A Transformer-Integrated Traction Power Supply System with Comprehensive Power Quality Control

The traction power supply system (TPSS) is suffering from numerous power quality issues, such as negative-sequence currents, voltage sags, and harmonic pollution, which can jeopardize the stable operation of the utility grid and the traction system. This paper proposes a hybrid V/V transformer-integrated traction power supply system (HVV-TPSS) with comprehensive power quality compensation. The parallel converters (PCs) and series converters (SCs) of HVV-TPSS are integrated to the three-limb four-winding V/V transformer for current and voltage compensation without auxiliary transformers, thus enhancing space utilization. Moreover, HVV-TPSS can perform comprehensive power quality management, including current-related power quality issues and severe disturbances related to voltage faults and harmonics, not only strengthening the voltage compensation capability but also improving its integration level. By establishing the mathematical model of the hybrid V/V transformer unit, the fundamental compensation principles of current and voltage within HVV-TPSS are elucidated. Subsequently, this paper further analyzes the working principle for comprehensive power quality compensation of HVV-TPSS under steady-state and grid fault conditions, followed by the proposal of its comprehensive control strategy. Finally, the effectiveness of HVV-TPSS is validated through simulations and experiments.