Research On The Control Technology Of Converter DFIG Unbalanced Voltage

As the main wind power technology, the double-fed wind generation technology is widely applied in engineering practice at present. But with the increasing of the capacity and the penetration of wind power, the requirement of operation control ability for wind generation when synchronizing with the main power system is higher. The wind generator designed on the base of ideal power environment and its operation strategy can not apply to the practical power system any more, especially when the grid occur asymmetry power fault. So they can’t meet the synchronizing and high operation requirement, which as a result will decrease the power quality and stability of the power system. This thesis study the control strategy of the double-fed asynchronous generator power under unbalanced voltage fault when synchronizing with the main power system.Firstly, the basic structure of the double-fed asymmetry wind generator and its main function of the main elements are introduced. The mathematical model of the net side converter and the rotor side converter under the synchronous speed rotating coordinate system is established. Then the PI controller based vector control strategy of the stator voltage oriented vector under the condition of ideal power grid is analyzed in detail.Secondly, the control goal of how to increase the operation ability of net side converter under unbalanced voltage fault is studied. And its dynamic mathematical model is established, the control algorithm is designed and the net side current reference value is selected. The principle and characteristics of the resonant controller is studied, and then take the advantage that the resonant controller can achieve zero static error control of the AC signal to design the net side converter control system under the two-phase static coordinate, which can realize the decoupling power control, simplify the coordinate conversion and the structure of the low level harmonic compensation.Finally, the dynamic mathematical model of rotor side converter and DFIG is established. The control aim to improve the DFIG’s operating state is put forward. The vector control system of the resonant controller based rotor convertor is designed. Then the control theory of rotor current zero static error is verified in the MATLAB/Simulink by the DFIG model. The simulink result prove that, comparing with the conventional PI controller, the vector control system which is based on the proportional resonant controller can achieve more realistic system structure, faster and more precise current regulation ability and better dynamic response character under the unbalanced voltage fault. The thesis’s research conclusion can contribute to the double-fed wind generator operation control to some extent.