Enhanced Commutation Failure Predictive Detection Method and Control Strategy in Multi-Infeed LCC-HVDC Systems Considering Voltage Harmonics

摘要

Voltage harmonics are very likely to cause commutation failure (CF) in multi-infeed LCC-HVDC systems. However, this has not been sufficiently considered in earlier CF detection methods and control strategies. In this paper, by incorporating the voltage harmonics into the inverter quasi-steady-state model, an extinction angle predictive algorithm is firstly presented to propose the enhanced CF predictive detection method. Compared to earlier methods, the enhanced method can detect both local and concurrent CFs more accurately. Moreover, the enhanced method is then used as the starting unit of the enhanced CF predictive control strategy to enable its effective activation. To develop the enhanced strategy, a firing angle order predictive algorithm is introduced using the inverter quasi-steady-state model with the voltage harmonics considered. Compared to earlier strategies, the enhanced strategy can mitigate both local and concurrent CFs more effectively. Furthermore, the response speed of the enhanced method and strategy is evaluated by comparing CF characteristics and signal process delay. It is shown that since the timescales of the voltage harmonics induced CFs are longer than signal process delay, the response speed is fast enough to ensure their practicality. Finally, simulation results based on a dual-infeed LCC-HVDC system validate the enhanced method and strategy.