CN105299612A - Main steam temperature control method based on multi-model switching and control system - Google Patents

Abstract

The invention discloses a main steam temperature control method based on multi-model switching and a control system. The control method and the control system are used for controlling the main steam temperature of a power station boiler. According to the method, switching strategies are used according to changes of the operation load of the boiler, a control model of the typical operation load operating point closest to practical situations is selected to control the water spraying quantity of a temperature reduction device, and temperature control is achieved. According to the control method and the control system, the accuracy is high, response is quick, and implementation is simple and convenient; the problem that controller parameters are not matched with control models in the operation process of a thermal power generating unit can be effectively solved through the main steam temperature control method used for the power station boiler through multi-model switching based on the proportion integration differentiation (PID) algorithm.

Description

Based on Main Steam Temperature Control method and the control system of multi-model switching

Technical field

The present invention relates to station boiler Main Steam Temperature Control method, especially relate to a kind of Main Steam Temperature Control method based on multi-model switching, be applicable to Thermal generation unit, belong to automatic control technology field.

Background technology

Large-sized station boiler Main Steam Temperature Control is increased economic efficiency, ensures the indispensable link of unit safety operation.Be very strict to the control overflow of Boiler Steam Temperature, steam temperature is too high or too low, and significantly fluctuates and all will affect boiler, the safety of steam turbine and economy.Therefore the stable operation maintaining Boiler Steam Temperature is very important.Superheater is generally made up of some levels, and pipe at different levels often uses different materials, maximum permissible temperature corresponding certain respectively.Therefore for ensureing metallic airbag, also the steam temperature that heating surface at different levels exports should be limited, in addition, also should be prevented the local quick-fried leakage of overtemperature of pipe and the inequality of being heated of steam turbine both sides.If vapor (steam) temperature is too high, exceedes the permission operating temperature of part of appliance (as superheater tube, jet chimney, nozzle of steam turbine, blade etc.), steel tertiary creep will have been made, reduce service life.Serious superhigh temperature even can make pipe overheated and explosion.Vapor (steam) temperature is too low, will reduce heat power equipment economy, increases gross coal consumption rate.Steam temperature is too low, steam turbine what steam moisture last also can be made to increase, aggravate, water slug will occur time serious, the safety of threat steam turbine to the corrosion function of blade.And the steam temperature bust that jumps also can make boiler each heating surface weld bond and coupling part produce larger thermal stress, causes swollen difference to increase.The sound friction between impeller and dividing plate even may be there is, steam turbine high vibration etc. time serious.

Main steam temperature generally can regard many appearance distributed constant controll plants as, more difficult to the control of this object.Its reason mainly contains: (1), Combustion Operation of Boilers are unstable, and fume side disturbance is frequent and disturbance quantity is comparatively large, affects main steam temperature change very fast; (2), due to operational characteristic, to determine superheater pipeline at different levels longer, causes Stream temperature to its regulating measure, and namely the reaction of the spray water flux change of direct-contact desuperheater is comparatively slow, shows obvious hysteresis characteristic; (3) external disturbance (as main steam flow fluctuation, main steam pressure fluctuation etc.) change is frequent and disturbance quantity is comparatively large, causes Stream temperature often to fluctuate; (4) internal disturbance (as the attemperation water flow fluctuation that main feedwater flow fluctuation, feed pressure fluctuation etc. cause), makes injection flow rate change, still often departs from setting value when causing Stream temperature to disturb less outside; (5) fresh steam temperature has obvious time-varying characteristics for the change of unit load.

Dynamic characteristic and the operating condition of thermal object are closely related, and the plant characteristic of unit is along with unit load change generation significant change, particularly even more serious for regulating units phenomenon.For Stream temperature object, its dynamic characteristic, by operating condition parameter (main steam flow, main steam pressure and main steam temperature) variable effect, causes model parameter generation significant change.Due to unit load variable effect coal supply amount, thus directly affect superheater heat absorption, steam turbine side load variations also can cause steam flow to change simultaneously, and therefore load variations can cause steam flow disturbance, superheater caloric receptivity disturbance and the disturbance of superheater entrance steam temperature.Usually, when load increases, the delayed of system performance function and inertia time constant and static gain can be caused all to present the trend of obviously reduction, total steam temperature then increase with load rising.

