A method for optimizing the calculation of coal-fired power output in power systems

Abstract

The present invention provides a method for optimizing the output of coal-fired thermal power in an electric power system, which relates to the technical field of electric power system planning and design. The output of coal-fired thermal power is adjusted by using a pumped storage power station, so as to achieve the purpose of saving coal. The technology includes, under the condition of obtaining the output capacity of the coal-fired thermal power unit, taking the maximum difference in the amount of coal burned by the coal-fired thermal power before and after optimization as the objective function, taking the sum of the increased output at the trough position of the coal-fired thermal power load equal to the sum of the reduced output at the peak position divided by the quotient of the conversion efficiency of the pumped storage power station as a constraint condition, constructing an optimization calculation method, and ensuring the energy conversion balance of the pumped storage power station. The present invention can be effectively used in the calculation of power balance in the planning and design of the electric power system, the scale of pumped storage demand, the installed capacity of pumped storage, and the demonstration of continuous full-generation hours.

Description

Technical Field

[0001] The invention relates to the technical field of power system planning and design, in particular to a method for optimizing the calculation of coal-fired thermal power output in a power system. Background Art

[0002] Pumped-storage power stations, with their large capacity, long life, and mature technology, have become an indispensable means of regulation after the connection of new energy to the grid. It can not only effectively absorb surplus new energy electricity, reduce the phenomenon of wind and solar power abandonment, and replace thermal power generation, thereby directly reducing coal consumption; it can also play an important capacity support role in the power system, and reduce the unnecessary start-up time of thermal power units through flexible adjustment, further saving coal resources. In addition, purpose: Since pumped-storage power stations have the ability to pump water for energy storage and replace power generation, they can transfer the energy of coal-fired thermal power, increase coal-fired power output during the low-power demand period to store energy for pumped-storage power stations, and reduce coal-fired power output during the peak power demand period to use pumped-storage power stations to replace power generation, thereby achieving "peak shaving and valley filling" of coal-fired power output, thereby reducing the amount of coal burned in coal-fired power generation and improving the economic efficiency of power system operation.

[0003] There are currently few methods proposed for optimizing coal-fired power output. Some methods have been analyzed and implemented from a mathematical perspective, but no corresponding calculation methods have been proposed. They are mainly used for situations where the coal consumption curve is monotonically decreasing and the coal consumption curve is monotonically increasing, and it is difficult to optimize for complex coal consumption curves. The present invention focuses on proposing a method for optimizing the output of coal-fired thermal power in a power system. The output of coal-fired thermal power is optimized using mathematical analysis and efficient optimization methods, and the coal-saving benefits brought about by the optimized coal-fired power operating conditions of a pumped-storage power station are calculated. This method can be applied to different types of coal consumption curves and is not limited to monotonically decreasing or increasing. The proposed method can more accurately analyze and calculate the coal-saving benefits brought about by the optimized coal-fired power output of a pumped-storage power station, while improving the operating economy of coal-fired thermal power and the overall operating economy of the power system. It is an important innovation in current energy transformation technologies. Summary of the invention

[0004] The present invention provides a method for optimizing the calculation of coal-fired thermal power output in an electric power system, aiming to solve at least one technical problem existing in the prior art mentioned in the background technology.

[0005] The present invention provides the following technical solutions to achieve the above objectives:

[0006] A method for optimizing the output of coal-fired thermal power in a power system is provided. Under the condition that the output of the coal-fired thermal power unit before optimization in the power and electricity balance is obtained, the maximum difference in the amount of coal burned by the coal-fired thermal power before and after optimization is taken as the objective function, and the sum of the increased output at the trough position of the coal-fired thermal power load is equal to the sum of the reduced output at the peak position divided by the quotient of the conversion efficiency of the pumped storage power station is taken as a constraint condition to construct an optimization calculation method to obtain the output of the coal-fired thermal power after optimization. The optimization calculation method comprises the following steps:

[0007] A. Obtain the coal consumption-thermal power output rate curve and determine the minimum incremental rate point;

[0008] B. Construct a two-layer nested function based on step A. The outer layer is to identify the trough position and peak position of coal-fired thermal power output before optimization, and assume that the sum of the reduced output at the peak position of coal-fired thermal power output before optimization is the decision variable; the inner layer is to increase the output at the trough position of coal-fired thermal power output before optimization based on the minimum incremental rate point, continuously calculate to ensure the constraints, and establish the objective function with the largest difference in coal consumption before and after optimization.

