CN101709863B - Hybrid control method for furnace pressure system of coal-fired boiler - Google Patents

Abstract

The invention relates to a hybrid control method for a furnace pressure system of a coal-fired boiler, which is characterized by firstly establishing a process model based on the real-time process data of the furnace pressure of the coal-fired boiler and digging out the basic process characteristics; then establishing a proportional-integral (PI) control circuit based on the process model; and finally implementing predictive PI control on PI differentiation control and the furnace pressure object of the coal-fired boiler wholly by computing the parameters of a predictive PI controller. The method of the invention makes up for the deficiency of traditional control, effectively facilitates the design of the controller, ensures the control performance to be elevated and simultaneously meets the given production performance index. The control technology provided by the invention can effectively reduce the error between the technological parameters of the ideal furnace pressure and the actual furnace pressure, further make up for the deficiency of the traditional controller and simultaneously ensure the control device to operate in the optimum state so as to ensure the technological parameter of the furnace pressure in the production process to be strictly controlled.

Description

Hybrid control method for furnace pressure system of coal-fired boiler

Technical field

The invention belongs to technical field of automation, relate to the mixing control method of prediction proportional plus integral control (predictive PI) with the PID control (PID) of a kind of coal-burning boiler furnace pressure system.

Background technology

Coal-burning boiler is the important motivity equipment of electrical production department, and its requirement is to supply with qualified steam, makes the coal-burning boiler steam exhaling amount adapt to the needs of load.For this reason, each main technologic parameters of production process must strict control.Yet coal-burning boiler equipment is the controlled device of a complicacy, and is interrelated between input quantity and the output quantity.For the boiler furnace pressure system: steam load changes and causes when steam pressure and superheat steam temperature change, and causes that also furnace pressure changes; The variation of fuel quantity directly influences steam pressure, the variation of superheat steam temperature, excess air and combustion chamber draft; The variation of desuperheating water can cause superheat steam temperature, steam pressure to change, and further causes the variation of furnace pressure etc.These unfavorable factors cause traditional control device precision not high, further cause subsequent production control parameter unstable again, and product percent of pass is low, and boiler efficiency is low.Traditional simple control device is adopted in the furnace pressure control of coal-burning boiler basically in the actual industrial at present, even manual operation, and the control parameter relies on technical staff's experience fully, and production cost is increased, and the control effect is very undesirable.China's coal-burning boiler control is relatively backward with optimisation technique; Energy consumption is high, and control performance is poor, and automaticity is low; Be difficult to adapt to the energy-saving and emission-reduction and the demand of environmental protection indirectly, this wherein directly one of influence factor be the control scheme problem of coal-burning boiler system.

Summary of the invention

Target of the present invention is the weak point to existing coal-burning boiler furnace pressure system control technology; A kind of hybrid control method for furnace pressure system of coal-fired boiler is provided, specifically is based on the mixing control method of prediction proportional integral and PID control.This method has remedied the deficiency of traditional control method, and when guaranteeing that control has higher precision with stability, the form that also guarantees is simple and satisfy the needs of actual industrial process.

The inventive method is at first set up process model based on coal-burning boiler furnace pressure real-time process data, excavates basic process characteristic; Set up the PID control loop based on this process model then; At last through calculating the parameter of predictive PI controller, with PID control and the control of coal-burning boiler furnace pressure object whole implementation predictive PI.

Technical scheme of the present invention is through means such as data acquisition, process identification, prediction mechanism, data-driven, optimizations; The predictive PI of a kind of coal-burning boiler furnace pressure system and the mixing control method of PID control have been established; Utilize this method can effectively improve the precision of control;, satisfy given production performance index simultaneously.

The step of the inventive method comprises:

(1) utilize coal-burning boiler furnace pressure real-time process data to set up process model, concrete grammar is:

At first set up coal-burning boiler furnace pressure real-time running data storehouse, gather N group real-time process service data,, be expressed as { X the sample set of the real-time process service data of gathering as data-driven through data acquisition unit _i, y (i) } _I=1 ^N, i=1,2 ..., N, wherein X _iThe input data of representing i group technological parameter, the output valve of y (i) expression i group technological parameter.

