Coordinated and Secured Reactive Power Control for Voltage Regulation in Modern Power Distribution Systems

Reactive power support from distributed energy resources through remote communication control is inevitable for optimum power flow and voltage regulation in the distribution power system. However, this communication control could threaten the power distribution in view of cyberattacks. This paper proposes a cooperative VAR control in distributed energy resources with an aim to continue the grid security during unexpected situations including modifications in remote VAR command, abrupt variations in power demand, and power generations. The proposed control method entirely utilizes distributed energy resources considering VAR support for the optimum power flow and gives priority to remote communication command. During the unexpected conditions, it can suspend the remote VAR command based on the local grid voltage and activate the autonomous VAR control with preferences for the voltage regulation over the optimum power flow. The remote VAR command is estimated through distributed online control framework with a dual ascent algorithm. The control and operation of on-load tap changers and switched capacitor banks are performed through VAR-Bias settings which can obviate the need for remote control. The proposed distributed cooperative VAR control in distributed energy resources and VAR-Bias settings in conventional voltage regulators are tested in a commercial 145-bus power distribution system through an extensive time-domain simulation approach. The test results verified grid reliability and security through the proposed distributed cooperative VAR control.