Novel zero-voltage-transition PWM multiphase converters

Novel zero-voltage-transition (ZVT) pulse-width-modulation (PWM) multiphase converters are presented. To construct a ZVT multiphase converter in a conventional way, it is necessary to add the auxiliary circuits with as many number of phases. In the proposed converter, only one auxiliary circuit provides the zero-voltage switching (ZVS) for main switches and diodes of all phases. So, the new converters are cost effective and attractive for high-performance and high power-density conversion applications. Operation, features, and characteristics of the two-phase buck converter are illustrated and verified on a 4-kW 100-kHz insulated gate bipolar transistor (IGBT)-based (a MOSFET for the auxiliary switch) experimental circuit     

Design and analysis of a novel zero-voltage-transition interleaved boost converter for renewable power applications

High-efficiency stepping up operation is an important feature of the converters used in renewable power applications due to the low voltage level of photo-voltaic arrays and fuel cells. Decreasing the switching losses of the converters is an effective solution for increasing the converter efficiency, especially in high-power applications. This article presents a novel zero-voltage-transition (ZVT) interleaved dc–dc boost converter that can be used in renewable power sources to reduce switching losses. The auxiliary circuit used in the proposed converter is composed of only one auxiliary switch and a minimum number of passive components without an important increase in the cost and complexity. The main advantage of the proposed converter is that it not only provides ZVT in the boost switches but also provides soft switching in the auxiliary switch. Another advantage of the proposed topology is that the semiconductor devices used in the converter do not have any additional voltage or current stresses. Also, it has a simple structure, low cost and ease of control. In this article, a detailed steady-state analysis of the proposed converter is presented. The theoretical analysis is verified via simulation and experimental studies which are in very good agreement.     

A novel zero-current-transition full bridge DC/DC converter

This paper proposes a novel zero-current-transition pulse-width modulation full-bridge dc/dc converter. The proposed converter not only achieves zero current switching for the main switches and auxiliary switch in the entire load ranges, but it also realizes soft commutation for the output rectifier diodes. Furthermore, the auxiliary circuit also helps to turn on the main switches softly. Simulation results and experimental results verify the theoretical analysis.     

Integrated Cuk-forward converter for photovoltaic-based LED lighting

An integrated Cuk-forward converter for a photovoltaic (PV)-based light emitting diodes (LED) lighting system is presented. In this converter, the Cuk converter delivers the solar energy via PV cell modules to a battery bank in charging mode during the daytime. However, the zero voltage switching (ZVS) forward converter drives the LED lighting system in discharging mode during the night time. Power switches in the Cuk converter and ZVS forward converter are integrated to reduce the component count and the synchronous switch is used in the circuit to reduce the conduction losses and increase the circuit efficiency. Thus, the advantages of the proposed converter are smaller size, lighter weight, fewer components and higher efficiency. Experimental results based on the laboratory prototype rated at 200 W are presented to verify the effectiveness of the proposed converter.     

Novel zero-voltage-transition current-fed full-bridge PWM converterfor single-stage power factor correction

A novel zero-voltage-transition (ZVT) current-fed full-bridge pulsewidth modulation (PWM) power converter for single-stage power factor correction (PFC) is presented to improve the performance of the previously presented ZVT converter. A simple auxiliary circuit which includes only one active switch provides a zero-voltage-switching (ZVS) condition to all semiconductor devices (two active switches are required for the previous ZVT converter). This leads to reduced cost and a simplified control circuit compared to the previous ZVT converter. The ZVS is achieved for wide line and load ranges with minimum device voltage and current stresses. Operation principle, control strategy and features of the proposed power converter are presented and verified by the experimental results from a 1.5 kW 100 kHz laboratory prototype     

A New PWM-Controlled Quasi-Resonant Converter for a High Efficiency PDP Sustaining Power Module