Serve as that the local controlled autoregressive moving average model based on the discrete differential equation form of least square method is set up on the basis with this furnace pressure real-time process service data set then:

y _L(k)＝Φ ^TX，Φ＝[a′ ₁，a′ ₂，…，a′ _n，b′ ₀，b′ ₁，…，b′ _m-1] ^T

X＝[y(k-1)，…，y(k-n)，u(k-d-1)，…，u(k-d-m)] ^T

Wherein, y _L(k) output valve of the technological parameter of expression current time process model, X representes the set of past input and output data constantly of the technological parameter of process model, the corresponding control variables of u (k) expression active procedure model technological parameter; K is current recursion step number; The set of the model parameter that Φ representes to obtain through identification, the transposition of T representing matrix, n; M, d+1 are respectively output variable order, the input variable order of corresponding real process, the time lag of real process.

The identification means that adopt are:

${\mathrm{\Φ}}_k={\mathrm{\Φ}}_{k-1}+\stackrel{\‾}{K}\left(k\right)[y\left(k\right)-{\mathrm{\Φ}}_k^T{X}_k]$

$\stackrel{\‾}{K}\left(k\right)=P(k-1)X_k[X_k^{T}P(k-1)X_k+\mathrm{\γ}{]}^{-1}$

Wherein, K and P are two matrixes in the identification;

γ is a forgetting factor, and

is unit matrix.

(2) adopt typical response curve method to design the proportional plus integral plus derivative controller of furnace pressure process model, concrete grammar is:

A. the proportional plus integral plus derivative controller with process model rests on manual operation state, and the operation dial makes its output have step to change, and by the output valve of recording apparatus recording process model, converts the response curve of process model output valve yL (k) to dimensionless form y _L ^*(k), specifically:

Wherein, y _L(∞) be the output of the proportional plus integral plus derivative controller of the process model process model output y when having step to change _L(k) steady-state value.

B. choose satisfied

Two calculation level k ₁And k ₂,, according to computes proportional plus integral plus derivative controller parameters needed K, T and τ:

K＝y _L(∞)/q

T＝2(k ₁-k ₂)

τ＝2k ₁-k ₂

Wherein, q is the step amplitude of variation of the proportional plus integral plus derivative controller output of process model.

C. the parameter of the proportional plus integral plus derivative controller of computational process model, specifically:

K _c＝1.2T/Kτ

T _i＝2τ

T _d＝0.5τ

K wherein _cBe the scale parameter of proportional plus integral plus derivative controller, T _iBe the integral parameter of proportional plus integral plus derivative controller, T _dBe respectively the differential parameter of proportional plus integral plus derivative controller.

(3) design prediction proportional integral proportional plus integral plus derivative controller, concrete steps are:

D. the proportional plus integral plus derivative controller with process model rests on automatic mode of operation, and the operation dial makes its input have step to change, and by the output of recording apparatus record real-time process, converts the response curve of process output valve y (k) to dimensionless form y ^*(k), specifically: y ^*(k)=y (k)/y (∞)

Wherein, y (∞) is the steady-state value of the input of the proportional plus integral plus derivative controller of the process model process model output y (k) when having step to change.

E. choose and satisfy y (k ₃)=0.39, y (k ₄Two calculation level k in addition of)=0.63 ₃And k ₄, according to computes prediction proportional integral proportional plus integral plus derivative controller parameters needed K ₁, T ₁And τ ₁:

K ₁＝y(∞)/q ₁

T ₁＝2(k ₃-k ₄)

τ ₁＝2k ₃-k ₄

Wherein, q ₁Step amplitude of variation for the input of the proportional plus integral plus derivative controller of process model.

F. the parameter that step e is obtained is converted into the local controlled delivery function model of Laplce's form:

$\frac{y\left(s\right)}{q_1\left(s\right)}=\frac{1}{{\mathrm{\λ}}_{1}s+1}{e}^{-L_{1}s}$

Wherein, s is the Laplace transform operator, λ ₁Be the time constant of local controlled delivery function model, L ₁Be the time lag of local controlled delivery function model, the Laplace transform of the output valve of y (s) expression current time process model, q ₁(s) Laplace transform of the proportional plus integral plus derivative controller input of expression process model.

