JPS637246B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a load control device for a combined cycle power generation plant (hereinafter referred to as a combined cycle plant) using a gas turbine and a steam turbine. In particular, the present invention relates to a load change rate limiting circuit that limits the load change rate of the combined cycle plant within a range that the plant can tolerate.

[Technical background of the invention]

Overview of a combined cycle plant A combined cycle plant is a gas turbine that burns fuel to rotate a generator, recovers the exhaust heat in a boiler to generate steam, and uses the generated steam to drive a steam turbine. This refers to a power generation plant that uses a system that also drives a generator. In this sense, it is also called a combined cycle or combined cycle plant. The overall output of this combined cycle plant depends on the amount of fuel supplied to the gas turbine, and therefore, by controlling this fuel flow rate, the output of the entire plant can be controlled.
In general, combined cycle plants are broadly classified into single-shaft types and multi-shaft types, depending on whether the gas turbine and steam turbine are connected by the same shaft or separated into multiple shafts.

Load Control Next, the load control device for the above-mentioned combined cycle plant will be described. To simplify the explanation, an example of a single-shaft type combined cycle plant will be used (see FIG. 1). In FIG. 1, first, the output control of the gas turbine 9 is as follows. The speed setting signal from the speed setter 1 is given to the subtracter 2. On the other hand, rotation speed detection signals of the gas turbine 9 , the steam turbine 13 , and the generator 10 are fed back to the subtractor 2 from the rotation speed detector 6 provided in the compressor 8 . The subtracter 2 calculates the deviation between the speed setting value and the detected value fed back, and outputs the deviation signal to the operational amplifier 3. The operational amplifier 3 performs a "proportional" or "proportional integral" calculation based on the input deviation signal, and sends the calculated value to the fuel regulating valve 5 via the servo amplifier 4 to control its opening degree. By this opening adjustment, the fuel flow rate supplied to the combustor 7 of the gas turbine 9 is controlled,
As a result, the output of the gas turbine 9 is controlled to match the speed setting.

Next, output control of the steam turbine 13 will be described. From the exhaust heat recovery boiler 11 to the steam turbine 13
The steam enthalpy supplied to the gas turbine is determined by the enthalpy of the exhaust gas from the gas turbine 9, so by keeping the steam control valve 12 fully open or at a constant opening, it can be uniquely determined in relation to the vacuum degree of the condenser 14. Turbine output will be determined.

From the above, in the combined cycle plant, the output to the power system is a value obtained by multiplying the sum of the outputs of the gas turbine 9 and the steam turbine 13 by the efficiency of the generator 10.

The load (generator output) is controlled by the load setting device 16.
The subtractor 17 calculates the deviation between the load setting signal from the load detector 15 and the actual load detection signal from the load detector 15, and the calculated deviation signal is applied to the speed setting device 1 to control the setting device 1. As a result, it is possible to control the deviation so that it ultimately becomes zero (that is, the load becomes equal to the load setting value).

Comprehensive load control of a multi-shaft combined cycle plant A combined cycle plant with the above characteristics is a multi-shaft type, and when the combined cycle plant is planned to function as one unit from the perspective of the power system. An example of a comprehensive load control device is shown in Fig. 2.

In FIG. 2, either the combined cycle plant load command value given from the central power supply station 18 or the station mode load command value given from the load setter 20 is selected by the switch 19 and input to the adder 21. Ru. On the other hand, a frequency bias signal from a frequency deviation bias generator 22 for compensating for system frequency deviation is input to an adder 21, and both signals are added. The added signal is subtracted by the subtracter 23 from the output of the entire combined cycle plant (the sum of the combined cycle plant outputs from the first axis A ₁ to the nth axis An) given from the adder 24 to obtain a deviation. This deviation is then input to the proportional integrator 25, which is the overall load controller.
The proportional integrator 25 issues a load target command for each axis based on the input deviation value. A subtracter ₂₇ , a generator output detector 26, and a proportional-integral calculator 28 are provided for each axis A1 to _Ao , respectively. These are all the same for each axis A ₁ to A _o , so they are indicated by the same reference numerals.

Now, the load target command is subtractor 2 for each axis A ₁ to _{A o.}
7, each subtractor 27 performs subtraction with the detection signal from the generator output detector 26 of each axis, and outputs the deviation to the proportional-integral calculator 28.
The proportional-integral calculator 28 outputs speed setting signals for each axis A ₁ to _{A o} based on the input deviation value.
The following operation is the same as the control operation in FIG. 1, and the speed setting signal is sent to each axis A ₁ to
The output of the combined cycle plant is controlled by the control device shown in _FIG .

