Study On Modeling And Control Technology For Direct-drive Permanent-magnet Wind Power Generator System

Wind energy is a new kind of renewable energy, because of the widespread distribution,no pollution and high economic value,has become an important part of the economic development and energy strategy over the world, with the grid-connection capacity increases continuously, meanwhile, the power grid and penetration rate of wind power system is also rose. If the grid occurs the faults of the voltage drop,the wind generator with a large-scale will take off the grid,to ensure the safe and effective operation of the power grid during voltage drop,There will be a higher requirement for the LVRT capability of the wind turbine,in the thesis,focus on analysis and researchs related to the control strategy of PMSG. as well as enhance the ability of LVRT,Main work is as follows:Firstly,compared the advantages and disadvantages of two kinds of mainstream wind turbines, to investigate the direct drive permanent magnet wind turbine operation principle, topology structure and the better LVRT performance based on PWM back-to-back type permanent magnet direct-drive wind turbines for theoretical analysis,establishing the wind machine,permanent magnet synchronous generator ised and the mathematical model of double PMW back-to-back converter, mainly studied to pave the way for the permanent magnet direct driven wind turbine operation and control,then derived the voltage equations of two side converters.Secondly, according to analysis two side converters in wind power generation system, the control method and control object has been used in the process, local improvement of the control structure was carried out.In order to design the controlling strategies of the converter on both sides. In this thesis, based on the analysis and calculation, to solve the problem of parameter modeling of wind power generation system, the traditional control strategy and calculation method are optimized.according to the above research results, established the simulation model, on this basis,verify and analysis in the experimental modelFinally, according to compare with the different low voltage ride through projects,an ocean of analysis is carried out. Then,selected the hardware protection crowbar circuit of unloading resistance in DC side, and a new coordinated control project is cited, in which the generator output power reduction, the unloading resistance and the pitch angle control to achieve the coordination of the controleffect,to avoid the high DC capacitor voltage and the generator over speed operation,in order to provide a guarantee for the safe operation of generator and converterat the same time, controlled the frequency of unloading resistance, then the simulation model of permanent magnet direct drive wind turbine is established with the software Matlab/Simulink, and design the example, belong to two cases of slight drop and depth drop, and then, the wind turbine generator verified the capability of LVRT during the fault period. The simulation results testify that the coordinated control strategy is effectiveness and correctness.