He is one of the leading experts in the area of power system stability analysis and control. The Complementary–Cluster Energy–Barrier Criterion (CCEBC) developed by him is a rigorous theory and quantitative method for general motion stability of non-conservative and non-autonomous systems. The Extended Equal–Area Criterion (EEAC) for power system stability is just such an example. The outstanding performances of EEAC have been demonstrated by on–line operation records in many EMS environments all over the world. Based on EEAC,the so-called Wide Area Monitoring Analysis Protection-control (WARMAP) system has been served in East China Power Grid since December 2006, which is the first blackout defense system in the world.