JP2001041403A - Boiler controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a boiler controller having a quick response to the change of load immediately after the start of operation without the need of a accumulating operation data. SOLUTION: In this controller, a plurality of discrete value 51 and the setting value of a controlled variable 52 are input to an adder 53 and deviation is acquired, the control error 61 output from the adder 53 is accumulated by a accumulating compensator 54, the accumulated value 62 is input to a control gain matrix K1 (55) on the side of the discrete value and output as a manipulated variable m. A manipulated variable 59 to a boiler B output from the adder 56 is input also to a boiler dynamic characteristic model 57 for acquiring the estimated value of the inner state 63 of the boiler, such as the inlet and outlet steam temperature, pressure and enthalpy of each heat transferring element, and the estimated value of the inner state 63 estimated by the boiler dynamic characteristic model 57 is input into the control gain matrix K2 (58) and output as a manipulated value n. A final manipulated variable 59 is output as the added value of the manipulated variable m that is the calculated value of the control gain matrix K1 (55) and the manipulated variable n that is the calculated value of a control gain matrix K2 (58).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a boiler for supplying steam to a steam turbine or the like for power generation.

[0002]

2. Description of the Related Art A boiler is a device for supplying steam to a power generating steam turbine or the like. A conventional turbine-driven boiler provided with a superheater and a reheater for reusing steam rotated from a high-pressure steam turbine to improve thermal efficiency will be described with reference to the drawings.

FIG. 4 is a diagram showing the flow of combustion gas and steam in a boiler. First, the flow of the combustion gas will be described.

A boiler B is supplied with air 1 at a flow rate determined by the degree of opening of the forced-air blower damper 3 to the burner 4 by the forced-air blower 2, and burns fuel injected from the burner 4. The combustion gas generated by the combustion of the fuel rises in the furnace 5 and heats the suspended superheater 6 and the suspended reheater 7, and then, partly controls the horizontal reheater 8 and the economizer 9. It joins after passing through the first path for heating and the rest through the second path for heating the horizontal superheater 10 and the economizer 9 respectively. And
Combustion gas having a flow rate determined by the degree of opening of the recirculation gas damper 11 is returned to the furnace 5 by the recirculation gas fan 12, and the remainder is discharged into the atmosphere from the exhaust port 13. The flow rate of the combustion gas passing through the first and second paths is determined by the opening degree of the reheater parallel damper 14 and the superheater parallel damper 15.

Next, the flow of steam will be described.

[0006] Water 20 sent out by a water supply pump (not shown) is heated by a economizer 9 to form a steam-water mixture inside a furnace water wall 21 and is guided to a steam-water separator 22 where the drain is separated and stored in a water storage tank. It is led to 23. On the other hand, the steam is superheated by the horizontal superheater 10 and the suspended superheater 6, and then the main steam 24 is heated.
Is supplied to a high-pressure turbine (not shown). Exhaust steam 25 from the high-pressure turbine is supplied to the horizontal reheater 8 and the suspended reheater 7.
, And supplied to a medium-pressure turbine (not shown) as reheated steam 26. Reference numeral 27 denotes a boiler control device that controls various pumps and valves.

Next, a control procedure of the boiler will be described.

When the magnitude of the output output from the generator (hereinafter referred to as the set output P) is determined, the set value Qp of the main steam flow rate Q to be supplied to the turbine and the necessary value for generating the main steam having the set value Qp are generated. Set value Wp of the supply water flow rate W, set value F of the fuel flow rate F required to generate the main steam having the set value Qp
p, a set value Ap of the air flow rate A required to burn the fuel of the set value Fp, and a set value Rp of the recirculation gas flow rate R,
Further, a set value Gp of the combustion gas flow rate G passing through the first and second paths for setting the steam to a required temperature is determined.
Therefore, the control device 27 calculates a physical quantity corresponding to each of the flow rates,
That is, based on the measured values such as temperature and steam pressure, the related devices are controlled so that the actual measured values become equal to the set values, and the above set values are set so that the output of the generator becomes the set output P. Is corrected.

FIG. 5 shows a control procedure of a conventional boiler. The boiler is controlled in the following procedure.

In the case of a turbine-driven boiler, the generator output J is immediately determined by the flow rate of the main steam supplied to the turbine. Therefore, the control device 27 compares the measured generator output J and the set output (power generation command value) P with each other. Then, the opening correction signal Gh is output to the governor that controls the main steam flow rate Q sent to the turbine according to the difference between the two.