[0009] Furthermore, the step A comprises:

[0010] 1) Collect data points of actual thermal power output rate and unit kilowatt-hour coal consumption, consider linear, n-order polynomial, exponential, logarithmic, and power function mathematical models to perform trend fitting on the data points, and select the trend fitting function with the best correlation as the unit kilowatt-hour coal consumption ~ thermal power output rate curve equation f(X) by comparing the correlation coefficients of different mathematical model fittings;

[0011] 2) Based on the unit kilowatt-hour coal consumption ~ thermal power output rate curve equation f(X), the coal consumption ~ thermal power output rate curve equation F(X) is obtained by combining the coal-fired thermal power startup capacity and thermal power output; the combined calculation steps are as follows:

[0012]

[0013] F(X)=10·Tout i f(X);

[0014] Among them, X is the thermal power output rate, that is, the percentage of thermal power output to the operating capacity NT, in %; Tout i is the thermal power output in the ith hour, in 10,000 kW; f(X) is the equation of the curve of coal consumption per unit of electricity ~ thermal power output rate, in g / kWh; F(X) is the equation of the curve of coal consumption ~ thermal power output rate, in kg / h; 10 is the unit conversion constant;

[0015] 3) Take the first-order and second-order derivatives of the coal-fired power output rate curve equation in turn, and solve the second-order derivative to obtain the inflection point of the coal-fired power output rate curve equation, that is, the minimum incremental rate point, recorded as Tdmin , in physical terms, it is also a thermal power output rate, with the unit being %.

[0016] Furthermore, the outer function of step B includes:

[0017] 1) Assuming that the sum of the reduced output at the peak position of coal-fired thermal power is the decision variable, the optimization cycle is month, week or day, and the optimization period is hour. Based on the output process of coal-fired thermal power before optimization, the maximum output of coal-fired thermal power before optimization and the minimum output of coal-fired thermal power before optimization are found period by period. The calculation formula is as follows:

[0018]

[0019] Among them, Tout_max is the maximum output of coal-fired power before optimization, in 10,000 kW; Tout_B i is the output of coal-fired thermal power in the i-th period before optimization, in 10,000 kW; m is the total number of hours in the optimization period, in h; imax is the hour number corresponding to the maximum output of coal-fired thermal power before optimization;

[0020]

[0021] Among them, Tout_mmin is the minimum output of coal-fired thermal power before optimization, in units of 10,000 kW; immin is the hour number corresponding to the minimum output of coal-fired thermal power before optimization;

[0022] 2) Based on the maximum output of coal-fired thermal power before optimization, it is assumed that the peak position is reduced to a certain thermal power output during the optimization period, and then the assumed decision variables can be obtained. The function is established by calculating hour by hour as follows:

[0023]

[0024] Among them, JC is the decision variable, that is, the sum of the output reduction at the peak position, in units of 10,000 kW; Tout_d is the reduced thermal power output value, in units of 10,000 kW; Tout_A i It is the optimized thermal power output in the i-th period, in 10,000 kW.

[0025] Furthermore, the inner function of step B includes: taking the minimum incremental rate point as the boundary, dividing the coal-fired thermal power output process before optimization into upper and lower parts, when the coal-fired thermal power output before optimization is greater than the thermal power output at the minimum incremental rate, that is, Tout_B i >NT*T min / 100, it is recorded as the upper section with large thermal power output; when the coal-fired thermal power output before optimization is less than the thermal power output at the minimum slight increase rate, that is, Tout_B i ≤NT*T min / 100, it is recorded as the lower section with low thermal power output; the slight increase rate corresponding to the thermal power output in each period is solved through the first-order derivative of the coal consumption-thermal power output rate curve equation, and the output is allocated after sorting from small to large.

[0026] The output distribution includes:

[0027] When the thermal power output rate of the lower part of the coal-fired thermal power output process before optimization is greater than the minimum slight increase rate point, the minimum value of the thermal power output of the lower part is taken as the lower limit, and the reduced thermal power output value Tout_d is taken as the upper limit. The binary method is used to calculate the increased thermal power output value Tout_u at the trough position. The calculation formula is as follows:

[0028]

[0029] Until the constraint condition that the sum of increased thermal power output is balanced with the sum of reduced thermal power output at peak positions after considering the conversion efficiency of pumped storage power stations is met, that is, JC′·α=JC; where JC′ is the sum of increased thermal power output at valley positions, in 10,000 kW; Tout_u is the increased thermal power output at valley positions, in 10,000 kW; α is the energy conversion efficiency of pumped storage, which is 0.75;

