CN109063890B - A heat load distribution method based on the maximization of the peak shaving capacity of the whole thermal power plant - Google Patents

Abstract

The invention discloses a heat load distribution method based on the maximization of the whole plant peak regulation capacity of a thermal power plant. The invention starts from studying the difference of thermoelectric relationship between different thermal power units in thermal power plants, establishes a mathematical model of the steam extraction volume and the upper and lower limits of the electric power of the unit, and then gives the objective functions of the upper and lower limits of the total power of the whole plant, so as to ensure that the heat supply remains unchanged. Under the premise of , the fmincon function of MATLAB tool is used for optimization calculation, and the best heat load distribution scheme is given, so that the total peak shaving capacity of the whole plant can be maximized. The research results of the present invention can optimize the operating conditions of the thermal power plant on-line, increase the upper limit of peak regulation in the whole plant, and reduce the lower limit of peak regulation in the whole plant by rationally distributing the steam extraction amount of each unit.

Description

A heat load distribution method based on the maximization of the peak shaving capacity of the whole thermal power plant

technical field

The invention relates to the technical field of thermal power generation, in particular to a heat load distribution method based on maximizing the peak-shaving capacity of the whole plant of a thermal power plant.

Background technique

In recent years, with the increasing pressure of environmental protection, the state has stepped up efforts to develop new energy power generation, including conventional hydropower, wind power, solar power and so on. However, the development of new energy units in some regions is too fast. Due to the particularity of the power generation of new energy units, especially the anti-peak shaving characteristics of wind turbines, it brings severe challenges to the peak shaving of the power grid, resulting in an increasingly prominent problem of new energy consumption. The anti-peak shaving characteristics of wind turbines are characterized by the daily output fluctuating within a certain range during the day, and the wind power output gradually rising at night, and the seasonal output characteristics of the highest average output in winter and the lowest average output in summer, resulting in a considerable degree of wind power grid connection. In 2015, the national wind abandonment rate was as high as 15%, in 2016 it reached 21%, and it improved in 2017, but it also reached 12%. At the same time, the utilization hours of thermal power units have also gradually decreased. In 2015, the utilization hours of thermal power were 4,329h, in 2016, they were 4,165h, and are expected to be around 4,000h in 2017. Thermal power units are basically running under peak regulation; On the other hand, the proportion of heating units in the northern region is getting higher and higher. As the main heat source, the thermal power unit needs to meet the heat load first, and there are operating constraints under the operating condition of "fixing electricity by heat", which leads to serious restrictions on the peak-shaving capacity in the heating season, and even Peak shaving is impossible, and the "wind and heat conflict" aggravates the difficulty of peak shaving.

In the past, the research on the peak shaving capacity of thermal power units mostly focused on the study of the electrical and thermal characteristics of the unit itself, while the research on the peak shaving capacity of the whole plant was relatively small. The capacity varies. Under the condition of a certain heat supply in the whole plant, the maximum peak shaving capacity of the whole plant can be obtained by rationally distributing the heat load. The effect of peak shaving performance is more obvious. For the heat load distribution of the whole plant, it is necessary to fully consider the differences in the peak shaving capacity of different types of units, and determine the heat load distribution scheme between different types of units, so that the total peak shaving capacity of the whole plant's units is maximized.

SUMMARY OF THE INVENTION

In view of the above problems, the present invention proposes a plant-wide heat load distribution method to maximize the plant-wide peak-shaving capability based on the electrical and thermal characteristics of the heating units and considering the difference in peak-shaving capacity between units.

The invention adopts the following technical scheme: a heat load distribution method based on the maximization of the peak-shaving capacity of the thermal power plant. There are different heating modes, and it is characterized in that it includes the following steps:

Step 1: Record the extraction steam volume, extraction steam pressure, extraction steam temperature and extraction steam drainage temperature under the current operating conditions of each unit;

Step 2: According to the extraction steam pressure, extraction steam temperature, and extraction steam drainage temperature recorded in Step 1, the extraction steam enthalpy and extraction steam drainage enthalpy of each unit are calculated by using the thermal property model of industrial water and steam;

Step 3: Calculate the heat supply of each unit according to the extraction steam volume of each unit in step 1 and the extraction steam enthalpy and extraction steam drainage enthalpy in step 2, and then obtain the current total heat supply of the whole plant;

