Logical design method for reverse dynamic correction of boiler energy storage coefficient using load deviation

Abstract

The present invention discloses a logic design method for dynamically correcting the boiler energy storage coefficient of a unit coordination system by using load deviation. The method proposes a correction logic of a quasi-dynamic energy storage signal based on the original energy storage calculation. The logic performs different logic operations according to different adjustment directions and different adjustment states of the unit. The result of the operation is to obtain a real-time correction coefficient vector δ of the energy storage coefficient. Compared with the prior art, the present invention has the following advantages: 1) The idea of ​​dynamically correcting the energy storage coefficient is applied to the dynamic adjustment of thermal power units under the direct energy balance control mode, so that the real-time nature of boiler energy changes can be applied to coordinated control; 2) Real-time correction of the energy storage coefficient can improve the anti-interference ability in the coordinated control optimization process, and has a certain anti-interference effect on the output disturbance of coal and fans; 3) The energy storage coefficient correction can ensure the adjustment accuracy when the load is slightly adjusted.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal power plant control, and relates to a thermal power unit CCS system control optimization design method, and specifically to a logic design method for reversely and dynamically correcting a boiler energy storage coefficient by utilizing load deviation. Background Art

[0002] In order to cope with the load disturbance caused by new energy, the frequency and depth of thermal power unit regulation have become increasingly unpredictable. The optimization of the original energy storage coefficient for the coordination system is essentially a fixed parameter (energy storage coefficient) participating in the dynamic adjustment of the load and pressure of the coordination system. At the same time, the existing energy storage coefficient is defined based on the drum pressure and the main steam pressure, and is the sum of the pressure-energy (non-linear) change relationship of the water-cooled wall, the drum, and the superheater system. The water-cooled wall and the drum are based on the drum pressure change, and the superheater system is based on the main steam pressure change. Therefore, the existing energy storage coefficient has the following problems when participating in the coordinated control adjustment under direct energy balance (DEB):

[0003] (1) The energy storage coefficient is a theoretical calculated value under ideal conditions. The premise of pressure-energy change is the stable supply of fuel and air volume. Although it describes the inherent energy storage characteristics of the boiler system, it has a certain deviation compared with the actual operating state, that is, the energy storage coefficient does not have dynamic characteristics.

[0004] (2) The energy storage coefficient is directly related to the pressure change of each process, but the drum pressure and main steam pressure cannot linearly correspond to the real-time load output under actual conditions. Without being directly related to the load variable, the existing energy storage coefficient is difficult to adapt to the coordinated control system with load deviation and pressure deviation as the control target. The variable relationship is as follows: Figure 1 shown.

[0005] In the on-site operating units, the dynamic change process of boiler energy is generally: water-cooled wall-steam drum-superheater system. The main body is the dynamic change between the boiler evaporation and the main steam flow. The intermediate change characteristics are reflected by the change of the steam pressure of the steam drum. The combustion of the boiler directly affects the size of the evaporation, and the size of the steam flow reflects the external load demand. Therefore, to obtain the dynamic energy storage coefficient, the parameters of the entire process must be dynamically monitored and then calculated in real time. The main control variable relationship is as follows: Figure 2 shown.

[0006] How to obtain the dynamic energy storage coefficient corresponding to different load changes will better reflect the significance of the energy storage coefficient participating in the adjustment in the coordinated control system based on direct energy balance.

[0007] The above adjustment process is now represented by the following function:

[0008] C c(N) = f(N);

[0009] In the formula, the energy storage coefficient is C c (N), N is the load value, f is the fitting function of the energy storage coefficient corresponding to the load under different loads obtained in the early stage through data calculation or field test. The function is piecewise and discontinuous. In practical applications, fixed parameters are often used to obtain global parameters through fuzzification, so that a smoother mapping function can be obtained.

[0010] However, during actual unit operation, especially during load adjustment, the mapping function changes, that is, the fuzzy intermediate value cannot describe the real dynamic energy storage signal, so that the dynamic energy storage signal cannot be used to adjust the dynamically changing controlled object. This is also the difficulty in the current application of fixed energy storage signals and the acquisition of dynamic energy storage signals.

