JP2015175570A - boiler system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a boiler system that prevents hunting from occurring.SOLUTION: A boiler system includes: a plurality of boilers 20 that enable combustion by changing a combustion rate; a steam header 6 in which steam generated by the plurality of boilers gathers; and a control section 4 for controlling the combustion states of the plurality of boilers 20 in accordance with required load. The control section 4 includes: a steam amount calculation section 41 for calculating necessary steam amount in the PID control method so as to maintain a steam pressure value (header pressure value) within the steam header 6 to a target steam pressure value relative to fluctuation of steam consumption amount; an output control section 42 for controlling the combustion states of the plurality of boilers 20 so as to generate the necessary steam amount calculated by the steam amount calculation section 41; a hunting detection section 43 for detecting fluctuation of the header pressure value that may cause hunting (pseudo hunting); and a correction section 44 for making correction to increase a proportional band in the PID control method when the pseudo hunting is detected by the hunting detection section 43.

Description

  The present invention relates to a boiler system that controls a combustion amount of a boiler according to steam consumption by a P (proportional control), PI (proportional integral control) or PID (proportional integral differential control) algorithm.

  DESCRIPTION OF RELATED ART Conventionally, the boiler system provided with the boiler and the control part which controls the combustion amount of a boiler according to the steam consumption (required load) of a steam using facility is known. In such a boiler system, the steam consumption value of the steam header is set so that the steam pressure value inside the steam header (hereinafter also referred to as “header pressure value”) becomes a constant target steam pressure value regardless of the fluctuation of the steam consumption. The combustion amount of the boiler is controlled according to the fluctuation. Conventionally, in order to keep the steam pressure value inside the steam header at the target steam pressure value against fluctuations in steam consumption, the steam amount (hereinafter also referred to as “necessary steam amount”) to be generated in the boiler is controlled by the PID algorithm. There has been proposed a boiler system using such a technique (see, for example, Patent Documents 1 and 2).

JP 2002-73105 A Japanese Patent No. 3805611

By the way, in the control of the steam amount by the PID algorithm, from the viewpoint of emphasizing pressure stability, a control pressure upper limit that is not reached if the header pressure value is normal control is provided in advance, for example, steam consumption of steam using equipment When the (required load) decreases sharply, when the header pressure value exceeds the upper limit of control pressure, unit control may be performed to stop all boilers (hereinafter also referred to as “all can stop”). .
When all cans are stopped, the header pressure value drops rapidly, and an excessive amount of steam calculated by PID calculation is secured. For this reason, when a boiler starts combustion and output steam amount increases, a header pressure value will change from a fall to a raise after that. The necessary steam amount continues to decrease from the time when the header pressure value starts to increase, but at that time, the necessary steam amount is secured excessively. Since the output steam amount does not catch up with the required steam amount, the output steam amount continues to increase and the header pressure value continues to increase.
In this case, the increase in the header pressure value cannot be suppressed, and all the cans are stopped again by exceeding the upper limit of the control pressure, so that the header pressure value may drop rapidly.
When this repetition occurs, a so-called hunting phenomenon in which the header pressure value fluctuates up and down without converging on the target steam pressure value occurs and continues.
Such a hunting phenomenon can occur even when the header steam pressure value is below the lower limit pressure that cannot be reached under normal control due to a significant shortage of output steam.

  In the present invention, when the header pressure value detects a pressure fluctuation that may cause hunting, the header pressure value is quickly converged to the target steam pressure value by avoiding the stoppage of all cans and occurrence of hunting. The purpose is to provide a boiler system.

  The present invention comprises a plurality of boilers capable of burning at different combustion rates, supplying steam to the load equipment, a steam header in which steam generated in the boiler group gathers, and a request from the load equipment A control unit that controls the combustion state of the plurality of boilers according to a load, and the control unit maintains a steam pressure value inside the steam header at a target steam pressure value with respect to fluctuations in steam consumption. As described above, the steam amount calculation unit for calculating the required steam amount by the PI control method or the PID control method, and the combustion state of the plurality of boilers are controlled so as to generate the necessary steam amount calculated by the steam amount calculation unit. An output control unit that performs, a hunting detection unit that detects fluctuations in the steam pressure value inside the steam header that may cause hunting as pseudo hunting, and the hunting detection unit, Serial when detecting pseudo hunting, a correction unit that performs correction to increase the proportional band in the PI control scheme or PID control method relates to a boiler system comprising a.

  After performing the correction to increase the proportional band, the correction unit, when the hunting detection unit does not detect the pseudo hunting for a predetermined time set in advance, in the PI control method or the PID control method Correction that returns the proportional band to the value before correction can be performed.

  Further, the hunting detection unit includes a control pressure upper limit value and a target steam pressure value that are set in advance as threshold values at which the steam pressure of the plurality of boilers is stopped by the control unit. During the first time, a fluctuation that exceeds a preset second control pressure upper limit value or becomes equal to or greater than the second control pressure upper limit value is detected as pseudo hunting during the first time. be able to.

  Further, the hunting detection unit is configured such that the steam pressure value inside the steam header falls below a second control zone lower limit value set in advance so that an absolute value of a deviation from the control zone lower limit value is equal to or less than the first threshold value. Alternatively, it is possible to detect, as pseudo hunting, fluctuations that occur more than the second number of times during the second time when the number of times becomes equal to or less than the second control zone lower limit value.

  Further, the hunting detection unit is a pressure having a preset pressure drop width when the steam pressure value inside the steam header drops from a value exceeding the target steam pressure value to a value lower than the target steam pressure value. A fluctuation that occurs more than the third number of times during the third time when the number of times the pressure drop value exceeds or exceeds the pressure drop value can be detected as pseudo hunting.

  The control unit includes a storage unit that stores a plurality of parameters related to a proportional band in the PI control method or the PID control method, and the steam amount calculation unit is a proportionality set by one parameter among the plurality of parameters. The necessary steam amount is calculated by a PI control method or a PID control method based on a band, and the correction unit can correct the proportional band using one parameter among the plurality of parameters.

  In addition, when the control unit detects pseudo hunting by the hunting detection unit, the control unit corrects information related to the pseudo hunting (for example, the date and time when the pseudo hunting is detected, the header pressure value, the proportional band when the pseudo hunting is detected, and the correction. A change information recording unit for recording the date and time, the proportional band at the time of correction, and the date and time returned to the proportional band before correction).

  According to the present invention, in a boiler system including a unit control means for controlling the combustion amount of a boiler to be controlled so that the steam pressure value inside the steam header matches the target pressure value, all can stop or cause of hunting When the fluctuation of the steam pressure value inside the steam header that may become a false hunting is detected as a pseudo hunting, the header pressure value is quickly set to the target steam pressure value by avoiding the occurrence of all-can stop or hunting in advance. It is possible to provide a boiler system that converges.