Step 4: Take the whole plant as a unit, collect the heating condition diagram of each unit, and use the heating condition diagram of each unit to draw the thermoelectric relationship curve; that is, the curve of the upper limit of the power of each unit with the steam extraction volume and the lower limit of the power of each unit with the steam extraction. quantity change curve;

Among them, the heating condition diagram is the coupling relationship diagram of the intake steam volume, the extraction steam volume and the active power; each extraction steam volume has a corresponding maximum and minimum power. Enter EXCEL and the minimum power value respectively to generate a thermoelectric relationship curve;

Step 5: Add trend lines to the curve of the upper limit of power of each unit with the change of steam extraction volume and the curve of the lower limit of power of each unit with the change of steam extraction volume, and fit the formula to obtain the mathematical relationship between the upper limit of power, lower limit of power and extraction volume of each unit ;

Step 6: Further accumulatively obtain the mathematical relationship between the upper and lower limits of the total power of the whole plant and the extraction steam volume;

Step 7: According to the mathematical relationship between the upper limit and lower limit of the total power of the whole plant and the steam extraction volume of each unit obtained in Step 6, and the set constraints, the upper and lower limits of the total power of the whole plant and the mathematical relationship of the steam extraction volume of each unit are calculated. The relational expression is used as the objective function, and is solved by the fmincon function in the MATLAB optimization toolbox to obtain the extraction steam volume based on the upper limit of the whole plant peak regulation and the extraction steam volume based on the lower limit of the whole plant peak regulation, and the corresponding total power of the whole plant. Maximum upper limit and minimum lower limit, so as to realize the heat load distribution that maximizes the peak shaving capacity of the whole plant.

The above constraints: the total heat supply of each unit is equal to the current total heat supply of the whole plant calculated in step 3, and the steam extraction volume of each unit does not exceed the maximum allowable steam extraction volume of the unit.

The step 2 is calculated using the IFC-97 thermal property model of industrial water and water vapor loaded in EXCEL.

In the step 3, the calculation formula of the current heat supply of each unit is as follows:

Q _n ′=G _n ′(h _n ′-h _sn ′)

In the formula: Q _n ′ is the current heat supply of the nth unit, G _n ′ is the current heat supply and extraction volume of the nth unit, h _n ′ is the current heat supply and extraction enthalpy of the nth unit, h _sn ' is the current heating extraction steam drainage enthalpy of the nth unit.

Q _a =Q ₁ ′+Q ₂ ′+...+Q _n ′

In the formula: Q _a is the current total heat supply of the whole plant, and Q ₁ ′～Q _n ′ are the current heat supply of the first to nth units respectively.

In the step 5, the calculation formulas of the upper power limit and the lower power limit of each unit are as follows:

PMAX _n =f _max (G _n )

In the formula: PMAX _n is the upper limit of the power of the nth unit, f _max (G _n ) is the unary function of the heating and extraction steam, which is obtained by EXCEL fitting;

PMIN _n =f _min (G _n )

In the formula: PMIN _n is the power lower limit of the nth unit, f _max (G _n ) is the unary function of the heating and extraction steam, which is obtained by EXCEL fitting;

G _n is the extraction steam volume of the nth unit.

In the step 6, the calculation formulas of the upper limit of the total power and the lower limit of the total power of the whole plant are respectively:

PMAX _a =PMAX ₁ +PMAX ₂ +...+PMAX _n

=f _max (G ₁ )+f _max (G ₂ )+…+f _max (G _n )

In the formula: PMAX _a is the upper limit of the total power of the whole plant;

PMIN _a =PMIN ₁ +PMIN ₂ +…+PMIN _n

=f _min (G ₁ )+f _min (G ₂ )+…+f _min (G _n )

In the formula: PMIN _a is the lower limit of the total power of the whole plant;

In the step 7, the expressions for solving the upper limit and lower limit of the total power of the whole plant are as follows: Since the fmincon function can only solve the minimum value, we transform the problem of solving the maximum value of the power upper limit into the problem of solving the minimum value of the negative function of the power upper limit. , the objective function is as follows:

min(-PMAX _a )=min(-(f _max (G ₁ )+f _max (G ₂ )+...+f _max (G _n )))

The objective function of the lower limit of the total power of the whole plant is as follows:

minPMIN _a = min(f _min (G ₁ )+f _min (G ₂ )+…+f _min (G _n ))