The feedwater flow rate W is compared with the measured steam pressure Wj and the set value Wp of the steam pressure Wj, and the result is corrected by the opening correction signal Gh, and a feedwater flow correction signal Wh is output to a feed pump (not shown). I do.

The fuel flow rate F is the measured main steam temperature Tj
Is compared with the set value Tp of the main steam temperature Tj, and the result is corrected by the feedwater flow correction signal Wh to output a fuel flow correction signal Fh to a fuel supply device (not shown).

The air flow rate A compares the measured oxygen concentration Oj with the set value Op of the oxygen concentration Oj, corrects the result with the fuel flow rate correction signal Fh, and outputs an air flow rate correction signal Ah to the push-in blower damper 3. I do.

The recirculation gas flow rate R is compared with the measured reheat steam temperature Tjp and a set value Trp of the reheat steam temperature Tjp, and the result is corrected by the feedwater flow rate correction signal Wh to open the recirculation gas damper 11. The degree correction signal Rh is output.

The combustion gas flow rate G is compared between the measured steam temperature Tsj at the outlet of the horizontal reheater and the set value Tsp of the steam temperature Tsj at the outlet of the horizontal reheater, and the result is corrected by the opening correction signal Rh. Then, an opening correction signal Dh of the reheater parallel damper 14 and the superheater parallel damper 15 is output.

In the conventional boiler taking such a control procedure, for example, when the governor opening degree is corrected by the governor opening degree correction signal Gh and the main steam flow rate Q is corrected, the corrected main steam flow is corrected. In order to supply the flow rate Q, the feedwater flow rate correction signal Wh determines the feedwater flow rate W, the fuel flow rate correction signal Fh determines the fuel flow rate F, the airflow rate correction signal Ah determines the air flow rate A, and the opening degree correction signal Rh determines the recirculation gas. The flow rate R is also determined by the opening correction signal Dh for the first and second flow rates.
Are corrected respectively. As a result, the generator output J was able to approach the set output P.

[0017]

SUMMARY OF THE INVENTION As in a constant output state,
When the difference between the generator output J and the set output P is small, there is almost no problem with the above control. However, when changing the generator output P, it took time for the output to stabilize. FIG. 6 shows that the generator output P is increased from 100% to 50%.
5 shows the response of the generator output J when the power is changed to%. The response of the generator output J to the command value indicated by the solid line is indicated by the dotted line, and it takes time for the output to become stable. This is for the following reason.

That is, in the above prior art, when the measured main steam temperature Tj is higher than the set value Tp, the fuel flow rate F is decreased in order to lower the main steam temperature T. Fuel flow rate F
Decreases, the temperature of the combustion gas decreases, and the measured reheat steam temperature Tsj becomes lower than the set value Tsp. Therefore, when the opening degree of the recirculation gas damper 11 is increased to increase the recirculation gas amount R in order to increase the reheat steam temperature Ts, the internal gas temperature of the furnace 5 decreases, and the main steam temperature Tj decreases to the set value Tp. Lower than. Then, an operation of increasing the main steam temperature T is performed in the reverse order to the above, and the main steam temperature Tj measured reversely returns to the initial state higher than the set value Tp. It was repeated and it took time for the output to stabilize. Further, since the change in the steam temperature with respect to the change in the temperature of the combustion gas is delayed, the control is troublesome.

The response speed of the generator output J when changing the generator output P can be improved by accumulating the operation data of the boiler. However, since the dynamic characteristics of the boiler differ depending on the load, a large amount of time was required to accumulate data.

An object of the present invention is to solve the above-mentioned problems in the prior art, and to provide a boiler control device which does not require accumulation of operation data and has a quick response to a load change immediately after the start of operation.

[0021]

In order to achieve the above object, the present invention provides a steam system from a feed water heater through a heat transfer tube to a turbine, a gas system in consideration of fuel combustion, and a transfer from a gas side. A boiler dynamic characteristic model that considers thermal characteristics, and a boiler control device that controls the operation state of the boiler based on the output of the boiler dynamic characteristic model and actual measurement values of each part of the boiler. Control means for obtaining an internal state estimated value including at least one of the temperature, pressure, and enthalpy of each of the heat transfer element inlet and outlet steam based on the measured values of the boiler components, and inputting the internal state estimated value and the measured value For controlling the boiler so as to minimize the evaluation function set in advance by an arithmetic expression based on each value including the temperature deviation, the generator output deviation, the pressure deviation, and the spray operation amount. And a configuration in which an optimum operating gain matrix calculation means for determining a proper operation amount.

