适用于PET的负载电流前馈控制策略

电力电子变压器(power electronic transformer,PET)由级联H桥(cascaded H-bridge,CHB)和双有源桥(dual active bridge,DAB)变换器级联组成,当发生负载突变时,PET的高、低压直流母线电压存在较大波动,无法迅速达到平衡。为了解决此问题,提出一种适用于级联系统的负载电流前馈控制策略。该策略由DAB级和CHB级的负载电流前馈2部分组成。前者是通过低压侧负载电流计算得到DAB级的补偿移相角,后者则考虑级联系统的输入输出功率守恒,将负载电流直接前馈到CHB级。同时,考虑到CHB级电流内环的延迟,CHB整流级采用一阶微分与功率均衡相结合的电流前馈控制策略。所提控制策略只需要采样低压直流母线负载电流,极大程度地节约了系统成本,且操作简单,易于实现。仿真和Starsim实验验证了所提控制方法的正确性和有效性。

Load Current Feedforward Control Strategy for Power Electronic Transformer

Power Electronic Transformer (PET) consists of cascaded H-bridge (CHB) converters and dual active bridge (DAB) converters. However, the fluctuation of load causes large voltage fluctuation of high voltage DC (HVDC) and low voltage DC (LVDC) buses of PET. To address this problem, a load current feedforward control strategy for cascaded systems is proposed, which consists of two parts: the load current feedforward of DAB stage and CHB stage. The former obtains the compensated phase shift ratio of the DAB stage through calculation of the load current at the low voltage side, while the latter feeds forward the load current to the CHB stage with consideration of the power conservation of the cascade system. Moreover, considering the delay of the inner current loop of the CHB stage, the first order differential is introduced to the feedforward strategy in CHB stage, which further suppresses the voltage fluctuation on HVDC buses. The proposed control strategy only needs to sample the load current of LVDC bus, which saves the system cost greatly. In addition, the proposed strategy is easy to operate and implement. Simulation and Starsim experimental results verify the correctness and effectiveness of the proposed control method.