Recent Advances in Converter Control Techniques for Wind Energy Conversion System

Over the last few decades wind energy has emerged as one of the fastest growing mainstream power technologies due to its low cost and environmentally friendly nature compared to conventional fossil fuel based power generation. Considering available options of state-of-the-art generator technologies in wind energy conversion system (WECS), doubly fed induction generator (DFIG) has become popular because of its economic operation, ability to regulate in sub-synchronous or super-synchronous speed and decoupled control of active and reactive power. Harnessing regulated power supply from unpredictable wind blow, extraction of maximum power from intermittent generation and supervision on nonlinear system dynamics of DFIG-WECS are some of the critically challenging issues for wind energy system. Maximization of the power yielded from wind turbine is possible by optimizing tip-speed ratio, turbine rotor speed or torque and blade angle. Traditionally, maximum power point tracking (MPPT) control algorithm is based on the Hill Climb Search (HCS) method due to its simple implementation and turbine parameter-independent scheme. Since the conventional HCS algorithm has few drawbacks such as power fluctuation and speed-efficiency trade-off, a new adaptive step size based HCS controller is developed in this work to mitigate its deficiencies by incorporating wind speed measurement in the controller. Again, conventional feedback linearization controllers are sensitive to system parameter variations and disturbances on grid-connected WECS, which demands advanced control techniques for stable and efficient performance considering the nonlinear system dynamics. An adaptive backstepping based nonlinear control (ABNC) scheme with iron-loss minimization algorithm for DFIG is also developed in this work to obtain both improved dynamic performance and reduced power loss. In order to verify the effectiveness of the proposed control schemes, simulation models are designed using Matlab/Simulink. The proposed MPPT control, nonlinear control for grid-connected mode of DFIG-WECS has been successfully implemented in real-time using DSP controller board DS1104 for a laboratory 350 W DFIG. In the laboratory environment a 4-quadrant dynamometer is used to emulate the wind turbine to provide variable wind speed to the generator. The performance of the proposed ABNC is also compared with the benchmark tuned proportional-integral (PI) controller under different operating conditions such variable wind speed, grid voltage disturbance and parameter uncertainties and it exhibits excellent grip over the rotor side and grid side converter control. Virtual: https://events.vtools.ieee.org/m/283915