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An electrical transient model (ETM) of insulated-gate bipolar transistor (IGBT)-diode switching cell is developed by coupling a temperature-dependent IGBT model with power loss model. The nonlinear behavior of IGBT and the reverse recovery characteristic of the diode are considered in this model to simulate the transient switching waveforms. Based on the transient waveforms of ETM under various operating conditions, the power loss estimation method (PLEM) for IGBT is developed. In addition to traditional modeling techniques that only uses ideal switch, this paper uses the model to replicate the power loss behaviors of semiconductor devices in circuit simulation by looking up tables. The proposed ETM is simulated in PSCAD/EMTDC with nanosecond time step, whereas the overall system application can be simulated with conventional time step in range of microsecond. By this way, the model can promise reasonable accuracy as well as an acceptable fast solving speed. The proposed ETM and PLEM have been implemented in PSCAD/EMTDC simulator and validated by experimental results using a double pulse test bench and boost converter test platform. [ABSTRACT FROM AUTHOR]

A matrix converter (MC) with model predictive control based on the source reactive power control usually fails to show sinusoidal source currents. The analysis presented in this paper shows that this common combination of a converter and control has the inherent inability to suppress some harmonics in the source currents, even with additional passive or active damping control. Direct source current control can be implemented to give sinusoidal source currents and intrinsic active damping. However, the issue of steady-state error in output currents then arises, as the MC topology does not allow of the independent control of source and output currents. Therefore, feedback control of load active power is proposed to address this issue without degrading the fast dynamic performance. Benefiting from the direct source current control, a simplified implementation is also proposed to decrease the number of candidate switching states from 27 to 5, which significantly reduces the computational burden. Experimental results have verified the theoretical analysis and the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

This paper proposes a novel dual active bridge (DAB)-based high-frequency-isolated dc–ac converter topology suitable for photovoltaic microinverter applications. The circuit configuration on the secondary sides of the employed three-winding transformer results in high-frequency current injection into each of the switch nodes, thereby making zero-voltage-switching (ZVS) operation of the devices possible. The topology achieves this functionality while using the same number of devices as conventional two-stage and single-stage high-frequency-link or DAB-based solutions. Furthermore, following a control-oriented power pulsation decoupling strategy involving dynamic variation of phase shift, twice line-frequency energy buffering can be handled on the high-voltage secondary side, thereby resulting in reduction in decoupling capacitance requirement. The working principle of the circuit and the associated control scheme is described followed by a detailed ZVS analysis. Simulation studies and experimental tests on a 310 W prototype verify circuit operation and exhibit efficiency improvements compared to a similar two-stage solution. [ABSTRACT FROM AUTHOR]

This paper presents a new single-phase ac–dc–ac three-level three-leg converter composed of three coupled-inductors and six active switches. The system model, operation principles, and a control strategy are presented and discussed. Additionally, a space-vector pulsewidth modulation technique is developed to double the effective frequency of the grid and load voltages and to reduce the switching losses. The proposed converter is compared to other similar converters in terms of switch count, harmonic distortion, and power losses. The results show that the proposed topology has improved power quality and uses fewer switches and gate drive circuits. These characteristics can potentially reduce the costs and the complexity of the system. In addition, the proposed converter eliminates the requirement for dead time to prevent short circuit of the dc-link. In order to validate the theoretical analysis, simulated and experimental results are presented and discussed. [ABSTRACT FROM AUTHOR]

With the conventional secondary phase-shifted (PS) control, a semidual-active-bridge (S-DAB) dc–dc converter suffers from low efficiency at light load in buck mode due to hard switching and high tank current. In order to avoid this phenomenon and extend soft-switching range, a hybrid control including the primary pulsewidth modulation plus secondary phase-shifted (PWM+PS) is proposed in this paper. Under the proposed hybrid control, all steady-state operation modes with distinctive features are identified and analyzed. Based on the operation range, power characteristics and switching behaviors in each mode, a minimum peak current control route is developed, which can enable the converter to work with low tank current and soft switching over the whole load range. A lab-scale S-DAB converter is implemented to validate the theoretical analysis, and experimental results reveal that the higher efficiency can be achieved using the proposed control route. [ABSTRACT FROM AUTHOR]

This paper presents a pulsed power modulator with a new structure that utilizes the reverse recovery characteristics of diodes to achieve an effective pull-down circuit configuration. The proposed configuration for active pull-down applicable to negative pulsed power applications with a high-voltage direct switching method is implemented by adding a diode to the pulse discharging path of the modulator, instead of using a pull-down resistor. The diode is forward-biased while an output pulse voltage is applied to the load. When the pulse voltage applied to the load is removed, the residual energy in the load is quickly discharged through the reverse recovery path of the diode so that the pull-down function of the pulsed power supply system is efficiently performed. The operating principle of the proposed system is described, and each operating mode is analyzed in detail. In addition, the feasibility of the proposed system configuration is examined through various simulation results. Finally, it is proven that the proposed system can be used effectively in pulsed power application fields through a practical experiment in plasma source ion implantation applications. [ABSTRACT FROM AUTHOR]

Battery energy storage system based on the modular multilevel converter (MMC-BESS) is able to realize the decentralized management of battery packs, which is suitable for the retired battery utilization to improve the efficiency of battery recycling. With multiple submodules (SM), the corresponding SM fault ride-through method is mandatory to improve operational reliability. This paper proposes a redistributed pulsewidth modulation method for MMC-BESS to ride-through the SM fault through employing the simple logic operation, which could avoid the unexpected carrier shift under various modulation indexes induced by the SM fault or grid voltage rise. MATLAB simulations and experimental results are presented to verify the performance of the proposed method. [ABSTRACT FROM AUTHOR]

