Research On Power System Voltage Stability With The Integration Of Wind Farm

Rich resources of wind energy as a green and renewable energy, are an effective way to solve the current energy crisis and environmental degradation, with more attention and strong development all over the world. With the annual increase of wind power generation capacity,stochastic volatility of the wind power output is more obvious,which is considered as problematic to power system operation since it would cause voltage fluctuation.Large-scale wind farms connected to the grid power system adversely will affect safe and stable operation of the power system, even lead to the collapse of power grid. Therefore, in order to consider the effects, this paper works on power system static voltage stability degree and measures to suppress voltage fluctuation concerned about the wind turbines by using PSAT and MATLAB simulation platform.Firstly, briefly introduces the mathematical model of the wind generator.On the basis of comparison of various existing equivalent model, the wind speed chooses Weibull Distribution in PSAT,the wind generation the variable speed constant frequency doubly-fed induction generator(DFIG)in this paper,building a single simulation model of DFIG and equivalent model of wind farm in PSAT.Then,the IEEE 39-bus system and four-generator two-area power systemcontaining DFIG-based wind turbines are constructed in PSAT. Based on the theory of singular value decomposition, an index with quadratic function characteristic is chosen as a static voltage analysis means in order to study the voltage stability of the power system.Three indicators of LC?quadratic ??r and C give a basis for investigating the static voltage stability and the perfect site selection of reactive power compensators of doubly-fed wind turbines including different grid-connected positions.A voltage stability control method is proposed based on the static reactive power compensation device SVC, comparing and analyzing the support and improvementto the system voltage with different grid-connected positions of SVC.The simulation results prove that different positions of grid-connected DFIG-based wind turbines can cause different significant effect on voltage stability.It will improve static voltage stability inconspicuouslywhen DFIG-based wind turbines is connected to generator areas, and can weaken static voltage stability when they are connected to load areas. The effects can change due to different positions of grid-connected DFIG.Finally,against system power oscillation problem caused by wind farm, this paper proposes a control strategy based on two-band power systems stabilizer PSS4B for suppressing the regional oscillation and the interval oscillation modes in the multi machine system and power oscillation caused by wind power parallelling to the grid and achieves good inhibition effect. A mathematical mode of PSS4B is built up in MATLAB. Examples are set to verify the proposed method. Simulation results its effectiveness of the proposed strategy.