A method for distributing heat load in a combined heat and power plant to improve flexibility

Abstract

The application discloses a heat load overall distribution method for improving flexibility of a combined heat and power station, and the operation boundary of an extraction condensing unit of a heat power plant is limited, the electric heat operation area of the unit is obtained by using a variable condition program, then linear fitting is performed on the obtained operation area boundary, and the slope size of the fitting relation formula of the electric heat operation area boundary of each unit is compared, so that the heat load overall distribution method which can maximize the total electric load regulation range of the heat power plant is obtained. The method can be used for heat load optimization distribution among extraction condensing units with different performances and types, so that the total electric load regulation range of the heat power plant is maximized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of thermal power generation, and particularly relates to a heat load overall allocation method for improving the flexibility of a cogeneration power station. BACKGROUND

[0002] In recent years, the renewable energy in China has developed rapidly, and the installed capacity has been increasing. By the end of February 2022, the installed capacity of wind power and photovoltaic power reached 330 million kilowatts and 320 million kilowatts, accounting for 13.8% and 13.4% of the total installed capacity of the country respectively. It is predicted that the proportion of renewable energy power generation will be more than 30% by 2030. On the one hand, there is a large amount of abandoned wind and light, and the power system is facing the severe challenge of high proportion of renewable energy grid connection and consumption. The demand for improving the peak regulation capacity of the power system is increasing. On the other hand, with the acceleration of urbanization, the demand for residential heating and heating is increasing year by year, and the heat load of the thermal power unit is becoming larger and larger. Due to the thermal-electric coupling mechanism of the extraction condensing unit, the peak regulation capacity of the single unit is limited.

[0003] The multi-extraction condensing units of the thermal power plant are coupled for heating. The electric heating operation domains of the units with different performances and types are different, and the peak regulation capacities of the units are different when supplying the same heat load. Therefore, it is required to reasonably allocate the heat load, especially with the increasing demand for heat load, the research on the optimal dispatching of the total heat load of the plant is of great significance to obtain the maximum regulation range of the total electric power of the plant. SUMMARY

[0004] The application aims to obtain the maximum regulation range of the total electric power of the plant by optimizing the heat load allocation between the units, starting from the differences in the electric heating characteristics of the single units. The purpose of the application is to provide a heat load overall allocation method for improving the flexibility of a cogeneration power station. The method can be used for the optimal allocation of the heat load between the extraction condensing units with different performances and types, so as to maximize the regulation range of the total electric load of the thermal power plant.

[0005] The technical solution adopted by the application to solve the technical problem is as follows:

[0006] A heat load overall allocation method for improving the flexibility of a cogeneration power station, the cogeneration power station is supplied with heat by multiple extraction condensing units. The optimal allocation of the heat load is used to maximize the regulation range of the electric load of the thermal power plant. The specific steps are as follows:

[0007] Step 1: Determine the electric and heat load regulation range of the i th extraction condensing unit, expressed as f (D0 i , Pe i , Qh i ) = 0, wherein D0 i is the main steam flow of the i th extraction condensing unit t / h, Pe iis the electric load of the ith extraction condensing unit, MW, Qh i is the heat load of the ith extraction condensing unit, GJ / h, and is specifically as follows:

[0008] (1) The operation limit condition is:

[0009] a) The amount of new steam is less than the maximum continuous evaporation amount of the boiler: limit line AB;

[0010] b) The steam admission amount of the low-pressure cylinder is greater than the minimum condensing flow: limit line BC;

[0011] c) The unit load is greater than the load under the stable combustion condition of the boiler: limit line CD;

[0012] (2) A variable condition function form of the extraction condensing unit is established: [Pe i ,Ddyr i ]=f(D0 i ,Qh i ), Ddyr i is the steam admission amount of the low-pressure cylinder of the ith extraction condensing unit, t / h, and the function gives the electric load and the steam admission amount of the low-pressure cylinder under the condition of the main steam amount and the heat load;

