基于无缝切换技术的三相不平衡换相开关研究与设计

应用三相不平衡换相开关可缓解低压配电网中三相电流不平衡现象，但目前分换相开关的相序切换原理过于简单，存在换相过程断电时间长、电压和电流畸变严重等问题，限制了其广泛应用。为此，提出了一种以功率因数校正电路与逆变器电路为基础，由初始阶段、当前相跟踪阶段、切换相跟踪阶段以及换相完成阶段4个阶段组成的整体换相方案。首先通过功率因数校正电路与逆变电路使得将要相互切换的两相的电压调整为同幅、同频与同相，然后电力电子开关完成换相动作，最终实现相间的无缝切换。仿真与实验结果表明，所提出的方案保证了换相过程的不间断供电，同时改善了电压和电流的畸变问题。

Research and design of three-phase unbalanced commutation switch based on seamless commutation technology

The application of three-phase unbalanced commutation switch can alleviate three-phase current unbalance in low-voltage distribution network. However, the phase sequence switching principle of split commutation switch at present is too simple, and there are some problems such as long power-off time, and serious voltage and current distortion in commutation process, which limit its wide application. An overall commutation scheme based on the power factor correction circuit and the inverter circuit is proposed, which is composed of four stages, including initial stage, current phase tracking stage, switching phase tracking stage and commutation completion stage. Firstly, the voltages of the two phases to be switched to each other are adjusted to the same amplitude, the same frequency and the same phase through the power factor correction circuit and the inverter circuit. Then the commutation action is completed by the power electronic switches, and finally the seamless switching between phases is realized. The simulative and experimental results show that the proposed scheme ensures the uninterrupted power supply in the commutation process, and improves the distortion of voltage and current.