Research of Power Compensator for Single-Phase Three-Wire Distribution System

在本研究中，我们首次提出了一种改进的PFC--功率因数校正转换器。它由两个半桥PFC结构组成，共用一条中性点电源线和两个平滑电容器，并连接到单相三线制配电系统。虽然传统的半桥PFC变流器往往存在不平衡的问题，但已有的研究表明，在没有额外控制方案的情况下，两个电容电压始终是平衡的。它有两个相同电压和同相的交流电源。许多交流负载可以连接到配电系统。当用户随机使用这些负载时，两个源电流往往是不平衡的。如果许多工作负荷偏向单边电源，则断路器的操作可能会导致断电。因此，即使负载电流不平衡，也希望通过in…来均衡两个源电流在配电系统中加入更多的电流均衡器。上述PFC转换器既可以作为交-直转换器，也可以作为交-交逆变器工作。此外，两个相应的半桥结构，转换器1和转换器2，可以单独控制。例如，当转换器1作为AC-DC转换器操作时，另一个转换器2可以同时作为逆变器进行DC-AC转换。在这项研究中，我们利用所提出的变流器的上述特性来研究一种电流均衡器，在配电网中可能存在几个功率因数较低的交流负载，例如感应电机。静止无功发生器的使用必须对其无功功率进行有效补偿。此外，传统的具有大平滑电容的二极管整流器利用电视、计算机等中流行的直流电源，将谐波电流流出到交流电源中，除非使用PFC变流器。为了防止由谐波引起的故障，在配电系统中采用有源滤波器是最好的。因此，我们将上述电流均衡器改进为具有多种功率补偿功能的新型AC-DC转换器。仿真和实验证明，在单相三线制配电系统中，除了所提出的变流器外，它本身可以向负载输出直流功率，同时还可以起到电流均衡器、静止无功发生器和有源滤波器的作用，以补偿单相三线制配电系统的电能质量。较少

We have first proposed an improved PFC, Power Factor Correction, converter in this research. It is composed of two half-bridge PFC structures in common with a neutral source line and two smoothing capacitors, and connected to the single-phase three-wire distribution system. It has been made clear that both capacitor voltages can be always in balance without extra control schemes, though the conventional half-bridge PFC converters tend to have the unbalanced ones.The above distribution system is employed extensively in Japan, USA and the other countries. It has two ac sources with the same voltage and in phase. Numerous ac loads may be connected to the distribution system. As a consumer makes use of these loads at random, two source currents tend to be unbalanced. If many working loads lean to a one-sided source, the power interruption may occur by the operation of circuit breakers. Therefore, even if the load currents are unbalanced, it is desired to equalize both source currents by in … More serting Current Balancer into the distribution system.The above-proposed PFC converter can operate not only as the ac-dc converter but also as the dc-ac inverter. Furthermore, two respective half-bridge structures, Converter 1 and Converter 2, can be individually controlled. For example, while Converter 1 operates as the ac-dc converter, another Converter 2 can make the dc-ac conversion as the inverter simultaneously. In this research, we have investigated a Current Balancer by applying the above property of the proposed converter.There may be several ac loads with poor power factor, such as induction motors, in the distribution system. The employment of Static Var Generator must be effective for compensating their reactive powers. Moreover, conventional diode rectifiers with large smoothing capacitors, made use of the popular dc sources in TVs, computers, and so on, flow out the harmonic currents into the ac source, unless the PFC converters. In order to prevent the troubles by harmonics, it is preferred to employ Active Filter into the distribution system. Therefore, we have improved the above Current Balancer to the novel ac-dc converter combined with several power compensator functions. It has been confirmed by the simulations and the experiments that itself can output the dc power to its load, and simultaneously it can perform as Current Balancer, Static Var Generator and Active Filter in order to compensate the power qualities of the single-phase three-wire distribution system, where various ac loads are connected besides the proposed converter. Less