LLC resonant DC–DC converter with series‐connected primary windings of transformer

This paper proposes a zero‐voltage switching (ZVS) LLC resonant step up DC–DC converter with series‐connected primary windings of the transformer. The series resonant inverter in the proposed topology has two power switches (MOSFETs), two resonant capacitors, two resonant inductors, and only one transformer with center‐tapped primary windings. The power switches are connected in the form of a half‐bridge network. Resonant capacitors and inductors along with the primary windings of the transformer form two series resonant circuits. The series resonant circuits are fed alternately by operating the power switches with an interleaved half switching cycle. The secondary winding of transformer is connected to a bridge rectifier circuit to rectify the output voltage. The converter operates within a narrow frequency range below the resonance frequency to achieve ZVS, and its output power is regulated by pulse frequency modulation. The converter has lower conduction and switching losses and therefore higher efficiency. The experimental results of a 500‐W prototype of proposed converter are presented. The results confirm the good operation and performance of the converter. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Dual voltage converter with improved power factor and enabling voltage control

In this paper, a novel version of the dual voltage converter is presented with improved voltage regulation and enabling a wide range of voltage control by using self-turn-off devices (power transistors) instead of diodes. Further, this system operates with unity displacement factor. We have obtained the analytical expressions of this circuit. The results are, however, quite complex. We could calculate values of the voltage and current waveforms by using a computer. The calculated values are essentially in agreement with the experimental values. Experimentally, an ideal load characteristic with null voltage regulation was obtained by the conduction angle control for power transistors. Further, a wide range of voltage from 220 V to 39 V was obtained. A disadvantage for this system is the requirement for snubber circuits with a larger value of capacitor in order to suppress the surge voltages at turn-off periods.     

矩阵变换器双电压合成策略的非线性补偿法

为减少矩阵变换器因换流的延时、开关管的导通压降对输入、输出性能的影响,基于双电压合成调制策略,对四步换流的死区效应、管压降形成的机理进行了定量分析,得出了一种非线性补偿方法。该方法根据双电压合成策略由输入电压瞬时值合成输出电压的特点,将管压降产生的电压误差考虑到理想参考输出电压中得到新的参考输出电压,补偿因换流的延时引起输出电压误差所需的调制时间,并在dSPACE硬件实时仿真平台进行了实验验证。结果表明,该非线性补偿方法不仅不需增加硬件及复杂的软件,简单易行,且减少了输出电流的谐波,改善了矩阵变换器的输出性能。     

Series resonant high‐voltage DC–DC converter with reduced component count

This paper proposes a novel zero‐current‐switching series resonant high‐voltage DC–DC converter with reduced component count. The series resonant inverter in the proposed topology has two power switches (insulated‐gate bipolar transistors, IGBTs), two resonant capacitors, and only one high‐voltage transformer (HVT) with center‐tapped primary windings. The power switches are connected in the form of a half‐bridge network. The leakage inductances of the transformer's primary windings together with the resonant capacitors form two series resonant circuits. The series resonant circuits are fed alternately by operating the power switches with interleaved half switching cycle. The secondary winding of the HVT is connected to a bridge rectifier circuit to rectify the secondary voltage. The converter operates in the discontinuous conduction mode (DCM) and its output voltage is regulated by pulse frequency modulation. Therefore, all the power switches turn on and off at the zero‐current switching condition. The main features of the proposed converter are its lower core loss, lower cost, and smaller size compared to previously proposed double series resonant high voltage DC–DC converters. The experimental results of a 130‐W prototype of the proposed converter are presented. The results confirm the excellent operation and performance of the converter. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

电容补偿在配电网电压调节中的应用

针对某些配电网负荷电压水平不满足要求和电压波动较大的问题,提出基于串联电容补偿的配电网负荷电压调节与稳定方法.通过在配电线路上串入可调电容,根据电容电压损耗与线路原电感电压损耗极性相反的特征,在负荷波动的情况下利用电容电压抵偿线路电感电压即可调节和稳定负荷侧电压.通过实时采样负荷功率,计算补偿电路的晶闸管触发角,调节电...     

