Measured Effects of Wind Turbine Reactive Power Control on an Isolated Utility

One phase of an overall effort in evaluating performance of a 150 kW MOD-OA wind turbine connected to the Block Island Power Company (BIPCO) system consisted in analyzing three methods of excitation (reactive power) control. These are identified as 1) constant var (reactive), 2) constant voltage, and 3) constant power factor (PF) control. The power system environment in which the wind turbine generator (WTG) exists ultimately determines which method of control is the most suitable. In the case of the BIPCO installation, the major emphasis was to insure sufficient WTG electrical torque during wind gusts in low power output periods. Subsequent use of constant PF control demonstrated an adequacy of performance equivalent to that of constant var control while constant voltage control indicated a diminished capacity to maintain synchronism with the utility, when compared to constant var or PF control. A mathematical model which incorporates the detailed excitation system transfer functions is used to compare the results indicated by the measurements produced during a three-month data acquisition effort.