Nonlinear Current-Limiting Control for Grid-tied Inverters

A current-limiting controller with nonlinear dynamics is proposed in this paper for single-phase grid-tied inverters. The inverter is connected to the grid through an LCL filter and it is proven that the proposed controller can achieve accurate real and reactive power regulation. By suitably selecting the controller parameters, it is shown by using the nonlinear input-to-state stability theory that the inverter current remains below a given value at all times. This is achieved without external limiters, additional switches or monitoring devices and the controller remains a continuous-time system guaranteeing the boundedness of the system states. Guidelines for selecting the controller parameters are also given to provide a complete controller design procedure. Simulation results of a single-phase grid-tied inverter are presented to verify the desired power regulation of the proposed controller and its current-limiting capability.