The constraint expression for solving the upper limit and lower limit of the total power of the whole plant is as follows:

Q _a =G ₁ (h ₁ -h _s1 )+G ₂ (h ₂ -h _s2 )+...+G _n (h _n -h _sn )

0≤G ₁ ≤G _1max

0≤G ₂ ≤G _2max

_{0≤Gn≤Gnmax _}

In the formula: Q _a is the current total heat supply of the whole plant calculated in step 3, which is a fixed value; G ₁ , G ₂ ,..., G _n are the upper limit and power of the first to nth units in the whole plant respectively. The corresponding extraction steam volumes under the lower limit; G _1max , G _2max , and G _{n max} are the maximum extraction steam volumes of the first to nth units respectively, which are fixed values and are obtained from the heating condition diagram of each unit; h ₁ , h ₂ ...... h _n are the heating extraction enthalpy of the first to n units respectively; h _s1 , h _s2 ...... h _sn are the heating extraction steam drains of the first to n units respectively enthalpy.

The beneficial effects of the present invention are as follows: the present invention starts from studying the difference in the thermoelectric relationship between different thermal power units in a thermal power plant, establishes a mathematical model of the steam extraction volume and the upper and lower limits of the electric power of the unit, and then provides the objective functions of the upper and lower limits of the total power of the whole plant, Under the premise of ensuring the constant heat supply, the fmincon function of the MATLAB tool is used for optimization calculation, and the best heat load distribution scheme is given, so that the total peak shaving capacity of the whole plant can be maximized. The research results of the present invention can optimize the operating conditions of the thermal power plant on-line, increase the upper limit of peak regulation in the whole plant, and reduce the lower limit of peak regulation in the whole plant by rationally distributing the steam extraction amount of each unit.

Through the online optimization of each thermal power plant, the peak shaving capacity of the power grid is improved, and the consumption of new energy is promoted, which brings significant economic and social benefits, and has a very broad application prospect.

Description of drawings

Figure 1 is a diagram of the heating condition of a unit;

Figure 2 is a graph of the thermoelectric relationship of a unit;

Figure 3 is a fitting formula diagram of the thermoelectric relationship curve of a unit.

Detailed ways

The basic situation of a power plant is as follows, the first phase project #1 and #2 units are two subcritical, one-time intermediate reheat, extraction and condensing units, the model is NC330/242-16.7/0.8/535/535, the steam extraction position It is a medium-pressure cylinder exhaust steam, the design rated heating pressure is 0.8MPa, the rated steam extraction flow rate is 340t/h, and the maximum extraction steam flow rate is 400t/h; the second-phase project #3 and #4 units are two supercritical units with one intermediate reheating. , Extraction condensing unit, model is C350/294-24.2/0.43/566/566, steam extraction position is medium pressure cylinder exhaust, design rated extraction pressure is 0.43MPa, rated extraction flow is 400t/h, the maximum The extraction steam flow is 500t/h.

The current operating conditions of the power plant are that #1, #3, and #4 units are running, and #2 unit is shut down. The current extraction steam volume and peak shaving upper and lower limits of each unit and the entire plant are shown in the following table:

Table 1 The current steam extraction volume and peak shaving upper and lower limits of each unit and the whole plant

The thermal load distribution method proposed by the invention is used to optimize the peak shaving capacity of the thermal power plant on-line, and by redistributing the steam extraction amount of each unit, the upper limit of the total peak shaving of the whole plant is increased, and the lower limit of the total peak shaving is lowered. Its heat load distribution method includes the following steps:

Step 1: Record the extraction steam volume, extraction steam pressure, extraction steam temperature and extraction steam drainage temperature under the current operating conditions of each unit from the DCS system of the thermal power plant, as shown in Table 2;

Table 2 Extraction parameters of each unit

type Extraction pressure (MPa) Extraction steam temperature (℃) Extraction steam flow (t/h) Extraction steam drain temperature (℃) #1 0.64 340.81 152.84 90.28 #3 0.2 227.11 252.45 84.14 #4 0.16 272.14 379 80.32

Among them, the extraction steam drain temperature is the drain temperature of the heat network heater, and the inlet steam pressure of the heat network heater is the default saturation pressure.

