PURPOSE: To prevent a parallel operation of an SC ON or ShR ON by transmitting the SC ON or ShR ON state signal of control ranges of controllers of power systems to be controlled by a plurality of VQ controllers to a controller of the other system, and controlling to switch a control pattern of the received VQ controller to an ShR or SC ON limit.

CONSTITUTION: An SC (power capacitor) and an ScR (shunt reactor) ON state signal of an own control range of each VQ controller are transmitted to the other system. When a voltage (V), a reactive power (Q) of the VQ controller are 'H', an SC ON (or ScR OFF) control is conducted through an AND conditions in which when the reactive power (Q) is 'H', it is not the own SC ON limit state and the other system ShR does not keep ON state. On the other hand, since the other system SC keeps ON when the V, Q falls in a B range of a control pattern, the ShC ON control is locked, and it becomes an LR (on-load time tap changing) drop control. Similarly, when the ShR signal is received by the other system and is 'H', the SC ON control is locked, and it turns into the LR rise control.