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In this paper, closed-loop control and boundary condition for continuous conduction mode and discontinuous conduction mode of nonisolated inverting N× multilevel boost converter (MBC) are articulated. Inverting N× MBC combines the features of classical boost converter and voltage multiplier to attain inverting N times higher voltage. Consequently, the inverting N× MBC provides a viable solution for high-voltage step-up photovoltaic applications with low voltage rating reactive components and semiconductor devices. The control strategy with saturation limiter is employed to achieve highly stable voltage. The modes of operation, benefits of inverting N× MBC, and key factors for the selection of semiconductor devices and sizing of the reactive components are discussed. Additionally, the effects of reactive components and semiconductor devices on the output voltage are examined. Experimental results of the developed circuit are presented to validate the design of converter, and effectiveness and robustness of the implemented control algorithm for different input and output side perturbations. [ABSTRACT FROM AUTHOR]

This paper describes a method of fast commutation of DC current into a capacitor. Theoretical study is provided, which enables evaluation of commutating DC current for the given contact velocity, capacitance, and dielectric strength. It is concluded that a non-zero contact velocity at separation is required, and a corresponding switch design is proposed. Experimental results on a laboratory setup illustrate successful DC current commutation up to 400 A, with voltages rising to 1.3 kV. Further experiments demonstrate that parasitic parameters reduce the magnitude of the current that can be commutated. A detailed non-linear PSCAD model and a linear model for the parasitic circuit are presented to enable prediction of the success of commutation. The model accuracy is confirmed with experimental tests. The DC current commutation in the proposed method occurs 5–10 μs after the contact separation, which is much faster than with other methods employing moving contacts. A further benefit of the extremely short arcing is the elimination of thermal issues on contacts, and possible simplified design of the mechanical switch. [ABSTRACT FROM AUTHOR]

This paper presents a novel fault-tolerant method for active–neutral-point-clamped (ANPC) inverter using a modified carrier-based pulsewidth modulation. At a fault event, the ANPC inverter is divided into subinverters, and the modulating signal is modified to two modulating signals. The modified modulating signals are used to control the subinverters and allow continuous operation of the three-level ANPC inverter during faulty conditions even up to four open-switch faults per phase. This technique provides the fault-tolerant capability of the ANPC inverter without the need to add any additional phase legs or complex control strategies. Furthermore, the proposed technique ensures the voltage balancing of the dc-link capacitors. The performance of the proposed fault-tolerant technique is verified through simulation studies in MATLAB/Simulink under different faulty conditions. The feasibility of the proposed technique is also verified experimentally. [ABSTRACT FROM AUTHOR]

In this paper, a voltage sensorless controller is developed for a two-switch single-phase rectifier that involves power factor correction and active pulsating power buffering without electrolytic capacitors. While a two-switch rectifier normally requires four sensed signals for control, only one current sensor is required in this proposal, thereby offering advantages such as low cost, high compactness, isolation between control and power circuits, and improved reliability. While the basic operating principle follows that of a conventional voltage sensorless controller for single-switch converters, several critical design considerations are the key to the success of the implementation which is explained in detail. The feasibilities of the controller are experimentally testified with a 100-W rectifier prototype regarding both steady state and dynamic performance. [ABSTRACT FROM AUTHOR]

In this paper, a new transformerless buck–boost converter based on a ZETA converter is introduced. The proposed converter has the ZETA converter advantages, such as buck–boost capability, input-to-output dc insulation, and continuous output current. The suggested converter voltage gain is higher than the classic ZETA converter. In the presented converter, only one main switch is utilized. The proposed converter offers low voltage stress of the switch; therefore, the low on-state resistance of the main switch can be selected to decrease the losses of the switch. The presented converter topology is simple; hence, the control of the converter is simple. The converter has the continuous output current. The mathematical analyses of the presented converter are given. The experimental results confirm the correctness of the analysis. [ABSTRACT FROM AUTHOR]

