CN102278738A - Boiler feed-forward quantification simple and quick calculation method based on energy balance - Google Patents
Boiler feed-forward quantification simple and quick calculation method based on energy balance Download PDFInfo
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- CN102278738A CN102278738A CN2011101364497A CN201110136449A CN102278738A CN 102278738 A CN102278738 A CN 102278738A CN 2011101364497 A CN2011101364497 A CN 2011101364497A CN 201110136449 A CN201110136449 A CN 201110136449A CN 102278738 A CN102278738 A CN 102278738A
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Abstract
A control circuit, which is more critical in the coordination control of a thermal power generating unit, is used in formation and adjustment of the boiler feed-forward. The boiler feed-forward and steam engine feed-forward are operated corporately when the large range of load change exists especially, so that the control effect of the unit load change is assured. However, the forming way and formulation of the boiler feed-forward are often obtained by experienced thermotechnical operators through testing in the actual set debugging and production process such that the forming way and the formulation of the boiler feed-forward have great subjectivity and uncertainty. The invention discloses a boiler feed-forward quantification simple and quick calculation method based on energy balance. According to the calculation method, the parameters including the generation/disappearance velocity of the boiler feed-forward, the final height and lasting time of the boiler feed-forward and the like, for restricting the function and the shape of the boiler feed-forward are related to the set response time, the set storage heat utilization degree and the set load change velocity. According to the invention, the characteristic parameters of the boiler feed-forward can be set quickly and the adjusting efficiency of a set coordination control system is improved greatly.
Description
Technical field
The present invention relates to the automation field of fired power generating unit, the boiler that uses in specifically a kind of coordination control in the fired power generating unit quantitative shortcut Calculation method that feedovers based on energy balance.
Background technology
In the coordination of fired power generating unit control, generally comprise boiler master loop and steam turbine main control loop, by the FEEDBACK CONTROL in boiler master loop and the steam turbine main control loop guarantee that unit is loaded under nominal situation and vapour pressure in appointed positions.Yet under the load change operating mode, above-mentioned FEEDBACK CONTROL can't satisfy load and the requirement of vapour pressure parameter control, must be improved by the means of FEEDFORWARD CONTROL.FEEDFORWARD CONTROL mainly comprises two parts: static feedforward and dynamic Feedforward, and static feedforward can draw according to the static parameter of each operating mode, and the indication feedforward is all dynamic Feedforward among the present invention.Wherein, act on the accumulation of heat that steam turbine feedforward in the steam turbine main control loop is used to discharge unit; Act on the hysteresis that boiler feedforward in the boiler master loop is used to overcome the fuel link.Therefore the boiler feedforward often is designed to generate according to the differential of load variations, and in addition suitable restriction.When load began to change, the boiler feedforward produced; When load variations finished, the boiler feedforward disappeared.The formation of boiler feedforward and adjustment are that fired power generating unit is coordinated control loop relatively more crucial in the control, and in the load change process, especially when load change on a large scale, boiler feedforward and steam turbine feedforward acting in conjunction have guaranteed the control effect that unit load changes.Yet take place and the problems such as relation of opportunity, boiler feedforward and the load change speed and the mobility scale of involution such as the size of boiler feedforward action, boiler feedforward, then often need test to determine and adjust, have bigger subjectivity and uncertainty, and expended the long period.The generation type of boiler feedforward and being formulated in order to coordinate to control key point and the difficult point in the debugging.Therefore need find a kind of effective boiler feedforward fast determination method, improve the adjustment efficient of unit cooperative control system.
Summary of the invention
Technical problem to be solved by this invention is to overcome the defective that above-mentioned prior art exists, a kind of boiler based on energy balance quantitative shortcut Calculation method that feedovers is provided, can determine each key property parameter that the boiler feedforward forms fast by this method, to improve the adjustment efficient of unit cooperative control system.