[0013] (3) Two layers of cycles including the main steam amount and the heat load changing according to a certain step are constructed, wherein the inner layer cycle is a cycle of the heat load from 0 to the maximum extraction steam amount, and the outer layer cycle is a cycle of the main steam amount from the maximum main steam amount to the minimum main steam amount, and a condition judgment of the minimum steam admission amount of the low-pressure cylinder is embedded in the inner layer cycle, and if the minimum steam admission amount of the low-pressure cylinder is not satisfied, the cycle is exited; an A-B-C-D-A region is obtained with the heat load as the horizontal coordinate and the electric load as the vertical coordinate, and the region is composed of the limit lines AB, BC and CD;

[0014] (4) According to the function [Pe i ,Ddyr i ]=f(D0 i ,Qh i ), the electric and heat loads obtained by the two-layer cycle calculation are recorded in a two-dimensional matrix, the first column corresponds to the electric and heat loads under the maximum main steam amount line, and the last column corresponds to the electric and heat loads under the minimum main steam amount line; a new matrix is added in the condition judgment, which is used to record a set of electric and heat loads under the maximum extraction steam amount at each main steam amount, and the last set of electric and heat loads corresponding to the minimum condensing flow is the last set of electric and heat loads for each main steam amount cycle;

[0015] Step 2: The total electric load adjustment range of the power plant can be maximized by overall allocation of the heat load, and the specific process is as follows:

[0016] (1) According to the three limit lines obtained, the limit lines are fitted:

[0017] AB: Pe i =kmaxi *Qh i +b maxi ;

[0018] BC: Pe i =k nqi *Qh i +b nqi ;

[0019] CD: Pe i =k mini *Qh i +b maxi ;

[0020] In the formula: k, b are the slope and intercept of each line segment;

[0021] (2) The upper limit of power generation is determined by the AB line, and the slopes of the AB line are arranged in order from small to large, which are:

[0022] k zqmax1 <k zqmax2 <k zqmax3 <…<k zqmaxn

[0023] The heat load distribution method is that the larger the k zqmaxi The unit is preferentially heated to the maximum heat load, and the excess heat load is borne by the next unit, that is, k zqmaxn The corresponding unit is preferentially heated, and finally k zqmax1 The corresponding unit is heated;

[0024] (3) The lower limit boundary of the power generation of each extraction condensing unit is composed of CD and BC lines, wherein the slope of CD line is less than 0, and the slope of BC line is greater than 0. The slopes corresponding to each line are arranged in order from small to large, which are:

[0025] k zqmin1 <k zqmin2 <k zqmin3 <…<k zqminn <k nq1 <k nq2 <k nq3 <…<k nqn

[0026] (4) Each extraction condensing unit has a critical heat load and a maximum heat load point, and the respective heat loads are:

[0027] Q con1 , Q con2 , Q con3 , … Q conn

[0028] QH max1 , QH max2 , QHmax3 ,... QH maxn

[0029] The lower limit of power of each extraction condensing unit corresponds to the heat load (0, Q coni , QH maxj ), Q coni The subscript number corresponds to the slope of the minimum main steam flow line in (3) of step 2, QH maxj The subscript number corresponds to the slope of the minimum condensing flow line in (3) of step 2, and these heat load nodes together constitute 2n heat load intervals:

[0030] (0, Q con1 ),

[0031] (Q con1 , Q con1 + Q con2 ),...

[0032] (Q con1 + Q con2 +... + Q con(n-1) , Q con1 + Q con2 +... + Q con(n-1) + Q conn ),

[0033] (Q con1 + Q con2 +... + Q con(n-1) + Q conn , Q con2 +... + Q con(n-1) + Q conn + QH max1 ),

[0034] (Q con2 +... + Q con(n-1) + Q conn + QH max1 , Q con3 +... + Q con(n-1) + Q conn + QH max1 + QH max2 ),...

