AC fault ride through control strategy on inverter side of hybrid HVDC transmission systems

Hybrid high-voltage direct current (HVDC) transmission systems employ a new type of HVDC transmission topology that combines the advantages of the line-commutated converter system and the voltage-source converter system. They can improve the efficiency and reliability of long-distance power transmission. However, realizing alternating-current (AC) grid-fault ride through on the inverter side of a hybrid HVDC transmission system is a challenge considering that a voltage-source converter based HVDC (VSC-HVDC) is used on the inverter side. In this study, a control strategy for an overvoltage fixed trigger angle based on the power-balance method is developed by fully utilizing the operation characteristics of a hybrid HVDC transmission system. The strategy reduces the inverter-side overvoltage of the HVDC system under a fault in the inverter-side AC system. Simulations based on Gezhou Dam are conducted to validate the effectiveness of the proposed strategy.