YN/VD connected balance transformer-based hybrid power quality compensator for harmonic suppression and reactive power compensation of electrical railway power systems

Abstract In this study, YN/VD connected balance transformer-based hybrid power quality compensator (HPQC) is proposed for harmonic suppression and reactive power compensation in electrified railways. The HPQC is composed of a balance transformer in YN/VD connection, a controllable three-phase voltage source inverter (VSI), as well as fully-tuned passive power filters (PPFs). It is able to integrate the active compensation device with the main transformer, without using auxiliary step-down transformer. This circuit configuration enables one to adopt VSI with low power rating, so that merits such as easy for system integration and low operation losses can be achieved. In this paper, the equivalent circuit model and the corresponding mathematical model of the HPQC in the harmonic domain are established to reveal its mechanism on harmonic suppression. And then, the working principle and control strategy of such a new topology are elaborated in detail. Finally, simulation and experimental results are provided to verify the feasibility and effectiveness of the above-mentioned structure and control strategy.