A systematic design of PR current controllers for single-phase LCL-type grid-connected inverters under distorted grid voltage

Abstract

LCL-type grid-connected inverters are crucial for the integration of distributed energy resources in power grids. In order to achieve high quality of the grid current for a compliance with IEEE and IEC standards and maintain system stability, not only an LCL resonance damping method but also a proper controller design is required. This paper proposes a systematic and generalized design approach for PR controllers to stabilize the operation of single-phase LCL-type grid-connected inverters under different conditions of grid voltage. The designed PR controller contains multiple resonant components to effectively eliminate high-order current harmonics and deal with the variation of grid frequency. Phase margin is taken into account when designing the PR controller to guarantee system stability. The efficacy of the proposed method is verified by both simulation and real-time hardware-in-the-loop experiments using a Typhon HIL 402 system. The results show that the designed PR current controller is capable of significantly reducing grid-current harmonics when the system operates with distorted grid voltage. In addition, between grid-current and inverter-current feedback approaches, the former results in a grid current with a higher quality. © 2018 on-line: journal/esrgroups.org/jes.