It is a schematic structure figure of boiler system 1 concerning a 1st embodiment. It is a figure which shows the outline of a boiler group. It is a functional block diagram which shows the structure of a control part. It is a flowchart which shows the flow of the feedback control of the boiler system 1 which concerns on 1st Embodiment. It is a figure which shows the time transition of the header pressure value at the time of implementing the pressure control by the PID algorithm which concerns on 1st Embodiment using the boiler system 1 shown in FIG. 1 as a model. It is a figure which shows the time transition of the header pressure value at the time of implementing the pressure control by the PID algorithm which concerns on 2nd Embodiment using the boiler system 1 shown in FIG. 1 as a model. It is a figure which shows the time transition of the header pressure value at the time of implementing the pressure control by the PID algorithm which concerns on 3rd Embodiment using the boiler system 1 shown in FIG. 1 as a model.

(First embodiment)
Hereinafter, a boiler system according to a first embodiment of the present invention will be described with reference to the drawings.
First, the overall configuration of the boiler system 1 of the present invention will be described with reference to FIG. The boiler system 1 includes a boiler group 2 including a plurality of (five) boilers 20, a steam header 6 that collects steam generated in the plurality of boilers 20, and steam that measures the pressure inside the steam header 6. A pressure sensor 7 and a number control device 3 having a controller 4 that controls the combustion state of the boiler group 2 are provided.

The boiler group 2 generates steam to be supplied to the steam use facility 18.
The steam header 6 is connected to a plurality of boilers 20 constituting the boiler group 2 via a steam pipe 11. The downstream side of the steam header 6 is connected to the steam use facility 18 via the steam pipe 12.
The steam header 6 collects and stores the steam generated in the boiler group 2. The steam header 6 adjusts the mutual pressure difference and pressure fluctuation of the one or more boilers 20 to be combusted, and supplies steam whose pressure is adjusted to be constant to the steam using facility 18.

  The vapor pressure sensor 7 is electrically connected to the number control device 3 via the signal line 13. The vapor pressure sensor 7 measures the vapor pressure (header pressure) of the vapor header 6 and transmits a vapor pressure signal as a measurement result to the unit control device 3 via the signal line 13.

  The number control device 3 is electrically connected to the plurality of boilers 20 through the signal line 16. The number control device 3 controls the combustion state of each boiler 20 based on the steam pressure inside the steam header 6 measured by the steam pressure sensor 7. Details of the number control device 3 will be described later.

The above boiler system 1 can supply the steam generated in the boiler group 2 to the steam using equipment 18 via the steam header 6.
The load required in the boiler system 1 (required load) is the amount of steam consumed in the steam using facility 18. The number control device 3 calculates the required steam amount based on the fluctuation of the steam pressure inside the steam header 6 generated in response to the fluctuation of the steam consumption, and determines the combustion state of each boiler 20 constituting the boiler group 2. Control.

  Specifically, if the required load (steam consumption) increases due to an increase in demand for the steam use facility 18 and the amount of steam supplied to the steam header 6 (output steam amount described later) is insufficient, the steam header 6 The internal steam pressure will drop. On the other hand, if the demand load (steam consumption) decreases due to a decrease in demand for the steam use facility 18 and the amount of steam supplied to the steam header 6 becomes excessive, the steam pressure inside the steam header 6 increases. Become. Therefore, the boiler system 1 can monitor the fluctuation of the required load based on the fluctuation of the steam pressure inside the steam header 6 measured by the steam pressure sensor 7. Then, the boiler system 1 calculates a necessary steam amount that is a steam amount required according to the steam consumption (required load) of the steam using facility 18 based on the steam pressure inside the steam header 6. Details of the control method will be described later.

Here, the several boiler 20 which comprises the boiler system 1 is demonstrated. FIG. 2 is a diagram showing an outline of the boiler group 2.
The boiler 20 is composed of a proportional control boiler capable of burning by continuously changing the combustion rate.
The proportional control boiler is a boiler whose combustion rate can be continuously controlled at least in the range from the minimum combustion state S1 (for example, the combustion state of 20% of the combustion rate) to the maximum combustion state S2. The proportional control boiler adjusts the combustion rate, for example, by controlling the opening of a valve that supplies fuel to the burner or a valve that supplies combustion air.

  Also, the continuous control of the combustion rate means that the calculation or signal in the local control unit 22 described later is a digital method and is handled in stages (for example, the output (combustion rate) of the boiler 20 is in increments of 1%). Even when the output is controlled).

The change of the combustion state between the combustion stop state S0 and the minimum combustion state S1 of the boiler 20 is controlled by turning on / off the combustion of the boiler 20 (burner). In the range from the minimum combustion state S1 to the maximum combustion state S2, the combustion rate can be continuously controlled.
More specifically, a unit steam amount U, which is a unit of variable steam amount, is set for each of the plurality of boilers 20. Thus, the boiler 20 can change the steam amount in units of the unit steam amount U in the range from the minimum combustion state S1 to the maximum combustion state S2.

The unit steam amount U can be appropriately set according to the steam amount (maximum steam amount) in the maximum combustion state S2 of the boiler 20, but from the viewpoint of improving the followability of the output steam amount to the necessary steam amount in the boiler system 1. It is preferably set to 0.1% to 20% of the maximum steam amount of 20, and more preferably set to 1% to 10%.
Note that the output steam amount indicates the steam amount output by the boiler group 2, and this output steam amount is represented by the total value of the steam amounts output from each of the plurality of boilers 20.

  Moreover, the priority order is set to each of the plurality of boilers 20. The priority order is used to select the boiler 20 that performs a combustion instruction or a combustion stop instruction. The priority order can be set, for example, using an integer value so that the lower the numerical value, the higher the priority order. As shown in FIG. 2, when the priorities of “1” to “5” are assigned to the first to fifth units of the boiler 20, the first unit has the highest priority, and the fifth unit has the highest priority. Lowest. In the normal case, this priority order is changed at predetermined time intervals (for example, 24 hour intervals) under the control of the control unit 4 described later.

The above boiler 20 is provided with the boiler main body 21 in which combustion is performed, and the local control part 22 which controls the combustion state of the boiler 20, as shown in FIG.
The local control unit 22 changes the combustion state of the boiler 20 according to the required load. Specifically, the local control unit 22 controls the combustion state of the boiler 20 based on the number control signal transmitted from the number control device 3 via the signal line 16.
Further, the local control unit 22 transmits a signal used in the number control device 3 to the number control device 3 via the signal line 16. Examples of the signal used in the number control device 3 include an actual combustion state of the boiler 20 and other data.

Next, details of the number control device 3 will be described.
Based on the steam pressure signal from the steam pressure sensor 7, the number control device 3 calculates the required combustion amount of the boiler group 2 according to the required load and the combustion state of each boiler 20 corresponding to the required combustion amount, The number control signal is transmitted to the boiler 20 (local control unit 22). As shown in FIG. 1, the number control device 3 includes a storage unit 5 and a control unit 4.

  The storage unit 5 includes the contents of instructions given to each boiler 20 under the control of the control unit 4, information such as the combustion state received from each boiler 20, information on the priority order setting of the plurality of boilers 20, and priority. Information on settings related to the change (rotation) of the order is stored. As will be described later, at least two or more parameters related to the proportional band in the PI control method or the PID control method can be stored in the storage unit 5. Also, as will be described later, information related to pseudo hunting detected by the hunting detection unit, such as the date and time when pseudo hunting was detected, the status of the pseudo hunting, the value of the proportional band when pseudo hunting was detected, the corrected date and time, and correction Information such as the value of the proportional band of time and the date and time when the proportional band before correction is restored can be stored.

