Design of PWM-SMC Controller Using Linearized Model for Grid-Connected Inverter with LCL Filter

Nowadays, various sliding-mode control (SMC) methods have been successfully applied to the digitally controlled grid-connected inverter (GCI) with an LCL filter. However, how to design the pulsewidth modulation based SMC (PWM-SMC) controller needs to be further explored, especially upon the large variation of the parameters drift and the delay issue. In this article, the essence of two classic SMC methods used in the power converter area is first analyzed in detail. Thus, a novel design of the PWM-SMC controller using a linearized model for the three-phase GCI with an LCL filter is proposed. Based on this, a three-loop step-by-step design of the PWM-SMC controller is developed, by using the closed-loop pole locations. A robust analysis against the parameters drift is also studied. In addition, a discrete state observer is adopted to reduce the number of sensors. Furthermore, a discussion between the proposed control strategy with the existing SMC methods and the full-state feedback controller is carried out. Finally, a 3-kW lab device designed on the dSPACE is constructed to verify the feasibility of the proposed strategy and the correctness of the theoretical analysis.