Step 2: According to the extraction steam pressure, extraction steam temperature, and extraction steam drainage temperature recorded in Step 1, use the IFC-97 thermal property calculation model of industrial water and steam loaded in EXCEL to calculate the extraction enthalpy and extraction steam of each unit Hydrophobic enthalpy, as listed in Table 3;

Table 3 Extraction enthalpy of each unit

Step 3: Calculate the heat supply of each unit according to the extraction steam volume of each unit in step 1 and the extraction steam enthalpy and extraction steam drainage enthalpy in step 2, and then obtain the current total heat supply of the whole plant.

The calculation formula of the current heat supply of each unit is as follows:

Q _n ′=G _n ′(h _n ′-h _sn ′)

In the formula: Q _n ′ is the current heat supply of the nth unit (GJ/h), G _n ′ is the current heat supply and steam extraction of the nth unit (t/h), and h _n ′ is the nth unit. The current heating and extraction enthalpy of the unit (kJ/kg), h _sn ′ is the current heating and extraction steam drainage enthalpy (kJ/kg) of the nth unit.

Q _a =Q ₁ ′+Q ₂ ′+...+Q _n ′

In the formula: Q _a is the current total heat supply (GJ/h) of the whole plant, and Q ₁ ′～Q _n ′ are the current heat supply of the first to nth units respectively.

According to the above calculation formula and the data listed in Table 2 and Table 3, the heat supply of each unit and the total heat supply of the whole plant can be obtained, as shown in Table 4.

Table 3 Heat supply value of each unit

type Heat supply (GJ/h) #1 643064.26 #3 1009915.57 #4 429456.91 The whole plant 2082436.73

Step 4: Take the whole plant as a unit, collect the heating condition diagram of each thermal power unit, and draw the thermoelectric relationship curve using the heating condition diagram of each unit. The heating condition diagram is usually the coupling relationship diagram of the steam intake, the extraction steam and the active power. As can be seen from the figure, each extraction steam volume has a corresponding maximum and minimum power. We input the different extraction steam volumes and the corresponding maximum and minimum power values into EXCEL respectively, and the thermoelectric relationship curve as shown in Figure 2 can be generated. , the upper curve in the figure is the change curve of the upper limit of the unit power with the steam extraction volume, and the lower curve is the change of the lower limit of the unit power with the steam extraction volume.

Step 5: Add trend lines to the generated power upper limit curve and power lower limit curve in EXCEL and fit the formula. The power upper limit curve is generally an approximate straight line, and linear fitting can be used; the power lower limit curve is generally a broken line, and polynomial fitting can be adopted. , in most cases, the fourth-order polynomial fitting can meet the accuracy requirements. The trend line and fitting formula are shown in Figure 3. In this way, we have obtained the mathematical relationship between the upper power limit, lower power limit and extraction volume of each unit.

The calculation formulas for the upper limit and lower power limit of each unit are as follows:

PMAX _n =f _max (G _n )

In the formula: PMAX _n is the upper limit of the power of the nth unit (MW), G _n is the current heat supply and extraction volume (t/h) of the nth unit; f _max (G _n ) is the heat supply and extraction volume The unary function of , obtained by EXCEL fitting;

PMIN _n =f _min (G _n )

In the formula: PMIN _n is the power lower limit of the nth unit, f _max (G _n ) is the unary function of the heating and extraction steam, which is obtained by EXCEL fitting;

According to the heating condition diagram of the #1 unit, the relationship between the upper limit of the power of the #1 unit and the heat supply and extraction volume is as follows:

PMAX ₁ = -0.2261G ₁ +341.96

The relationship between the power lower limit of the #1 unit and the amount of heating and extraction steam is as follows:

PMIN ₁ =1.47*10 ^-8 G ₁ ⁴ -1.1069*10 ^-5 G ₁ ³ +2.7366*10 ^-3 G ₁ ² -0.47985G ₁ +220.03

Units #3 and #4 are of the same type. Therefore, the relationship between the upper limit and lower limit of power and the amount of heating and extraction steam fitted according to the unit’s heating condition diagram is the same. The relationship between the upper limit of power and the amount of heating and extraction steam is as follows:

PMAX ₃ = -0.2003G ₃ +391.57

The relationship between the lower limit of power and the amount of heating and extraction steam is as follows:

PMIN ₃ =1.2083*10 ^-8 G ₃ ⁴ +1.1009*10 ^-5 G ₃ ³ -1.9486*10 ^-3 G ₃ ² -0.17934 G ₃ +235.44

Step 6: According to the mathematical relationship between the upper limit of power, lower limit of power and steam extraction volume of each unit obtained in step 5, the mathematical relationship between the upper limit of total power, lower limit of total power and extraction volume of the whole plant is obtained by accumulating.

