Dynamic analysis of a DC offset controller for grid-connected inverters

DC injection limits into the AC network are an important power quality control requirement for grid-connected photovoltaic systems. Most publications on DC offset controllers focus only on their steady state performance. It is important to consider their dynamic performance especially in terms of speed of response and stability. In this paper a mathematical model for a digitally implemented DC offset controller is derived. A design procedure, based on the model, is proposed for the controller. Results of tests performed on a system of 1kW nominal rating, provide validation for the mathematical model.