A DC voltage converter with a series resonant inverter and asymmetric control of power transistors

The interest in dc converters with a series resonant inverter (resonant converters) is due to the fact that they easily realize switching of semiconductor devices at zero current and zero voltage in a device. This makes it possible to significantly reduce power losses during switching of semiconductor devices and to realize the operation of a dc–dc converter at higher frequencies with a high efficiency. In the foreign literature, many circuits of resonant converters are described and many results of experimental studies are presented. However, the theory of such converters has not been sufficiently developed and theoretical studies are conducted using approximate methods, for example, fundamental-harmonic method. This paper describes the operating principle of the power part of a dc–dc converter with a series resonant inverter with asymmetric control in the discontinuous conduction mode (DCM), when the switching frequency is less than the resonance frequency of the LC circuit. The features of symmetric and asymmetric control of the inverter’s power transistors are described, in which bipolar current pulses are formed in half of the switching period. An algorithm for asymmetric control of transistors is proposed, and a scheme for implementing this algorithm on discrete components in the form of a virtual model in the Matlab–Simulink environment is presented. The results of modeling (transient and steady-state conditions, external characteristics, and other dependences), as well as the results of a comparison of the taken and theoretical (constructed from analytical relationships) characteristics, are presented.     

Soft‐switching converter with low circulating current and wide range of ZVS turn‐on

In this paper, a new hybrid dc–dc converter with low circulating current within the freewheeling interval, wide range of zero‐voltage switching and reduced output current ripple is presented. The proposed hybrid circuit includes two three‐level pulse‐width modulation converters and a series resonant converter with the shard lagging‐leg switches. Series resonant converter is operated at fixed switching frequency (close to series resonant frequency) to extend the zero‐voltage switching range of lagging‐leg switches. The output of series resonant converter is connected to the secondary sides of three‐level converters to produce a positive rectified voltage instead of zero voltage. Hence, the output inductances can be reduced. The reflected positive voltage is used to decrease the circulating current to zero during the freewheeling interval. Therefore, the circulating current losses in three‐level converters are improved. Finally, experiments are presented for a 1.44 kW prototype circuit converting 800 V input to an output voltage 24 V/60A. Copyright © 2015 John Wiley & Sons, Ltd.     

移相全桥PWM变换器的DCM研究

当输出滤波电感的电流在一个周期内不连续时,移相全桥PWM变换器就工作在电流断续模式(DCM).在该模式下,输出滤波电感两端电压会出现振荡.这种现象不仅会导致次级占空比增加,还会给输出纹波带来不利的影响,在某些应用场合是不允许的.在详细分析该模式下变换器的工作过程和软开关特性的基础上,通过考虑电路各处的分布参数特别是输出滤波电感的寄生参数,很好地解释了振荡现象.利用PSpice仿真研究,总结出电路中各参数,特别是电感寄生参数对谐振过程的影响规律.提出了一种抑制该振荡的方法,最后通过仿真和实验验证了该方法对抑制DCM下电感电压振荡的有效性.     

基于恒频PWM及多谐振技术的桥式ZCS变流器

分析及研究桥式并联谐振开关变流器存在的不足之处，针对开关功率管的导通在较大初始电流下进行，容易产生较大的di／dt导通损耗；控制回路的调节方式通过改变开关频率来实现，不利于整机电路的优化设计等^[1-3]问题。对原有电路拓朴结构提出一系列改进措施，使开关三极管实现了在零电流条件下导通及关断，变流器的控制方式实现了恒频PWM控制方式。     

降低整数阶无线电能传输谐振频率的分数阶方法

针对谐振无线电能传输谐振频率高而电力电子器件目前较难实现高频大功率开关变换器的问题,提出一种基于分数阶原理降低无线电能传输谐振频率的方法,建立SS型分数阶无线电能传输系统的电路模型,推导其输出功率和传输效率的表达式,通过Matlab数值仿真分析分数阶元件的阶数对谐振无线电能传输参数及特性的影响。研究结果表明,采用分数阶电感、电容元件,可以大幅度降低谐振无线电能传输系统的谐振频率,从而降低开关器件的开关频率,且可以输出比整数阶无线电能传输系统更大的功率。     

