The Optimization Strategies For Parallel Operation Between Doubly-fed Variable Speed Constant Frequency Wind Turbines And Grid

Doubly-fed variable speed constant frequency wind turbine is the mainstream type in wind power, and its grid side converter and rotor side converter adopt the traditional control strategies based on the grid operating under normal conditions. However, with the increased penetration of wind power generations in power system and developed modern grid codes concerning grid-connected wind turbines, the researches on wind power have changed from grid normal operating to wind turbines riding through under abnormal grid conditions. Based on the structure characteristics of doubly-fed variable speed constant frequency converter, two aspects (grid side converter and rotor side converter) have been studied. First of all, the characteristics of grid side converter and rotor side converter were analyzed. According to their topological structures, the mathematical models and the control strategies were built. Then the mathematical models of grid side converter and rotor side converter under three-phase static coordinate system, two-phase stationary frame and two phase synchronization reference frame were established, and analyzed the instantaneous active and reactive power components of stator output power. As the positive and negative double currents control strategies have many shortcomings, this paper put forward a new unbalanced control strategy based on the forecasting methods innovatively. In view of the different voltage dips, the rotor side converter used improved control strategy and increasing hardware circuit (crowbar) method respectively to realize the ride through. The models are simulated in PSCAD and RTDS, and the results illustrate that the methods presented in this paper are correct and provide reliable reference to practical engineering.