Nonlinear adaptive backstepping controller design for grid currents regulation of a CSI based PV system with external disturbances

Abstract

In this paper, a nonlinear adaptive controller for regulating the grid of a current source inverter (CSI) based three-phase grid-connected photovoltaic (PV) system is proposed. The proposed control structure is composed with an outer control loop-responsible for controlling the DC-side inductor current and the inner current control loop-responsible for controlling injected current into the utility grid. The proposed adaptive controller is designed recursively by considering external disturbances within the system and these unknown external disturbances are estimated through the adaption laws. The overall stability of the whole CSI based three-phase grid-connected PV system is verified by formulating the control Lyapunov functions (CLFs) at different stages throughout the design process of the proposed controller. Finally, the performance of the designed controller is tested on a similar CSI based three-phase grid-connected PV system under different atmospheric conditions. Simulation results demonstrate that the proposed control scheme can effectively meet the desired control objectives as compared to the existing controller in terms of settling time and power quality.