A Parametric Programming Approach to Bilevel Merchant Electricity Transmission Investment Problems

Nowadays, electricity transmission investments are made in a liberalized market environment, in which the transmission system operator, the market, producers, and investors have different objectives. The transmission expansion problem can account for this by bilevel programming, with an investor making expansion decisions in an upper level while anticipating the result of a lower-level market-clearing. In this work, we formulate a stochastic transmission expansion problem of a merchant investor collecting congestion rents determined by the differences between nodal market prices. The bilevel program can be recast as a mathematical program with equilibirium constraints (MPEC), but does not allow for linearization and reformulation by mixed-integer linear programming. Instead, we apply a parametric programming approach that facilitates decomposition with respect to both time periods and scenarios. A numerical study illustrates its ability to solve the problem, even though standard solvers for non-linear MPECs fail.