Coordinated Control Strategy for Commutation Failure Recovery in Multi-infeed AC/DC Systems Based on Multi-infeed Operating Short Circuit Ratio

In multi-infeed AC/DC systems, the simultaneous commutation failure of multiple HVDC systems will seriously threaten the safe operation of the system. A coordinated control strategy for commutation failure recovery is proposed. Firstly, by analyzing the shortcomings of the MIESCR, the multi-infeed operating short circuit ratio (MIOSCR) is proposed. Next, the recovery sequence coordination principles that should be followed for the commutation failure recovery are summarized. Then, based on the MIOSCR, a two-stage coordination control strategy is proposed. Finally, the simulation results of Jiangsu power grid in PSS/E show that the strategy can effectively shorten the duration of commutation failure recovery in multi-infeed AC/DC systems.

I. Introduction

With the development of the HVDC systems and the construction of the West-East Power Transmission Project, the number and capacity of HVDC systems have increased sharply. The East China Power Grid has become an extra-large multi-infeed AC/DC system with the most DC drop points, the closest electrical connection, and the largest power receiving in the world^[1]. A short-circuit fault may cause commutation failure of an HVDC system or multiple HVDC systems. Then it will cause the drop in DC voltage, the increase in direct current, and the drop in DC power. If the continuous commutation failure occurs in an HVDC system, it may cause the HVDC system blocked. In a receiving-end system, if the electrical distance between points of common coupling (PCCs) is relatively close, a single short-circuit fault may cause the commutation failure occurs in multiple HVDC systems. Therefore, it is very necessary to adopt appropriate preventive measures to decrease or even avoid the occurrence of the continuous commutation failure.