[Problems with background technology]

In the single-shaft type and multi-shaft type combined cycle plants as described above, when changing the load, it is necessary to give a load command at a rate of change within a range that the plant can tolerate. The reason is as follows. Since the output of a gas turbine depends on the amount of fuel, a sudden change in the load command will cause a sudden change in the amount of fuel, resulting in a sudden change in the gas turbine inlet temperature. It appears as a sudden change in temperature.
Such changes lead to generation of thermal stress in the steam turbine, which is undesirable from the viewpoint of turbine life management. Therefore, changes in the load command must be limited to within a rate of change that can be tolerated by the plant. This is true not only for single-shaft types but also for multiple axes, and especially in the case of multiple axes, it is necessary to limit the load command not only for each axis A ₁ to _{A o} individually but also for the entire plant. be. Factors that limit the rate of load change include a sudden rise in turbine inlet temperature, the lifespan of the steam turbine due to a sudden rise in steam temperature, and restrictions on preventing NOx generation. Figure 3 shows the load change rate [MW/min] taking into consideration these limitations and operational limitations. In Figure 3, the horizontal axis is the actual load value [MW].

[Purpose of the invention]

The present invention is a load control device for a single-shaft or multi-shaft combined cycle plant, which automatically limits the load change rate so as not to exceed an allowable load change rate according to the current actual load state, thereby achieving smooth control. The purpose of the present invention is to provide a load control device that enables the following.

[Summary of the invention]

In order to achieve the above object, a load control device according to the present invention includes a function generator that receives an actual load state signal of the combined cycle power plant and outputs a signal indicating a limit of the load change rate at the time of the load; The present invention is characterized by comprising a load change rate limiter that adds the load change rate limit signal from the function generator to the load command signal.

[Embodiments of the invention]

Embodiments of the load control device according to the present invention will be described below with reference to the drawings. FIG. 4 shows an example of a load control device for a multi-shaft combined cycle plant. In FIG. 4, parts that overlap with those in FIG. 2 are given the same reference numerals and will be described below.

In the load change rate limiting circuit according to the present invention shown in FIG. 4, a detection signal (MW) is given to the function generator 31 from a load detector 35 that detects the current actual load state of the combined cycle plant. These are provided for each axis A ₁ to A _o . A load change rate corresponding to the actual load value is set in advance in the function generator 31, and the load change rate R ₁ to be limited at that time is set as a function of the input actual load detection value.
Output R _o . The load change rate signals R ₁ to R _o are provided to an adder 34 and each axis A ₁ to A _o , respectively, via a switch 32 and applied to a load change rate limiter 30 . The switch 32 is used when manually setting the minimum load, and the increase/decrease signal is transferred to the integrator 3 during manual operation.
Switch operation to output via 3. The adder 34 calculates the sum of each load change rate signal for all axes _A1 to _Ao , and the calculated value is sent to the load command signal of the general load control system (the general load setter 2) by the limiter 29.
output from 0). That is, each axis A ₁ ~
The total load factor signal for A _o is added to the load command of the general load control system, and at the same time is added to the load command of each axis (output of the general load controller 25).

The above has described an example in which the present invention is applied to a multiple-shaft combined cycle plant, but it goes without saying that the present invention can be similarly applied to a single-shaft type plant.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to set an appropriate load increase/decrease rate according to the current load state of the combined cycle plant, thereby enabling smooth control.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing an example of the configuration of a load control device for a conventional combined cycle plant (single-shaft type).
Figure 2 is a block diagram showing a configuration example of a general load control device for a conventional combined cycle plant (multi-shaft type), Figure 3 is an explanatory diagram showing the load change rate with respect to actual load, and Figure 4 is a load diagram according to the present invention. FIG. 2 is a block diagram showing an embodiment of a control device. DESCRIPTION OF SYMBOLS 1...Speed setter, 2...Subtractor, 3...Operation amplifier, 4...Servo amplifier, 5...Fuel adjustment valve, 6...Rotation speed detector, 7...Gas turbine combustor, 8... ...compressor, 9...gas turbine, 10...generator, 11...exhaust heat recovery boiler,
12...Steam control valve, 13...Steam turbine, 1
4...Condenser, 15...Load detector, 16...Load setter, 17...Subtractor, 20...Load setter, 25...Proportional integrator (general controller),
29...Overall load factor limiter, 30...Each axis load factor limiter, 31...Function generator, 34...Adder.

Claims (1)

[Scope of Claims] 1. In a load control device for a combined cycle power plant that drives a steam turbine with steam generated using exhaust heat of a gas turbine, the load control device receives an actual load state signal of the combined cycle power plant and controls the load control device. The present invention is characterized by comprising a function generator that outputs a signal indicating the limit of the load change rate under load, and a load change rate limiter that adds a load change rate limit signal from the function generator to the load command signal. Load control device for combined cycle power generation plants. 2. In the device according to claim 1,
A load control device for a combined cycle power plant, characterized in that the combined cycle power plant is a single-shaft type in which a gas turbine, a steam turbine, and a generator are connected together on the same shaft. 3. In the device according to claim 1,
A load control device for a combined cycle power plant, characterized in that the combined cycle power plant has multiple shafts in which each combination of a gas turbine and a generator, and a steam turbine and a power generator are connected by different shafts. 4. In the device according to claim 3,
A combined cycle power plant is 1 from the power system perspective.
1. A load control device for a combined cycle power plant, characterized in that the load control device is controlled by a general load control device so as to function as one unit. 5 In the device according to claim 3 or 4, when the combined cycle power generation plant has multiple axes, the load change rate limit signal is combined with the overall load command signal of the entire plant and the load command signal of each axis. A load control device for a combined cycle power generation plant characterized by providing the following: