Single-Phase SRM Drive With Torque Ripple Reduction and Power Factor Correction

In a single-phase switched reluctance motor (SRM) drive, the dc voltage source is generally supplied by a circuit consisting of a bridge rectifier and a filter capacitor connected to an ac line. The charging time of the capacitor is shorter from the ac source as capacity increases. The bridge rectifier draws pulsating current from the ac source, which results in a degraded power factor (PF) and lower system efficiency. A single-phase SRM drive system is presented in this paper, which includes the realization of a drive circuit for the reduction of torque ripple and PF improvement with a novel switching topology. The proposed drive circuit adds one switch and one diode, which can separate the output of the ac/dc rectifier from the large capacitor and supply power to the SRM alternately. This allows the drive system to realize torque ripple reduction and PF improvement through the switching scheme. The validity of the proposed method is analyzed by mathematical modeling and tested by simulations and experiments.     

Unity-power-factor PWM converter with DC ripple compensation

The generation of harmonics and their subsequent propagation into power lines is a topic of increasing concern to power-supply authorities. To prevent obstacles in the power system, a unity-power-factor PWM converter will be applied at ac-dc power conversion plants. However, the PWM converter, especially at single-phase circuit, has some serious defects, including low-frequency ripple current that flows into the dc line and gives rise to a low-frequency ripple voltage that appears on the dc output. In usual cases, it is necessary to connect a very large capacitor or a passive L-C resonant circuit to the dc line for reduction of low-frequency ripple voltage. However, when batteries are connected to the dc output, most of the dc ripple current flows into the battery even if the above circuits are used, because the impedance of the battery is very low compared to that of the circuits. The low-frequency ripple current causes power loss on the battery and the temperature rises. It is well known that the life of a battery is deeply influenced by the temperature. The ripple current, therefore, should be reduced as low as possible. To accomplish reduction of the low-frequency ripple current, a novel topology for the PWM rectifier is presented in this paper. The main circuit is constituted by adding only a pair of switching devices to the conventional PWM converter circuit. With a simple control technique, the ripple energy on the dc line is converted into stored energy on the input ac capacitors through additional switches. The theoretical characteristics are obtained by using the state-space averaging method. The effect of ripple reduction is confirmed by experiments using a breadboard setup. © 1998 Scripta Technica, Electr Eng Jpn, 123(1): 51–62, 1998     

UPFC直流侧电容电压弱控制策略研究

在分析UPFC直流侧电容电压传统控制方式的基础上,提出了直流侧电容电压弱控制策略的概念,并分析了直流侧电容容量、直流侧电压等级和线路传输功率之间的关系.通过仿真实验,比较了单机无穷大系统线路发生三相对称短路时,线性最优控制和直流侧电容电压弱控制策略下系统的运行情况.结果表明该策略能够利用UPFC直流侧电容吸收部分暂态能量,从而加速故障后线路上潮流稳定过程.     

Output current ripple reduction of LED driver using ceramic‐capacitor‐input circuit and buck‐boost converter

This article proposes an LED driver that consists of a ceramic‐capacitor‐input rectifier and a buck‐boost converter. The LED driver has an advantage of long life because it does not contain any electrolytic capacitors. However, the issue with electrolytic capacitor‐less LED driver is that the ripple of the smoothed voltage becomes large due to insufficient capacitance of the smoothing capacitor. The proposed method, which uses the discontinuous current mode of a buck‐boost converter, reduces the output current ripple under such conditions. Experimental results using a 5.7 W LED driver prototype demonstrate that the proposed method reduces the output current ripple and that the percent flicker becomes 4.4%, which is smaller than the recommended upper limit of 8%.     

Improvement of a double-connected diode rectifier with a smoothing capacitor by the use of an interphase transformer

A novel method to reduce harmonics involved in ac line currents of a diode rectifier circuit with a smoothing capacitor inside the dc output is proposed. This circuit has only passive rectifier devices. It is applied to the conventional double-connected diode rectifier, 12-phase rectifier, and is added to an auxiliary circuit comprising an interphase transformer with a secondary winding and a single-phase diode rectifier. Input voltage waveforms of the proposed circuit are quasi 24-step voltages that correspond to those of the conventional 24-phase rectifier. In this paper, circuit performances of the proposed method are explored by analyzing the input voltage waveforms. The effects on harmonic reductions can be examined by theoretical and experimental results; the ratings of system components are investigated. © 1997 Scripta Technica, Inc. Electr Eng Jpn. 118 (4): 46–57, 1997     

不对称半桥单相单级式车载充电系统改进控制策略研究

对称半桥可以有效吸收单相变换系统直流侧二次纹波、减小系统体积、提高功率密度,但当半桥上下桥臂电容容值不等时,会在直流侧产生一次纹波。针对这一问题,分析研究了不对称半桥单相单级式车载充电系统,提出电感电流加电容偏置补偿的改进控制策略。基于该控制策略,从满足二次纹波功率补偿、电池最低电压及避免过调制三方面研究了半桥电路电感及电容参数设计方法。仿真和实验结果验证了不对称半桥通过采用改进的控制策略不仅能够有效滤除二次纹波,且不产生一次纹波,还可降低电池端电压与电流纹波;仿真验证了参数设计方法的有效性。     

