Research On Direct Torque Control For Brushless Doubly-fed VSCF Wind Power Generator

With the rapid economic development,energy consumption is increasing every year, conventional energy resources are facing the dilemma of increasing depletion,it need some clean,pollution-free,renewable new energy sources urgently.Among the many renewable energy and new energy technology development,wind power has its own unique advantages, and great development value.The control of wind turbine technology is one of the key technologies,it affect the safety and efficiency of the unit directly,VSCF power generation system can maximize the use of wind energy,improve the operating efficiency of wind turbines, it is a highly efficient energy conversion system.they have been widely used.Brushless doubly-fed wind generator is particularly suitable for variable speed constant frequency wind power system,research on the brushless doubly-fed VSCF wind turbine control technology,it can improve the use of BDFG in the field of application of wind power, it has important theoretical significance and value in use.In this paper we has studied the brushless doubly-fed wind generator and direct torque control strategy,and direct torque control strategy.First we analyze the electromagnetic theory of brushless doubly-fed generator,introduce several operating mode of the generator,it includes asian synchronized,synchronization,super-synchronous and so on.we study the relationship between the electromagnetic and energy flow between them.then analyze the brushless doubly-fed generator under three phase stationary reference frame model,give the two phase rotating system mathematical model under the coordinate transformation theory,and on the basis,we give the brushless doubly-fed generator mathematical model base on the coordinate system on the control.To to meet the brushless doubly-fed wind generator torque control system dynamic response speed,good control performance,for traditional direct torque control,it use hysteresis controller to control the flux and torque,it has a lot of problems,for example:limited hysteresis adjustment,low-speed torque pulse and inverter switching frequency is larger.in this paper we use fuzzy control for direct torque controlling,then design the direct control based on fuzzy in direct torque control system.we use fuzzy controller instead of using the torque,flux hysteresis controller respectively,then optimize fuzzy control rules with the genetic algorithm.it can reduce the flux and torque control of tolerance.Simulation results show that the method can reduce the torque ripple and improve the control performance of the system.Using fuzzy control to establish generator inverter switching state,it can chose voltage space vector responably,and the torque ripple is smaller,it can improve the dynamic performance of the generator. The key for the direct control is the proper control of flux,according to the problem of the brushless doubly-fed generator at low voltage,we can see that the generator how to control the flux vector which led to system oscillation.The article is designed based on adaptive identification of direct torque control strategy. Control winding flux model use reference adaptive observe model,we use improved torque hysteresis comparator instead of the torque hystesis controller.Simulation show that the current waveform is lower in the peaks and troughs,flux recognition accuracy,it verify that the method is feasibility and correcrness.