Nonlinear Adaptive Disturbance Rejection Control Strategy Based on VSG for Photovoltaic-Storage Grid-Connected Inverter

In this paper, a nonlinear adaptive disturbance rejection control (NADRC) strategy is designed to overcome the limitations of the traditional virtual synchronous generator (VSG) control method in photovoltaic (PV) grid-connected energy storage systems. This strategy utilizes exact feedback linearization and linear optimal control theory to establish a nonlinear adaptive disturbance rejection control law based on the virtual synchronous generator. It achieves zero static error control and noise adaptive stabilization of the AC link in a multiple-input multiple-output system. Compared with the simulation results of the grid-connected inverter voltage and current double closed-loop (VACDCL) strategy, the nonlinear adaptive disturbance rejection control effectively mitigates the fluctuations in load current caused by the photovoltaic energy storage module. It ensures power tracking under variable power conditions and outperforms traditional PI dual-loop control in terms of dynamic and static regulation performance as well as grid-connected current quality. Furthermore, this strategy's anti-disturbance adaptive link can quickly respond to system disturbances like frequency drift, voltage oscillations, and load current variations, thereby improving system performance.