CN106556149A - Multiple branch circuit multi-burner heating furnace branch balance control method and system - Google Patents

Abstract

The present invention discloses a kind of multiple branch circuit multi-burner heating furnace branch balance control method and system, by the transmission function for recognizing each branch road, set up nominal model and calculate the PID controller parameter under given Robust Stability Conditions, with the PID controller parameter as control signal output to heating furnace entrance, to adjust oil flow, so that each branch road outlet temperature reaches consistent effect, it is applicable not only to each branch road transmission function identical homogeneous system, it is particularly suited for the different alien system of each branch road transmission function, alien system is solved with the difficulty that nominal model is selected during IMC-PID.

Description

Multiple branch circuit multi-burner heating furnace branch balance control method and system

Technical field

The invention belongs to the automation field of petrochemical industry tubular heater, particularly multiple branch circuit multi-burner heating furnace branch road are flat Weighing apparatus control method and system.

Background technology

In oil plant, commonly used is the heating furnace of multiple branch circuit multi-combustor, and raw material is dividedly flowed into Jing after total pipeline charging Enter each branch road, each branch road has burner to heat which, the crude oil after heating is admixed together by each branch road again.It is preferable State is that each branch road Crude Oil flow is equal, and burner flame state is identical, then outlet temperature also should be identical.But it is actual In production, unavoidably there is interference, so as to be difficult to ensure that outlet temperature is identical.If a certain branch road temperature drift, can cause Slagging, affects pipe heat-transfer coefficient, and pipeline is tightened up, reduce flow, so that temperature is further improved, cause Vicious cycle, may cause pipeline breaking when serious, this is extremely dangerous.Therefore furnace outlet temperature must be controlled System, it is ensured that outlet temperature is identical.Existing control program large deviations control technology (DCT) mentality of designing is simple, but works as When number of branches is more, control structure is complicated, it is difficult to implement；Many deviation control technologies (DSCT) compensate for deviation control technology Deficiency, it can be difficult to ensureing that outlet temperature is exactly mixed temperature；Broad sense Compensating Control (GC2T) controls skill to many deviations After art is improved, its shortcoming is made up, but it is less for its effective controller design scheme, it is especially for alien system, difficult To provide unified pid parameter.

The content of the invention

In order to solve above-mentioned deficiency of the prior art, the present invention proposes multiple branch circuit multi-burner heating furnace branch balance controlling party Method, comprises the following steps：

The outlet temperature of S1, the oil flow of each branch input of measurement and outfan, by the crude stream value and outlet temperature Value is converted into the signal of telecommunication；

S2, the signal of telecommunication that S1 steps are obtained is stored, after storage time t, the signal of telecommunication is sent to into system identification mould Block；

S3, the transmission function that each branch road is recognized using linear least squares method algorithm；

S4, optimum nominal model is obtained according to the frequency characteristic of the transmission function of each branch road, then calculated in given robustness bar PID controller parameter under part；

S5, PID controller parameter are sent to controller as control signal, control oil flow.

Storage time t is that, from the step signal moment for recognizing each branch road is added, reaching new steady-state value to output is Time period only.

The detailed process of S3 is：Output Y (k) of amplitude h, sampling period Ts and acquisition target according to the step signal,

The parameter being calculated in the transmission function of each branch road according to the following formula

θ=(P^T·P)^-1P^TQ

Wherein P and Q are the coefficient matrix being made up of h, ts, Y (k) respectively, and θ is the ginseng for identifying the transmission function of each branch road Number.

The detailed process of S4 is：

S401, frequency characteristic G that each branch road is calculated according to the transmission function of each branch road_i(jw)；

S402, frequency characteristic of the average as optimum nominal model for choosing each branch road frequency characteristic,

Wherein, N is circuitry number；

S403, the transmission function that nominal model is calculated using method of least square,

Wherein, L be the pure delay time of nominal model, K be gain, T be time constant, s be Laplace operator；

S404, given initial λ=0.1L, calculate its corresponding peak response Ms, If Ms ＜ 1.4, terminate to calculate；λ=λ+0.05L are otherwise made, then substitutes into formulaDirectly To Ms ＜ 1.4；

S405, the parameter for calculating PID controller

C_PID(s)=K_p+K_I/s

Wherein K_p=T/K/ (λ+L), K_I=1/K/ (λ+L).

The multiple branch circuit multi-burner heating furnace branch balance control method of the present invention nominal model selected when internal mode controller is designed It is not based on the model of some branch road, but considers the characteristic of each branch road, designs internal mode controller on this basis, can be with Effectively outlet temperature is controlled.

Second aspect, the present invention provide a kind of multiple branch circuit multi-burner heating furnace branch balance control system, including what is be sequentially connected Measuring transducer and data storage and output unit, it is characterised in that be also linked in sequence after the data storage and output unit There are system identification unit, parameter analysis unit and controller output unit, wherein

Measuring transducer, for gathering input signal and output signal；

Data storage and output unit, the data that measuring transducer transmission comes are stored, and are exported to system identification list Unit；

System identification unit, identifies the transmission function of each branch road using identification algorithm；

Parameter analysis unit, the nominal model for transferring function by frequency-response analysis, finding out optimum by each branch road, and utilize Internal model strategy and nominal model calculate the PID controller parameter under given Robust Stability Conditions；

The control signal that PID controller is exported is sent to each branch road entrance, to adjust the original of each branch road by controller output unit Stream amount.

