A Method for Reducing Commutation Failure Risk in Multi-Infeed HVDC Systems

This paper presents a method to reduce the risk of single or multiple commutation failures in multi-infeed HVDC systems caused by AC faults occurring at the receiving-end AC system. Based on the node impedance matrix, a voltage coupling factor (VCF) is derived to analyze the effect of faults on AC buses on voltage of inverter AC buses. Then, a method to reduce the commutation failure risk of multi-infeed DC systems is proposed, combining with the criterion of commutation failure based on the minimum extinction angle. In the design stage of converter stations, the short-circuit impedance of converter transformers should be reduced as much as possible on the basis of considering all kinds of restrictive factors. By using this method, the critical voltage coupling factor can be increased and the commutation failure risk can be reduced. The effectiveness of this method is demonstrated by the electromechanical-electromagnetic hybrid simulation results based on a practical multi-infeed HVDC system.