Studies On The Impacts Of Voltage Stability Of Local Power Grid Integrated With Large Scale Wind Farms

Large scale wind farms integrated to the grid brings more and more impacts on the safety, stability and scheduling operation of electric power system in our country. It is emergent to carry out the relevant theoretical research and analysis work. This topic aims at the voltage safety and stability of power grid integrated with large scale wind farms.The major study and analysis objects include static voltage stability, maximum access capacity and transient voltage stability of local power grid which integrated wind farms.Basing on the wind farm’s steady-state model, complete node P-V curve of two different types local power grid is calculated through continuation power flow respectively.Through P-V curve, active power transmission limit, the collapse point voltage level and static voltage stability of different operation mode is analysised. In the operation of wind farm, appropriate capacitance compensation, larger R/X ratio tie line, smaller wind farm equivalent load and higher system voltage can improve the static voltage stability of local power grid.All node P-V curves is calculated on the different power factor of wind farm and operation mode of power grid. Calculating wind farm maximum access capacity also needs to use voltage limit violation when adding wind power. Wind farms running state should consider all wind speed between cut-in and reted speed. The maximum access capacity of wind farms has a closed relation with wind turbine power factor. So there has a power factor makes the largest wind farm maximum access capacity.Basing on the wind farm’s model of each part, transient voltage stability of local power grid is studied, the influence to the voltage stability is researched on the maximum and minimum reactive power demand operation mode after power system’s fait. If wind turbine is tripping, the wind turbine terminal and collection station node transient voltage stability are influenced greatly. The influence is small to the main network node. If wind turbine is not tripping through low voltage ride through capability of wind turbine, the influence is small to all the node. Therefore, in order to improve the transient voltage stability, wind turbine must have the low voltage ride through capability.