1. School of Electronic and Electrical Engineering Hongik University Seoul 04066 Republic of Korea
2. Division of Electrical, Electronic and Control Engineering Kongju National University Cheonan 31080 Republic of Korea
3. Department of Energy Engineering Soonchunhyang University Asan 31538 Republic of Korea
4. Center of Advanced Energy Research Soonchunhyang University Asan 31538 Republic of Korea