Modeling And Simulation Of Doubly-Fed Induction Wind Power System

With the development of various types of wind power generation, it is generally accepted that double fed induction generation(DFIG) plant plays a significant role as the main model for it can achieve variable speed operation with a converter of relatively lower capacity. However, due to the limited capacity of converters which is the key equipment to realize the control of DFIG, DFIG wind turbines may require proper control strategy against over rotor currents or over voltages in the DC-links.This paper focuses on the deduction of mathematical model including different subsystems of the DFIG from the basic partial differential equation under the three-phase static coordinate system and two-phase rotating coordinate system. A detailed study of the vector control strategy and direct torque control strategy is carried out on both rotor converter and grid converter, which is also obtained the efficient decoupling of the nonlinear active power and reactive power, laying a solid foundation for simulation and analysis in the future works.Based on the above theoretical analysis, this article builds a 1.5MW DFIG simulation model by applying the Matlab/Simulink. The analog simulation experiments are subsequently carried out when the wind speed mutates for the maximum power point tracking control, which verifies whether the VC or DTC can achieve the maximum power point tracking control target. The simulation result illustrates the point that DTC have good dynamic response speed and low steady-state error. Then this article makes a dynamic simulation study under both symmetrical and asymmetrical grid fault. The simulation results are compared between VC and DTC, which show that both strategy have considerable endurance ability confronting the grid fault impact. The performance characteristics achieved by both vector and direct control philosophies, can be categorized as very similar, making them two main valid solutions for DFIG. It is also seen that, under these circumstances, the required rotor current and the DC bus voltage by DTC exceed the limit but less severely than in the VC. The oscillation of second harmonic generation can also be effectively restrained both under vector and direct control philosophies.According to the test standard of IEC for velocity-power characteristic curve, experiments are carried out considering the influence of the complex terrain and other circumstance characteristics. A set of experimental data measured by wind measurement lidar instead of traditional mechanical anemometer is to raise to plot the velocity-power characteristic curve, thus proving that the model established is correct and valid.