  The control unit 4 gives various instructions to each boiler 20 via the signal line 16 and receives various data from each boiler 20 to control the combustion state and priority order of the five boilers 20. . When each boiler 20 receives a signal for changing the combustion state from the number control device 3, it controls the boiler 20 according to the instruction.

(Configuration of control unit 4)
Next, a detailed configuration of the control unit 4 will be described. As shown in FIG. 3, the control unit 4 includes a steam amount calculation unit 41, an output control unit 42, a hunting detection unit 43, a correction unit 44, a fluctuation information recording unit 45, a history information analysis unit 46, It is comprised including.

  The steam amount calculation unit 41 calculates the required steam amount based on the target steam pressure value SV set in advance, the steam pressure value PV inside the steam header 6 measured by the steam pressure sensor 7, and the like. Specifically, the steam amount calculation unit 41 sets the necessary steam amount so that the steam pressure value PV inside the steam header 6 measured by the steam pressure sensor 7 becomes a preset target steam pressure value SV. For example, it is calculated by a speed type PID algorithm.

The steam amount calculation unit 41 calculates the current required steam amount MVn generated from the plurality of boilers 20 based on the following speed type arithmetic expression (1).

MV _n = MV _n-1 + ΔMV _n (1)
Here, when Δt is a control period and n is a positive integer value,
MV _n is the current required steam amount generated from the plurality of boilers 20 in the control cycle n (starting point t0 + n * Δt),
MV _n-1 is the previous required steam amount in the control cycle (n-1),
ΔMV _n represents the required amount of steam change for each control cycle.

The speed type calculation is a method of calculating only the necessary steam amount change ΔMV _{n for} each control cycle and adding the previous required steam amount MV _n−1 to this to calculate the present required steam amount MV _n .
On the other hand, the PID control algorithm that directly calculates the required steam amount MV _n this time for each control cycle is referred to as position calculation.

The required steam amount change ΔMV _{n for} each control cycle is calculated based on the following equations (2) to (6).

ΔMV _n = ΔP _n + ΔI _n + ΔD _n (2)
Here, ΔP _n is the P control output (change).
[Delta] I _n the I control output (change amount),
ΔD _n represents the D control output (change).

_{* ΔP n = K P (e} n -e n-1) ··· (3)
Where K _P is the proportional gain,
e _n is a difference (current deviation amount) between the current target steam pressure value SV _n and the current steam pressure value PV _n inside the steam header 6 measured by the steam pressure sensor 7, as shown in the equation (4). ).

e _n = SV _n −PV _n (4)

_{ΔI n = K P * (Δt} / T I) * e n ··· (5)
T _I represents the integration time.

_{ΔD n = K P * (T} D / Δt) * (e n -2e n-1 + e n-2)
... (6)
Here, _{T D} represents the derivative time.

The steam amount calculation unit 41 calculates a necessary steam amount change ΔMV _n for each control cycle by summing the outputs (changes) calculated by the equations (3), (5), and (6).
The steam amount calculation unit 41 calculates the current required steam amount MV _n by adding ΔMV _n to the previous required steam amount MV _n−1 as shown in Equation (1).
Note that the steam amount calculation unit 41 may apply a PID control algorithm based on position type calculation when calculating the required steam amount.

(Control pressure upper limit value)
By the way, when controlling the steam amount by the PI algorithm or the PID algorithm, the control unit 4 previously sets a control pressure upper limit that cannot be reached if the header pressure value is normal control from the viewpoint of emphasizing pressure stability. For example, if the steam consumption (required load) of the steam-using equipment decreases rapidly, and the header pressure value exceeds the limit condition pressure, all boilers are stopped (hereinafter also referred to as “all can stop”). To control the number of units.

When all cans are stopped, the header pressure value drops rapidly, and an excessive amount of steam calculated by PID calculation is secured. For this reason, when a boiler starts combustion and output steam amount increases, a header pressure value will change from a fall to a raise after that. The necessary steam amount continues to decrease from the time when the header pressure value starts to increase, but at that time, the necessary steam amount is secured excessively. And since the amount of output steam has not caught up with the required amount of steam, the amount of output steam may continue to increase and the header pressure value may continue to increase.
As a result, it is highly possible that the increase in the header pressure value cannot be suppressed, and that all the units are on standby again by exceeding the limit condition pressure, and that the header pressure value rapidly decreases.
When such an event occurs, a so-called hunting phenomenon in which the header pressure value fluctuates up and down without converging to the target steam pressure value occurs and continues.

(Control pressure upper limit 2)
For this reason, the second control pressure upper limit value is set in advance between the control pressure upper limit value and the target steam pressure value that are set in advance as a threshold value at which the header 4 is stopped by the control unit 4 for all the boilers 20. To do.
Control pressure upper limit value> Second control pressure upper limit value> Target steam pressure value

In the first embodiment, although the header pressure value does not exceed the control pressure upper limit value, the fluctuation that becomes equal to or greater than the second control pressure upper limit value is performed a predetermined number of times (for example, 4 times) within a predetermined time (for example, 60 seconds). ) If the above is repeated, it is considered that the header pressure value fluctuates, which may cause hunting (hereinafter referred to as “pseudo hunting”, the predetermined time as “first time”, and the predetermined number of times as “first” 1 times)).
By detecting the pseudo hunting, it is possible to prevent the header pressure value from exceeding the control pressure upper limit value and to stop all cans and cause hunting.

(Proportional band)
By the way, when the control part 4 controls the amount of steam by the PID algorithm, it is necessary to appropriately set a proportional band or a proportional gain in order to improve pressure stability.

Here, the relationship between the proportional band Pb and the proportional gain Kp will be briefly described.
For example, the relationship between the proportional band Pb and the proportional gain Kp can be expressed by the following equation.

Proportional gain Kp = Maximum steam volume / (Proportional band Pb x Full scale pressure)
... (7)
Note that the value of the proportional gain is not a fixed value and can be adjusted based on the combustion rate of the boiler 20, for example, so that the proportional gain becomes smaller as the combustion rate of the boiler 20 is lower.

  Thus, when the proportional band Pb is set large, the proportional gain becomes small, and a small operation amount is calculated with respect to the deviation between the target steam pressure value and the header pressure value. When the proportional band is set small, the proportional gain becomes small. A large manipulated variable is calculated with respect to the deviation between the target steam pressure value and the header pressure value. (See Formula (3), Formula (5), Formula (6), Formulas (8) to (10), etc.).)

One cause of the occurrence of pseudo hunting is that the manipulated variable is excessively calculated with respect to the deviation between the target steam pressure value and the header pressure value. As a result, the pressure fluctuations suddenly move up and down, resulting in pseudo hunting (or hunting). ) May occur.
For this reason, when the hunting detection unit 43 detects the pseudo hunting, the correction unit 44 corrects the proportional band so as to increase as described later. By correcting the proportional band largely, as a result, the proportional gain is changed to be small, and control is performed so that the operation amount is not excessively calculated. By doing so, the rapid vertical fluctuation of the pressure fluctuation is suppressed, the header pressure value is quickly converged to the target steam pressure value in the pseudo hunting stage, and the occurrence of all can stop or hunting is avoided.