The measurement of fast voltage and current transients of Silicon Carbide (SiC) devices requires high bandwidth (BW) probes. Commercially available voltage and current probes can be expensive, and, in addition, the delay introduced by them must be compensated to achieve a proper time alignment (de-skew). Determining this de-skewing value is not a trivial task. In this paper, a simple and affordable measurement method is presented for the simultaneous measurement of the voltage and current transients of SiC devices. The voltage is measured by means of a high BW RC attenuator, while the current is estimated from the voltage drop in the stray inductance of the switching loop. Since both voltages are measured with two equal and matched high BW passive voltage probes, there is no need to apply any de-skew. This is one of the most important advantages of the method. The presented method is experimentally evaluated and used for the estimation of energy switching losses in the tested SiC-mosfet. [ABSTRACT FROM AUTHOR]

This paper describes the design, robustness analysis, and implementation of a zero average dynamics sliding mode control (ZAD–SMC) for a multiphase step-down converter. The ZAD–SMC operates at fixed switching frequency and allows to implement an interleaving technique providing current-ripple cancellation at the converter output. Moreover, the proposed control structure, which is based on a master–slave strategy, includes an equalization technique guaranteeing current sharing among the phases and avoiding undesirable power unbalance. Additionally, a stability analysis considering unmatched losses in the converter phases shows that the design provides asymptotic stability for the overall load range. The controllers are implemented in an FPGA, and all the expected features, such as fast transient response, robustness, fixed switching frequency, interleaving, and current equalization are sustained by the experimental results obtained from using a 1.5-kW prototype. [ABSTRACT FROM AUTHOR]

Finite control set model predictive control (FCS-MPC) calculates torque and flux tracking errors via a cost function that is used for selecting the optimal vector. Compared with field oriented control, FCS-MPC has the merit of a faster dynamic performance because it eliminates both pulsewidth modulation and inner proportion-integration controllers. However, the weighting factor for modifying torque and flux terms must be tuned in accordance with varying operating conditions; this is an area in which further research is needed. In this paper, a parallel predictive torque control (PPTC) with predefined constraints is proposed as a solution for this problem. The PPTC method optimizes torque and flux terms simultaneously, and switching-state candidates are then selected in an adaptive mechanism. The key feature is that torque and flux tracking errors are constrained within the initial boundaries. The proposed PPTC is compared with the state-of-the-art predictive torque control (PTC) method. Both simulation and experimental results confirm that the proposed method, which has no weighting factor, achieves an even better dynamic performance and robustness than the conventional PTC. [ABSTRACT FROM AUTHOR]

In this paper, a novel topology of modular dc–dc converter has been proposed for medium voltage dc (MVdc) integration of high-penetration distributed PV. The proposed topology is featured with input-independent and output-series connected configuration and intermodule power balancing units (PBUs). A high voltage gain could be achieved with series-connected submodules (SMs), while each SM's input port is connected with PV array to realize the independent maximum power point tracking (MPPT) control function. PBUs with bidirectional power conversion ability are installed between adjacent SMs for the elimination of intermodule power mismatch. The operation principles of the proposed converter have been explained in detail along with the corresponding control strategies. The design principles of major passive components have been investigated on the basis of boundary operation conditions, while a quantitative analysis of steady-state power losses has been performed. Moreover, a comparative study is conducted from the aspects of operation range, topology complexity, component stress, and power efficiency. The theoretical results have been validated by both simulations and down-scaled experiments. [ABSTRACT FROM AUTHOR]

Nine-switch converter (NSC) has been presented as a dual-output converter with common frequency (CF) or different frequency (DF) operation modes. This paper proposes a novel space-vector modulation (SVM) method for the NSC that supports both the CF and DF modes. This method is based on the simplification of the space-vector diagram of NSC into that of six-switch converter, and the SVM method for NSC can be done like conventional SSC. The proposed voltage vector selection method without using common logical xor operation and the calculation method for dwelling times of voltage vectors are described in detail. In addition, the modulation indices for two ac terminals of NSC have been analyzed deeply, and the derived fitting equations can guide engineering application. The performance of the proposed SVM is verified by the simulation and experimental results, and the low total harmonic distortions and harmonic components for phase currents prove the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) strings consisting of multiple panels suffer from partial shading or characteristic mismatch issues, such as a significant reduction in power yield. Various kinds of differential power processing (DPP) converters have been developed to prevent the negative impacts of substring-level partial shading. For panel-level applications, however, conventional DPP converters face a variety of challenges, such as impaired extendibility and increased voltage stress of circuit elements. This paper proposes a switched capacitor converter (SCC)-based modular DPP architecture. Modules, each containing series-connected panels with a panel-level DPP converter, are connected through a switchless module-level DPP converter, and PV panel characteristics are unified at module- and panel-levels. The number of panels in each module is fixed, while the number of modules can be arbitrarily extended without redesigning DPP converters, hence offering good modularity. In addition, since voltage stresses of capacitors in the proposed architecture can be reduced lower than half the module voltages, the proposed DPP system realizes all-ceramic-capacitor SCC circuit by properly determining the module voltages. A prototype for eight panels, which were grouped into two modules, was built, and laboratory and field tests were performed. The experimental results demonstrated the enhanced power yield from the partially shaded PV string. [ABSTRACT FROM AUTHOR]

The three-phase dual-active bridge converter is a promising topology for the high-power high-frequency dc–dc conversion, due to the soft-switching capability and inherent galvanic isolation. With the state-of-the-art instantaneous current control (ICC) based on the single phase-shift (SPS) operation, a bidirectional power flow can be controlled dynamically between two dc ports without inducing overshoots in the transformer currents. However, a transient dc-bias flux may still occur in the transformer, which may cause the transformer core saturation in the dynamic operation such as start-up, power-off, and abrupt load changes. To analyze and address this issue, this paper presents a set of model-based methods to avoid inducing the dc-bias flux in various transient situations. The proposed double-side SPS operation could nullify the dc-bias flux in abrupt load changes and even instant power-flow reversals. Furthermore, the soft-magnetizing and soft-demagnetizing techniques are presented to eliminate the initial and residual dc-bias flux during start-up and power-off instantly. The proposed flux control method can be integrated with the ICC. Thus, the transformer magnetizing flux and the winding currents can be controlled simultaneously and instantaneously in transient situations. Simulations and experiments on a down-scaled hardware prototype validate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

