A novel control strategy to suppress transient overvoltage balancing active power impact reduction caused by commutation failure

The line-commutated high voltage direct current (LCC-HVDC) is easy to occur commutation failure (CF), during the CF and recovery period, lots of reactive power surplus can cause transient overvoltage (TOV) in the sending end system. Generally, the reactive power control is adopted, however, the simultaneous existence of active and reactive power during the fault, which may further worsen the transient active power impact. To handle this problem, a novel control strategy is proposed to suppress TOV balancing active power impact reduction. Firstly, this paper reveals that DC current is the dominant factor affecting the reactive power consumption by the rectifier and transient voltage amplitude. By establishing a mathematical relationship between DC current and transient voltage, it is shown that excessive reduction in DC current is the primary cause of TOV. Furthermore, the interplay between DC electrical quantities, active power, and reactive power is examined to understand how changes in DC current and reactive power affect active power, and a mathematical relationship between transient voltage and active power is established. On this basis, a novel control strategy is proposed. This strategy can not only suppress TOV and balancing active power impact reduction, but also reduce the probability of subsequent CF. Finally, based on the CIGRE HVDC Benchmark Model in PSCAD platform, a test system is built to verify the effectiveness of the proposed control strategy under different working conditions.