Design and analysis of repetitive controllers for grid connected inverter considering plant bandwidth for interfacing renewable energy sources

The plant bandwidth plays a vital role in the design of any feedback controller. Its importance is more for repetitive controller (RC) based systems because it is required to provide higher gains at desired frequencies. This paper discusses design of the repetitive controller (RC) for a LCL filter based grid connected inverter with special emphasis on plant's bandwidth. The relation between plant bandwidth and the capacitor value of the LCL filter is also investigated. The effectiveness of the repetitive controller for different plant bandwidths is tested in the presence of different utility voltage harmonics and uncertainty in utility impedance. The results show that a suitable value of the capacitor in LCL filter must be selected in order to provide enough bandwidth for the repetitive controller to be effective.