本文提出了一種應用于異步電機調速系統的基于三相四橋臂結構的逆變策略，它既改
善了系統的EMC 性能又提高了其可靠性。在這個策略中，如果系統正常工作，第四橋臂可以平衡逆變器的輸出電壓，從而降低系統的共模電壓。在這個過程中使用本文提出的狀態交換策略不僅突破了以往SPWM 調制指數必須在0.66 以下的限定，避免了直流電壓利用率低下的問題，而且優化了系統的差模輸出，將總的諧波失真度降到最低。如果系統的一個逆變橋發生故障，第四橋臂可以作為冗余橋臂代替故障橋臂的工作。采用暫時開環控制可以是橋臂切換平穩，降低切換過程中出現的過沖電流。這樣系統可以不間斷地容錯運行，整體的可靠性得到顯著改善。該策略的有效性通過仿真和實驗得到了證實。
Abstract：This paper proposes a strategy based on three-phase four-leg structure that can improve either reliability or EMC performance in speed regulating system of asynchronous motor. In the strategy, if the system is working orderly, the fourth leg functions in balancing the output voltage so as to reduce the common mode (CM) voltage of the system. During this process, the use of state exchange method not only breaks through the limitation of SPWM modulation index to avoid the extremely low utilization ratio of direct current (DC) voltage, but also reduces the total harmonic distortion factor (THD) of the output voltage. If an inverter leg of system is in failure, the fourth leg acts as the redundant leg to take the place of that one. The transitory open-loop control is adopted to reduce the overshoot current and to switch leg smoothly. Thus the system can run uninterruptedly in the fault tolerant operation mode and the holistic reliability can be improved markedly. The effectiveness of the strategy is proved by simulation and experiment results.
關鍵詞：三相四橋臂，可靠性，共模電壓，容錯運行，策略
Keyword：Three-phase four-leg, reliability, common mode voltage, fault tolerant operation,
strategy