Zero-voltage-switching For Switches Research Articles

Comparative analysis of three‐phase dual active bridge converter with different transformer topology and modern universal control for DC microgrids

AbstractThe presented work discusses issues related to the use of modern multiphase topologies of Dual Active Bridge (DAB)‐type converters. Converters of this type are widely used in most DC microgrid applications. The introduction emphasizes a comparative analysis between single‐phase and multi‐phase DAB topologies within high‐power DC microgrids, delving into their respective advantages, drawbacks, design procedures, and considerations based on the latest knowledge. The publication explores the comparison and selection of viable topologies for deployment in high‐power and high‐efficiency DC microgrids. The unified method of controlling 1‐phase and multi‐phase DAB converters was proposed in this design, simplifying the issues of DC microgrid control. All topologies were tested on the same controller concept. The study performs laboratory investigation of DAB 1‐phase and 3‐phase: Star–Star, and Star–Delta topologies. Attention was paid to maintaining uniform operating conditions of the system, contrary to studies known from the literature, all tests were carried out on the same laboratory stand and the same magnetic components in different configurations. Analytical and laboratory analyses of the Zero Voltage Switching (ZVS) region were performed, accounting for non‐linear phenomena. Based on these findings, an assessment of the system's performance in soft switching was carried out. The presented results were implemented in a simulation model and subsequently validated through tests on a constructed laboratory setup to ensure the proper operation of the system. This work meticulously presents and discusses variations in efficiency, dynamic response, phase current harmonic distribution, phase shift distribution, ZVS switching region, and more among the examined topologies. To ensure a fair comparison, the converter configuration for both simulation and laboratory models utilized identical components across all configurations.

A Novel ZVS/ZCS Push-Pull LC Resonant DC-DC Converter for Energy Sources

In this paper, a novel soft switching push-pull LC resonant DC-DC converter for energy sources is presented. In a high step-up converter, the input of primary side possesses low voltage and high current, so the losses caused by the current account for most of the total power loss. At the same time, the high-voltage stress of the high-voltage output components on the secondary side is also a major problem. Therefore, a high-gain isolated push-pull converter with a secondary-side resonant circuit is proposed, so that the primary-side switches have zero voltage switching (ZVS) and the secondary-side diodes have zero current switching (ZCS). The push-pull structure can reduce the number of active switches, so that the total power loss on the primary side can be reduced. The converter has a resonant tank circuit arranged between the secondary side of isolation transformer and the high-voltage output rectification module. The high-voltage output rectifier module adopts a full-bridge architecture suitable for high-voltage coupling connection. The low-side power switching module adopts a push-pull architecture suitable for low-voltage and high-current applications. The resonant tank circuit uses an inductor–capacitor (LC) structure to improve the resonant tank circuit, which achieves soft switching during power transfer, increasing the efficiency of the converter and improving the electromagnetic compatibility. The main advantage of this technology is that the secondary-side leakage inductance of transformer and the resonant capacitance are connected in series to achieve ZVS for switches and ZCS for diodes. Finally, a prototype of a high-gain push-pull resonant converter was established. The converter was operated at a fixed switching frequency of 135 kHz and a duty cycle of approximately 0.5. The efficiency of the converter can reach 97.1% under experimental tests at an output voltage of 400 V and a rated output power of 500 W.

1 kV, 10-kW SiC-Based Quadruple Active Bridge DCX Stage in a DC to Three-Phase AC Module for Medium-Voltage Grid Integration

Interfacing low voltage dc to medium voltage three-phase ac grid is often based on series-stackable modular converter architectures. To minimize energy storage requirements, it is advantageous to employ a quadruple active bridge (QAB) stage operating as a “dc transformer” in each stackable module. The QAB stage offers three isolated dc link voltages, which then allow for flexible stacking of three single-phase dc-to-ac inverter stages. Each of the module phases processes a pulsating power having a component at twice the line frequency. This presents a challenge in maintaining zero voltage switching (ZVS) on the secondary sides of the QAB during low-power portions of the line cycle. This article is focused on the design of the QAB stage. A detailed analysis of ZVS switching waveforms is presented, including effects of nonlinear device capacitances. It is shown how ZVS can be achieved at all times using a relatively small circulating current provided by the magnetizing inductance of the high-frequency transformer. Analytical expressions are given for the optimal values of the magnetizing inductance and the dead times of the QAB primary and secondary bridges. The approach is verified by experimental results on a 1 kV, 10-kW SiC-based prototype, demonstrating a relatively flat efficiency curve with a peak efficiency of 97.1% at 75% load.