For this reason, the present invention adopts following technical scheme: a kind of boiler based on energy balance quantitative shortcut Calculation method that feedovers, it is characterized in that, suppose that it is S1 that the fired power generating unit heat storage capacity satisfies the needed initial stage energy of load change process, correlation properties to the boiler feedforward are quantitatively calculated, be defined as follows in calculating and suppose: boiler instructs be t the lag time of load responding, and its unit is min; Load and coal amount corresponding relation are B, and its unit is t/mwh; The maximum change speed that the boiler instruction is allowed is K, and its unit is mw/min; Target load change speed is R, and its unit is mw/min; The target load amplitude of variation is M, and its unit is mw;
Calculated as can be known by above-mentioned definition and hypothesis: energy S1=KRt2/2 of needed initial stage of load change process (K-R), its unit are mwmin; The required theoretical maximum height h=RtB[t/h that reaches of boiler feedforward]; The boiler feedforward reaches the needed time t1=RtB/K of maximum height, and its unit is min; The boiler feedforward theoretical time range later the time be M/R-t between the M/R, its unit is min; Load instruction when the boiler feedforward is turned one's head and the deviation range between the load target are between 0 to Rt, and its unit is mw.
The present invention is based on energy budget method the origin cause of formation and the character of boiler feedforward are analyzed, analytic process is as follows: under the situation that does not have disturbance, can think that there are the corresponding relation of determining in fuel quantity, steam generating amount and unit load.The chemical energy of supposing fuel, when load change, only needs get final product according to the corresponding adjustment of the relation curve of a determining boiler output less than lagging behind to the conversion between the electric energy of unit load so.Yet in real process, there is the hysteresis of all too many levels in the chemical energy of fuel to the conversion between the electric energy of unit load, and only the relation curve of determining according to target load is corresponding adjusts the requirement that boiler output can't satisfy load control.Therefore need overcome above-mentioned hysteresis by the mode of FEEDFORWARD CONTROL, satisfy the control requirement.
The present invention only utilizes degree and unit load rate of change just can quantitatively determine the formation/extinction time of boiler feedforward and the wording depth of boiler feedforward according to unit response time, unit accumulation of heat.The derivation of computational methods of the present invention is an energy budget method, does not relate to the analysis and the derivation of transfer function, does not have the complicated equation of higher degree to find the solution, and whole process is simple, clear.Needed calculating parameter is known parameter or the parameter that is easy to obtain in the computational process of the present invention, need not carry out special attribute testing, and the threshold of computing application is lower.
The invention will be further described below in conjunction with specification drawings and specific embodiments.
Description of drawings
Fig. 1-1 is load change process under the no boiler feedforward.
Fig. 1-2 is a desirable boiler feedforward load change process down.
Fig. 1-3 is an actual boiler feedforward load change process (accumulation of heat is enough) down.
Fig. 1-4 is an actual boiler feedforward load change process (accumulation of heat deficiency) down.
Fig. 2-1 is the contrast operating mode of load change process.
Fig. 2-2 is long operating mode lag time.
Fig. 2-3 is the slower operating mode of load change speed.
Fig. 2-4 is the less operating mode of load change amplitude.
Fig. 2-5 is the boiler feedforward degree of contrast schematic diagram under Fig. 2-1,2-2,2-3, the 2-4 situation.
Fig. 3 is the theoretical computed altitude and the actual height contrast schematic diagram of boiler feedforward.
The specific embodiment
Load uphill process curve with certain unit is an example, by energy budget method the action principle of boiler feedforward is analyzed, and is the action principle and the comparative analysis schematic diagram of boiler feedforward in this process shown in Fig. 1-1,1-2,1-3, the 1-4.
As can be seen, in the load uphill process, when boiler instruction during fully according to the corresponding reference instruction curvilinear motion of load target, because the boiler instruction transformation is that actual load exists lag time, actual load will lag behind the load target from Fig. 1-1.Therefore the load deviation between actual load and the load target needs the FEEDFORWARD CONTROL of boiler instruction to be revised.
