This paper proposes a methodology for distribution system operation using battery energy storage system (BESS), interfaced inverter with DGs and existing voltage control devices. The proposed method decides the optimal operation schedule of each control device by optimal calculation. Optimal calculation uses a forecast information for a next day photovoltaic generator output and load demand. As a result, the proposed method achieves a voltage control for each of the node within the acceptable range, smoothing an interconnection point power flow and reducing of total distribution loss. The effectiveness of the proposed method is verified by using MATLAB.