| 摘要 |
A controller operates with a varying target power factor and/or compensation range. In order to determine when to adjust the reactive power compensation by switching in/out stages of a multistage capacitor bank, the controller is provided with the step size provided by each switchable stage. The controller can thus switch in or out successive stages as necessary to compensate for the reactive power of the load and maintain the power factor close to target. To minimise repeated switching, the controller may be provided with a selectable sensitivity. The product of step size and sensitivity together with variable target power factor effectively creates a variable compensation range of reactive power levels within which no correction will be added or removed. When the reactive power level is outside the compensation range for a variable time duration the controller is operable to switch in/out shunt capacitors as necessary to return the reactive power level to within the compensation range. Preferably, a different discrete target power factor or different discrete sensitivities are selected when the active power level lies within different ranges, for example three groups of values: group 1 associated with lower levels of active power; group 2 associated with medium levels of active power; and group 3 associated with higher levels of active power. |