  The output control unit 42 controls the combustion state (combustion amount) of the boiler 20 based on the current required steam amount calculated by the steam amount calculating unit 41. The output control unit 42 controls the combustion state of each boiler 20 so that steam corresponding to the required steam amount is generated from the boiler group 2.

  The output control unit 42 sets the number of boilers 20 to be burned based on the required steam amount calculated according to the steam consumption amount in the steam amount calculation unit 41. The output control unit 42 sets the boilers 20 that start or stop combustion in accordance with the priority order described in the storage unit 5, and sends a unit control signal (operation start or operation) to the local control unit 22 of the boilers 20. Stop) is output. Thereby, by controlling the combustion state of each boiler 20 so that steam corresponding to the required steam amount is generated from the boiler group 2, a steam amount corresponding to the required steam amount (hereinafter also referred to as “output steam amount”) is obtained. Supplied to the steam header 6.

In the hunting detection unit 43, the number of times that the steam pressure value inside the steam header 6 exceeds the second control pressure upper limit value or becomes equal to or higher than the second control pressure upper limit value is during the first time (for example, 60 seconds). In addition, it is detected whether or not the first occurrence (for example, 4 times) or more has occurred.
In addition, about 1st time and 1st frequency | count, it can set suitably according to the characteristic of a boiler system. For example, when the first number of times is set to “1”, the hunting detector 43 determines that the steam pressure value inside the steam header 6 exceeds the second control pressure upper limit value or is equal to or greater than the second control pressure upper limit value. It is detected whether or not it has occurred.

  The correction unit 44 causes the number of times that the steam pressure value inside the steam header 6 exceeds the second control pressure upper limit value or exceeds the second control pressure upper limit value by the hunting detection unit 43 for the first time (for example, When it is detected that the occurrence has occurred more than the first number of times (for example, 4 times) during 60 seconds), correction is performed to increase the proportional band in the PI control method or PID control method.

  In order to perform this correction, at least two or more parameters related to the proportional band in the PI control method or the PID control method are stored in the storage unit 5 in advance.

  Of the at least two or more parameters, one parameter is used as a normal band parameter as a proportional band value in the PI control method or PID control method. That is, the steam amount calculation unit 41 calculates the required steam amount by the PI control method or the PID control method based on the proportional band set by the normal parameter among the plurality of parameters, and is calculated by the output control unit 42. The required amount of steam is supplied to the steam header.

  Of the at least two or more parameters, parameters other than normal parameters are manipulated with respect to the deviation between the target steam pressure value and the header pressure value when pseudo hunting is detected as a correction parameter. Is used as the value of the proportional band in the PI control method or the PID control method so that it is not excessively calculated. For this reason, it is assumed that the value of the proportional band in the parameter at the time of correction is larger than the value of the proportional band set by the parameter at the normal time.

For example, when the value of the proportional band in the normal parameter is 5%, for example, a value of 7% to 8% may be adopted as the parameter at the time of correction.
A plurality of parameters may be provided as correction parameters. In this case, the correction parameter is identified by giving a correction number, for example, and a value of 7% as a value of the proportional band in the correction parameter of correction number 1 is set to the correction number of 2. The parameter can be a parameter in which the value of the proportional band is increased by a predetermined ratio so that a value of 9% is set as the value of the proportional band in the parameter. For the normal parameters, the parameter identification number may be identified as the correction number 0 for convenience.

  When the hunting detection unit 43 detects pseudo hunting, the correction unit 44 performs correction to temporarily increase the proportional band in the PI control method or the PID control method by replacing the normal parameter with the correction parameter. be able to.

  By doing so, the steam amount calculation unit 41 calculates the necessary steam amount by the PI control method or the PID control method based on the temporarily increased proportional band set by the parameter at the time of correction, and the output control unit 42 The required steam amount calculated based on the PI control method or the PID control method based on the proportional band set by the correction parameter is supplied to the steam header. As a result, it is possible not to calculate an excessive amount of operation with respect to the deviation between the target steam pressure value and the header pressure value. It is possible to converge.

  After the correction unit 44 performs correction to temporarily increase the proportional band, the hunting detection unit 43 determines whether or not pseudo hunting occurs during a predetermined time (for example, 2 to 3 minutes). To monitor. When the hunting detection unit 43 does not detect pseudo hunting for a predetermined time (for example, 2 to 3 minutes) set in advance, it is determined that the pseudo hunting tends to converge, and the correction unit 44 By replacing the correction parameter with the normal parameter, the proportional band in the PI control method or the PID control method can be returned to the original value.

  By doing so, the steam amount calculation unit 41 again calculates the required steam amount based on the PI control method or the PID control method using the proportional band set by the normal parameters, and the output control unit 42 The required steam amount calculated based on the PI control method or the PID control method using the proportional band set by the normal parameters is supplied to the steam header.

  When a plurality of parameters at the time of correction are provided, the correction unit 44 performs a correction to increase the proportional band by the parameter at the time of correction (correction number 1), and then uses the proportional band set by the parameter. When the required steam amount calculated by the steam amount calculation unit 41 based on the control method or the PID control method is supplied to the steam header by the output control unit 42, when the pseudo hunting is still detected by the hunting detection unit 43, The correction unit 44 can perform correction to further increase the proportional band in the PI control method or the PID control method by further replacing the correction parameter (correction number 1) with the correction parameter (correction number 2). .

  By doing so, the output control unit 42 is calculated by the steam amount calculation unit 41 based on the PI control method or the PID control method that uses a temporarily larger proportional band set by the correction parameter (correction number 2). The required amount of steam is supplied to the steam header 6. As a result, it is possible not to calculate an excessive operation amount with respect to the deviation between the target steam pressure value and the header pressure value, and it is possible to converge pressure fluctuations gently.

When the hunting detection unit does not detect pseudo hunting for a predetermined time (for example, 2 minutes), the correction unit 44 changes the correction parameter (correction number 2) to the correction parameter (correction). By replacing with No. 1), the proportional band in the PI control method or PID control method is returned to the value set by the parameter at the time of correction (correction number 1), and then the proportional band by the parameter at the time of correction (correction number 1) In a state in which the correction for increasing is performed, after confirming that the hunting detection unit does not detect pseudo hunting for a predetermined time (for example, 2 minutes), the correction unit 44 It is preferable that the proportional band in the PI control method or the PID control method is returned to the original value by replacing the parameter in FIG.
If the hunting detection unit does not detect pseudo hunting for a predetermined time (for example, 2 minutes), the correction unit 44 sets the correction parameter (correction number 2) as the normal parameter. It can also be configured to return to (correction number 0).

When supplying the required steam amount calculated by the steam amount calculation unit 41 based on the PI control method or PID control method using the proportional band set by the normal parameters to the steam header by the output control unit 42, Pseudo hunting is detected every time, but after performing correction to increase the proportional band, the steam amount calculation unit 41 based on the PI control method or PID control method using the proportional band set by the parameter at the time of correction When the calculated required steam amount is supplied to the steam header 6 by the output control unit 42, pseudo hunting may not be detected.
In such a case, there may be a choice that it is better to increase the normal proportional band. For example, when the number of occurrences exceeds a predetermined threshold based on the number of occurrences of pseudo hunting when using normal parameters, the correction unit 44 does not return from the correction parameters to the normal parameters. Also good.

