Variable-speed pumped storage and wind-solar combined regulation and control operation method based on nonlinear programming

Abstract

The invention discloses a variable-speed pumped storage and wind-light combined regulation and control operation method based on nonlinear programming, and belongs to the technical field of energy regulation and control. A variable-speed pumped storage and wind-solar combined operation model with minimum operation cost of each unit, minimum wind and light curtailment amount and minimum pollutant emission as targets is constructed, the minimum wind and light curtailment amount is converted into penalty cost, the minimum pollutant emission amount is converted into pollutant treatment cost to be counted into total cost, and finally, the total cost is minimum as a target. And the stable operation condition of each unit is taken as a constraint condition, and the objective function is solved through a nonlinear programming method to obtain the optimal operation method for combined regulation and control, so that not only is the wind and light absorption effect improved, but also economy and environmental protection are considered, and the obtained combined regulation and control method is relatively high in reliability.

Description

Technical Field

[0001] The present invention relates to the technical field of energy regulation, and specifically, to a variable-speed pumped storage and wind-solar combined regulation operation method based on nonlinear programming. Background Art

[0002] Under the background of "carbon peak" and "carbon neutrality", the proportion of clean energy such as wind and solar power connected to the power grid is increasing continuously. However, they are intermittent and random power sources. Once connected to the power grid on a large scale, they will pose a huge threat to the stability of the power grid. As a mature energy storage technology, pumped storage is an important means to alleviate the consumption of new energy. The pumped storage unit has two working modes: power generation and pumping. Its operation mode is flexible, which can provide rotational reserve capacity for the power system and reduce the impact on power grid dispatching caused by the uncertainty of new energy generation such as wind and solar power. Variable-speed pumped storage with high flexibility and fast responsiveness has become the forefront direction of the development in the field of pumped storage today. Compared with traditional pumped storage power stations, variable-speed pumped storage can more accurately adjust power dynamically according to the grid demand, optimize the energy conversion process, reduce losses, thereby reducing mechanical wear, extending the equipment life, and reducing operation and maintenance costs, and improving the economy with its precise regulation technology.

[0003] In addition to using energy storage, relying on the complementary characteristics between thermal power and wind and solar power can also suppress the volatility of wind and solar power output to a certain extent. However, it cannot completely solve the problem of wind and solar power consumption. At this time, energy storage needs to be introduced. As the most economical and mature ideal high-quality power source at present, pumped storage is the best choice to participate in the combined regulation of wind, solar and thermal power. In the wind-solar-thermal-pumped storage combined operation system, how to reasonably allocate each part to make the pumped storage and various power sources operate coordinately and jointly regulate, so as to minimize the uncertainty of wind and solar power output is the key point of the research, which also reflects the importance of the combined regulation strategy. In current research, traditional pumped storage is mostly used in the wind-solar-thermal power system. How to make full use of the advantages of variable-speed pumped storage and add it to the wind-solar-thermal power system to participate in the combined regulation is a difficult problem that needs attention and solution.

[0004] Chinese Patent, Publication No.: CN119419778A, Publication Date: February 11, 2025, discloses a short-term combined dispatching method for water, wind, light and energy storage considering variable-speed pumped storage units. Through the combined application of virtual power plants, Latin hypercube sampling and synchronous back substitution reduction algorithms, the uncertain factors in the dispatching of distributed wind and light power plants are quantified to generate a series of typical deterministic scenario combinations. Then, based on the variable-speed pumped storage unit strategy, the daily output plan of the unit is flexibly adjusted within the allowable output variation range to reduce the peak-valley difference of the grid load. Finally, with the goal of minimizing the number of unit starts, the management of the centralized control center of multiple pumped storage power plants is guided to achieve the optimal unit combination among power plants, and necessary standby capacity units are reserved for the power grid. Although it suppresses the volatility of wind and light output to a certain extent, it cannot completely solve the problem of wind and light consumption. Summary of the Invention

[0005] Aiming at the problem that the existing combined regulation method has a poor effect on solving the problem of wind and light consumption by using the complementary characteristics between energy storage, thermal power and wind and light, the present invention provides a combined regulation and operation method for variable-speed pumped storage and wind and light based on nonlinear programming. By introducing external energy storage, the variable-speed pumped storage participates in the combined regulation of wind, light and thermal power. By constructing a combined operation model of variable-speed pumped storage and wind and light with the goals of minimizing the operating cost of each unit, minimizing the curtailment of wind and light, and minimizing the pollutant emissions, and converting the minimum curtailment of wind and light into penalty costs and the minimum pollutant emissions into pollutant treatment costs and including them in the total cost, finally, with the goal of minimizing the total cost and taking the stable operating conditions of each unit as the constraint conditions, the optimal combined regulation operation method is obtained by solving the objective function through the nonlinear programming method. It not only improves the effect of wind and light consumption, but also takes into account economy and environmental protection at the same time, and the obtained combined regulation method has high reliability.

