Research on AC fault ride through strategy for LCC-VSC based on trigger angle clamp control

The hybrid line commutated converter (LCC)- voltage source converter (VSC) high voltage direct current transmission system has both the advantages of LCC and VSC technology. However, once an AC fault occurs at the receiving end, the DC voltage will rise sharply due to the unbalanced power. To tackle this DC overvoltage problem, one AC fault ride through strategy for LCC-VSC based on trigger angle clamp control is proposed. Firstly, the DC overvoltage mechanism of LCC-VSC is studied. Then the trigger angle clamp control strategy for LCC is discussed, based on which an AC fault ride through strategy is proposed. The trigger angle clamp control strategy can maximize the control capability of the overvoltage problem by clamping the trigger angle to the maximum value when the AC fault occurs. The comparative simulation results in PSCAD/EMTDC can validate the effectiveness of the proposed method.