  Even in such a case, it is assumed that the correction is merely a precautionary measure for hunting and a temporary correction for temporarily preventing the occurrence of hunting, so that the correction parameter is always returned to the normal parameter. It may be.

  In either case, as will be described later, it is preferable that the administrator can always check the correction status based on the analysis information output by the history information analysis unit 46.

The fluctuation information recording unit 45 stores information on pseudo hunting detected by the hunting detection unit 43, for example, the date and time when the pseudo hunting is detected, the content of the pseudo hunting, and the value of the proportional band when the pseudo hunting is detected as history information. Store in part 5.
Similarly, the fluctuation information recording unit 45 records the time information such as date, time, minute, second, etc., in which the correction unit 44 has performed the correction for increasing the proportional band, and the value of the proportional band before correction and the value of the proportional band after correction. The information is stored in the storage unit 5 as information. A correction number may be stored instead of the value of the proportional band before correction and the value of the proportional band after correction.

  In addition, the fluctuation information recording unit 45 uses the correction unit 44 to replace the parameter at the time of correction with the parameter before correction (for example, the time information when the parameter is corrected and the proportional band before the replacement). The value of the proportional band after the replacement is stored as history information in the storage unit 5. The parameter before replacement is corrected instead of the value of the proportional band after the replacement. The number and the correction number of the parameter after replacement may be stored.

  The history information analysis unit 46 generates history information related to pressure value variation information stored by the variation information recording unit 45, the number of occurrences of pseudo hunting that occurred during a predetermined period designated by the administrator or set in advance. Information such as the situation, alarm information (for example, when the occurrence of pseudo hunting is abnormal during the period), and the like are output. The analysis information can be output to a display unit (not shown) or a terminal used by the administrator.

  In addition, the history information analysis unit 46 outputs the history information regarding the pressure value variation information stored by the variation information recording unit 45 to a display unit (not shown) or a terminal used by the administrator each time. Also good.

  By doing so, the administrator uses the output information of the history information analysis unit 46 to optimize the PID parameter as a material for determining whether or not the PID parameter (proportional band value) for the required load is appropriate. Is possible.

(flowchart)
Next, the operation of the boiler system 1 will be described with reference to FIG. FIG. 4 is a flowchart showing a control flow of the boiler system 1.

The control flow of the boiler system 1 is as follows.
In step ST1, the control unit 4 (correction unit 44) performs initial setting so that the normal parameter (correction number 0) is used as the value of the proportional band.
At this time, for example, flag data using a register, a bit memory or the like is prepared, and the control unit 4 (correction unit 44) sets the correction number 0 to the flag data.

  In step ST <b> 2, the steam amount calculation unit 41 performs PI control method or PID control based on the target pressure value, the steam pressure value inside the steam header 6 measured by the steam pressure sensor 7, and the proportional band of the currently set parameters. The required steam amount is calculated by the method, and the output control unit 42 controls the combustion state of the boiler 20 so as to generate the required steam amount calculated by the steam amount calculating unit 41.

  In step ST3, the hunting detection unit 43 determines whether or not pseudo hunting has occurred (that is, the steam pressure value inside the steam header 6 exceeds the second control pressure upper limit value or exceeds the second control pressure upper limit value). Whether or not the number of occurrences has occurred for the first time (for example, 4 times) or more during the first time (for example, 60 seconds) is detected. When the occurrence of pseudo hunting is detected (Yes), the process proceeds to step ST4. If the occurrence of pseudo hunting is not detected (No), the process returns to step ST2.

In step ST4, the correction unit 44 determines whether or not the correction parameter corresponding to the correction number has reached the maximum value. When the maximum value has been reached (Yes), the process proceeds to step ST8. If the maximum value has not been reached, the process proceeds to step ST5.
When the maximum value has been reached (Yes), the fluctuation information recording unit 45 stores history information indicating that the correction parameter has reached the maximum value, and alarm information (the correction parameter has reached the maximum value). Alarm) indicating that it is in a state. As alarm information, it is desirable to display an alarm or a display that can be seen at a glance on the display screen.

    In step ST5, the correction unit 44 calculates a new correction number by adding 1 to the correction number set in the flag data.

  In step ST6, the correction unit 44 temporarily replaces the proportional band in the PI control method or the PID control method by replacing the current parameter with a new correction parameter (new correction number) corresponding to the new correction number. Make the correction to be larger. By doing so, the steam amount calculation unit 41 can perform the PI control method or PID based on the target pressure value, the steam pressure value inside the steam header 6 measured by the steam pressure sensor 7, and the proportional band of the new correction parameter. The necessary steam amount is calculated by the control method, and the output control unit 42 controls the combustion state of the boiler 20 so as to generate the necessary steam amount calculated by the steam amount calculating unit 41.

  In step ST7, the fluctuation information recording unit 45 includes information on the pseudo hunting detected by the hunting detection unit 43 and time information (time minute second) when the correction unit 44 performs correction to temporarily increase the proportional band. , And the value of the proportional band before correction and the value of the proportional band after correction are stored in the storage unit 5 as history information. A correction number may be stored instead of the value of the proportional band before correction and the value of the proportional band after correction.

In step ST8, the hunting detector 43 detects whether or not pseudo hunting occurs during a predetermined time (for example, 2 minutes).
When the occurrence of pseudo hunting is detected (Yes), the process proceeds to step ST4. If the occurrence of pseudo hunting is not detected (No), the process proceeds to step ST9.

  In step ST9, the correction unit 44 calculates a correction number before correction by subtracting 1 from the correction number set in the flag data.

  In step ST10, the correction unit 44 replaces the current parameter with a correction parameter (correction number before correction) corresponding to the correction number before correction, thereby correcting the proportional band in the PI control method or PID control method before correction. Perform correction to return to.

In step ST11, the fluctuation information recording unit 45 includes the time information when performing the correction to return to the proportional band before correction, the value of the proportional band before returning to the value of the proportional band before correction, and the proportional band before correction. The value is stored in the storage unit 5 as history information. A correction number may be stored instead of the value of the proportional band before correction and the value of the proportional band after correction.
Thereafter, the process proceeds to step ST2.

  In step ST12, the correction unit 44 determines whether or not the value set in the flag data is zero. If the value set in the flag data is 0 (Yes), the process proceeds to step ST2. If the value set in the flag data is not 0 (No), the process proceeds to step ST8.

(Convergence of pseudo hunting)
Next, referring to FIG. 5, when the pressure control is performed using the PID algorithm according to the first embodiment, the header pressure value, the necessary steam amount, and the actual output after the occurrence of the pseudo hunting and the pseudo hunting occurs. The temporal change in the amount of steam will be described.
FIG. 5 shows a temporal transition of the header pressure value when the pressure control by the PID algorithm according to the first embodiment is performed.