适用于Buck电路的一种改进型软开关实现方法

用同步整流加电感电流反向的方法可实现Buck电路开关管的ZVS，但该方法的电感电流纹波比较大．从而会引起较大的输出电压纹波，只适用于对输出电压纹波要求不高的场合。若靠单纯增加输出滤波电容的数量来降低输出电压纹波会大大增加变换器的成本。文中提出了一种改进方案，通过附加一个电感和较小的电容，在实现开关管ZVS的基础上大大减少了输出电压纹波。最后的实验结果验证了该电路的工作原理及有效性。     

buck变换器的输出本质安全特性分析及优化设计

用buck变换器的电感和电容的最大储能之和反映其输出短路释放能量，推导了buck变换器在连续导电模式（CCM）和不连续导电模式（DCM）下的最大输出短路释放能量，若它们部小于最小点燃放电能量，则该变换器是满足输出本安要求的。指出如果变换器在最小负载电阻和最高输入电压的情况下处于CCM，则该状态下的输出短路能量就是该变换器在整个工作范围的最大输出短路释放能量。根据输出纹波电压指标将最小输出电容值用电感表示出来，并通过令最大输出短路释放能量对电感的偏导数为0的方法，得出在给定设计指标条件下使最大输出短路释放能量最小的电感和电容设计参数。实验结果验证了理论分析的正确性。     

基于三相供电电压偏差选取直流电容参数研究

在电压型PWM AC/DC/AC变换中,直流侧储能滤波电容参数的选取是变换器稳定运行的关键因素之一。针对目前直流侧电容选取存在一定的不精确性,分析了AC/DC/AC变换电路稳态时直流电容充放电的原理,对变换器交直流侧电压的关系进行研究,建立了电容纹波电压与三相供电电压偏差之间的数学模型,提出了基于三相供电电压偏差选取直流侧电容参数的方法。分别对单相和三相不可控整流电路提供直流电源时直流侧电容C的合理选取给出了相应的分析和计算,并通过仿真和试验验证了直流储能滤波电容参数确定方法的有效性。     

一种带非电解电容的电动汽车充电电源的建模和设计方法

电动汽车车用电池的寿命通常在50 000 h以上,而传统的电动汽车车用充电电源寿命受电解电容的限制只能在8 000 h左右。为实现充电电源与动力电池的寿命匹配,关键在于将短寿命的DC-link电解电容替换为长寿命的非电解电容或代替电容的其他结构。本文提出了一种基于状态空间平均法的建模方法,重构了包括控制电路和主电路的平均控制模式下的Boost PFC电路。并通过该方法得到全电路的控制框图,最终得到了输出电压对输入电压的闭环传递函数,进而得到了100 Hz两倍工频纹波电压的衰减倍数与DC-link电容之间的关系,证明了DC-link电容容值可以大大低于传统的经验值,实现了长寿命小容值的薄膜电容对短寿命大容值电解电容的替换。最后用仿真和实验样机对该建模方法以及电源的无电解电容化进行了验证。     

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.     

A Three-Phase Inverter with Reactive Power Control

A new type of self-commutated inverter for fixed or moderately variable frequency has been developed. The inverter is characterized by an extremely uncomplicated main circuit. In its basic form the inverter contains two converter circuits: a principal converter circuit and an auxiliary converter circuit. The principal converter circuit transfers power from the input dc side to the output ac side, and the auxiliary converter circuit generates an inductive current to balance the reactive current of a three-phase capacitor on the ac side. This capacitor has the combined function of a phase compensator, a filter capacitor, and is also the source of the commutating voltage. Both converter circuits are of the line commutated type, meaning that at power frequencies normal converter thyristors can be employed. This makes it possible to build high-power inverters without series or parallel connected thyristors. All filter reactors are smoothing reactors placed on the dc side of the converter circuits. Thus the inverter has a very good efficiency even at the higher frequencies. The ability of a converter circuit to generate a negative sequence current when unsymmetrically controlled makes the inverter insensitive to unbalanced loads. The transient behavior of the inverter is similar to that obtained from a conventional self-commutated inverter with an output filter.     

