JPH0379601B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a control device for a fluid flow rate regulating device in a power generation plant such as a thermal power generation plant, and is particularly suitable for controlling large auxiliary equipment such as a blower or a water pump. This relates to a control device.

[Background of the invention]

First, Figure 1 shows an overview of the entire thermal power plant. In FIG. 1, 1 indicates a boiler automatic control device (hereinafter referred to as ABC device).
This ABC device 1 is responsible for the central control function of a thermal power plant, and immediately responds to the generator load request, that is, the power supply command _Rq , to input the amount of fuel _Fl , water supply W, and air A to the boiler 2. _r etc. to maintain the pressure and temperature of the steam at the inlet of the turbine 3 at specified values regardless of load fluctuations. That is, the ABC device 1 includes a master control device 4 that controls the power generation plant in general, and an inlet of a forced ventilation fan 5 that is a control unit that adjusts the flow rate of combustion air A _r as a fluid based on a control signal from the master control device 4. A combustion control device 6 that controls the damper 23, a steam temperature control device 8 that controls the fuel control valve 7 that adjusts the flow rate of fuel _Fl , a water supply control device 10 that controls the water supply control valve 9, and a steam control valve 12. and an output control device 13 for controlling. Note that 14 is a generator, 15 is a condenser, 16 is a water pump, and 17 is a gas recirculation fan.

On the other hand, as shown in Figure 2, today's power supply systems respond to power demand by comprehensively using three types of power generation plants: nuclear power generation, hydropower generation, and thermal power generation. Figure 2 shows the state of daily load changes, and it can be seen that nuclear power plants, whose output is difficult to control, are used in the base load region, and daily load changes are adjusted by thermal power generation. Note that the base load means the amount that secures the minimum power supply against the daily load change. Figure 3 shows the trends in the amount of electricity supplied throughout Japan by year.As can be seen from Figure 3, the recent operation of thermal power plants has shifted from base load to intermediate load. You can see that Here,
Intermediate load body refers to the load range of 1/4 to 3/4 of rated operation.

For such operations, the ABC shown in Figure 1
The output is controlled by the device 1, but the problem is that the blower of the water supply pump 16 (for example,
This is control of the forced ventilation fan 5). In other words, the combustion air A _r is controlled by the forced draft fan 5 as a fluid regulating section and the damper 23 provided upstream thereof. This was done by operating at low speed and adjusting the opening of the damper 23.
The same applies to the flow rate adjustment of the boiler feed water W, which is generally performed by operating the drive motor of the feed water pump 16 at low speed and adjusting the opening degree of the feed water flow rate control valve 9. In all such systems, the fluid flow rate is controlled by a throttle, for example, the fourth
When the power supply amount is controlled in response to daily load changes as shown in the figure, a loss _Ls occurs due to the damper 23 and the water supply flow rate control valve 9 corresponding to the shaded area in FIG. As can be seen from FIG. 5, the loss is especially large at low loads, and in the current intermediate load operation, the efficiency is poor and the load placed on the damper 23 and the water supply flow rate control valve 9 is large.

Here, the control system of the forced ventilation fan 5 will be explained in more detail by taking as an example. Figure 6 shows the flue duct system of a thermal power plant. The boiler with a forced draft fan has a secret structure, and the furnace 1
Since there is no leakage of outside air from the furnace wall in No. 8, the amount of air required for combustion is determined entirely by the amount of combustion air A _r .
In FIG. 6, in order for the combustion air A _r to be combusted in the furnace 18 and to flow out as a generated gas to the outside through the flue 19, there is a forced ventilation passage 20 and a flue 19.
The pressure must be sufficient to overcome the air resistance of each part. Therefore the combustion air A _r
After being pressurized by the forced ventilation fan 5, the temperature is raised by the air preheater 21 to the optimum temperature for combustion, and after being supplied to the combustion burner device (not shown), it is heated to the flue 19 by the induction fan 22. is released to the outside via the Note that 24 indicates an inlet vane of the induction fan 22. The pressures at various points in the flue system are maintained at values as shown in FIG. That is, the inlet damper 23 of the forced draft fan 5 and the inlet burn 24 of the induction fan 22 are controlled to maintain the pressure value as shown in FIG.
As mentioned above, in the case of such control, conventionally the forced ventilation fan 5 or the induction fan 2 is used.
The drive motor No. 2 was operated at a constant speed, and the flow rate of the combustion air A _r was controlled by adjusting the opening degrees of the damper 23 and the vane 24.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a control device capable of optimal control by cooperatively controlling a flow rate operation section such as a forced ventilation fan or a water supply pump and a flow rate adjustment means such as a damper or a flow rate control valve.

