Strategic Bidding For Cascaded Hydropower Plants

A bout 16% of the electricity in the world is generated by hydropower producers.In Norway,Brazil,New Zealand and some other countries and regions,hydropower producers not only participate directly in market competition but also own an annual share of more than 60%in electricity generation.Despite having the ability to exert market power and influence market clearing prices,hydropower producers are generally regarded as the price-takers in the electricity market,and there are few researches on the strategic bidding of hydropower.Therefore,taken short-term scheduling of cascaded hydropower into consideration,this paper proposed a bi-level model to determine price and quantity strategic bids for a casecade hydropower producer participating in a day-ahead electricity market.The upper level is to slove the strategic bidding with the objective of maximazing the profit of the hydropower producer and the constraints of short-term scheduling of cascaded hydropower.The lower level problems represent the day-ahead market clearing problems,through which market clearing prices and winning power of each producers and demands in each period and scenario are obtained by maximizing social welfare under system oparating conditons.Uncertaitny on offering strategies of rivals are modeled by using a set of stocastic scenarios.Since decision vriables of upper level becomes parameters in the lower level problems,the lower level problems are linear.Hence,the bi-level model are rewritten as a one-level mathmetical programming with equilibrium constraitns(MPEC)by equivalently substituting the lower level problems as Karush-Kuhn-Tucker(KKT)conditions.Using linearization technique,the MPEC model is reformulated as an mixed-integer linear program(MILP),which can be addressed directly through commercial solver CPLEX via GAMS.The proposed model is applied in a 3-node test system with three hydroelectric cascade plants in different cases to show the effectiveness and efficiency of the model.