1. Professor, College of Renewable Energy, North China Electric Power Univ., Beijing 102206, China.
2. Graduate Student, College of Renewable Energy, North China Electric Power Univ., Beijing 102206, China (corresponding author).
3. Graduate Student, College of Renewable Energy, North China Electric Power Univ., Beijing 102206, China.
4. Senior Lecturer, College of Renewable Energy, North China Electric Power Univ., Beijing 102206, China.