This paper employs a single-phase-shift modulated dual-active-bridge converter (DABC), and establishes a small-signal model, which involves its voltage transformation ratio. Then, through a voltage transformation ratio feedback loop, which is feedforward compensated by the port voltages and currents, closed-loop control of the transformation ratio of the DABC is realized. The proposed controller can make the DABC operate in constant transformation ratio mode, and act as an ideal dc transformer in an active dc distribution network. Based on the bidirectional voltage support capability of the proposed dc transformer, the different buses of an active dc distribution network can mutually provide voltage support for each other. Besides, the proposed dc transformer can realize the normalized decentralized power coordination between the energy storage systems at different buses of the active dc distribution network. The feasibility of the proposed dc transformer is verified by several hardware-in-loop tests. [ABSTRACT FROM AUTHOR]

The Cuk dual resonance core (DRC) realizes overlapped dual resonance to regulate its output voltage. However, the DRC configuration was only applied to the Fibonacci switched-capacitor converter (SCC), series–parallel SCC, and voltage doubler. In this paper, the Cuk DRC is modified and then is extended to the Dickson SCC to form a multi-resonance-core-based (MRC) Dickson resonant switched-capacitor converter. All charging and discharging loops achieve soft charging, and so the inherent capacitor charge sharing loss and the high current transient spikes are eliminated. The modular configuration makes the MRC Dickson easy to be extended to a higher voltage level. The on-time fixed frequency modulation is adopted, all transistors being turned on with zero-current-switching (ZCS) operation and all diodes being turned off with ZCS operation. Most importantly, the conversion ratio of the MRC Dickson can be regulated continuously, widely, and efficiently even at light load condition, which is a huge advantage over the traditional Dickson SCC with limited control headroom. A comprehensive analysis of the operation principle, voltage-gain curve, component stress analysis, and output characteristic is provided. The converter operation principle and regulation capability were verified by both simulation and experiment. [ABSTRACT FROM AUTHOR]

This paper proposes a model predictive flux control (MPFC) strategy with cost function-based field weakening (FW) strategy for permanent magnet synchronous motor (PMSM). The stator flux vector is used as the control variable and the cost function of the proposed MPFC is configured in the form of flux increment, which can reflect the saturation degree of the inverter output. A novel space flux vector plane is introduced to explain the principle of optimal switching state selection in the proposed MPFC. The voltage and current limitations of the inverter in the high-speed region are analyzed in the flux plane to reveal the objective of FW compensation. The value of the cost function is controlled with a proportional integral controller in the proposed cost function-based FW strategy. Moreover, the reference flux vector is compensated with the output of the FW controller to enlarge the operation region of the stator flux vector. With the proposed FW strategy, the operation range of the PMSM is extended and the torque output in high-speed range is increased. Experimental studies are carried out to verify the validity and effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

Load-independent output characteristics of inductive power transfer (IPT) systems are increasingly popular in battery charging. This paper proposes a novel variable-parameter T-circuit (VT) for an IPT system charging a battery with constant current (CC) or constant voltage (CV) output. The VT can transfer a CC/CV input to a CC or CV output by using an ac switch and a passive component (inductor or capacitor). An IPT system with a VT for CC–CV charging can reduce the number of passive components and ac switches. Besides, the proposed VT merits more design freedom of charge current/voltage with the constraints imposed by the loosely coupled transformer parameters compared to that of the traditional one. In addition, there are three kinds of VTs for various IPT charging systems with different requirements. A 400 W laboratory-scale prototype with a 150 mm air gap was built to verify the theoretical analyses. Both electronic load and lead-acid battery are utilized to verify the charging profile of the proposed method. The experimental results of the IPT system indicate that the fluctuation of the charging current in CC mode is less than 2%, and the change rate of charging voltage in CV mode is within 2.9%. The maximum overall efficiency 93.93% of the charging system is achieved from a dc 110 V input to a dc 100 V output. [ABSTRACT FROM AUTHOR]

This paper proposes the design of gray wolf optimizer (GWO) algorithm-based fractional order proportional integral (FOPI) controller for power factor correction (PFC) using interleaved dc–dc single ended primary inductance converter converter with improved performance characteristics such as speed, accuracy, and stability. The detailed analysis and modeling of the proposed converter are presented. The optimal parameters of FOPI controller are obtained using GWO algorithm to improve the speed of response of the system. FOPI controller provides better performance in terms of robustness and stability since it has one more adjustable parameter than the conventional proportional integral (PI) controller. The cascade control strategy is implemented for the proposed converter with GWO-based FOPI controller as inner current and outer voltage controllers for PFC and load voltage regulation. The performance characteristics of the proposed system are analyzed and compared with conventional and other optimization techniques using MATLAB/Simulink software. A prototype of the proposed converter controlled by TMS320C2000 microcontroller for an output power of 200 W is tested and validated with the simulation results. The proposed system is used for powering devices like robots in critical applications such as military, space craft, etc., where stability, speed, and accuracy are major concerns. [ABSTRACT FROM AUTHOR]

A novel nine-level inverter topology for low-voltage applications is proposed in this paper. Each phase of the inverter is composed of a T-type three‐level cell and an active neutral point clamp three‐level cell. The operation principles and current conduction paths are analyzed in detail and phase-disposition sinusoidal pulsewidth modulation is used to balance voltages of flying capacitors and neutral point. The mathematical relationship between the capacitance and the desired ripple in the inverter output is established to select the intermediate capacitance value. Compared with other nine-level inverters suitable for low-voltage applications, the proposed inverter has advantages in a number of gate drivers, a number of dc sources, and efficiency. Simulation and experimental results under different settings of modulation index, power factor, output frequency, and load are presented to verify the effectiveness and performances of the proposed inverter. [ABSTRACT FROM AUTHOR]