This paper presents a modification of the Vienna rectifier (VR) to obtain more than three voltage levels at the DC line connection, while preserving the unity power factor at the AC grid side. The proposed unidirectional multilevel there-phase rectifier, called the “Negev rectifier”, has a reduced device count and utilizes a unique novel Time Division Multiplexed based control scheme, which makes the challenging N-level VR expansion possible. The Negev rectifier can serve as a grid interface for supplying dc voltage to multilevel inverters with 4 up to 7 voltage levels, eliminating the burden of inverter-side voltage balancing control. The Negev hardware can be constructed by two complementary topologies, making it suitable for either high current or high voltage applications. [ABSTRACT FROM AUTHOR]

The large amount of power electronic submodules and semiconductor switching events in the Modular Multilevel Converter (MMC) introduces several challenges for efficient and accurate Electro-Magnetic Transient (EMT) simulation. Research efforts have focused on developing Average Value Models (AVMs) of MMC that enable fast and accurate dynamic simulation of the converter. This paper proposes a universal blocking-module-based AVM, which can simulate the MMC of different submodule types and provide accurate results for the MMC operating in both blocking and de-blocking modes. An analytical approach is included in the model to calculate the semiconductor losses of different submodule types in the MMC. The proposed model is validated against a detailed switching-based model and the state-of-the-art AVMs in a 41-level two-terminal MMC-HVDC system. [ABSTRACT FROM AUTHOR]

Modeling and simulation play a vital role in the design and testing of modular multilevel converter (MMC) high voltage direct current (HVDC) systems. Detailed equivalent model (DEM) and switching-function-based average value model (SFB-AVM) are two major types of accurate and efficient models to represent the dynamic response of the MMCs. However, the DEM and the SFB-AVM possess unique benefits depending on the purpose of the simulation studies. The DEM provides a detailed representation of submodule (SM) switching events and individual capacitor ripples. The SFB-AVM provides faster simulation speed by using arm equivalent capacitance. Combining both models in a universal arm equivalent circuit gives the users the choice of selecting the most appropriate modeling method during dynamic simulation. This paper proposes a universal modeling framework combining the DEM with the SFB-AVM which allows the DEM and the SFB-AVM smoothly switch from one to the other during dynamic simulation. The proposed SFB-AVM can accurately represent the MMCs with different SM types. The proposed models are validated in offline and real-time simulation studies which demonstrate the improved simulation speeds of the proposed SFB-AVM over the DEM especially for large numbers of SMs. [ABSTRACT FROM AUTHOR]

This paper proposes a new approach for the capacitor balancing of a dual three-level T-type converter based on silicon carbide discrete semiconductors. This study is performed while the converter feeds an open-end induction motor. The model predictive control (MPC) scheme is developed to balance the dc-link capacitors and to control the machine torque simultaneously. The proposed technique for MPC reduces the number of redundant switching states that are used in computations without affecting the operating voltage vectors. This reduces the computational time substantially. In addition, the proposed control strategy mitigates the weighting factor tuning problem of capacitor balancing in addition to the conventional MPC cost function. MATLAB simulation results for the proposed drive system under different case studies are presented. Hardware experimental setup for the proposed converter is built, tested, and verified. A comparison between experimental and simulation results is presented. It is observed that the theoretical as well as the experimental results are in full agreement. [ABSTRACT FROM AUTHOR]

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

In this paper, a novel topology combining reconfigurability and hybridization is presented. Reconfigurability allows the proposed converter to operate in three different operating modes, yielding a wide range of step-up conversion ratios. The combination of two charge-pump cells and an inductor allows to reduce the average inductor current if compared to a standard equivalent boost converter. A prototype with integrated MOS, drivers, and logic but external passives was built. Experimental results show that with $\mathbf {f_{s} }=\text{300}\,$ kHz, $\mathbf {V_{in} = \text{6}}\,$ V, and $\mathbf {I_o = \text{70}}\,$ mA, the converter can cover conversion ratios in the range from $\text {2.5}$ to $\text {10}$ , with a maximum output voltage equal to $\text {60}\,$ V. Peak efficiency is $\text {91}$ %. When the output current is increased to $\text {100}\,$ mA peak efficiency is $\text {92.8}$ %. [ABSTRACT FROM AUTHOR]