Among them, the calculation formulas of the upper limit of the total power and the lower limit of the total power of the whole plant are:

PMAX _a =PMAX ₁ +PMAX ₂ +...+PMAX _n

=f _max (G ₁ )+f _max (G ₂ )+…+f _max (G _n )

In the formula: PMAX _a is the upper limit of the total power of the whole plant;

PMIN _a =PMIN ₁ +PMIN ₂ +…+PMIN _n

=f _min (G ₁ )+f _min (G ₂ )+…+f _min (G _n )

In the formula: PMIN _a is the lower limit of the total power of the whole plant.

According to the fitting relationship between the upper and lower limits of the power of each unit and the heating and extraction volume in step 5, the fitting relationship between the upper and lower limits of the total power of the whole plant and the heating and extraction volume of each unit can be obtained. The relationship between the heat supply and steam extraction of the unit is as follows:

PMAXa=PMAX ₁₊ PMAX ₂₊ PMAX ₃ =-0.2261G ₁ +341.96-0.2003G ₃ +391.57-0.2003G ₄ +391.57

The relationship between the lower limit of the total power of the whole plant and the heating and extraction volume of each unit is as follows:

PMINa=PMIN ₁₊ PMIN ₃₊ PMIN ₄ =1.47*10 ^-8 G ₁ ⁴ -1.1069*10 ^-5 G ₁ ³ +2.7366*10 ^-3 G ₁ ² -0.47985G ₁ +220.03+1.2083*10 ^-8 G ₃ ⁴ +1.1009*10 ^-5G ₃ ³ -1.9486*10 -3G ^{3 2} _{-0.17934G 3 +}

235.44+1.2083*10 ^-8 G ₄ ⁴ +1.1009*10 ^-5 G ₄ ³ -1.9486*10 ^-3 G ₄ ² -0.17934G ₄ +235.44

Step 7: According to the mathematical relationship between the upper and lower limits of the total power of the whole plant and the steam extraction volume of each unit obtained in step 6, and the set constraints: the total heat supply of each unit is equal to the current value of the whole plant calculated in step 3. The total heat supply, the steam extraction volume of each unit does not exceed the maximum allowable steam extraction volume of the unit, and the mathematical relationship between the upper and lower limits of the total power of the whole plant and the extraction steam volume of each unit is used as the objective function. The fmincon function is solved to obtain the extraction steam volume based on the upper limit of the whole plant peak regulation and the extraction steam volume based on the lower limit of the whole plant peak regulation, as well as the corresponding maximum upper limit and minimum lower limit of the total power of the whole plant.

The above expressions for solving the upper limit and lower limit of the total power of the whole plant are as follows:

Since the fmincon function can only solve the minimum value, we transform the problem of solving the maximum value of the upper power limit into the problem of solving the minimum value of the negative function of the upper power limit. The objective function is as follows:

min(-PMAX _a )=min(-(f _max (G ₁ )+f _max (G ₂ )+...+f _max (G _n )))

The objective function of the lower limit of the total power of the whole plant is as follows:

minPMIN _a = min(f _min (G ₁ )+f _min (G ₂ )+…+f _min (G _n ))

The constraint expression for solving the upper limit and lower limit of the total power of the whole plant is as follows:

Q _a =G ₁ (h ₁ -h _s1 )+G ₂ (h ₂ -h _s2 )+...+G _n (h _n -h _sn )

0≤G ₁ ≤G _1max

0≤G ₂ ≤G _2max

_{0≤Gn≤Gnmax _}

In the formula: Q _a is the current total heat supply (GJ/h) of the whole plant calculated in step 3, which is a fixed value; G ₁ , G ₂ ,..., G _n are the first to nth units in the whole plant respectively. The extraction steam volume (t/h) corresponding to the upper limit and lower power limit of the plant respectively; G _1max , G _2max , G _{n max} are the maximum extraction volume (t/h) of the first to nth units respectively, and are The fixed value is obtained from the heating condition diagram of each unit; h ₁ , h ₂ ……h _n are the heating extraction enthalpy of the first to nth units respectively; h _s1 , h _s2 …… h _sn are respectively is the heating extraction steam drainage enthalpy of the first to nth units.