In Fig. 1-2, the load deviation of instructing FEEDFORWARD CONTROL to revise in boiler is interpreted as a kind of energy, and this energy can be considered needed leading energy in the load change process.Consider that the boiler instruction transformation is that actual load exists lag time, will rely on the unit accumulation of heat to satisfy the energy requirement in this stage at the initial stage of load change.Therefore be S1 and two parts of S2 with above-mentioned leading energy binned, the S1 part that should satisfy wherein for the unit accumulation of heat, S2 is the part that boiler feedovers and should satisfy.S2 is corresponded to S2 ' in the boiler instruction according to lagged relationship, S1 is corresponded to S1 ' in the boiler instruction according to similarity relation, can draw the boiler instruction after the desirable boiler feedforward of stack.
Because the rate of change of boiler instruction has been subjected to all multifactor restrictions such as pulverized coal preparation system, furnace pressure, initial period in load variations, the boiler instruction can not be changed in the mode of vertical lifting, but finishes variation according to the slope that allows, and change procedure is as shown in Fig. 1-3.As can be seen, behind the rate of change that reduces the boiler instruction, the S1 in the leading energy requirement partly increases, and promptly needs bigger unit accumulation of heat to finish load change.
When the unit accumulation of heat can't be satisfied the increase part of S1 in the leading energy requirement, actual load can not change according to the load aim curve fully, and the realized load curve shown in Fig. 1-4 has characterized this situation.Under the situation of this accumulation of heat underutilization, be easy to occur the correction of load and vapour pressure is caused the fluctuation of actual load line owing to PID controller in the coordinated control system.
Suppose that the unit accumulation of heat is enough to satisfy energy S1 of needed initial stage of load change process the factor that may influence the boiler feedforward is carried out qualitative analysis, the factor of analyzing comprises: lag time, load change speed and the load change amplitude of boiler instruction, analytic process is as shown in Fig. 2-1,2-2,2-3,2-4,2-5.
Fig. 2-1 is the contrast operating mode of analysis of Influential Factors, boiler feedforward analysis of influential factors is all contrasted this operating mode carries out, think that in analytic process the Initial change speed of boiler instruction remains unchanged, the shape of its boiler feedforward is shown in the contrast performance curve A of the load change process among Fig. 2-5.
1) lag time of boiler instruction
Be the boiler feedforward situation after boiler instruction prolongation lag time shown in Fig. 2-2, as can be seen from the figure: energy S1 of needed initial stage of load change process increases, and the requirement of unit accumulation of heat increases; The maximum height of boiler feedforward increases, and the feedforward shape is shown in the lag time among Fig. 2-5 long performance curve B.
2) load change speed
Be the boiler feedforward situation after the reduction of load change speed shown in Fig. 2-3, as can be seen from the figure: the needed initial stage of load change process, energy S1 reduced, and the requirement of unit accumulation of heat reduces; The maximum height of boiler feedforward reduces, and the feedforward shape is shown in the slower performance curve C of the load change speed among Fig. 2-5.
3) load change amplitude
Be the boiler feedforward situation after the reduction of load change speed shown in Fig. 2-4, as can be seen from the figure: the needed initial stage of load change process, energy S1 was constant, and requiring of unit accumulation of heat is constant; The maximum height of boiler feedforward is identical, and the feedforward shape is shown in the less performance curve D of the load change amplitude among Fig. 2-5, and the feedforward action time shortens.
In sum, heat storage capacity, the load change speed of the maximum height of boiler feedforward and unit are relevant.The action time of boiler feedforward is relevant with the covering process of load change amplitude, unit accumulation of heat.
