Research on Single-phase SVG Based on DC 2nd Harmonic Feedforward and Decoupling Control

Under single-phase SVG applications, traditional control method of DC voltage was to compare the capacitor voltage directly with the reference value, by which second order harmonic was inherited together with the DC base component, and resulting grid-side non-characteristic harmonics. In this article, the model of single-phase H-bridge PWM SVG, the reasons of second harmonic of DC voltage, and the influence of amplitude and phase of the grid-side input current on the DC second order harmonic, were analyzed. To facilitate the control of active and reactive power of the converter, single-phase system was constructed with a d-q coordinate system. And grid-side current amplitude was calculated by integration. Further, for estimating value of the DC second harmonic, a method by using the grid-side current amplitude, phase, voltage amplitude and phase-locked signal was constructed. And a feedforward method by adding the 2nd harmonic estimated value is proposed. Combined with d-q coordination decomposition, single-phase SVG converter control method for independent control of reactive power is given. The method has been proved to be effective by experiments, and the DC voltage control is stable without increasing the non-characteristic sub-harmonics on the AC side.