JP5320037B2 - Boiler automatic control device and boiler system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and a method of automatically controlling a boiler and a boiler system suitable for exhibiting energy saving effects by an inverter while maintaining control performance of conventional technologies, in the device of automatically controlling the boiler for controlling a flow rate or pressure of air or combustion gas within the boiler to a specified value. <P>SOLUTION: The method of automatically controlling the boiler is used for detecting physical quantity of fluid sent to inside of the boiler, preparing a physical quantity command to control the physical quantity of the fluid to a specified value, calculating a deviation between the physical quantity of the fluid and the physical quantity command, and controlling the fluid quantity based on the deviation. When the deviation is lower than a predetermined value, the physical quantity of the fluid is controlled at a higher change ratio, compared to when the deviation is higher than the predetermined value. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a boiler automatic control device, a control method, and a boiler system.

  Thermal power plants generate electricity by generating high-temperature and high-pressure steam in a boiler and rotating a steam turbine. Conventionally, a commercial frequency power source is used as power for the ventilator in the boiler system, and the motor output (rotational speed) of the ventilator is driven constant in the normal operation state. Therefore, control of the boiler internal pressure and the like of the boiler is performed by a flow rate adjusting operation end that adjusts the flow rate of the fluid (air or combustion gas) passing through the ventilator. However, the conventional technology does not consider the case where an inverter (frequency converter) is applied to large-capacity ventilation for thermal power generation, and there is a problem that pressure control in the furnace and ventilator motor output control by the inverter cannot be established. there were.

  In order to solve the above-mentioned problem, for example, Patent Document 1 discloses a technique for controlling the flow rate adjusting operation end by proportional-integral calculation and controlling the inverter output of the ventilator motor by a program corresponding to the boiler load.

Japanese Patent No. 3944405

  In the above technique, the flow rate adjusting operation end using the inlet vane as an example guarantees that it is possible to cope with a transient change in the air flow rate in which the inverter output cannot follow both the increasing direction and the decreasing direction. For this reason, during normal operation, the opening degree of the flow rate adjusting operation end is constantly reduced by a constant opening degree, so there is a problem that the motor output of the ventilator needs to be increased accordingly and energy is consumed.

  An object of this invention is to provide the boiler automatic control apparatus suitable for suppression of the motor output of ventilation, the control method, and a boiler system in view of the said subject.

  The above problem is to detect a physical quantity of a fluid sent into a boiler, create a physical quantity command for controlling the physical quantity of the fluid to a specified value, calculate a deviation between the physical quantity of the fluid and the physical quantity command, and calculate the deviation. A boiler automatic control method for controlling the amount of fluid based on the method, wherein the physical quantity of the fluid is controlled at a higher rate of change when the deviation is lower than a predetermined value than when the deviation is higher than a predetermined value. Will be solved.

  According to the present invention, since the rotation speed of the aerator motor can be reduced, the output of the inverter, which is the motor power, can be suppressed accordingly.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows a configuration of a boiler and a control device of a thermal power plant to which the present invention is applied. A boiler and a control device of a thermal power plant include a furnace 1 that burns fuel and generates steam by heat exchange, a forced air blower 2 (hereinafter abbreviated as “FDF”) that blows combustion air to the furnace 1, and FDF motor 3 that is the power of FDF 2, FDF inlet vane 4 that adjusts the amount of air blown by FDF 2, FDF inlet vane control drive 41 that drives FDF inlet vane 4, chimney 5, and air blown to furnace 1 An air flow rate detector 6 that detects the flow rate, an inverter device 7 that controls the rotational speed of the FDF motor 3, and a boiler automatic control device 8 that performs comprehensive control of the process amount of the boiler.

  In addition, in this embodiment, in order to explain the case where an inverter is applied to a forced air blower of a thermal power plant, the boiler has only one flue channel system, and the ventilator is configured by only a forced air fan. In addition to this example, an induction ventilator for exhausting combustion gas and a coal-fired boiler with a primary ventilator that blows air for conveying pulverized coal, A configuration having two road systems is conceivable. The control device according to the present invention can also be applied to control of each ventilator in the boiler configured as described above.

  Next, the function of each element shown in FIG. 1 will be described. The furnace 1 takes in combustion air sent from the FDF 2 and burns fuel to generate high-temperature and high-pressure steam and rotate a steam turbine (not shown). The chimney 5 discharges exhaust gas generated by combustion in the furnace 1. The air flow rate detector 6 detects the air flow rate sent to the furnace 1 and sends an air flow rate signal 11 to the boiler automatic control device 8.

