Higher-Order Sliding Mode Control for the Fully-Actuated LCL Grid-Connected Inverter

In renewable energy grid-connected power generation systems, LCL grid-connected inverters demonstrate outstanding high-frequency harmonic suppression performance. However, LCL inverters constitute complex third-order coupled nonlinear systems, making precise parameter tuning difficult with traditional PI control and failing to effectively address inherent resonance issues. To address this challenge, this paper employs fully-actuated control theory to reduce the order of the LCL inverter system model, thereby simplifying controller design. Based on this theory, a high-order fully-actuated (HOFA) model for the LCL grid-connected inverter system is derived. To enhance system dynamic response performance, this paper proposes a high-order sliding mode control (HOSMC) strategy to regulate the HOFA model of the LCL inverter system. Simulation results demonstrate that compared to conventional PI control, this strategy significantly improves grid-connected current control accuracy, accelerates system dynamic response, enhances disturbance rejection capability, and improves steady-state power quality. It also effectively reduces controller design complexity, making it more suitable for applications demanding high grid-connected power quality and robust control performance.