[Summary of the invention]

In order to achieve the above object, the control device according to the present invention controls the flow rate operation section with the opening degree of the flow rate adjustment means being kept open when the load of the power generation plant is below a predetermined value, and The present invention is characterized in that when the value exceeds the flow rate, the flow rate of the fluid is controlled by operating the flow rate operation section in a fixed state and controlling the flow rate adjustment means.

That is, energy saving is achieved by controlling the rotational speed of a fan as a flow rate control unit and a drive motor of a pump, and also controlling the opening degree of a damper or vane in a coordinated manner. We use rotation speed control that has a slow response to the process when the load is below a predetermined load value with relatively little load fluctuation, and damper and vane control that has a good response in the region of a predetermined load value where the load fluctuates significantly. This is to adjust the temperature.

[Embodiments of the Invention] Next, embodiments of a control device for a fluid flow rate regulating device according to the present invention will be described based on the drawings.

FIG. 8 shows a schematic configuration of a control device according to the present invention. Note that the same parts as shown in FIG. 1 are given the same reference numerals, and detailed explanation thereof will be omitted.

In FIG. 8, the forced ventilation fan 5 is driven by a driving induction motor (hereinafter referred to as motor) 26 connected via a clutch 25, and this motor 26 is connected to a circuit breaker from a power bus 27. It receives power supply via 28.
A control device according to the invention is inserted between the circuit breaker 28 and the electric motor 26. The control device includes a rotation control system 30 that controls the rotation of the electric motor 26 by a variable frequency inverter 29, and an aperture control system 31 that directly transmits electric power from the power supply bus 27 to the electric motor 26.
There are two main control systems: Switching between the rotation control system 30 and the aperture control system 31 is performed by switching switches 32 and 33. These changeover switches 32 and 33 are switched according to the load condition by a command signal from the ABC device 1.
That is, when the load value is 3/4 or less of the total load, the switch 32 is turned on and the switch 32 remains open, so that the rotation control system 30 operates and the motor 26 is controlled by variable frequency. . on the other hand,
When the load exceeds 3/4, the switch 32 is opened by a command from the ABC device 1, and the switch 33 is turned on instead. As a result, electric power from the power supply bus 27 is directly supplied to the electric motor 26, and the electric motor 26 is rotated at a constant speed.

On the other hand, when the switch 32 of the rotation control system 30 is turned on, the damper 23 is fixed in a fully open state by a command from the ABC device 1. switch 33
When the damper 23 is turned on, the opening degree of the damper 23 is controlled according to the change in load according to a command from the ABC device 1. Note that 34 indicates a transformer.

Next, FIG. 9 shows details of the ABC device 1 for controlling the present invention. In FIG. 9, it is assumed that the load is currently 3/4 load or less. At this time, monitor relay 35 is under 3/4 load.
It turns ON and outputs a logic signal H. On the other hand, the other monitor relay 36 similarly outputs a logic signal H when the opening degree of the damper 23 is greater than or equal to a predetermined value. These logical signals H are ANDed by an AND circuit 37 and applied to changeover switches 32 and 33. When the output of the AND circuit 37 is H, the changeover switch 32 is closed and the switch 33 is open. Therefore 3/4
Below the load, the speed of the electric motor 26 is controlled by the rotation control system 30 centered on the variable frequency inverter 29.

