Soft-switching Implementation Research Articles

On‐board charger applications: A new hybrid control strategy for bidirectional CLLC resonant converter

AbstractThis paper proposes a new hybrid control strategy to solve the problem of bidirectional wide voltage range regulation in CLLC converters. On the (LLC) side (G2V direction), the SSSA control method is employed for voltage boost, combined with bus voltage and burst control to achieve wide voltage regulation. On the (C) side (V2G direction), the SSSA and full/half‐bridge mode switching control are used to achieve V2G direction wide voltage regulation. This hybrid control strategy also enables high conversion efficiency in both directions without the need for additional components to reduce the converter power density. This is particularly suitable for OBC applications with strict requirements for converter volume and weight. A detailed analysis with mathematical derivation, hybrid control strategy, and converter operation principles is introduced in this paper. The following subchapters supplement the converter voltage gain, soft switching implementation conditions, and design considerations. Finally, the feasibility of the proposed control strategy was verified through an experimental prototype with an input voltage ranging from 340 to 430 V to an output voltage ranging from 225 to 450 V and bidirectional rated power of 6.6/3.3 kW. This prototype achieved a maximum conversion efficiency of 97.7% in the G2V direction and 97.1% in the V2G direction.

An Improved Zero-Voltage and Zero-Current- Switching Phase-Shift Full-Bridge PWM Converter With Low Output Current Ripple

In order to improve the performance of traditional phase-shifted full-bridge converters and reduce the output current ripple, an improved zero voltage and zero current switching phase-shifted full-bridge PWM converter is proposed in this article. By adding a simple auxiliary circuit, the leading-leg switches realize zero voltage switching and the lagging-leg switches realize zero current switching. The primary current is reset during the freewheeling period, so the efficiency of the converter is improved. What is more, the improved converter can effectively reduce the output current ripple. The added auxiliary circuit does not include any lossy components or saturable reactors. The improved phase-shifted full-bridge converter has many advantages, including simple circuit topology, easy implementation of soft switching, high efficiency, and low output current ripple. The operational principle and analysis of the proposed converter are presented in this article. An 800 W experimental prototype is built for experimental verification.

A Synchronous Auxiliary Resonant Commutated Pole Soft-Switching Inverter With Improved Load Adaptability

To realize a soft-switching inverter with small volume and high efficiency, a synchronous auxiliary resonant commutated pole (SARCP) soft-switching inverter with improved load adaptability is proposed, which only contains two auxiliary inductors. In one switching cycle, all commutation processes can be synchronously assisted by an auxiliary inductor. Soft switching is achievable for all switches of the SARCP inverter. Compared with the auxiliary resonant commutated pole (ARCP) inverter, the SARCP inverter has improved load adaptability, especially in the light load current condition, which is beneficial to reduce the total power loss and the dc-link capacitance. The equivalent circuits of the SARCP inverter are given under different operation modes. The operation principle, soft-switching implementation conditions, parameter optimization design methods, and the characteristics of the SARCP inverter are analyzed. Finally, simulation and experimental results verify the effectiveness of the SARCP inverter.

Analysis and Implementation of Inverter Wide-Range Soft Switching in WPT System Based on Class E Inverter

This article addresses the problem of hard switching caused by the change of equivalent load in a wireless power transfer (WPT) system based on a class E inverter. Based on the load-sensitive characteristics of the class E inverter, the coil structure is improved, and the self/mutual inductance compensation method of the transmitting coil is proposed to realize a wide range of soft switching. On the basis of fully considering the coupling relationship between the source and load coils, a coil structure with multiple coils in series on the primary side is proposed, and the cross-coupling relationship between the coils is analyzed in detail and simplified. The inverter parameters and coupling mechanism were adjusted by means of coil series reverse connection. Combined with the parameter influence law and the load equivalent principle of the class E inverter, the margin of soft switching at the inverter side was increased and the load offset correction was carried out. The soft-switching effect of the equivalent load from 0 to 3.3 times of ideal load was obtained, and the purpose of improving system reliability and efficiency was achieved. Finally, the feasibility and effectiveness of the proposed method were verified by simulation and experiment.