Therefore, when the operating load of boiler changes time, continue to use initial conventional PID controllers state modulator boiler operatiopn model that control effects will be caused to be deteriorated, even cause the instability of control system.Therefore, need for the corresponding controller of the modelling under each operating mode, to ensure best control effects.

Summary of the invention

In order to solve the defect existed in prior art, the invention provides a kind of Main Steam Temperature Control method based on multi-model switching and control system, to solve station boiler unit running process middle controller parameter and the unmatched problem of Controlling model.Technical scheme is as follows:

A kind of Main Steam Temperature Control method based on multi-model switching, operating load change according to boiler uses switchover policy, select the Controlling model of the typical operating load operating point the most close with actual conditions to control the injection flow rate of Desuperheating device, realize temperature and control, concrete steps are as follows:

Step one: go out N number of typical operating load operating point, wherein N >=2 according to the maximum operating load of station boiler unit and main operating load interval division;

Step 2: the actual operating data gathering typical operating load operating point, adopts cas PID control method, sets up the Main Steam Temperature Control model at typical operating load operating point place;

Step 3: optimize the pid control parameter at representative row load condition point place, set up the optimum Main Steam Temperature Control model at typical operating load operating point place, makes each typical operating load operating point have one group of adjustable controling parameters corresponding with it;

Step 4: carry out strategy according to multi-model switching index and switch, recycling PID control method, obtains desuperheater spray amount J;

Described multi-model switching index is the difference degree between to be switched control procedure and optimum Main Steam Temperature Control model;

Described tactful handoff procedure adopts delayed switching method;

Described PID control method adopts incremental PID control method.

In described step 4, the preparation method of multi-model switching index is as follows:

$J_i={\mathrm{\αe}}_i\left(k\right)+\mathrm{\β}\underset{j=1}{\overset{L}{\Σ}}{\mathrm{\ρ}}^{(k-j)}{e}_i(k-j),i=1,2,\mathrm{......},N$

Wherein, e _i(k)=y (k)-y _i(k), i.e. e _ik () exports the error amount in the kth moment for the output of process and i-th optimum Main Steam Temperature Control model; α, β are weights, represent respectively current time and last time the output of process and model export between difference on the impact switching index; N is the number of optimum Main Steam Temperature Control model; L is the length that impact switches the error of index; ρ is the memory effect to error; J _ifor the difference degree between control procedure and i-th optimum Main Steam Temperature Control model, namely switch index, value is less represent between control procedure and i-th optimum Main Steam Temperature Control model more close;

In described step 4, tactful handoff procedure is as follows:

According to delayed switching method,

J _i(k)＝min{J _i(k)},i＝1,2....,N

Wherein i is the optimum Main Steam Temperature Control model sequence number of current use, and j is minimum with the switching index of i corresponding optimum Main Steam Temperature Control model sequence number, if now i ≠ j, judges the necessity switched, if

J _j(k)+ρ＜J _i(k)

Then be switched to a jth optimum Main Steam Temperature Control model, otherwise still use i-th optimum Main Steam Temperature Control model, wherein ρ is hysteresis factors;

In described step 4, incremental PID control method is as follows:

$u\left(k\right)=K_p\{e_k+\frac{T}{T_I}\underset{j=0}{\overset{k}{\Σ}}e\left(j\right)+\frac{T}{T_d}\[e_k-e_{k-1}\]\}$

$u(k-1)=K_p\[e_{k-1}+\frac{T}{T_I}\underset{j=0}{\overset{k}{\Σ}}e\left(j\right)+\frac{T}{T_D}(e_{k-1}-e_{k-2})\]$

Deduct u (k-1) with u (k), can obtain

$\begin{array}{c}\mathrm{\Δ}u\left(k\right)=K_p\[e_k-e_{k-1}+\frac{T}{T_I}{e}_k+\frac{T}{T_d}(e_k-2e_{k-1}+e_{k-2})\]\\ =K_P\[(1+\frac{T}{T_I}+\frac{T_D}{T})e_k+(1+2\frac{T_D}{T})e_{k-1}+\frac{T_D}{T}{e}_{k-2}\]\end{array}$