A single-phase PWM current source type converter coupled with an ac chopper

A current source type converter can easily generate a sinusoidal current on the ac side by employing a PWM strategy. In the converter system for a single-phase supply, however, the dc current pulsates because the dc output voltage of the converter contains an ac component with twice the ac supply frequency. The dc current pulsations cause the ac current waveform to be distorted. Although the use of a dc reactor with large inductance reduces the dc current pulsations, the size and the weight of converter equipment including a dc reactor is large. Two-phase rectification using two full-bridge converters and a converter system with an ac chopper circuit has been proposed for elimination of the dc pulsations. In these converters, the number of switching devices comprising the circuit will unavoidably increase. To solve this problem, we propose a novel single-phase current source type converter coupled with an ac chopper circuit and the PWM method. In this circuit, two switching devices in the main bridge are used to form an ac chopper bridge with two added devices and a capacitor. This paper gives the experimental and theoretical waveforms and the steady-state characteristics. The results prove that a smooth dc current and a sinusoidal ac current are obtained, and that a great reduction of the dc inductance can be achieved by using the proposed converter. © 1998 Scripta Technica. Electr Eng Jpn, 123(3): 36–45, 1998     

Analysis and Experimental Validation of an Interleaved LLC Resonant Converter with Reduced Component Count

This paper presents an interleaved LLC resonant half-bridge DC-DC converter with lesser component count. Unlike most of the conventional interleaved LLC resonant converters, the proposed converter uses only one power transformer having two primary windings and one secondary winding. The primary windings of the transformer are fed in parallel via dual resonant tanks by operating the power switches of half-bridge network with interleaved half-switching cycle. Due to parallel feeding, core magnetization current divides equally between primary windings. Consequently, the effective value of magnetization inductance seen at each primary winding becomes twofold of the measured value. An equivalent circuit of converter is derived to validate this phenomenon. The gain characteristics of the equivalent circuit indicate that the maximum gain of converter occurs at relatively lower switching frequency than the conventional two power transformers-based interleaved LLC converters. Consequently, the proposed converter will have same operational characteristics at half magnetizing inductance. The validity of developed equivalent circuit and operational principle and performance of converter are confirmed by both simulation and experimental results of a 1000-W prototype. The experimental results show that for an input voltage of 400 V, converter has maximum efficiency of 96.24% at output power of 1000 W.     

谐振引起的牵引变电所无功动补投切故障分析

某牵引变电所TCR型动态无功补偿装置在进行设备投运时,发生2次谐波放大现象,导致牵引变电所继电保护装置频繁跳闸.结合SVC投切试验现象,对投切故障进行了分析.在工频频率下,SVC滤波支路的容抗远大于系统感抗.不会产生并联谐振.但对谐波频率而言,系统感抗大幅增加而滤波支路容抗大幅减小.当电力系统短路容量过小时,系统阻抗和...     

用于无刷直流电机驱动的谐振极软开关逆变器

用硬开关逆变器来驱动无刷直流电机会产生逆变器的开关损耗大和运行效率低的问题。为降低开关损耗,提出一种用于无刷直流电机驱动的新型谐振极软开关逆变器的拓扑结构,通过在传统硬开关逆变器的三相输出端添加辅助谐振电路,利用辅助电路中的高频变压器的等效电感与主开关并联的缓冲电容之间的谐振,实现逆变器主开关器件的零电压开关和辅助开关器件的零电流开关。依据不同工作模式下的等效电路图,分析了电路的换流过程和设计规则,并建立起了辅助谐振电路损耗的数学模型,讨论了谐振参数对辅助电路损耗的影响。制作了1台实验样机,实验结果表明逆变器的主开关和辅助开关都实现了软开关。该谐振极软开关逆变器能有效改善效率,降低开关损耗。     

Analysis and improved control method of resonant DC link inverters

High performance power conversion requires high switching frequency power converters. Resonant dc link inverters, which are investigated in this paper, are suitable for this purpose because they cause no switching loss in principle. But in these inverters, loss of the resonant oscillation and occurrence of high peaks in the resonant capacitor voltage are serious problems. In this paper, we investigate a control method for resonant dc link inverters which can overcome these problems. First of all, we summarize the basic control principle of an ideal resonant dc link inverter. Then we present an analyzing method for the practical resonant dc link inverter introducing two equivalent circuits in which the influence of the power losses in the resonant link and in the inverter load is considered. From these equivalent circuits, the problems of existing control methods are clarified. Based on the results of this analysis, we propose an optimum and keep the capacitor voltage at an allowable level. A simple compensation method for the influence of storage time of switching devices, which affects the implementation of the proposed control method, is described. Some experimental results are included to confirm the validity of the analytical results and the effectiveness of the proposed control method.     

