Impact Assessment And Countermeasures Of Wind Power Integration On Grid Voltage

Recently with the continuous change of technological progress and developed concepts,methods of wind power generation and other new energy power generation have been paid widely attention by many countries.Its advantages of eco-friendly philosophy and renewability can help to solve the problem of energy shortage and environmental protection worldwide.Based on the randomness and uncontrollability of wind resources,large-scale wind power grid integration is a double-edged sword for regional power grid.In order to reduce the negative impact of wind power grid integration,contribute better to grid and increase the proportion of wind power to the grid,China generally chooses the higher voltage level grid to integrate.With the improvement of wind power technology and the trend of energy sustainable development,it can be predicted that the wind power penetration will be increasing in the future.Therefore.it is practical to analyze the characteristics of wind grid and study the impact of power distribution.In this thesis,this thesis mainly studies the following aspects:(1)The development status of wind turbines is researched and the wind grid model and annular grid model are established.In this thesis,the wind grid steady-state model based on doubly-fed wind turbines,which is most commonly used in China,is discussed in depth.By studying the steady-state model under constant power factor operation mode and comparing three commonly used steady-state models,a simplified steady-state model for calculation is proposed.On the premise of guaranteeing the accuracy of power flow calculation results.the calculation process is optimized and the number of power flow calculation is reduced,which improves the operation efficiency.According to the simplified steady-state model,a wind grid model is built by DigSILENT to calculate later power flow.(2)The influence of wind power grid integration.on the voltage of ring power grid is analyzed theoretically.The influence of wind power grid integration on steady-state voltage distribution and static voltage stability in ring power grid is deduced.According to the actual situation of Weifang power grid,a ring network model is established,and the results of theoretical analysis are verified in both wind grid steady-state model and ring network model.From the active and reactive power output of wind grid,the influence of grid integration on the ring power grid is studied detailly.The influence of the same wind grid output on the grid voltage is simulated respectively under the conditions of large load in summer and small load in winter.The simulation results show that the variation of active power and power factor of wind grid will affect the steady-state voltage distribution of power grid.Meanwhile,the range of influence will affect all nodes in the loop network.And the degree of influence will be affected by the output and load of wind grid.(3)A method of wind power grid voltage evaluation based on correlation analysis is proposed.Wind power grid integration has a greater impact on grid voltage,but the voltage fluctuation is also related to generator output,load fluctuation,load failure and other factors.Aiming at the unreasonable aspects of existing power quality assessment methods,the thesis proposed some solutions.Through correlation coefficient method and Granger causality test,the correlation between output variation of wind grid and node voltage to be evaluated is judged.Vector autoregressive model needle is established for correlative variables to evaluate the impact of specific wind grid on voltage.The process of evaluating the impact on grid voltage based on correlation analysis is proposed,which provides a basis for improving the current situation of wind power grid integration according to the evaluation results.(4)Combined with the current situation of wind power grid integration and the impact assessment of grid voltage,the corresponding countermeasures are put forward to improve the quality of grid.By comparing the current development status of wind turbine,the double-fed wind turbine and direct-drive wind turbine are analyzed in many ways.Then the appropriate type of wind turbine is selected according to Weifang wind resources.The existing reactive power compensation schemes for wind grid are discussed,and a more reasonable reactive power compensation scheme is proposed.According to the results of correlation evaluation,choosing the appropriate access location of wind grid can not only improve the integration capacity of wind power,but also reduce the impact on grid voltage.Combining with the geographical characteristics of Weifang,the maximum wind power absorptive capacity is calculated,and appropriate methods to improve the wind power absorptive capacity of regional power grid are put forward.