[0011] There are many methods for calculating the energy storage coefficient of coal-fired boilers under different stable states. However, the calculations of these methods are mostly based on ideal conditions, at least when the unit is stable in one operating condition, and the energy storage coefficient under the corresponding state is obtained directly through disturbance experiments or calculated using data processing after data collection. Summary of the invention

[0012] The purpose of the present invention is to provide a logic design method for dynamically correcting the boiler energy storage coefficient by utilizing load deviation. The energy storage coefficient obtained by this method is finally used for coordinated optimization, especially in the coordinated control system under direct energy balance (DEB).

[0013] The objective of the present invention is achieved through the following technical solutions:

[0014] A logic design method for reversely and dynamically correcting a boiler energy storage coefficient using load deviation comprises the following steps:

[0015] Step 1: Collect historical data of the unit under stable operation, and use the data averaging method to obtain the steam-water parameters in the steam drum, water wall and superheater corresponding to the typical load point;

[0016] Step 2: Process the data collected in step 1, and use the segmented and working medium calculation method to calculate the heat storage coefficients of the drum, water wall and superheater under the steady state of each typical load point, and obtain the standard energy storage coefficient distribution of the boiler under pressure changes under 50% to 100% load conditions;

[0017] Step 3: Design the implementation logic of the dynamic correction of the boiler energy storage coefficient. The specific steps are as follows:

[0018] For the coordinated control system using direct energy balance, when the direct energy balance signal is used, the feedback signal u of the fuel control loop is bbfor:

[0019]

[0020] Where p1 is the regulating stage pressure, representing the energy entering the turbine, and p d is the drum pressure, and after using the correction coefficient, the optimized feedback signal u' bb for:

[0021]

[0022] In the formula, δ=[δ1δ2δ3], C c =[C s ; C b ; C t ], δ1 corresponds to C s As the water wall energy storage coefficient C s Correction coefficient; δ2 corresponds to C b As the drum energy storage coefficient C b Correction coefficient; δ3 corresponds to C t As the superheated steam section energy storage coefficient C t Correction coefficient; C c (ΔN) refers to the real-time energy storage factor calculated based on the actual load change ΔN;

[0023] Step 4: Correct the dynamics of the energy storage coefficient under load deviation. The specific steps are as follows:

[0024] Step 1: Determine the load increase or decrease. After obtaining the change trend, take the existing N0 load as the benchmark and obtain the corresponding upper limit load value N according to the pressure change range of 1MPa. S0 and C c0 ;

[0025] Step 2: Determine N S0 With N S The difference between |N S0 -N S |<1MW, then directly use C c0 Assigned as the energy storage parameter δC in the coordinated system c (ΔN); when |N S0 -N S |≧1MW, proceed to the third step;

[0026] Step 3: Calculate N S The standard energy storage coefficient under the load is obtained by referring to the distribution of the standard energy storage coefficient of the boiler under pressure changes, and the corresponding pressure value under the load is obtained. The obtained drum pressure and main steam pressure deviation are processed in sections, and the section interval is still 1MPa, and the number of sections is used as the step size for updating the energy storage coefficient.

[0027] Step 4: Update the energy storage coefficient of the interval variable step length. Whenever the pressure deviation interval decreases by 1MPa, repeat the second and third steps until the pressure deviation is reduced to within 1MPa, then execute the first step;

[0028] Step 5: Calculate the correction factor δ.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] 1) The idea of ​​using dynamic correction of energy storage coefficient is proposed to be applied to the dynamic adjustment of thermal power units under direct energy balance control, so that the real-time change of boiler energy can be applied to coordinated control;

[0031] 2) Real-time correction of the energy storage coefficient can improve the anti-interference ability in the coordinated control optimization process, and has a certain anti-interference effect on the output disturbance of coal and fans;

[0032] 3) The energy storage factor correction can ensure the adjustment accuracy when the load is adjusted slightly. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The correlation between energy storage coefficient and key parameters under ideal conditions;

[0034] Figure 2 The correlation between the energy storage coefficient and key parameters under field conditions;

[0035] Figure 3 This is the schematic diagram of energy storage coefficient correction. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described below in conjunction with the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0037] The present invention provides a logic design method for reversely dynamically correcting the boiler energy storage coefficient of a unit coordination system by using load deviation. The method proposes a correction logic of a quasi-dynamic energy storage signal based on the original energy storage calculation. This logic performs different logic operations according to different adjustment directions and different adjustment states of the unit. The result of the operation is to obtain a real-time correction coefficient vector δ of the energy storage coefficient.