三相有源滤波器直流侧电容与电压波动关系分析及设计

有源滤波器的直流侧通常配置很大的电解电容,电解电容器的电压纹波额定值较低,损耗较大,应对电容值做出合理选择以避免内部发热。面对大容量的谐波补偿要求,并联有源滤波器(Shunt Active Power Filter,SAPF)需要进一步降低系统体积和成本。针对电容值与直流电压纹波关系这一问题,分析了三相SAPF补偿系统的瞬时功率流动,得到对直流电压波动有影响的功率分量,并在特定的负载条件下求取了振荡功率的积分值,得到电容能量波动的精确值,提出了一种考虑电容纹波电压关系的电容容量优化设计方法。利用MATLAB仿真模型并与其他文献比较,验证了所提思路及结果的正确性及有效性。     

Single-phase PWM converter using balanced two-phase rectification

Energy storage devices, such as inductors or capacitors, are needed in single-phase ac to dc converters because instantaneous power flow of input single-phase ac is inherently pulsating and output dc power must have as little ripple as possible. Energy storage devices (such as smoothing inductors or capacitors) are usually inserted on the dc side. In those converters, energy storage ability of the devices cannot be used effectively, especially when dc power ripple is required to be very small. To solve such a problem, this paper presents novel single-phase ac/dc conversion circuits, in which energy storage devices are used at the ac rather than at the dc side. That is, after converting single-phase ac into balanced (rectangular) two-phase ac using variable reactance element, reconversion of it into dc is carried out. This paper presents a control method for the converters and the variable reactance devices, and performance of the proposed circuits is confirmed using computer simulation.     

A power decoupling control method for an isolated single‐phase AC‐to‐DC converter based on a high‐frequency cycloconverter

This paper proposes a new power decoupling method for a high‐frequency cycloconverter which converts the single‐phase line‐frequency ac input to the high‐frequency ac output directly. The cycloconverter consists of two half‐bridge inverters, two input filter capacitors, and a series‐resonant circuit. The proposed power decoupling method stores the input power ripple at double the line frequency in the filter capacitors. Therefore, the proposed method achieves a unity power factor in ac input and a constant current amplitude in the high‐frequency output without any additional switching device or energy storage element. This paper theoretically discusses the principle and operating performance of the proposed power decoupling method, and the viability is confirmed by using an experimental isolated ac‐to‐dc converter based on the high‐frequency cycloconverter. As a result, the proposed power decoupling method effectively improved the displacement power factor in the line current to more than 0.99 and reduced the output voltage ripple to 4% without any electrolytic capacitor.     

考虑ESR的DC-DC型开关变换器的研究

电容的寄生参数串联等效电阻（ESR）是电容的一个重要参数,它对电路的性能有较大影响,特别是当电容用于DC-DC型开关变换器中输出电压滤波时对输出电压的纹波影响较大,由于电容的ESR存在,它增加了DC-DC型开关变换器动态小信号数学模型的一个零点,在分析和设计DC-DC型开关变换器系统中应予以重视。文中以Buck型开关变换器为例,分析讨论了电容串联等效电阻对Buck型开关变换器的输出纹波电压及动态小信号数学模型的影响,利用psim软件对所得的结论进行了仿真验证。所得到的结论对DC-DC型开关变换器其它拓扑的滤波电容的选择和控制系统设计有参考价值。     

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     

一种单相MMC预充电控制策略

模块化多电平换流器(MMC)的预充电通常可分为两个阶段:不控整流以及boost升压。三相MMC的boost升压控制技术已经较为成熟。然而与三相MMC不同的是,单相MMC的直流侧具有独立电容。因此,单相MMC的boost升压阶段必须同时考虑子模块电容和直流侧电容,这是单相MMC预充电的难点所在。文中提出了一种基于单相半桥子模块(HBSM)的预充电策略。该策略的第一阶段仍为不控整流,第二阶段通过上下桥臂的能量之和与能量之差的控制来实现子模块电容的boost升压。之后,直流侧电容电压被交流侧持续馈入的能量充到额定值。该控制方案使整个启动过程快速、平滑、稳定,对单相MMC做整流运行具有重大价值。最后,所提方案的有效性及正确性在一台单相8个子模块的实验样机上得到了验证。     

通信电源中单相Buck功率因数校正器的研究

研究了断续电流模式(DCM)下单相Buck电路作为功率因数校正器的拓扑电路和工作原理,给出了实现功率因数校正的临界条件和临界电感的计算公式;分析了输入电流产生畸变的原因和影响畸变程度的主要因素;分别用功率匹配法和等效电流源法对该电路的输出电压纹波进行了分析,总结了输入电流畸变与输出电压纹波的定性关系。仿真结果验证了理论分析的正确性,表明单相Buck功率因数校正器(即单相Buck PFC)可以满足通信电源对功率因数的要求。     

单相PFC输出母线电压波动抑制与脉动功率转移技术

采用电解电容抑制单相功率因数校正PFC(power factor correction)输出母线电压波动的方式受到电解电容本身寿命短、体积大等因素限制,难以做到高功率密度以及长时间稳定性。因此,提出一种采用双向升降压电路实现输出母线功率解耦的策略,从而可移除母线处的电解电容。详细分析了解耦电路的基本工作状态,并基于相关参数的设计考虑提出一种新型控制方案,在双闭环的基础上引入输出母线电压波动加权控制,进一步增加在功率解耦支路与输出母线之间转移的脉动功率,减小母线电压纹波,实验结果验证该电路及控制方案的有效性。