A comprehensive control strategy for power quality enhancement in railway power system

The selection of the correct traction transformer reduces power quality (PQ) issues and minimizes the high impact of electrified railway systems (ERS) on the electrical grid. In contrast to power systems, the use of Yd11 transformers in ERSs is less common but represents a more suitable solution. This article assesses the performance of the Yd11 transformer in a traction power substation (TPS) and establishes its superiority over Scott and V/V transformers. The evaluation and analysis are carried out based on factors such as system connectivity, PQ, and economic considerations. A railway PQ compensator (RPQC) serves as the primary compensator, with the TPS acting as an auxiliary compensator in the analysis, both under balanced and unbalanced conditions. Simulation results validate the accuracy of the theoretical analysis. The proposed control system utilizes a proportional-integral (PI) controller integrated with a type-2 fuzzy logic controller (Type-2 FLC) due to the fast and dynamic nature of traction loads. Carrier-based pulse width modulation (PWM) signals are employed to generate pulse signals for the full bridge RPQC switches. The success of the suggested control technique is demonstrated through simulation results for V/V, Scott transformers, and Yd11 transformers. The results clearly indicate that the Yd11 transformer achieved superior performance, with distortion levels of 1.57% and 1.17% at loads ς=0.5 and ς=0, respectively.