[0035] (Q conn + QH max1 + QH max2 +... + QH max(n-1) , QH max1 + QH max2 +... + QH maxn )

[0036] (5) There is a heat load distribution method, in each interval, the corresponding slope of the extraction condensing unit undertakes an additional part of the heat load, which contains 0,

[0037] In (0, Q con1 ) k zqmin1 corresponding to the line segment unit undertakes an additional part of the heat load, the second to n units undertake heat load is 0;

[0038] In (Q con1 , Q con1 +Q con2 ) k zqmin2 corresponding to the line segment unit undertakes an additional part of the heat load, the first unit undertakes heat load is Q con1 , the second to n units undertake heat load is 0;

[0039] In (Q con1 +Q con2 +...+Q con(n-1) +Q conn , Q con2 +...+Q con(n-1) +Q conn +QH max1 ) k nq1 corresponding to the line segment unit undertakes an additional part of the heat load, the second to n units undertake heat load is Q con2 , Q con3 , … Q conn .

[0040] The heat load allocation method for improving the flexibility of cogeneration power plants can obtain the operation parameters of the extraction condensing unit by heat test when the actual performance of the extraction condensing unit and the relative error of the heat balance diagram exceed 10%, and obtain the electricity and heat operation domain by re-fitting calculation of the turbine stage efficiency.

[0041] The heat load allocation method for improving the flexibility of cogeneration power plants needs to delete or add new slopes and nodes, and re-perform the unit sorting and superposition in step 2 if there is a shutdown unit or a new unit in the cogeneration power plant.

[0042] The heat load allocation method for improving the flexibility of cogeneration power plants only needs to replace the node heat load 0 in step 2 with the minimum heat supply load of the unit if the unit has a minimum heat supply load requirement when considering safe operation.

[0043] The heat load overall allocation method for improving the flexibility of a combined heat and power plant, if the combined heat and power plant has a high back pressure unit, the high back pressure unit electric heat load is one-to-one corresponding, and the slope of the high back pressure unit electric heat operation line is usually the largest, the maximum heat load is provided when the upper limit of the total electric power is calculated, the minimum heat load is provided when the lower limit of the total electric power is calculated, and the remaining heat load is borne by the extraction condensing unit and subjected to step 2 sequencing and superposition.

[0044] The heat load overall allocation method for improving the flexibility of a combined heat and power plant, if the combined heat and power plant has an extraction back pressure unit, the extraction back pressure unit and the extraction condensing unit have similar electric heat characteristics, which are in a region, the upper limit of which is divided into two segments and the lower limit of which is one segment, then a processing method of slope sequencing, interval division and linear superposition is adopted.

[0045] The heat load overall allocation method for improving the flexibility of a combined heat and power plant, the upper and lower limits of the electric power obtained form a comprehensive electric heat operation domain of the combined heat and power plant, which represents the operation relationship between the total electric load and the total heat load of the power plant.

[0046] Compared with the prior art, the present application has the following advantages:

[0047] (1) The present application uses the unit electric heat operation region obtained by the variable working condition program calculation, and then linearly fits the obtained operation domain boundary, and then compares the slope of the fitting relationship of the unit electric heat operation domain boundary, to obtain the heat load overall allocation method that makes the total electric load adjustment range of the combined heat and power plant the largest, so that the total electric load adjustment range of the combined heat and power plant is the largest. The present application can be used for the heat load optimization allocation among extraction condensing units with different performances and types.

[0048] (2) The present application is simple, easy and convenient to use, and since it is only related to the unit characteristics, the comprehensive electric heat characteristic domain of the whole plant can be obtained for a specific combined heat and power plant. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 is an electric heat operation domain diagram of an extraction condensing unit.

[0050] Figure 2a and Figure 2b are two extraction condensing units, respectively, and are comparison diagrams of the upper and lower limits of the total electric power for heat supply and the intelligent algorithm calculation results.

[0051] Figure 3 is a comprehensive electric heat characteristic domain of two extraction condensing units and a heat load allocation method diagram thereof.

[0052] Figure 4 is a comparison diagram of the lower limit of the total electric power for heat supply of three extraction condensing units and the intelligent algorithm calculation results. DETAILED DESCRIPTION

[0053] The present application will be further described in detail below in combination with the drawings and specific embodiments.

