超臨界機(jī)組燃料—汽壓系統(tǒng)建模與控制策略研究
發(fā)布時間：2018-08-22 14:34
【摘要】：當(dāng)今社會能源與環(huán)境問題日益突出,超臨界機(jī)組由于具有效率高、能耗低等特點,日益成為火電廠裝機(jī)的趨勢。超臨界機(jī)組的燃燒控制系統(tǒng)是整個控制系統(tǒng)的重要組成部分,目前大多數(shù)火電廠燃煤來源廣、熱值偏差大,嚴(yán)重影響了燃燒系統(tǒng)的控制,其控制水平又進(jìn)一步影響到整個機(jī)組控制的安全性與經(jīng)濟(jì)性。因此,在燃煤煤種多變的情況下,研究一種適用于超臨界機(jī)組的煤質(zhì)自適應(yīng)控制策略,提高機(jī)組運行的安全性與經(jīng)濟(jì)性,優(yōu)化超臨界機(jī)組的控制系統(tǒng),成為亟待解決的問題。設(shè)計了自適應(yīng)煤質(zhì)前饋校正,以功煤系數(shù)為出發(fā)點,借助組合預(yù)測模型的思想建立一個對入爐煤量的預(yù)測模型,采用方差倒數(shù)法求取前1小時功煤系數(shù)對當(dāng)前時刻功煤系數(shù)的最優(yōu)權(quán)重,實現(xiàn)對入爐煤功煤系數(shù)以及入爐煤煤量的預(yù)測。用入爐煤量的預(yù)測模型對某660MW機(jī)組#4鍋爐入爐煤量進(jìn)行預(yù)測,結(jié)果表明,用實時入爐煤量的預(yù)測值作為實際給煤量,其準(zhǔn)確度能達(dá)到97.0%左右,提高了入爐煤量的準(zhǔn)確性。主蒸汽壓力是表征超臨界機(jī)組機(jī)爐能量供求關(guān)系的重要參數(shù),其主要影響因素為燃料量。目前大部分火電廠燃料煤種雜、熱值波動大,造成主蒸汽壓力波動頻繁,嚴(yán)重影響機(jī)組的安全運行。在燃料量的前饋控制系統(tǒng)的基礎(chǔ)上,設(shè)計了二階自抗擾控制器,在燃料量的反饋控制系統(tǒng)中用自抗擾控制代替?zhèn)鹘y(tǒng)的PID進(jìn)行閉環(huán)反饋控制,主要是借助擴(kuò)張狀態(tài)觀測器估計出燃煤熱值自發(fā)擾動,并在動態(tài)過程中將其實時補(bǔ)償,進(jìn)一步提高入爐煤量的準(zhǔn)確性,防止因燃煤熱值波動造成主蒸汽壓力的頻繁波動。采用壓力節(jié)點的方法將超臨界直流鍋爐動態(tài)數(shù)學(xué)模型分為3個壓力節(jié)點,對每個壓力節(jié)點列出質(zhì)量守恒與能量守恒方程,然后對方程進(jìn)行化簡、無量綱化,最后將3個壓力節(jié)點串聯(lián)即可得到超臨界機(jī)組燃料 汽壓系統(tǒng)模型。利用某660MW超臨界機(jī)組設(shè)計數(shù)據(jù)進(jìn)行建模、計算,得出超臨界機(jī)組燃料 汽壓系統(tǒng)在100%THA、75%THA、50%THA工況下的模型計算參數(shù)。在三種工況下,對求得的模型分別進(jìn)行傳統(tǒng)的PID控制與自抗擾控制仿真,結(jié)果表明:與傳統(tǒng)PID控制相比,自抗擾控制的抗干擾能力更強(qiáng),具有更好的魯棒性,對主蒸汽壓力有更好的控制品質(zhì)。通過比較傳統(tǒng)PID控制器和自抗擾控制器控制效果可知,具有消除擾動效果的自抗擾控制方案是具有前景的控制方案。
[Abstract]:Nowadays, the problems of energy and environment are becoming more and more serious. Because of its high efficiency and low energy consumption, supercritical units are becoming the trend of power plant installation. The combustion control system of supercritical unit is an important part of the whole control system. At present, most thermal power plants have wide sources of coal combustion and large deviation of calorific value, which seriously affects the control of combustion system. Its control level further affects the safety and economy of the whole unit control. Therefore, it is an urgent problem to study a kind of coal quality adaptive control strategy for supercritical units, to improve the safety and economy of operation, and to optimize the control system of supercritical units. The adaptive feedforward correction of coal quality is designed. Based on the work coal coefficient and the idea of combined prediction model, a prediction model of coal quantity into the furnace is established. The optimum weight of the work coal coefficient of the first hour to the current time is obtained by using the reciprocal method of variance, and the prediction of the work coal coefficient and the coal quantity into the furnace is realized. The coal quantity of #4 boiler of a 660MW unit is predicted by using the prediction model of coal quantity into the furnace. The results show that the accuracy of using the prediction value of the input coal quantity in real time as the actual coal quantity can reach about 97.0%, which improves the accuracy of the coal quantity into the boiler. The main steam pressure is an important parameter to characterize the energy supply and demand of supercritical units, and the main influencing factor is the fuel quantity. At present, most thermal power plants have mixed fuel and coal, and their calorific value fluctuates greatly, which results in frequent fluctuation of main steam pressure, which seriously affects the safe operation of units. Based on the feedforward control system of fuel quantity, a second-order ADRC is designed. In the feed-back control system of fuel quantity, the closed-loop feedback control is carried out by using ADRC instead of traditional PID. The main purpose of this paper is to estimate the spontaneous disturbance of coal-fired calorific value by means of the expanded state observer and compensate it in real time in the dynamic process to further improve the accuracy of coal intake and prevent the frequent fluctuation of main steam pressure caused by the fluctuation of coal-fired calorific value. The dynamic mathematical model of supercritical once-through boiler is divided into three pressure nodes by the method of pressure node. The conservation equations of mass and energy are listed for each pressure node, and then the equations are simplified and dimensionless. Finally, three pressure nodes are connected in series to obtain the model of supercritical unit fuel steam pressure system. Using the design data of a 660MW supercritical unit to model and calculate, the model calculation parameters of the fuel steam pressure system of the supercritical unit under the condition of 100th THA75THA50THA are obtained. Under three conditions, the model is simulated by traditional PID control and auto disturbance rejection control respectively. The results show that compared with the traditional PID control, the ADRC has stronger anti-interference ability and better robustness. The main steam pressure has better control quality. By comparing the control effect of the traditional PID controller and the active disturbance rejection controller, it can be seen that the active disturbance rejection control scheme with the effect of eliminating disturbance is a promising control scheme.