Current Stress Optimisation Strategy for Three-phase Dual Active Bridge Converter during the Start-Up Process

Three-phase dual active bridge (3p-DAB) converter is widely used in high-power bidirectional power transfer applications, due to its unique high power density and easy implementation of soft switching. In this paper, the start-up process of the 3p-DAB converter is studied. The cause of high current stress, especially in the case of heavy-load start-up is analysed, and a new start-up control strategy for the start-up process is proposed. The control strategy is helpful to reduce the current stress of the transformer and the switches by adjusting the duty-cycle and the phase shift angle coordinately without adding any other hardware circuits. Finally, based on a TMS320F28377D + XC6SLX25 controller, a 30kW 3p-DAB converter prototype with input voltage 650-750V and output voltage 400-500V is developed to verify the effectiveness of the proposed start-up strategy.

An Improved Pulse Density Modulation of High-Frequency Inverter in ICPT System

Pulse density modulation (PDM) is often applied in inductively coupled power transfer (ICPT) systems to improve high-frequency inverter (HFI) efficiency. However, the PDM may cause the inverter output current fluctuation, even interruption for light load or low-quality factor system. This may result in the difficulty for the implementation of soft switching in ICPT. In this article, an improved PDM (IPDM) strategy is proposed by optimizing the distribution of switch sequences. Through the current fluctuation numerical analysis and Fourier decomposition, IPDM can reduce the current fluctuation and improve the system efficiency. The experimental results on a 20 kW ICPT system prototype show that the proposed IPDM strategy reduces the HFI output current ripple coefficient is 40% to 65% lower than PDM, and the efficiency is also improved.

A Design Method to Implement ZVS for Electric Vehicle Wireless Charging System With Double-Side LCC Compensation

In this article, the zero voltage switching (ZVS) of the inverter in the electric vehicle wireless charging system is realized through the parameter optimization design of compensation components, which is conducive to the high efficient operation of the system. The effects of the parameter adjustment of each compensation component on the input impedance angle and output current of the double-side LCC compensation topology were analyzed under the conditions of different output voltages and coupling coefficients, which provides a basis for the component optimization design of the inverter ZVS realization. The quantitative relationship between the optimized component parameter and the soft switching implementation conditions was analyzed. Then, a specific parameter design method was proposed, according to the results analyzed earlier. At last, the effectiveness of the proposed method was verified by a 3.3-kW wireless charging system prototype. Experimental results show that the optimized system is always able to achieve soft switching, the system efficiency is up to 95.2% at the rated power, and it is higher than 93% even under the condition where the coupling coefficient and output voltage are both reduced by half.

A Soft-Switching Synchronous Rectification Noninverting Buck–Boost Converter With a New Auxiliary Circuit

In this article, a new soft-switching auxiliary circuit structure for the synchronous rectification noninverting buck-boost converter (NIBBC) is proposed. This new auxiliary circuit, which contains a fully coupled inductor (or a transformer), a snubber inductor, a capacitor, and a power diode, will provide zero voltage switching (ZVS) turn-ON conditions for all power transistors of the proposed NIBBC. In addition, waveform ripples in the auxiliary circuit of the output side are reduced, and then the output current ripple is also reduced. Meanwhile, the current across the main inductor is not affected by the auxiliary circuit. In order to analyze the proposed NIBBC, operating principles, soft-switching implementation conditions, and main characteristics of the proposed NIBBC are presented in this article. Finally through building a 400-W experimental prototype, key waveforms and measuring efficiency curves are obtained. Experiment result shows that all transistors of the new NIBBC operate under ZVS conditions. The efficiency of the proposed NIBBC is improved by comparing to the triangular current mode soft-switching NIBBC.

