适应电力电子变压器功率双向交换的低电压穿越运行控制策略

Low-voltage ride through strategy for bidirectional power electronic transformers

针对交流电网故障导致机端电压跌落时电力电子变压器的运行特点,该文提出一种适应PET功率双向交换的低电压穿越运行控制策略。在电压跌落期间,根据正序电压跌落深度,自动调整注入无功功率,以协助电网电压恢复;并根据电压跌落前PET有功传输情况,在保证PET电流不越限的前提下,最大程度保持有功传输的水平及方向,减少对交直流电网的扰动。在电压不对称跌落情况下,同时辅之以负序电流抑制控制,以保证注入电网电流的对称性。最后,通过仿真模型验证该低电压穿越运行控制策略的有效性。

In view of the operating characteristics of PET when the AC grid voltage sags,this paper proposes a LVRT strategy for bidirectional PET.During the voltage drop,the injected reactive power is automatically adjusted according to the positive sequence voltage drop to assist the grid voltage recovery.According to the active power of PET before the voltage sag,the level and direction of the active power are maintained as far as possible without exceeding the current limit to reduce the disturbance to the AC/DC grids.In the case of asymmetric voltage drop,the negative sequence current suppression is regarded as the supplementary method to ensure the symmetry of the injected grid current.Finally,the effectiveness of the proposed LVRT strategy is verified by the case study.