A Synergetic Control Approach to Grid-Connected, Wind-Turbine Doubly-Fed Induction Generators

The doubly-fed induction generator (DFIG) with back-to-back four-quadrant power converters between the rotor side and the stator side can realize an efficient and flexible conversion from wind energy to electric energy. Based on the stator-flux orientation control strategy, this paper aims to introduce a synergetic control synthesis method and applies this method in the control of the DFIG's rotor-side power converter. Synergetic control synthesis of the rotor-side power converter is based on a simplified induction machine model. The dynamic characteristics of the synergetic controller are studied in a typical grid-connected wind energy conversion system. Four typical scenarios are studied, where the active power setpoint, reactive power setpoint, grid voltage and input wind mechanical power undergo a step change respectively. Comparing the dynamic responses under the synergetic control law to those under the PI control, this paper concludes that the synergetic control has better dynamic performance than the traditional PI control in regulating the output power of the doubly-fed induction generator in the grid-connected mode by controlling the rotor-side voltage source converter.