Reactive power compensation with improvement of current waveform quality for single-phase buck-type Dynamic Capacitor

Due to relatively low cost and flexible performance, Dynamic Capacitor (D-CAP) is often designed to implement dynamic reactive power compensation, whose output current might distort under the effects of background harmonic voltage from the grid or non-ideal PWM mode caused by non-linear switch characteristics. This paper presents a reactive power compensation control strategy with waveform quality amelioration of output capacitive current for single-phase Buck-type D-CAP. Through establishing basic control equations, reactive power compensation principle and equivalent model of single-phase Buck-type D-CAP are analyzed. In order to suppress output harmonic current, duty ratio of Buck-type D-CAP is generated by means of introducing Even Harmonic Modulation (EHM). Then a selective current control strategy in multiple synchronous reference frames is adopted to track reactive power compensation current reference with nearly zero steady-state error and alleviate output current distortion with demanded harmonic components. Finally, a series of experimental results from single-phase Buck-type D-CAP laboratory prototype are provided to verify the validity of dynamic reactive power compensation and almost sinusoidal output current waveform optimizing method.