Power output maximization for wave power generation plants using an adaptive sliding mode control

Modern wave power generation plants are capable to work in variable speed operations. These wave power generation plants are provided with adjustable speed generators, like the double feed induction generator. One of the main advantage of adjustable speed generators is that they improve the system efficiency compared to fixed speed generators, because turbine speed can be adjusted as a function of the flow coefficient to maximize the output power. However these systems requires a suitable speed controller in order to track the optimal turbine reference speed. In this work, a sliding mode control for variable speed wave power generation plants is proposed. The proposed sliding-mode control law incorporates an adaptive switching gain, which avoids having to calculate an upper limit of the system uncertainties that is necessary in the traditional sliding-mode control laws. The stability analysis of the proposed controller is provided under disturbances and parameter uncertainties by using the Lyapunov stability theory. Finally simulated results show, on the one hand that the proposed controller provides high-performance dynamic characteristics, and on the other hand that this scheme is robust with respect to the uncertainties that usually appear in the real systems.