Modified Double Auxiliary Resonant Commutated Pole Inverter and its Modulation Strategy

In order to overcome the complexity of the double auxiliary commutation circuit (DACC) and the coupling of the resonance process of the double auxiliary resonant commutated pole (DARCP) inverter, a modified DARCP inverter topology and its modulation strategy are proposed. The modified topology not only retains the advantage of reliable zero voltage switching (ZVS) turn-off of auxiliary switches and so on, but also realizes the simplification of the DACC and the decoupling of the resonance process. The cost of the inverter and the system oscillation caused by coupling resonance are reduced, and the performance and practicability of the inverter are improved. According to the equivalent circuits of different operation modes under the proposed modulation strategy, the operation principle, the soft-switching implementation condition, and the parameter design method are analyzed. Finally, a 10-kW, 16-kHz soft-switching inverter prototype is built. Experimental results are given to demonstrate the validity of the proposed inverter.

Conduction Loss Analysis According to Variation of Resonant Parameters in a Zero-Current Switching Boost Converter

In this paper, conduction loss analysis of a zero-current switching (ZCS) boost converter with variations of the resonant parameters in the auxiliary circuit is performed. Generally, the auxiliary circuit for soft switching of the main device generates additional losses. An improperly designed auxiliary circuit part cannot improve the efficiency of the overall system and, even make it worse. For this reason, an auxiliary resonant circuit should be designed based on the selected parameters through accurate and detailed analysis. First, a design procedure considering practical aspects to implement ZCS is proposed in this paper. Equations associated with additional conduction losses caused by resonant parameters are proposed through a mathematical analysis. The conduction losses at various design values of the resonance parameters are calculated and compared through the proposed equations. To verify the proposed analysis, the experimental results about additional conduction loss analysis with the variations in the resonant parameters of the auxiliary circuit for soft switching implementation are provided.

Design of ZVS DC/DC converter based on DSP2812 phase-shifted full bridge

The phase-shifted full-bridge DC/DC converter is a very important component of power electronics and is suitable for medium and large power output applications based on switching power supplies. Aiming at the implementation of soft-switching and the problem of power loss, this paper firstly describes the structure and working mode of DC/DC converter, then analyzes the calculation and selection process of resonant inductance and capacitance parameters in the converter, and finally adopts the traditional PI control to achieve stable control of the output voltage. The simulation and experimental results fully prove the feasibility and rationality of the design and parameter selection of this scheme.

Resonant Inductance Design and Loss Analysis of a Novel Resonant DC Link Inverter

To realize a soft-switching inverter with the advantages of a simple structure, high efficiency, low-voltage stress, and easy to control, a novel parallel resonant dc-link inverter with the function of pulse current regeneration is proposed in this paper. All switches in the inverter main circuit can achieve zero-voltage switching (ZVS) turn- on and ZVS turn- off . In addition, all switches in the auxiliary commutation circuit (ACC) can achieve soft switching. The power in the ACC is small. Freewheeling diodes in the inverter turn off under zero current condition, which can reduce the reverse recovery loss of freewheeling diodes. In addition, the bulk capacitors are avoided in the circuit and there is no neutral point potential variation problem. At the same time, the zero-voltage duration is independent of the load current, and the time of transition can be selected freely. According to the equivalent circuits in different operation modes under the proposed modulation strategy, the operation principle, soft-switching implementation condition, and parameter design procedure of the proposed inverter are analyzed successively in this paper. Finally, a 10 kW, 10 kHz soft-switching inverter prototype with insulated gate bipolar transistor based switches is built. Experimental results are given to demonstrate the validity and features of the soft-switching inverter.

Parallel Resonant DC Link Inverter Topology and Analysis of Its Operation Principle

To realize a soft-switching inverter with the advantages of simple structure, high efficiency, low voltage stress, and easy to control, a novel parallel resonant dc link inverter with the function of pulse current regeneration is proposed in this paper. All switches in the inverter main circuit can achieve zero-voltage-switching (ZVS) turn-on and ZVS turn-off. All switches in the auxiliary commutation circuit (ACC) can achieve soft-switching. The power in the ACC is small. Freewheeling diodes in the inverter turn off under the zero-current condition, which can reduce the reverse recovery loss of freewheeling diodes. In addition, the bulk capacitors are avoided in the circuit and there is no neutral point potential variation problem. At the same time, the zero-voltage duration is independent of the load current, and the time of transition can be selected freely. According to the equivalent circuits in different operation modes under the proposed modulation strategy, the operation principle, soft-switching implementation condition, and parameter design procedure of the proposed inverter are analyzed successively in this paper. Finally, a 10-kW–10-kHz soft-switching inverter prototype with insulated gate bipolar transistor (IGBT)-based switches is built. Experimental results are given to demonstrate the validity and features of the soft-switching inverter.

