Power controller design and stability analysis of a photovoltaic system with a dc/dc boost converter

The challenging issue of designing stable active power controllers for photovoltaic (PV) systems interfaced to the load with dc/dc boost converters is addressed in this paper. In particular, exploiting the inherent voltage and current ripple of power converters, a new proportional-integral (PI) controller with error variable the power-voltage gradient is proposed which is capable to ensure maximum power point (MPP) operation. Taking into account the nonlinear model of the PV source and the accurate nonlinear dynamics of the dc/dc boost converter an extensive stability analysis is addressed. Based on the singular perturbation theory and Lyapunov´s direct method, it is proven that for appropriate values of the PI controller gains, stability and convergence to the MPP can be guaranteed. The excellent performance of the proposed PI controller is evaluated through simulations results and it is compared with the commonly used perturb and observe algorithm and the conventional MPP method based on ripple correlation control.