[0038] The above correction coefficient and energy storage coefficient together constitute the dynamic energy storage coefficient:

[0039] C c (N(t)) = δC c (N) (1).

[0040] In the above formula, Cc (N) is the standard working condition, under the traditional calculation method, the corresponding relationship between the unit load and the boiler energy storage, C c (N(t)) is the actual energy storage of the boiler at load N(t) at time t under the actual operating state, and δ is the correction coefficient.

[0041] The correction factor of the energy storage coefficient is affected by two factors. The first factor is the influence of load changes, the difference between the load increase and load reduction operation processes of the unit. The reason for this division is that when the unit is dynamically adjusting the load, the adjustment directions of steam, water, and fuel under load increase and load reduction are different (such as the different directions of change in the enthalpy value of steam), which makes the energy storage have a certain inertia, so it is necessary to distinguish and calculate the correction coefficient for the two states of load increase and load reduction. The second factor is the disturbance factor under stable load. When the load output is in a relatively stable state, its energy storage coefficient also changes. Its main influencing factors are external disturbances, such as fluctuations in main steam temperature, fuel, wind, etc. Therefore, it is more reasonable to analyze the correction coefficients of the energy storage coefficients under different states separately. The energy storage coefficient corrected by the above method can continuously change the load adjustment rate during the load adjustment process of the unit, thereby reducing problems such as overshoot caused by large and rapid changes in load. Specifically include the following steps:

[0042] Step 1: Collect historical data of the unit under stable operation, and use the data averaging method to obtain the steam-water parameters in the steam drum, water wall and superheater corresponding to the typical load point, which are used to calculate the energy storage coefficient under stable state.

[0043] The implementation of this step is based on the existing energy storage coefficient calculation. The main principles are as follows: First, the steam-water system of the boiler is divided into three parts: water-cooled wall, steam drum and superheating system; then, the energy storage coefficients of the steam-water and metal are calculated respectively; finally, the coefficients of the three parts are added up as the total energy storage coefficient.

[0044] Step 2: Process the data collected in step 1, and use the segmented and working medium calculation method to calculate the heat storage coefficients of the steam drum, water wall and superheater under stable conditions at each typical load point, and obtain the standard energy storage coefficient distribution of the boiler under pressure changes under load conditions of 50% to 100%.

[0045] In this step, the heat storage coefficients C of the drum, water wall and superheater under steady state at each typical load point are calculated. c (ΔN)(C c (ΔN) refers to the real-time energy storage coefficient calculated based on the actual load change ΔN) and the calculation rules are as follows:

[0046] After obtaining the steam-water parameters of the water-cooled wall, drum, and superheated steam system in each load range of 50% to 100%, the energy storage basic coefficient set is calculated according to the amplitude of each change of 1MPa. The relevant calculation is relatively mature in the industry and will not be described in detail here. For example, the derivation method described in the document "Theoretical Calculation and Analysis of Heat Storage Coefficient of Drum Boiler" written by Ma Boyang. The data in Table 1 can be obtained as follows:

[0047] Table 1 Distribution of boiler standard energy storage coefficient under pressure change

[0048]

[0049] The data in Table 1 are segmented according to the changes in the drum pressure and the superheated steam section pressure under the steady state. The data obtained are the middle point data. For the convenience of practical application, the data between each interval point can be regarded as a local linear distribution. By directly performing a linear average distribution, the energy storage coefficient corresponding to each point can be obtained.

[0050] Therefore, the energy storage coefficient under stable state can be obtained as:

[0051] C c =C s +C b +C t (2).

[0052] In the above formula, C c Represents the total boiler energy storage factor.