Multilevel converters are widely applied in medium voltage (MV) drive systems due to the attractive features, such as the ability to use devices with lower voltage ratings, high equivalent switching frequency, etc. Recently, a multilevel topology, named seven-level hybrid clamped (7L-HC), is proposed for MV drives. It has a competitive number of devices, showing the potential to build low-cost 7L converters. However, to ensure the wide frequency range operation and power quality of MV drives, its dc-link capacitors and floating capacitors must be controlled properly with balanced voltages. In this paper, an active voltage balancing method is proposed for the 7L-HC converter. This method can effectively balance all the capacitor voltages under a wide frequency range. The method is embedded in the PWM procedure without modifying the control strategies. Simulation and experimental results are provided to validate the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, a family of new step-up series–parallel dual resonant switched-capacitor converters (SP-DRSCs) is proposed to extend the conversion ratio for high step-up applications. The converters feature a wide gain range, continuously adjustable, and enhanced light-load voltage regulation. All flying capacitors operate in resonance, eliminating high transient current spikes and charge sharing losses. Thus, zero-current-switching (ZCS) turn-on for all transistors and ZCS turn-off for all diodes are achieved. A comprehensive analysis of the operation principle, voltage-gain curves, stable regulation range, and voltage and current stress is given. An analytical method to quantify the passive component volume for the group of step-up dual resonance switched-capacitor converters is presented. Further design considerations to optimize the passive component volume of the proposed SP-DRSC and the effect of bulky bypass capacitors on the volume are discussed. [ABSTRACT FROM AUTHOR]

This paper presents a voltage multiplier topology that is a hybrid between a Cockcroft–Walton multiplier and a Dickson charge pump. The Cockcroft–Walton structure exhibits significant output voltage drop under load as the number of multiplier stage increases. This is because all coupling capacitors are connected in series. Dickson charge pump mitigates this issue by connecting all capacitors in parallel. But this solution comes at the expense of large capacitor voltage stress at the last multiplier stage. The proposed hybrid structure arranges some capacitors in parallel and others in series, thereby achieving low output voltage drop and low capacitor voltage stress at the same time. We develop a model that predicts hybrid multiplier's performance and validates it experimentally. We also demonstrate a 60–2.25 kV dc–dc converter based on a 16-stage hybrid voltage multiplier which achieves a voltage gain of 12.8 while keeping the highest capacitor voltage stress to 660 V. [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]

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]

Circuit analysis and design criteria of a two-phase bidirectional converter with high voltage gain are presented in this paper. The operating principle of the forward or reverse mode is similar to that of the conventional buck or boost converter. Compared with the conventional converter, the switch stresses can be reduced significantly depending on the operating region of the voltage ratio in the two-phase converter. The power losses can also be reduced due to the use of low-voltage rating switches. The derivate converters are discussed to demonstrate the advantages of the proposed topology. A 200 W/1 MHz two-phase prototype converter with gallium nitride (GaN) devices is built and tested to verify the feasibility. [ABSTRACT FROM AUTHOR]

In this paper, the design methodology of switched-tank converter (STC) is presented. The power loss breakdown analysis is conducted to point out the directions and paths for components optimization. It is revealed that the switching device conduction loss, printed circuit board (PCB) loss, and inductor loss become significant when output power is >150 W. Power loss of four switches is calculated and compared for switching device selection. The resonant capacitor is carefully designed to meet both current stress and ripple requirements. On the other hand, optimal design of the resonant inductors and PCB layout are fully investigated. The core loss model is provided, and different core materials are compared to minimize the core loss. Besides, a fine-tuned inductor winding structure is designed to achieve the lowest winding loss. Furthermore, PCB layout is optimized to get short loop length for each operation state. In addition to the hardware level optimization, an improved control method is proposed, in which the conduction time of switching devices is tuned to mitigate the circulating power. To verify the optimization work, a prototype of STC is built and tested. The experimental results indicate that a state-of-the-art performance of 98.71% efficiency and a 1000 W/in3 high power density is achieved. [ABSTRACT FROM AUTHOR]

