Risk-based security assessment for operating electric power systems

The power system is a widespread and complex network whose complete behavior, at present, still remains partially characterized. Power systems have operated in most cases reliably, but conservatively with the help of many deterministic techniques that rely heavily on the modeling of system components and the associated dynamics. Now, with increasing competition and growing demand, the power system, however, has been shifting from a deterministically regulated system to a competitive and uncertain market environment. Power utilities are required to have a comprehensive knowledge of the risks as well as benefits in their transmission operations. Our interest is motivated by this need of the industry to provide a method to quantify the risk of operating a power system with consideration to the probabilistic nature of system behaviors. The objective of this dissertation is to develop a foundation of risk-based bulk power system security assessment that leads to the definition, calculation, and application of the risk in operating electric power systems. The work includes three parts of risk assessments: transmission line thermal overload, voltage insecurity, and composite risk assessments. Both the probability of insecurity problems and their cost consequences are measured such that an expected monetary impact is given as the measurement of risk. This quantitative measurement of thermal, voltage, and composite risk is helpful for the operator to trade off the benefits and costs in the competitive utility environment. For making this economic tradeoff, several decision criteria, including both deterministic and probabilistic strategies, from conservative to greedy preference, are introduced to aid the operator to make operating decisions. This research establishes a bridge between power system security and economics by the index of risk that is compatible with the economic results of market-based electricity trading. Both the method to quantify the risk and the ways to apply it in decision-making make contributions to the power industry