A Novel Control Strategy for a Single-phase Grid-connected Power Injection System

In this paper, a novel and simple control approach to controlling the power injection system (PIS)using state feedback is proposed. The PIS is composed of a DC voltage source, a voltage sourceinverter (VSI) and an L-C-L filter. The DC source is a battery with boosted voltage. The battery can becharged with photovoltaic cells. Since the grid voltage acts as a disturbance, the state space model ismodified to reject the disturbance. The minimum necessary input DC voltage is also calculatedaccording to specified injection power. Moreover, to avoid measurement problems such as noise andcost, an observer is designed. The major problem with single-phase PISs is the injection of some DCcurrent with AC current. We show that the proposed controller not only performs near perfect tracking, but also eliminates the DC current injected into the grid. Further, a Proportional-Resonant (PR) controller is designed and applied to the PIS for comparison. Simulation results show that the proposed method has significant advantages over the PR controller such as simple realization and application, low overshoot, no DC offset at the output current and fast response. The simulations are performed using average and accurate models of PIS. The results confirm the advantages of proposed method over PR controller.