The Active Disturbance Rejection Control Of Doubly-fed Wind Power Generation Grid-connection

Due to the advantages of low cost,variable speed constant frequency operation,small power slip and so on,doubly-fed induction generator(DFIG)is widely used in the grid wind power system with large capacity.PI controller is usually applied in traditional vector control of doubly-fed induction generator to achieve the grid-connection and power-generation,but PI controller depends on the motor parameters,the estimation of magnetic flux and the compensation of voltage and current cross-coupling will lower the speed of the generator in tracking the grid voltage,resulting in a deterioration of dynamic response performance and an increment of the overshoot voltage.To deal with these disadvantages,this paper proposed a control strategy of vector control combined with ADRC and apply it to the process of DFIG grid-connection.On the platform of PSCAD,simulation model are established,investigate by simulation the following three performances in/after the grid-connection processes:the generator stator voltage in tracking the grid voltage in no-load synchronization control;the generator stator current variation during the transition period of grid-connection;the power regulation after the grid-connection.Firstly,the basic structure and the variable speed constant frequency operation mechanism of DFIG were analyzed.The mathematical model of DFIG in three-phase stationary coordinates were established.Then the DFIG mathematical model in two-phase synchronous rotating coordinates system based on the theory of coordinates transformation were deduced.Secondly,the mathematical model of grid side converter were established and the control strategy were deduced according to the grid side converter’s functions and control targets,realized the target of the DC bus voltage control and unit power factor operation by using the technology of space vector pulse width modulation(SVPWM).The grid side converter’s control models were built on the simulation platform of PSCAD and the system was simulated and analyzed,the simulation results verify the correctness of the control strategy.Finally,based on the analysis of the functions and control targets of rotor side converter in/after grid-connection,the no-load synchronization control strategy and power decoupling control strategy of DFIG in/after grid-connection based on ADRC were proposed,and the ADRC strategy system was compared and analyzed with the system of PI control.On the platform of PSCAD,the simulation model were established and the systems were researched,the simulation results show that ADRC with no overshoot,fast and robust performances in the following three processes:stator voltage in tracking the grid voltage in synchronization control of no-load,the generator stator current variation during the transition period of grid-connection and the power regulation after the grid-connection,it comes to a conclusion that the control performance of ADRC is better than the traditional control of PI.