FIG. 5 includes a boiler group including five boilers 20 as shown in FIG. 1. The maximum amount of steam generated (maximum output) of each boiler 20 is 7000 kg / h, the maximum pressure is 2 MPa (megapascal), and the target The boiler system 1 has a steam pressure value of 1.6 MPa, a limit upper limit pressure of 1.7 MPa, a second control pressure upper limit value of 1.65 MPa, and a control zone lower limit of 1.5 MPa.
Moreover, the normal proportional band is set to 5% (= 0.1 MPa = 2 × 0.05). The proportional band at the time of correction is set to 8%, the first time is set to 60 seconds, the first number of times is set to 4 times, and the predetermined time for monitoring the occurrence of pseudo hunting after correction is set to 2 minutes.
In FIG. 5, the horizontal axis indicates the elapsed time (seconds), and the left vertical axis indicates the steam pressure value (MPa).

  In the boiler system 1, the hunting detector 43 detects that the steam pressure value inside the steam header 6 has exceeded the second control pressure upper limit value (1.65 MPa) at the elapsed time t1 (first time), and the elapsed time It is detected that the steam pressure value inside the steam header 6 has exceeded the second control pressure upper limit value (1.65 MPa) (second time) at t2, and the steam pressure value inside the steam header 6 becomes the first at the elapsed time t3. 2 It was detected that the control pressure upper limit value (1.65 MPa) was exceeded (third time), and the steam pressure value inside the steam header 6 exceeded the second control pressure upper limit value (1.65 MPa) at the elapsed time t4. (4th) is detected.

  At the elapsed time t4, the hunting detection unit 43 starts the internal operation of the steam header 6 for the fourth time from the elapsed time t1 when the steam pressure value inside the steam header 6 exceeds the second control pressure upper limit (1.65 MPa) for the first time. It is detected that the time until the elapsed time t4 when the steam pressure value exceeds the second control pressure upper limit value (1.65 MPa) is within the first time (60 seconds), and the occurrence of pseudo hunting is detected. .

  In response to the detection of the occurrence of pseudo hunting by the hunting detection unit 43 at the elapsed time t4, the correction unit 44 changes the current parameter (proportional band 5%) to a new correction parameter (proportional band) corresponding to the correction number 1. 8%), the proportional band in the PI control method or PID control method is temporarily increased from 5% to 8%.

  As a result, the steam amount calculation unit 41 calculates the required steam amount by the PI control method or the PID control method based on the temporarily increased proportional band (8%) set by the parameter at the time of correction, and the output control unit 42 Will supply the steam header 6 with the required steam amount calculated based on the PI control method or the PID control method based on the proportional band (8%).

  For this reason, an excessive operation amount is not calculated with respect to the deviation between the target steam pressure value and the header pressure value, and the fluctuation of the pressure value is reduced.

As a result, the hunting detection unit 43 does not detect the occurrence of pseudo hunting from the elapsed time t4 to t5 when a predetermined time (2 minutes) set in advance elapses.
At the elapsed time t5, the correcting unit 44 replaces the current parameter (proportional band 8%) with the normal parameter before the correction (proportional band 5%), so that the proportional band in the PI control method or PID control method is set to normal. Correction to return to the hour value (5%) is performed.

  After t5, the header pressure value converges near the target pressure value. By doing so, it was possible to prevent all cans from stopping or hunting.

(Second embodiment)
Next, a second embodiment of the present invention will be described. The second embodiment will be described mainly with respect to differences from the first embodiment, and detailed description of the same configuration as the first embodiment will be omitted. In the second embodiment, the description of the first embodiment is appropriately applied to points that are not particularly described. Also in the second embodiment, the same effects as in the first embodiment are achieved.

In the boiler system 1 according to the second embodiment, the number of times that the steam pressure value inside the steam header 6 falls below the preset second control zone lower limit value or less than the second control zone lower limit value is the second. A case where the steam pressure value that occurs more than the second number of times (for example, 4 times) during a time (for example, 60 seconds) fluctuates rapidly in a low direction is regarded as a kind of pseudo hunting (hereinafter referred to as “first number”). 2).
Here, the second control zone lower limit value is a value in the vicinity of the control zone lower limit value, and for example, the absolute value of the deviation between the second control zone lower limit value and the control zone lower limit value becomes the first threshold value. Can be set to

  In addition, about 2nd time and 2nd frequency | count, it can set suitably according to the characteristic of a boiler system. For example, when the second number of times is set to “1”, the hunting detection unit 43 causes the steam pressure value inside the steam header 6 to fall below the second control zone lower limit value or less than the second control zone lower limit value. Detect if something has happened.

  The correction unit 44 of the boiler system 1 according to the second embodiment is configured so that the hunting detection unit 43 causes the second pseudo hunting (that is, the steam pressure value inside the steam header 6 to be lower than the second control zone lower limit value or 2) When the number of times that is less than or equal to the lower limit value of the control band is detected during the second time (for example, 60 seconds) is greater than or equal to the second number of times (for example, 4 times)) Correction is performed to temporarily increase the proportional band in the control method.

  Moreover, about the flowchart which shows the flow of control of the boiler system 1 of 2nd Embodiment, in the flowchart which shows the flow of control of the boiler system 1 of 1st Embodiment, "pseudo hunting", "1st time", and " About the flowchart which shows the flow of control of the boiler system 1 of 1st Embodiment by replacing "1st frequency" with "2nd pseudo hunting", "2nd time", and "2nd frequency", respectively. The explanations apply.

  Further, FIG. 6 shows temporal transition of the header pressure value when the pressure control by the PID algorithm according to the second embodiment is performed.

  In the boiler system 1, the hunting detection unit 43 detects that the steam pressure value inside the steam header 6 falls below the second control zone lower limit value at the elapsed time t′1 (first time), and the elapsed time t′2. , It is detected that the steam pressure value inside the steam header 6 falls below the second control zone lower limit (second time), and the steam pressure value inside the steam header 6 at the elapsed time t′3 becomes the second control zone. It is detected that the value falls below the lower limit value (third time), and the steam pressure value inside the steam header 6 is detected to fall below the second control zone lower limit value (fourth time) at the elapsed time t′4.

  At the elapsed time t′4, the hunting detector 43 starts the steam inside the steam header 6 for the fourth time from the elapsed time t′1 when the steam pressure value inside the steam header 6 falls below the second control zone lower limit value for the first time. It is detected that the time until the elapsed time t′4 when the pressure value falls below the second control zone lower limit value is within the second time (60 seconds), and the occurrence of pseudo hunting is detected.

  In response to the detection of the occurrence of the second pseudo hunting by the hunting detection unit 43 at the elapsed time t′4, the correction unit 44 sets the current proportional band parameter to the new proportional band parameter at the time of correction corresponding to the correction number 1. By substituting for the correction, the proportional band in the PI control method or the PID control method is temporarily increased from 5% to 8%.

  As a result, the steam amount calculation unit 41 calculates the required steam amount by the PI control method or the PID control method based on the temporarily increased proportional band (8%) set by the parameter at the time of correction, and the output control unit 42 Will supply the steam header 6 with the required steam amount calculated based on the PI control method or the PID control method based on the proportional band (8%).

  For this reason, an excessive operation amount is not calculated with respect to the deviation between the target steam pressure value and the header pressure value, and the fluctuation of the pressure value is reduced.

