Voltage stability preventive control using VMPI sensitivities

In power systems the proper voltage ranges are predetermined in the individual voltage classes. In order to maintain the proper voltage ranges, we propose the voltage stability index VMPI (Voltage Margin Proximity Index), which defines the voltage stability from the point of view of the voltage magnitude limits. Many previous papers dealing with voltage stability preventive control have used control devices which take continuous values, such as static var compensators, but real power systems mainly utilize voltage control devices which take discrete values. Hence, in this paper, we propose voltage stability preventive control using the VMPI sensitivities in order to control devices which take discrete values. We generally require speed for preventive control in order to use it on line, but the VMPI takes time due to the performance of optimal power flow calculations. Consequently, we propose a practical voltage stability preventive control method using a calculation with initial estimates of the control devices and estimation of the VMPI sensitivities, which requires less calculation time. Simulations using the IEEJ West 30-machine 115-bus system have verified the effectiveness of the proposed method.