[0030] When the thermal power output rate of the lower part of the coal-fired thermal power output process before optimization is less than or equal to the minimum slight increase rate point, the thermal power output is increased in sequence from the coal-fired thermal power output before optimization with the smallest slight increase rate to the thermal power output rate of T dmin of thermal power output,

[0031] The optimized thermal power output calculation formula is as follows:

[0032] Tout_A i =NT·T dmin / 100;

[0033] The calculation formula for increasing the total thermal power output is as follows:

[0034]

[0035] Until the constraint condition of increasing the sum of thermal power output taking into account the conversion efficiency of the pumped storage power station and reducing the sum of thermal power output at the peak position is met, that is, JC'·α=JC.

[0036] Furthermore, the objective function of maximizing the difference in the amount of coal burned by coal-fired thermal power before and after optimization is established, and the decision variables of the outer layer assumptions and the corresponding reduced thermal power output value Tout_d are solved with the goal of maximizing the amount of coal saved. The calculation formula is as follows:

[0037]

[0038] Among them, ΔF is the amount of coal saved after thermal power output optimization relative to before optimization, in kg;

[0039] Repeat steps A and B to find the optimal value for reducing thermal power output Tout_d.

[0040] Furthermore, the method for solving the optimal method for reducing the thermal power output value Tout_d includes using a genetic algorithm or a successive approximation method for calculation.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The present invention proposes a method for calculating the output optimization of coal-fired thermal power in a power system, which has clear ideas and steps, and uses a mathematical analysis method to solve the optimized thermal power output, so that the physical meaning is clearer and easier to understand. The method fills the gap in the optimization of coal-fired thermal power output by pumped storage in the calculation of power balance, improves the calculation method and results of the coal-saving benefits of pumped storage, and provides a solid foundation for the demonstration of pumped storage power stations. The present invention can be effectively used in power balance calculations in power system planning and design, pumped storage demand scale, pumped storage installed capacity, and continuous full-generation hours demonstration. It has great promotion value in the current and future periods of new power system power expansion optimization and the vigorous development of pumped storage. The method has obvious innovation and creativity, and is of great value to project production and scientific research. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Attached Figure 1 This is a conceptual diagram of coal-fired thermal power output optimization;

[0044] Attached Figure 2 It is a schematic diagram of the coal consumption per unit kilowatt-hour and thermal power output rate curve of a certain type of coal-fired power unit;

[0045] Attached Figure 3 It is a schematic diagram of the coal consumption-thermal power output rate curve of a certain type of coal-fired power unit;

[0046] Attached Figure 4 It is a schematic diagram of the first-order derivative of the coal consumption-thermal power output rate curve;

[0047] Attached Figure 5 It is a schematic diagram of the second-order derivative of the coal consumption-thermal power output rate curve;

[0048] Attached Figure 6 Schematic diagram of thermal power output process before and after optimization. DETAILED DESCRIPTION

[0049] To facilitate the understanding of the present invention, the present application will be described more comprehensively below with reference to the relevant drawings; the drawings show preferred embodiments of the present invention, but the present invention can be implemented in many different forms and is not limited to the embodiments described herein; on the contrary, the purpose of providing these embodiments is to enable a more thorough and comprehensive understanding of the disclosed content of the present invention.

[0050] It should be noted that the terms “vertical”, “horizontal”, “up”, “down”, “left”, “right” and similar expressions used in this document are only for illustrative purposes and do not represent the only implementation method.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which the present invention belongs; the terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the term "and / or" used herein includes any and all combinations of one or more related listed items.

[0052] Embodiment. A method for optimizing the output of coal-fired thermal power in a power system, referring to Figures 1 to 6 , using a pumped storage power station to adjust the output of coal-fired thermal power, so as to achieve the purpose of saving coal, under the condition of obtaining the output of the coal-fired thermal power unit before optimization in the power balance, taking the maximum difference in the coal consumption of coal-fired thermal power before and after optimization as the objective function, taking the sum of the increased output at the trough position of the coal-fired thermal power load considering the conversion efficiency of the pumped storage power station and the sum of the reduced output at the peak position as the constraint condition, constructing an optimization calculation method to obtain the optimized coal-fired thermal power output; the optimization calculation method includes the following steps: A, obtaining a coal consumption-thermal power output rate curve, and determining the minimum micro-increase rate point;

