Reserves in Stochastic Unit Commitment: An Irish System Case Study

As the level of variable renewable sources integrated into the power system increases, their nature forces a re-evaluation of traditional methodologies for managing uncertainty in power generation. This paper quantifies the interaction among the implicit reserve carried by a rolling planning stochastic unit commitment, deterministic reserve criteria, and the quality of information around wind forecast error, for a fully isolated 2020 Irish system. To perform this, three case studies were run. The first demonstrates that the implicit reserve carried by the stochastic model causes the implicit value of lost load set by the inclusion of explicit reserve requirements to be disproportionately high compared to the deterministic model. The second demonstrates that the relative value of the reserve rules does not have consistent impact between the models. In the final case, it is shown that the forecast error information utilized changes the security behavior of stochastic models. This is of importance, given the frequency at which normal distributions are used to model wind forecast error. Together, these results indicate a need for a holistic solution to reserve provision which considers the implicit nature of stochastic models, and forecast error assumptions when deciding reserve criteria.