Now, when the required air flow rate signal V _AD1 of 3/4 load or less is input, this signal is input to the first function generator 38. The characteristic of the first function generator 38 is the 10th
As shown in Figure a, the required air flow rate signal
A predetermined rotational speed signal V _o is output depending on the magnitude of V _AD1 . As can be seen from Figure 10a, its characteristics are as follows: 1/4 load, that is, the required air flow rate signal V _AD1 is 25
% value, the minimum air flow rate is constant, and beyond that, the speed increases at a predetermined rate up to 3/4 load, and above 3/4 load, the speed becomes constant again _.
is generated. The rotational speed signal V _o generated in this way is applied to one input of the addition element 39 .

The other input of the addition element 39 receives a rotation speed increase/decrease bias signal V _b given from the second function generator 40.
is added and corrected. That is, although the current rotation speed control mode is performed by the variable frequency inverter 29, sudden load fluctuations may occur even in cases where the load is 3/4 or less. Therefore, the damper 23 detects the actual air flow rate and corrects for sudden fluctuations. for that,
Input the actual air flow rate signal V _AD2 to the addition element 41,
In addition, the required air flow rate signal V _AD1 is input to the addition element 41, and its deviation value is input to the PI (proportional, integral) controller 42.
The opening adjustment signal _V0 output from the PI controller 42 is input to the second function generator 40, and a predetermined rotational speed increase/decrease bias signal _Vb based on the opening adjustment signal _V0 is sent to the addition element 39. It is something to add. The characteristics of the second function generator 40 are shown in FIG. 10b. In other words, the function of the second function generator 40 based on the actual air flow rate signal V _AD2 is to provide a margin for the adjustment operation of the damper 23. As shown in FIG. 10b, the characteristics of the second function generator 40 are such that when the damper opening becomes more than 80% and less than 20% and there is no margin for adjusting the opening, it increases or decreases the rotation speed of the electric motor 26, and always It is designed to allow a certain amount of leeway in the damper opening. Note that 43 is for outputting to the PI controller 42 via a suitable control gain changeover switch 44 in the rotation control mode. The characteristics of this third function generator 43 are as follows:
As shown in Figure g. On the other hand, 45 outputs an appropriate control gain to the PI controller 42 via the switch 44 in an aperture control mode to be described later. The characteristics of the fourth function generator 44 are shown in FIG.
It is shown in

The rotational speed signal V′ _o corrected in the adding element 39 as described above is applied to the variable frequency inverter 29. Therefore, the variable frequency inverter 29 controls the rotation speed of the electric motor 26 at a rotation speed according to the required air flow rate signal V _AD1 while giving the damper 23 a predetermined margin of opening. As a result, as shown in FIG. 5, the forced draft fan 5 supplies combustion air at a flow rate according to the required air flow rate signal V _AD1 to the furnace 18 through the forced draft passage 20.

Next, although the rotation speed of the electric motor 26 is controlled by the variable frequency inverter 29 at a load of 1/4 to 3/4, the control operation when the load exceeds 3/4 will be explained below. . As mentioned earlier, when the load is 3/4 or more, the occurrence frequency is relatively low, and in that case, throttle control is performed by the damper 23 to reduce the loss and the load on the damper.

Here, FIG. 11 shows the characteristics of the forced ventilation fan 5. In Figure 11, curve A represents system loss (loss due to air resistance in the ventilation system),
Curves B to G show air flow rate (Q)-discharge pressure (h) curves for each rotational speed of the forced draft fan 5 when the damper 23 is opened to 80%. And B is the rated frequency (commercial power supply), C is 90%, D is 80%, and E is
The frequency is 70%, F is 60%, and G is 50%. Also, when B ₁ is 70% damper opening at the rated frequency, B is also 60%, B ₃
is also the Qh curve at 50%.