The thermal power plant is optimized online by the above method, and the steam extraction volume of each unit is redistributed. The optimized steam extraction volume of each unit and the whole plant and the upper and lower limits of peak regulation are shown in Table 4:

Table 4 The optimized steam extraction volume and peak shaving upper and lower limits of each unit and the whole plant

The comparison between the upper and lower limits of the total peak shaving of the whole plant before and after optimization is shown in Table 5:

Table 5 Comparison table of upper and lower limits of total peak shaving in the whole plant before and after optimization

The whole plant Peak shaving lower limit (MW) Peak shaving upper limit (MW) Before optimization 606.72 873.65 Optimized 512.61 964.28

It can be seen from Table 5 that the method proposed by the present invention is used to optimize the thermal power plant online, and after redistributing the heat load of each unit, the lower limit of the total peak regulation of the whole plant is significantly reduced, and the upper limit of the total peak regulation is also significantly increased. Peak capacity is significantly improved.

The above descriptions are only preferred embodiments of the present application, and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims (10)

1. A heat load distribution method based on maximizing the peak shaving capacity of the thermal power plant. The thermal power plant has n extraction and condensing steam turbine generator sets to supply heat, n≥2, and there are differences in the capacity or heating mode between the units , is characterized in that, comprises the following steps: Step 1: Record the extraction steam volume, extraction steam pressure, extraction steam temperature and extraction steam drainage temperature under the current operating conditions of each unit; Step 2: According to the extraction steam pressure, extraction steam temperature, and extraction steam drainage temperature recorded in Step 1, the extraction steam enthalpy and extraction steam drainage enthalpy of each unit are calculated by using the thermal property model of industrial water and steam; Step 3: Calculate the heat supply of each unit according to the extraction steam volume of each unit in step 1 and the extraction steam enthalpy and extraction steam drainage enthalpy in step 2, and then obtain the current total heat supply of the whole plant; Step 4: Take the whole plant as a unit, collect the heating condition diagram of each unit, and use the heating condition diagram of each unit to draw the thermoelectric relationship curve; Variation curve with extraction steam volume; Step 5: Add trend lines to the curve of the upper limit of power of each unit with the change of steam extraction volume and the curve of the lower limit of power of each unit with the change of steam extraction volume, and fit the formula to obtain the mathematical relationship between the upper limit of power, lower limit of power and extraction volume of each unit ; Step 6: Further accumulatively obtain the mathematical relationship between the upper and lower limits of the total power of the whole plant and the extraction steam volume; Step 7: According to the mathematical relationship between the upper limit and lower limit of the total power of the whole plant and the steam extraction volume of each unit obtained in Step 6, and the set constraints, the upper and lower limits of the total power of the whole plant and the mathematical relationship of the steam extraction volume of each unit are calculated. The relational expression is used as the objective function, and the optimization toolbox is used to solve it, and the extraction steam volume based on the upper limit of the whole plant peak shaving and the extraction steam volume based on the lower limit of the whole plant peak shaving, as well as the corresponding upper limit and lower limit of the total power of the whole plant are obtained. The minimum value, so as to realize the heat load distribution that maximizes the peak shaving capacity of the whole plant; The constraint conditions: the total heat supply of each unit is equal to the current total heat supply of the whole plant calculated in step 3, and the steam extraction volume of each unit does not exceed the maximum allowable steam extraction volume of the unit. 2. A heat load distribution method based on maximizing the peak shaving capacity of the thermal power plant as claimed in claim 1, wherein the heating condition diagram of the step 4 is the amount of steam intake, steam extraction and active power. The coupling relationship diagram of the three powers; each extraction steam volume has a corresponding maximum and minimum power. Input the different extraction steam volumes and the corresponding maximum and minimum power values into EXCEL to generate a thermoelectric relationship curve. 