Triple Phase Shift Control of Wireless Charging DAB LCC Resonant Converter for Unity Power Factor Operation with Optimized Rectifier AC Load Resistance

This paper presents a new triple phase shift (TPS) closed-loop control scheme of a dual active bridge (DAB) LCC resonant DC/DC converter to improve wireless charging power transfer efficiency. The primary side inverter phase shift angle regulates the battery charging current/voltage. The secondary side rectifier phase shift angle regulates the rectifier AC load resistance to match its optimized setting. The inverter-to-rectifier phase shift angle is set to achieve unity power factor operation of the DAB rectifier and inverter. The mathematical formulation of the TPS shift control is given for each phase shift angle. The analytical calculation, circuit simulation, and experimental test are carried out in a power scaled-down DAB LCC resonant wireless charging converter laboratory hardware setup to validate the proposed TPS close-loop control scheme. The PLECS circuit simulation shows that DAB LCC resonant SiC MOSFET operates at zero-voltage-switching (ZVS) with a unity power factor in emulated constant current (CC) mode battery charging. In constant voltage (CV) mode operation, one inverter/rectifier Leg does not operate at ZVS switching when Sic MOSFET is switched on near zero current. The experimental results show that the efficiency is greatly improved for CV mode charging with large DC load resistance connected if rectifier AC load resistance matching control is enabled. The measured efficiency matches well with the analytical calculation. The estimated efficiency improvement will be much more significant for EV applications in the kW power range with greater winding loss. The challenges and possible solutions to implement TPS PWM modulation in two separate inverter and rectifier control hardware are explained for future TPS control algorithm development in practical wireless charging products.

Power-Estimation-Based Synchronous Rectification Solution for Bidirectional DAB-LLC Converter

An LLC-DAB bidirectional converter with reduced switch count as a DC-DC transformer (DCX) is proposed in this paper. It can achieve voltage regulation, full load range zero voltage switching (ZVS) for eight main switches and wide load range ZVS for four auxiliary switches, with consideration of the switch junction capacitors under different power direction. A part portion of total power is transferred through an auxiliary DAB circuit to achieve voltage regulation and bidirectional power conversion. The main power is transferred through LLC circuit with an easy PWM scheme achieving high conversion efficiency. Different from the existing LLC-DAB DCX structure, the two secondary side transformer outputs are in parallel, and connected to the same full-bridge circuit. In this way, the auxiliary DAB circuit can not only adjust the output voltage, but also can inject current into the secondary side to help achieving ZVS of switches without synchronous rectifier (SR) circuit. The converter operation principle is analyzed under different power directions, and ZVS is analyzed with the consideration of all the switch junction capacitors. Based on the analysis, the design consideration is introduced. Finally, a 2-kW prototype with 750V input and 400V output is built up to verify the effectiveness of the proposed solution.

An LLC-DAB Bidirectional DCX Converter With Wide Load Range ZVS and Reduced Switch Count

An LLC dual active bridge (DAB) bidirectional converter with reduced switch count as a dc–dc transformer (DCX) is proposed in this article. It can achieve voltage regulation, full load range zero voltage switching (ZVS) for eight main switches and wide load range ZVS for four auxiliary switches, with consideration of the switch junction capacitors under different power direction. A part portion of total power is transferred through an auxiliary DAB circuit to achieve voltage regulation and bidirectional power conversion. The main power is transferred through LLC circuit with an easy PWM scheme achieving high conversion efficiency. Different from the existing LLC -DAB DCX structure, the two secondary side transformer outputs are in parallel, and connected to the same full-bridge circuit. In this way, the auxiliary DAB circuit can not only adjust the output voltage, but also can inject current into the secondary side to help achieving ZVS of switches without synchronous rectifier circuit. The converter operation principle is analyzed under different power directions, and ZVS is analyzed with the consideration of all the switch junction capacitors. Based on the analysis, the design consideration is introduced. Finally, a 2-kW prototype with 750 V input and 400 V output is built up to verify the effectiveness of the proposed solution.

Improved Control Strategy of Triple-Voltage Three-Phase DAB (T2-DAB) Converter for Current Stress and Zero-Voltage-Switching Optimization

Three-phase triple-voltage dual-active-bridge (T <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> -DAB) converter possesses high input voltage and large output current capacity, which can be adopted to constitute a high-power-density dc transformer. However, when employing conventional phase-shifted (PS) control strategy, zero-voltage switching (ZVS) turn-on is easily lost under light-load and voltage-mismatching situations. Hence, this article presents an optimized asymmetrical duty-cycle modulation strategy for T <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> -DAB converter, ensuring ZVS for switches and reducing the current stress over wide power and voltage ranges. The detailed model is established with a time-domain analysis method, and ZVS constraints are given with the particular consideration of dead time and parasitic capacitances of switches. Then, the MATLAB optimization toolbox is adopted to calculate the optimum duty cycle and PS angle, and the specific control scheme is introduced. Finally, a 2-kW prototype is built to verify the theoretical analysis, whose input voltage ranges from 480 to 720 V and output voltage is 200 V. The experimental results show that the proposed optimized control scheme can realize ZVS turn-on for all switches over wide voltage and power ranges, and the efficiency is improved, especially under light-load and voltage-mismatching situation.

An Optimized Zero-Current, Zero-Voltage, and Three-Level DC–DC Converter

In this article, an optimized zero-voltage and zero-current pulsewidth modulation converter is proposed by investigating conventional converters widely used in dc grids. In this presented model, instead of using three-phase power switches, single-power switches are employed since single-power MOSFETs and IGBTs have lower switching loss and simpler drive circuit than the other module series. Therefore, the converter size and its power loss will decrease compared with the models with three-phase components. In addition, soft switching is utilized in the proposed converter to decrease the total power loss and increase efficiency accordingly. Also, for optimum use of zero-voltage switching (ZVS) and zero-current switching (ZCS), a new combination of IGBT and MOSFET is presented in the converter's circuit. Considering low turn-off loss for IGBT and low capacitive loss for MOSFET, IGBT and MOSFET are taken for ZVS switching and ZCS switching, respectively. In addition, a simple stabilizer circuit is added to the output part to improve the operation of the output filter since the filter plays an essential role in dc-dc converters. Finally, simulation of the proposed model is implemented in the PLECS software, and the results confirm the proper application of ZVS and ZCS, converter high efficiency, and high stability at the output voltage.

Deadband Effect and Accurate ZVS Boundaries of GaN-Based Dual-Active-Bridge Converters With Multiple-Phase-Shift Control

Gallium nitride (GaN) high-electron-mobility transistors (HEMTs) are promising for the next-generation power switching applications due to their low on-resistance, high-frequency operation, and small gate capacitances, which are essential for the power density and efficiency improvement. However, with the increase of the switching frequency, the deadband effect will become a challenging issue for the high-efficiency converter design over a wide operation range. In this article, a comprehensive theoretical analysis and experimental verification of the deadband effect in the GaN-based dual-active-bridge (DAB) converters with multiple-phase-shift (MPS) control is presented. First, resonant transitions for various switching conditions with different initial currents by using MPS controls are discussed, and the effect of the stray capacitance of GaN HEMTs is analyzed. On this basis, the accurate boundaries among zero-voltage switching (ZVS), partial ZVS, and hard switching with MPS control can be obtained. A deadband compensation strategy is proposed by considering different switching conditions. Finally, a DAB prototype based on GaN HEMTs was built, and main experimental results were provided to verify the effectiveness of the proposed resonant transition analysis, ZVS boundaries, and the deadband compensation strategy.