[0053] 1) Collect data points of actual thermal power output rate and unit kilowatt-hour coal consumption, consider linear, n-order polynomial, exponential, logarithmic, power function and other mathematical models to perform trend fitting on the data points, and select the trend fitting function with the best correlation as the unit kilowatt-hour coal consumption ~ thermal power output rate curve equation f(X) by comparing the correlation coefficients of different mathematical model fittings;

[0054] 2) Based on the unit kilowatt-hour coal consumption ~ thermal power output rate curve equation f(X), the coal consumption ~ thermal power output rate curve equation F(X) is obtained by combining the coal-fired thermal power startup capacity and thermal power output; the combined calculation steps are as follows:

[0055]

[0056] F(X)=10·Tout i f(X);

[0057] Among them, X is the thermal power output rate, that is, the percentage of thermal power output to the operating capacity NT, in %; Tout i is the thermal power output in the ith hour, in 10,000 kW; f(X) is the equation of the curve of coal consumption per unit of electricity ~ thermal power output rate, in g / kWh; F(X) is the equation of the curve of coal consumption ~ thermal power output rate, in kg / h; 10 is the unit conversion constant;

[0058] 3) Take the first-order and second-order derivatives of the coal-fired power output rate curve equation in turn, and solve the second-order derivative to obtain the inflection point of the coal-fired power output rate curve equation, that is, the minimum incremental rate point, recorded as T min , in physical terms, it is also a thermal power output rate, with the unit being %.

[0059] Based on step A, a two-layer nested function is constructed. The outer layer is used to identify the trough position and peak position of the coal-fired thermal power output before optimization, and the sum of the reduced output at the peak position of the coal-fired thermal power output before optimization is assumed to be the decision variable; the inner layer is used to increase the output at the trough position of the coal-fired thermal power output before optimization based on the minimum incremental rate point, and the constraints are continuously calculated to ensure that the constraints are met, so as to establish an objective function with the largest difference in coal consumption before and after optimization.

[0060] The outer function of step B includes:

[0061] Assuming that the sum of the reduced output at the peak position of coal-fired thermal power is the decision variable, the optimization cycle is month, week or day, and the optimization period is hour. Based on the output process of coal-fired thermal power before optimization, the maximum output of coal-fired thermal power before optimization and the minimum output of coal-fired thermal power before optimization are found period by period. The calculation formula is as follows:

[0062]

[0063] Among them, Tout_max is the maximum output of coal-fired power before optimization, in 10,000 kW; Tout_B i is the output of coal-fired thermal power in the i-th period before optimization, in 10,000 kW; m is the total number of hours in the optimization period, in h; imax is the hour number corresponding to the maximum output of coal-fired thermal power before optimization;

[0064]

[0065] Among them, Tout_min is the minimum output of coal-fired thermal power before optimization, in units of 10,000 kW; imin is the hour number corresponding to the minimum output of coal-fired thermal power before optimization;

[0066] Based on the maximum output of coal-fired thermal power before optimization, it is assumed that the peak position is reduced to a certain thermal power output during the optimization period, and then the assumed decision variables can be obtained. The function is established by calculating hour by hour as follows:

[0067]

[0068] Among them, JC is the decision variable, that is, the sum of the output reduction at the peak position, in units of 10,000 kW; Tout_d is the reduced thermal power output value, in units of 10,000 kW; Tout_A i It is the optimized thermal power output in the i-th period, in 10,000 kW.

[0069] The inner function of step B includes:

[0070] Taking the minimum incremental rate point as the boundary, the coal-fired thermal power output process before optimization is divided into upper and lower parts. When the coal-fired thermal power output before optimization is greater than the thermal power output at the minimum incremental rate, that is, Tout_B i >NT*T min / 100, it is recorded as the upper section with large thermal power output; when the coal-fired thermal power output before optimization is less than the thermal power output at the minimum slight increase rate, that is, Tout_B i ≤NT*T min / 100, it is recorded as the lower section with low thermal power output; the slight increase rate corresponding to the thermal power output in each period is solved by the first-order derivative of the coal consumption-thermal power output rate curve equation, and the output is allocated after sorting from small to large; the output allocation includes:

[0071] When the thermal power output rate of the lower part of the coal-fired thermal power output process before optimization is greater than the minimum slight increase rate point, the minimum value of the thermal power output of the lower part is taken as the lower limit, and the reduced thermal power output value Tout_d is taken as the upper limit. The binary method is used to calculate the increased thermal power output value Tout_u at the trough position. The calculation formula is as follows:

