JPH0435602B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a turbine control device for a turbine plant, and particularly to a pressure change control device for a turbine.

Conventionally, the amount of electricity demanded has fluctuated, reaching a maximum during the day and decreasing at night. In line with this, thermal power generation turbine plants are being forced to operate at intermediate or low loads in order to reduce the amount of power generated.

Generally, in a turbine plant, constant pressure operation is applied in which the inflow steam pressure of the turbine is kept constant. Turbine output during constant pressure operation is controlled by controlling the opening degree of a regulating valve provided at the turbine inlet in accordance with the load factor to control the flow rate of steam flowing into the turbine. usually,
This control valve is divided into a plurality of parts depending on the rated steam flow rate. FIG. 1 shows the relationship between the load factor, the opening degree of the regulating valves, and the turbine internal efficiency during constant pressure operation of a turbine equipped with four regulating valves. The horizontal axis of Figure 1 A and B is the load factor W
%, on the vertical axis, A is the steam pressure P% at the inlet of the control valve and the turbine internal efficiency ηγ%, and B is the opening degree S% of each control valve. Steam pressure P is maintained at a constant rated pressure (100%) as shown in line 1, and as shown in line B, the first to fourth regulating valves are controlled according to the load factor W. They are controlled along the opening degrees S shown by lines 2 to 5, respectively. It is known that the turbine internal efficiency ηγ controlled in this manner decreases as the load factor becomes lower, as shown by curve 6 in FIG. 1A. This decrease in efficiency ηγ is
It is known that this is caused by throttling loss of the control valve and loss due to changes in the flow state of steam inside the turbine due to a decrease in the volumetric flow rate _FV of the amount of steam flowing into the turbine.

Against this background, and on the other hand, due to the soaring fuel price, in recent years, the thermal efficiency of turbine plants has been reduced by reducing the steam pressure P according to the load factor W at low and intermediate load factors. However, attempts are being made to reduce the unit cost of power generation by applying variable voltage operation, which can be improved to save energy.

FIG. 2 shows the relationship among the load factor, the steam pressure, the opening degree of the control valve, and the turbine internal efficiency when the same turbine plant as the example shown in FIG. 1 is operated under variable pressure.

The horizontal axis of FIGS. 2A and 2B is the load factor W%, the vertical axis A is the steam pressure P% and the turbine internal efficiency ηγ%, and B is the opening degree S% of each control valve. As shown by line 7 in FIG. 2B, the opening of the first regulating valve is controlled in proportion to the load factor up to the load factor _W1 , as in the case of constant pressure operation. When the load factor W becomes ₁ or more, the first,
The second and third regulating valves are set to a reference opening close to fully open, and until the load factor _W2 , the steam pressure P is maintained at a constant slope shown by line 8 in the figure, which is determined by making it correspond to the load factor. Turbine output is controlled by variable pressure operation controlling increasing pressure. Also, load factor
When the steam pressure exceeds W ₂ , the steam pressure is maintained at a constant value of the rated pressure, and the turbine output is controlled by controlling the opening degree of the fourth regulating valve. According to such variable pressure operation, the throttling loss of the regulating valve and the loss due to the turbine internal flow state are improved, and the turbine internal efficiency ηγ as shown by the illustrated curve 9 can be obtained.

Generally, when the steam pressure of the turbine is lowered, thermodynamic loss increases due to pressure reduction, but it is known that the thermal efficiency ηp of the turbine plant as a whole is improved. This will be explained using FIG. 3. In FIG. 3, the horizontal axis represents the load factor W%, and the vertical axis represents the increase in heat consumption rate ΔH%; when ΔH is positive, it represents a decrease in the thermal efficiency ηp, and when it is negative, it represents an improvement in ηp. The thermodynamic loss due to the variable pressure operation shown by curve 11 increases as the steam pressure decreases as the load factor decreases. However, by performing variable pressure operation, as shown in the figure, the turbine internal efficiency ηγ is improved 12, the boiler feed water pump shaft power is reduced 13, and the boiler steam temperature characteristics are improved 14 The overall increase in heat consumption ΔH becomes negative as shown by curve 15, and the thermal efficiency ηp is improved as a whole.

As described above, in conventional variable pressure operation, the steam pressure is controlled using pressure patterns determined in correspondence with low and intermediate load factors to improve the thermal efficiency of the entire plant. However, if, for example, the amount of extracted air from the turbine changes at the same load factor, the steam flow rate must be controlled by controlling the opening degree of the regulating valve. In addition, other factors that cause the steam flow rate to fluctuate regardless of the load factor include fluctuations in the degree of vacuum in the condenser and changes in turbine performance over time. For this reason, conventionally, the first to third regulating valves were not fully opened, but were set to a standard opening with enough controllable opening margin to accommodate the fluctuations in the steam flow rate, and throttle control was performed in response to the fluctuations in the steam flow rate. Therefore, there remained room for improvement in throttling loss and turbine internal efficiency. for example,
As shown by line 17 in Figure 4, the steam weight flow rate F _W
If the control valve is used to throttle the 5% decrease in , the turbine plant thermal efficiency ηp will decrease by 0.2%. In contrast, the steam pressure P is adjusted according to line 18 without throttling with a regulating valve.
If you perform variable pressure operation to reduce the pressure by 4.2%, the volumetric flow rate F _V
is constant, so the thermal efficiency ηp of the turbine plant
does not decrease.