ZVS Buck-Boost LLC cascade converter with all soft switched switches

ABSTRACTA Buck-Boost LLC cascade converter is proposed in this paper. In virtue of the Zero-Voltage-Switching (ZVS) modulation strategy for Buck-Boost circuit, all the switches can be soft switched with wide conversion range and full load range. By sharing one of the two bridge legs, the magnetizing current needed to realize the ZVS of switches decreases. Then, the power density and efficiency of the proposed converter increase. Theoretical analysis and characteristics of the proposed converter are presented and verified on a 210 V–400 V input 12 V/400 W output experimental prototype. The experimental results show that the proposed converter can achieve a peak efficiency of 95.6% at 1 MHz. The power density of the proposed converter is as high as 414 W/in3 with the help of GaN transistors and planar transformers.

Hardware Implementation of GaN-HEMT Based ZVS DC–DC Converter Considering PCB Layout

The gallium nitride high electron mobility transistors (GaN HEMT) are among the most promising power semiconductor devices. However, these transistors have a small gate voltage margin compared with conventional power devices. In this paper, the gate voltage of GaN HEMTs is mathematically analyzed when it is applied to a zero voltage switching (ZVS) phase-shift full bridge (PSFB) DC–DC converter. The analysis accounts for nonlinear capacitance characteristics under the ZVS switching condition, and a critical parasitic inductance are derived to restrict the gate voltage to a safety operation area. The optimal layout for bridge topologies and gate drivers is proposed, to satisfy the derived parasitic inductance limitation. A 500-W-power laboratory phase-shift full-bridge DC–DC converter is implemented to verify the proposed layout.

High-Efficiency Zero-Voltage Switching Single-Stage Switching Amplifier With Half-Bridge Active Clamping Circuit

A zero-voltage switching (ZVS) single-stage switching amplifier (SSA) is proposed in this paper. The proposed SSA is composed of a bipolar phase shift modulation (BPSM) high-frequency link single-stage inverter and a half-bridge active clamp (HBAC) circuit. HBAC circuit is developed to clamp the voltages across cycloconverter switches and to recycle the energy in filter inductor and leakage inductance. ZVS of cycloconverter switches can be realized with the help of active clamp circuit. By utilization of magnetizing current, wide range ZVS of primary-side switches can be achieved. By delaying the turn on time of clamp switches to primary-side switches, full range ZVS of active clamp switches can be realized. High efficiency of the proposed HBAC-SSA is achieved with single-stage power conversion, recycling of inductive energy, and wide range ZVS. Benefiting with BPSM and voltage clamp across cycloconverter switches, low distortion of output voltage is also obtained. A 120 W prototype with 93.6% peak efficiency and 0.07% total harmonics distortion has been built to verify the analysis results of the proposed HBAC-SSA.

A Control Strategy for Bidirectional Isolated 3-Phase Current-Fed Dual Active Bridge Converter

This paper examines the characteristics of the zero voltage switching (ZVS) and zero voltage transition (ZVT) soft-switching applied in the 3-phase current fed dual active bridge (3P-CFDAB) converter, which combines the advantages of the dual active bridge (DAB) converter and current-fed full bridge (CFFB) converter. When an active clamp circuit is added to the CFFB converter, the circuit configuration of the DAB converter is shown in part of the entire circuit. This allows the use of pulse width modulation (PWM) techniques which combine the PWM techniques of both the DAB converter and CFFB converter. The proposed converter performs both duty and phase control at the same time in order to reduce the circulating current and ripple current of the output capacitor, which are the disadvantages of the CFFB converter and DAB converter. In addition, the ZVS and ZVT soft switching areas were analyzed by means of the phase current and leakage inductor current in each transformers. To verify the principle and feasibility of the proposed operation techniques, a simulation and experiment were implemented with the 3P-CFDAB.

