Abstract: A centralized voltage control device connected, via a communication network, to local voltage control devices connected to voltage control apparatuses, including: a transmission and reception unit receiving the number of times a tap position is changed per fixed time of the voltage control apparatus from the local voltage control device; a dead-zone-width updating unit increasing a dead zone width when the number of times a tap position is changed in a voltage control apparatus of a transformer type is a threshold or larger; and a voltage-upper-and-lower-limit-value determining unit determining the voltage upper limit value and the voltage lower limit value for each local voltage control device and issuing a command regarding these values to each local voltage control device, and determining the voltage upper limit value and the voltage lower limit value of the voltage control apparatus of a transformer type on the basis of the dead zone width.

Abstract: A cooperative voltage sensor (CVS) issues a target voltage change request when a voltage moving average at an end thereof deviates from a proper voltage upper or lower limit value. A cooperative voltage controller (CVC) also can issue a target voltage change request when a voltage moving average at an end thereof deviates from the proper voltage upper or lower limit value. The target voltage change request issued by the cooperative voltage sensor (CVS) or the cooperative voltage controller (CVC) is transferred between cooperative voltage controllers (CVCs) via a communication network and notified to all the cooperative voltage controllers (CVCs), and a cooperative operation of voltage control is realized.

Abstract: A centralized voltage control apparatus calculates an optimum voltage distribution in a centralized control cycle period and determines, based on the relationship between the optimum voltage distribution and a proper voltage range, voltage upper and lower limit values for which a command is issued to each local voltage control apparatus taking into account voltage upper and lower limit margin amounts at respective points in a voltage control responsible range of the local voltage control apparatus for each local voltage control apparatus. The local voltage control apparatus adjusts, based on the voltage upper and lower limit values commanded from the centralized voltage control apparatus via a communication network, a control amount of a voltage control device every local control cycle shorter than the centralized control cycle period, to maintain the control voltage of the voltage control device between the voltage upper and lower limit values.

Abstract: Starting from an initial combination state, a destination state to which a certain state is to be moved is determined from its neighboring states or previously defined transferable combination states by using an evaluation function, and an optimal combination state for minimizing or maximizing the function value of an evaluation function comprising the sum of a function to be minimized or maximized and a penalty function representing an amount of constraint violation is intended to be found by iteratively performing a search in which the certain state is successively moved to the thus determined destination state. It is determined whether there is a constraint violation in the current state. If so, the evaluation function is switched to another evaluation function for evaluating a constraint violation alone, whereas if not, the evaluation function is switched to another evaluation function which disregards the constraint violation.