Accommodating High Levels of Variable Generation - NERC

Characteristics of Power Systems & Variable Generation
to decrease power. This technique of yaw control is in practice only for small wind turbines
(1 kW or less), as it subjects the rotor to cyclically varying stress which may ultimately
damage the entire structure.
• Voltage Control: As variable resources, such as wind power facilities, constitute a larger
proportion of the total generation on a system, these resources may provide voltage
regulation and reactive power control capabilities comparable to that of conventional
generation. Further, wind plants may provide dynamic and static reactive power support as
well as voltage control in order to contribute to power system reliability. Figure 2.7 shows
an example of the performance of a voltage control scheme at a 160 MW wind plant in the
western U.S. illustrating the plant’s ability to support and control voltage. 31
Wind Plant Voltage
Voltage at POI
Wind Plant Power Output
Figure 2.7 Wind Plant voltage control with significant variation in wind power
31 This plant consists of 108 wind turbine generators (1.5 MW each), connected to a relatively weak and
remote 230kV utility interconnection substation by approximately 75 km of 230kV transmission line. The short
circuit ratio (fault duty/plant rating) at the point of interconnection is about 3.5. The voltage
regulator continuously adjusts the reactive power output to maintain constant voltage at the interconnection bus.
Accommodating High Levels of Variable Generation 22