A new concept for the clearing of European Power Exchange day-ahead markets with complex orders

A new concept for the clearing of the day-ahead market of a European Power Exchange is proposed in this paper, bypassing the problems caused by the indivisibility of complex orders present in the European markets. The presence of complex orders may lead to paradoxically accepted and/or paradoxically rejected orders, necessitating the use of iterative heuristic procedures and empirical simplifying criteria for their handling. In this paper, the concept of “adjustable orders” is introduced, leading to a significant simplification in the handling of complex orders. The adjustable orders can be partially cleared, leading to orders that can be marginally accepted in the market clearing, setting the market prices accordingly for the hours involved in the orders. The complex orders that are used in this paper comprise profile block orders (offers/bids), flexible hourly orders and joint demand profile orders. The modeling of adjustable blocks is not possible as a MILP problem due to the inherent indivisibility denoted by the use of binary variables; instead, the day-ahead market clearing is formulated as a Mixed Complementarity Problem. The solution of the proposed MCP model is compared with the solution of the classical MILP model solution within an iterative procedure (employed in CWE and Nordpool) for the handling of paradoxically accepted/rejected orders.