An approximate solution to lower tap changing or capacitors regulator times in reactive power control in distribution systems

In the operation of distribution system, if the tap of transformer and capacitors regulators were frequently changed, these devices would be easily damaged. So it is necessary to lower the tap-changing and capacitors regulators times. Due to the fact that capacitors exert smaller influence on the voltage level than transformers do, it is appropriate to first adjust the capacitors settings with tap position fixed so as to reduce substantially the probability of voltage limits violations while minimizing losses, and then to adjust transformer taps to maintain voltage within the specified range. The problem of reactive power and voltage control is well decoupled. The objective function is not related to the taps changing of transformers, but it is only related to capacitive susceptance; therefore, the capacitors variables can be adjusted alone to reduce the objective function, then the taps changing of transformers to meet the voltage constraints. In this paper, a two-phase based loss optimization algorithm, which is suitable to distribution network, is presented. In this method, losses in the system can be optimized, and the tap-changing or capacitors regulators times can be lowered. IEEE 30-bus system indicates the proposed algorithm’s validity, fast convergence, and computation efficiency.