1. Dept. of Electrical and Computer Engineering, Iowa State Univ., Ames, IA 50011; and Universidad de Antioquia, Medellin, Colombia.
2. XM, Compañía de Expertos en Mercados SA (Colombian System Operator), Medellin, Colombia.
3. Midwest Independent Transmission System Operator, St. Paul, MN 55108.
4. Dept. of Industrial and Manufacturing Systems Engineering, Iowa State Univ., Ames, IA 50011.
5. Dept. of Industrial and Manufacturing Systems Engineering, Iowa State Univ., Ames, IA 50011 (corresponding author).