Wherein K _pfor proportionality coefficient, u (k) for k moment PID calculated value, T be system communication cycle, T _ifor integration time constant, T _dderivative time constant, e _kfor the error amount of k moment desired value and output temperature, e _k-1for k-1 moment desired value and output temperature error amount, e _k-2for k-2 moment desired value and output temperature error amount; U (k-1) is k-1 moment PID calculated value; Desuperheater spray amount computational process is as follows as from the foregoing:

$J_k=J_{k-1}+\mathrm{\Δ}J=J_{k-1}+K_P\[(1+\frac{T}{T_I}+\frac{T_D}{T})e_k+(1+2\frac{T_D}{T})e_{k-1}+\frac{T_D}{T}{e}_{k-2}\]$

Wherein J _kfor k moment desuperheater spray amount, J _k-1for k-1 moment desuperheater spray amount, K _pfor proportionality coefficient, T is system communication cycle, T _ifor integration time constant, T _dfor derivative time constant, e _kfor the error amount of k moment desired value and output temperature; e _k-1for k-1 moment desired value and output temperature error amount, e _k-2for k-2 moment desired value and output temperature error amount;

Obtain desuperheater spray amount J based on said method, realize the Main Steam Temperature Control of multi-model switching.

Adopt a kind of control system of the Main Steam Temperature Control method based on multi-model switching, comprise multi-model switching control module, traditional cas PID control module, optimize cas PID control module and addition and subtraction computing module, described traditional cas PID control module is arranged with optimization cas PID control wired in parallel, and input is all connected with multi-model switching control module, output is connected with addition and subtraction computing module, and described addition and subtraction computing module output is connected with multi-model switching control module input;

Described traditional cas PID control module is divided into inside and outside two loops, and external loop is the PI control loop that proportional+integral controls, and inner looping is the pid control circuit of proportional+integral+differential, and through traditional cas PID control module output is main steam temperature;

The actual operating data of the N number of typical operating load operating point in the maximum operating load of described optimization cas PID control module acquires station boiler unit and main operating load interval, and adopt cas PID control method, setting up the Main Steam Temperature Control model at typical operating load operating point place, obtaining optimum Main Steam Temperature Control model through optimizing;

Described addition and subtraction computing module subtracts exporting next main steam temperature through traditional cas PID control module and exporting through optimum Main Steam Temperature Control model each best main steam temperature come, and result is input in multi-model switching control module;

Described multi-model switching control module is according to the result inputted through addition and subtraction computing module, and obtain multi-model switching index and carry out strategy switching, recycling PID control method, obtains desuperheater spray amount.

Compared with prior art, beneficial effect of the present invention is:

Control method provided by the present invention and the control system degree of accuracy is high, reaction fast, simple and easy to do, based on the multi-model switching station boiler Main Steam Temperature Control method of pid algorithm, thermal power unit operation process middle controller parameter and the unmatched problem of Controlling model effectively can be solved.

Accompanying drawing explanation

Fig. 1 is Control system architecture schematic diagram of the present invention.

Detailed description of the invention

In order to further illustrate technical scheme of the present invention, in conjunction with Figure of description, technical scheme of the present invention is as follows:

The present invention discloses a kind of Main Steam Temperature Control method based on multi-model switching, operating load change according to boiler uses switchover policy, the Controlling model of the typical operating load operating point the most close with actual conditions is selected to control the injection flow rate of Desuperheating device, realize temperature to control, concrete steps are as follows:

Step one: go out N number of typical operating load operating point according to the maximum operating load design capacity of station boiler unit and main operating load interval division, each typical operating load operating point represents a load value; The value of N is not less than 2, and described in as N=2,2 typical operating point are respectively boiler minimum load operating point X _min, specified peak load operating point X _max; As N>2, described N number of typical operating point is respectively boiler minimum load operating point X _min, specified peak load operating point XX _max, and above-mentioned two operating points between (N 1) individual typical operating point of marking off.

