Reliability Assessment at Day-Ahead Operating Stage in Power Systems with Wind Generation

This paper proposes to evaluate reliability performances at operating stage for power systems with variable wind generation. This is a first step towards recognizing the stronger coupling of power system decision making across different time-scales. In the day-ahead energy-reserve co-optimization unit commitment model, the validity of using operating reserve as an approximation of long-term reliability requirement is tested with realistic wind generation profile. Reliability indices such as Loss of Load Probability (LOLP) and Loss of Expected Energy (LOEE) are computed at each hour of the day at the conclusion of the day-ahead unit commitment decision. Numerical experiments conducted in the IEEE Reliability Test System suggest that while operating reserve requirement does not change within a day, the actual reliability performance of the system varies significantly depending on (i) system loading conditions, (ii) wind power variation, and (iii) operating rules. Also, the operating reserve requirement is shown to either over-approximate or under-approximate the reliability requirement of power system. It indicates that operating reserve could be a very coarse deterministic approximation of system reliability requirement especially with high wind penetration. A much more integrated approach for modeling, analysis, and decision making is envisaged for provision of reliable and cost-effective electricity services.