transfer functions. A two-loop average current controller is designed and implemented on a digital signal processor to evaluate and demonstrate the transient performance of the converters. A complete procedure for a closed-loop control design is illustrated. Simulation results using PSIM 11.1.64 with the designed controller are shown to validate the stability of the system. Experimental results demonstrated satisfactory transient performance at various load conditions of the converter and validated the derived model and the control design. [ABSTRACT FROM AUTHOR]

Renewable energy generations have been attracting sustained attentions in academic and industry. Current-fed-isolated-bidirectional dc/dc converters (CF-IBDCs) are widely adopted in low-voltage high-current applications such as solar photovoltaic fuel cell with energy storage. This paper gives an overview and a comprehensive comparative evaluation of CF-IBDCs. The active clamped, dual half-bridge, L-L type dual active bridge, resonant-type, naturally clamped, and other type topologies of CF-IBDCs are investigated, analyzed, and compared regarding their circuit topological structures, operation characteristics, modulation methods, and soft-switching technologies. In addition, component cost models and loss models of converters are deduced and presented. On this basis, quantitative and comprehensive performance comparison of seven typical CF-IBDC topologies selected from each type is conducted in terms of costs, losses, weight, volume, and power density for the given system specifications and design constraints. Finally, the application range of different CF-IBDCs and future trend are presented to encourage further development. [ABSTRACT FROM AUTHOR]

The battery management system in electrified transportation requires an accurate battery model for online state estimation of the battery. The parameters of the battery model depend upon state of charge, C‐rate, and temperature. A detailed battery model defined by 31 polynomial coefficients is used for determination of battery parameters. The parameter estimation is formulated as an optimisation problem and six different meta‐heuristic optimisation techniques are utilised for solving it. The efficiency of optimisation techniques is compared in terms of solution quality, computation efficiency, and convergence characteristics. Further, their performance is analysed statistically using parametric (t‐test) and non‐parametric tests (Wilcoxon test). The parameters values estimated by applying optimisation techniques are cross‐validated with value of parameters extracted using standard constant‐current pulse charge–discharge test to establish the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

The battery management system in electrified transportation requires an accurate battery model for online state estimation of the battery. The parameters of the battery model depend upon state of charge, C-rate, and temperature. A detailed battery model defined by 31 polynomial coefficients is used for determination of battery parameters. The parameter estimation is formulated as an optimisation problem and six different meta-heuristic optimisation techniques are utilised for solving it. The efficiency of optimisation techniques is compared in terms of solution quality, computation efficiency, and convergence characteristics. Further, their performance is analysed statistically using parametric (t-test) and non-parametric tests (Wilcoxon test). The parameters values estimated by applying optimisation techniques are cross-validated with value of parameters extracted using standard constant-current pulse charge--discharge test to establish the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]