[0072]

[0073] Until the constraint condition that the sum of increased thermal power output is balanced with the sum of reduced thermal power output at peak positions after considering the conversion efficiency of pumped storage power stations is met, that is, JC′·α=JC; where JC′ is the sum of increased thermal power output at valley positions, in 10,000 kW; Tout_u is the increased thermal power output at valley positions, in 10,000 kW; α is the energy conversion efficiency of pumped storage, which is 0.75;

[0074] When the thermal power output rate of the lower part of the coal-fired thermal power output process before optimization is less than or equal to the minimum slight increase rate point, the thermal power output is increased in sequence from the coal-fired thermal power output before optimization with the smallest slight increase rate to the thermal power output rate of T dmin of thermal power output,

[0075] The optimized thermal power output calculation formula is as follows:

[0076] Tout_A i =NT·T dmin / 100;

[0077] The calculation formula for increasing the sum of thermal power output is as follows:

[0078]

[0079] Until the constraint condition of increasing the sum of thermal power output and taking into account the conversion efficiency of pumped storage power stations and reducing the sum of thermal power output at peak locations is met, that is, JC′·α=JC.

[0080] The objective function of maximizing the difference in the amount of coal burned by coal-fired thermal power before and after optimization is established, and the decision variables of the outer layer assumptions and the corresponding reduced thermal power output value Tout_d are solved with the goal of maximizing the amount of coal saved. The calculation formula is as follows:

[0081]

[0082] Among them, ΔF is the amount of coal saved after thermal power output optimization relative to before optimization, in kg;

[0083] Repeat steps A and B to solve the optimal thermal power output value Tout_d; find the maximum and minimum outputs time by time, that is, assuming that the maximum output in the optimization period is 0, starting from the first period of the optimization period, if the output of the next period is greater than the output of the previous period, the maximum output is the output of the next period, if it is less than or equal to, the maximum output remains unchanged; the same is true for the minimum output, assuming that the output of the first period in the optimization period is the minimum output, starting from the second period, if the output of the next period is less than the output of the previous period, the minimum output is the output of the next period, if it is greater than or equal to, the minimum output remains unchanged; continue to judge time by time until the last period, and the maximum and minimum outputs in the optimization period can be found.

[0084] The method for solving the optimal method for reducing the thermal power output value Tout_d includes using a genetic algorithm or a successive approximation method for calculation.

[0085] Application example. The main idea of ​​the present invention is to analyze and fit the unit kilowatt-hour coal consumption-thermal power output rate curve according to the actual coal consumption and thermal power output rate of the coal-fired thermal power unit, and then analyze and obtain the coal consumption-thermal power output rate curve, and use the mathematical function analysis method to analyze the concavity of the coal consumption-thermal power output rate curve, solve the first-order derivative and second-order derivative of the function, analyze the key inflection point to obtain the minimum micro-increase rate point; on the basis of the thermal power output process before optimization, construct a two-layer nested calculation method to solve the thermal power output optimization, the outer layer is the peak output and valley output position identification of coal-fired thermal power, and it is assumed that the sum of the peak position reduction output is the decision variable, and the inner layer is to increase the coal-fired thermal power output at the valley output position according to the minimum micro-increase rate of mathematical analysis, and continuously optimize the trial calculation to ensure that the sum of the valley position increase output is equal to the sum of the peak position reduction output divided by the pumped storage conversion efficiency, that is, to ensure the balance of energy conversion of the pumped storage power station. Taking the maximum difference in the amount of coal burned before and after optimization as the objective function, the optimization algorithm is used to continuously assume and solve the outer decision variables, while ensuring the energy conversion balance of the pumped storage power station in the inner cycle, and then the optimized coal-fired thermal power output is obtained, such as Figure 1 The figure shows a conceptual diagram of thermal power output optimization. In general, it is divided into two steps: obtaining the coal consumption ~ thermal power output rate curve and mathematical analysis, and solving the thermal power optimization output calculation in two layers of nesting. The present invention has been applied in practice. Taking a certain power system as an example, according to the results of the power balance calculation before optimization, the coal-fired thermal power startup capacity of 63 million kW is obtained, with an optimization cycle of 7 days a week. First, the representative output rate and coal consumption rate data of the system's coal-fired thermal power units are collected, and the unit electricity coal consumption ~ thermal power output rate curve is fitted. See the details. Figure 2 As shown in the figure, the fitted unit kilowatt-hour coal consumption ~ thermal power output rate curve equation is: f(X) = -0.000247X 3 +0.0782X 2 -8.036X+557.05. Combined with the coal-fired thermal power generation capacity NT, the coal-fired power generation output rate curve equation is obtained, which is:

