Disturbance Rejection for LCL-Type Inverter System Based on Equivalent Input Disturbance and Generalized State Observer Method

The inverter systems have been widely used in photovoltaic microgrids. They play an important role in ensuring the stable operation of the entire power grid system. This paper discusses the disturbance rejection problem for the LCL-type inverter system with an unknown disturbance. Based on the idea of equivalent input disturbance (EID) and generalized state observer (GSO), a disturbance rejection control method is developed. This method firstly defines an EID for the unknown disturbance and designs a GSO for the EID-based system. And then, a disturbance estimator is constructed to estimate the EID. After that, a feedback controller is designed by using the internal model principle and the quadratic optimal control theory. It guarantees the robust tracking control objective of the LCL-type inverter system to be realized. Simulation and comparison results demonstrate the validity of our developed control strategy.