For an LLC converter, it is difficult to realize the wide output range with conventional pulse frequency modulation control because of the limited operating frequency. This paper proposes a new hybrid control method. The proposed strategy combines the burst-mode control and phase-shift control methods for the LLC converter. The burst-mode control can regulate the output voltage from zero to its maximum value, and the phase-shift control can reduce the increased resonant current during burst-on time. By using this method, the wide output voltage range is realized with the low resonant current during burst-on time and zero-voltage switch (ZVS) for all switches. The reliability and efficiency of the converter can be improved accordingly. The burst duty ratio is regulated by the reference output voltage, and the phase-shift angle is derived when realizing ZVS for lagging-leg switches. Moreover, the resonant parameters and the maximum phase-shift angle are optimized under the constraints of current stress and ZVS condition. This method is easy to be implemented in a low-cost microcontroller because high-frequency real-time calculations are not necessary. A 1.5-kW prototype is built to verify the feasibility and validity of the proposed control method. [ABSTRACT FROM AUTHOR]

The modular multilevel converter is the state-of-the-art topology for voltage source converter HVDC. Despite its advantages, this converter handles large internal low-frequency energy ripples, and the capacitance that supports these dynamics is a key design parameter that affects the operating region of the converter. Different strategies can be found in the literature to increase the feasible region of operation of the converter. Nevertheless, they are typically open loop in nature and use precalculated control references. This paper presents an alternative based on model predictive control that steers the system through optimal control trajectories that are calculated online. This provides feedback and corrective control action in real time. The predictive controller used for this purpose is presented and a linear time-varying approximation is used to reduce the computational burden of the algorithm. The feasible boundaries of the converter are sought and the final performance of the control algorithm is evaluated through detailed simulations using a switching model of the converter. [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 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]

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]

A multilevel dodecagonal voltage space vector generation scheme for variable-speed drive applications with single-dc-link operation requires a large value of capacitance for cascaded H-bridge (CHB) filters, when operated at lower speeds. In existing schemes, the multilevel dodecagonal structure is obtained by cascading a flying capacitor inverter with a CHB. In this paper, a new scheme has been proposed to minimize the capacitance requirement for full speed operation by creating vector redundancies using modular and equal voltage CHBs. Also, an algorithm has been developed to optimize the selection of vector redundancies among the CHBs in order to minimize the voltage ripple of the floating capacitors. The proposed algorithm considers instantaneous capacitor voltages and phase currents for optimal selection of vector redundancies. A mathematical model for capacitor voltage deviation is presented, and the effectiveness of the proposed algorithm is verified in both the simulation and the experiment. [ABSTRACT FROM AUTHOR]

This paper presents the current control design procedure of a single-phase grid-tied five-level packed U-cell inverter (PUC5) with an LCL output filter. The PUC5 inverter is used as an interface of renewable energy sources, such as solar applications. The LCL filter is calculated according to the grid-tied operation and converter ratings. An optimal controller, based on a linear quadratic regulator with integral action, is designed to inject a sinusoidal current with low harmonic distortion at unity power factor. For that design, the PUC5 inverter is modelled in the D–Q frame. The sensorless voltage control is incorporated into the switching technique to balance the PUC5 capacitor voltage and generate a five-level waveform at the output. Experimental tests are performed on a laboratory benchmark to confirm the theoretical design. The results prove the efficiency and accuracy of the adopted control strategy in a steady state and under transients of grid current, grid inductance, ac and dc voltage amplitudes. [ABSTRACT FROM AUTHOR]

For photovoltaic applications, the flyback microinverter with pseudo-dc-link is popular as a simple topology but brings large transformer turns ratio and thus large leakage inductance, which would deteriorate the converter efficiency. To solve this issue, based on the nonisolated pseudo-dc-link structure, this paper proposed a hybrid boost–flyback/flyback (BF/F) microinverter. This new topology is operated at the BF mode for the most segment of a half grid cycle and the F mode for the rest. During the BF mode, high voltage gain with low voltage stress is easily available in minimized transformer turns ratio. Besides, the leakage energy is recycled and the turn-off voltage spike of the main switch is clamped, as a result of a passive snubber inherently contained in this mode. Given that the BF mode is lack of step-down function, the F mode is developed to regulate the output voltage even for values lower than the input voltage. The operation and characteristic of the hybrid BF/F microinverter in boundary conduction mode are analyzed in detail, and the mathematical expression of reference current is derived theoretically to guarantee high power quality. Finally, a 240 W prototype was implemented to validate the theoretical analysis and the benefits of the proposed topology. [ABSTRACT FROM AUTHOR]