Assume now that the variable frequency inverter 29 is rotating at 80% frequency, the damper opening is 80%, and the forced ventilation fan 5 is balanced at the intersection b of curves D and A in FIG. Assuming that, when switching from the variable frequency inverter 29 to the throttle control system, the push-in ventilation fan 5 is connected to the power supply bus 27.
The speed will increase to the maximum speed according to the required voltage given from be.
Therefore, the output voltage of the variable frequency inverter 29 is converted into a frequency signal by the f/V converter 46 and input to the fifth function generator 47. Fifth function generator 4
The characteristics of No. 7 are as shown in Figure 10c, and the higher the rotation speed when switching from rotation control to throttle control, the smaller the throttle opening is, and the characteristic is that the throttle opening is reduced to the minimum air flow rate at 1/4 load or less. It is becoming. On the other hand, the damper 23 cannot be tightened suddenly. Therefore, the electric motor 26
The damper 23 must be gradually tightened in a time commensurate with the speed increase rate. Therefore, f/V
The output signal of the converter 46 is input to a sixth function generator 48, and a signal t corresponding to the time corresponding to the speed increase rate is input to a change rate setter 49. The characteristics of the sixth function generator 48 are as shown in FIG. 10d, and provide a speed increase rate commensurate with the speed increase time t up to the rated time when switching from the variable frequency inverter 29 to aperture control. In Figure 10 d, N seconds is 0% rotation speed.
It shows the speed increase time from to 100%. In this way, the change rate setter 49 generates the throttle opening signal Vc based on the throttle opening signal outputted from the fifth function generator 47 and the speed-up time t outputted from the sixth function generator 48. It is input to one terminal of the addition element 50.

A PI controller 42 is connected to the + side terminal of the addition element 50.
Therefore, this opening adjustment signal V ₀ is corrected by the narrowing signal Vc, and is sent to the drive device 51 _as the opening adjustment signal V' ₀ .
supplied to As a result, the drive device 51 controls the damper 23 at a predetermined narrowing change rate mainly using the opening adjustment signal V ₀ from the PI controller ₄₂ based on the deviation between the required air flow rate signal V _AD1 and the actual air flow rate signal V AD2.
The opening will be adjusted.

The above explanation is about the operation when the load changes from low load to high load, that is, from less than 3/4 load to more than 3/4 load. A case will be explained in which the load decreases to 3/4 load or less when opening adjustment, that is, diaphragm control is being performed. In this case, when the load becomes 3/4 or less, the rotation speed signal
Since V′ _o becomes small, monitor relay 35 is turned on.
Therefore, a logic signal H is output. As a result, changeover switch 33 is opened, and changeover switch 32 is closed instead. As a result, the control mode changes to the rotational speed control mode, and the electric motor 26 is controlled by the variable frequency inverter 29 again. At this time, the opening degree of the damper 23 must be adjusted to a predetermined value, but for this purpose, a signal is given from the f/V converter 46 to the seventh function generator 52, and the damper operation rate (change rate ) is applied from the seventh function generator 52 to the rate of change setter 49 via the switch 53. As a result, the drive device 51 of the damper 23 receives the narrowing signal from the rate of change setting device 49.
Adjust the opening according to Vc. The characteristics of the seventh function generator 52 are as shown in FIG. 10e,
Although the characteristics are similar to those of the sixth function generator 48 (FIG. 10d), the speed-up time and deceleration time are different.
In Figure 10e, M seconds is the rotation speed from 100% to 0%.
It shows the deceleration time up to.

Note that 54 is a setting device used when the damper 23 is not narrowed down at all (i.e., 0%), and 55 is a setting device for selecting either the narrowing control signal from the fifth function generator or the signal from the setting device 53. It is a switch.

