JPH04262004A - Run-back method in electric system failure - Google Patents

Abstract

PURPOSE:To provide a run-back method for speedily reducing the output of a power generator, controlling the pressure and temperature of a boiler to the reference values, by controlling the output of the power generator through turbine governor in the turbine following state, and by controlling the boiler pressure through a turbine bypass regulating valve, in an electric system failure. CONSTITUTION:A switching device 51 is interposed in the output passage of a variation rate limiter 32 for obtaining the base body demand (MWD) 33 of a unit, and the demand in accordance with the electric system failure run-back target value 52 is selectively outputted in substitution for the demand outputted from the variation rate limiter 32 when run-back is generated. Further, a switching device 53 is interposed in the output passage of an adjuster (PI) 47, and a turbine bypass regulating valve 8 is opening-degree-controlled on the basis of the output of a pressure control regulator (PI) 46 when run-back is generated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a runback system in the event of an electrical fault, which is applied to, for example, a boiler automatic control system for a thermal power generation unit.

0002

[Background Art] A thermal power generation unit has a runback function that automatically and rapidly reduces the load of the failed equipment to an allowable power generation output when the equipment that makes up the unit fails. .

[0003] Usually, a forced draft fan (FDF) of a boiler,
The feed water pump (BFP) etc. is approximately 50% of the rated output of the generator.
% capacity will be installed.

Currently, if one of the forced draft fans (FDF) stops due to a failure while the unit is being operated at its rated output, the remaining forced draft fan (FDF)
It is necessary to automatically and rapidly reduce the generator output (MW) and boiler input amount (water supply, fuel) to the output that can be covered by F).

At this time, rather than simply reducing the demand at a constant rate, the steam pressure required by the turbine,
It is necessary to throttle the steam while maintaining its temperature, ie, automatically controlling it as required.

[0006] In the case of a once-through boiler, the so-called cooperative control mode is usually a method in which the turbine governor and the boiler input amount (feed water, fuel, air) are simultaneously controlled in response to the generator output demand. .

FIG. 2 is a diagram schematically showing the configuration of the power generation unit, and FIG. 3 is a diagram showing the control system in the cooperative control mode.

In FIG. 3, the output command value 31 of the power generation unit is given from the command center according to the load, and is determined by the unit's basic demand ( MWD) becomes 33.

This basic demand (MWD) 33 is divided into a demand for the generator output control system by the turbine governor 7 and a demand for the boiler input amount.

In the generator output control system, the turbine governor 7 is controlled by adjusting the deviation between the generator output (MW) 21a and the basic demand (MWD) 33 using a turbine governor regulator (PI) 36.

On the other hand, boiler input demand (BID) is
Based on the basic demand (MWD) 33, a water supply demand 38 is first obtained, and the deviation from the actual water supply flow rate (FW) 25 is controlled by a regulator (PI) 39 and a water supply adjustment mechanism 4.

Next, the main steam temperature (TM) 21b regulator (PI) 40 is connected to the water supply demand (BID) 38.
The combustion amount command (FRD) becomes the fuel flow rate demand 41, and the fuel control valve 6
is controlled.

Furthermore, the combustion rate command (FRD) 41 is controlled by a regulator (PI) of the excess air ratio (O2) 24 in the boiler exhaust gas.
)43 correction, air flow demand (ARD)
Thus, the air conditioning damper 5 is controlled via the regulator 44 (PI).

On the other hand, the main steam pressure (PT) 22 is adjusted to the basic demand (MW) by a regulator (PI) 46 so that the pressure set value (SG) 45 required by the turbine is maintained.
D) added to 33 and controlled by all boiler inputs, i.e. feed water, fuel and air.

Normally, the turbine bypass control valve 8 is fully closed, and the regulator (PI) 47 suppresses it only when the main steam pressure increases abnormally in some abnormality.

At this time, for example, if one of the ventilators 2 stops due to an accident, the device detects this abnormality and activates the runback function.

[0017] Due to the above runback occurrence, the switch (T)
35 and 38 are switched to signals on the 49 (runback target value) and 48 (adjuster 46) sides, respectively. That is, the main steam pressure (PT) 22 of the boiler is transferred to the control system by the turbine governor regulator 36, and further the boiler input demand (BI
D) 38 is switched at an allowable speed with respect to the boiler input amount limit at the time of runback occurrence, in this case 50% which is the capacity of one FDF (ventilator), and the water supply and fuel are rapidly throttled.

This control mode is usually called a turbine follow mode or boiler input mode, and is a mode in which a turbine governor controls the so-called boiler pressure.

That is, when compared with the previous form of cooperative control,
The generator output is not controlled, and the generator output depends on the behavior of the pressure control of the turbine governor.

