Research On Controlling Measures To Enhance Low Voltage Ride Through Of Wind Farm With STATCOM

Under the threat of environmental pollution and energy crisis,all countries around the world are seeking to developing renewable and cleaner energy sources.Among them,wind power has become vigorously advocated around the world at present.Because it has the advantages of low cost and more familiar technology.The development of wind power in our country is rapid and the installed capacity has also been gradually increased,at the same time,the grid-connected wind farms have been expanding. Therefore,the various problems about voltage stability caused by large scale wind power injected into the grid system have to be addressed.At present,the tripping accidents of wind farms have happened frequently,which seriously restrict wind turbines from connecting with the grid at large scale.Based on popular double fed wind turbine,the low voltage ride through characteristics is discussed in detail in this paper.Firstly,based on the tripping accident of wind turbines, the complete development process and the influence on wind farm are described.The reason of the accident is also analyzed in detail.It concludes that compensation equipment of reactive power(STATCOM) has significance on stable operation of wind turbines.Secondly,this paper introduces the fundamental structure and operation theory of the double fed machine, mathematical models of DFIG based on abc and dq0 coordinate system are elaborated.The controlling strategy of both grid side converter and rotor side converter which will be used in the following simulation model are described.Thirdly,the principle and mathematical model of STATCOM is investigated,In addition,two typical control schemes about STATCOM are analyzed.Fourthly,based on MATLAB/Simulink environment,simulation system of DFIG are built.By simulation of the DFIG dynamic responses under different degrees of voltage drop, in the case of 80% and 20%It proposes that using STATCOM dynamic reactive power compensation device in the case of 80% and add ing the STATCOM and Crowbar in the case of 20%.These controlling strategies are finally confirmed to improve the low voltage ride through.In addition,the principle of Crowbar protection circuit is introduced, the influence of the value and disconnection time on the performance of low voltage ride through are also analyzed.