λ ₁＝T ₁

L ₁＝τ ₁

G. the parameter that the model parameter that calculates according to step f is adjusted prediction proportional integral proportional plus integral plus derivative controller, concrete grammar is:

1. to this object designs prediction pi controller.The closed loop transfer function, model of choosing expectation is G _Q2(s)

$G_{q2}\left(s\right)=\frac{1}{{\mathrm{\λ}}_{2}s+1}{e}^{-L_{2}s}$

λ ₂Be the time constant of closed loop transfer function, model of expectation, L ₂Be the time lag of closed loop transfer function, model of expectation, L ₂=L ₁

2. predict the transfer function G of proportional integral proportional plus integral plus derivative controller _C1(s) can represent by following formula

$G_{c1}\left(s\right)=\frac{{\mathrm{\λ}}_{1}s+1}{({\mathrm{\λ}}_{2}s+1-e^{-L_{2}s})}$

3. 2. obtain current prediction proportional integral proportional plus integral plus derivative controller parameter value u (s) according to step

$u\left(s\right)=\frac{({\mathrm{\λ}}_{2}s+1-e^{-L_{2}s})}{{\mathrm{\λ}}_{1}s+1}y\left(s\right)$

A kind of model based on data-driven that the present invention proposes chooses and predictive PI-PID mixing control method has remedied the deficiency of traditional control, and has made things convenient for the design of controller effectively, guarantees the lifting of control performance, satisfies given production performance index simultaneously.

The control technology that the present invention proposes can effectively reduce the error between desirable furnace pressure technological parameter and the actual furnace pressure process parameter; Further remedied the deficiency of traditional controller; Guarantee that simultaneously control device operates in optimum state, make the furnace pressure technological parameter of production process reach strict control.

The specific embodiment

With the process control of circulating fluidized bed boiler systems furnace pressure is example:

Here describe as an example with the control in this system furnace pressure loop.Furnace pressure not only receives the influence of air mass flow, also receives fuel flow rate, the influence of desuperheating water flow and steam flow simultaneously.Regulating measure adopts into air capacity, and remaining influences as uncertain factor.

(1) sets up the furnace pressure process model of this circulating fluidized bed boiler systems.

Gather real-time process furnace pressure service data through data acquisition unit; With the sample set employing least square method reasoning of the real-time process furnace pressure service data of gathering, set up furnace pressure process model based on the discrete differential equation form of least square method as data-driven.

Wherein, the system call inference machine adopts least square method to carry out the identification of furnace pressure process model parameter, and these parameters comprise the number and concrete numerical value of variable among the element Φ.

${\mathrm{\Φ}}_k={\mathrm{\Φ}}_{k-1}+\stackrel{\‾}{K}\left(k\right)[y\left(k\right)-{\mathrm{\Φ}}_k^T{X}_k]$

$\stackrel{\‾}{K}\left(k\right)=P(k-1)X_k[X_k^{T}P(k-1)X_k+\mathrm{\γ}{]}^{-1}$

Wherein y (k) is the actual furnace pressure measuring value, Φ _k ^TX _kIt is the output valve of furnace pressure process model.

This process is a first step reasoning process.This first step reasoning is the fundamental characteristics that tentatively excavates the actual furnace pressure circuit.

(2) proportional plus integral plus derivative controller of design furnace pressure process model, concrete grammar is typical response curve method.

The first step: the furnace pressure proportional plus integral plus derivative controller is rested on " manual operation " state; The dial that air capacity is advanced in operation makes into air capacity controller output that individual step variation arranged; By the output valve of recording apparatus record furnace pressure process model, with furnace pressure process model output valve y _L(k) response curve converts dimensionless form y to _L ^*(k):

$y_L^{*}\left(k\right)=y_L\left(k\right)/y_L(\∞)$

Wherein, y _L(∞) be furnace pressure process model output y _L(k) steady-state value.

Second step: choose 2 calculation levels,

calculates furnace pressure proportional plus integral plus derivative controller parameters needed T and τ according to following computing formula:

K＝y _L(∞)/q

T＝2(k ₁-k ₂)

τ＝2k ₁-k ₂

Wherein, q is the step amplitude of variation of furnace pressure proportional plus integral plus derivative controller output.

