Locational-based coupling of electricity markets: benefits from coordinating unit commitment and balancing markets

We estimate the benefits of electricity locational marginal pricing (LMP) that arise from better coordination of day-ahead commitment decisions and real-time balancing markets in adjacent power markets when there is significant uncertainty in demand and wind forecasts. To do so, we formulate a series of stochastic models for committing and then dispatching electric generators subject to transmission limits. In the unit commitment stage, the models optimise day-ahead generation schedules under either the full set of network constraints or a simplified net transfer capacity (NTC) constraint, where the latter represents the present approach for limiting forward electricity trade in Europe. A subsequent redispatch model then creates feasible real-time schedules. Benefits of LMP arise from decreases in expected start-up and variable generation costs resulting from consistent consideration of the full set of network constraints both day-ahead and in real time. Meanwhile, coordinating adjacent balancing markets provides benefits because intermarket flows can be adjusted in real-time in response to changing conditions. To quantify these benefits, we analyse a stylised four-node network, examining the effects of varying system characteristics on the magnitude of the locational-based unit commitment benefits and the benefits of intermarket balancing. We conclude that both categories of benefits are situation dependent, such that small parameter changes can lead to large changes in expected benefits. Although both can amount to a significant percentage of operating costs, we find that the benefits of coordinating balancing markets generally exceed unit commitment benefits.