A New Method for Online Sensitivity-Based Distributed Voltage Control and Short Circuit Analysis of Unbalanced Distribution Feeders

Reactive power support through shunt capacitors and distributed generation is used in conjunction with step voltage regulators (SVRs) for voltage control of distribution feeders. Distribution management system is responsible for coordination among distributed reactive power sources, such as capacitors, photovoltaic and wind power generators, and SVRs. In this paper, a novel method for calculating voltage sensitivity to active, reactive power injection, and SVR taps in unbalanced distribution feeders is developed. The method is based on ABCD parameters of network components which are used in forward/backward sweep of power-flow solution. The method can deal with network unbalance, network shunt admittances, single-phase sections, and ungrounded sections. The initial sensitivities are calculated in one power-flow forward sweep through a recursive way, and the online updating of sensitivities is very easy and straightforward so the method is suitable for online voltage control. A novel sensitivity-based online optimization method is developed for online coordinated voltage control with no prior information about the load. The same ABCD parameters are used for developing a novel method for calculating short circuit currents in unbalanced distribution feeders. The method can also handle unbalance, shunt elements, and single phase sections, and is applicable to all fault types. The developed method for voltage control and short circuit calculation are tested on the IEEE comprehensive test feeder and the results prove the effectiveness of the proposed algorithms.