In this case, the optimal operation gain matrix minimizes a deviation from a plurality of control amounts, an estimated value of a state amount obtained from an arbitrary parameter affecting the control amount, and an evaluation function determined by the operation amount. Asked to do
As the evaluation function, for example, a quadratic evaluation function can be used. Further, it is preferable that the optimal operation gain matrix is changed according to a power generation command.

Note that the deviation from a plurality of control variables for obtaining the optimal operation gain matrix is defined by integrating a deviation 61 between a control variable (measured value) 51 and a control variable set value 52 in the following embodiment. This is an integrated value 62 integrated by the compensator 54. Further, the estimated value of the state quantity obtained from an arbitrary parameter affecting the control amount is the estimated internal state value 63 estimated using the boiler dynamic characteristic model 57. Note that the optimal operation amount at this time is the operation amount 59 from the accumulator 56 obtained by adding the operation amounts m and n obtained by calculating the control gain matrices K1 and K2.

[0024]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a control system diagram according to an embodiment of the present invention. The same reference numerals are given to the same components as those in FIG. 4 and the description is omitted. In FIG. 1, reference numeral 50 denotes the entire control system (arithmetic unit) of the control device 27. The control system 50 includes an adder 53, an integral compensator 54, and a control gain matrix K on the measurement value side.
1 (55), an adder 56, a boiler dynamic characteristic model 57, and a control gain matrix K2 (58) on the estimated value side. This control system includes two control systems including a control gain matrix K1 (55) on the measurement value side and a control gain matrix K2 (58) on the control side. The boiler dynamic characteristic model 57 is for obtaining an estimated value 63 of the internal state of the boiler such as the steam temperature, pressure, and enthalpy at the entrance and exit of each heat transfer element such as the horizontal superheater 10.

A plurality of measurement values (control amounts) 5 from boiler B
1 and the control amount set value 52 are input to an adder 53, and a deviation is obtained. A control deviation 61 output from the adder 53 is integrated by an integration compensator 54, and the integrated value 62 is a control gain on the measured value side. It is input to the matrix K1 (55) and output as the manipulated variable m.

On the other hand, the boiler B output from the adder 56
Is input to the boiler dynamic characteristic model 57, and the internal state estimation value 63 estimated using the boiler dynamic characteristic model 57 is input to the control gain matrix K2 (58) on the control side, and the operation amount n Is output as The operation amount 59 is actually the operation amount m, which is the operation value of the measured value-side control gain matrix K1 (55), and the control-side control gain matrix K2.
This is an addition value of the operation amount n which is the operation value of (58).

As the evaluation function, for example, a quadratic evaluation function is employed. FIG. 2 shows a procedure for deriving the quadratic form evaluation function.

When it is desired to control the control amount θ (t) like the target value r (t), some errors actually occur as shown in FIG. Therefore, in order to objectively evaluate whether the control of FIG. 2A is good, for example, if the deviation between the control amount and the target value is y (t) = θ (t) −r (t), The area of the shaded area in FIG.

(Equation 1) Should be minimized. Here, the expression shown in Expression (1) is an example of the evaluation function.

However, even when undesired control is performed as shown in FIG. 2B, there is a case where the evaluation function J is minimized due to the cancellation of the positive and negative.

Therefore, in order to prevent this, y in Expression (1) is used.
(T) is squared to obtain the following equation (2)

(Equation 2) Set the evaluation function to a format like Further, in order to control a plurality of control amounts, y (t) is vectorized as in the following equation (3).

[0032]

(Equation 3) This equation (3) is called a quadratic evaluation function. As will be described later, it is necessary to separately specify the weight of each component of Q and y (t) in the expression (3) which is the evaluation function. For example, if the weights of all the control amounts are the same, a unit matrix as shown in the following equation (4) is obtained.

[0033]

(Equation 4) Furthermore, when the manipulated variables (inputs) are incorporated in the evaluation function, the following equation is obtained, and the general function is obtained when the optimal regulator theory is applied.

[0034]

(Equation 5) As this kind of quadratic evaluation function, for example, a function disclosed in Japanese Patent No. 2521722 is known.

In the present invention, the weight of the evaluation function is adjusted instead of emphasizing the parameters of the proportional, integral and differential elements constituting the conventional steam control system. The adjustment of the weight must be performed by trial and error to some extent, but can be adjusted as follows, for example.

That is, a case where the dynamic characteristic model is a general linear model used for control and the following equation (6) and the evaluation function is the above equation (5) will be described by way of example.