A new pulsewidth modulation (PWM)-controlled quasi-resonant converter for a high-efficiency plasma display panel (PDP) sustaining power module is proposed in this paper. The load regulation of the proposed converter can be achieved by controlling the ripple of the resonant voltage across the primary resonant capacitor with a bidirectional auxiliary circuit, while the main switches are operating at a fixed duty ratio and fixed switching frequency. Hence, the waveforms of the currents can be expected to be optimized from the view-point of conduction loss. Furthermore, the proposed converter has good zero-voltage switching (ZVS) capability, simple control circuits, no hign-voltage ringing problem of rectifier diodes, no dc offset of the magnetizing current and low-voltage stresses of power switches. Thus, the proposed converter shows higher efficiency than that of a half-bridge LLC resonant converter under light load condition. Although it shows the lower efficiency at heavy load, because of the increased power loss in auxiliary circuit, it still shows the high efficiency around 94%. In this paper, operational principles, features of the proposed converter, and analysis and design considerations are presented. Experimental results demonstrate that the output voltage can be controlled well by the auxiliary circuit using the PWM method.      

A Soft-Switching Scheme for an Isolated DC/DC Converter With Pulsating DC Output for a Three-Phase High-Frequency-Link PWM Converter

This paper outlines a soft-switching mechanism based on zero-voltage-zero-current-switching (ZVZCS) principle for the front-end isolated dc/dc converter of an isolated three-phase rectifier-type high-frequency-link bidirectional power converter. In conjunction with a back-end dc/ac converter operating with a novel patent-filed hybrid modulation scheme outlined in , , and that reduces the number of hard-switched commutation per switching cycle, the proposed ZVZCS scheme can lead to less overall switching losses than other conventional switching schemes. The proposed ZVZCS scheme is effective for various load conditions, operates seamlessly with a simple active-clamp circuit, and is suitable for applications where low-voltage dc to high-voltage three-phase ac power conversion is required.      

A simple active auxiliary commutation circuit for three-level PWMsingle-phase inverters

This paper presents the analysis and design of a new low-loss auxiliary circuit for three-level pulsewidth-modulation single-phase full-bridge inverters which achieve soft switching at all semiconductor devices. The active auxiliary commutation circuit (AACC) is composed of an LC circuit and two bidirectional switches, where one auxiliary switch commutates under zero-voltage switching condition and the other under zero-current switching condition. The AACC dispenses with the use of auxiliary voltage sources. Low reactive energy is added to the converter, resulting in low RMS current stresses at the main switches and, consequently, higher efficiency is achieved. Auxiliary circuit design procedures and experimental results are presented to prove the operation principle     

A Novel Soft-Commutating Isolated Boost Full-Bridge ZVS-PWM DC–DC Converter for Bidirectional High Power Applications

A soft-commutating method and control scheme for an isolated boost full bridge converter is proposed in this paper to implement dual operation of the well-known soft-switching full bridge dc/dc buck converter for bidirectional high power applications. It provides a unique commutation logic to minimize a mismatch between current in the current-fed inductor and current in the leakage inductance of the transformer when commutation takes place, significantly reducing the power rating for a voltage clamping snubber and enabling use of a simple passive clamped snubber. To minimize the mismatch, the method and control scheme utilizes the resonant tank and freewheeling path in the existing full bridge inverter at the voltage-fed side to preset the current in the leakage inductance of the transformer in a resonant manner. Zero-voltage-switching is also achieved for all the switches at the voltage-fed side inverter in boost mode operation. The proposed soft-commutating method is verified through boost mode operation of a 3-kW bidirectional isolated full bridge dc/dc converter developed for fuel cell electric vehicle applications. The tested result verified the isolated boost converter can operate at an input voltage of 8.5–15V and an output voltage of 250–420V with a peak efficiency of 93% and an average efficiency of 88% at 55-kHz switching frequency with 72$^circ$C automotive coolant.     

A New Simplified Multilevel Inverter Topology for DC–AC Conversion

Multilevel converters offer high power capability, associated with lower output harmonics and lower commutation losses. Their main disadvantage is their complexity, requiring a great number of power devices and passive components, and a rather complex control circuitry. This work reports a new multilevel inverter topology using an H-bridge output stage with a bidirectional auxiliary switch. The new topology produces a significant reduction in the number of power devices and capacitors required to implement a multilevel output. The new topology is used in the design of a five-level inverter; only five controlled switches, eight diodes, and two capacitors are required to implement the five-level inverter using the proposed topology. The new topology achieves a 37.5% reduction in the number of main power switches required (five in the new against eight in any of the other three configurations) and uses no more diodes or capacitors that the second best topology in the literature, the Asymmetric Cascade configuration. Additionally, the dedicated modulator circuit required for multilevel inverter operation is implemented using a FPGA circuit, reducing overall system cost and complexity. Theoretical predictions are validated using simulation in SPICE, and satisfactory circuit operation is proved with experimental tests performed on a laboratory prototype.     

