Energy delivery capacity and generation scheduling in the deregulated electric power market

The generation schedules obtained in traditional hydrothermal scheduling or unit commitment programs are in hourly generation levels. In the new deregulated power market, the power transactions are processed in terms of hourly energy delivery. Failing to fulfil scheduled energy delivery may result in a penalty to the power producers. This paper shows that although ramp-rate constraints are satisfied in hydrothermal scheduling, taking a generation level schedule as an energy delivery schedule may not be realizable. Based on the maximum principle in optimal control theory, the energy delivery capacity across the scheduling horizon is established as a set of recursive equations with given ramp-rate constraints. A sufficient and necessary condition is obtained to check if an energy delivery schedule is realizable. Based on this condition, two cases, where ramp-rate constraints are both satisfied, are analyzed and an unrealizable energy delivery schedule is observed.