Special issue on on-line voltage stability assessments and enhancement

Abstract

It is our honor and privilege to serve as guest editors of the special issue on power system On-line Voltage Stability Assessments and Enhancement for International Transactions on Electrical Energy Systems.A major activity in power system planning and operations is the examination of the impact of a set of credible disturbances it has on power system dynamic behaviors such as stability. Power system stability analysis is concerned with a power system's ability to reach an acceptable steady state (operating condition) following a disturbance. Important conclusions and decisions about power system operation and planning are made on the basis of the results of stability studies.Power system instabilities are unacceptable to society. Indeed, recent major blackouts in North America and Europe have vividly demonstrated that power interruptions, grid congestions, or blackouts significantly impact the economy and society. The ever-increasing loading of transmission networks together with a steady increase in load demands has pushed many power systems ever closer to their stability limit.Over the past 40 years, more than 30 major blackouts worldwide were related to voltage instability and collapse. Among them, at least 13 voltage-related blackouts happened in the USA. The on-line voltage stability assessment (VSA) system is designed to provide system operators with critical information for secure operations of power grids against voltage instability. There are significant engineering and financial benefits to be expected from on-line VSA. First, one may be able to operate a power system with operating margins reduced by a factor of 10 or more if the VSA is based on the actual system configuration and operating conditions instead of assumed worst case conditions, as is done in off-line studies. The second benefit is that the on-line analysis can be reduced to those cases relevant to actual operating conditions, thereby obtaining more accurate operating margins and allowing more power transfer. Because of the emerging smart grid environment where the distributed (renewable) generation and demand responses introduce much more uncertainty into the power system real-time operations, the on-line VSA system is becoming a critical tool for smart grid operations.As power systems become more complicated and the penetration of renewable energies increases, system operators require more powerful tools to analyze voltage security of the system based on actual on-line system operating conditions. VSA and enhancement (VSA&E) is a key application for maintaining and enhancing voltage security of bulk power systems. In today's control center, as power systems become more stressed and the penetration of renewable energies increases, system operators need to analyze voltage security of the systems based on actual operating conditions, contingency, and stressing of the system. Many power companies including California ISO recognized such a need. They required a real-time voltage stability analysis tool for maintaining the reliability of the...