Recently，large amount of photovoltaic generator（PV) have been installed to distribution systems. Hence，it has been more difficult to maintain voltage within adequate range and to suppress voltage f1uctuation caused by PV due to weather condition. One of the conventional methods to regulate voltage is to use SVR (Step Voltage Regulator) which changes its tap position automatically by monitoring its secondary voltage. However，it is concerned that the number of time changing tap position of SVR increases in case that large amount of PVs are connected. Furthermore，this causes the deterioration of SVR. In contrast，some devices controlling reactive power such as SVC (Static Var Compensator) is regarded as effective voltage control equipment against a sudden voltage change caused by PV. Nevertheless，large capacity of SVC is required to regulate voltage sufficiently and this causes high cost.
In this paper, the new algorithm of SVR controlled by using solar radiation sensor is proposed to prevent voltage deviation and reduce the number of operations of SVR to prevent the deterioration of SVR. This method is low-cost method because it needs only SVR which is already placed to distribution system. Effectiveness of the proposed control method is confirmed by numerical simulation.