Implementation of an Active-Clamped Current-Fed Push–Pull Converter Employing Parallel-Inductor to Extend ZVS Range for Fuel Cell Application

This paper proposes a wide-range zero-voltage-switching (ZVS) active-clamped current-fed push–pull converter for fuel cell application. The presented converter achieves ZVS for all of the primary switches and ZCS for secondary diodes from rated load to 10% full load over the wide input voltage variation, improving the overall efficiency. The ZVS of switches is realized by the energy stored in the transformer leakage inductance aided by the secondary parallel inductor. An additional active clamping circuit suppresses the voltage spike as well as assists in realizing ZVS of switches. Low-voltage-rated switches with low on-state resistance can be used. Moreover, the voltage-doubler rectifier is adopted to release the reverse-recovery problem of rectifier diodes and reduce turns ratio of the high-frequency transformer. Detailed steady-state operation, analysis, design, control, comparative study, and experimental results are discussed in depth in this paper. Finally, a 200-W prototype has been built in the laboratory to verify the effectiveness of the proposed converter.

Dynamic and Performance Analysis of Distributed Hybrid Photovoltaic (PV) and Fuel Cell based Power Generation using Adaptive Neuro Fuzzy Inference System (ANFIS)

This paper proposes the dynamic modeling and performance analysis for distributed hybrid power generation. Intelligent modeling of two diode PV/PEMFC systems should provide stable and continuous power to the electrical vehicle. The transformer isolated full bridge converter is proposed to improve the generated Photovoltaic power. The full bridge converter integrates with PV model and achieves Single stage power conversion between sources to dc link. Additionally; high power density, primary switching ZVS (Zero Voltage Switching) and high efficiency have been achieved. The main study of PV two diode modeling is used to reduce computational time and neglecting the series and shunt resistances, also provide more efficient power depends upon irradiance, temperature, shading effects etc. PEMFC is connected to dc-bus via a Cuk converter. In Cuk converter the source and dc link are separated by a dc link capacitor thus energy transferred from the source to load side occurs through this capacitor which has reduce the lode side ripple current. However the additional fuel cell topology promoted to overcome the other energy requirement and reduce the conversion cost. The Adaptive Neuro Fuzzy Inference System (ANFIS) based controller used for the control purpose of DC-DC power conversion. Therefore, the proposed PV/PEMFC models are verified under MATLAB/SIMULINK environment; as the result efficiency increases compared with the conventional system.

An Improved Zero Voltage Transition PWM Boost Converter with an Active Snubber Cell

This study presents an improved zero voltage switching (ZVS) boost converter with an active snubber cell providing soft switched operation for all semiconductors. The active snubber cell reduces the reverse recovery loss of the boost diode and also provides the zero voltage transition (ZVT) Turn-on and ZVS Turn-off for the boost switch. The zero current switching (ZCS) Turn-on and ZVS Turn-off for the snubber switch is also achieved. All diodes in the converter can be operated with soft switching (SS). In the snubber cell, SS energy can be transfered effectively to the output by the use of a snubber inductor and a capacitor. This energy transfer allows the use of additional parallel connected capacitor to the boost switch to provide ZVS turning off. There is no additional voltage and current stress on the boost switch and boost diode. The voltage stress of the snubber switch is also limited by the output voltage and the current stress of the snubber switch is reduced by the energy transfer to the output. SS operating of the semiconductors is maintained at very wide load ranges. The operation of the proposed converter is presented with a detailed steady state analysis. The predicted theoretical analysis is validated by a prototype with 500[Formula: see text]W output power and 100[Formula: see text]kHz operating frequency. The measured maximum efficiency values are obtained as approximately 97% and 85.4% at full load and 10% load conditions, respectively.