[0053] When the load changes, first determine whether the load increase ΔN is a large change. The criteria for determination are: N s -N t Whether the pressure change across the change exceeds 1MPa, if the drum pressure P b Or the main steam pressure P t If any of the two changes exceeds 1MPa, it can be regarded as a large load change. s is the load instruction. After receiving the instruction, you can directly refer to Table 1 to obtain the corresponding drum pressure P b , Main steam pressure P t , water wall heat storage coefficient C s , Drum heat storage coefficient C b , Superheated steam heat storage coefficient C t Here, only the relevant parameters of the target load are obtained, the instantaneous load N t The above data need to be recalculated. The calculation principle is based on instantaneous parameters and 1MPa load change as the target. The instantaneous energy storage coefficient is obtained by using the existing calculation method, such as the calculation scheme mentioned by Ma Boyang in the theoretical calculation and analysis of the heat storage coefficient of the drum boiler: the water-cooled wall heat storage coefficient C s0, Drum heat storage coefficient C b0 , Superheated steam heat storage coefficient C t0 , and then obtain the total energy storage coefficient C c0 .

[0054] Step 3: Design the implementation logic of dynamic correction of boiler energy storage coefficient;

[0055] The design of the present invention is aimed at a coordinated control system using direct energy balance. When the direct energy balance signal is used, the feedback signal u of the fuel control loop bb Using heat signals, generally:

[0056]

[0057] Where p1 is the regulating stage pressure, representing the energy entering the turbine, and p d is the drum pressure. After adopting the correction factor, the feedback signal of the fuel control loop becomes u' bb , combined with formula (1), the optimized feedback signal is:

[0058]

[0059] C c (ΔN) and C c The difference is that the former is the matrix value of the real-time energy storage coefficient calculated according to the actual load change ΔN, which is composed of the vector δ and the segmented energy storage vector coefficient vector C c The multiplied value, where δ = [δ1 δ2 δ3], C c =[C s ; C b ; C t ], δ1 corresponds to C s As the water wall energy storage coefficient C s Correction coefficient; δ2 corresponds to C b As the drum energy storage coefficient C b Correction coefficient; δ3 corresponds to C t As the superheated steam section energy storage coefficient C t The correction factor of .

[0060] Step 4: Correct the dynamics of energy storage coefficient under load deviation.

[0061] When the energy storage coefficient is dynamically corrected during load adjustment, the overall principle is as follows: Figure 3 shown.

[0062] Based on the data calculation and rule setting in the above steps, the coefficient correction steps are as follows:

[0063] Step 1: Determine the load increase or decrease. After obtaining the change trend, take the existing N0 load as the benchmark and obtain the corresponding upper limit load value N according to the pressure change range of 1MPa. S0 and C c0 .

[0064] Step 2: Determine N S0 With N S The difference between |N S0 -N S |<1MW, then directly use C c0 Assigned as the energy storage parameter δC in the coordinated system c (ΔN); when |N S0 -N S |≧1MW, proceed to the third step.

[0065] Step 3: Calculate N S The standard energy storage coefficient under load is directly referenced to the existing data in Table 1 to obtain the corresponding pressure value under load, and the obtained drum pressure and main steam pressure deviation are processed in sections, the section interval is still 1MPa, and the number of sections is used as the step size for updating the energy storage coefficient. It should be pointed out here that if the load is between N0 and N s During the change process, the drum pressure changes by 3.6MPa and the main steam pressure changes by 4.1MPa, then the update step size is selected as 5, that is, the selected step size must completely cover the pressure change range.

[0066] Step 4: Update the energy storage coefficient of the interval variable step length. Whenever the pressure deviation interval decreases by 1MPa, repeat the second and third steps until the pressure deviation is reduced to within 1MPa, then execute the first step;

[0067] Step 5: Calculate the correction coefficient δ. In the above steps 2 and 3, as long as it is within a range, the calculation of the correction coefficient can be regarded as a local linear change. The calculation of the correction coefficient is calculated in proportion, and the rules are as follows:

[0068] Take 200MW load as the starting load, the corresponding drum pressure and main steam pressure are assumed to be 13MPa and 15MPa, the target load is 280MW, and the pressures are 15.8MPa and 18.6MPa respectively:

