Abstract: To achieve the smooth connection between the medium and long-term electricity market and the day-ahead market, a joint clearing model of energy and ancillary services in the day-ahead market considering the regulation performance of cascade hydropower stations is constructed. The model considers the relationship between the energy clearing volume and the ancillary service clearing volume among cascade hydropower stations, and aims to minimize the total procurement cost of the day-ahead market to obtain the clearing results of energy and ancillary services in the day-ahead market. The duality theorem is used to analyze the relationship between the ancillary service offer of cascade hydropower stations and the energy clearing price. The results show that the lower the ancillary service offer, the lower the energy clearing price. The settlement results using the difference contract method show that the established model can reduce the risk of recovering excessive profits for power generation entities and increase electricity revenue.

Key words: power market transaction, cascade hydropower station, energy transaction, ancillary service transaction, joint clearing