A multi-resonant sliding-mode controller for single-phase grid-connected inverter with LCL-filter

Sliding mode control (SMC) is recognized as robust controller with a high stability in a wide range of operating conditions, however it suffers from chattering problem. In addition, the sliding surface that is a linear combination of the system state variables and the generated references would drift while the system parameters change or external disturbance exists, which affects the tracking error and THD of system output seriously. In this paper, a fixed switching frequency multi-resonant SMC (MRSMC) is proposed for single-phase grid-connected inverter. The chattering problem of SMC is eliminated by adopting Gao´s reaching law and the parameters of SMC are optimized according to the ripple of the system output based on pulse width modulation (PWM). In order to fully eliminate the grid current tracking error and suppress its THD effectively, multiple resonant terms of the grid current error are added to the sliding function. Simulation and experimental results on a 5-kVA single-phase grid-connected inverter prototype show the effectiveness of the proposed control strategy.