Reserch On The Characteristics Of DFIG Wind Power System With Variable-speed Constant-frequency

At present, the energy shortage and environmental deterioration has become two global problems, there have an inevitable choice to solve this problem is that the full development and utilization of renewable energy. The wind power which is one of the most mature energy has been used more and more widely. And, the double fed system with variable speed constant frequency has becomes a research hotspot. Because of its advantages of high wind energy utilization coefficient and the output power can be regulated.First, analysis the operation principle of the doubly fed induction generator how to achieve variable-speed and constant-frequency. Through the coordinate transformation, build a two-phase rotating coordinate. Research the vector of doubly fed generator system back-to-back PWM converter control strategy based on the math model. On the basis of a model of the double fed motor vector back-to-back PWM converter control strategy based on target, to control the rotor side PWM converter and the grid side PWM converter, designed rotor stator flux oriented vector control system based on grid side grid voltage orientation vector control system. In particular, the rotor side PWM converter control system design is introduced in the hysteresis current control technology, not only simplifies the control system, but also improve the dynamic response of the system. At the same time, according to the equivalent circuit of doubly fed generator to analysis the power flow of DFIG.Second, according to the design of control system establish simulation model of the double fed induction wind power generation system in the simulation platform of PSCAD. Through the simulation of energy flow in the grid side converter and the simulation of wind change to verify the validity of the simulation model. And show that the control strategy can play a certain role to maintaining LVRT of DFIG wind power system when the grid voltage sag.Finally, build the doubly fed motor transient model and add the active Crowbar protection circuit in the rotor side. Through the simulation of model, to prove that Crowbar protection circuit can protect the doubly fed wind power system LVRT...