Abstract: In order to leverage the role of energy storage systems in deep peak regulation of thermal power units and improve the economic benefits of thermal power units in the electricity market environment, a cost per kilowatt-hour model for peak regulation operation of thermal power units and an economic benefit model for energy storage systems participating in deep peak regulation of thermal power units have been established.Based on this model, the economic benefits of three energy storage systems (ESSs) (i.e. LiFePO₄ battery ESS, vanadium redox flow battery ESS and compressed air ESS) were calculated and analyzed.Results illustrate that, with the installed power of one of the three energy storage systems of 420 MW, the peak regulation depth of 50%, and the low price electricity charging price of 0.288 yuan/(kW·h), the energy storage system has the best economic benefits when the ratio of peak regulation frequency to charging frequency at low electricity price is minimized.The three energy storage systems, in order of economic benefits, are LiFePO₄ battery ESS, vanadium flow battery ESS, and compressed air ESS. The corresponding optimal levelized cost of energy (LCOE) for the three systems are respectively 0.860, 0.921, and 0.960 yuan/(kW·h), with internal rates of return of 27.01%, 6.24%, and 5.40%, respectively.