Nonlinear Current Control Scheme for a Single-Phase Grid-Connected Photovoltaic System

This paper presents a new nonlinear current control scheme for a single-phase grid-connected photovoltaic (PV) system. The controller is designed using partial feedback linearization which linearizes the system partially and enables the controller design scheme for reduced-order PV systems. The reference current is calculated from the maximum power point tracking system. The proposed current control approach introduces the internal dynamics and the stability of the internal dynamics is a key requirement for the implementation of the controller. In this paper, an energy-based Lyapunov function is used to analyze the stability of internal dynamics of a PV system. The performance of the controller is evaluated based on the tracking of grid current to the reference current by considering the changes in atmospheric conditions. To ensure the suitability of the proposed controller in a real system, a large system similar to a practical system is simulated under different operating conditions such as changes in atmospheric conditions and faults on various parts of the system and compared with conventional controllers. The experimental validation of the proposed control scheme is also presented in this paper.