Direct Torque Control Strategy Of Brushless Doubly-fed Generator For Variable Speed Constant Frequency Wind Power System

For variable speed constant frequency (VSCF) brushless doubly-fed wind power generation system, a control system is designed based on the relationship between the maximum absorption power and speed of the brushless doubly-fed generator(BDFG) in this paper, Science and Technology Tackling Plan of Liaoning Province "High-reliable stator brushless doubly-fed wind power generation motor and its slip frequency excitation control stsyem" (Project Grant No.:2010220029) as the background. Direct torque control (DTC) algorithm is completed, acting DSP2812 as the core of the control system. The given generator torque is obtained according to the principle of maximum wind energy capture, which makes the control system meet the requirements of wind power generation.Firstly, the development status of wind power generation technology and control technology of BDFG are analyzed, which demonstrates the superiority of BDFG applied to wind power generation.Secondly, the working principle of BDFG is analyzed according to it mathematical model, and the power flow and energy relationships of BDFG are analyzed. Based on this, the fundamental control of the brushless doubly-fed wind power generation system is determined, namely, VSCF generation and the maximum wind power capture principles, and its realization method also is discussed. The advantages of BDFG is utilized to realize VSVF generation, that is, VSCF generation is ensured by adjusting control winding frequency of BDFG with the wind speed changing. Through the research of the relation of maximum absorbed power and speed of BDFG, the speed on point of maximum energy capture under different wind speeds is obtained, and the given torque is achieved by adjusting the speed, in order to realize the maximum wind power capture.Finally, Simulink software is used to simulate, in order to verify the feasibility of the proposed control scheme. The simulation results show that maximum absorbed power can be not only obtained by adjusting generator torque rapidly to tracking the change of the wind speeds, but also VSCF generation can be realized through the adjustment. In addition, the hardware and software design program of VSCF brushless doubly-fed wind power generator direct torque control system is proposed, experimental platform of the control system is built, and experimental research of the proposed control scheme is carried out. The hardware part of the experimental system includes rectifier circuit, inverter circuit, switching device drive circuit, relevant protection circuit and testing circuit. DSP2812 is used as core in the software part, and the control system is programmed and debugged by CCS3.3 software. Experimental results show that the control system is stable, and it can meet the operation requirements of VSCF wind power generation basically.