Modelling and Control of Grid Connected Wave Energy Converter Using Sliding Mode Controller

Abstract: Wave energy is one of the most promising renewable energy sources for generating electricity. To extract energy from ocean waves, Wave Energy Converters (WEC) play an important role. One of the WEC types is the Point Absorber which is an oscillating type WEC that extracts the heave, or vertical motion from a wave. It consists of a cylindrical structure which is directly connected to the power takeoff system (PTO) which is connected to the grid through cable. The vertical motions of the point absorber compresses and expands the fluid and make the generator to rotate. The PTO system consists of permanent magnet synchronous generator (PMSG) which transforms the mechanical energy to electrical energy. The time domain simulations of point absorber are performed to evaluate the power take off capabilities of the modeled WEC. The overall system is obtained by connecting the hydrodynamic model to the PTO system. To obtain the maximum power it is required to reduce the voltage fluctuations at the grid side. Sliding Mode Controller (SMC) is implemented at the grid side to generate maximum power by reducing the voltage fluctuations. The output voltage settles at the reference value but due to high switching frequency of SMC, output voltage exhibits disturbances. Keywords: Wave Energy Converter (WEC), Power Take off (PTO), Permanent Magnet Synchronous Generator (PMSG), Sliding Mode Control (SMC).