A Novel Control Technique for a Switched-Capacitor-Converter-Based Hybrid Electric Vehicle Energy Storage System

This paper presents the analysis and novel controller design for a hybrid switched-capacitor bidirectional dc/dc converter. Features of voltage step-down, step-up, and bidirectional power flow are integrated into a single circuit. The novel control strategy enables simpler dynamics compared to a standard buck converter with an input filter, good regulation capability, low electromagnetic interference, lower source current ripple, ease of control, and continuous input current waveform in both modes of operation (buck and boost modes).      

有源箝位软开关充电机的设计与仿真研究

传统硬开关电路影响效率和可靠性的同时,对其他设备的电磁干扰也较大,软开关则可解决上述问题。本文提出了一种基于辅助谐振换流的新型ZVT-PWM变换器,即通过采用简单的有源辅助谐振网络实现了主、辅开关管的软开关,主开关管实现了零电压开通,开关管电流电压应力小。利用这种软开关技术研制了一台用于为风力发电蓄电池充电的充电机,给出了充电机的控制系统框图,简单介绍了充电机的工作原理。最后利用Pspice给出了运行波形和仿真结果。     

A Bidirectional DC–DC Converter for an Energy Storage System With Galvanic Isolation

This paper addresses a bidirectional dc-dc converter suitable for an energy storage system with an additional function of galvanic isolation. An energy storage device such as an electric double layer capacitor is directly connected to a dc side of the dc-dc converter without any chopper circuit. Nevertheless, the dc-dc converter can continue operating when the voltage across the energy storage device drops along with its discharge. Theoretical calculation and experimental measurement reveal that power loss and peak current impose limitations on a permissible dc-voltage range. This information may be useful in design of the dc-dc converter. Experimental results verify proper charging and discharging operation obtained from a 200-V, 2.6-kJ laboratory model of the energy storage system. Moreover, the dc-dc converter can charge the capacitor bank from zero to the rated voltage without any external precharging circuit.     

Implementation of a Highly Reliable Hybrid Electric Scooter Drive

In contrast to hybrid electric cars (HECs), the issues concerning cost, volume, and reliability are even more rigorous when developing hybrid electric scooters (HESs). Therefore, the drive topology and control strategy used in HEC cannot be applied to HES directly. This paper presents a single-stage bidirectional dc/ac converter based on a general full-bridge inverter. The converter is designed for a low-voltage brushless dc motor/alternator (BLDCM/A) used in HESs, in which the additional bulky inductor and power switches are eliminated in the proposed design. In order to increase the reliability of the commutation process, a cost-effective sensorless control scheme for the motor and alternator commutation is developed. The commutation signals are extracted directly from the average terminal voltages, in which the motor neutral voltage, multistage analog Alters, analog-to-digital converters, and the complex digital phase-shift (delay) circuits are eliminated. In addition, instead of using the complex flux- weakening control technique, the winding-changeover technique is exploited to extend the range of the operating speed. With attractive features, such as low cost and ease of implementation, the proposed approach is particularly suitable for electric bikes, electric scooters, HESs, etc. Theoretical analysis and several experiments are conducted to justify the effectiveness of the proposed method.     

Self-commutated auxiliary circuit ZVT PWM converters

This paper introduces a novel class of zero voltage transition (ZVT) DC/DC pulse-width modulation (PWM) converters that use a resonant inductance-capacitance (L-C) circuit connected to the auxiliary switch, which is termed a self-commutated auxiliary circuit. It provides a simple and reliable means of achieving zero-current conditions (ZCS) for auxiliary switch commutations under wide line and load ranges, without the inclusion of any kind of DC voltage source. Furthermore, this auxiliary circuit is placed in parallel with the main power converter, retaining the ZVT characteristics. The self-commutated auxiliary circuit ZVT PWM boost is analyzed, and its feasibility and reliability are confirmed by experimental results obtained from laboratory prototypes rated at 1 kW and 100 kHz.     