As a combination of the switched-mode converter and linear amplifier, the switch-linear hybrid (SLH) envelope tracking (ET) power supply can achieve high efficiency and high tracking bandwidth simultaneously, and it can be classified into three types, namely, series-form, parallel-form, and series–parallel-form. In the SLH ET power supply, interaction may occur between the converters, and as a result, the controlled variable will deviate from its target. In this paper, the interaction in the series-form SLH ET power supply with different structures is analyzed first from the aspects of control and parasitic capacitances, and the feedforward control scheme and/or filter is adopted to eliminate the interaction. Then, for the parallel-form SLH ET power supply, four current control methods are introduced and compared from the current tracking and disturbance-rejection performances, and the method for suppressing the disturbance is presented. Since series–parallel-form SLH ET power supply contains at least three converters, the interaction is more complex. On the basis of the analysis of the series-form and parallel-form SLH ET power supplies, the interaction between the converters in series–parallel-form SLH ET power supply is analyzed and followed by the corresponding elimination method. Finally, one series-form, and one parallel-form SLH ET power supplies are implemented in the lab, and the experimental results verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

The device-level real-time simulation of power converters is constrained by the contradiction between the required short simulation time step to describe the transient behaviors and the large computational amount caused by the nonlinearities of switches’ models. In this paper, a novel low-latency device-level power converter modeling approach is proposed for field programmable gate array (FPGA)-based real-time simulation. A piecewise linear insulated-gate bipolar transistor (IGBT)/diode transient model is proposed based on the inductive switching behaviors. The switching transient is modeled into four phases, which are identified by the boundaries between three operating regions of IGBT and between two operating modes of a diode. Moreover, each phase is approximated by a linear continuous behavior in order to reduce the real-time computational amounts. Accompanied by the effective boundary identification, the device-level IGBT/diode model can be efficiently integrated into the real-time simulation with low computational latency. A dc–dc–ac topology model is implemented on the FPGA-based real-time platform, as a case study to verify the effectiveness and practicability of the proposed approach. With the help of circuit partitioning techniques, the device-level converter model can be simulated with a 50-ns time step on FPGA. Moreover, the accuracy of FPGA-based simulation results is validated by the error evaluation with respect to the results from offline simulation tools. [ABSTRACT FROM AUTHOR]

In this paper, a method is proposed to eliminate the voltage ringing problem in a phase-modulated dc–ac converter, also known as a micro-inverter. The basic idea is to apply a time-critical two-stepped voltage waveform to the input of the converter bridge connected to the filter inductor. This method is implemented by a new topology that has one more switching leg added to the full bridge voltage fed converter. It produces a second voltage level and adds it to the first by using a transformer. The advantages of the proposed method are as follows. It almost eliminates the requirement of a voltage clamp, there is no circulating current in the freewheeling state, and the secondary side devices have less voltage and current stress compared to a conventional phase-modulated converter. The overall benefit is an improvement in converter efficiency even for a high-voltage conversion ratio application. The proposed topology operates with a secondary side modulation scheme that achieves zero-voltage switching of four devices on the primary side and either zero-voltage switching or zero-current switching of all the devices on the secondary side, over the entire line cycle of the ac output. Finally, the experimental results verify the proposed method. [ABSTRACT FROM AUTHOR]

Pulsed power loads (PPLs) are becoming prevalent in medium-voltage naval dc micro-grids. To alleviate their effects on the system, energy storages are commonly installed. For optimal performance, their interface converters need to have fast dynamics and excellent disturbance rejection capability. Moreover, these converters often need to have voltage transformation and galvanic isolation capability since common energy storage technologies such as batteries and supercaps are typically assembled with low-voltage strings. In order to address these issues, a moving discretized control set model predictive control (MDCS-MPC) is proposed in this paper and applied on a dual-active-bridge converter. Fixed switching frequency is maintained, enabling easy passive components design. The proposed MDCS-MPC has a reduced prediction horizon, which allows low computational burden. The operating principle of the MDCS-MPC is introduced in the development of a cost function, which provides stiff voltage regulation. Resonance damping and sampling noise resistance can also be achieved with the proposed cost function. An adaptive step is introduced to enable a fast transition. Assessments on the performance of the proposed MDCS-MPC are conducted. Comparisons with other control methods are also provided. Experimental validations on a 300 V/300 V 20-kHz 1-kW dual-active-bridge converter are carried out to verify the theoretical claims. [ABSTRACT FROM AUTHOR]

DC circuit breakers (DCCBs) are vital for the safe and continuous operation of large high-voltage dc grids. Insulated-gate bipolar transistor-based hybrid DCCBs (IHCBs) can interrupt currents quickly and have good operational characteristics. Thyristor-based hybrid DCCBs (THCBs) are superior to IHCBs in terms of interruption capacity because of the large surge current capacity of thyristors. Nevertheless, existing THCBs have limitations regarding one or more of the following characteristics: pre-activation, fast reclosing, quick interruption of small current and no requirement for an additional pre-charge source. This paper proposes a thyristor full-bridge-based dc circuit breaker (TFCB) with all favorable characteristics mentioned above. The TFCB contains a main conductor, a main breaker (MB), an auxiliary branch, and an energy absorber. After an interruption, the capacitor in the TFCB can restore its initial voltage quickly to guarantee that the TFCB is available for the next interruption. Quick interruption of small currents is achieved using the additional charge current provided by the auxiliary branch. Pre-activation is achieved using the conduction path in the MB. The parameter designs are analyzed to ensure that the TFCB reliably interrupts currents without damaging itself. The proposed TFCB is validated using prototype experiments and PSCAD/EMTDC simulations. [ABSTRACT FROM AUTHOR]

In general, misalignment in a wireless power transfer system is inevitable, which decreases the efficiency of the system. In this paper, a full-bridge dual resonant tank (FBDRT) topology is proposed to improve the system efficiency under the lateral-misalignment condition of a wireless power transfer system. The topology with two transmitters connected with two separate half bridges is employed to deliver power to the load. Operating principle, efficiency, current, power, and soft-switching region of the proposed method are analyzed in detail, and a comparison is drawn in with the traditional series–series topology. Theoretical analysis shows that the equivalent impedance of the transmitters can be adjusted, utilizing the phase-shift modulation. The proposed method holds a higher efficiency and a wider soft-switching region when the phase is selected reasonably. A 100 W prototype is built to validate the feasibility of the proposed topology. The efficiency of FBDRT is always higher than 88.3% with an improvement of 6.8%, compared with that of the traditional SS topology when the lateral misalignment increases from 0 to 200 mm (0%–50% of maximum coil size). [ABSTRACT FROM AUTHOR]