一种新颖的耦合电感MVS无源无损缓冲电路

研究了一种适用于大功率Buck变换器的带耦合电感的最小电压应力(Minimun Voltage Stress,简称MVS)无源无损ZCS开通缓冲电路,它利用耦合电感的漏感与谐振电容在功率管开关过程中进行谐振,实现软开关。分析了变换器的工作模态,给出了软开关环节中耦合电感和谐振电容的参数设计方法,并搭建了150 W实验样机。实验结果表明,该结构实现了功率开关管ZCS开通和近似ZVS关断,抑制了功率二极管的反向恢复过程,减小了开关损耗,提高了变换器的效率。     

LLCL滤波的单相光伏并网逆变器控制技术研究

采用新型LLCL滤波器对单相光伏并网逆变器进行滤波,LLCL滤波器通过在传统LCL滤波器的电容支路中串联一个小电感达到在开关频率处产生串联谐振,相比LCL滤波器能够更大程度地对串联谐振频率处的电流谐波进行衰减,可进一步减小总电感值。分析表明LCL滤波器双电流环控制同样适用于LLCL滤波器,并网电流外环采用带谐波补偿的准比例谐振(PR)控制器能够有效跟踪并网电流指令的同时可对特定次谐波进行补偿,但谐振控制器在谐振频率处存在180°相角跳变,随着谐波补偿的次数增加易导致系统不稳定。在准PR控制器之后增加一个超前校正环节,对谐振频率处进行相位补偿的同时能够提高系统的相位裕量,增强系统稳定性。此外,引入电网电压前馈控制增强系统对电网电压的抗干扰能力。仿真结果表明系统具有较好的稳态性能和抗干扰性能。     

一种辅助谐振变换极三相电压型PWM变流器

提出了一种新颖的辅助谐振变换极三相PWM变流器拓扑结构.该拓扑结构较传统辅助谐振变流器简单,控制方便.文章分析了PWM 控制方式、零电压谐振的工作模式,并对谐振电路和谐振条件进行了数学推导.仿真研究结果表明,该变流器在单位功率因数运行的情况下,能够实现零电压开关动作.     

Design of a Pulsewidth-Modulated Resonant Converter for a High-Output-Voltage Power Supply

The design and fabrication of a parallel resonant converter circuit and a high-frequency step-up transformer used to supply an adjustable dc voltage to a load is described. The 500-W system is operated from 115/230 V single-phase 60-Hz power, which is rectified and filtered to form a 310-V dc link. A two-transistor half-bridge circuit operating at a fixed frequency above the circuits resonant frequency converts the dc voltage to an ac voltage at approximately 20 kHz. This high-frequency voltage is transformed with a low-capacitance oil-impregnated ferrite transformer. The output voltage is rectified to form a dc voltage with a maximum value of 90-kV peak. The output voltage is adjustable using pulsewidth modulation of the conduction time of the two transistors in the power circuit. The energy stored in the resonant circuit provides a sinusoidal transformer voltage at fixed frequency over a wide range of control. The system is provided with a closed-loop peak-voltage regulator and an on-off capability from the control electronics. The transformer is designed for a specific value of inductance and capacitance to operate at the desired resonant frequency and characteristic impedance.     

