As standard operating procedure while any mode of start up power plant that during silica purging, we maintain the load 350MWgross with 4 mills in service. The Unit Master control for load 350MWgross can be shown picture above.
From load set 350MWgross, Main Steam pressure set point is 91.97 Bar, Turbine master position 57.64% and Coal flow demand 133.21 T/h as interpolate calculation below.
The Unit Master logic if no feed back value can be shown as picture below.
The Unit Master logic actual has feedback value caused by load actual 357MWgross (7MW overshoot). This time is stat boiler over firing and shown that Turbine master position can response from overshoot but the boiler master is delay 30min. Coal flow consumption just need around 133.21 T/h but get overshoot until 190.2 T/h, and the turbine master position response to 100% make generator load overshoot until 450MW (350MW set).
This caused by boiler control only use proportional - integral control and every 120s the integral control send the feedback. I needs longer time to get steady state and derivative control should be in consideration when power plant on very hot start at mode.
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