Load rejection test is requisite for large steam turbine power plants running on grid. During the load rejection

due to the large variation of unit parameters

it becomes difficult to control each parameter under manual mode.Thus

according to the characteristics of load rejection

design and optimization for relative control loops of several main systems was conducted

such as the turbine HP/LP bypass system and boiler master control system.Moreover

a new control method for feed-water control was put forward.The 50% and 75%load rejection tests indicate that

with the control system under the automatic control mode

the turbine speed is under control

the combustion in boiler is stable

each main parameter changes smoothly

and the unit can connect to the grid again quickly.Therefore

the control quality is enhanced

which ensures the operation safety of the unit and grid.