PRI Control Methodology for Grid-connected Inverters in Harmonic Distorted Grid Utility

The impacts of grid voltage on grid current in distributed generation grid- connected inverters are analyzed, and a control strategy that can compensate harmonics and suppress DC bias is proposed. In comparison with traditional PR controller, the proposed PRI controller with an additional integral part obtains a higher gain in low frequency, and the controller has an apparent effort especially for suppressing DC bias. Finally the PRI controller is verified in a 50KW. The experimental results show that the PRI controller not only can reduce harmonics of grid current in the steady state but also can suppress DC bias rapidly in a dynamic process. The PRI controller is suitable for DGs since they typically contain low order harmonics which caused by nonlinear l three-level inverter loads.