Comprehensive Review and Comparison of Single-Phase Grid-Tied Photovoltaic Microinverters

The power processing and the presence of the electrical isolation between the PV module and the grid is a very crucial aspect in determining the performance requirement, as well as the utility operator’s specifications for the PV microinverter design. The grid-connected PV microinverter design can be classified into four categories: 1) nonisolated single-stage topologies; 2) isolated single-stage topologies; 3) nonisolated double-stage topologies; and 4) isolated double-stage topologies. Typically, a microinverter’s performance can be enhanced by the use of nonisolated topologies to be more efficient, more compact, less bulky, and less costly than the isolated topologies. Whereas, the use of a transformer in microinverter topologies provides high-power quality as well as galvanic isolation to eliminate the safety issues, which in return meet the grid standards. The power processing (boosting the dc voltage of PV panel, extracting the maximum power and converting it to ac power), which can be achieved either via single stage or double stage, has a significant impact on the microinverter performance. This paper reviews and compares experimentally verified microinverter topologies in terms of their corresponding efficiency, power density, reliability, and cost. The most efficient topology in each category is designed and simulated in comparison with a benchmark. The topologies are then compared in terms of their component count, input voltage range, modular structure, soft-switching implementation, and battery integration.

4-level capacitor-clamped boost converter with hard-switching and soft-switching implementations

This paper presents parameters analysis of 4-level capacitor-clamped boost converter with hard-switching and soft-switching implementation. Principally, by considering the selected circuit structure of the 4-level capacitor-clamped boost converter and appropriate pulse width modulation (PWM) switching strategy, the overall converter volume able to be reduced. Specifically, phase-shifted of 120° of each switching signal is applied in the 4-level capacitor-clamped boost converter in order to increase the inductor current ripple frequency, thus the charging and discharging times of the inductor is reduced. Besides, volume of converters is greatly reduced if very high switching frequency is considered. However, it causes increasing of semiconductor losses and consequently the converter efficiency is affected. The results show that the efficiency of 2-level conventional boost converter and 4-level capacitor-clamped boost converter are 98.59% and 97.67%, respectively in hard-switching technique, and 99.31% and 98.15%, respectively in soft-switching technique. Therefore, by applying soft-switching technique, switching loss of the semiconductor devices is greatly minimized although high switching frequency is applied. In this study, passive lossless snubber circuit is selected for the soft-switching implementation in the 4-level capacitor-clamped boost converter. Based on the simulation results, the switching loss is approximately eliminated by applying soft-switching technique compared to the hard-switching technique implementation.

Three‐phase double auxiliary resonant commutated pole inverter topology and analysis of its working principle

This study presents a double auxiliary resonant commutated pole (ARCP) inverter topology and modulation strategy. In the proposed inverter, the zero-voltage-switching (ZVS) turn-off of auxiliary switches influenced by parasitic circuit elements from the wiring process can be avoided. It is assured that the auxiliary switches achieve ZVS turn-off reliably. Hence, the reliability of the ARCP inverter is improved, especially in high-power application. According to the equivalent circuits in different operation modes under the proposed modulation strategy, the working principle, soft-switching implementation condition, and parameter design procedure of the proposed inverter are analysed successively in this study. Finally, a 10 kW, 16 kHz double ARCP inverter prototype is built. Experimental results are given to demonstrate the validity of the proposed inverter.

