Research On Power System Stability Of Wind Plant To Power Grid

With the development of low-carbon economy, the wind power as a clean andpollution-free power generation mode will expand in the proportion of the powersystems. But, the volatility, randomness and other features of wind energy and thedifference between wind turbines and traditional synchronous generators will have amajor impact on power system stability. Therefore, the research on power systemstability of different types of wind turbines connecting with the grid is necessary andmeaningful. In this paper, a computer simulation platform is used to investigate theimpact of three types of wind turbines which are constant speed wind turbine(CSWT),doubly fed induction generator(DFIG) and direct drive synchronous generator(DDSG)respectively on transient stability and small signal stability.The main contents of the research analyzed the subject by using aMATLAB-based power system analysis toolbox PSAT, and also found the differentimpact on power system of three wind turbine types. The main work and conclusionsare focused on the following three aspects.Firstly, the study of low frequency oscillation mode and its characteristics wasmade when power system has wind plant in it. By analyzing a strongly coupled tworegional system example, it can be argued that some good damping properties stronglycorrelating with wind farm of oscillation modes can be gotten when the traditionalsynchronous generators are replaced by wind plants of the three types.In order to analyzing the damping characteristics of the system further, a tworegional increasing wind penetration power example was introduced to research thesmall signal stability. With wind penetration power increasing, the change of originalsynchronous generator interval or local oscillation mode is seldom, while theoscillation characteristics are changed. When penetration level increasing, CSWTsystem will improve its oscillation characteristics, the damping of new added localoscillation mode in DFIG system will be weakened. DDSG system will improve thelocal oscillation damping related to wind plant.Secondly, according to the existed mathematical model of wind turbine, thefactors which affect dynamic stability of constant speed wind turbine was discussed.The roles of shaft process and generator parameters concerned with CSWT dynamicstability were analyzed. The methods are obtained that improving the shaft stiffness coefficient Ks, the rotor resistance Rrand reducing the stator reactance Xs, the rotorreactance Xrwill enhance its dynamic stability.Finally, the validity of the equivalent wind turbine in PSAT was verified.based ona39buses network simulation example with wind plant in it, the different effects ontransient stability was compared among the three wind turbines access to powersystem. The conclusions are drawn that the CSWT has the greatest impact on transientstability with the traditional synchronous generators close to it in electrical impedance,DFIG and DDSG are better than CSWT on transient stability to power system.