  Here, the amount of air sent into the furnace 1 must be controlled to an amount necessary for combustion of the fuel charged into the furnace 1 and so that the oxygen concentration in the exhaust gas becomes a specified value. An air flow rate command calculation unit (not shown) calculates an air flow rate command 14 from the amount of fuel input to the furnace 1 and the oxygen concentration of the exhaust gas discharged from the chimney 5 and sends it to the boiler automatic control device 8 so that the specified value is obtained. .

  The boiler automatic control device 8 calculates the calculation result of the control arithmetic circuit built in the boiler automatic control device 8 from the air flow rate signal 11 sent from the air flow rate detector 6 and the air flow rate command 14 sent from the air flow rate command calculation unit. On the basis of the FDF inlet vane opening command 18 and the FDF rotational speed command 13, and send them to the FDF inlet vane control drive 41 and the inverter device 7, respectively. The boiler automatic control device 8 is a device that controls the generator output, steam temperature, pressure, and the like in addition to the above, but only functions related to the present invention will be described here.

  The FDF control drive 41 drives the FDF inlet vane 4 based on the FDF inlet vane opening degree command 12 sent from the boiler automatic control device 8. The FDF inlet vane 4 is an operation end for adjusting the amount of air blown from the FDF 2, and is driven by the FDF control drive 41 to control the amount of air passing through the FDF 2.

  On the other hand, the amount of air blown from the FDF 2 can also be adjusted by increasing or decreasing the rotational speed of the FDF motor 3 by the inverter device 7. The inverter device 7 adjusts the inverter output based on the FDF rotational speed command 13 sent from the boiler automatic control device 8, and the rotational speed (frequency) of the FDF motor 3 is equal to the FDF rotational speed command 13 from the boiler automatic control device 8. Control to be the same. The FDF motor 3 is driven by the power of the inverter device 7 and drives the fan of the FDF 2 to control the amount of air blown from the FDF 2.

  The FDF 2 adjusts the amount of air sent to the furnace 1 by the FDF inlet vane 4 and the FDF motor 3 to a specified value, and the oxygen concentration in the exhaust gas is a specified value to an amount necessary for combustion of the fuel charged into the furnace 1. Control to be

  Next, the detailed control function of the boiler automatic control device 8 according to the present invention will be described with reference to FIG. The subtractor 801 is an air flow rate command (hereinafter referred to as AFD) 14 (hereinafter referred to as AFD) 14 calculated from the air flow rate signal 11 (PV) input from the air flow rate detector 6 and the oxygen concentration in the fuel and exhaust gas supplied to the furnace 1. The air flow rate deviation signal 15 (SV-PV) is calculated from SV).

  Here, the air flow rate deviation signal 15 is used for two signal calculations. One is sent to the proportional-plus-integral calculator 804, and the proportional-plus-integral calculator 804 performs a proportional-integral calculation on the air amount deviation signal 15, and the FDF rotation speed control signal 17 (K2 × (SV−PV) + K3 × ∫ (SV−PV) ) Dt) is generated and sent to the change rate limiter 805. At this time, the proportional-plus-integral calculator 804 continuously integrates during the boiler control by the integral term ∫ (SV-PV) dt.

  Here, the change rate of the inverter output is determined by the characteristics of the inverter device 7, and the inverter output cannot follow even if the FDF rotation speed command is given to the inverter device at a change rate exceeding the operable range of the inverter. Therefore, the command to the inverter device 7 needs to be limited to the operable range of the inverter device 7. The change rate limiter 805 is provided for this purpose, and if the change rate of the FDF rotation speed command 17 sent from the proportional-plus-integral operation unit 804 is less than the operable range of the inverter device 7, no processing is performed and the FDF rotation speed command 17 If the change rate of the inverter device 7 is greater than or equal to the operable range of the inverter device 7, the signal is limited to be less than or equal to the operable range of the inverter device 7, and the final FDF rotation speed command 13 is sent to the inverter device 7.

  The air flow deviation signal 15 used for the other signal calculation is sent to the function generator 802. The function generator 802 inputs the air flow rate deviation signal (SV-PV) 15 to the function fx as the input value x, and outputs the FDF inlet vane control signal 16 (f (SV-PV)) to the proportional gain multiplier 803. . The function f (x) generated by the function generator 802 is shown below.