Generally, battery-fed capacitive loads are charged to high voltages in series of switching cycles with smaller fragments of energy delivered to the load in every cycle to ensure an efficient charging process. In high voltage low power (HVLP) flyback charging circuit, significant portion of input energy drawn from the source in a cycle is utilized by the effective parasitic capacitance of the HV transformer and semiconductor devices and circulated back to the source at the end of the cycle. This reduces the energy delivered to the load per cycle and hence the net energy delivered in the charging process. In this paper, an energy-based analysis and simplified energy-based model for HVLP charging circuits is derived. An energy-based approach is appropriate to describe and define the HVLP converter behavior in terms of load energy component and circulating energy component. The derived energy-based model is extended to obtain analytical closed-form expressions governing the essential parameters of the charging circuit. The proposed energy-based model and analytical formulation of essential parameters are experimentally validated on a 0–2.5 kV programmable high voltage charging circuit prototype fed from 12 V input battery source. [ABSTRACT FROM AUTHOR]

In a conventional linear-control design of a higher order power-electronic system (PES), the gains of the control laws are typically determined by small-signal analysis of the averaged model of the PES. The closed-loop control of such a PES (driving a pulsating load that periodically shifts the equilibrium) using its small-signal model is often found to be unsatisfactory with regard to the overall stability and performance. To address the challenges in control design for a PES driving such a nonlinear time-varying pulsating load, this paper delineates an optimal switching-sequence-based control (SBC) scheme, which applies stability-bound switching sequence(s) to the PES. A novel method has been formulated to ensure the reachability of the PES dynamics based on its switching sequence in terms of the time horizon of the switching sequence and the allocation of this time among the switching states of the same switching sequence. This is ascertained by modeling the PES and the pulsating load as a nonlinear map and then using this map and multiple Lyapunov functions determined by solving a set of linear-matrix inequalities corresponding to each of the switching states of a given switching sequence. It has been further shown that the knowledge of the stability bounds of a reachable switching sequence helps in reducing the online computation time for optimal SBC associated with solving the optimization problem by reducing the overall search space. Finally, to validate the optimal SBC, an experimental GaN-FET-based 100-kHz  Ćuk-PES has been fabricated and tested on a pulsating load. The overall SBC is implemented on a low-cost TMS320F28335 DSP, which also implements an observer to preclude the need for plurality of sensors for the higher order Ćuk-PES. The overall performance of the SBC is found to be satisfactory under varied dynamical conditions. [ABSTRACT FROM AUTHOR]

This paper presents the circuit design and magnetic integration of push–pull class-E inverters for wireless power transfer (WPT) up to megahertz. The design criterion for achieving zero-voltage switching (ZVS) of a class-E inverter with coupled windings is derived mathematically. The approaches of magnetic integration for push–pull class-E inverters are analyzed and compared. Then, a new magnetic structure with hybrid magnetic materials is proposed to build the integrated inductors with either coupled windings or uncoupled windings. A 3-MHz WPT system is built to verify the analysis. The detailed comparison of the class-E inverters with magnetic integration is presented in terms of switch voltage, efficiency, harmonic currents, and thermal distribution. In the optimized design example, the switches keep ZVS over the entire load range without using any closed-loop control. The system efficiency reaches 87.1% at 350-W output power. [ABSTRACT FROM AUTHOR]

Improving the power density of a power converter has many benefits for systems integration. Aspects such as thermal management, weight, conformation to mounting locations, and the footprint of the converter all become critical factors as systems continue to scale down in size. The flying capacitor multilevel converter topology is of interest because it has characteristics which contribute to high power density. This paper presents a quasi-square-wave zero-voltage switching (ZVS) multilevel dc–dc converter. ZVS greatly reduces switching losses and enables high-frequency operation of the converter. A hardware prototype is implemented, built on a flexible polyimide substrate circuit board. Experimental results show a peak system efficiency above 98.1%, an effective switching frequency of up to 3 MHz, and a power output of 250 W. [ABSTRACT FROM AUTHOR]

In this paper, two single-phase single-stage split-inductor buck–boost inverters are proposed: type-I and II. The proposed type-I is unity power factor inverter, while the proposed type-II inverter is suitable for any power factor. Both topologies remove the shoot-through problem. Furthermore, the reverse recovery issues for all switches are eliminated; therefore, mosfets are used to obtain higher efficiencies. The proposed inverters operated at higher switching frequencies confer the additional benefit of smaller passive components. The current stresses of the two switches in the proposed type-I and II inverters are lower of the conventional boost inverter. The dead time can be eliminated at both the high and line switching frequencies. In addition, the inductor conduction loss is minimized to improve efficiency. Moreover, the voltage stresses of the two switches in the type-I inverter can be much lower of its counterpart boost inverter. Most importantly, unlike the conventional high-reliability inverters, the magnetic volume of the proposed high-reliability type-I and II inverters is same of its counterpart boost inverter. The experimental results obtained for 500 W, 110 Vrms, 60 Hz hardware prototypes verify the analysis. [ABSTRACT FROM AUTHOR]

Three-phase power factor correction rectifiers are an essential area of power electronics, supplying a direct current load with tens of kilowatts, or more, from the public three-phase mains and achieving sinusoidal input currents. In many applications, isolation is required between the mains and the load, for example, due to safety reasons or different grounding schemes. This paper describes the modulation, design, and realization of a buck–boost-type, unity-power-factor, isolated matrix-type, dual-active-bridge, three-phase rectifier. It uses a circuit similar to a conventional dual-active-bridge converter, but employs a direct matrix converter to connect the high-frequency transformer's primary winding to the mains. A soft-switching modulation scheme is proposed and comprehensively analyzed, deriving closed-form solutions and numerical optimization problems to calculate switching times that achieve minimal conduction losses. Based on this analysis, the design of an 8-kW 400-V rms three-phase ac to 400-V dc prototype is discussed, striving for the highest possible efficiency. Using 900-V SiC mosfets and a transformer with an integrated inductor, a power density of ${\text{4}}\; {\text{kW}\cdot \text{dm}^{-3}}$ (${\text{66}}\; {\text{W}\cdot \text{in}^{-3}}$) is achieved. Measurement results confirm an ultrahigh full-power efficiency of 99.0% at nominal operating conditions and 98.7% at 10% lower input voltage. [ABSTRACT FROM AUTHOR]