Furthermore, due to the above-mentioned soaring fuel prices, turbine plants have come to use many different types of fuel. Therefore, since the amount of air extracted from the turbine often varies depending on the type of fuel, etc., in the case of variable pressure operation with a constant pressure pattern corresponding to the conventional load factor described above, it is necessary to improve the thermal efficiency of the turbine plant. It was not possible to achieve a satisfactory result.

An object of the present invention is to provide a variable pressure control device for a turbine plant that can improve thermal efficiency by performing variable pressure operation in response to fluctuations in the flow rate of steam such as extracted air that fluctuates regardless of the load factor.

The present invention provides a control valve that controls the flow rate of steam flowing into the turbine according to a deviation between a turbine output target signal and an output detection signal, and a control valve that detects the inlet steam pressure of the control valve and outputs a pressure detection signal. a pressure detector; a function generator that outputs a pressure setting signal having a certain correlation in accordance with the output target value; and a function generator that compares the pressure setting signal with the pressure detection signal and outputs a pressure correction signal. 1 subtracter and a first adder that adds the pressure correction signal and the output target signal and outputs a boiler control signal. an opening detector that detects the opening and outputs an opening detection signal; and an opening setting device that outputs an opening setting signal corresponding to a constant reference opening independent of the output target value of the control valve. a second subtractor that compares the opening degree setting signal and the opening degree detection signal and outputs an opening degree deviation signal; By additionally providing a second adder for correcting the pressure setting signal inputted to the device, variable pressure operation can be performed in response to fluctuations in steam flow rate such as bleed air that fluctuates regardless of the load factor, The aim is to improve thermal efficiency.

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 5 shows a schematic diagram of the configuration of a turbine plant according to an embodiment of the present invention.

As shown in FIG. 5, a boiler feed pump 22 is connected to the boiler 21. Boiler 21
The steam generated by the pipe 23 and the control valve 24
It is supplied to the turbine 25 via. A generator 26 is engaged with the turbine 25 . The output target value signal 34 of the generator 26 is input to the boiler control device 27, the pressure setting circuit 28, and the regulating valve control circuit 29, respectively. The boiler control device 27 is connected to a boiler control operation end 30. A pressure detector 31 provided on the inlet side of the regulating valve 24 and an opening detector 32 of the regulating valve 24 are connected to the pressure setting circuit 28, and this pressure setting circuit 28 is connected to the boiler control device 27. It is connected. An output detector 33 is provided at the output end of the generator 26, and the output detector 33 is connected to the regulating valve control circuit 29, which in turn is connected to the regulating valve 24.

FIG. 6 shows a detailed control block diagram of the voltage transformation control device according to the present invention of the embodiment shown in FIG. Components in the figure with the same reference numerals as in FIG. 5 have the same parts and functions.

In the figure, an output target value signal 34 input to the pressure setting circuit 28 is input to a function generator 35. The opening degree setter 36 is connected to the + input terminal of a second subtractor 37, and one input terminal of this subtractor 37 is connected to the opening degree detector 32. The output end of this subtracter 37 is connected to a second adder 39 via an integrator 38, and the other input end of this adder 39 is connected to the function generator 35. The output terminal of this adder 39 is connected to a first subtracter 40
The subtracter 40 is connected to its + input terminal, and the pressure detector 31 is connected to its - input terminal. Furthermore, the output terminal of this subtracter 40 is connected to the PI calculator 41.
via the first adder 42 of the boiler control device 27
connected to the input end of the The output target value signal 34 is input to the other input terminal of the adder 42, and the output terminal is connected to the boiler control circuit 43.

Further, the output target signal 34 input to the control valve control circuit 29 is input to the + input terminal of the third adder 44, and the output detector 33 is connected to the - input terminal of the subtracter 44. ing. This subtractor 4
The output end of 4 is connected to the control valve 24 via a PI calculator 45.

The operation of the embodiment configured as above will be explained.

In order to set the inflow steam pressure of the turbine according to the load factor, the function generator 35 generates a pressure pattern function determined with a certain correlation with the load factor, and corresponds to the input output target value signal. This outputs a pressure setting signal. In addition, the control valve 2
The opening degree setting device 36 of No. 4 is set to output an opening degree setting signal corresponding to a reference opening degree determined from an optimum opening degree that takes controllability into consideration and improves the thermal efficiency of the turbine plant.

