Small scale integration of variable speed wind turbines into the local grid and its voltage stability aspects

The effect of small scale variable speed (VS) wind energy integration into the local grid is investigated in this paper. In particular, the effect of reactive power control from wind turbines on the local voltage stability considering different types of load is analyzed here. Both steady-state and dynamic analysis have been done. It is found that integration of wind power in several feeders of a sub station could influence the operation of the tap changing transformer at the substation. With the high level of integration of wind turbines at the local grid, mixed with different critical loads, high load-low wind condition is the most critical situation from a load power quality point of view when lost voltage-time area at the load bus will be higher for a given disturbance at the grid. To overcome a relatively low voltage disturbance (grid voltage dip higher than 85%) by utilizing the fast power electronic converter of the nearby wind turbine, keeping the active power production from the wind turbine at the pre-disturbance value, it is the high wind-low load situation which is the difficult case to handle from the wind turbine side. Mitigation of a larger voltage disturbance in this way requires a larger grid side converter. Instead, injecting reactive current into the grid keeping the active current injection from the wind turbine at the pre-fault level, gives satisfactory contingency performance of the wind turbine from the grid point of view