Research On The Control Of Direct-Drive Permanent Magnet Wind Turbine Generator System

The limitation of fossil energy always is a great proposition of the sustainable development, the whole world set a high value on environmental protection, people has paid much attention on wind energy due its abundant resources, cleanliness and no pollution. The models and the topological structures of wind power generation are in a variety styles. Direct-drive permanent magnet synchronous motor doesn't need gear box, it have characteristic of low noise, run stably, low cost of maintenance. It presents the development direction of future wind power industry.First of all, the paper analyzes the domestic and foreign wind technology in the current development situation, and then briefly introduces several common topologies. In this paper, we select dual PWM control structure, can independent control the grid-side converter and the generator-side converter.On this basis, this paper introduces the basic principle of field orientation control and three common-used types of coordinate, and the principle of SVPWM converter technology; And then analyses the three-phase voltage source PWM converter's basic principle, the mathematical models of grid-side converter and the generator-side converter in Three-phase static coordinate and two-phase synchronously rotating coordinate are established, according to the principles of maximum power point tracking(MPPT), the generator-side converter's particular method is double-loop control mode, take electric circuit as inner loop, and the outer loop of the double-loop speed control strategy, the grid-side converter in due to realize unit power factor control, it uses double-loop control mode too, but the outer loop using voltage instead; Finally, to resolve the problem of grid voltage symmetrical sag, adds a damping load at DC-side, the ability of LVRT can be improved.With comprehensive consideration of the actual situation as well as the theory research, a simulation model of the wind turbine generator system is built in Matlab/Simulink. Then the system is operated in both static and dynamic condition, the simulation results confirm the correctness of the control strategy. Moreover, the system proposed in this paper can realize the control objectives pre-established with good control ability.