Using multiple branch circuit multi-burner heating furnace branch balance control system of the present invention, the constant constraints of total feed is being met Under, when difference occurs in the outlet temperature of each branch road, automatically the flow of each branch road is adjusted, so that furnace outlet is each The temperature of branch road is identical.

Description of the drawings

Flow charts of the Fig. 1 for embodiment of the present invention multiple branch circuit multi-burner heating furnace branch balance control method；

Fig. 2 is another embodiment of the present invention multiple branch circuit multi-burner heating furnace branch balance control system architecture figure；

Fig. 3 is the schematic diagram in the embodiment of Fig. 1 using multiple perturb expression nominal model and each branch model difference.

Specific embodiment

In order that the objects, technical solutions and advantages of the present invention become more apparent, below in conjunction with drawings and Examples, to this It is bright to be further elaborated.It should be appreciated that specific embodiment described herein is only to explain the present invention, and without It is of the invention in limiting.

Multiple branch circuit multi-burner heating furnace branch balance control method embodiment as shown in figure 1, comprise the following steps,

The circuitry number for assuming heating furnace is 4, and total feed is 140t/h, and the gas flow of burner is constant, by each branch road The outlet temperature of each branch road of flow-control；

Step 1, from the input end measuring crude stream value of each branch road, from each branch road measurement of output end crude exports temperature value, will Flow value and temperature value pick-up are the signal of telecommunication；

The signal of telecommunication in step 2, storing step 1, after meeting the quantity required for each branch road of identification, the signal of telecommunication is transmitted To system identification module；

Step 3, the transmission function that each branch road is recognized according to the linear least squares method algorithm of setting；

For homogeneous system, the plant characteristic of its each branch road is identical, therefore the transfer function model of each branch road is identical, i.e., G₁(s)=G₂(s)=G₃(s)=G₄(s)=- 5e^-60s/(160s+1)；

For alien system, the plant characteristic of each branch road has different, therefore the transmission letter of recognized each branch road for obtaining Number is also different, but as its essential structure is roughly the same with working condition, therefore difference mostlys come from the parameter of object. Equally be the heating furnace of four branch roads, it is recognized after, the transmission function of four branch roads is respectively：

Step 4, frequency analyses are transferred function by each branch road, the average frequency characteristic of each branch road is obtained as nominal model Frequency characteristic, recycle compound curve fitting technique to obtain the transmission function of nominal model；Using the ginseng of nominal model transmission function Number finds out the internal mode controller parameter for meeting given robustness requirement；Corresponding PID control is obtained by internal mode controller parameter finally Device parameter.

For homogeneous system, nominal model is necessarily satisfying for G (s)=G₁(s)=G₂(s)=G₃(s)=G₄(s)=- 5^e-60s/ (160s+1), Parameter analysis unit can provide the internal mode controller of (Ms ＜ 1.4) under the conditions of meeting certain robust for the nominal model that calculates Parameter of PID controller of equal value with which, be respectively：G_IMC(s)=- (160s+1)/(450s+5), G_PID(s)=- (0.2133+0.0013/s)；

For alien system, as the transmission function of each branch road is differed, choose nominal model on, by each branch road with it is nominal The difference of model is regarded as model uncertainty to process, while considering with multiple perturbation to describe uncertain domain.As shown in figure 3, Branch road 1 and branch road 2 have different frequency response curves, in order that selected nominal model can with a less uncertain domain (compared with Little disc radius) curve of branch road 1 and 2 is surrounded, best mode is the center line for selecting branch road 1 and 2 curves as mark Claim the frequency characteristic of object, in the same manner, for the heating furnace for having N number of branch road, the frequency characteristic of its nominal model can be as the following formula It is calculated：

In order to reduce the robustness requirement of controller, the Nyquist of the center line as nominal model of each branch road Nyquist curves is chosen Curve, recycles compound curve fitting technique to obtain the transmission function of nominal model, requires to pass through according to the frequency characteristic of nominal model Least-squares algorithm can obtain the transmission function of the present embodiment nominal model：

According to nominal model, under certain Robust Stability Conditions, (Ms ＜ 1.4) available PID controller is： G_PID(s)=- (0.2441+0.0015/s).

Step 5, PID controller parameter are admitted to controller output unit and act on for output control.

The present embodiment is applicable not only to each branch road transmission function identical homogeneous system in selection nominal model, is particularly suited for each The different alien system of branch road transmission function, solves alien system with the difficulty that nominal model is selected during IMC-PID.

Embodiment 2

The present embodiment is multiple branch circuit multi-burner heating furnace branch balance control system, and its structure is as shown in Figure 2.

