A modified control algorithm of Variable Speed Wind
Generator (VSWG) for supporting power system frequency stabilization is
presented in this paper. Comparison of the performance of this algorithm with
active power control algorithms of VSWG for supporting power system frequency
stabilization, as published in the scientific literature, is also presented. A
systematic method of analysis of the modified control algorithm is described in
detail. It has been shown that by using the modified control algorithm, VSWG “truly”
emulates the inertial response of a conventional steam generating unit with synchronous
generators during the initial/inertial phase of primary frequency control, following
loss of active power generation when wind speed is between cut in (i.e. 4 m/s) and
rated speed (i.e. 12 m/s). By the inclusion of a signal proportional to the
frequency deviation as a power reference to the torque controller feedback loop
of the modified control algorithm it is ensured that the contribution of VSWG
to frequency stabilization is independent of the initial wind speed. This
independence is kept as long as the wind speed
is above the cut in wind speed and slightly below rated
wind speed (i.e. 12 m/s). One of the important features of the modified control
algorithm, namely a near-proportional relationship between the initial wind
turbine speed and the maximum wind turbine speed variation during the inertial
response has been identified. The results of the analysis
provide a solid basis for further research in the area
of VSWG contribution to frequency stabilization.