As a result, the hunting detection unit 43 does not detect the occurrence of the second pseudo hunting from the elapsed time t′4 to t5 when a predetermined time (2 minutes) set in advance elapses.
At the elapsed time t′5, the correction unit 44 replaces the current proportional band parameter (8%) with the normal parameter before the correction (proportional band 5%), thereby allowing the proportionality in the PI control method or the PID control method. Correction is performed to return the band to the normal value (5%).

  After t′5, the header pressure value converges near the target pressure value. By doing so, it was possible to prevent all cans from stopping or hunting.

(Third embodiment)
Next, a third embodiment of the present invention will be described. The third embodiment will be described mainly with respect to differences from the first embodiment, and detailed description of the same configuration as the first embodiment will be omitted. In the third embodiment, the description of the first embodiment is appropriately applied to points that are not particularly described. Also in the third embodiment, the same effects as in the first embodiment are achieved.

  In the boiler system 1 according to the third embodiment, the pressure drop width when the steam pressure value inside the steam header 6 drops from a value exceeding the target steam pressure value to a value lower than the target steam pressure value is preset. Steam pressure value such that the number of times the pressure drop width value is exceeded or more than the pressure drop width value is generated for the third time (for example, 4 times) or more during the third time (for example, 60 seconds) Is considered as a kind of pseudo hunting (hereinafter also referred to as “third pseudo hunting”).

  In addition, about 3rd time and 3rd frequency | count, it can set suitably according to the characteristic of a boiler system. For example, when the third number of times is set to “1”, the hunting detection unit 43 drops the steam pressure value inside the steam header 6 from a value exceeding the target steam pressure value to a value below the target steam pressure value. It is detected whether or not the pressure drop width at that time exceeds a preset pressure drop width value or exceeds the pressure drop width value.

  The correction unit 44 of the boiler system 1 according to the third embodiment uses the hunting detection unit 43 to detect the third pseudo hunting (that is, from the value at which the steam pressure value inside the steam header 6 exceeds the target steam pressure value). The number of times that the pressure drop width when dropping to a value lower than the pressure value exceeds a preset pressure drop width value or becomes equal to or greater than the pressure drop width value is the number of times during the third time (for example, 60 seconds). When the number of occurrences of 3 (for example, 4 times or more) is detected, correction is performed to temporarily increase the proportional band in the PI control method or the PID control method.

  In addition, about the flowchart which shows the flow of control of the boiler system 1 of 3rd Embodiment, in the flowchart which shows the flow of control of the boiler system 1 of 1st Embodiment, "pseudo hunting", "1st time", and " About the flowchart which shows the flow of control of the boiler system 1 of 1st Embodiment by replacing "1st frequency" with "3rd pseudo hunting", "3rd time", and "3rd frequency", respectively. The explanations apply.

  Further, FIG. 7 shows the temporal transition of the header pressure value when the pressure control by the PID algorithm according to the third embodiment is performed.

  In the boiler system 1, the hunting detector 43 is a pressure when the steam pressure value inside the steam header 6 drops from a value exceeding the target steam pressure value to a value lower than the target steam pressure value at the elapsed time t ″ 1. It is detected that the drop width exceeds the preset pressure drop width value (first time), and the steam pressure value inside the steam header 6 at the elapsed time t ″ 2 starts from the value exceeding the target steam pressure value. It is detected that the pressure drop width when dropping to a value lower than the pressure value exceeds the preset pressure drop width value (second time), and the steam pressure value inside the steam header 6 is detected at the elapsed time t ″ 3. , It is detected that the pressure drop width when dropping from a value exceeding the target steam pressure value to a value lower than the target steam pressure value exceeds a preset pressure drop width value (third time), and an elapsed time t ″ 4 In the steam header 6 It is detected that the pressure drop width when the steam pressure value of the part drops from a value exceeding the target steam pressure value to a value below the target steam pressure value exceeds a preset pressure drop width value (fourth time).

  At the elapsed time t ″ 4, the hunting detector 43 has a pressure drop width when the steam pressure value inside the steam header 6 drops from a value exceeding the target steam pressure value to a value below the target steam pressure value for the first time. From the elapsed time t ″ 1 exceeding the preset pressure drop width value, the steam pressure value inside the steam header 6 drops from a value exceeding the target steam pressure value to a value below the target steam pressure value for the fourth time. The time until the elapsed time t ″ 4 when the pressure drop width exceeds the preset pressure drop width value was detected within the third time (60 seconds), and the third pseudo hunting occurred Detect that.

  In response to the detection of the occurrence of the third pseudo hunting by the hunting detection unit 43 at the elapsed time t ″ 4, the correction unit 44 sets the current proportional band parameter to the new proportional band at the time of correction corresponding to the correction number 1. By replacing with a parameter, correction is performed to temporarily increase the proportional band in the PI control method or PID control method from 5% to 8%.

  As a result, the steam amount calculation unit 41 calculates the required steam amount by the PI control method or the PID control method based on the temporarily increased proportional band (8%) set by the parameter at the time of correction, and the output control unit 42 Will supply the steam header 6 with the required steam amount calculated based on the PI control method or the PID control method based on the proportional band (8%).

  For this reason, an excessive operation amount is not calculated with respect to the deviation between the target steam pressure value and the header pressure value, and the fluctuation of the pressure value is reduced.

As a result, the hunting detection unit 43 does not detect the occurrence of the third pseudo hunting from the elapsed time t ″ 4 to t5 when a predetermined time (2 minutes) elapses.
At the elapsed time t ″ 5, the correction unit 44 replaces the current proportional band parameter (8%) with the normal parameter before correction (proportional band 5%). Correction is performed to return the proportional band to the normal value (5%).

  After t ″ 5, the header pressure value converges in the vicinity of the target pressure value. By doing so, it was possible to prevent all cans from stopping or hunting.

(Fourth embodiment)
In addition to the first to third embodiments, any two or more pseudo huntings among pseudo hunting, second pseudo hunting, and third pseudo hunting can be detected.

  According to the boiler system 1 of 1st Embodiment demonstrated above, there exist the following effects.

(1) In the boiler system 1 according to the first embodiment described above, pseudo hunting that may cause hunting (that is, the steam pressure value inside the steam header is changed by the control unit to the plurality of boilers). The number of times that exceeds a second control pressure upper limit value set in advance between the control pressure upper limit value set in advance as a threshold for stopping all cans and the target steam pressure value, or is equal to or higher than the second control pressure upper limit value, When a fluctuation that occurs for the first time or more during the first time is detected, correction for increasing the proportional band in the PI control method or the PID control method is performed.
Thereby, the boiler system 1 which concerns on 1st Embodiment makes it possible to prevent beforehand that a header pressure value exceeds a control pressure upper limit value and raise | generates all can stop and hunting. As a result, the pressure stability of the boiler system 1 can be improved.

(2) In the boiler system 1 according to the second embodiment described above, the second pseudo hunting (that is, the steam pressure value inside the steam header 6 may be the second control zone lower limit) that may cause hunting. When the number of times that falls below the value or falls below the second control zone lower limit value is detected during the second time (for example, 60 seconds), the second number of times (for example, four times) or more) Correction for increasing the proportional band in the PI control method or the PID control method is performed.
Thereby, the boiler system 1 which concerns on 2nd Embodiment makes it possible to prevent that a header pressure value falls rapidly below a control zone lower limit, and raise | generates hunting beforehand. As a result, the pressure stability of the boiler system 1 can be improved.

