Representing Hydropower in Hydrothermal Power System

A method is developed for evaluating a hydro‐system schedule for a large power system that has both hydro and thermal resources. The method computes thermal costs that accrue while meeting hourly generation requirements by hydro plants, a thermal system, and a pumped‐storage plant. The uncertainties associated with thermal‐unit operations are dealt with by considering the thermal system as a sum of independent random variables and then computing their expected generation levels. One pumped‐storage plant is modeled in detail, with complete chronological accounting of reservoir levels and corresponding pump/generation capabilities. The conventional hydro‐system minimizes the variation in the hydro‐reduced loads. Constraints on the permissible hour‐to‐hour variation in a thermal unit's generation are also satisfied. The method allocates all power resources so as to approximate their most economical operation while meeting a weekly sequence of hourly power demands. It is designed to rapidly evaluate hydro schedules in models that use a power objective function. An example of the method is given for a week's projected hourly demands.