Sliding-mode control in dq-frame for a three-phase grid-connected inverter with LCL-filter

The three-phase LCL-filter-based grid-connected inverter (LCL-GCI) is a third-order and multivariable system, and claiming a higher demand to the control system design Aiming at this, an improved current sliding mode control (SMC) strategy combing with capacitor current feed-forward control is proposed to eliminate the distortion of the grid current for a three-phase LCL-GCI control system. Meanwhile, the modified exponential reaching law is presented to effectively alleviate the shaking shock effect caused by the traditional SMC strategy. The detailed theoretical analysis and design method of the proposed SMC strategy are presented. A simulation model and hardware-in-the-loop experimental platform on a 50kW three-phase LCL-type grid inverter is built with Matlab/Simulink and RT-LAB, which are compared with the traditional control strategy for verifying the accuracy of the proposed SMC strategy. The simulation and experimental results show that with the proposed SMC strategy, the steady and transient performances of the grid current are effectively improved. (C) 2020 The Franklin Institute. Published by Elsevier Ltd. All rights reserved.