采用低压中点调节器实现三桥臂逆变器三相四线供电的方法

Three-phase Four-wire Power Supply Method for Three-phase Three-leg Inverter Using Low-voltage Neutral Point Regulator

三相四线制供电可以有效避免不平衡负载导致的交流侧中点电位偏移。为简化逆变器抑制三相不平衡电压的拓扑和控制,分析了三相三桥臂逆变器采用中点电位调节的方法向不平衡负载供电的工作原理,得到中点调节器的输出电压规律以及输出功率特性。由于调节中点电位需要的电压很小,且调节器输出功率只为无功功率,因此该调节器可采用低压大电流的桥臂,其供电的直流电源只需要提供功率器件的损耗功率。给出了中点调节器拓扑,并分别给出三桥臂逆变器以及该中点调节器的控制策略,实现了该调节器的完全独立控制。最后,以三相七电平逆变器为例,调节器选用三电平拓扑,进行了仿真和实验验证,证明了低压中点调节器的正确性与可行性。

Three-phase four-wire power supply of inverter can effectively avoid the AC side neutral potential offset caused by unbalanced load.In order to simplify the topology and control o f three-phase unbalanced voltage suppression,this paper analyzed the working principle of three-phase three-leg inverter using neutral point potential regulation to supply power to unbalanced load,and obtained the output voltage law and power characteristics of the neutral point regulator.Because the voltage required to regulate the neutral point potential was very low and the output power of the regulator was only reactive,the regulator could adopt low-voltage high-current legs,and the DC power needed only to supply the loss o f the power devices.The neutral point regulator topology and the control strategies o f the three-leg inverter and the neutral point regulator were given respectively,realizing completely independent control of the regulator.Finally,with a three-phase seven-level inverter taken as an example and a three-level topology adopted as the regulator,simulation and experimental verification was carried out,proving correctness and feasibility of the proposed neutral point regulator.