1. School of Engineering, King Mongkut's Institute of Technology Ladkrabang,Electrical Engineering Dept.,Bangkok,Thailand
2. School of Engineering, King Mongkut's Institute of Technology Ladkrabang,Instrumentation and Control Engineering Dept.,Bangkok,Thailand
3. Power System Operation and Control Section 2,Power System Control Dept. Metropolitan Electricity Authority,Bangkok,Thailand
4. School of Engineering, Rajamangala University of Technology Rattanakosin,Electrical Engineering Dept.,Bangkok,Thailand