This paper presents a new highly integrable hybrid step-down converter that merges switched-inductor and switched-capacitor operations and significantly reduces onboard loss by using the input cable's parasitic inductance as its main inductor. This converter has the inductor placed at the input with a smaller voltage swing, leading to possible use of a smaller inductor and low-voltage rating switches that generally translate to reduced conduction losses. Analyses of converter operation and losses to reveal its original characteristics and design guidelines are presented to facilitate the components optimization. The converter architecture is verified by a proof-of-concept 15-W inductor-less lithium-ion battery charger prototype that uses a 1-m USB 3.0 cable as inductor. The converter, switched at 2 MHz from a 5-V input, experimentally achieves 89.7% peak efficiency and 6% higher efficiency at full load than a Buck converter counterpart. This high efficiency and zero onboard inductor yield a relative 45.7% onboard loss reduction at full load, promising excellent integration feasibility and superior system thermal management. [ABSTRACT FROM AUTHOR]

This paper proposes a novel isolated high step-down conversion circuit, called an integrated buck and modified push−pull (IBMPP) converter, which is able to lower the voltage level on the primary side of the ideal transformer, resulting in a lower turns-ratio and decreased leakage inductance. The IBMPP converter is able to prevent the duty cycle from operating in extremely low conditions. Furthermore, the proposed converter adopts active-clamp techniques to recycle leakage energy and to suppress voltage spikes, so that the conversion efficiency can be effectively improved. The advantages of the IBMPP converter are its simple topology, easy control mechanism (which requires only two signals with a 180-degree phase shift), high conversion ratio, low component counts for power switches, and less voltage stress on some of the switches on the high-voltage side. The operation principle, steady-state analysis, design considerations, and experimental results of the proposed IBMPP converter are presented in detail. The feasibility of the IBMPP is verified by hardware implementation. The full-load efficiency at 250 W is 81.44%, and the input and output voltages are 380 and 5 V, respectively. [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]

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]

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 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]

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]

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]

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]

This paper presents a model predictive current control (MPCC) for three-phase four-switch converters (TPFSC) connected to surface permanent magnet synchronous generators (SPMSGs) in oscillating water column (OWC) wave energy plants, that brings some benefits over the existing control methods used in this type of plants. The proposed MPCC for TPFSC follows the current references with great accuracy, whereas the switching frequency of the insulated-gate bipolar transistor (IGBTs) is fixed and low. This method minimizes the current reference tracking error, and its fast response makes it suitable for the power take-off systems present in wave energy converters. Furthermore, the system features a fast capacitor voltage offset suppression control. The dynamic performance and the voltage offset control of the proposed strategy for TPFSC feeding a SPMSG is evaluated in the Simulink environment. Later, experimental studies are carried out on an 8.7 kW laboratory SPMSG prototype. Finally, the capability of the proposed method to harvest the maximum energy from irregular waves is assessed using an OWC power plant emulator. [ABSTRACT FROM AUTHOR]

In this paper, a new low-voltage ringing zero voltage transition (ZVT) cell is proposed for a family of non-isolated dc–dc converters. In the proposed converter, all semiconductor devices operate under soft-switching condition at both turning on and off. The proposed ZVT cell resolves the issues appeared in the previous works: no online calculation required to achieve ZVS turn-on of the main switch; no extra voltage stress imposed on the main or snubber components; no floating gate driver required for the main and snubber switches; low component count of the ZVT cell; operation principles and design guideline of the boost converter with the proposed ZVT cell are presented. Also, three different positions of a snubber diode considering its junction capacitor are analyzed to clarify the advantage of the proposed ZVT cell. A 2-kW laboratory prototype of the boost converter with the proposed ZVT cell operating at 100 kHz is built and tested to verify the theoretical analysis. Finally, a comparative analysis is given to demonstrate the superiority of the proposed converter. [ABSTRACT FROM AUTHOR]