【學(xué)位授予單位】：華北電力大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM621
本文編號：2197386
[Abstract]:Nowadays, the problems of energy and environment are becoming more and more serious. Because of its high efficiency and low energy consumption, supercritical units are becoming the trend of power plant installation. The combustion control system of supercritical unit is an important part of the whole control system. At present, most thermal power plants have wide sources of coal combustion and large deviation of calorific value, which seriously affects the control of combustion system. Its control level further affects the safety and economy of the whole unit control. Therefore, it is an urgent problem to study a kind of coal quality adaptive control strategy for supercritical units, to improve the safety and economy of operation, and to optimize the control system of supercritical units. The adaptive feedforward correction of coal quality is designed. Based on the work coal coefficient and the idea of combined prediction model, a prediction model of coal quantity into the furnace is established. The optimum weight of the work coal coefficient of the first hour to the current time is obtained by using the reciprocal method of variance, and the prediction of the work coal coefficient and the coal quantity into the furnace is realized. The coal quantity of #4 boiler of a 660MW unit is predicted by using the prediction model of coal quantity into the furnace. The results show that the accuracy of using the prediction value of the input coal quantity in real time as the actual coal quantity can reach about 97.0%, which improves the accuracy of the coal quantity into the boiler. The main steam pressure is an important parameter to characterize the energy supply and demand of supercritical units, and the main influencing factor is the fuel quantity. At present, most thermal power plants have mixed fuel and coal, and their calorific value fluctuates greatly, which results in frequent fluctuation of main steam pressure, which seriously affects the safe operation of units. Based on the feedforward control system of fuel quantity, a second-order ADRC is designed. In the feed-back control system of fuel quantity, the closed-loop feedback control is carried out by using ADRC instead of traditional PID. The main purpose of this paper is to estimate the spontaneous disturbance of coal-fired calorific value by means of the expanded state observer and compensate it in real time in the dynamic process to further improve the accuracy of coal intake and prevent the frequent fluctuation of main steam pressure caused by the fluctuation of coal-fired calorific value. The dynamic mathematical model of supercritical once-through boiler is divided into three pressure nodes by the method of pressure node. The conservation equations of mass and energy are listed for each pressure node, and then the equations are simplified and dimensionless. Finally, three pressure nodes are connected in series to obtain the model of supercritical unit fuel steam pressure system. Using the design data of a 660MW supercritical unit to model and calculate, the model calculation parameters of the fuel steam pressure system of the supercritical unit under the condition of 100th THA75THA50THA are obtained. Under three conditions, the model is simulated by traditional PID control and auto disturbance rejection control respectively. The results show that compared with the traditional PID control, the ADRC has stronger anti-interference ability and better robustness. The main steam pressure has better control quality. By comparing the control effect of the traditional PID controller and the active disturbance rejection controller, it can be seen that the active disturbance rejection control scheme with the effect of eliminating disturbance is a promising control scheme.
【學(xué)位授予單位】：華北電力大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM621
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