[0054] A heat load overall allocation method for improving the flexibility of a combined heat and power plant, the combined heat and power plant being supplied with heat by a plurality of extraction condensing units, the electric load regulation range of the combined heat and power plant being maximized through optimized allocation of the heat load, and the specific steps being as follows:

[0055] Step 1: determining the electric and heat load regulation range of the i-th extraction condensing unit, expressed as f(D0 i ,Pe i ,Qh i )=0, wherein D0 i is the main steam flow of the i-th extraction condensing unit t / h, Pe i is the electric load of the i-th extraction condensing unit MW, and Qh i is the heat load of the i-th extraction condensing unit GJ / h, and the specific steps being as follows:

[0056] (1) the operation limitation condition is:

[0057] a) the amount of new steam is less than the maximum continuous evaporation amount of the boiler: the limitation line AB;

[0058] b) the amount of steam entering the low-pressure cylinder is greater than the minimum condensing flow: the limitation line BC;

[0059] c) the unit load is greater than the load under the stable combustion condition of the boiler: the limitation line CD;

[0060] (2) a variable condition function form of the extraction condensing unit [Pe i ,Ddyr i ]=f(D0 i ,Qh i ) is established, Ddyr i is the steam entering amount of the low-pressure cylinder of the i-th extraction condensing unit t / h, and the function gives the electric load and the steam entering amount of the low-pressure cylinder under the given main steam amount and heat load;

[0061] (3) a two-layer cycle including the main steam amount and the heat load changing according to a certain step is constructed, wherein the inner layer cycle is a cycle of the heat load from 0 to the maximum extraction steam amount, and the outer layer cycle is a cycle of the main steam amount from the maximum main steam amount to the minimum main steam amount, and a condition judgment of the minimum steam entering amount of the low-pressure cylinder is embedded in the inner layer cycle, and if the minimum steam entering amount of the low-pressure cylinder is not satisfied, the cycle is exited; an A-B-C-D-A area with the heat load as the horizontal coordinate and the electric load as the vertical coordinate and composed of the limitation lines AB, BC and CD is obtained;

[0062] (4) according to the function [Pe i ,Ddyr i ]=f(D0 i ,Qh i), two-layer circulation calculation obtained electrical, thermal load record in two-dimensional matrix, the first column corresponds to the maximum main steam line under the electrical and thermal load, the last column corresponds to the minimum main steam line under the electrical and thermal load; In the condition judgment, a new matrix is added to record a set of electrical and thermal load when the extraction steam quantity is maximum under each main steam quantity, and the last set of electrical and thermal load corresponding to the minimum condensing quantity line is obtained for each main steam quantity circulation;

[0063] Step 2: The total electrical load adjustment range of the power plant can be maximized by allocating the thermal load in an overall manner, as follows:

[0064] (1) According to the obtained three limiting lines, fitting is performed thereon:

[0065] AB: Pe i =k maxi *Qh i +b maxi ;

[0066] BC: Pe i =k nqi *Qh i +b nqi ;

[0067] CD: Pe i =k mini *Qh i +b maxi ;

[0068] In the formula: k, b are the slope and intercept of each line segment;

[0069] (2) The upper limit of power generation is determined by the AB line, and the slopes of the AB line are arranged in ascending order as follows:

[0070] k zqmax1 <k zqmax2 <k zqmax3 <…<k zqmaxn

[0071] The heat supply load distribution method is that the larger the k zqmaxi corresponding unit is preferentially heated to the maximum heat supply load, and the excess heat load is borne by the next unit, that is, the k zqmaxn corresponding unit is preferentially heated, and finally the k zqmax1 corresponding unit is heated;

[0072] (3) The lower limit boundary of the power generation capacity of each extraction condensing unit is composed of CD and BC lines, wherein the slope of CD line is less than 0, and the slope of BC line is greater than 0. The corresponding slope of each line is arranged in ascending order as follows:

[0073] k zqmin1 <k zqmin2 <k zqmin3<… <k zqminn <k nq1 <k nq2 <k nq3 <… <k nqn

[0074] (4) Each extraction condensing unit has a critical heat load and a maximum heat load point, and their respective heat loads are as follows:

[0075] Q con1 Q con2 Q con3 ...Q conn

[0076] QH max1 QH max2 QH max3 ...QH maxn

[0077] The lower limit of the power output of each extraction condensing unit corresponds to the heat load (0, Q). coni QH maxj ), Q coni The subscript number corresponds to the slope of the minimum main steam flow line in step 2 (3), QH maxj The subscript numbers correspond to the slope of the minimum condensate flow rate line in step 2 (3). These heat load nodes together form 2n heat load intervals:

[0078] (0, Q) con1 ),

[0079] (Q con1 Q con1 +Q con2 ),...

