Inherent correlation analysis and verification of typical hybrid repetitive controllers for grid-connected inverters

In polluted grid, hybrid repetitive controller (RC) is an effective way to suppress the current distortions of grid-connected inverters. Typical hybrid RCs are usually divided into two types: plug-in RCs and parallel-type RCs. However, existing research claims that the stability of parallel-type RC is worse than that of plug-in RC, of which the analysis method is conservative. In addition, it is difficult to find the stability boundary and obtain the optimal control parameters by conventional design methods. In this paper, inherent correlation analysis of typical hybrid RCs are carried out, clearly addressing the control coupling effects within controllers and proves that the parallel-type RCs can also realize the same performance through correct parameter design. Furthermore, the generalized stability boundaries of typical hybrid RCs are obtained in this paper, which is conducive to guiding hybrid RCs design. Moreover, to increase the dynamic response of a converter in abc coordinates, proportional, resonant controller and repetitive controller (PR-RC) is used as an example. The results of parameter design and experiment are presented to verify the inherent correlation analysis of typical hybrid RCs.