IBC Using a Single Resonant Inductor for High-Power Applications

In this paper, an interleaved boost converter (IBC) with a zero-voltage-transition (ZVT) cell using a single resonant inductor in continuous conduction mode is proposed. The IBC with the proposed ZVT cell has advantages such as a simple circuit, reduced size, and low cost by using a single resonant inductor. It is more suitable for high-power applications. The proposed ZVT cell circuit and principles for the IBC are explained in detail. The validity of the IBC with the proposed ZVT cell is verified through experimental results.     

A bidirectional DC-DC converter for fuel cell electric vehicle driving system

This paper presents a power converter for a fuel cell electric vehicle driving system. A new bidirectional, isolated topology is proposed in consideration of the differing fuel cell characteristics from traditional chemical-power battery and safety requirements. The studied converter has the advantages of high efficiency, simple circuit, and low cost. The detailed design and operating principles are analyzed and described. The simulation and experimental waveforms for the proposed converter are shown to verify its feasibility.     

A simplified three-phase zero-current-transition inverter with three auxiliary switches

Most existing three-phase soft-switching inverters with fewer than six auxiliary switches have fundamental drawbacks in performance. There exist a few soft-switching inverters with six auxiliary switches that can potentially achieve desirable performance, but are penalized with the high cost and large size associated with the auxiliary switches. This paper proposes a zero-current-transition (ZCT) inverter topology that requires only three auxiliary switches. Each phase of the proposed circuit employs one auxiliary switch and one LC resonant tank to assist switching transitions. With considerable reduction in device count, cost, and size, the proposed topology realizes zero-current turn-off for all main switches and auxiliary switches, and provides soft commutation for all diodes. Meanwhile, it requires no modification to normal pulsewidth modulated (PWM) algorithms. The operation principles, design and control guidelines, and an analysis using the state-plane technique are presented. Based on the proposed topology, a 50-kW three-phase prototype inverter has been developed for electric vehicle propulsions, and tested to the full power level with a closed-loop induction motor drive system. Experimental results on the 50-kW prototype are provided to verify the proposed concept in high-power AC adjustable speed drive applications.     

无源器件辅助换流的单相全桥软开关逆变器

为提高单相全桥逆变器的转换效率,提出了一种无源器件辅助换流的单相全桥软开关逆变器拓扑结构,通过在逆变器桥臂上增加辅助谐振电路,实现了开关器件的软开关动作.辅助谐振电路中无辅助开关器件,只含有电感、电容和二极管等少量无源器件,这有利于降低辅助电路的成本,而且不会使逆变器的控制策略复杂化.此外,在逆变器处于死区状态时,负载电流能通过辅助谐振电路续流,可以改善逆变器输出电流波形的畸变率,减小了死区的不利影响.文中详细分析了电路的工作过程,在功率为4kW的单相实验样机上进行了实验验证,获得的实验结果表明在轻载和满载时逆变器的开关器件都能实现软开关,逆变器输出电流波形的畸变率都得到了改善.因此,该无源器件辅助换流的单相全桥软开关拓扑结构对于提高逆变器的性能具有重要意义.     

A new ZVT-ZCT-PWM DC-DC converter

In this paper, a new active snubber cell is proposed to contrive a new family of pulse width modulated (PWM) converters. This snubber cell provides zero voltage transition (ZVT) turn on and zero current transition (ZCT) turn off together for the main switch of a converter. Also, the snubber cell is implemented by using only one quasi resonant circuit without an important increase in the cost and complexity of the converter. New ZVT-ZCT-PWM converter equipped with the proposed snubber cell provides most the desirable features of both ZVT and ZCT converters presented previously, and overcomes most the drawbacks of these converters. Subsequently, the new converter can operate with soft switching successfully at very wide line and load ranges and at considerably high frequencies. Moreover, all semiconductor devices operate under soft switching, the main devices do not have any additional voltage and current stresses, and the stresses on the auxiliary devices are at low levels. Also, the new converter has a simple structure, low cost and ease of control. In this study, a detailed steady state analysis of the new converter is presented, and this theoretical analysis is verified exactly by a prototype of a 1-kW and 100-kHz boost converter.