智能TSC低压动态无功补偿控制器设计

介绍了一种以单片机87C196KC为主处理器的TSC型低压动态无功补偿控制器,并给出了实验结果。控制器采用改进的“九域图法”控制策略,避免了投切振荡。通过对三相电压、电流信号的一个周期进行等间隔采样,并对采样数据进行快速傅里叶变换处理(FFT),得到各有关电量参数,实现无功补偿和电网监测功能。     

0．4kV低压电网无功补偿方式探讨

介绍了低压电网的无功补偿方式,主要有线路补偿和终端补偿方式。并讨论了电容器的容量计算及最优容量的选择依据,最后对如何评估补偿效益作了阐述。     

A pulsed power supply with sag compensation using controlled gradational voltage

A pulsed power supply with sag compensation using controlled gradational voltage to increase the flatness of output waveforms has been developed. The sag compensation circuit consists of compensation units connected in series. Each compensation unit consists of capacitances, diodes, and semiconductor switches. The capacitances of each unit are charged with different voltages by 2ⁿ(V₀,2V₀,4V₀,…). The compensation voltage, which has 2ⁿ?1 steps, is generated by switching the semiconductor switches of each unit in a binary sequence. Using this method, compensation voltage waveforms up to 6.2 kV with 31 steps can be obtained with five compensation units. The sag compensation circuit has been adapted to a direct switch‐type pulsed power supply, which generates 7 kV pulsed voltage with a pulse width of 700µs, thus realizing sag compensation. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 150(4): 54–63, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20017     

电压调节和无功补偿技术在城市配电网中的降损作用

结合揭阳老市区10kV配电网络的实际，着重阐述电压调节和无功补偿在城市配电网改造中节能降损的重要作用，提出配电网调节和无功补偿的方法，并指出当前城网改造中应大力应用电压调节和无功补偿技术。     

级联H桥型变流器直流电压均衡控制

在分析变流器直流电容充放电状态和功率器件开关状态之间关系的基础上,提出了一种改进的适用于整流、无功补偿、谐波电流抑制等场合的级联H桥型变流器直流电压均衡控制方法。根据变流器交流侧能量传递方向合理地选择开关函数,调整变流器各个直流电容充放电状态,实现直流电压的均衡控制。调节均衡控制周期,可以改变直流电压均衡速率,调整均衡算法对开关频率的影响。基于MATLAB/Simulink的仿真结果表明了所提直流电压均衡控制方法的有效性。     

Implementation of parallel zero‐voltage switching converter with series‐connected transformers

This paper presents a parallel zero‐voltage switching (ZVS) DC–DC converter with series‐connected transformers. In order to increase output power, two transformers connected in series are used in the proposed converter. Two buck‐type converters connected in parallel have the same switching devices. The primary windings of series‐connected transformers can achieve the balanced secondary winding currents. The current doubler rectifiers with ripple current cancellation are connected in parallel at the output side to reduce the current stress of the secondary winding. Thus, the current ripple on the output capacitor is reduced, and the size of the output choke and output capacitor are reduced. Only two switches are used in the proposed circuit instead of four switches in the conventional parallel ZVS converter to achieve ZVS and output current sharing. Therefore, the proposed converter has less power switches. The ZVS turn‐on is implemented during the commutation stage of two complementary switches such that the switching losses and thermal stresses on the semiconductors are reduced. Experimental results for a 528‐W (48 V/11 A) prototype are presented to prove the theoretical analysis and circuit performance. Copyright © 2011 John Wiley & Sons, Ltd.     

并联型有源电力滤波器直流侧电压控制策略的研究

在研究了PI控制方法控制方法的基础上,提出了对有源电力滤波器直流侧电压实现模糊递推PI控制的方法,设计了模糊控制规则,详细介绍了模糊递推PI控制方法的控制原理,并且针对PI控制方法和模糊递推PI控制方法采用Matlab/Simunlink仿真软件对直流侧电压进行仿真分析。仿真结果表明,模糊递推PI控制方法在系统稳定以及负载突变时比PI控制方法能够更加有效地消除稳态误差,使有源电力滤波器直流侧电压实现精确跟踪,从而提高滤波器的滤波效果。     

双绕组反激式单级PFC变换器及功率因数改善措施研究

为改善功率变换器的功率因数,提出一种双绕组反激式单级功率因数校正PFC(Power Factor Correction)变换拓扑。该拓扑由Boost PFC电路和具有串并联结构的双绕组反激变换电路组合而成,利用2个中间储能电容吸收变压器初级绕组的漏感能量,有效地抑制功率器件的电压应力,提高变换器的可靠性。详细分析了变换器的工作原理和稳态特性,并在传统的单电压环控制方法的基础上,将整流电压引入到控制电路,提出了一种简单的电压补偿控制方法来提高变换器的功率因数、降低输入电流的总谐波畸变率。设计制作了一台150 W/24 V实验样机,实验结果验证了所提出电路原理的正确性和采用电压补偿控制方法改善输入电流波形质量的有效性。     

A novel method of suppressing the inrush current of transformers by using a series‐connected voltage‐source PWM converter