Analysis and design of a single-switch high step-up coupled-inductor boost converter are presented in this paper. With the aid of the coupled inductor, the proposed converter can achieve high-voltage gain without extreme duty cycle. Also, low switch voltage stress can be achieved, thus low-voltage-rating mosfet is allowed to lower the conduction loss. Moreover, the proposed converter features continuous input current, which is desirable and friendly to the battery, fuel cell, and photovoltaic applications. In addition, the reverse recovery problem of the diodes can be alleviated and leakage energy can be recycled. The operation principles and characteristics of the proposed converter are discussed. Experimental results are provided to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

When the interleaved boost power-factor correction (PFC) converter operates in a light load (<15% of nominal load), the phase-shedding control is commonly used to increase the converter's efficiency. If the inductors are coupled for high power density applications, because of the strong mutual effects of the coupled inductor, the switching of the operation phase may lead to a current flowing in the non-operation phase. In this paper, a two-phase interleaved boost PFC converter with a coupled inductor in the single-phase operation was analyzed. The operation modes of the converter in a switching cycle and a half line cycle were presented, and the modes’ variation with the load changes, as well as the power distribution, was provided. A 1-kW prototype was built to verify the analysis, and it was shown that the non-operation phase also delivers some power, which may worsen the converter's efficiency and distort the average input current waveform. [ABSTRACT FROM AUTHOR]

This paper presents a self-adapting synchronized-switch harvesting (SA-SSH) interface circuit to extract energy from vibration-based piezoelectric energy harvesters (PEHs). The implemented circuit utilizes a novel switching technique to recycle optimum amount of harvested charge on piezoelectric capacitance to strengthen the damping force, and simultaneously achieve load-independent energy extraction with a single inductor. Charge recycling is realized by adjusting extraction time, and optimized through a maximum power point tracker based on charge-flipping dissipation. The circuit has been implemented using 180 nm HV CMOS technology with 0.9 × 0.6 mm2 active area. Self-adapting SSH circuit has been validated with both macro-scaled and MEMS PEHs with different inductor values. The interface circuit provides maximum energy extraction for the full storage voltage range of 1.8–3.7 V. The implementation harnesses have 500% more power compared to an ideal full-bridge rectifier, and output 3.4 μW for 2.24 V peak-to-peak open-circuit piezoelectric voltage from MEMS PEH excited at its resonant frequency. [ABSTRACT FROM AUTHOR]

In the control of permanent magnet synchronous machines (PMSMs), predictive controllers have received considerable attention due to the enhanced dynamic responses. However, periodic disturbances caused by dead-time effects and sampling errors deteriorate the performances of PMSMs. In order to suppress periodic disturbances, one typical control structure is to adopt several corresponding resonant controllers connected in parallel with the main controller. Even though excellent steady-state performances can be obtained, coupling effects between reference tracking and periodic disturbance attenuation can be observed, leading to significant transient oscillations under the situation of a reference step change. In order to realize decoupling between reference tracking and disturbance attenuation, this paper proposes a dual-loop predictive control structure, in which the reference tracking is only determined by the primary predictive controller. Periodic disturbance attenuation is achieved through an embedded disturbance rejection loop. By applying the proposed controller, periodic disturbances are strongly attenuated while smooth and fast transient performances are simultaneously guaranteed. Furthermore, a wide range of low frequency harmonics can be successfully suppressed, including but not limited to the main periodic harmonics. The steady-state performance, dynamic responses, and robustness against parameter variations of the proposed controller are verified through experiments based on a 2.3-kW PMSM. [ABSTRACT FROM AUTHOR]

In photovoltaic applications, many previous research works have focused on pulsewidth modulation (PWM) resonant converters in order to achieve a high efficiency with a wide input voltage range. Conventional approaches utilized symmetric boosting modulation at the secondary side rectifier to obtain a symmetric operation, and they utilized two boosting modes in a switching period. Among various rectifier structures, the voltage doubler structure has a strong advantage due to a small number of components. However, it suffers from serious hard switching losses in the secondary side rectifier. In this paper, a new converter with a novel asymmetrical modulation is proposed and verified. The strong point of the proposed converter is that it eliminates hard switching turn-on losses from the rectifier, while maintaining the minimized number of components. Although the proposed converter adopts an asymmetric modulation, the offset current on the transformer becomes zero inherently. Furthermore, a “forced half resonance” operation of the proposed converter keeps rms current stresses at the same level as conventional converter although it has a higher peak current. Accordingly, the proposed converter achieves a superior efficiency with the minimum number of components at 35–25 V input and 380 V/300 W output specification. [ABSTRACT FROM AUTHOR]

Three-phase current reconstruction techniques with a single current sensor have been studied for permanent magnet synchronous machines (PMSMs) drive system due to its reducing cost and volume. In order to minimize the current reconstruction dead zone in the conventional method with a single dc-link current sensor, a strategy to couple multiple available positions through the single current sensor is proposed in this paper. With the proposed method, two independent equations of the stator currents can be obtained by sampling the single current sensor twice in both zero voltage vectors and active voltage vectors. By solving these two equations, the phase current reconstruction can be achieved accurately, which moves the current reconstruction dead zone toward six corner area of the space vector hexagon. Meanwhile, in order to guarantee the proposed method suitable in the whole linear modulation region, the suitable selection of the pulsewidth modulation switching period is analyzed in detail. Furthermore, the optimal selections of multiple sampling positions are discussed to lower the actual implementation difficulty of the proposed method. Finally, the experimental results on the PMSM demonstrate that the reconstructed phase currents with the proposed method can be always in consistent with the actual measured currents under different working conditions. [ABSTRACT FROM AUTHOR]

