Flexible Fractional Compensating Mode for Railway Static Power Conditioner in a V/v Traction Power Supply System

Railway static power conditioner (RPC) is commonly used to improve the power quality (PQ) indices of the grid that supplies an electrified railway system (ERS). The main problem of the RPC is its high kilovoltampere rating, as it is intended to operate in a maximum compensating mode (MCM). This paper presents a flexible fractional compensating mode (FrCM) and its corresponding control system to mitigate the required rating of the RPC. The FrCM aims to fully utilize the available rating of the compensator for approaching the MCM. The FrCM not only reduces the kilovoltampere rating of the RPC but also maintains the grid-side PQ indices within their standard ranges and improves the performance of the dc-link voltage. The proposed method does not need any modification in power stages and adding extra circuit element(s); hence, this model can be used in both design and operating phases. Simulation and laboratory-scaled experimental results are presented to show the effective performance and rating reduction of the proposed method.