[0086]

[0087] Where: X is the thermal power output rate, that is, the percentage of thermal power output to the operating capacity, in %; Tout i is the thermal power output in the ith hour, in 10,000 kW; f(X) is the equation of the coal consumption per unit kilowatt-hour ~ thermal power output rate curve, in g / kWh; F(X) is the equation of the coal consumption ~ thermal power output rate curve, in kg / h.

[0088] The calculated coal consumption-thermal power output rate curve equation is:

[0089] F(X)=-0.156X 4 +49.3·X3 -5.06·10 3 ·X 2 +3.51·10 5 ·X, see the specific curve diagram Figure 3 .

[0090] Further mathematical analysis is performed on the coal consumption-thermal power output rate curve equation, and the first-order derivatives are calculated as follows:

[0091] F′(X)=-0.622X 3 +148·X 2 -1.01·10 4 ·X+3.51·10 5

[0092] The second-order derivative is: F″(X)=-1.867X 2 +296·X-1.01·10 4 , the first-order derivative and second-order derivative curves are shown in the attached Figure 4 and attached Figure 5 . Let the second-order derivative be F″(X 0 )=0, solve the inflection point, and the root obtained is the minimum incremental rate point X 0 =T dmin =50.144. This is the boundary point, the thermal power output rate is less than T dmin When the thermal power output rate is greater than T dmin When , the first-order derivative increases, that is, the slight increase rate increases with the increase of output rate.

[0093] The second step is to solve the thermal power optimization output by two-layer nesting. The main steps of the two-layer nesting solution are as follows:

[0094] (1) The outer layer is for the identification of peak output and valley position of coal-fired thermal power, and it is assumed that the sum of the reduced output at the peak position is the decision variable. Taking the week (or month or day) as the optimization cycle and the hour as the optimization period, based on the hourly thermal power output process before optimization, the maximum thermal power output and the minimum thermal power output before optimization are found in each period. The specific formula is:

[0095]

[0096] Where: Tout_max is the maximum thermal power output before optimization, 10,000 kW; Tout_B i is the thermal power output in the i-th period before optimization, 10,000 kW; m is the total number of hours in the optimization period, h; imax is the hour number corresponding to the maximum thermal power output before optimization.

[0097]

[0098] Where: Tout_min is the maximum thermal power output before optimization, in 10,000 kW; imin is the hour number corresponding to the maximum thermal power output before optimization; the other symbols have the same meanings as before.

[0099] On the basis of the maximum thermal power output before optimization, a certain step length is adopted to assume that the peak position is reduced to a certain thermal power output (hereinafter referred to as the reduced thermal power output value), and then the assumed decision variable, that is, the sum of the reduced output at the peak position, can be obtained. The specific calculation is calculated in sequence according to each time period, and the calculation formula is:

[0100]

[0101] Where: JC is the decision variable, i.e., the sum of the reduced output at the peak position, in 10,000 kW; Tout_d is the reduced thermal power output value, in 10,000 kW; Tout_A i is the optimized thermal power output in the i-th period, in 10,000 kW; the other symbols have the same meanings as before.

[0102] The inflection point T obtained by mathematical analysis dmin , with T dmin As the boundary, the thermal power output process before optimization is divided into upper and lower parts, that is, if Tout_B i >NT·T dmin , then it is the upper part with large output. On the contrary, if Tout_B i ≤NT·T dmin / 100, then it is the lower part with low output. For the upper and lower parts, based on the first derivative F′(X) of the coal consumption-thermal power output rate curve equation, the corresponding slight increase rate of thermal power output in each period is calculated, and they are sorted from small to large, and then the output is allocated on this basis. Then, they are sorted from small to large according to the slight increase rate, starting from the thermal power output before optimization with the smallest slight increase rate, and the thermal power output is increased to the thermal power output rate of T dmin The thermal power output of the optimized thermal power output is taken as the optimized thermal power output. The specific calculation formula of the optimized thermal power output is: Tout_A i =NT·T dmin / 100, until the constraint condition that the sum of increased thermal power output is balanced with the sum of reduced thermal power output at peak position after considering the conversion efficiency of pumped storage power station is met, that is, JC′·α=JC. At this time, the calculation formula for the sum of increased thermal power output in this section is:

