CN104503502A - Modified Smith prediction main stream temperature control structure - Google Patents

Abstract

The invention provides a modified Smith prediction main stream temperature control structure. The modified Smith main stream temperature control prediction structure is characterized by a system transfer function. The another technical scheme includes that a novel Smith predictor is added, and a modified Smith main stream temperature prediction structure is provided and characterized by a system transfer function. The modified Smith prediction main stream temperature control structure has the advantages that the function transferring manner that the one-order inertia adds the delay link of the conventional Smith predictor is replaced by the high-order system, allowing the prediction system stable, thus dynamic deviation of the system is decreased and engineering application is convenient.

Description

A kind of modified Smith estimates main-stream control structure

Technical field

The present invention relates to the main-stream control structure of a kind of fuel-burning power plant super-critical and ultra super-critical power unit.

Background technology

Along with the development of China's electric utility, the jumbo unit of China constantly increases, and the automaticity of electrical network there has also been very large raising, and this just has higher requirement to unit allocation quality.Wherein main steam temperature is the important parameter being related to Unit Economic safe operation.Require during unit operation that Stream temperature changes near setting value, can not have excessive deviation.Conventional main-stream control scheme is generally cas PID control scheme, the features such as stability is high, structure is simple because PID controls to have, easy to adjust, highly versatile, so its status in power plant's control is difficult to replace.But along with the development of the present computer technology and modern control theory, Advanced Control Techniques becomes the focus of research both at home and abroad.Wherein for this Large-lag System of Stream temperature, a kind of model can be dreamed up according to process characteristic and join in feedback control system, be used for the dynamic perfromance of delay of bucking-out system.Dynamic matrix control scheme generally concentrates on several aspects such as ANN (Artificial Neural Network) Control, fuzzy control, PREDICTIVE CONTROL and Smith Prediction Control.Although the appearance proposing advanced control algolithm and the theory of control compensates the characteristic of steam temperature large time delay, applying to not be a lot of in reality.Smith Prediction Control is the typical control program of one for the large delay of Stream temperature, and it is simple relative to design concept other advanced control systems, and it is also relatively easy to implement, and is convenient to engineer applied.

Summary of the invention

The object of this invention is to provide a kind of can at the Smith Prediction Control algorithm of main-stream control.

In order to achieve the above object, a technical scheme of the present invention there is provided a kind of modified Smith and estimates main-stream control structure, and it is characterized in that, ssystem transfer function is in formula, X (s) is input, and Y (s) is output, G ₀s () is controlled device k is amplification coefficient, and T is time constant, and system features equation is: g _c1s () is controller.

Another technical scheme of the present invention adds novel SMITH prediction device, and provide a kind of modified Smith and estimate main-stream control structure, it is characterized in that, ssystem transfer function is in formula, X (s) is input, and Y (s) is output, G ₀s () is controlled device, k is amplification coefficient, and T is time constant, G ₀ ^*s Controlling model that () is estimated for Smith, ${G_0}^{*}\left(s\right)=\frac{K}{(1+T_{2}s)},$ T ₂＝nT。

The invention provides a kind of New type of S mith and estimate structure, traditional Smith prediction device is required that transport function is that one order inertia adds that the form of delay link changes into high order system, and its advantage is:

Adopt depression of order lmproved Smith Estimator that Prediction System can be made more stable, be conducive to the dynamic deviation of minimizing system.For first order inertial loop, traditional prediction device then controlled device must add that delay link then realizes than being easier to.If the model that Stream temperature model is set up is high order system, then use traditional prediction device, by the time of the transformation model of at substantial.The secular equation of the system after traditional Smith estimates is 1+G _c(s) G _o(s), wherein delay link is eliminated for original system.The present invention proposes another kind of follow-on prediction device, estimates rear secular equation to be eliminate delay link equally, but secular equation does not change, do not change system performance, facilitate engineer applied.

Accompanying drawing explanation

Fig. 1 is traditional SMITH prediction device illustraton of model;

Fig. 2 is control structure schematic diagram of the present invention.

Embodiment

For making the present invention become apparent, hereby with preferred embodiment, and accompanying drawing is coordinated to be described in detail below.

In main stream temperature, the output of temperature controller forms the setting value of desuperheating water spray flow controller.Between the temperature in of three-stagesuperheater and outlet temperature, the steam in pipeline and tube wall are connected by multiple single appearance object to form multi capacity object, so controlled device has the characteristic of large time delay.

The cardinal principle of Smith prediction device is pre-estimate out the dynamic perfromance of controlled process under certain disturbance, then by Smith prediction device, it is compensated in advance, make regulated variable leading reflection that time delay is to controller, make controller advancement, thus reduce the overshoot of system and reduce regulating time.

The prerequisite that Simth Prediction Control structure can realize good effect be Controlling model there is higher accuracy.It is very responsive to model error, and compensation result depends on the precision of compensator model.But the main temperature Controlling model of power plant is a fuzzy model.The object of this invention is to provide a kind of modified Smith and estimate structure, under the prerequisite not changing plant characteristic, reduce prediction device to the dependence of control object model accuracy, not only facilitate theoretical research, also facilitate engineer applied.

As shown in Figure 1, after adding Smith prediction device, system closed loop transfer function, is:

$\frac{Y\left(s\right)}{X\left(s\right)}=\frac{G_0\left(s\right)G_{c1}\left(s\right)}{1+G_0\left(s\right)G_{c1}\left(s\right)}{e}^{{-\mathrm{\τ}}_{0}s}$

In formula, X (s) is input, and Y (s) is output, τ ₀for delay time, G _c1s () is controller, k is amplification coefficient.System features equation does not comprise that is, Smith Prediction System has eliminated the impact of the direct purely retarded of X (s) and Y (s) for closed-loop system, and in molecule just the response time of controlled parameter Y (s) is postponed τ ₀this time period.

As shown in Figure 2:

A kind of novel SMITH Prediction Control system provided by the invention, if do not add Prediction Control, ssystem transfer function is: $\frac{Y\left(s\right)}{X\left(s\right)}=\frac{G_0\left(s\right)G_{c1}\left(s\right)}{1+G_0\left(s\right)G_{c1}\left(s\right)},$ In formula, $G_0\left(s\right)=\frac{K}{{(1+\mathrm{Ts})}^n},$ K is amplification coefficient, and T is time constant.System features equation is: for large time-delay system.

If add novel SMITH prediction device, ssystem transfer function is: in formula, $G_0\left(s\right)=\frac{K}{{(1+\mathrm{Ts})}^n},$ G ₀ ^*s Controlling model that () is estimated for Smith, ${G_0}^{*}\left(s\right)=\frac{K}{(1+T_{2}s)},$ T ₂＝nT。Convert first order inertial loop to by large delay link like this, be conducive to the hysteresis quality of bucking-out system, system is responded fast.

Claims (2)

1. modified Smith estimates a main-stream control structure, it is characterized in that, ssystem transfer function is in formula, X (s) is input, and Y (s) is output, G ₀s () is controlled device k is amplification coefficient, and T is time constant, and system features equation is: g _c1s () is controller.

2. modified Smith estimates a main-stream control structure, it is characterized in that, ssystem transfer function is in formula, X (s) is input, and Y (s) is output, G ₀s () is controlled device, k is amplification coefficient, and T is time constant, G ₀ ^*s Controlling model that () is estimated for Smith, ${G_0}^{*}\left(s\right)=\frac{K}{(1+T_{2}s)},T_2=\mathrm{nT}.$