Defining the must-run and must-take units in a deregulated market

Reliability must-run (RMR) units are generation facilities that are necessary during certain operating conditions in order to maintain the security of power systems in a competitive environment. Absence of RMR units may result in insecure operation of a system. From a financial point of view, RMR units may become a safety net for independent power producers IPPs) who enjoy steady incomes or a place for those who prefer not to participate in the competitive market. This paper presents a practical method to determine RMR units and their must-run output in the Thailand power market, according to the proposed structure of the Thailand deregulated market to be implemented in 2003 (forecasted opening date of the operation based on information of August 1999). The study determines the amount of must-run output in RMR units by finding the necessary amount of generation to avoid the violation of voltage magnitude, thermal limit, and voltage stability limit. The proposed procedure to determine RMR units defines the amount of generation capacity to be assigned as RMR and allows must-run units to sell surplus generation capacity to the system.