In the no-load condition, LLC converter usually fails to regulate its output voltage although it operates at a high switching frequency. Till now, it is hard to obtain the exact relationship between design parameters and the maximum switching frequency for no-load regulation capability. In this paper, a specific criterion for no-load regulation of LLC converter is provided, without using active components or other modulation schemes. By analyzing the macroscopic switching period and microscopic switching transition in the no-load condition, it is shown that not only the peaking resonant current during the switching transition, but also the resonant tank design affect the no-load regulation of the LLC converter, which affects the no-load regulation capability. Furthermore, the relationship among design parameters is analyzed and the design guideline is also provided to achieve no-load regulation at the specified maximum switching frequency. To verify the effectiveness of the proposed design, 400 V input and 50 V/200 W output prototype is built and tested. [ABSTRACT FROM AUTHOR]

Multi-phase magnetically coupled resonant (MCR) wireless power transfer (WPT) technology can fulfill the requirements of time-varying spatial positions of loads in mid-range applications, as it can generate a rotating magnetic field around sending coils, and effectively reduce the limits of spatial positions on transfer characteristics including output power and transfer efficiency. Nevertheless, the design of coils parameters and control strategies put a great influence on the realistic transfer characteristics, which should be considered elaborately in practice. In this paper, a three-phase MCR WPT system with cylinder-shaped coils is investigated, the equivalent circuit model is built to carry out the theoretical analysis. Based on that, the influence on zero-voltage-switching (ZVS) conditions of power switches and the output power of the system, resulting from different phase-shifted angles between each phase, coil turns and angular misalignments of the receiving coil, is analyzed comprehensively. Detailed discussions on relationships among coil turns, the angular misalignment, ZVS conditions, and the output power are completed under different phase-shifted angles. Furthermore, the parametric optimization of coil turns, as well as phase-shifted angles, are proposed to ensure the power switches realize ZVS and ensure the system realize stable output power within the full range of angular misalignment. Finally, experiments are carried out to evaluate the accuracy of theoretical analysis and confirm the validity of the proposed optimal design. [ABSTRACT FROM AUTHOR]

A systematic method for developing ultra-wide output voltage range power supply based on modular switched-converter principle is proposed in this paper. The basic symmetric switched-converter (SSC) module is composed of two dc–dc modules, two diodes, and one active switch. Multi-stage SSC modules are generated by symmetric cascaded connection method. By controlling the active switches in multi-stage SSC modules, the connections of all the dc–dc modules’ output ports can be changed flexibly among series, parallel, and partial–parallel–partial-series connections. Then segmented regulation can be realized and system output voltage range can be widely extended. Meanwhile, the voltage range of each dc–dc module can be narrowed and the voltage/current stress can be reduced to simplify the design, increase device utilization ratio, and improve overall efficiency. A full-bridge isolated buck–boost converter with a semiactive rectifier, which features soft-switching and wide voltage adjustment range, is adopted as the dc–dc module to realize the proposed system. Input current sharing control strategy is adopted to ensure proper power balancing in all possible operating modes. The stability of the proposed system is also explored. Simulation and experimental results are provided to verify the effectiveness and advantages of the proposed system configuration, the switched-converter principle, and the control strategies. [ABSTRACT FROM AUTHOR]

This paper presents a reduced component count five-level inverter topology based on the stacked cell approach to multilevel inverters. The proposed topology utilizes the fundamental properties of three-phase voltages to reduce the number of switches and flying capacitors to cut size, weight and costs while facilitating higher reliability, simpler wiring and lesser electromagnetic interference. The operational aspects of the topology such as circuit structure, modulation and capacitor balancing are explained, followed by an account of device stresses and reliability. A discussion of certain additional features such as fault tolerant operation, loss steering and common-mode elimination addresses the usefulness of the topology in practical situations. A comparison of the proposed topology with existing methods in terms of several parameters is then used to highlight its merits and features. Finally, experimental results obtained using an induction motor drive incorporating the topology are given, so as to validate the feasibility of the proposed approach. [ABSTRACT FROM AUTHOR]

The low-frequency fluctuation over the capacitor voltages seriously limits the development of medium-voltage variable-speed drives with a modular multilevel converter (MMC). Therefore, this paper presents an effective strategy of the low-speed and start-up operation for an MMC-based motor drive. The proposed strategy properly coordinates the improved injection and the reduced average capacitor voltage with high applicability. The specific interactions between the control parameters and the system metrics are analyzed to give the detailed steps of the parameters designing. Hence, based on the derivations, the proposed method enables the low-frequency operation under the nominal load torque with decreased injected components and reduced peak capacitor voltages. What is more, two start-up strategies that, respectively, aim at different objectives for the coordinated strategy are proposed, indicating satisfying control performances for the practical applications. The injected common-mode voltage and circulating current in the proposed method are designed to have a great reduction. Thus, the unfavorable risks for the motor are evidently decreased for better stability. The reduced peak current also lessens the high stress on switching devices with desirable reliability. The simulation and experiment results of an MMC-based motor drive prototype prove the effectiveness and superiority of the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents a delta-sigma modulation (DSM) control scheme for noninverting buck–boost (NIBB) converter that features a duobinary encoding for four power switch controls. The proposed scheme converts the single-bit output of the modulator into a 1.5-b signal to enable a three-phase operation comprising the charging, bypassing, and discharging phases. This control method reduces both switching and conduction losses by changing only two switches in each period, thus, achieving high conversion efficiency. A smooth mode transition is provided by the DSM controller, which automatically and continuously determines the operating mode of the converter. Thus, the dead zone can be effectively released with improved transient responses. Furthermore, the spurious tones in the output are effectively eliminated by the robust noise shaping capability of the modulator. The proposed DSM-based NIBB converter was implemented on a 180-nm CMOS. It regulated the output in the range of 2.0–4.6 V with input voltage of 2.5–5.0 V, and the maximal load current was 500 mA. The converter showed a peak efficiency of 94.8% at 90-mA load and the output voltage ripples were maintained under 18 mV. A low noise floor with the first spurious peak located –92 dBc below the signal was achieved across all mode operations. In addition, the converter occupied a small chip area of 1.51 mm2. [ABSTRACT FROM AUTHOR]