[0080] (Q con1 +Q con2 +...+Q con(n-1) Q con1 +Q con2 +...+Q con(n-1) +Q conn ),

[0081] (Q con1 +Q con2 +...+Q con(n-1) +Q conn Q con2 +...+Q con(n-1) +Q conn +QH max1 ),

[0082] (Q con2 +...+Q con(n-1) +Q conn +QH max1 Qcon3 +...+Q con(n-1) +Q conn +QH max1 +QH max2 )、...

[0083] (Q conn +QH max1 +QH max2 +...+QH max(n-1) ,QH max1 +QH max2 +...+QH maxn )

[0084] (5) There is a heat load distribution method, in each interval, the corresponding slope of the extraction condensing unit to bear an additional portion of the heat load, which with the extraction condensing unit to bear the node heat load, including 0, for example:

[0085] In (0, Q con1 ) k zqmin1 Corresponding line segment unit to bear an additional portion of the heat load, the second to n unit to bear the heat load is 0;

[0086] In (Q con1 , Q con1 +Q con2 ) k zqmin2 Corresponding line segment unit to bear an additional portion of the heat load, the first unit to bear the heat load is Q con1 , the second to n unit to bear the heat load is 0;

[0087] In (Q con1 +Q con2 +...+Q con(n-1) +Q conn , Q con2 +...+Q con(n-1) +Q conn +QH max1 ) k nq1 Corresponding line segment unit to bear an additional portion of the heat load, the second to n unit to bear the heat load is Q con2 , Q con3 , … Q conn .

[0088] The heat load allocation method for improving the flexibility of a combined heat and power plant, when the actual performance of the extraction condensing unit and the heat balance diagram have a relative error of more than 10%, the extraction condensing unit operating parameters can be obtained again through the extraction condensing unit heat test, and the electric heating operation domain is obtained by re-fitting calculation of the turbine stage efficiency.

[0089] As a preferred embodiment of the present application, in step 2, the least square polynomial fitting (one time) is used to fit the electric heating operation domain limit line.

[0090] The heat load overall allocation method for improving the flexibility of a combined heat and power plant, if there is a shutdown unit or a new unit in the combined heat and power plant, needs to delete or add a new slope and node, and then re-perform the unit sorting and superposition in step 2.

[0091] The heat load overall allocation method for improving the flexibility of a combined heat and power plant, if there is a minimum heat supply load requirement for the unit in the combined heat and power plant in consideration of safe operation, only needs to replace the node heat load 0 in step 2 with the minimum heat supply load of the unit.

[0092] The heat load overall allocation method for improving the flexibility of a combined heat and power plant, if there is a high back pressure unit in the combined heat and power plant, the electric heat load of the high back pressure unit is one-to-one corresponding, and the slope of the electric heat operation line of the high back pressure unit is usually the largest, the maximum heat load is supplied when the upper limit of the total electric power is calculated, the minimum heat load is supplied when the lower limit of the total electric power is calculated, and the remaining heat load is borne by the extraction condensing unit and the sorting and superposition in step 2 are performed.

[0093] The heat load overall allocation method for improving the flexibility of a combined heat and power plant, if there is an extraction back pressure unit in the combined heat and power plant, the extraction back pressure unit and the extraction condensing unit have similar electric heat characteristics, which are represented as a region, the upper limit of which is divided into two segments and the lower limit of which is divided into one segment, then a processing method of slope sorting, interval division and linear superposition is adopted.

[0094] The heat load overall allocation method for improving the flexibility of a combined heat and power plant, the upper and lower limits of the electric power form a comprehensive electric heat operation domain of the combined heat and power plant, which represents the operation relationship between the total electric load and the total heat load of the power plant.

