Study On Control Strategy Of Doubly Fed Wind Power Generation System Under Unbalanced Grid Voltage

With the rapid development of society,human dependence on energy is getting more and more higher.But with the fossil energy depletion,it is urgent from the fossil energy-based single energy structure to renewable energy as the representative of the diversification of energy structure transformation.As the wind energy is rich in resources,widely distributed,clean and so on,and its associated power generation technology has been rapidly development.The advantages of low cost,stable operation and simple control of doubly fed motor are widely used in realistic wind power generation system.In this paper,the doubly fed wind power generation system under voltage unbalance is studied deeply.In this paper,the mathematical model of grid-side converter and rotor-side converter is established,and the influence of unbalanced grid voltage on the two-side converter is analyzed by symmetrical component method.At the same time,a sampling algorithm of sinusoidal sampling sequence is proposed to carry out fast and accurate positive and negative sequence separation in the unbalance of the network side converter.Under the unbalanced voltage of the grid,the control target of the network side converter and the coordinated control of network side with the rotor-side converter are not only analyzed,and the control target of the rotor-side converter is also analyzed.According to the double dq-PI control method,the dual dq-PI controller of the network side and the rotor side converter is designed.The passive control of the grid side converter and the rotor side converter control are verified under the unbalanced grid voltage.On the basis of passive control method,a nonlinear controller under the two sides of the converter is designed on the grid voltage unbalance.In the environment of Matlab/Simulink,the two controllers of the network side converter and the rotor side converter are simulated and compared to verify the effectiveness of the nonlinear controller designed.As far as possible to achieve a coordinated control target between the network side and the rotor side converter,a coordination controller is proposed,and the nonlinear passive controller of the converter on both sides in the coordination control method is adopted.The different control targets in the environment of Matlab/Simulink is simulated and compared,and the correctness of the passive nonlinear controller in the coordinated control is verified.At the same time,through the coordinated control of the two sides of the converter,the more control objectives can be achieved,and the entire wind power system operating performance is improved on the grid voltage unbalanced conditions.