(3) Further, in the boiler system 1 according to the third embodiment, the third pseudo hunting (that is, the steam pressure value inside the steam header 6 may cause the hunting) is the target steam pressure value. The third time (for example, 60 seconds) is the number of times that the pressure drop width when the pressure drop falls below the target steam pressure value exceeds the preset pressure drop width value or becomes equal to or greater than the pressure drop width value. If a third number of occurrences (for example, four times or more) is detected during this period, correction is performed to increase the proportional band in the PI control method or PID control method.
Thereby, the boiler system 1 which concerns on 3rd Embodiment makes it possible to prevent that a header pressure value fluctuates rapidly up and down a target vapor pressure, and raise | generates hunting beforehand. As a result, the pressure stability of the boiler system 1 can be improved.

(4) Moreover, in the boiler system 1 which concerns on 4th Embodiment, the operation | movement similar to 1st Embodiment, 2nd Embodiment, and 3rd Embodiment can be performed.
Thereby, in the boiler system 1 according to the fourth embodiment, it is possible to prevent hunting from occurring in the same manner as in the first embodiment, the second embodiment, and the third embodiment. As a result, the pressure stability of the boiler system 1 can be improved.

  As mentioned above, although preferable one Embodiment of the boiler system which concerns on this invention was described, this invention is not restrict | limited to the above-mentioned embodiment, It can change suitably.

  For example, in each embodiment, when controlling the amount of steam in the control unit 4, the PID control is mainly described as a control algorithm, and details of other controls (PI control and P control) are omitted. In this regard, the steam amount control executed by the control unit 4 is not limited to PID control, and may be PI control or P control.

  Further, in each embodiment, when the steam amount is controlled by the control unit 4, the required steam amount is calculated by the speed type PID algorithm. However, the required steam amount may be calculated by the position type PID algorithm.

When using the position type PID algorithm, the current required steam amount MV _{n for} each control cycle can be calculated based on the following equations (8) to (11).

Required steam volume MV _n
= Proportional control output (P control) + Integral control output (I control) + Differential control output (D control)
... (8)

Each component constituting the necessary steam amount MV _n this time is calculated by the following equations (8) to (10).
Proportional control output (MV_P) = PID_K × (target steam pressure value−current steam pressure value)
... (9)
Here, PID_K (proportional gain) is the boiler output (steam amount) per unit pressure deviation (1 kgf / cm 2 or 1 MPa).

Integral control output (MV_I) = PID_K × (target steam pressure value−cumulative value of current steam pressure value) / integration time (seconds)
(10)
Differential control output (MV_D) =
PID_K × (steam pressure value one second ago−current steam pressure value) × differentiation time (seconds)
(11)

  In each embodiment, the correction unit 44 previously stores the normal parameters and correction parameters in the storage unit 5 in order to correct the proportional band. However, instead of the correction parameters, the correction unit 44 performs correction. The unit 44 may add a predetermined increase value to the value of the normal proportional band. The correction unit 44 may multiply the value of the normal proportional band by a predetermined increase rate.

  Moreover, although each embodiment demonstrated the example which combined the pressure control by this invention and the number control of several boilers, you may apply the pressure control by this invention to the pressure control of a single boiler. In that case, the required steam amount calculated by the PID algorithm (PI algorithm or P algorithm) is set as the required steam amount in a single boiler as it is.

  Moreover, in each embodiment, although the some boiler 20 shall be comprised with a proportional control boiler, the boiler 20 is good also as not only a proportional control boiler but with a step value control boiler. The stage value control boiler has a plurality of staged combustion positions, and controls the amount of combustion by selectively turning on / off combustion, adjusting the size of the flame, etc. It is a boiler that can increase or decrease the amount of combustion in stages according to the selected combustion position. As an example, the plurality of boilers 20 may be configured by a three-position boiler having three positions, a combustion stop position, a low combustion position, and a high combustion position. Of course, the boiler 20 is not limited to three positions, and may have arbitrary N positions of combustion positions.

DESCRIPTION OF SYMBOLS 1 Boiler system 2 Boiler group 3 Boiler control apparatus 4 Control part 5 Memory | storage part 6 Steam header 7 Steam pressure sensor 18 Steam use equipment 20 Boiler 41 Steam volume calculation part 42 Output control part 43 Hunting detection part 44 Correction | amendment part 45 Fluctuation information recording part 46 History information analysis unit

Claims (7)

A plurality of boilers that can burn at different combustion rates, and supply steam to load equipment;
A steam header in which steam generated in the boiler group gathers;
A control unit for controlling the combustion state of the plurality of boilers according to a required load from a load device,
The controller is
A steam amount calculation unit that calculates the required steam amount by the PI control method or the PID control method so as to keep the steam pressure value inside the steam header at the target steam pressure value against the fluctuation of the steam consumption amount;
An output control unit for controlling the combustion state of the plurality of boilers so as to generate the necessary steam amount calculated by the steam amount calculation unit;
A hunting detector that detects fluctuations in the steam pressure value inside the steam header that may cause hunting as pseudo hunting;
A boiler system comprising: a correction unit that performs correction to increase a proportional band in the PI control method or the PID control method when the pseudo hunting is detected by the hunting detection unit. The correction unit is
After performing the correction to increase the proportional band, if the hunting detection unit does not detect the pseudo hunting for a predetermined time set in advance, the proportional band in the PI control method or the PID control method is not corrected. The boiler system of Claim 1 which performs correction | amendment which returns to the value of.   The hunting detection unit is configured such that a steam pressure value inside the steam header is between a control pressure upper limit value and a target steam pressure value that are preset as a threshold at which all the boilers are stopped by the control unit. The fluctuation that exceeds the second control pressure upper limit value set in advance or becomes equal to or greater than the second control pressure upper limit value is detected as pseudo hunting as a fluctuation that occurs for the first time or more during the first time. The boiler system according to claim 1 or 2.   The hunting detection unit is configured such that the steam pressure value inside the steam header falls below a second control zone lower limit value set in advance such that an absolute value of a deviation from the control zone lower limit value is equal to or less than a first threshold value. The boiler according to any one of claims 1 to 3, wherein a fluctuation that occurs less than or equal to the second control band lower limit value during the second time is detected as a pseudo hunting during the second time. system.   The hunting detection unit has a pressure drop width in which a pressure drop width when a steam pressure value inside the steam header drops from a value exceeding the target steam pressure value to a value lower than the target steam pressure value is set in advance. 5. The fluctuation that exceeds the value or exceeds the pressure drop width value during the third time is detected as a pseudo hunting during the third time. The boiler system described in the paragraph. The controller is
A storage unit for storing a plurality of parameters related to the proportional band in the PI control method or the PID control method;
The steam amount calculation unit calculates a required steam amount by a PI control method or a PID control method based on a proportional band set by one parameter among the plurality of parameters,
The boiler system according to any one of claims 1 to 5, wherein the correction unit corrects the proportional band using one of the plurality of parameters. The controller is
The boiler system according to any one of claims 1 to 6, further comprising a fluctuation information recording unit that records information related to the pseudo hunting when the hunting detection unit detects pseudo hunting.

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