As shown in Figure 1, in the present embodiment, be divided into 5 typical operating loads according to boiler day-to-day operation operating mode, be respectively 30% load, 44% load, 62% load, 88% load, 100% load.

Step 2: utilize boiler DCS control system to gather the actual operating data of typical operating load operating point, utilize recognition software, adopts cas PID control method, sets up the Main Steam Temperature Control model at typical operating load operating point place;

Cas PID control system is divided into inside and outside two loops, and external loop is that proportional+integral control and PI control, and inner looping is that proportional+integral+differential and PID control.

General leading district Mathematical Modeling is one order inertia equivalent model:

$G_1^n\left(s\right)=\frac{y_1\left(s\right)}{y_2\left(s\right)}=\frac{K_1^n}{T^{n}s+1}{e}^{-ns},(n=1,2,3,4......)$

Inertia district is that one order inertia adds pure delay model:

$G_2^n\left(s\right)=\frac{y_2\left(s\right)}{u\left(s\right)}=\frac{K_2^n}{T_2^{n}s+1},(n=1,2,3,\mathrm{4.......})$

Y ₁s () is desuperheater spray amount, y ₂(s) for main steam temperature, u (s) after attemperator be main steam temperature;

G ₁(s), G ₂s () is external loop and inner looping transfer function respectively.

Step 3: utilize parameter optimization software to calculate the optimal value of the pid control parameter at typical operating load operating point place, set up the optimum Main Steam Temperature Control model at typical operating load operating point place, make each typical operating load operating point have one group of adjustable controling parameters corresponding with it;

Step 4: carry out strategy according to multi-model switching index and switch, recycling PID control method, writes Multiple model control changeover program and is write in DCS control system, final acquisition desuperheater spray amount J;

Described multi-model switching index is the difference degree between to be switched control procedure and optimum Main Steam Temperature Control model;

The preparation method of multi-model switching index is as follows:

$J_i={\mathrm{\αe}}_i\left(k\right)+\mathrm{\β}\underset{j=1}{\overset{L}{\Σ}}{\mathrm{\ρ}}^{(k-j)}{e}_i(k-j),i=1,2,\mathrm{......},N$

Wherein, e _i(k)=y (k)-y _i(k), i.e. e _ik () exports the error amount in the kth moment for the output of process and i-th optimum Main Steam Temperature Control model; α, β are weights, represent respectively current time and last time the output of process and model export between difference on the impact switching index; N is the number of optimum Main Steam Temperature Control model; L is the length that impact switches the error of index; ρ is the memory effect to error; J _ifor the difference degree between control procedure and i-th optimum Main Steam Temperature Control model, namely switch index, value is less represent between control procedure and i-th optimum Main Steam Temperature Control model more close;

Described tactful handoff procedure adopts delayed switching method;

Strategy handoff procedure is as follows:

According to delayed switching method,

J _i(k)＝min{J _i(k)},i＝1,2....,N

Wherein i is the optimum Main Steam Temperature Control model sequence number of current use, and j is minimum with the switching index of i corresponding optimum Main Steam Temperature Control model sequence number, if now i ≠ j, judges the necessity switched, if

J _j(k)+ρ＜J _i(k)

Then be switched to a jth optimum Main Steam Temperature Control model, otherwise still use i-th optimum Main Steam Temperature Control model, wherein ρ is hysteresis factors;

Described PID control method adopts incremental PID control method; Incremental PID control method is as follows:

$u\left(k\right)=K_p\{e_k+\frac{T}{T_I}\underset{j=0}{\overset{k}{\Σ}}e\left(j\right)+\frac{T}{T_d}\[e_k-e_{k-1}\]\}$

$u(k-1)=K_p\[e_{k-1}+\frac{T}{T_I}\underset{j=0}{\overset{k}{\Σ}}e\left(j\right)+\frac{T}{T_D}(e_{k-1}-e_{k-2})\]$

Deduct u (k-1) with u (k), can obtain

$\begin{array}{c}\mathrm{\Δ}u\left(k\right)=K_p\[e_k-e_{k-1}+\frac{T}{T_I}{e}_k+\frac{T}{T_d}(e_k-2e_{k-1}+e_{k-2})\]\\ =K_P\[(1+\frac{T}{T_I}+\frac{T_D}{T})e_k+(1+2\frac{T_D}{T})e_{k-1}+\frac{T_D}{T}{e}_{k-2}\]\end{array}$