The present embodiment also includes in addition to the heating furnace comprising with n branch road：Measuring transducer, for measuring each The oil flow of road porch and the temperature in exit, and be the signal of telecommunication by above parameter pick-up；

Data storage and output unit, the signal of transmitter of testing oneself in the future are stored, until meeting required for each branch road of identification Data volume, then output a signal to system identification unit；

System identification unit, for by calculating, picking out the transmission function of each branch road；

Parameter analysis unit, the nominal model for transferring function by frequency-response analysis, finding out optimum by each branch road for obtaining, And the PID controller parameter under the conditions of certain robustness is automatically calculated using internal model strategy and nominal model；

The control signal that PID controller is exported is sent to each branch road entrance, to adjust the original of each branch road by controller output unit Stream amount.

Technological means disclosed in the present invention program are not limited only to the technological means disclosed in above-mentioned embodiment, also include by the above The technical scheme constituted by technical characteristic combination in any.

Claims (5)

1. multiple branch circuit multi-burner heating furnace branch balance control method, it is characterised in that perform following steps,

The outlet temperature of S1, the oil flow of each branch input of measurement and outfan, by the crude stream value and outlet temperature Value is converted into the signal of telecommunication；

S2, the signal of telecommunication that S1 steps are obtained is stored, after storage time t, the signal of telecommunication is sent to into system identification mould Block；

S3, the transmission function that each branch road is recognized using linear least squares method algorithm；

S4, optimum nominal model is obtained according to the frequency characteristic of the transmission function of each branch road, then calculated in given robustness bar PID controller parameter under part；

S5, PID controller parameter are sent to controller as control signal, control oil flow.

2. multiple branch circuit multi-burner heating furnace branch balance control method according to claim 1, it is characterised in that described Storage time t is from the step signal moment for recognizing each branch road is added, to output reaches new steady-state value Time period.

3. multiple branch circuit multi-burner heating furnace branch balance control method according to claim 2, it is characterised in that described The detailed process of S3 is：Output Y (k) of amplitude h, sampling period Ts and acquisition target according to the step signal, The parameter being calculated in the transmission function of each branch road according to the following formula

$P=\left[\begin{array}{ccc}Y\left(1\right)-Y\left(0\right)& -Tsh& h\\ Y\left(2\right)-Y\left(0\right)& -2Tsh& h\\ .& .& .\\ .& .& .\\ .& .& .\\ Y\left(n\right)-Y\left(0\right)& -nTsh& h\end{array}\right]$ $\mathrm{\θ}=\left[\begin{array}{c}{\mathrm{\θ}}_1\\ {\mathrm{\θ}}_2\\ {\mathrm{\θ}}_3\end{array}\right]$

$Q=\left[\begin{array}{c}-Ts\underset{i=0}{\overset{1}{\Σ}}Y\left(i\right)\\ -Ts\underset{i=0}{\overset{2}{\Σ}}Y\left(i\right)\\ .\\ .\\ .\\ -Ts\underset{i=0}{\overset{n}{\Σ}}Y\left(i\right)\end{array}\right]$

θ=(P^T·P)^-1P^TQ

Wherein P and Q are the coefficient matrix being made up of h, Ts, Y (k) respectively, and θ is the ginseng for identifying the transmission function of each branch road Number.

4. multiple branch circuit multi-burner heating furnace branch balance control method according to claim 1, it is characterised in that S4 Detailed process be：

S401, frequency characteristic G that each branch road is calculated according to the transmission function of each branch road_i(jw)；

S402, frequency characteristic of the average as optimum nominal model for choosing each branch road frequency characteristic,

$\stackrel{\‾}{G}\left(jw\right)=\frac{1}{N}\underset{i=1}{\overset{N}{\Σ}}{G}_i\left(jw\right)$

Wherein, N is circuitry number；

S403, the transmission function that nominal model is calculated using method of least square,

$\stackrel{\‾}{G}\left(s\right)={\mathrm{Ke}}^{-Ls}/(Ts+1)$

Wherein, L be the pure delay time of nominal model, K be gain, T be time constant, s be Laplace operator；

S404, given initial λ=0.1L, calculate its corresponding peak response Ms, If Ms<1.4, then terminate to calculate；λ=λ+0.05L are otherwise made, then substitutes into formulaDirectly To Ms<1.4；

S405, the parameter for calculating PID controller

C_PID(s)=K_p+K_I/s

Wherein K_p=T/K/ (λ+L), K_I=1/K/ (λ+L).

5. multiple branch circuit multi-burner heating furnace branch balance control system, including the measuring transducer and data storage being sequentially connected with Output unit, it is characterised in that being also linked in sequence after the data storage and output unit has system identification unit, ginseng Number analytic unit and controller output unit, wherein

Measuring transducer, for gathering input signal and output signal；

Data storage and output unit, the data that measuring transducer transmission comes are stored, and are exported to system identification list Unit；

System identification unit, identifies the transmission function of each branch road using identification algorithm；

Parameter analysis unit, the nominal model for transferring function by frequency-response analysis, finding out optimum by each branch road, and utilize Internal model strategy and nominal model calculate the PID controller parameter under given Robust Stability Conditions；

The control signal that PID controller is exported is sent to each branch road entrance, to adjust the original of each branch road by controller output unit Oily flow.