The discontinuous conduction mode boost power factor correction converter features zero-current turn-on for the switch, no reverse recovery in diode, and constant frequency operation. With traditional constant duty ratio control, the power transfer in each switching cycle exhibits great difference during a half-line cycle. Consequently, the peak and root mean square values of the inductor current are large, the same goes for the switch and diode. This increases not only the current stress of the power components but also the conduction and switching turn-off loss, and lowers the efficiency of the converter. Introducing third and fifth harmonics into the input current and varying the duty cycle correspondingly can reduce the aforementioned power transfer difference, and provide huge space for the increment of boundary inductance as well. An optimum boundary inductance control concerning limited power factor (PF) is proposed in this paper. For the maximum boundary inductance of the converter within wide input voltage range, the optimum harmonics amounts are analyzed and figured out. The proposed method brings about efficiency improvement, output voltage ripple reduction, and PF increase as well, especially at high input voltages. A prototype has been built and the experimental results are presented to show the validity of the scheme. [ABSTRACT FROM AUTHOR]

T-type multilevel (T2ML) inverters feature low total harmonic distortion and high efficiency. Reliability improvement is particularly important for T2ML inverters because they have high power device count. Methods that provide T2ML inverters with the ability to tolerate simultaneous failures of multiple switches in several legs have not been addressed in the existing literature. This paper proposes a redundant unit that can be shared across phases in a T-type three-level inverter topology to manage open-circuit faults in multiple legs. The redundant unit includes two switches and six diodes, with the extra active switches connected by diodes to each middle switch of the base inverter. Under fault conditions, a standby parallel leg consisting of middle switches and the added redundant devices can be formed in each phase of the inverter to provide an extra current path connecting the dc bus and loads. The middle switches can share the redundant unit simultaneously to replace faulted half-bridge switches. By these means, open-circuit faults in multiple legs can be tolerated simultaneously and the rated output capacity can be maintained during faulted operation. Experimental tests are given to verify the effectiveness and feasibility of this proposed fault-tolerant method. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) systems having rechargeable batteries are prone to be complex and costly because multiple converters are necessary to individually regulate a load, PV panel, and battery. This paper proposes novel nonisolated multiport converters (MPCs) integrating a bidirectional pulsewidth modulation (PWM) converter and phase-shift-switched capacitor converter (PS-SCC) for standalone PV systems. A PWM converter and PS-SCC are integrated by reducing the total switch count, realizing the simplified system and circuit. In the proposed MPCs, two control freedoms of duty cycle and phase shift angle are manipulated to individually regulate the load, PV panel, and/or battery. The detailed operation analysis was performed to mathematically derive gain characteristics and zero voltage switching operation boundaries. For the battery discharging mode, in which the PV panel is not available and the MPC behaves as a single-input–single-output converter with two control freedoms available, the optimized control scheme achieving the lowest rms current is also proposed to maximize power conversion efficiencies. Various kinds of experimental verification tests using a 200-W prototype were performed to verify the theoretical analysis and to demonstrate the performance of the proposed MPC. [ABSTRACT FROM AUTHOR]

As research in matrix converters (MCs) has progressed over time, space vector modulation has emerged as the most popular technique for their modulation. Lately, model predictive control (MPC) has also been explored for the modulation and control of MCs, primarily gaining popularity due to the ease in realization of multiple objectives, as desired in MCs. However, multi-objective MPC employs assignment of weights to each control objective, wherein weight tuning is either empirical in nature or computationally cumbersome. This paper proposes a new modulation technique for MCs, inspired from delta sigma modulation for voltage source converters, that can be used for load voltage and source current control of MCs. Since source currents are samples of the load current envelope, it is required that this envelope be known for the control of source current. To eliminate load current sensors, predictive model of the load is used in envelope estimation. Further, independent switching schemes are generated for each objective, and an error minimization approach is used in integrating the two schemes into a final state selection, hence eliminating weighing factors. Unlike MPC, error predictions for all states of MCs, are not needed, hence facilitating easier implementation without significant processor burden, besides ensuring the quality of response. [ABSTRACT FROM AUTHOR]

The time delay caused by the digital computation and the update of the duty cycle tend to worsen the dynamic performance of digitally controlled power converters. This paper proposes a real-time calculation method for single-phase cascaded H-bridge (CHB) inverters with the phase-shifted carrier pulsewidth modulation (PSC-PWM) to eliminate the time delay caused by the digital computation in the control loop without the loss of duty cycle. In the approach, a sampling method for the PSC-PWM applied in a single-phase CHB inverter is introduced, which samples the current and voltage at points of the intersection for triangular carriers of legs in all adjacent H-bridge cells. The sampling method is used alternately with the conventional regular sampling method by following a selection rule in order to avoid the loss of duty cycle. Experimental results verify that the proposed method effectively improves the transient performance of the current control loop and suppresses the effect of the distortion of the grid voltage on the line current. [ABSTRACT FROM AUTHOR]

Boost-based converters are used in a variety of non-isolated step-up applications, such as power factor correctors, because of their simplicity. The power density of these converters can be increased in higher switching frequencies, which reduces the size of the magnetic elements. This increases the switching losses, but that can be solved by soft-switching techniques. This paper proposes a resonant bridgeless power factor correction converter that provides soft switching for all of the semiconductors. The proposed structure can provide zero voltage switching for the switches and zero current switching for the diodes. In the proposed structure, the input current is inherently sinusoidal with low total harmonic distortion, even with small inductances. Therefore, a high input power factor is achieved without requiring a current control loop in the circuit. This reduces the complexity of the control circuit. An experimental prototype has been constructed to investigate the validity of the claims. Experimental results show near-unity power factor, as well as $\text{2}\%$ efficiency improvement at full load when compared to a conventional interleaved boost converter with the same components. [ABSTRACT FROM AUTHOR]