By receiving the output target signal, the boiler control circuit 43 controls the generated pressure using the boiler control signal output from the adder 42. Further, in the regulating valve control circuit 29, the deviation is calculated from the output target value signal and the output detection signal by a subtractor 44,
This deviation signal is processed by a PI calculator 45.
Based on this, the opening degree of the adjustment valve 24 is controlled,
The output is controlled to match the target value by increasing or decreasing the steam flow rate of the turbine. On the other hand, as described above, the function generator 35 outputs a pressure setting signal corresponding to the output target value signal. If no signal is input from the integrator 38 to the adder 39, the subtracter 40 takes the deviation between the pressure setting signal and the pressure detection signal, and this deviation is
Processed by the PI calculator 41 and added to the adder 42
is input. As a result, a boiler control signal is output from the adder 42, and the boiler control circuit 43 and the boiler operating end 30 control the increase and decrease of the boiler water supply, fuel, air amount, etc. based on this signal, and the steam pressure is controlled by the load. The pressure is controlled according to the rate.

What has been described above is variable pressure control when the variable factors unrelated to the load factor, such as the amount of extracted air, match the turbine plant plan, but the thermal efficiency is sufficiently improved compared to constant pressure operation.

Next, a case will be described in which the amount of extracted air from the turbine changes even though the load factor, that is, the output target value is constant.

When the flow rate of steam extracted from the turbine 25 changes, the control valve 24 is first operated to maintain a constant output target value. As a result, the opening degree of the adjusting valve deviates from the reference opening degree. The opening degree at this time is detected by the opening degree detector 32 and the subtracter 3
7 is input. This subtracter 37 calculates the deviation between the opening detection signal and the opening setting signal, and this deviation is processed by an integrator 38 and input to an adder 39 as an opening deviation signal. This adder 39
The pressure setting signal output from the function generator 35 is corrected based on the opening deviation signal.
As a result, the boiler is controlled and the steam pressure is controlled to the corrected pressure, so that the opening degree of the regulating valve is returned to the reference opening degree.

Therefore, according to this embodiment, the steam pressure is controlled according to the load factor, and the steam pressure is also controlled in accordance with the steam flow rate of bleed air, etc., which fluctuates independently of the load factor, so that the control valve can be controlled. Since the opening degree is controlled to the optimum opening degree with little loss, the thermal efficiency of the turbine plant can be significantly improved.

In addition, each circuit that calculates the deviation of the adjustment valve opening and corrects the pressure setting value is provided with an upper and lower correction limiter, and the correction calculation is locked when the plant is rapidly throttled down due to a system failure. It is possible to strengthen the

As explained above, according to the present invention, variable pressure operation can be performed in response to variations in the load factor and variations in the flow rate of steam such as extraction air that fluctuates regardless of the load factor, thereby improving the thermal efficiency of the turbine plant. This has the effect of significantly improving the

[Brief explanation of drawings]

Figure 1A is a diagram showing the relationship between load factor W, steam pressure P, and turbine internal efficiency ηT in conventional constant pressure operation, and Figure 1B is a diagram showing the relationship between load factor W and regulating valve opening S. , Figure 2A is a line diagram showing the relationship between load factor W, steam pressure P, and turbine internal efficiency ηT in conventional variable pressure operation, and Figure 2B is a line diagram showing the relationship between load factor W and regulating valve opening S. Figure 3 is a diagram to explain the thermal efficiency improvement by variable pressure operation, Figure 4 is a diagram showing the relationship between the steam weight flow rate reduction rate, the turbine plant thermal efficiency reduction rate and the steam pressure reduction rate, and Figure 5 6 is a schematic diagram of the configuration of a turbine plant according to an embodiment of the present invention, and FIG. 6 is a partial detailed control block diagram of the embodiment shown in FIG. 24... Regulating valve, 25... Turbine, 32...
Opening degree detector, 33...Output detector, 34...Output target value signal, 35...Function generator, 36...Opening degree setter, 37...Second subtractor, 39...Second Adder, 40...first subtracter, 42...first adder.

Claims (1)

[Claims] 1. A control valve that controls the flow rate of steam flowing into the turbine according to the deviation between the output target signal and the output detection signal of the turbine, and a pressure detector that detects the inlet steam pressure of the control valve and outputs a pressure detection signal. a function generator that outputs a pressure setting signal having a certain correlation in response to the output target value signal; and a first function generator that outputs a pressure correction signal by comparing the pressure setting signal and the pressure detection signal. In a pressure transformation control device for a turbine plant, comprising a subtracter and a first adder that adds the pressure correction signal and the output target value signal to output a boiler control signal, an opening detector that detects and outputs an opening detection signal; an opening setting device that outputs an opening setting number corresponding to a constant reference opening independent of the output target value of the control valve; a second subtracter that compares the opening setting number with the opening detection signal and outputs an opening deviation signal; and the opening deviation signal is output from the function generator and input to the first subtracter. A pressure transformation control device for a turbine plant, further comprising a second adder for correcting the pressure setting signal.