Robust repetitive current control of two-level utility-connected converter using LCL filter

Abstract

This paper investigates the implementation and performance limits of conventional and odd-harmonic repetitive controllers used for current control of two-level gridconnected inverter. This research is motivated by the relatively poor performance of classical (PI) controller when utility voltage has high harmonic distortion. Repetitive controllers (RCs) have the ability to track or reject periodic signals. However, their effectiveness is limited severely by the scarce bandwidth of the plant. To address this issue, the relationship between plant bandwidth and the converter’s LCL filter is also investigated. In addition, the effects of variation in parameters of low-pass filter used in RC loop on the performance of the system are studied. Odd-harmonic repetitive controller (ORC) is used to overcome the excessive memory requirement in RC implementation. The performance of RC and ORC is tested for different total harmonic distortion (THD) values of utility voltage. The results show that RC improves steady state error and THD of the output current. Also, RC is found to be robust under variations in output-side inductance. Keywords: Repetitive controller, Odd repetitive controller, Capacitive current feedback, Two-level converter, Plant bandwidth, Smart grid