This paper presents a new bridgeless buck–boost power factor corrector with the use of the active virtual ground technique, which is named as the Manitoba Rectifier. The proposed topology can convert the grid ac voltage into a wide range of voltage outputs within a single-stage circuit. It is in a bridgeless structure and simple in design. During the operation, an LC filter is generated at the system input, where continuous grid current is guaranteed in a buck–boost characteristic topology. In addition, the filter capacitor helps to clamp the voltage ripple between the grid and the output bus terminal. Both leakage current and common mode noise are kept in a relatively small value. Thus, a single-stage and low common-mode buck–boost converter system is built. The proposed topology is successfully implemented on an 800 W prototype, and the performance is experimentally verified, which shows good agreement with the theoretical findings. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive analysis of the generation mechanism and suppression methods of common-mode (CM) touch current when employing semiconductor-based galvanic isolation (SGI). SGI achieves galvanic isolation by utilizing semiconductor switches to deliver differential-mode (DM) power during their on states while sustaining CM isolation voltage during their off states. In SGI converters, the touch current (TC) is generated as the switch output capacitance is charged by the CM voltage during each turn-on transient. The TC rises as the switching frequency increases, which limits the system power density. This process is modeled by the proposed high-frequency pulse current model and the low-frequency equivalent resistance-based average model. Passive TC suppression approaches are reviewed, and an active TC compensation method has been proposed. A 2-kW EV battery charger with a GaN-based Totem-pole power factor correction stage and an SGI-based dc/dc stage has been built and tested. The touch current has been effectively reduced by 27 dB. It allows the converter to operate at a higher switching frequency to achieve higher power density while meeting the safety standards’ touch current requirement. [ABSTRACT FROM AUTHOR]

In this paper, a new high voltage gain step-up dc–dc converter is proposed for interfacing renewable power generation. The configuration optimally integrates both the coupled-inductor and switched-capacitor techniques to achieve an ultra-high step-up gain of voltage conversion with low voltage stress and high efficiency. It consists of a voltage boost unit, a passive clamp circuit, and a symmetrical voltage multiplier network. The structure becomes modular and extendable without adding any extra winding for ultra-high step-up voltage gain. The proposed topology not only reduces the voltage stress on the main switch but also maintains it steady for the entire duty cycle range. Furthermore, the reverse recovery issue of the diodes is alleviated through the leakage inductance of the coupled inductor. The operation principle and steady-state analysis are presented in detail. Experimental evaluation validates the claimed advantages and demonstrates a well-distributed efficiency curve and the peak of 96.70%. [ABSTRACT FROM AUTHOR]

Nanosecond pulse discharge plasma has many prospects in industrial applications, and high-voltage repetitive nanosecond pulse generators with compact design and light weight have become one of the key issues limiting its development in some applications. This paper presents a high voltage series-connected silicon carbide (SiC) metal-oxide -semiconductor field effect transistor (MOSFETs) module which can be served as the main switch in a repetitive high-voltage nanosecond pulse generator. This kind of series-connected MOSFETs module with only single external gate driver requiring very few components is very suitable for compact assembly. By analyzing the working principle, three topologies of series-connected MOSFETs module are proposed. The switching behaviors of the three different topologies with four SiC MOSFETs series-connected are compared experimentally. The variation of switching characteristics of series-connection SiC MOSFETs module with different numbers of devices are investigated. The layout is also optimized to shorten pulse front time and improve output pulse quality. Furthermore, a 10 kV SiC MOSFETs module with a turn-on transition time ∼10 ns is developed. The double pulse test result demonstrates excellent switching performances. Finally, a compact and high-voltage pulse generator composed of three 10 kV SiC MOSFETs module is tailored, with a typical rise time ∼40 ns and peak voltage of ∼30 kV. [ABSTRACT FROM AUTHOR]

Reliability of power systems can be improved by the use of voltage source inverters (VSIs) with fast dynamic control, which can handle uncertainties induced by renewable energy resources and nonlinear loads. To ensure fast-dynamic response and simplified controller design, various model predictive control (MPC) methods are investigated in this paper. In the conventional MPC design for three-level VSIs, the cost function requires an additional term to ensure the balance of the neutral-point voltage (NP-V), which however can considerably impact the main goal of the MPC. To address this issue, an enhanced MPC using virtual space vectors is proposed, which allows the use of a significantly reduced weighting factor for the term in the cost function for NP-V balancing, while retaining fast-dynamic response. Additionally, the proposed MPC leads to reduced harmonic distortion in the VSI output voltage and current. Both simulation and controller hardware-in-the-loop studies are performed to demonstrate the effectiveness of the proposed enhanced MPC in an operating microgrid under both steady-state and fast-transient conditions. [ABSTRACT FROM AUTHOR]

