Direct-drive Permanent Magnet Wind Power System Low Voltage Across Studies

Along with the environmental problem getting highlights and fossil energy consumption, the issue of energy is getting more and more attention. Renewable energy sources such as wind power for its recycled, no pollution, safe reliable, has made great strides in development. With the constantly growth of the grid power getting from wind, the interaction between wind power system and power grid is becoming more and more big. When the voltage sags happened in the fall, wind power generation systems need the ability to run through low voltage range.The low voltage ride through technology of the direct-drive permanent magnet synchronous generator is studied in this paper. Through the analyses of the response characteristics of the constituent parts of the full power converter when the grid voltage dip, the scheme of the low voltage ride through based on the Crowbar protection circuit which is located on the DC side is put forward, then the simulation is done to verify the scheme. The specific contents are as follows:(1) the first chapter outlines the current situation of development of wind power generation technology at home and abroad, introduce the types of mainstream wind turbines, then put forward the low voltage ride through technology of wind turbine when the grid voltage dip happens,the research status is also introduced at the same time.(2) the second chapter creates the mathematical models of the constituent parts of the direct-driving PMSG wind power system, including the models of the wind turbine、the PMSG、the gen-side rectifier and the grid-side inverter; Then discusses the operation characteristics and control strategy of the constituent parts based on the models; at last, we will verify the strategy through its simulation; laid the theoretical and practical basis for the control technologies of PMSG low voltage ride through.(3) the third chapter will give a brief introduction about the power grid voltage drop, and then analyze the response characteristics of the wind power converter DC link and network-side converter links during the grid voltage drops, provide a detailed analysis about the changes of internal voltage and current of the full-power converter current, and then simulate the response characteristics of the network-side converter during the different intensity and duration of the voltage drop fault, give a direction of the study for the protection measures the of the low voltage ride through which will be studied in the fourth chapter(4) the fourth chapter will give a specific research about the protection program of the low voltage ride through of the PMSG power system, select the program of installing Crowbar protection circuit in the DC part,which has got the most widely used and has the most mature technology,then give a analysis in much greater detail about the different implementations of the program and control strategy of the Crowbar protection circuit, provide its simulation verify its control effect; put forward a STATCOM mode, the reactive power compensation scheme for the reactive power demand. Finally give a brief introduction of the other control programs about the low voltage ride through.