Research on Harmonic Weakening Modulation of Railway Power Conditioner under High Double-Frequency Ripple of DC Side Voltage

In single-phase railway power conditioner (RPC) system, the coupling of AC and DC power will cause single-phase inverter DC bus voltage to contain lots of double-frequency AC voltage ripple components, resulting in lots of third harmonics on the AC side, which have a serious impact on the railway power quality if traditional modulation methods are used. In this paper, a harmonic weakening modulation method of RPC voltage is proposed for the case of high double-frequency ripple rate on DC side, and a delay-free adaptive state observer is designed to separate DC component and double-frequency ripple component of the DC bus voltage, and the inverse quadratic component is injected into the modulation coefficients to complete the weakening of third harmonic of AC side of the RPC and the suppression of double-frequency ripple on DC side, and reduce the total harmonic distortion rate. Finally, the simulation results verify its effectiveness.