A Novel Electric Vehicle Aggregator Bidding Method in Electricity Markets Considering the Coupling of Cross-Day Charging Flexibility

This article presents a novel method for electric vehicle aggregators (EVAs) to engage in day-ahead and real-time electricity markets, overcoming the issue of cross-day energy gaps of EVAs. Traditional day-ahead bidding processes are usually treated as independent, one-time actions, and fail to consider the continuity of the cross-day energy status of the electric vehicle (EV) fleet. To tackle this problem, the endpoint energy and power boundary (EEPB) model is introduced, which is achieved by decomposing each EV charging event into multiple events based on the split points. Then, a two-layer method to determine the optimal split points, i.e., split times and split energy levels, which minimizes the flexibility loss of the EVA, is proposed. In addition, a novel cross-day bidding method for EVAs, which aligns with the day-by-day bidding process, is proposed. This method utilizes EEPB based on historical EV charging records, restores flexibility on an operating day, and implements a risk-averse cross-day bidding strategy. These proposed methods are tested on about 700000 real-world residential EV charging records in North China between 2021 and 2022, demonstrating their effectiveness in addressing cross-day energy gaps, reducing charging flexibility losses, and achieving a balance between cost and risk for EVAs.