In this paper

the leading phase limiting factors of coal-fired units in the deep peak-regulation in accordance with the limiting factors in the leading phase test of the generating unit.The measures on improving the leading phase capacity of the unit at deep peak regulation are proposed though the limiting factors of the leading phase limiting factors of the unit and in accordance with the limiting factors.It is pointed out that the main limiting factors at the deep peak regulating unit is mainly the auxiliary power voltage

then stator voltage and static stability limit

and elevation of grid voltage or switching auxiliary power plant to start transformer can effectively enhance the leading phase capacity in the deep peakregulation.It is concluded through the leading phase test of the deep peak regulation that under identical grid voltage

the leading phase capacity of the unit shows linear relationship with active power.The lower the active power is

the higher the leading capacity is

which provides theoretical and true base for the leading phase operation of the deep peak regulation.