IMPROVING VOLTAGE STABILITY BY UTILIZING REACTIVE POWER INJECTION CAPABILITY OF VARIABLE SPEED WIND TURBINES

N.R. Ullah∗ and T. Thiringer∗

Keywords

Renewable generation, variable speed wind turbine, power system stability, reactive power, underload tap changer

Abstract

The impact that wind turbines have on the voltage stability is investigated in this paper. In particular, the effect of utilizing the reactive power injection capability of modern wind energy converters is investigated. It is found that large wind farms, integrated into the transmission level with their control properly modified, can increase the voltage stability of the power grid substantially, as well as moderately increase the steady-state power transfer limit. For a high wind speed situation in which the wind turbine converter is fully utilized, it is found that it is worth reducing the active power production from the wind turbine to make room for reactive power injection from a voltage stability point of view. An interesting observation is that a modern variable speed wind turbine constantly operating at maximum power factor does not provide much voltage stability improvement compared with a traditional fixed-speed system under its usual operating condition, i.e., at lower wind speeds. The finding is that the worst case to handle, from a voltage stability point of view, is the case where there is a high load demand, irrespective of the wind speed situation.

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