When x <a f (x) = x + b Equation (1)
When a ≦ x, f (x) = 100 Equation (2)

  However, a and b are constants, and in particular, a is set to a negative value. The air flow rate deviation signal 15 (SV-PV) calculated by the subtractor 801 is input to the function generator 802 as an input value x, and the function generator 802 receives the FDF inlet vane control signal 16 (f (SV-PV)). Output. However, the output of the function generator 802 represents a percentage (%) with the fully opened FDF vane opening being 100%. Here, a linear function of x is used as the function f (x) when x <a. However, the function is not limited to this. For example, a function higher than a quadratic function, an exponential function, or a step function may be used.

  The output value of the FDF inlet vane control signal 16 with respect to the input value of the air quantity deviation signal 15 of the function generator 802 is shown in graph 19 (horizontal axis: air quantity deviation signal 15, vertical axis: FDF inlet vane control signal 16). As shown in the graph 19, when the air flow deviation signal 15 is positive, that is, when the air is insufficient, a signal that outputs 100%, that is, the FDF inlet vane is fully opened, is output. When the air flow deviation signal 15 is negative, that is, when the air is excessive, air is output. It is set to output a signal for reducing the FDF inlet vane opening according to the flow rate deviation 15.

  The output value of the function generator 802 is set so that it does not fall below 100% unless the air flow deviation signal 15 is less than a certain negative value a. In order to prevent both the FDF inlet vane and the FDF rotational speed from operating and interfering with each other when the value is negative, the air flow rate becomes unstable. In such a case, the operation of the FDF inlet vane is fixed to control the FDF rotational speed. This is intended only to cause the air flow deviation signal 15 to be finally set to zero.

  The proportional gain multiplication unit 803 multiplies the FDF inlet vane control signal 16 sent from the function generator 802 by the proportional gain to create an FDF inlet vane opening command 12 and sends it to the opening command limiter 806. Here, the proportional gain determines the rate of change of the vane opening degree when the air flow rate deviation 15 is less than a, and normally operates at a constant value, but can be changed online.

  Thereafter, the opening command limiter 806 limits the opening command to the vane to the upper limit of 100%, creates a final FDF inlet vane opening command 18 and sends it to the inverter device 7. That is, if the FDF inlet vane opening command 12 created by multiplying by the proportional gain is less than 100%, no processing is performed, and if it is 100% or more, the opening command limiter 806 sends an opening command to the vane. Limiting to 100%, the final FDF vane opening command 18 is created.

  The control according to the present invention as described above performs proportional integral control of the air flow rate by FDF rotation speed control to ensure that the air flow rate is controlled to a specified value, and the FDF inlet vane is normally in a fully opened state and has excessive air. Only when it becomes significant, the opening is reduced and the air flow rate is quickly returned to the specified value.

  In the present invention, the inlet vane is basically fully opened, and the number of rotations of the FDF is reduced accordingly, thereby reducing the power consumption and improving the energy saving effect. However, the background behind the establishment of this control method is fundamental. Explain the idea. The operation patterns of thermal power plants can be broadly divided into normal load operations such as start, stop, load increase and load drop, and runback operations such as emergency load operations (for example, failure of plant components such as fans and pumps) , Operation that causes the load to drop rapidly to the maximum load that can be operated with only the remaining healthy equipment), FCB (when the power plant is disconnected from the system due to a system fault, etc., the plant is not stopped and the system is restored. To reduce the load to the load in the power plant so that the re-parallel operation can be performed quickly).

  Of these, the load change rate is about 5% / min at the maximum in normal load operation. On the other hand, in emergency load operation, the output is narrowed down at a load change rate of about 100% / min. In any case, the air flow rate needs to be increased or decreased in accordance with the load change speed of the power plant, but the operable speed of the inverter output is slower than the operable speed of the inlet vane. For this reason, in the conventional technology, the flow control operation end such as an inlet vane is always throttled to a certain degree to ensure that it can cope with a transient change in the air flow rate that the inverter output cannot follow in both the increasing and decreasing directions. ing.

  However, the operable speed in the increasing direction of the inverter output is usually sufficiently faster than 5% / min of the maximum speed considered in plant load operation. However, the decreasing direction is much slower than 100% / min of the maximum speed considered for plant load operation and more than several times slower than the operable speed of the inlet vane. Control by is essential. From the above, it can be said that the inlet vane need not always have a control allowance on the increased side, but can be operated on the decreased side when necessary, which is the basis of the idea of the present invention. .

