Optimal allocation of synchronous condensers for reducing commutation failure risk in multi-infeed LCC-HVDC systems

Commutation failures (CFs) caused by AC faults of the receiving-end system are regarded as a classical faulty event in multi-infeed LCC-HVDC systems, and reasonable configuration of synchronous condensers can effectively reduce the CF risk. Simulation and actual power grid operation experience show that CF caused by faults has probability characteristics, ignoring the CF probability may make the synchronous condenser's configuration inaccurate. In this paper, a method for the optimal allocation of synchronous condensers considering the CF probability is proposed to reduce CF risk in multi-infeed LCC-HVDC systems. First, a CF risk index is proposed, which can represent the relationship between the probability and severity of CF. The CF risk index considers the impacts of the types, locations, and occurrence time of AC faults on CF and the impacts of CF on the receiving-end system. Second, a fast and accurate calculation method for the CF risk index is proposed based on the voltage drop and AC-DC voltage asymmetry factor methods, which improved the accuracy and efficiency of theoretical calculations. Third, the optimal configuration model of synchronous condenser is established to reduce the CF risk index and cost, which can simultaneously optimize the number, size, and placement of synchronous condensers. Finally, an optimal allocation of synchronous condensers is demonstrated through genetic algorithm in the modified IEEE 118-bus system to show the effectiveness of the proposed method.