3. a heat load distribution method based on maximizing the peak shaving capacity of a thermal power plant as claimed in claim 1, wherein the step 2 utilizes the IFC-97 industrial water and steam thermal properties loaded in EXCEL Model calculation. 4. A heat load distribution method based on the maximization of the peak regulation capacity of the thermal power plant as claimed in claim 1, wherein in the step 3, the current calculation formula of the heat supply of each unit is as follows: Q _n ′=G _n ′(h _n ′-h _sn ′) In the formula: Q _n ′ is the current heat supply of the nth unit, G _n ′ is the current heat supply and extraction volume of the nth unit, h _n ′ is the current heat supply and extraction enthalpy of the nth unit, h _sn ' is the current heating extraction steam drainage enthalpy of the nth unit. 5. A heat load distribution method based on maximizing the peak-shaving capacity of the thermal power plant as claimed in claim 4, wherein in the step 3, the current total heat supply calculation formula of the whole plant is: Q _a =Q ₁ ′+Q ₂ ′+...+Q _n ′ In the formula: Q _a is the current total heat supply of the whole plant, and Q ₁ ′～Q _n ′ are the current heat supply of the first to nth units respectively. 6. A heat load distribution method based on maximizing the peak shaving capacity of the thermal power plant as claimed in claim 1, wherein in the step 5, the upper limit of the power of each unit, the lower limit of the power and the steam extraction amount of each unit are calculated. The calculation formulas are as follows: PMAX _n =f _max (G _n ) In the formula: PMAX _n is the upper limit of the power of the nth unit, f _max (G _n ) is the unary function of the heating and extraction steam, which is obtained by EXCEL fitting; PMIN _n =f _min (G _n ) In the formula: PMIN _n is the power lower limit of the nth unit, f _max (G _n ) is the unary function of the heat extraction steam amount, which is obtained by EXCEL fitting. 7. A heat load distribution method based on maximizing the peak shaving capacity of a thermal power plant as claimed in claim 1, wherein in the step 6, the calculation formulas for the upper limit of the total power and the lower limit of the total power are respectively: : PMAX _a =PMAX ₁ +PMAX ₂ +...+PMAX _n =f _max (G ₁ )+f _max (G ₂ )+…+f _max (G _n ) In the formula: PMAX _a is the upper limit of the total power of the whole plant; PMIN _a =PMIN ₁ +PMIN ₂ +…+PMIN _n =f _min (G ₁ )+f _min (G ₂ )+…+f _min (G _n ) In the formula: PMIN _a is the lower limit of the total power of the whole plant. 8 . The heat load distribution method based on the maximization of the peak shaving capacity of the thermal power plant as claimed in claim 1 , wherein, in the step 7, the fmincon function in the MATLAB optimization toolbox is used to solve the problem. 9 . 9. A heat load distribution method based on maximizing the peak shaving capacity of a thermal power plant as claimed in claim 8, wherein in the step 7, the expressions for solving the upper limit and lower limit of the total power of the whole plant are as follows : Since the fmincon function can only solve the minimum value, the problem of solving the maximum value of the power upper limit is transformed into the problem of solving the minimum value of the negative function of the power upper limit. The objective function is as follows: min(-PMAX _a )=min(-(f _max (G ₁ )+f _max (G ₂ )+...+f _max (G _n ))) The objective function of the lower limit of the total power of the whole plant is as follows: _minPMINa = _min (fmin( _G1 ) _{+ fmin} (G2)+...+ _fmin ( _Gn )). 10. A heat load distribution method based on the maximization of the peak shaving capacity of the thermal power plant as claimed in claims 1-9, wherein the constraint condition expression is as follows: Q _a =G ₁ (h ₁ -h _s1 )+G ₂ (h ₂ -h _s2 )+...+G _n (h _n -h _sn ) 0≤G ₁ ≤G _1max 0≤G ₂ ≤G _{2max 0≤Gn≤Gnmax _} In the formula: Q _a is the current total heat supply of the whole plant calculated in step 3, which is a fixed value; G ₁ , G ₂ , ..., G _n are the upper limit of the power of the first to nth units in the whole plant, respectively and the corresponding extraction steam volume under the lower power limit; G _1max , G _2max , and G _nmax are the maximum extraction steam volumes of the first to nth units respectively, which are fixed values and are obtained from the heating condition diagram of each unit; h ₁ , h ₂ ...... h _n are the heating extraction enthalpy of the first to n units respectively; h _s1 , h _s2 ...... h _sn are the first to n units respectively Unit heating extraction steam drainage enthalpy.

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