New dual-mode variable step-size control strategy for quadratic boost converter used in solar energy system

This paper presents a new control strategy based on Lyapunov theory used to control a quadratic boost converter used in solar energy system. The proposed controller assures the stability of the system. To provide a maximum power extraction, a maximum power point tracking (MPPT) is included in the controller. First a simple MPPT algorithm based on the fact that the derivative of the power with respect to the voltage at the output of the solar panel is null when the operating point is the same as the maximum power point (MPP) is integrated in the controller, then we will propose a modified version of the algorithm operating in dual-mode with a variable step-size. The proposed controller is tested by simulations using Matlab/Simulink™ with both MPPT algorithms. The proposed dual-mode variable step-size algorithm has proved its advantage compared to the simple one. It gives a smoother output, therefore decreases power losses. The proposed controller is compared also to a conventional perturb and observe (P&O) controller. The comparison has proved that the proposed controller has a smaller response time, a lower steady-state error and a more stable operating point.