[0103]

[0104] (3) Combined with the objective function of the optimization calculation, the decision variables of the outer layer assumption and the corresponding reduced thermal power output value Tout_d are obtained by optimization. The objective function of this optimization calculation is:

[0105]

[0106] Where: ΔF is the amount of coal saved after thermal power output optimization relative to before optimization, in kg. The optimal thermal power output reduction value Tout_d can be continuously solved by genetic algorithm or successive approximation method, and then the optimized thermal power output process can be obtained by repeating the above steps. The entire optimization process needs to fully consider the installed capacity and storage capacity constraints of pumped storage.

[0107] According to the above steps, the output process of thermal power after optimization in one week is shown in Figure 6 As shown, the corresponding amount of coal saving can be further calculated.

[0108] Obviously, the above is only a part of the embodiments of the present invention, not all of the embodiments. The above embodiments are not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and variations. Any combination, modification, equivalent replacement, improvement and all other embodiments that can be made by those of ordinary skill in the art within the spirit and principle of the present invention should be within the protection scope of the present invention.

Claims

1. A method for optimizing the output of coal-fired thermal power in a power system, characterized by: Under the condition of obtaining the output of the coal-fired thermal power unit before optimization in the power and electricity balance, taking the maximum difference in the amount of coal burned by the coal-fired thermal power before and after optimization as the objective function, taking the sum of the increased output at the trough position of the coal-fired thermal power load and the sum of the reduced output at the peak position after considering the conversion efficiency of the pumped storage power station as the constraint condition, an optimization calculation method is constructed to obtain the output of the coal-fired thermal power after optimization; the optimization calculation method comprises the following steps: A. Collect statistical data on coal consumption per unit of electricity and statistical data on unit thermal power output rate to obtain the curve equation of coal consumption per unit of electricity ~ thermal power output rate. Based on the curve equation of coal consumption per unit of electricity ~ thermal power output rate f(X), the curve equation of coal consumption ~ thermal power output rate F(X) is obtained by combining the coal-fired thermal power startup capacity and thermal power output; the combined calculation steps are as follows: F(X)=10·Tout i f(X); where X is the thermal power output rate, that is, the percentage of thermal power output to the operating capacity NT, in %; Tout i is the thermal power output in the ith hour, in 10,000 kW; f(X) is the equation of the curve of coal consumption per unit of electricity ~ thermal power output rate, in g / kWh; F(X) is the equation of the curve of coal consumption ~ thermal power output rate, in kg / h; 10 is the unit conversion constant; Solve for the point where the second-order derivative of the coal consumption-thermal power output rate curve is zero, and obtain the minimum incremental rate point; B. Construct a two-layer nested function based on step A. The outer layer is for identifying the peak and valley output positions of coal-fired thermal power plants, and assumes that the sum of the reduced output at the peak position is the decision variable. The inner layer increases the coal-fired thermal power output at the valley output position according to the minimum incremental rate of mathematical analysis, and continuously optimizes the trial calculation to ensure that the sum of the increased output at the valley position is equal to the sum of the reduced output at the peak position divided by the pumped storage conversion efficiency, that is, to ensure the balance of energy conversion of the pumped storage power station. The maximum difference in the amount of coal burned by coal-fired thermal power before and after optimization is taken as the objective function. The decision variables of the outer layer are continuously assumed and solved through the optimization algorithm, while ensuring the energy conversion balance of the pumped storage power station in the inner cycle, and then the optimized coal-fired thermal power output is obtained.

2. The method for optimizing the output of coal-fired thermal power in a power system according to claim 1, characterized in that: The step A comprises: 1) Collect data points of actual thermal power output rate and unit kilowatt-hour coal consumption, consider linear, n-order polynomial, exponential, logarithmic, and power function mathematical models to perform trend fitting on the data points, and select the trend fitting function with the best correlation as the unit kilowatt-hour coal consumption ~ thermal power output rate curve equation f(X) by comparing the correlation coefficients of different mathematical model fittings; 2) Take the first-order and second-order derivatives of the coal-fired power output rate curve equation in turn, and solve the second-order derivative to obtain the inflection point of the coal-fired power output rate curve equation, that is, the minimum incremental rate point, recorded as T dmin , in physical terms, it is also a thermal power output rate, with the unit being %.

