Study On Control Strategy Of Grid-connected Doubly-fed Wind Turbine Based On PSASP

Wind energy is one of the many types of clean renewable energy, thedevelopment of wind energy can help make up the deficiency of the energy andreduce environmental pollution. The most important usage of wind energy is togenerate power, which has been rapidly developed around the world. Because of therandomness of natural wind, the wind power generated is random and fluctuant,besides, the wind energy can’t be made use of at peak efficiency all the time.Therefore, it is worthy to study further on how to maximize the utilization of windenergy by regulating the speed and excitation of the generator when wind speedchanges, and how to improve steady-state performance of generator and the voltagelevel of the bus during the fault period, through optimal control to the reactive powerof the generator.This paper analyzed the working principle of DFIG, and based on the equivalentcircuit of DFIG, built the mathematical model under the three-phase stationarycoordinate system, which was then transformed to the model under two-phase rotatingcoordinate system by coordinate transformation. Though analysis of the powercharacteristics of wind turbine, this paper proposed the control strategies of DFIG, thecontrol strategy of the rotor-side converter was stator flux oriented and the controlstrategy of the grid-side converter was grid voltage oriented. Besides, the method totune parameters of the PI controllers was studied, and it turned out to work well in theprogram debugging. The strategy to optimize reactive power was also studied, duringsteady state, the reactive power control strategy was aiming at minimizing the copperconsumption of DFIG, while during the fault period, certain reactive power wasinjected into power system to improve bus voltage, the total copper consumption ofDFIG and the contact lines was minimized though optimal distribution of the reactivepower between the rotator and the stator when the total reactive power was certain.Based on PSASP/UPI and the two-area power system consisting of4generators and11nodes, simulation was done to verify strategies proposed in this paper. In thesimulation, the control strategies performed with fast response speed and good controlaccuracy. Contrast to traditional reactive power control strategy, the one proposed inthis paper can improve the bus voltage and reduce the copper consumption duringfault period.