TECHNICAL FIELD
5 [0001] The present disclosure relates to a control device and a control method.
This application claims the priority of Japanese Patent Application No. 2020-219036 filed
on December 28, 2020, the content of which is incorporated herein by reference.
BACKGROUND
10 [0002] A thermal power plant is known which uses steam generated in a boiler (steam
generator) to drive a steam turbine. A thermal power plant of this type may have a turbine
bypass valve on a bypass line configured to bypass the steam turbine with respect to a line for
supplying steam from the boiler to the steam turbine. The turbine bypass valve is typically
used to contribute to reducing a startup time by controlling an opening degree before startup of
15 the steam turbine or to suppress a rise in steam pressure by performing an opening operation
when the steam pressure in the steam turbine rises excessively.
[0003] Meanwhile, an electric utility that operating, as such a thermal power plant, a
thermal power plant for generating power with an output of a steam turbine has an obligation
to try to maintain a voltage and a frequency of the generated power at values predetermined for
20 a power grid, which is a power supply destination, according to the Electricity Business Act.
The electric utility has responded by controlling the boiler output on the basis of a load demand
value provided from a central load dispatching center according to a supply and demand state
in the power grid or an AFC (Automatic Frequency Control) signal responding to a relatively
fast frequency fluctuation.

we claim:

1. A control device for a thermal power plant that includes a boiler, a steam turbine driven
by steam from the boiler, and a turbine bypass valve for adjusting an amount of steam bypassing
5 the steam turbine, comprising:
a turbine bypass valve opening command value generation part for generating a turbine
bypass valve opening command value for the turbine bypass valve on the basis of an AFC
(Automatic Frequency Control) signal, in an AFC associated mode of the thermal power plant;
a turbine bypass valve control part for controlling the turbine bypass valve on the basis of
10 the turbine bypass valve opening command value;
a boiler input demand value generation part for generating a boiler input demand value
by adding a positive sign bias value to a base input value based on a load demand value for the
thermal power plant, in the AFC associated mode; and
a boiler control part for controlling the boiler on the basis of the boiler input demand value.
15
2. The control device according to claim 1,
wherein the bias value is constant regardless of the load demand value, in a range where
the load demand value is not greater than a predetermined value.
20 3. The control device according to claim 2,
wherein the bias value is set corresponding to a maximum decrease value relative to a
reference value of the AFC signal.