The 3rd step: go on foot the K that calculates, the parameter that T and τ adjust the furnace pressure proportional plus integral plus derivative controller according to second:

K _c＝1.2T/Kτ

T _i＝2τ

T _d＝0.5τ

K wherein _c, T _i, T _dBe respectively the scale parameter of proportional plus integral plus derivative controller, integral parameter, differential parameter.

(3) predictive PI-PID controller of design furnace pressure process, concrete grammar is:

This boiler furnace pressure real time execution process database is set up in basic controlling loop to the furnace pressure proportional plus integral plus derivative controller and the process model of design are formed; Gather furnace pressure real-time process service data through data acquisition unit; Set up predictive PI-required forecast model of PID control according to furnace pressure real-time process service data; Design corresponding furnace pressure real-time process predictive PI-PID controller based on this forecast model, concrete steps are:

The first step: the furnace pressure proportional plus integral plus derivative controller is rested on " operation automatically " state; The input of operation furnace pressure proportional plus integral plus derivative controller makes the input of furnace pressure proportional plus integral plus derivative controller have individual step to change; By the output of recording apparatus record furnace pressure real-time process, convert the response curve of furnace pressure real-time process output valve y (k) to dimensionless form y ^*(k):

y ^*(k)＝y(k)/y(∞)

Wherein, y (∞) is the steady-state value of furnace pressure real-time process output y (k).

Second step: choose 2 calculation levels, y (k ₃)=0.39, y (k ₄Furnace pressure predictive PI-PID controller parameters needed K is calculated according to following computing formula in)=0.63 ₁, T ₁And τ ₁:

K ₁＝y(∞)/q ₁

T ₁＝2(k ₃-k ₄)

τ ₁＝2k ₃-k ₄

Wherein, q ₁Step amplitude of variation for the input of furnace pressure proportional plus integral plus derivative controller.

The 3rd step: go on foot the local controlled delivery function model that the parameter that obtains is converted into Laplce's form with second:

$\frac{y\left(s\right)}{q_1\left(s\right)}=\frac{1}{{\mathrm{\λ}}_{1}s+1}{e}^{-L_{1}s}$

Wherein, the Laplace transform of y (s) expression current time furnace pressure process model output valve, q ₁(s) Laplace transform of the proportional plus integral plus derivative controller input of expression furnace pressure process model.

λ ₁＝T ₁

L ₁＝τ ₁

The 4th step: the parameter that the model parameter that the 3rd step of foundation calculates is adjusted furnace pressure predictive PI-PID controller, concrete grammar is:

1. to this object designs prediction pi controller.The closed loop transfer function, model of choosing expectation is G _Q2(s)

$G_{q2}\left(s\right)=\frac{1}{{\mathrm{\λ}}_{2}s+1}{e}^{-L_{2}s}$

λ ₂Be the time constant of closed loop transfer function, model of expectation, L ₂Be the time lag of closed loop transfer function, model of expectation, L ₂=L ₁

2. predict the transfer function G of proportional integral proportional plus integral plus derivative controller _C1(s) can represent by following formula

$G_{c1}\left(s\right)=\frac{{\mathrm{\λ}}_{1}s+1}{({\mathrm{\λ}}_{2}s+1-e^{-L_{2}s})}$

3. 2. obtain current prediction proportional integral proportional plus integral plus derivative controller parameter value u (s) according to step

$u\left(s\right)=\frac{({\mathrm{\λ}}_{2}s+1-e^{-L_{2}s})}{{\mathrm{\λ}}_{1}s+1}y\left(s\right)$

Claims (1)

1. hybrid control method for furnace pressure system of coal-fired boiler is characterized in that this method may further comprise the steps:

(1) utilize coal-burning boiler furnace pressure real-time process data to set up process model, concrete grammar is:

At first set up coal-burning boiler furnace pressure real-time running data storehouse, gather N group real-time process service data,, be expressed as { x the sample set of the real-time process service data of gathering as data-driven through data acquisition unit _i, y (i) } _I=1 ^N, i=1,2 ..., N, wherein x _iThe input data of representing i group technological parameter, the output valve of y (i) expression i group technological parameter;

