BEIJING (AFX-ASIA) – Huaneng Power Group said it signed an agreement to buy a further 31.14% stake in Hainan Zhonghai Energy Co Ltd from several unspecified local government-controlled companies. In an announcement, Huaneng Group said after the move, it will hold a total 50.76% stake in Hainan Zhonghai, following its acquisition of a 16.67% stake…