On-line voltage control in distribution systems with multiple voltage regulating devices

Voltage regulation in distribution systems is typically performed with the aid of multiple voltage regulating devices, such as on-load tap changer and step voltage regulators. These devices are conventionally tuned and locally coordinated using Volt/VAR optimization strategies in accordance with the time-graded operation. However, in case of distribution systems with distributed generation (DG), there could be a possibility of simultaneous responses of DG and multiple voltage regulators for correcting the target bus voltage, thereby resulting in operational conflicts. This paper proposes an online voltage control strategy for a realistic distribution system containing a synchronous machine-based renewable DG unit and other voltage regulating devices. The proposed strategy minimizes the operational conflicts by prioritizing the operations of different regulating devices while maximizing the voltage regulation support by the DG. It is tested on an interconnected medium voltage distribution system, present in New South Wales, Australia, through time-domain simulation studies. The results have demonstrated that voltage control for a distribution feeder can effectively be achieved on a real-time basis through the application of the proposed control strategy.