[0037]

(Equation 6) Here, in Expression (6), x is a state variable, u is an operation amount (input), y is a control amount (output), and A, B, and C are coefficient matrices.

In such a model, the control amount is three elements of the main steam temperature, the main steam pressure, and the output (MW), and the operation amount is three elements of the fuel flow rate, the feedwater flow rate, and the governor opening degree, and the dynamic characteristics are six elements in total. Suppose the model is represented. In that case, (5)
Q and R in the equation are represented by the following equation (7).

[0039]

(Equation 7) However, in equation (7), for simplicity, elements other than the diagonal elements are set to “0”.

Q11, q22, q3 in equation (7)
3, r11, r22, and r33 correspond to the main steam temperature, the main steam pressure, the output (MW), the fuel flow rate, the feedwater flow rate, and the governor opening, respectively. If the same weight is used for all control amounts and operation amounts, Expression (7) becomes Expression (8) below.

[0041]

(Equation 8) Here, for example, if the optimal regulator theory is applied,
The gain matrices K1 and K2 having the weight of the expression (8) and minimizing the evaluation function (5) can be obtained. Simulation is performed using the obtained K1 and K2 as control gains, and if the result is satisfactory, K1 and K2 can be adopted. However, if you are not satisfied, you need to adjust the weights. For example, if the simulation results show that the main steam temperature fluctuates greatly and there is a margin for the feedwater flow rate, in other words, if the flow rate can be increased even though the flow rate is not increased much, for example, (9) As shown in the equation, the weight of the main steam temperature is increased and the weight of the feedwater flow rate is decreased.

[0042]

(Equation 9) The magnitude by which the weight is changed is determined by trial and error while performing the simulation again. For this weight, trial and error redundant calculation is required,
Since it is a general problem in designing a multivariable control system,
No special boiler knowledge is required. Therefore, for example, an analysis method that has already been developed can be used. Therefore, unlike the PID adjustment performed in the conventional control system design, the calculation is performed by the automatic calculation of the computer without requiring the experience and intuition of a skilled person, and as a result, the development efficiency is improved.

As described above, the control gain matrices K1 and K2 can be obtained by applying the optimal regulator theory. However, the coefficient matrices A, B, and C of the dynamic characteristic model of the boiler represented by the equation (6) are nonlinear, and A, B, and C are different in different states. Therefore Q, R and A,
The control gain matrices K1 and K2 obtained from B and C need to be recreated in different states. Therefore, the control gain matrices K1 and K2 are actually changed according to the state. This change can be made, for example, by creating optimal K1 ₁₀₀ and K2 ₁₀₀ in advance in a steady state at a load of 100%, and similarly in 90%, 80%,. . . K1 at 0%
₉₀ , K2 ₉₀ , K1 ₈₀ , K2 ₈₀ ,. . . K1 _0,
You create a K2 _0. When the load is 95% or more, K1 ₁₀₀ and K2 ₁₀₀ are used as control gains, and when the load is 85% to 95%, K1 ₉₀ and K2 ₉₀ are switched.

According to this method, since the control gain matrices K1 and K2 are prepared in advance, the amount of calculation during operation is reduced. Since the states do not always coincide with each other, K1 ₉₀ and K2 ₉₀ are not necessarily optimal control gains. However, in this method, more preferable control can be performed by switching than by not switching.

As another method, there is a method in which the optimum control gains K1 and K2 are sequentially calculated according to the state at that time, and control is performed while sequentially switching the gains K1 and K2. However, this method requires a large amount of calculation to calculate the control gain every time.

Incidentally, in the usual optimal regulator theory,
Although the objective is to optimize the control amount y (corresponding to the integral value 62) and the operation amount u (corresponding to the operation amount 59) as in the above equation (5), in this embodiment, the state quantity (internal (Corresponding to the state estimation value 63) is also optimized.

Although an example in which a quadratic form evaluation function is adopted as the evaluation function is described here, it goes without saying that another evaluation function can be adopted.

Next, the operation of this embodiment will be described.

When the generator output P is constant, the generator output J
Further, a set value 52 such as a temperature, a pressure, and a spray water amount of each part of the boiler is compared with a measured value 51 by a comparator 53, and the difference is integrated by an integrator 54. Then, a control gain matrix K1 (55) corresponding to the integration result and the generator output P at this time is obtained.
The operation amount m is calculated from On the other hand, the operation amount n is calculated from the internal state estimation value 63 output by inputting the operation amount 59 to the boiler dynamic characteristic model 57 and the control gain matrix K2 (58) corresponding to the generator output P at this time. . Then, the operation amount m and the operation amount n are added by the adder 56 to obtain an optimum operation amount 59.