[0020]

[Problems to be Solved by the Invention] As mentioned above, runback is generally an output restriction in the event of an abnormality in the water supply, fuel, or air system equipment that supplies boiler input. The purpose is to narrow down the output, and the behavior of the generator output is not a particular issue.

[0021]However, recently, it has become necessary to suppress the output of the unit not due to circumstances on the boiler input side but due to electrical system circumstances such as loss of cooling water in the generator or overcurrent restriction of transmission lines.

[0022] In this case, the conventional runback circuit, whose sole purpose is to reduce the input to the boiler to a target value within a predetermined time, reduces the generator output to the limit value within a predetermined time required by the electrical system. The narrowing control function cannot be achieved.

That is, rather than leaving the output of the generator to its own course, it is necessary to respond to the output suppression while controlling it in some way.

[0024]

[Means for Solving the Problems] The key point of the present invention is to realize a method of rapidly reducing the generator output while controlling the pressure and temperature of the boiler to specified values. for that,
In the above-mentioned turbine follow mode, a system is adopted in which the generator output is controlled by a turbine governor and the boiler pressure is controlled by a turbine bypass control valve.

[0025]

[Operation] When a runback occurs due to an electrical system fault, the demand according to the runback target value specific to the electrical system fault becomes effective instead of the demand according to the output command value of the power generating unit, and the The generator output (MW) is automatically controlled by the governor regulator to the required target value at the required speed. Furthermore, at this time, based on the input command (BID) according to the demand, the supply water, fuel, and air are automatically throttled to the required command value, and the pressure is automatically controlled to a predetermined value by controlling the opening of the turbine bypass control valve.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a control system in an embodiment of the present invention.

In the embodiment of the present invention, as shown in FIG.
3 was established, and its target value (electrical system accident runback target value) of 52 was added. That is, the basic demand of the unit (M
A switch 5 is connected to the output path of the rate of change limiter 32 to obtain WD) 33.
1, when a runback occurs, the rate of change limiter 3
2, the demand according to the electrical system accident runback target value 52 is selectively outputted, and a switch 53 is interposed in the output path of the regulator (PI) 47 to control the runback. At the time of occurrence, the turbine bypass control valve 8 is activated based on the output of the pressure control regulator (PI) 46.
The configuration is such that the opening degree is controlled.

As a result, when a runback occurs due to an electrical system fault, the switch 51 switches to the output side of the electrical system fault runback target value 52, that is, the runback target value, which is the basic demand (MWD). It became 33,
By the turbine governor regulator 36 of the generator output control system,
The generator output (MW) 21a is automatically controlled to the required target value at the required speed.

On the other hand, the basic demand (MWD) 33 becomes the boiler input command (BID) 38, and the water supply, fuel,
Automatically throttles air to the required command value.

At this time, the output 48 of the pressure control regulator 46
becomes an opening command for the turbine bypass control valve 8 by the switch 53, and the pressure is automatically controlled by the turbine bypass control valve 8 to a predetermined value.

By applying the configuration of the above-described embodiment to a runback circuit of an automatic boiler control system of a thermal power plant, it can be used as an output suppression method in the event of an abnormality such as when generator stator cooling water is lost. Works effectively.

[0033]

[Effects of the Invention] As detailed above, according to the runback method of the present invention, pressure control is performed using a turbine bypass control valve in order to enable generator output control that could not be achieved with conventional runbacks. By configuring it to do this,
It is possible to realize a runback function that can satisfy various demands for output suppression in the event of an electrical system fault, that is, can reduce the generator output to an allowable value within a certain period of time.

[Brief explanation of the drawing]

FIG. 1 is a control system diagram showing one embodiment of the present invention.

FIG. 2 is a flowchart of a power generation unit targeted by the present invention.

FIG. 3 is a conventional control system diagram.

[Explanation of symbols]

1... Water pump (BFP), 2... Forced draft fan (FDF)
, 3...Fuel pump, 4...Water supply adjustment mechanism (water supply adjustment valve),
5... Air conditioning mechanism (air conditioning damper), 6... Fuel regulating mechanism (fuel regulating valve), 7... Turbine governor, 8... Turbine bypass regulating valve, 11... Boiler, 12... Turbine, 13
... Generator, 14... Chimney, 32... Rate of change limiter, 36,3
9, 40, 42, 43, 44, 46, 47,...adjuster (
PI), 51, 53...Switching device, 52...Electrical system fault runback target value.

Claims (1)

[Claims] 1. Means for selectively outputting a demand according to a runback target value specific to an accident in the electrical system in place of an output command of a power generation unit when an abnormality occurs in the electrical system, and means for selectively opening a turbine bypass control valve. The present invention is characterized in that the generator output is controlled by a turbine governor in accordance with the demand when an abnormality occurs in the electric system, and the boiler pressure is controlled by a turbine bypass control valve to throttle the generator output. Runback method in the event of an electrical accident.