A comprehensive on-line voltage stability assessment method based on continuation power flow

Static voltage stability assessment (VSA) of power system based on load margin computation has been a basic module in modern EMS. However, the static load voltage characteristics, automatic adjustment of ULTC and switchable shunt are not considered in most VSA tools. Furthermore, the thermal limit induced branch outage is not considered. Therefore, the maximal power limits obtained in VSA are not of practical significance, which do not meet the requirement of security alarming and preventive control. A novel on-line static VSA method based on continuation power flow technique is proposed in this paper. The effects of load voltage characteristics, automatic devices and relays of transmission lines have been considered. The proposed method has been used on a practical system in China. The numerical results show that the proposed method is more suitable for on-line voltage stability assessment.