Fuzzy dynamic programming approach to reactive power/voltage control in a distribution substation

A fuzzy dynamic programming (FDP) approach is proposed for solving the reactive power/voltage control problem in a distribution substation. The main purpose is to improve the voltage profile on the secondary bus and restrain the reactive power flow into a main transformer at the same time. To reach our objectives, the load tap changer (LTC) usually installed in a main transformer is employed to adjust the secondary voltage and the capacitor connected to the secondary bus is employed to compensate the reactive power flow for the load demands. We first forecast the real and reactive power demands of a main transformer and its primary voltages for the next day. With these forecasting data at hand, a fast LTC tap position estimation formula that takes the load models into account is derived to effectively reduce the computational burden for the proposed approach. Practical constraints on bus voltage limits, maximum allowable number switching operations in a day for the LTC and capacitor and the tolerable worst power factor for a main transformer are also considered. To demonstrate the usefulness of the proposed approach, reactive power/voltage control at a distribution substation within the service area of Taipei City District Office of Taiwan Power Company is investigated. It is found that a proper dispatching schedule for the LTC and capacitor can be reached by the proposed approach.