[0069] When the maximum pressure deviation corresponding to the load deviation is determined to be 2.8MPa and 3.6MPa by referring to Table 1 before execution, the first step only needs to calculate the energy storage coefficient within 1MPa of the adjacent deviation, that is, four initial data iterations (4 times can cover 3.6MPa), and both the first calculation and the second calculation can satisfy δ=[1 1 1], until a non-integer pressure deviation value appears, the corresponding δ=[δ1 δ2 δ3] coefficient will change. At this time, when the third update is made, δ1 and δ2 are directly related to the drum pressure, so the coefficient becomes 0.8. At this time, the steam deviation must not reach 3, that is, the third update of the energy storage coefficient should be C c (ΔN)=[0.8 0.8 1][C s ; C b ; C t ], until the last deviation is within 1MPa, if the two pressure deviations of the load deviation approach value reach 0.6 and 0.8, then δ=[δ1 δ2 δ3] becomes [0.6 0.6 0.8]. Here, for the sake of clarity, only the principle is explained in terms of data. The actual data changes may not be so, because the drum pressure and the main steam pressure are asynchronous in the process of load approach, and will not change at the speed of 1MPa at the same time. The 0.6 and 0.8 here are only to illustrate a value assignment principle of δ when dealing with non-integer pressure deviations, and are only used as an alternative representation of non-integer pressure deviation variables.

Claims

1. A logical design method for reversely and dynamically correcting the boiler energy storage coefficient using load deviation, characterized in that The method comprises the following steps: Step 1: Collect historical data of the unit under stable operation, and use the data averaging method to obtain the steam-water parameters in the steam drum, water wall and superheater corresponding to the typical load point; Step 2: Process the data collected in step 1, and use the segmented and working medium calculation method to calculate the heat storage coefficients of the drum, water wall and superheater under the steady state of each typical load point, and obtain the standard energy storage coefficient distribution of the boiler under pressure changes under 50% to 100% load conditions; Step 3: Design the implementation logic of the dynamic correction of the boiler energy storage coefficient. The specific steps are as follows: For the coordinated control system using direct energy balance, when the direct energy balance signal is used, the feedback signal u of the fuel control loop is bb for: Where p1 is the regulating stage pressure, p d is the drum pressure, and after using the correction coefficient, the optimized feedback signal u' bb for: In the formula, δ=[δ1δ2δ3], C c =[C s ; C b ; C t ], δ1 corresponds to C s As the water wall energy storage coefficient C s Correction factor of δ2 corresponds to C b As the drum energy storage coefficient C b Correction coefficient; δ3 corresponds to C t As the superheated steam section energy storage coefficient C t Correction coefficient; C c (ΔN) refers to the real-time energy storage factor calculated based on the actual load change ΔN; Step 4: Correct the dynamics of energy storage coefficient under load deviation.

2. The logic design method for reverse dynamic correction of boiler energy storage coefficient using load deviation according to claim 1 is characterized in that In step 2, the heat storage coefficients of the drum, water wall and superheater under steady state at each typical load point are calculated. c The calculation rule of (ΔN) is as follows: after obtaining the steam-water parameters in the water-cooled wall, steam drum and superheated steam system in each load range from 50% to 100%, the energy storage basic coefficient set is calculated respectively according to the amplitude of each change of 1MPa.

3. The logic design method for reverse dynamic correction of boiler energy storage coefficient using load deviation according to claim 1 is characterized in that The specific steps of step 4 are as follows: Step 1: Determine the load increase or decrease. After obtaining the change trend, take the existing N0 load as the benchmark and obtain the corresponding upper limit load value N according to the pressure change range of 1MPa. S0 and C c0 , C c0 is the total energy storage coefficient; Step 2: Determine N S0 With N S The difference, N s is the load instruction, when |N S0 -N S |<1MW, then directly use C c0 Assigned as the energy storage parameter δC in the coordinated system c (ΔN); when |N S0 -N S |≧1MW, proceed to the third step; Step 3: Calculate N S The standard energy storage coefficient under the load is obtained by referring to the distribution of the standard energy storage coefficient of the boiler under pressure changes, and the corresponding pressure value under the load is obtained. The obtained drum pressure and main steam pressure deviation are processed in sections, and the section interval is still 1MPa, and the number of sections is used as the step size for updating the energy storage coefficient. Step 4: Update the energy storage coefficient of the interval variable step length. Whenever the pressure deviation interval decreases by 1MPa, repeat the second and third steps until the pressure deviation is reduced to within 1MPa, then execute the first step; Step 5: Calculate the correction factor δ.

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