When changing the generator output P,
Each time the generator output P changes, the control gain matrices K1, K2 corresponding to the generator output P at that time are used.

FIG. 3 shows that the generator output P is increased from 100% to 50%.
5 shows the response characteristics of the generator output J when the output is changed to%. The response of the generator output J to the command value indicated by the solid line is indicated by the dotted line, and the output does not vibrate after the generator output P reaches 50%.

In the present embodiment, the effect of each minute change in all control amounts and operation amounts on all other control amounts and operation amounts is quantified and controlled by a multivariable control system used for control. As a result, there is no interference between the control amounts and the operation amounts, and the response of the control amount when the load changes can be accelerated. Moreover, normally, the control gains K1 and K2 of the multivariable control system for the linear model are provided in advance for each output of the generator output P, and the control is performed using the optimum control gain. Can do
The generator output J can be quickly changed to the generator output P without excessively large overshoot or vibration due to too large an operation amount, or conversely, deterioration in followability due to too small an operation amount.
Can be adjusted to

[0053]

As described above, according to the present invention,
Control means for obtaining an internal state estimated value including at least one of the temperature, pressure and enthalpy of each heat transfer element inlet / outlet steam based on the output of the boiler dynamic characteristic model and the actually measured value of each part of the boiler; Optimum operation amount for controlling the boiler so as to minimize the evaluation function set by an arithmetic expression based on each value including the temperature deviation, generator output deviation, pressure deviation, and spray operation amount with the actual measurement value as input And an optimal operation gain matrix operation means for determining
By the multivariable control, each control element does not interfere, and the controllability is excellent. Further, since the internal model can cope with the slow response of the boiler, it is possible to cope with a high-speed load change and control according to the non-linearity of the boiler becomes possible.

[Brief description of the drawings]

FIG. 1 is a control system diagram according to an embodiment of the present invention.

FIG. 2 is a diagram showing a procedure for deriving a quadratic evaluation function.

FIG. 3 is a diagram showing a response of a generator output according to the embodiment of the present invention.

FIG. 4 is a diagram showing flows of combustion gas and steam in a boiler.

FIG. 5 is a conventional control system diagram.

FIG. 6 is a diagram showing a response of a conventional generator output.

[Explanation of symbols]

 Reference Signs List 50 Overall control system (arithmetic unit) 51 Measured value (control amount) 52 Control value set value 53, 56 Adder 54 Integration compensator 55 Control gain matrix K1 on measured value side 57 Boiler dynamic characteristic model 58 Control gain matrix on control side K2 59 Final manipulated variable 61 Control deviation 62 Integral value 63 Internal state estimated value B Boiler m, n manipulated variable

Continued on the front page F-term (reference) 3L021 AA05 CA06 DA04 DA05 DA38 EA04 FA02 FA12 5H004 GA16 GA30 GB04 HA01 HA03 HA14 HA16 HB01 HB02 HB03 HB14 JA23 JB08 KA71 KA72 KB05 KB38 KB39 KC17 KC22 KC27 KC32 KC13 LA18 HH34 KK55

Claims (4)

[Claims] A boiler dynamic characteristic model which takes into account a steam system from a feed water heater to a turbine through a heat transfer tube to a turbine, a gas system taking fuel combustion into consideration, and a heat transfer characteristic from the gas side. A boiler control device that controls a boiler operating state based on an output of a dynamic characteristic model and an actually measured value of each part of the boiler. Control means for obtaining an internal state estimated value including at least one of steam temperature, pressure and enthalpy; and a temperature operation, a generator output error, a pressure error, and a spray operation in advance by using the internal state estimated value and the actually measured value as inputs. Optimal operation gain matrix operation means for determining an optimal operation amount for controlling the boiler so as to minimize the evaluation function set by the operation expression based on each value including the amount, Boiler control device characterized by comprising. 2. The optimal operation gain matrix minimizes a deviation from a plurality of control amounts, an estimated value of a state amount obtained from an arbitrary parameter affecting the control amount, and an evaluation function determined by the operation amount. The boiler control device according to claim 1, wherein the boiler control device is obtained as described above. 3. The control device for a boiler according to claim 1, wherein the evaluation function is a quadratic form evaluation function. 4. The boiler control device according to claim 1, wherein the optimum operation gain matrix is changed according to a power generation command.