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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 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]

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]

The battery management system (BMS) of battery electric vehicles (BEVs) requires highly fidelity equivalent circuit model of battery to replicate its behavior in real-time applications. The estimation of parameters of battery model is a nonlinear, high-dimensional, and complex problem. In this paper, the determination of battery parameters is expressed as an optimization problem with an objective function defined as minimization of the Manhattan distance between catalog voltage and estimated voltage curve. The dependency of model parameters on C-rate and State of Charge (SOC) has also been accounted. Six different heuristic optimization approaches are implemented for minimizing the objective function, and their performances have been compared statistically using parametric and nonparametric tests and based on their convergence characteristics. The proposed method is tested on Energy Innovation Group (EIG) battery with nominal voltage 2.5 V and capacity 8 Ah. The battery parameters are also obtained using the pulse current charge–discharge test and used as a benchmark to compare the results of the proposed method. [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]

This paper presents a novel six-pulse low-frequency (LF) fluctuating high-voltage dc-bus-based power system architecture for fuel cell vehicles (FCVs) application. A novel hybrid modulation scheme consisting of six-pulse modulation at LF scale and modified secondary modulation and 33% pulse width modulation at high-frequency (HF) scale is proposed. Three-phase ac waveforms for the propulsion system of FCVs are generated from LF fluctuating high-voltage dc bus. The proposed modulation technique significantly reduces the switching losses of the bidirectional dual-stage inverter: 1) soft-switching of both sides of the front-end current-fed full-bridge converter is realized; and 2) at any moment, only one leg of back-end three-phase inverter is switched at HF, while the other two legs are kept in on or off states. This tremendously reduces the bidirectional inverter's switching losses and improves the system efficiency. The LF fluctuating high-voltage dc bus allows the elimination of large electrolytic dc-link capacitor, which contributes to a more reliable and compact design. This paper presents the operation, analysis, and design of a bidirectional inverter implementing the proposed hybrid modulation technique. Simulation results obtained from power electronics simulation software PSIM and experimental results from the lab prototype clearly validate the effectiveness of the proposed modulation technique. [ABSTRACT FROM PUBLISHER]

As it has changed gradually from more electric aircraft (MEA) to all electric aircraft, the stabilization of the on-board dc power system is a hot research topic in recent years. In such an application, small and light systems are required, and thus, the optimization of passive LC filter is a significant issue. It is known that reduction of the LC filter capacitor will cause instability when the constant power load is employed. There is always a compromise between stability margin and system size. A practical method using the current perturbation was proposed in order to stabilize the on-board power system. The main objective is to suppress the instability and improve the stability margin, while keeping the benefits of the low weight and volume. The mathematical model of the system is analyzed, and the simulations and experimentations are performed to confirm the validity and effectiveness of the proposed method. [ABSTRACT FROM PUBLISHER]

Cascaded bidirectional dc–ac converters are commonly used in uninterruptible power supply applications and battery chargers for electric vehicles. Power conversion units for such applications employ a large electrolytic capacitor at high-voltage dc bus, which not only reduces the lifetime but also adds to the weight of the converter. In this paper, a novel bidirectional dual active bridge cascaded three-phase converter (DABCC) with six-pulse dc link is proposed. Also, a new closed-loop control scheme to implement the six-pulse modulation (SPM) technique in DABCC is proposed. The advantages of the proposed control scheme in DABCC are that the electrolytic capacitor is eliminated and is replaced with a low-value film capacitor resulting in increased reliability, compactness, and reduced cost. SPM technique also increases the dc bus utilization and decreases the inverter average switching frequency to 33% when compared with the conventional sine pulse-width modulation (SPWM). Harmonic components introduced in the pole voltages of the SPM-modulated DABCC due to inverter dead time are analyzed, and a resonant controller is designed to mitigate them. Also, root mean square current stress for high-voltage dc-link capacitor is studied, and it is shown that the capacitor requirement for SPM modulation is lower than the conventional SPWM. To validate the proposed control scheme, an 800-W proof-of-concept laboratory hardware prototype is fabricated and experimental results are demonstrated. [ABSTRACT FROM PUBLISHER]

Three-phase inverters in uninterrupted power supply, electric vehicles, and hybrid electric vehicles use an intermediate dc-link electrolytic capacitor, which has reliability issues and is one prominent cause of inverter failure and limited life. The large volume of an electrolytic capacitor increases the size and cost of the system. Recent research on electrolytic capacitorless inverters using six-pulse modulation technique along with high-frequency power conversion has attempted to address this issue. However, closed-loop operation and control has some issues due to capacitorless dc-link. In this paper, closed-loop operation, design, and implementation of an electrolytic capacitorless inverter is presented. A proof-of-concept 1-kW hardware prototype has been built and tested in a laboratory under different loading conditions. In total, 98% rated efficiency of the inverter is obtained with total harmonic distortion within 2%. Transient results during start-up and load change are smooth, demonstrating safe operation of the inverter. [ABSTRACT FROM AUTHOR]

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]

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]

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]

In order to reduce the influence of the grid harmonic currents and voltages, harmonic compensation is regularly implemented for a grid-tied inverter. In this study, a new topology of a higher order power filter for single-phase grid-tied voltage-source inverters, named L(LCL)2 , is presented. The subscript is added to the name to prevent confusion with the LLCL filter. In the proposed design, the inverter side inductance is divided into three parts, and the grid side inductor is removed. Also, an additional resonant branch at the double of the switching frequency is added to the traditional LLCL filter to attenuate high-frequency harmonics. The overall inductance of the recommended filter is smaller than the LLCL filter. A comparative study and discussions on the subject of the traditional LLCL filter and the proposed L(LCL) 2 filter have been conducted and assessed through an experimental hardware implementation on a 700 W, 120 V/60 Hz single-phase grid-tied inverter. Furthermore, a straightforward engineering design benchmark is suggested to discover parameters of the L(LCL) 2 filter. Moreover, stability analysis, loss analysis and an optimization of the L(LCL)2 filter parameters have been conducted in this study. The analysis shows that in comparison with the LLCL filter, the L(LCL)2 filter not only has lower voltage drop and less total inductor size, but also has improved performance in decreasing high-order current harmonics. [ABSTRACT FROM AUTHOR]

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]

In electrical power converter systems, the presence of an LC input filter can efficiently reduce the Electromagnetic Interference (EMI) effect, and at the same time protect the converter and the load from being impacted by sharp input impulse voltages. However, for transportation applications, the weight and size limitations of input LC filters for power converters have to be taken into consideration. The reduction of LC filter size may impair the system stability margin and dynamic response. In serve cases, the system may even become unstable. Thus, in order to ensure the system stability while minimizing the input LC filter size, the implementation of a stabilizer for the system control is needed. In this paper, a novel digital stabilizer design method is proposed for a boost power converter with a small input LC filter. The proposed method is based on input filter inductance current measurements and DSP (Digital Signal Processor)-based digital stabilizer design. Simulation and experimentation confirm the validity of the proposed approach. [ABSTRACT FROM AUTHOR]