Research on improved hybrid power quality conditioner for VV co-phase railway power supply system

Conventional Hybrid Power Quality Conditioner (HPQC) adopts LC coupling branch and L coupling branch in the back-to-back converters to reduce the converter compensation capacity as well as the DC voltage. However, HPQC could only achieve the minimum compensation capacity under certain special load condition. To maintain the converter compensation capacity at a low level under all load conditions, an Improved Hybrid Power Quality Conditioner (IHPQC) is proposed in this paper. The conventional fixed coupling branches are replaced by thyristor switch branches to adjust the branch impedance dynamically. The compensation principle of conventional HPQC is firstly introduced and the defect of HPQC when compensate varying locomotive load is analyzed. And then the compensation principle of proposed IHPQC is proposed. At last, simulation and experiment results verified that the IHPQC could reduce the converter compensation capacity effectively.