  Next, the effect of the control according to the present invention will be described in comparison with the control according to the reference example while showing a typical operation pattern of the thermal power plant in FIG. However, the FDF rotational speed command of the reference example is programmed based on the air flow rate command, and is finally created by being limited to the operable speed of the inverter by the change rate limiter. In addition, the FDF inlet vane opening degree command of the reference example is generated by performing a proportional integral calculation from the air amount deviation signal calculated by the subtractor.

  In FIG. 2, the behavior of air flow control during load increase as an example of normal load operation, and the behavior of air flow control during FCB as an example of load operation in an emergency, the upper diagram shows a reference example, and the lower diagram shows the present invention. As shown. However, the horizontal axis represents time, and it is assumed that a normal load increasing operation is performed from t1 to t2, an FCB is generated at t3 after a constant load operation from t2 to t3. Also, during operation from t1 to t2 and from t2 to t3, the value of the air flow rate deviation signal 15 (SV-PV) is assumed to be greater than or equal to a shown in equations (1) and (2), and FCB is generated at t3. It is assumed that the value of the air flow deviation signal 15 (SV-PV) is less than a shown by the expressions (1) and (2).

  The air flow rate command basically operates in the same manner as the plant load command. The FDF inlet vane and the FDF rotational speed are controlled so as to follow this air flow rate command.

  In the reference example, during operation from t1 to t2 and from t2 to t3, the FDF inlet vane is always controlled so that the air flow rate deviation is zero, and the FDF inlet vane opening command is opened to secure the control allowance. It is kept at about 80%. At this time, the FDF rotation speed command is programmed based on the air flow rate command and moves in accordance with the air flow rate command. However, when FCB occurs at t3, the inverter cannot follow the rapid narrowing of the air flow rate command, so the FDF rotation speed command is created while being limited to the operable range by the change rate limiter. Therefore, since the air flow rate is excessively ensured temporarily, the FDF inlet vane is greatly narrowed to control the air flow rate.

  On the other hand, in the present invention shown in the figure below, the air amount deviation signal 15 (SV-PV) is greater than or equal to a shown in equation (2) during normal load increasing operation from t1 to t2, and therefore the FDF inlet from equation (2). The vane opening command is kept at 100%, that is, fully open. As described above, during normal load operation, since the range can be sufficiently followed only by the control by the FDF rotation speed control, the air flow rate deviation signal 15 is controlled to be 0 only by the FDF rotation speed control by the inverter. .

  Similarly, during the constant load operation from t2 to t3, the air amount deviation signal 15 (SV-PV) is equal to or greater than a indicated by the equation (2), and therefore the FDF inlet vane opening degree command 12 is 100 from the equation (2). %, And the air flow rate deviation signal 15 is controlled to be 0 only by the FDF rotation speed control.

  Here, the FDF inlet vane opening degree command and the FDF rotational speed command in the present invention and the reference example at the time of operation from t1 to t2 and from t2 to t3 are compared. Compared to the FDF inlet vane opening command and the FDF rotational speed command in the reference example shown by the dotted line in the lower diagram of FIG. 2, in the present invention, the FDF inlet vane opening command is set to 100% during normal load increase operation and constant load operation. Therefore, the FDF rotation speed command 13 can be kept low accordingly.

  When an FCB occurs at t3 after normal load operation, the FDF rotation speed command 13 is limited to the operable range by the change rate limiter 805 because it exceeds the followable range of the inverter due to a rapid load drop. At this time, since the value of the air flow rate deviation signal 15 (SV-PV) is less than a shown in the equation (1), the FDF inlet vane opening is based on the air flow rate deviation signal 15 (SV-PV) from the equation (1). The degree command 12 is narrowed down to 100% or less.

  After that, when the air flow rate deviation signal 15 (SV-PV) becomes a value equal to or larger than a shown in the equations (1) and (2) and is in a range that can be sufficiently followed by control only by the FDF rotation speed, the FDF inlet vane opening degree command 12 Is again kept at 100%.

  Similarly after t3, when comparing the FDF inlet vane opening command and the FDF rotational speed command in the present invention and the reference example, in the present invention, since the FDF inlet vane opening command starts to narrow down from 100%, the FDF rotational speed command is It is possible to keep it low.

