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）变换器。它由两个半桥式PFC结构组成，共有一个中性源线和两个平滑电容器，并连接到单相三线制配电系统。已经明确的是，这两个电容器电压可以在没有额外控制方案的情况下始终处于平衡状态，尽管传统的半桥PFC转换器往往具有不平衡的电压。上述配电系统在日本、美国等国家广泛应用。它有两个具有相同电压和相位的交流电源。许多交流负载可能连接到配电系统。当用户随机使用这些负载时，两个源电流往往不平衡。如果许多工作负载倾向于一个单侧源，则可能由于断路器的操作而导致电源中断。因此，即使负载电流不平衡，也需要通过在配电系统中设置电流平衡器来平衡两个源电流。本文提出的PFC变换器既可以作为交直流变换器，也可以作为直流-交流逆变器。此外，两个各自的半桥结构，转换器1和转换器2，可以单独控制。例如，当转换器1作为交直流变换器时，另一个转换器2可以同时使直流-交流转换为逆变器。在这项研究中，我们利用所提出的变换器的上述特性研究了一个电流平衡器。在配电系统中，可能存在几个功率因数较差的交流负载，例如感应电动机。采用静态无功发电机必须能有效地补偿其无功功率。此外，传统的二极管整流器采用大平滑电容，利用电视、计算机等中流行的直流电源，将谐波电流输出到交流电源，除非PFC转换器。为了防止谐波引起的故障，配电网最好采用有源滤波器。因此，我们将上述电流平衡器改进为结合多种功率补偿器功能的新型交直流变换器。仿真和实验结果表明，该变换器既能向负载输出直流电源，又能同时作为电流平衡器、静态无功发生器和有源滤波器来补偿单相三线制配电系统中各种交流负载的电能质量。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