Wherein K _pfor proportionality coefficient, u (k) for k moment PID calculated value, T be system communication cycle, T _ifor integration time constant, T _dderivative time constant, e _kfor the error amount of k moment desired value and output temperature, e _k-1for k-1 moment desired value and output temperature error amount, e _k-2for k-2 moment desired value and output temperature error amount; U (k-1) is k-1 moment PID calculated value; Desuperheater spray amount computational process is as follows as from the foregoing:

$J_k=J_{k-1}+\mathrm{\Δ}J=J_{k-1}+K_P\[(1+\frac{T}{T_I}+\frac{T_D}{T})e_k+(1+2\frac{T_D}{T})e_{k-1}+\frac{T_D}{T}{e}_{k-2}\]$

Wherein J _kfor k moment desuperheater spray amount, J _k-1for k-1 moment desuperheater spray amount, K _pfor proportionality coefficient, T is system communication cycle, T _ifor integration time constant, T _dfor derivative time constant, e _kfor the error amount of k moment desired value and output temperature; e _k-1for k-1 moment desired value and output temperature error amount, e _k-2for k-2 moment desired value and output temperature error amount.

Write the multi-model switching program based on pid algorithm based on said method, final acquisition desuperheater spray amount J, realizes the Main Steam Temperature Control of multi-model switching.

As shown in Figure 1, the invention also discloses the control system adopting above-mentioned control method, this system comprises multi-model switching control module, traditional cas PID control module, optimizes cas PID control module and addition and subtraction computing module, described traditional cas PID control module is arranged with optimization cas PID control wired in parallel, and input is all connected with multi-model switching control module, output is connected with addition and subtraction computing module, and described addition and subtraction computing module output is connected with multi-model switching control module input;

Described traditional cas PID control module is divided into inside and outside two loops, and external loop is the PI control loop that proportional+integral controls, and inner looping is the pid control circuit of proportional+integral+differential, and through traditional cas PID control module output is main steam temperature;

The actual operating data of the N number of typical operating load operating point in the maximum operating load of described optimization cas PID control module acquires station boiler unit and main operating load interval, and adopt cas PID control method, setting up the Main Steam Temperature Control model at typical operating load operating point place, obtaining optimum Main Steam Temperature Control model through optimizing; According to boiler day-to-day operation operating mode, described optimization cas PID control module is divided into 5 typical operating load Controlling model in the present embodiment, is respectively 30% load model, 44% load model, 62% load model, 88% load model, 100% load model.

Described addition and subtraction computing module subtracts exporting next main steam temperature through traditional cas PID control module and exporting through optimum Main Steam Temperature Control model each best main steam temperature come, and result is input in multi-model switching control module;

Described multi-model switching control module is according to the result inputted through addition and subtraction computing module, and obtain multi-model switching index and carry out strategy switching, recycling PID control method, obtains desuperheater spray amount.

Claims (5)

1. the Main Steam Temperature Control method based on multi-model switching, it is characterized in that: described control method uses switchover policy according to the operating load change of boiler, the Controlling model of the typical operating load operating point the most close with actual conditions is selected to control the injection flow rate of Desuperheating device, realize temperature to control, concrete steps are as follows:

Step one: go out N number of typical operating load operating point, wherein N >=2 according to the maximum operating load of station boiler unit and main operating load interval division;

Step 2: the actual operating data gathering typical operating load operating point, adopts cas PID control method, sets up the Main Steam Temperature Control model at typical operating load operating point place;

Step 3: optimize the pid control parameter at representative row load condition point place, set up the optimum Main Steam Temperature Control model at typical operating load operating point place, makes each typical operating load operating point have one group of adjustable controling parameters corresponding with it;

Step 4: carry out strategy according to multi-model switching index and switch, recycling PID control method, obtains desuperheater spray amount J;

Described multi-model switching index is the difference degree between to be switched control procedure and optimum Main Steam Temperature Control model;

Described tactful handoff procedure adopts delayed switching method;

Described PID control method adopts incremental PID control method.

