Utilization of electric vehicles for frequency regulation in Danish electrical grid

Abstract

Utilization of electric vehicles (EVs) to support the electrical grid (ancillary services), especially for frequency regulation, in Danish electrical grid is evaluated. Danish grid has two different networks: DK1 (Western Denmark) and DK2 (Eastern Denmark). Although both electrical grids are coordinated by the same transmission service operator (TSO, Energinet.dk), they have different characteristics, including the capacity, supply composition, and grid connections. The capacity of DK2 network is significantly smaller than DK1 and has relatively high share of renewable energy, leading to several problems, including frequency fluctuation. Regarding the primary frequency regulation, DK2 adopts a symmetrical regulation for both up and down regulations. On the other hand, DK1 adopts an independent price for each up and down regulations. From revenue analysis of frequency regulation service conducted by passenger EVs, revenue of about 7,000-11,000 DKK per year can be earned for passenger car in both DK1 and DK2. However, primary frequency regulation conducted by EVs in DK2 leads to higher revenue compared to one conducted in DK1. The symmetric primary frequency regulation in DK2 leads to higher revenue in total, including up (discharging) and down (charging) regulations. Unfortunately, because the frequency and its fluctuation of both up and down services are higher in DK2, a faster battery degradation of EVs in DK2 is predicted.