[0095] The specific case calculation results are as follows:

[0096] Figure 2a And Figure 2b The total electric power upper and lower limits and the intelligent algorithm calculation results when two extraction condensing units supply heat are respectively given. Figure 3 The comprehensive electric heat characteristic domain of the two extraction condensing units and the heat load allocation method corresponding to the upper and lower limits when the total heat load is in different ranges are given. Figure 4 The total electric power lower limit and the intelligent algorithm calculation results when three extraction condensing units supply heat are given. It can be seen from the comparison that the calculation results of the present application are consistent with the intelligent algorithm, simple and easy to implement, and the comprehensive electric heat characteristic domain of the whole plant and the heat load allocation method can be obtained.

Claims

1. A method for coordinating and allocating heat load to improve the flexibility of combined heat and power (CHP) plants, characterized in that: A combined heat and power (CHP) power plant is supplied with heat by multiple extraction condensing turbine units. By optimizing the distribution of heat load, the electrical load regulation range of the CHP power plant is maximized. The specific steps are as follows: Step 1: Determine the electric heating load adjustment range of the i-th extraction condensing unit, denoted as f(D0). i Pe i ,Qh i )=0, where D0 i For the main steam flow rate (t / h) of the i-th extraction condensing unit, Pe i For the electrical load (MW) of the i-th extraction condensing unit, Qh i The heat load (GJ / h) of the i-th extraction condensing unit is as follows: (1) The operating restrictions are: a) The amount of new steam is less than the boiler's maximum continuous evaporation capacity: Limit line AB; b) Low-pressure cylinder steam inlet flow rate is greater than minimum condensing steam flow rate: Limit line BC; c) The unit load exceeds the load under stable boiler combustion conditions: Limit line CD; (2) Establish the variable operating condition function form of the extraction condensing unit [Pe] i Ddyr i ]=f(D0 i ,Qh i ), Ddyr i Let t / h be the steam inlet flow rate of the low-pressure cylinder of the i-th extraction condensing unit. This function takes the main steam flow rate and thermal load as input and obtains the electrical load and the steam inlet flow rate of the low-pressure cylinder. (3) The structure includes two-layer circulations where the main steam volume and heat load change at a certain step size. The inner circulation is the circulation where the heat load changes from 0 to the maximum extraction steam volume, and the outer circulation is the circulation where the main steam volume changes from the maximum main steam volume to the minimum main steam volume. A condition judgment of the minimum steam intake of the low-pressure cylinder is embedded in the inner circulation. If the minimum steam intake of the low-pressure cylinder is not met, the loop is exited. The ABCDA region is obtained with heat load as the horizontal axis and electrical load as the vertical axis, and is composed of the limit lines AB, BC, and CD. (4) According to the function [Pe i Ddyr i ]=f(D0 i ,Qh i The electrical and thermal loads obtained from the two-layer loop calculation are recorded in a two-dimensional matrix. The first column corresponds to the electrical and thermal loads under the maximum main steam flow line, and the last column corresponds to the electrical and thermal loads under the minimum main steam flow line. A new matrix is ​​added to the condition judgment to record a set of electric heating loads corresponding to the minimum condensing flow limit conditions for each main steam cycle. Step 2: By coordinating and allocating heat load, the total electrical load regulation range of the cogeneration power plant can be maximized, as detailed below: (1) Based on the three obtained constraint lines, fit them: AB:Per i =k maxi *Qh i +b maxi ; BC:Pe i =k nqi *Qh i +b nqi ; CD:Pe i = k mini *Qh i +b maxi ; In the formula: k and b are the slope and intercept of each line segment; (2) The upper limit of power generation is determined by line AB. Arrange the slopes of line AB in ascending order as follows: k zqmax1 <k zqmax2 <k zqmax3 <…<k zqmaxn The heating load distribution method is as follows: k zqmaxi Larger generating units are given priority to supply heat up to their maximum heating load; any excess heat load is handled by the next largest unit, i.e., k. zqmaxn The corresponding generating unit is given priority for heating, and k is given last. zqmax1 Heating is supplied by the corresponding unit; (3) The lower limit boundary of the power generation of each extraction condensing unit is composed of lines CD and BC, where the slope of line CD is less than 0 and the slope of line BC is greater than 0. The slopes of each line are arranged in ascending order as follows: k zqmin1 <k zqmin2 <k zqmin3 <…<k zqminn <k nq1 <k nq2 <k nq3 <…<k nqn (4) Each extraction condensing unit has a critical heat load and a maximum heat load point, and their respective heat loads are as follows: Q con1 、Q con2 、Q con3 、…Q conn QH max1 QH max2 QH max3 ,…QH maxn The lower limit of the power output of each extraction condensing unit corresponds to the heat load (0, Q). coni QH maxj ), Q coni The subscript number corresponds to the slope of the minimum main steam flow line in step 2 (3), QH maxj The subscript numbers correspond to the slope of the minimum condensate flow rate line in step 2 (3). These heat load nodes together form 2n heat load intervals: (5) Based on the above steps, the heat load of the cogeneration power plant is allocated in the following way: within each heat load interval, the extraction condensing unit with the corresponding slope bears the heat load exceeding the node, and the remaining extraction condensing units bear the heat load corresponding to the node. exist inner k zqmin1 The corresponding unit in the line segment bears the additional heat load, while the 2nd to nth units bear 0 heat load. exist inner k zqmin2 The corresponding unit bears the additional heat load, with the first unit bearing a heat load of Q. con1 The heat load borne by units 2 to n is 0; exist inner k nq1 The corresponding unit bears the additional heat load, and the heat loads borne by units 2 to n are Q respectively. con2 Q con3 ...Q conn .

