Because of power systems being more and more complicated, besides low frequency oscillation by minus damp, there is also chaos oscillation that can not be dispelled by PSS in power systems.

• 由于电力系统的日趋复杂和庞大,电力系统除了因负阻尼引起的低频振荡外,还存在PSS不能消除的混沌振荡的危机。