According to derivation conclusion of the present invention, the shortcut Calculation method that the present invention draws the boiler feedforward is as follows: consider that the unit heat storage capacity satisfies energy S1 of needed initial stage of load change process, with the process among Fig. 1-3 is example, and the correlation properties of boiler feedforward are quantitatively calculated.Be defined as follows in calculating and suppose: boiler instructs be t[min the lag time of load responding]; Load and coal amount corresponding relation are B[t/mwh]; The maximum change speed that the boiler instruction is allowed is K[mw/min]; Target load change speed is R[mw/min]; The target load amplitude of variation is M[mw].
Calculate as can be known by above-mentioned derivation conclusion and hypothesis: energy S1=KRt2/2 of needed initial stage of load change process (K-R) [mwmin]; The required theoretical maximum height h=RtB[t/h that reaches of boiler feedforward]; The boiler feedforward reaches the needed time t1=RtB/K[min of maximum height]; Theoretical time range (M/R-t, M/R) [min] when the boiler feedforward is turned one's head; Load instruction when the boiler feedforward is turned one's head and the deviation range between the load target (0, Rt) [mw].
Use the present invention, the work of adjusting of coordinating boiler feedforward in the control is finished fast, improved the adjustment efficient of unit cooperative control system.
In certain 600MW supercritical unit debugging, adopted the present invention to finish adjusting fast of boiler feedforward.Process is as follows: at first according to this machine unit characteristic and result of the test, the approximate generating capacity correspondence of thinking 1mw the coal-fired consumption of 0.42t/h, boiler is about 2.5min-3min lag time, carry it into the aforementioned calculation formula, conversion is the characteristic manner of fuel quantity, and result of calculation is as shown in table 1:
According to the aforementioned calculation result, finish fast at the adjusting of feedforward parameter before the boiler, and test adjustment on this basis, adjusted result and calculated data basically identical, relativity is as shown in Figure 3.
Claims (1)
1. the boiler based on energy balance quantitative shortcut Calculation method that feedovers, it is characterized in that, suppose that it is S1 that the fired power generating unit heat storage capacity satisfies the needed initial stage energy of load change process, correlation properties to the boiler feedforward are quantitatively calculated, be defined as follows in calculating and suppose: boiler instructs be t the lag time of load responding, and its unit is min; Load and coal amount corresponding relation are B, and its unit is t/mwh; The maximum change speed that the boiler instruction is allowed is K, and its unit is mw/min; Target load change speed is R, and its unit is mw/min; The target load amplitude of variation is M, and its unit is mw;
Learnt by above-mentioned definition and hypothesis calculating: energy S1=KRt2/2 of needed initial stage of load change process (K-R), its unit are mwmin; The required theoretical maximum height h=RtB[t/h that reaches of boiler feedforward]; The boiler feedforward reaches the needed time t1=RtB/K of maximum height, and its unit is min; The boiler feedforward theoretical time range later the time be M/R-t between the M/R, its unit is min; Load instruction when the boiler feedforward is turned one's head and the deviation range between the load target are between 0 to Rt, and its unit is mw.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113238589A (en) * | 2021-04-25 | 2021-08-10 | 东南大学 | Method for setting parameters of superheated steam temperature load feedforward controller |
| CN113231188A (en) * | 2021-06-07 | 2021-08-10 | 国投云顶湄洲湾电力有限公司 | Method for improving response load rate of generator set of pulverizing system of medium-speed coal mill |
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2011
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113238589A (en) * | 2021-04-25 | 2021-08-10 | 东南大学 | Method for setting parameters of superheated steam temperature load feedforward controller |
| CN113238589B (en) * | 2021-04-25 | 2022-02-11 | 东南大学 | Method for setting parameters of superheated steam temperature load feedforward controller |
| CN113231188A (en) * | 2021-06-07 | 2021-08-10 | 国投云顶湄洲湾电力有限公司 | Method for improving response load rate of generator set of pulverizing system of medium-speed coal mill |
| CN113231188B (en) * | 2021-06-07 | 2022-05-24 | 国投云顶湄洲湾电力有限公司 | Method for improving response load rate of generator set of pulverizing system of medium-speed coal mill |
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