Zero‐voltage‐switching buck converter with low‐voltage stress using coupled inductor

This study presents a new zero-voltage-switching (ZVS) buck converter. The proposed converter utilises a coupled inductor to implement the output filter inductor as well as the auxiliary inductor which is commonly employed to realise ZVS for switches. Additional magnetic core for the auxiliary inductor in traditional ZVS converters is eliminated and hence reduced cost is achieved. Moreover, thanks to the series connection between the input and output, the switch voltage stress in the steady state is reduced and thus the ZVS operation can be easier achieved. Then the leakage inductor current circulating in the auxiliary switch is decreased, contributing to reduced conduction losses. In particular, low-voltage rating devices with low on-state resistance can be adopted to further improve efficiency in applications with non-zero output voltage all the time, such as the battery charger. Furthermore, the reverse-recovery problem of the diode is significantly alleviated by the leakage inductor of coupled inductor. In the study, operation principle and steady-state analysis of the proposed converter are presented in detail. Meanwhile, design considerations are given to obtain circuit parameters. Finally, simulations and experiments on a 200 W prototype circuit validate the advantages and effectiveness of the proposed converter.

Current‐tripler‐rectifier pulse width modulation ZVS three‐phase full‐bridge DC/DC converter with Y–Δ connected transformer

To decrease the current stress of the switches in high power applications, a current-tripler-rectifier zero voltage switching (ZVS) three-phase full-bridge DC/DC converter with pulse width modulation (PWM) control strategy is proposed in this study. The converter utilises a three-phase full-bridge structure at the primary side and a current-tripler rectifier at the secondary side. The converter applies to situations involving high power, high input voltage and large output current. The three-phase interleaved structure not only decreases the current stress of the switches, but also increases the frequency of input and output current ripple to three times as large as the switching frequency, which reduces the filter inductance. All switches achieve ZVS with the proper PWM control strategy. It is quite easy to achieve ZVS for lower switches of the bridge leg since the energy coming from the output filter inductor discharges the junction capacitors. Since the energy of upper switches achieving ZVS comes from the leakage inductors of two phase transformers, it is easier to achieve ZVS for upper switches of this converter than lagging-leg switches of the phase-shifted full-bridge converter. A prototype with 360 V input and 48/42 A output was built in the lab and experimental results verified the theoretical analysis.

Input-Series-Output-Parallel Phase-Shift Full-Bridge Derived DC–DC Converters With Auxiliary LC Networks to Achieve Wide Zero-Voltage Switching Range

This letter proposes an input-series-output-parallel derived dc-dc converter composed of two phase-shift full-bridge (PSFB) dc-dc converters and two auxiliary LC networks. Each LC network is connected between the leading-leg midpoint of a module and the lagging-leg midpoint of the other one. For conventional PSFB converters, the lagging-leg switches may lose zero-voltage switching (ZVS) conditions at light loads. In the proposed converter, ZVS for lagging-leg switches can be achieved with the aid of the LC networks even at light loads. The efficiency of the converter at the light load is improved. Therefore, the proposed converter is suitable for the wide load range. The feature of the converter is analyzed. The performance of the proposed converter is verified by a 900 W experimental prototype.

Analysis, Design, and Implementation of the Class-E ZVS Power Amplifier With MOSFET Nonlinear Drain-to-Source Parasitic Capacitance at any Grading Coefficient

In this paper, analytical expressions for waveforms and design relationships are derived for the class-E power amplifier with the MOSFET nonlinear drain-to-source parasitic capacitance under the subnominal operation, i.e., only zero-voltage switching (ZVS) condition, for any grading coefficient m of the MOSFET body junction diode and 50% duty ratio. Only the MOSFET nonlinear drain-to-source parasitic capacitance is used for the analysis of the class-E ZVS power amplifier, and its nonlinearity is determined by the grading coefficient m. The switch voltage waveform does not satisfy the class-E ZVS switching condition when only the linear shunt capacitance is considered. The grading coefficient m is used as an adjustment parameter that provides accurate design to satisfy the given output power and peak switch voltage simultaneously. Therefore, the grading coefficient m is the important parameter to satisfy the class-E ZVS condition and given design specifications, which is the most important result in this paper. Additionally, the output power capability and maximum operating frequency are affected by the grading coefficient m. The analytical expressions are obtained by considering the grading coefficient m as an adjustment parameter, which is validated by PSpice simulations and laboratory experiments. The measurement and PSpice simulation results agreed with the analytical expressions quantitatively, which denotes the usefulness and effectiveness of our obtained analytical expressions.