The Second-Order 6k±1-Order Repetitive Control for Three-Phase Grid-Connected Inverter

The conventional repetitive control (CRC) cannot obtain ideal control performance when a large number of renewable energy are connected to the new power system. In this paper, the second-order 6
$k$
±1 repetitive control (SO 6
$k$
±1 RC) which is composed of a standard structure of SO 6
$k$
±1 RC is proposed. The control performance can be improved comprehensively in the three-phase grid-connected inverters when the proposed SO 6
$k$
±1 RC is applied, include the steady-state performance, dynamic performance, and frequency self-adaptability. Since SO 6
$k$
±1 RC can update filter coefficient online at any one time, so good dynamic response and steady-state performance are obtained, and the problem of frequency variations can be solved effectively in the three-phase grid-connected inverters. Simulation results for the three-phase grid-connected inverters controlled by the proposed SO 6
$k$
±1 RC show that good frequency self-adaptability is obtained compared with CRC/6
$k$
±1 RC.