3. The method for optimizing the output of coal-fired thermal power in a power system according to claim 2, characterized in that: The outer function of step B includes: 1) Assuming that the sum of the reduced output at the peak position of coal-fired thermal power is the decision variable, the optimization cycle is month, week or day, and the optimization period is hour. Based on the output process of coal-fired thermal power before optimization, the maximum output of coal-fired thermal power before optimization and the minimum output of coal-fired thermal power before optimization are found period by period. The calculation formula is as follows: Among them, Tout_max is the maximum output of coal-fired power before optimization, in 10,000 kW; Tout_B i is the output of coal-fired thermal power in the i-th period before optimization, in 10,000 kW; m is the total number of hours in the optimization period, in h; imax is the hour number corresponding to the maximum output of coal-fired thermal power before optimization; Among them, Tout_min is the minimum output of coal-fired thermal power before optimization, in units of 10,000 kW; imin is the hour number corresponding to the minimum output of coal-fired thermal power before optimization; 2) Based on the maximum output of coal-fired thermal power before optimization, it is assumed that the peak position is reduced to a certain thermal power output during the optimization period, and then the assumed decision variables can be obtained. The function is established by calculating hour by hour as follows: Among them, JC is the decision variable, that is, the sum of the reduced output at the peak position, in 10,000 kW; Tout_d is the reduced thermal power output value, in 10,000 kW; Tout_A i It is the optimized thermal power output in the i-th period, in 10,000 kW.

4. The method for optimizing the output of coal-fired thermal power in a power system according to claim 2, characterized in that: The inner function of step B includes: Taking the minimum incremental rate point as the boundary, the coal-fired thermal power output process before optimization is divided into upper and lower parts. When the coal-fired thermal power output before optimization is greater than the thermal power output at the minimum incremental rate, that is, Tout_B i >NT*T dmin / 100, it is recorded as the upper section with large thermal power output; when the coal-fired thermal power output before optimization is less than the thermal power output at the minimum slight increase rate, that is, Tout_B i ≤NT*T dmin / 100, recorded as the lower section with small thermal power output; through the first-order derivative of the coal consumption-thermal power output rate curve equation, solve the corresponding slight increase rate of thermal power output in each period, sort them from small to large, and distribute the output; The output distribution includes: When the thermal power output rate of the lower part of the coal-fired thermal power output process before optimization is greater than the minimum slight increase rate point, the minimum value of the thermal power output of the lower part is taken as the lower limit, and the reduced thermal power output value Tout_d is taken as the upper limit. The binary method is used to calculate the increased thermal power output value Tout_u at the trough position. The calculation formula is as follows: Until the constraint condition that the sum of increased thermal power output is balanced with the sum of reduced thermal power output at peak positions after considering the conversion efficiency of pumped storage power stations is met, that is, JC′·α=JC; where JC′ is the sum of increased thermal power output at valley positions, in 10,000 kW; Tout_u is the increased thermal power output at valley positions, in 10,000 kW; α is the energy conversion efficiency of pumped storage, which is 0.75; When the thermal power output rate of the lower part of the coal-fired thermal power output process before optimization is less than or equal to the minimum slight increase rate point, the thermal power output is increased in sequence from the coal-fired thermal power output before optimization with the smallest slight increase rate to the thermal power output rate of T dmin of thermal power output, The optimized thermal power output calculation formula is as follows: All_A i =NT·T dmin / 100; The calculation formula for increasing the sum of thermal power output is as follows: Until the constraint condition of increasing the sum of thermal power output and taking into account the conversion efficiency of pumped storage power stations and reducing the sum of thermal power output at peak locations is met, that is, JC′·α=JC.

5. The method for optimizing the output of coal-fired thermal power in a power system according to claim 4, characterized in that: The objective function of maximizing the difference in coal consumption before and after optimization is established. The decision variables of the outer assumption and the corresponding reduction in thermal power output value Tout_d are solved with the goal of maximizing coal saving. The calculation formula is as follows: Among them, ΔF is the amount of coal saved after thermal power output optimization relative to before optimization, in kg; Repeat steps A and B to find the optimal value for reducing thermal power output Tout_d.

6. The method for optimizing the output of coal-fired thermal power in a power system according to claim 5, characterized in that: The method for solving the optimal method for reducing the thermal power output value Tout_d includes using a genetic algorithm or a successive approximation method for calculation.

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