光伏直流变压器不闭锁零电压穿越策略

Aiming at the low voltage ride through problem of photovoltaic direct current transformer（DCT）under bipolar fault of medium voltage direct current （MVDC） system，based on the topology structure of sub⁃ module with dual active bridge and full bridge isolated circuit，the fast implementation scheme of maximum power point tracking control during normal operation of photovoltaic DCT is analyzed. Then，based on the output characteristics of photovoltaic panels，a DCT non-blocking ride through strategy is proposed，which is insensitive to the fault duration and can realize zero voltage ride through under severe faults. Furthermore，aiming at the problem of the overvoltage and submodule voltage imbalance in the transient process of fault ride through，a smooth switching scheme among multiple control strategies is proposed to reduce the over⁃ voltage during the transient process and improve the voltage balance effect among submodules. Finally，a simulation model is built in MATLAB／Simulink platform to verify the effectiveness of the proposed strategy.