Serve as that the local controlled autoregressive moving average model based on the discrete differential equation form of least square method is set up on the basis with this furnace pressure real-time process service data set then:

X＝[y(k-1)，…，y(k-n)，u(k-d-1)，…，u(k-d-m)] ^T

Y wherein _L(k) output valve of the technological parameter of expression current time process model, x representes the set of past input and output data constantly of the technological parameter of process model, the corresponding control variables of u (k) expression active procedure model technological parameter; K is current recursion step number; The set of the model parameter that Φ representes to obtain through identification, the transposition of T representing matrix, n; M, d+1 are respectively output variable order, the input variable order of corresponding real process, the time lag of real process;

The identification means that adopt are:

Wherein k and P are two matrixes in the identification;

γ is a forgetting factor, and

is unit matrix;

(2) adopt typical response curve method to design the proportional plus integral plus derivative controller of furnace pressure process model, concrete grammar is:

A. the proportional plus integral plus derivative controller with process model rests on manual operation state, and the operation dial makes its output have step to change, by the output valve of recording apparatus recording process model, with process model output valve y _L(k) response curve converts dimensionless form y to _L ^*(k), specifically:

Wherein, y _L(∞) be the output of the proportional plus integral plus derivative controller of the process model process model output y when having step to change _L(k) steady-state value;

B. choose satisfied

Two calculation level k ₁And k ₂, according to computes proportional plus integral plus derivative controller parameters needed K, T and τ:

K＝y _L(∞)/q

T＝2(k ₁-k ₂)

τ＝2k ₁-k ₂

Wherein q is the step amplitude of variation of the proportional plus integral plus derivative controller output of process model;

C. the parameter of the proportional plus integral plus derivative controller of computational process model, specifically:

K _c＝1.2T/Kτ

T _i＝2τ

T _d＝0.5τ

K wherein _cBe the scale parameter of proportional plus integral plus derivative controller, T _iBe the integral parameter of proportional plus integral plus derivative controller, T _dBe respectively the differential parameter of proportional plus integral plus derivative controller;

(3) design prediction proportional integral proportional plus integral plus derivative controller, concrete steps are:

D. the proportional plus integral plus derivative controller with process model rests on automatic mode of operation, and the operation dial makes its input have step to change, and by the output of recording apparatus record real-time process, converts the response curve of process output valve y (k) to dimensionless form y ^*(k), specifically: y ^*(k)=y (k)/y (∞)

Wherein, y (∞) is the steady-state value of the input of the proportional plus integral plus derivative controller of the process model process model output y (k) when having step to change;

E. choose and satisfy y (k ₃)=0.39, y (k ₄Two calculation level k in addition of)=0.63 ₃And k ₄, according to computes prediction proportional integral proportional plus integral plus derivative controller parameters needed K ₁, T ₁And τ ₁:

K ₁＝y(∞)/q ₁

T ₁＝2(k ₃-k ₄)

τ ₁＝2k ₃-k ₄

Q wherein ₁Step amplitude of variation for the input of the proportional plus integral plus derivative controller of process model;

F. the parameter that step e is obtained is converted into the local controlled delivery function model of Laplce's form:

Wherein s is the Laplace transform operator, λ ₁Be the time constant of local controlled delivery function model, L ₁Be the time lag of local controlled delivery function model, the Laplace transform of the output valve of y (s) expression current time process model, q ₁(s) Laplace transform of the proportional plus integral plus derivative controller input of expression process model;

λ ₁＝T ₁

L ₁＝τ ₁

G. the parameter that the model parameter that calculates according to step f is adjusted prediction proportional integral proportional plus integral plus derivative controller, concrete grammar is:

1. to this object designs prediction pi controller; The closed loop transfer function, model of choosing expectation is G _Q2(s)

λ ₂Be the time constant of closed loop transfer function, model of expectation, L ₂Be the time lag of closed loop transfer function, model of expectation, L ₂=L ₁

2. predict the transfer function G of proportional integral proportional plus integral plus derivative controller _C1(s) can represent by following formula

3. 2. obtain current prediction proportional integral proportional plus integral plus derivative controller parameter value u (s) according to step

。