This paper proposes a novel method of suppressing the inrush current of transformers. A small‐rated voltage‐source PWM converter is connected in series to the transformers through a matching transformer. As the connected PWM converter serves as a resistor for the source current, no inrush phenomena occurs. The required rating of the PWM converter, which serves as the damping resistor for the inrush phenomena, is 1/400 that of the main transformers in single‐phase circuits. In three‐phase circuits, it is 1/900. The basic principle of the proposed method is discussed. Digital computer simulation is implemented to confirm the validity and excellent practicability of the proposed method using the PSCAD/EMTDC. A prototype experimental model is constructed and tested. The experimental results demonstrate that the proposed method can perfectly suppress the inrush phenomena. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(4): 56–65, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20174     

混合变压器式可控电抗器及其仿真

为满足谐波要求,传统的变压器式可调电抗器(ControllableShuntReactorofTransformerType, CSRT)在轻载时存在一段不可调的死区。针对这一缺点,提出了混合变压器式可控电抗器(HybridCSRT, HCSRT),它采用电压源型逆变器代替了CSRT中的反并联晶闸管来控制调节绕组的输出,通过合理设置各控制绕组的容量,N个控制绕组的HCSRT可以实现2N级分级平滑调节。在此基础上,进一步提出了同时具有容性和感性无功补偿能力的混合变压器式静止无功补偿器。理论分析和数字仿真表明     

电力电缆护层电压补偿装置研究

电力电缆线路改造时容易造成换位的电缆三段不等长,从而引起护层电压不平衡,产生护层环流。在对电缆护层电压理论分析的基础上,推导了电缆几种主要排列方式下的护层感应电压数学模型;提出了电缆护层电压的补偿方法。该方法是在电缆终端增加一补偿电感,即在铁芯上绕制线圈,此线圈一端接电缆金属护层末端,另一端接地,基于这一补偿方法开发了补偿装置计算的软件包,并进行仿真计算,在此基础上研制了补偿装置。通过改变该补偿装置的气隙和匝数,可以对电缆护层电压进行有效补偿,使补偿后电缆护层的总电压大为减小,有效地抑制了护层环流,可大幅度降低电缆损耗,提高电缆传输容量。     

新型串联高电压补偿系统在中卫电网的应用

为解决110 kV电网重负荷、长距离输电带来的负荷末端电压质量问题,对影响电压质量的主要原因进行分析,提出在中卫电网110 kV新-海线海原变电站侧线路上加装高压新型串联电压补偿系统的解决方案。应用结果表明:线路电压降导致的用户受端电压质量不合格和重负载启停时造成的电压波动问题得以根除,为宁夏高压电网、超高压电网、乃至特高压电网电压补偿系统的合理布局和优化调度奠定了基础。     

级联式并联有源电力滤波器的控制

本文提出了一种新的级联式并联有源电力滤波器(CSAPF)的控制算法.传统的两电平拓扑结构的有源滤波器由于其功率开关耐压水平的限制,难以实现对高压大容量非线性负载的谐波补偿.在高压大容量传动系统中,H桥级联式逆变器得到了广泛的应用.然而,这种逆变器独立电容电压的不平衡问题限制了其在有源滤波领域的应用.本文针对这一问题设计了一种新的参考电流提取算法和电容电压平衡PWM算法.实验结果表明了所提出算法的正确性和有效性.     

并联型APF直流侧电压的滑模PI控制策略研究

并联有源滤波器(shunt active power filter, SAPF)在主动配电网系统中应用日益广泛,提升SAPF的补偿性能成为众多学者关注和研究的热点。对直流侧电压精准稳定控制是保证SAPF补偿性能的关键。采用传统PI控制系统在非线性负载突变和电压跳变时无法对直流侧电压进行快速稳定控制,为改善直流侧电压的控制性能,提出电压外环滑模变结构PI复合控制器。仿真与实验结果表明:滑模PI复合控制器提高了直流电压控制的稳态精度和响应速度,降低了直流电压波动对SAPF补偿性能的影响。     

不平衡电压下双馈感应发电机转子侧变流器的灵活功率控制

针对不平衡电压下双馈感应发电机(DFIG)转子侧变流器的控制,分析定子瞬时有功和无功功率与三相定子电压、转子电流的关系,通过引入连续调节系数得到转子三相电流指令值的通用计算式。进一步地,求得指令电流调节系数、转子电流峰值及DFIG定子有功和无功波动的表达式,分析DFIG控制特性随调节系数、电压不平衡度的变化规律;分析不平衡电压跌落下DFIG的可控性,给出电压跌落后定子电压的临界值和转子侧变流器可控的判断条件;以功率波动设定值为目标,计及转子电流峰值限制,建立DFIG单位功率因数和无功功率支持2种模式下的灵活功率控制策略,通过仿真验证所提方法的可行性。