Various control schemes for voltage source inverter in PV grid interfaced system

Abstract

Over the years, power converters have found wide application in grid interfaced systems, including distributed power generation with renewable energy sources. In distributed energy systems like solar, hydro or any diesel generation where the output of the system is DC and is expected to be converted in AC, an inverter is used. There are various modes to have a controlled output of inverter. The paper consists of the comparative study of three phase Voltage Source Inverter control schemes. The different control methods used are PI controller, PR (P + Resonant) controller. In PI control, the stationary reference frame is used to transfer the feedback quantities, where the decoupling of component requirement increases complications. To avoid these complications, a new Proportional resonant control strategy is employed, in which, a second order very high gain (ideally infinite gain) is introduced at fundamental frequency. The main advantage with this controller is the reduction in steady state DC error. PR controller is adopted in the outer loop alpha beta coordinates to avoid complicated decoupling process. The PI controller is adopted in the most familiar dqo reference frame. The three phase system is simulated in the matlab-simulink environment with both the controllers and experimental results are given to prove the correctness and feasibility of the system. On the basis of results also, these two controllers are compared.