中文说明：NPC逆变器的电源电路由四个开关和两个二极管组成，其中两个中心开关和二极管允许输出端连接到直流链路的中性点
English Description：
The power circuit of the NPC inverter is composed of four switches and two diodes where the two center switches and the diodes allow the output terminal to be connected to the neutral point of the DC link