The three-level full-bridge (TLFB) dc−dc converter has been widely used in high-voltage, high-power applications. In the experimental test, the neutral-point voltage deviation appears; moreover, it has also been found out that if the flying capacitors are introduced, the input capacitor voltages could realize self-balance even if no active balancing solutions are adopted. In the previous publications, the role of flying capacitors is generally considered to extend the range of soft switching; however, the self-balance ability has not been mentioned or investigated in any publications thus far. In order to fill this gap, this paper provides the detailed mode operation analysis of the TLFB converter and reveals the cause of the imbalance. In addition, the mechanism of the self-balance ability provided by the flying capacitors is explained in detail, which gives a deep insight into the converter. At last, the influence factor of the voltage error in steady state has been analyzed, and the specific expression of the voltage error is also derived. The feasibility of the theoretical analysis is verified by the simulation and experimental results. [ABSTRACT FROM AUTHOR]

Without active control, the voltage fluctuations of the dc-link and flying capacitors in a 4-level hybrid-clamped converter (4L-HCC) become excessively large in low-frequency operation. This paper studies the switching state redundancy inherent in a 4L-HCC and proposes a new capacitor voltage balancing and stabilizing method to minimize the dc-link and flying capacitor voltage fluctuations. A straightforward algorithm is developed based on a logic table to select the suitable switching states. Verified by simulation and experimental testing results, the new method and algorithm virtually eliminate all the big voltage fluctuations of capacitors at low and zero frequencies, greatly enhancing the robustness and reliability of a 4L-HCC. The capacitor size can be reduced by more than 80% compared with the conventional method. [ABSTRACT FROM AUTHOR]

Despite several studies and approaches, the design of current controllers for grid-connected converters via LCL filters is still a challenging task. This is mainly due to the parametric uncertainties and the grid background voltage distortions to which the system is submitted. In order to overcome these inherent system challenges, this paper proposes a multiloop control framework that simplifies the system dynamics of the overall circuit by splitting it in two equivalent sub-circuits. An inner loop is implemented as a fast sliding mode controller that controls the filter capacitor voltage in a fast and robust way. As a result, the plant, viewed by the outer loop, yields a voltage-controlled voltage source connected to the grid through an L filter. Thus, multiple resonant controllers are included in the state-space representation of this simplified system, allowing the design of a state-feedback controller in the outer loop for asymptotic tracking of the grid current with disturbance rejection of the grid background voltage. Here, a discrete linear quadratic regulator algorithm is used for designing the state-feedback gains. A simple design procedure is presented, as well as simulations and experimental results, to show the good performance of the proposed control scheme even under significant uncertainties and disturbances of the system. [ABSTRACT FROM AUTHOR]

A novel PWM full bridge (FB) dc–dc converter for large power industrial applications is proposed in this paper. The soft switching mode of the primary switches can be varied under different input and output conditions to achieve optimum system efficiency. In the zero-voltage and zero-current switching (ZVZCS) mode, the turn-on and turn-off switching loss can be optimized because the soft switching conditions of the turn-on and turn-off instants are well decoupled. In the zero-voltage switching (ZVS) mode, the turn-off switching loss can also be optimized because there is no requirement for light load operation in this mode. Four mosfets with ultra-low on-state resistance are used, thus, the added conduction loss is small. The auxiliary mosfets with high switching frequency are turned on with zero-current and off with zero-voltage, hence, the added switching loss can also be neglected. Furthermore, some drawbacks of the conventional ZVS and ZVZCS converters, e.g., narrow ZVS load range, high primary circulating current, incomplete reset of the primary current, and unreasonable VA rating of the added components, have been well solved. The operation principles and soft switching characteristics are discussed. Experimental results from an 18-kW prototype are provided to verify the proposed converter. [ABSTRACT FROM AUTHOR]