The operation of the present invention can be summarized as follows. Conventionally, the electric motor 26 is always rotated at a constant speed for the load pattern shown in FIG. 12a, so the amount of air is adjusted according to the load by operating as shown by the dotted line in FIG. 12c. It was hot. However, in the present invention, as shown in FIG. 12b, the rotation speed of the electric motor 26 is controlled by changing the rotation speed commensurate with the load pattern (that is, up to 3/4 load, which has a large operating range in intermediate load operation). Higher load bands, i.e. less frequent 3/
When the load band ratio exceeds 4, the prime mover 26 is operated at the rated rotational speed, and the damper 23 adjusts the amount of air according to the load. Therefore, in the case of the control according to the present invention, the loss due to the damper 23 is only the shaded part on the damper opening curve in FIG. 12c, and the loss is lower than that in the conventional case shown in FIG. can be significantly reduced. Further, the loss can be similarly kept small even at low loads.

In the above embodiment, the control of the combustion air supply system using the forced ventilation fan 5 has been described, but the water supply pump 16 as shown in FIG.
It goes without saying that the present invention can also be applied to load following control of the water supply W by the water supply flow rate control valve 9. When applied to the water supply pump 16 and the water supply flow rate control valve 9, the water supply pump is used instead of the forced draft fan 5, the water supply flow rate control valve 9 is used instead of the damper 17, and other designs are made to suit the water supply system. Bye.

〔Effect of the invention〕

As described above, according to the present invention, when the load of the power generation plant exceeds a predetermined value, the flow control section is controlled with the opening degree of the flow control means kept open, while when the load exceeds the predetermined value. Since the configuration is such that the fluid flow rate is controlled by coordinated control by operating the flow rate operation section in a fixed state and controlling the flow rate adjustment means, optimal control can be performed in response to changes in load.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the overall outline of a typical thermal power plant, Figure 2 is an explanatory diagram showing the power generation plant's share of responsibility for electricity demand, and Figure 3 shows changes in the amount of power supplied by year. Figure 4 is an explanatory diagram showing the daily load change state, Figure 5 is an explanatory diagram showing the loss of the inlet damper of a forced ventilation fan, Figure 6 is a block diagram of the smoke and wind duct system of a thermal power plant, FIG. 7 is an explanatory diagram showing pressure values at various points in the smoke duct system, FIG. 8 is a circuit diagram showing an overview of the control device according to the present invention, and FIG. 9 is a diagram according to the present invention.
A block diagram showing the configuration of the ABC device, Fig. 10 is a characteristic diagram showing the characteristics of each function generator, Fig. 11 is a characteristic diagram showing the flow rate (Q) - discharge pressure (H) curve of the forced ventilation fan, and Fig. 12 The figure is an explanatory diagram for explaining the effect of the control of the present invention. 1... ABC device, 2... Boiler, 5... Forced draft fan, 9... Water supply flow rate control valve, 16... Water supply pump, 23... Inlet damper, 26... Electric motor, 32, 33... Selector switch , A _r ...Combustion air, V _AD1 ...Required air flow rate.

Claims (1)

[Scope of Claims] 1. In a control device for a fluid flow rate adjustment device provided in a power generation plant, the control device includes a flow rate operation section by adjusting the rotation speed and a flow rate adjustment means by adjusting the valve opening degree.
When the load of the power generation plant is in a predetermined value range, the rotational speed of the flow control section is controlled with the valve opening degree of the flow rate regulating means being adjusted to a constant value, and the required flow rate and the actual flow rate based on the load are controlled. The valve opening degree of the flow rate adjusting means is controlled in the vicinity of the constant opening degree according to the deviation of the flow rate, and when the load is outside a predetermined value range, the flow rate adjusting means is controlled with the flow rate operation part fixed. A control device characterized by controlling a flow rate by: 2. The control device according to claim 1, wherein the predetermined region ranges from approximately 3/4 load to approximately 1/4 load. 3. The control device according to claim 1, wherein the constant opening degree of the flow rate adjusting means is approximately 80%.