中文摘要：

当传统三相两电平六开关逆变器的某个功率管发生开路或短路故障时,四开关逆变器作为一种容错拓扑结构可以维持三相系统继续运行。然而,由于有一相负载电流从电容中点流入流出,势必导致母线中点上下两个电容的电压波动。对需要经常改变运行工况的场合,两电容电压甚至会向相反方向漂移,严重影响系统的可靠运行。首先通过电路分析给出电容电压波动公式,指出从正常运行切换到四开关拓扑结构瞬间,流入电容中点电流的相位对两电容电压波动的影响,分析了电容电压产生漂移的原因并给出通过发送特定开关状态实现两电容电压均衡的控制方法。实验结果验证了分析的正确性和电压均衡控制方法的有效性。

英文摘要：

When open or short circuit fault occurs for a power device in traditional three-phase two-level six-switch in-verter,the four-switch inverter as a fault-tolerant topology can maintain the operation of system.But there is one phase load current flowing in and out the midpoint of DC-link,which will inevitably cause the fluctuation of two capacitors upper and lower the midpoint of DC-link.For the occasion where operation conditions change frequently,the two ca-pacitor voltages will drift in the opposite direction even seriously affect the system reliable operation.The fluctuation formula of capacitor voltage is firstly derived through the circuit analysis.Subsequently,the reason of two capacitor voltage drifting is analyzed and corresponding balancing control method is introduced.The experimental results verify the correctness of the analysis and effectiveness of the balancing control method.