Voltage stability preventive and emergency preventive control using VIPIt sensitivities

Recently, as power system loads are located farther away from power plants and are more unevenly distributed, reactive power losses have tended to increase due to the heavier power flow with high load growth and long distance transmission. Therefore, an effective voltage control scheme has been brought to attention in a considerable number of studies. Hence, We propose on-line voltage stability control schemes, i.e. a preventive control and an emergency preventive control, in addition to conventional local controls. In order to assess the effect on voltage stability in different generators, we propose the voltage instability proximity index including three power flow equations in a specified value space (VIPIt) based on the conventional index VIPI.