Analysis of a hybrid controlled three-phase grid-connected inverter with harmonics compensation in synchronous reference frame

The power quality of three-phase grid-connected inverters has drawn attention with the increasing numbers of distributed generation systems. In order to effectively eliminate the harmonics in output currents, a hybrid system based on proportional-integral (PI) control and repetitive control (RC) implemented in the synchronous reference frame (SRF) is presented. Based on the reference frame transformation, the use of a repetitive controller is not for achieving fundamental reference current tracking but attaining the harmonics compensation, which is different from the RC designed in a static reference frame. In addition, analyses of the SRF-based hybrid controlled converter system, including stability constraints, harmonics rejection principles and the relationship between the PI controller and repetitive controller, are further developed in frequency domain and time domain. Finally, experimental results are demonstrated to validate the steady-state and dynamic performance of the proposed hybrid controlled system.