Research On Low Voltage Ride Though Capacity Of Doubly-Fed Wind Power Generator Based On The Accurate Model

As the wind increased in power ratio, countries in the world pay more and more attention to stable operation of wind power system. Currently, power quality, reactive power control and voltage stability problems of grid wind power systems become the research hotspot. In particular, the capacity of LVRT(Low voltage ride though) is extremely important to system stability.In this paper, the basic principle of the doubly-fed generators is formulated, the mathematical model of two-phase rotating coordinate is deduced through the mathematical model of three-phase static coordinate to laid a certain theoretical basis for establishing simulation models and implementation vector control strategy. Then, a new precise model is established based on traditional stator flux oriented vector control strategy for grid. Besides, the doubly-fed wind power system dynamic behavior is analyzed in detail, and the expression of the transient DC component of the stator current is deduced in the voltage drop. What's more, with the running track of stator flux, relevant factors which affect rotor over-voltage and current are cleared, and some useful conclusions are drawn. Again, the selection of resistance of Crowbar protection circuit is analyzed in detail in the grid voltage serious drops. At last, based on DFIG(Doubly Fed Induction Generator) for two-way flow of energy requirements, DFIG is controlled by dual PWM inverter, whose energy can be two-way flow. In order to solve the problem of simulating wind turbine in lab, VVVF (Variable Voltage and Variable Frequency) asynchronous motor which simulates wind turbine is adopted to experiment.In this paper, digital control of the experiment and software programming and debugging of precise model grid-connection generation control strategy are achieved by digital signal processor TMS320LF2407A DSP. Finally, the experiment is done in laboratory 11 kW DFIG wind simulation system platform, and experimental results show the feasibility and correctness of the used control strategy.