三 电 平 串 联 谐 振 变 换 器 内 外 管 均 压 方 法

With a three-level half-bridge structure, the three-level series resonant converter (TL-SRC) has the advantage of significantly reducing the number of power modules and thus reducing the cost, so it is widely used in DC transformers. However, when the TL-SRC operates in the power reverse transmission mode, the inconsistent charging current of the junction capacitors of the inner and outer switches may cause a voltage imbalance of the switching devices, which brings the risk of overvoltage damage to the devices. To solve this problem, this paper analyzes the mechanism of voltage imbalance of the three-level inner and outer switches in the power reverse transmission mode. Based on the mechanism, a passive voltage balancing method with parallel auxiliary capacitors at both ends of the inner switch is proposed, and the parameter design method of auxiliary capacitors is given. Further, an active voltage balancing method for controlling the timing of the inner and outer switches is proposed, and the basis for designing the timing of the inner and outer switches is derived. Finally, the correctness of the theoretical analysis and the feasibility of the proposed method are verified on a 75 kW experimental platform.