基于LC谐振的叠层母排杂散电感测量的新方法

现有的叠层母排杂散电感测量方法主要是基于电压过冲和关断电流变化率的原理,在精度上存在不足。为此提出了一种基于LC谐振的精确测量方法。测量时需要在IGBT桥臂两端并联吸收电容,并且在桥臂的上管并联一个线性电感器。控制桥臂下管的开关动作,就可以使叠层母排杂散电感和吸收电容构成二阶LC谐振回路。由于谐振周期和吸收电容的电容量都可以精确测量获得,因此可以准确计算得到杂散电感值。用该方法测量H桥逆变器叠层母排的杂散电感,测量结果验证了所提出方法的准确性。     

Hybrid DC–DC converter with high efficiency,wide ZVS range,and less output inductance

In this paper, a new soft switching direct current (DC)–DC converter with low circulating current, wide zero voltage switching range, and reduced output inductor is presented for electric vehicle or plug‐in hybrid electric vehicle battery charger application. The proposed high‐frequency link DC–DC converter includes two resonant circuits and one full‐bridge phase‐shift pulse‐width modulation circuit with shared power switches in leading and lagging legs. Series resonant converters are operated at fixed switching frequency to extend the zero voltage switching range of power switches. Passive snubber circuit using one clamp capacitor and two rectifier diodes at the secondary side is adopted to reduce the primary current of full‐bridge converter to zero during the freewheeling interval. Hence, the circulating current on the primary side is eliminated in the proposed converter. In the same time, the voltage across the output inductor is also decreased so that the output inductance can be reduced compared with the output inductance in conventional full‐bridge converter. Finally, experiments are presented for a 1.33‐kW prototype circuit converting 380 V input to an output voltage of 300–420 V/3.5 A for battery charger applications. Copyright © 2015 John Wiley & Sons, Ltd.     

Analysis and design of a two‐transformer active‐clamping forward converter with parallel‐connected current doubler rectifiers

A new two‐transformer active‐clamping forward converter with parallel‐connected current doubler rectifiers (CDRs) is proposed in this paper. The presented DC–DC converter is mainly composed of two active‐clamping forward converters with secondary CDRs. Only two switches are required and each one is the auxiliary switch for the other. The circuit complexity and cost are thus reduced. The leakage inductance of the transformer or an additional resonant inductance is employed to achieve zero‐voltage‐switching (ZVS) during the dead times. Two CDRs at the secondary side are connected in parallel to reduce the current stresses of the secondary windings and the ripple current at the output side. Accordingly, the smaller output chokes and capacitors decrease the converter volume and increase the power density. Detailed analysis and design of the presented two‐transformer active‐clamping forward converter are described. Experimental results are recorded for a prototype converter with a DC input voltage of 130??180V, an output voltage of 5 V and an output current of 40 A, operating at a switching frequency of 100 kHz. Copyright © 2010 John Wiley & Sons, Ltd.     

输入并联输出串联LCC变换器的设计

LCC串并联谐振变换器较之其他形式的谐振变换器能更有效利用高压变压器的漏感和寄生电容实现软开关,并且能更大范围地调整输出电压,从而更加适用于高压电源.提出了一种输入并联输出串联LCC变换器的设计,分析了软开关实现的条件.所设计的变换器采用了主从控制方法,主模块采用脉冲频率调制,从模块采用脉冲频率调制结合脉冲跨周期调制,...     

Minimization of wiring inductance in high power IGBT inverter

The wiring inductance is one of main causes limiting the use of the inverter in hard commutation mode, particularly when voltage, current and switching frequency are increased. The busbar technology is the means that allows one to reach low wiring inductance between DC source and power switches in spite of relatively long connections. This paper deals with studies of busbar structure applied to the high power inverters in order to improve their performances. Two structures of wiring are tested; the traditional one and busbar technology. Experimental and simulation results show that this last technique permits to obtain very low wiring inductance so that no snubber circuits are needed     

三类高频链AC-AC变换器比较研究

本文对Buck、Boost、Buck-Boost型三类高频链AC-AC变换器的电路结构与拓扑、控制策略、网侧功率因数、负载短路时的可靠性、输出容量、高频变压器磁化状态和原理试验结果等进行了深入的比较研究,获得了重要结论。高频链AC-AC变换器电路结构,是由输入滤波器、储能电感(Boost型)、输入周波变换器、高频变压器或高频储能式变压器、输出周波变换器、输出滤波器依序级联而成。研究结果表明,三类高频链AC-AC变换器具有不同的特点、工程实现难易性和应用场合,为实现新型的正弦交流稳压器、交流调压器、电子变压器和同频波形变换器等奠定了关键技术基础。