Research on A Novel Modulation Strategy for Double Auxiliary Resonant Commutated Pole Soft-switching Inverter with the Shunt Dead Time

Aimed at the problem that the auxiliary commutation circuit (ACC) of auxiliary resonant commutated pole (ARCP) inverters has a high loss in commutation processes, this paper presents a novel modulation strategy with shunt dead time based on a double ARCP (DARCP) inverter. In comparison with the original modulation strategy, this modulation strategy cannot only achieve soft switching for all switches, but also avoid the superposition of resonance current and load current at commutation moments in double ACCs (DACCs) and make the maximum current through DACCs approximately equal to load current in commutation processes. So, the circulating current loss in DACCs and the current stress of auxiliary switches can be effectively reduced. According to the equivalent circuits in different operation modes under the novel modulation strategy, this paper analyzes the operation principle, soft-switching implementation condition, and optimal parameter design procedure of the DARCP inverter. Finally, a 10-kW–16-kHz DARCP inverter prototype with insulated gate bipolar transistor-based switches is built. Experimental results are given to demonstrate the validity and features of the DARCP inverter under the novel modulation strategy.

Novel Zero-Voltage and Zero-Current Switching (ZVZCS) PWM Three-Level DC/DC Converter Using Output Coupled Inductor

In this paper, a novel zero-voltage and zero-current switching (ZVZCS) pulsewidth modulation (PWM) half-bridge (HB) three-level (TL) dc/dc converter is proposed. Compared with traditional ZVZCS PWM TL dc/dc converters, this converter does not include auxiliary resonant circuits. It can achieve zero-voltage switching (ZVS) for the leading switches and approximate ZCS for the lagging switches with the aid of the transformer parasitic inductance, snubber capacitors, and tapped-inductor-type smoothing filter. This converter can reduce the voltage and current spikes of the power switches as well as the primary circulating current loss effectively. The operation principle of the novel converter and the soft-switching implementation condition are analyzed according to equivalent circuits under different stages. Besides, the effects of the tapped-inductor turns ratio on the current stress of the power switches and the output voltage characteristic under open-loop control scheme are discussed. The validity and features of the proposed converter are demonstrated by simulation results and experimental results via a 6-40 kHz prototype using the fast switching insulated gate bipolar transistor (IGBT).

Research on a Novel Modulation Strategy for Auxiliary Resonant Commutated Pole Inverter With the Smallest Loss in Auxiliary Commutation Circuits

Aiming at overcoming the problem that the auxiliary commutation circuit (ACC) of auxiliary resonant commutated pole (ARCP) inverters has a high loss in commutation processes, this paper presents a novel modulation strategy based on an improved ARCP inverter. In comparison with the original modulation strategy, this modulation strategy can not only realize soft-switching for all switches, but also avoid the superposition of resonance current and load current at commutation moments in ACCs and make the maximum current through ACCs approximately equal to load current in commutation processes. So the circulating current loss in ACCs and the current peak stress of auxiliary switches can be effectively reduced. According to the equivalent circuit in different operation modes under this modulation strategy, this paper analyses the operation principle, soft-switching implementation condition, and optimal parameter design procedure of the improved ARCP inverter. Finally, the novel modulation strategy is applied to a 10 kW 16 kHz improved ARCP inverter prototype with insulated gate bipolar transistor-based switches. Experimental results are given to demonstrate the validity and features of the inverter under the novel modulation strategy.

Analysis of a Novel Isolated Input-Series and Output-Series Full-Bridge Bidirectional DC/DC Converter

A novel topology of isolated input-series and output-series (ISOS) full-bridge bidirectional DC/DC converter is described in this paper for the application requirement of high input voltage and high output voltage, which can be used in the next generation medium and high voltage power conversion systems. The proposed novel isolated bidirectional DC/DC converter not only can apparently decrease the stress of the switches, but also have the advantages, such as galvanic isolation, ease of realizing soft-switching control, high power density, and so on. In this paper, working principle of the proposed DC/DC converter is discussed in detail, the corresponding equations are derived, and the soft switching implementation is discussed too. In the end, simulation is done through PSIM to certify the feasibility of the proposed DC/DC converter and accuracy of the criterion.