  The start up costs in many kinds of generators lead to complex cost
structures, which in turn yield severe market loopholes in the locational
marginal price (LMP) scheme. Convex hull pricing (a.k.a. extended LMP) is
proposed to improve the market efficiency by providing the minimal uplift
payment to the generators. In this letter, we consider a stylized model where
all generators share the same generation capacity. We analyze the generators'
possible strategic behaviors in such a setting, and then propose an index for
market power quantification in the convex hull pricing schemes.
