The electricity spot market is a critical element in developing an electricity market system and its open

competitive

and orderly operation. An appropriate pricing mechanism is basic for reflecting the commodity nature of electricity

thereby guiding the resource allocation

and eventually enhancing the operational efficiency. However

the essence of electricity spot market clearing centers on solving unit commitment

whose inherent non-convexity leads to the locational marginal pricing based on security-constrained economic dispatch

generating significant uplift costs. These uplift costs may define different costs for the same services

introducing market discrimination and ultimately affecting market fairness. In response to these challenges

this paper delves into the theoretical foundations and application limitations of this locational marginal pricing and then proposes a method to alleviate the obvious impact of non-convex costs on market fairness. Specifically

the paper introduces a linear relaxation pricing method based on the convex hull of unit commitment

which theoretically shown to be effective in reducing total uplift costs and achieving market fairness

thereby expanding its applications. Finally

this proposed linear relaxation pricing method based on the convex hull of unit commitment is applied to the modified IEEE-30 test system and the Polish-2383 test system

whose numerical simulations are utilized to validate its effectiveness.