  Thus, according to the present invention, the FDF rotation speed can be kept low in all the time regions shown in FIG. 2, and the FDF power consumption can be reduced correspondingly.

  As described above, in the present embodiment, the ventilator that sends fluid to the boiler, the flow rate adjusting operation end that adjusts the amount of fluid passing through the ventilator, the inverter that is the power of the motor of the ventilator, and the fluid A detection unit that detects a physical quantity; a subtraction unit that calculates a deviation between the physical quantity of the fluid and a physical quantity command calculated from the amount of fuel supplied to the boiler; and a control command to the inverter based on the physical quantity command. An inverter command calculation unit for calculating, and a flow rate adjustment operation end command calculation unit for creating a control command to the flow rate adjustment operation end based on the deviation, wherein the deviation is predetermined When the deviation is lower than the predetermined value, when the deviation is lower than the predetermined value, the FDF rotation speed is controlled by controlling the deviation at a higher rate with respect to the deviation. Energy-saving effect by the inverter can be suppressed clause can be exhibited to the maximum. In addition, when there is a need to rapidly reduce the flow rate that cannot be followed by FDF rotation speed control by an inverter, the flow rate adjustment operation end is appropriately narrowed down, so that the same flow rate control performance as the conventional technology can be maintained. is there.

It is a block diagram of the boiler and control apparatus of the thermal power plant in one Embodiment of this invention. It is a comparison figure of control in the present invention and a reference example.

Explanation of symbols

1 Furnace 2 Intruder (FDF)
3 FDF motor 4 FDF inlet vane 5 Chimney 6 Air flow detector 7 Inverter device 8 Boiler automatic controller 11 Air flow signal 12 FDF inlet vane opening command 13 FDF rotational speed command 14 Air flow command (AFD)
41 FDF inlet vane control drive

Claims (8)

A ventilator that sends fluid to the boiler;
A flow rate adjusting operation end for adjusting the amount of fluid passing through the ventilator;
An inverter serving as a power for the motor of the ventilator;
A detection unit for detecting a physical quantity of the fluid;
A subtractor that calculates a deviation between the physical quantity of the fluid and a physical quantity command calculated from the amount of fuel supplied to the boiler;
An inverter command calculation unit that calculates a control command to the inverter based on the physical quantity command;
A flow adjustment operation end command calculation unit for creating a control command to the flow adjustment operation end based on the deviation;
When the deviation is higher than a predetermined value, the inverter is controlled by the inverter,
When the deviation is lower than a predetermined value, the inverter and the flow rate adjusting operation end
A boiler automatic control device characterized by controlling a recording fan . 2. The control according to claim 1, wherein when the deviation is higher than a predetermined value and when the deviation is lower than the predetermined value, the deviation is lower than the predetermined value at a higher rate of change with respect to the deviation. A boiler automatic control device characterized by: 2. The boiler automatic control device according to claim 1, wherein the control command to the inverter is created by a proportional-integral calculation of the deviation. 2. The boiler automatic control device according to claim 1, wherein the control command to the flow rate adjusting operation end is generated by multiplying a function generated by the flow rate adjusting operation end command calculating unit by a proportional gain. 2. The boiler automatic control device according to claim 1, further comprising a change rate limiter for limiting a change rate of the inverter. 2. The boiler automatic control device according to claim 1, wherein when the deviation is larger than the set value, the flow rate adjusting operation end command calculation unit fully opens the flow rate adjusting operation end. According to claim 1 or claim 6, wherein the set value boiler automatic control system, characterized in that provided for in a negative value. With a boiler,
A ventilator that sends combustion gas or air to the boiler;
A flow rate adjusting operation end for adjusting the amount of combustion gas or air passing through the ventilator;
A motor for driving the ventilator;
An inverter serving as the power of the motor;
A detection unit for detecting a physical quantity of the combustion gas or air;
A subtractor for calculating a deviation between the physical quantity of the combustion gas or air and the physical quantity command calculated from the amount of fuel supplied to the boiler;
An inverter command calculation unit that calculates a control command to the inverter based on the physical quantity command;
A flow adjustment operation end command calculation unit for creating a control command to the flow adjustment operation end based on the deviation;
When the deviation is higher than a predetermined value, the inverter is controlled by the inverter,
When the deviation is lower than a predetermined value, the ventilator is controlled by the inverter and the flow rate adjusting operation end.

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