Research On The Doubly-Fed Wind Generator Direct Torque Control System

With the increasing scarcity of the Earth's resources and the gradually serious environmental problems, wind as a renewable green energy has got wide attention all over the world. Wind power is developing at an unprecedented pace, and the wind power technology has also become the study focus across the world. At present, the doubly-fed generator with its unique technological advantage has become one of mainstream model of wind-driven generator which connect with grid directly. The direct torque control technology has become a major control strategy among the double-fed generator control strategies. This paper mainly aims at the direct torque control technology of the double-fed wind power generator.Firstly, the overview of the doubly-fed wind turbine technology and Direct Torque Control Technology Research is summarized comprehensively in this article. The problems exist in traditional direct torque control technology are stated as well. This paper discusses in detail the power of the wind turbine characteristics and the operation of doubly-fed generator principles and characteristics. Besides, it also analyzes theoretically the mathematical model and the energy flow of the doubly-fed generator. At the same time, problems such as poor low-speed performance, torque ripple and unfixed switching frequency that exist in the traditional direct torque control system are discussed thoroughly, laying a theoretical basis for further research.Secondly, this thesis represents the traditional direct torque control principle of doubly-fed wind power generator in-depth, and traditional direct torque control system of poor performance, low-speed, torque ripple, switching frequency is not fixed and so on, reference voltage space vector (SVPWM) estimation. This control method firstly estimates the reference voltage through the flux and torque errors, and then takes use of SVPWM modules to modulate the switching signal. Next, it sends the switching SVPWM modulation signal to the rotor-side inverter, so as to achieve the direct torque control of the rotor side of the generator.Finally, the soft of PSCAD is adopted in this paper to simulate the traditional and the improved methods. The simulation results show that the control system has a collection of advantages that the torque is small, the voltage and current waveforms is improve, the response speed is fast, the operation is smooth. The improved system makes up for the deficiencies of conventional DTC control and can better track the value of flux and torque error to select the suitable space voltage vector in order to eliminate errors, thus achieving satisfactory control effect. The improvement approach can improve the problems in the traditional direct torque. Thus it is feasible and has a certain guiding significance on the actual system design and debug.