2. a kind of Main Steam Temperature Control method based on multi-model switching as claimed in claim 1, is characterized in that:

In described step 4, the preparation method of multi-model switching index is as follows:

Wherein, e _i(k)=y (k)-y _i(k), i.e. e _ik () exports the error amount in the kth moment for the output of process and i-th optimum Main Steam Temperature Control model; α, β are weights, represent respectively current time and last time the output of process and model export between difference on the impact switching index; N is the number of optimum Main Steam Temperature Control model; L is the length that impact switches the error of index; ρ is the memory effect to error; J _ifor the difference degree between control procedure and i-th optimum Main Steam Temperature Control model, namely switch index, value is less represent between control procedure and i-th optimum Main Steam Temperature Control model more close.

3. a kind of Main Steam Temperature Control method based on multi-model switching as claimed in claim 1, is characterized in that:

In described step 4, tactful handoff procedure is as follows:

According to delayed switching method,

J _i(k)＝min{J _i(k)},i＝1,2....,N

Wherein i is the optimum Main Steam Temperature Control model sequence number of current use, and j is minimum with the switching index of i corresponding optimum Main Steam Temperature Control model sequence number, if now i ≠ j, judges the necessity switched, if

J _j(k)+ρ＜J _i(k)

Then be switched to a jth optimum Main Steam Temperature Control model, otherwise still use i-th optimum Main Steam Temperature Control model, wherein ρ is hysteresis factors.

4. a kind of Main Steam Temperature Control method based on multi-model switching as claimed in claim 1, is characterized in that:

In described step 4, incremental PID control method is as follows:

Deduct u (k-1) with u (k), can obtain

Wherein K _pfor proportionality coefficient, u (k) for k moment PID calculated value, T be system communication cycle, T _ifor integration time constant, T _dderivative time constant, e _kfor the error amount of k moment desired value and output temperature, e _k-1for k-1 moment desired value and output temperature error amount, e _k-2for k-2 moment desired value and output temperature error amount; U (k-1) is k-1 moment PID calculated value; Desuperheater spray amount computational process is as follows as from the foregoing:

Wherein J _kfor k moment desuperheater spray amount, J _k-1for k-1 moment desuperheater spray amount, K _pfor proportionality coefficient, T is system communication cycle, T _ifor integration time constant, T _dfor derivative time constant, e _kfor the error amount of k moment desired value and output temperature; e _k-1for k-1 moment desired value and output temperature error amount, e _k-2for k-2 moment desired value and output temperature error amount;

Obtain desuperheater spray amount J based on said method, realize the Main Steam Temperature Control of multi-model switching.

5. adopt the control system of a kind of Main Steam Temperature Control method based on multi-model switching as claimed in claim 1, it is characterized in that: comprise multi-model switching control module, traditional cas PID control module, optimize cas PID control module and addition and subtraction computing module, described traditional cas PID control module is arranged with optimization cas PID control wired in parallel, and input is all connected with multi-model switching control module, output is connected with addition and subtraction computing module, and described addition and subtraction computing module output is connected with multi-model switching control module input;

Described traditional cas PID control module is divided into inside and outside two loops, and external loop is the PI control loop that proportional+integral controls, and inner looping is the pid control circuit of proportional+integral+differential, and through traditional cas PID control module output is main steam temperature;

The actual operating data of the N number of typical operating load operating point in the maximum operating load of described optimization cas PID control module acquires station boiler unit and main operating load interval, and adopt cas PID control method, setting up the Main Steam Temperature Control model at typical operating load operating point place, obtaining optimum Main Steam Temperature Control model through optimizing;

Described addition and subtraction computing module subtracts exporting next main steam temperature through traditional cas PID control module and exporting through optimum Main Steam Temperature Control model each best main steam temperature come, and result is input in multi-model switching control module;

Described multi-model switching control module is according to the result inputted through addition and subtraction computing module, and obtain multi-model switching index and carry out strategy switching, recycling PID control method, obtains desuperheater spray amount.