1. School of Electrical and Electronic Engineering, Shandong University of Technology, Zibo, Shandong, China
2. Liaocheng Power Supply Company, State Grid Shandong Electric Power Company, Liaocheng, Shandong, China
3. Technical College Branch of State Grid Corporation of China, Jinan, Shandong, China
4. China Petrochemical Corporation, Shengli Petroleum Administration Co. Ltd. Electric Branch, Dongyin, Shandong, China