2. The method for coordinating and allocating heat load to improve the flexibility of a combined heat and power plant according to claim 1, characterized in that: When the relative error between the actual performance of a certain extraction condensing unit in a cogeneration power plant and the heat balance diagram exceeds 10%, the operating parameters of the extraction condensing unit are obtained again through thermal tests, the turbine stage efficiency of the extraction condensing unit is refitted, and the electrothermal operating range of the extraction condensing unit is obtained.

3. The method for coordinating and allocating heat load to improve the flexibility of a combined heat and power plant according to claim 1, characterized in that: If a combined heat and power plant has out-of-service units or newly added units, the unit sorting and overlay work in step 2 needs to be repeated after deleting or adding new slopes and nodes.

4. The method for coordinating and allocating heat load to improve the flexibility of a combined heat and power plant according to claim 1, characterized in that: If the cogeneration power plant unit has a minimum heating load requirement for safe operation, simply replace the "0" in the first heating load interval in step 2 with the unit's minimum heating load.

5. The method for coordinating and allocating heat load to improve the flexibility of a combined heat and power plant according to claim 1, characterized in that: If a cogeneration power plant has high back-pressure units, the electrical and thermal loads of the high back-pressure units correspond one-to-one, and the slope of the electrical and thermal operating line of the high back-pressure units is usually the largest. The maximum heat load is supplied when the upper limit of the total electrical power is calculated, and the minimum heat load is supplied when the lower limit of the total electrical power is calculated. The remaining heat load is then undertaken by the extraction condensing unit and the sorting and superposition work in step 2 is carried out.

6. The method for coordinating and allocating heat load to improve the flexibility of a combined heat and power plant according to claim 1, characterized in that: If a combined heat and power plant has a back-pressure extraction unit, and the back-pressure extraction unit exhibits similar electrothermal characteristics to the condensing extraction unit, with its upper boundary divided into two segments and its lower boundary into one segment, then a method of slope sorting, dividing the intervals, and then linearly superimposing the results is adopted.

7. The method for coordinating and allocating heat load to improve the flexibility of a combined heat and power plant according to claim 1, characterized in that: The upper and lower limits of the power generation capacity of the cogeneration power plant are obtained, forming the comprehensive electric and thermal operation domain of the cogeneration power plant, which represents the operating relationship between the total electrical load and the total thermal load of the power plant.

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