Development of short-term reliability criterion for frequency regulation under high penetration of wind power with vehicle-to-grid support

Existing reliability indices for power systems provide measures of long-term stability; in this work, we propose a new reliability criterion that estimates the probability of a spinning-reserve shortage occurring, thus indicating the short-term stability of the grid frequency. In the formulation, load, wind power, and vehicle-to-grid (V2G) power are represented as random variables, and conventional generators are incorporated in a deterministic manner. Using the equilibrium of demand and supply and the physical constraints of automatic generation control (AGC), two inequalities are derived, from which the probability of successful frequency regulation is obtained. The inverted probability, referred to as the failure rate for frequency regulation (FRFR), is employed as a metric in the short-term reliability criterion. Then, the developed criterion was applied in several case studies. First, the impact of wind-power deployment was estimated in terms of the required spinning reserve. The acceptable penetration level of wind power was then investigated in the case that V2G power is also present. The variation of FRFR with respect to the commitment level of thermal (non-renewable) power plants was also investigated under the renewable portfolio standard (RPS) to illustrate the recursive effect of the policy. Finally, FRFR was calculated for the IEEE reliability test system and compared with conventional reliability indices.