A Novel Reactive Power Control Mitigating a DC link Ripple voltage of Reactive Power Compensator for Distribution Line

Abstract

In this paper, a reactive power compensator (RPC) is used for stabilization of the low voltage distribution line, and a novel reactive power control method of the RPC is proposed to reduce size as well as maintain its long lifetime. In the single-phase system, a 2nd harmonic component is inevitably generated in the DC link voltage, and this phenomenon gets even worse in case that the capacity of DC link capacitor decreases in order to reduce the size and cost of the RPC. A reactive power control is performed by controlling the d-axis current in the virtual synchronous reference frame, and the voltage control for maintaining the DC link voltage is implemented through the q-axis current control. The proposed method for compensating the ripple voltage effect consists of an extraction unit of DC link ripple voltage, high pass filter (HPF), and time delay unit. The HPF removes an offset component of DC link ripple voltage caused by an integrator, and a time delay unit compensates the phase leading effect due to the HPF. The compensated DC link voltage is used as a feedback component of voltage control loop in order to supply the stable reactive power. The performance of the proposed algorithm is verified through simulation and experiments. In case that DC link capacitor is reduced to 375uF, an effect of ripple voltage is reduced to 8V pp from 74V pp in the voltage control loop, and total harmonic distortion (THD) of the current is improved.