Nonlinear control of MPPT and grid connected for wind power generation systems based on the PMSG

In this paper, nonlinear control of permanent magnet synchronous generators (PMSG) for wind energy conversion system (WECS) is investigated in order to maximize the generated power from wind turbine. The control strategy combines the technique of maximum power point tracking (MPPT) method and sliding mode (SM) nonlinear control. A speed and pitch control scheme for variable speed wind turbines are proposed. The block diagram of the WECS with PMSG and a back-to-back PWM converter structure is established with the dq frame of axes. Both converters used the sliding mode control scheme considering the variation of wind speed. A speed controller is designed to maximize the extracted energy from the wind, below the rated power area, while the objectives of grid-side converter are to deliver the energy from the PMSG side to the utility grid, to regulate the DC-link voltage and to achieve unity power factor and low distortion currents. The employed control strategy can regulate both the reactive and active power independently by quadrature and direct current components, respectively. With fluctuating wind, the controller is capable to maximize wind-energy capturing. Under varying load condition and at constant load, the controller can maintain the load voltage and frequency quite well. The system is built using Matlab/Simulink environment. Simulation results show the effectiveness of the proposed control scheme.