A dynamic simulation approach to identify additional reactive reserves against long-term voltage instability

A simple method is proposed to identify additional reactive reserves enabling to counteract long-term voltage instability after a large disturbance. In contrast to the many references based on power flow calculations, the method resorts to dynamic simulation. The post-disturbance system evolution is simulated in the presence of time-varying shunt susceptances with specified rate of change. This allows to deal with dynamic issues such as the required speed of the additional reactive power sources, or the onset of unstable electromechanical oscillations. Furthermore, a compromise is sought between the speed of action and the volume of additional compensation. The method is demonstrated on a detailed model of the Nordic test system.