Research on Reactive Power Optimization Scheme of AC Metro Power Supply System Considering the Trade-off of Investment and Benefit

Due to the advantages of fast running speed and long power transmission distance, AC metro systems have been implemented and are planned for construction in most medium and large cities globally. This has become a major trend in the development of urban rail transit, particularly for connecting central urban areas with suburban regions and surrounding towns and cities. However, the issue of excessive capacitive reactive power in the AC metro power supply system, primarily caused by the use of cables linking various electrical systems, is especially pronounced during nighttime and initial operational phase. To address this, this paper proposes a reactive power optimization scheme for AC metro power supply system considering the trade-off between investment and benefits. First, the topology and operational mode of the metro power supply system are introduced, followed by the establishment of a reactive power flow model for the system. Subsequently, a series of evaluation indices are proposed to assess the reactive power level. Finally, a multi-objective optimization method for reactive power management, based on an improved particle swarm optimization algorithm, is presented. This method integrates both investment and benefit considerations. Using an AC metro system in a southern Chinese city as a case study, the results demonstrate that the proposed reactive power optimization method effectively mitigates the issue of excessive reactive power in the power supply system.