[0006] In a first aspect, a technical solution provided in an embodiment of the present invention is: A combined regulation and operation method for variable-speed pumped storage and wind and light based on nonlinear programming, including the following steps: S1. Collect relevant parameters of each unit, wind and light output data, and load data to construct a combined operation model of variable-speed pumped storage and wind and light, construct an objective function with the goals of minimizing the operating cost, minimizing the curtailment of wind and light, and minimizing the pollutant emissions, and calculate the total cost during combined operation; S2. Construct unit stable operation constraints, wind and light output constraints, and power balance constraints with the goal of the stable combined operation of variable-speed pumped storage and wind and light; S3. The objective function is solved based on the nonlinear programming method on the basis of the constraint conditions, that is, the total cost, to obtain the optimal combined regulation operation method for variable-speed pumped storage and wind and light.

[0007] In this solution, by introducing external energy storage and involving variable-speed pumped storage in the combined regulation of wind, light, and thermal power, it is possible to better absorb wind and light power generation, reduce the phenomena of wind and light abandonment, improve the utilization rate of renewable energy, and promote the development of clean energy; with the goal of minimizing the total cost, by optimizing the operation strategy, the additional cost during the combined operation of wind and light power generation and the pumped storage system is reduced, improving economic benefits; by constructing the constraint conditions for the combined operation of variable-speed pumped storage and wind and light, the system is ensured to remain stable during operation, reducing the uncertainty brought by the volatility of wind and light power generation and enhancing the reliability of the power grid.

[0008] Preferably, in S1, the total cost includes the operating cost of thermal power units, the operating cost of variable-speed pumped storage units, the penalty cost for wind and light abandonment, and the pollution control cost.

[0009] In this solution, by considering the operating costs of each unit in the combined regulation, the pollution control costs of the pollutants generated during the operation of each unit, and the penalty costs for wind and light abandonment, all the objects to be regulated during the combined regulation are fully considered, providing a data basis for subsequent optimization goals of minimizing operating costs, minimizing wind and light abandonment, and minimizing pollutant emissions.

[0010] Preferably, the operating cost of the thermal power unit is the sum of the coal consumption cost, start-up cost, and shutdown cost of the thermal power unit; the coal consumption cost of the thermal power unit is the sum of the values obtained by multiplying the power generation power of each time period during the working period of the thermal power unit by the coal consumption cost coefficient; The start-up cost of the thermal power unit is the sum of the values obtained by multiplying the number of times the thermal power unit changes from the shutdown state to the operating state during the working period of the thermal power unit by the single start-up cost of the thermal power unit; The shutdown cost of the thermal power unit is the sum of the values obtained by multiplying the number of times the thermal power unit changes from the operating state to the shutdown state during the working period of the thermal power unit by the single shutdown cost of the thermal power unit.

[0011] In this solution, by analyzing the types of operating costs generated in the thermal power unit and decomposing the operating cost of the thermal power unit into coal consumption cost, start-up cost, and shutdown cost, it is possible to more clearly understand the proportion of each cost in the total cost, providing a basis for subsequent cost control. For example, after clarifying the sources of each cost, the operation strategy of the thermal power unit can be optimized accordingly. For example, reducing the frequency of start-stop to reduce start-up and shutdown costs, or adjusting the power generation power to reduce coal consumption costs, thereby improving the operation efficiency; by analyzing the cost composition, the links with higher costs can be identified and corresponding measures can be taken to reduce costs. For example, optimizing the unit start-stop plan or improving the coal combustion efficiency, thereby enhancing the economic benefits of the thermal power unit.

[0012] Preferably, the pollution control cost is calculated based on the types of pollutants, the emissions of the corresponding pollutant types, and the corresponding treatment costs; The operating cost of the variable-speed pumped storage unit is the sum of the start-up costs of the pumping and power generation conditions during the working period of the variable-speed pumped storage unit; The curtailment penalty cost of wind power is calculated based on the curtailment power of wind power and the curtailment penalty cost coefficient during the working period; The curtailment penalty cost of photovoltaic power is calculated based on the curtailment power of photovoltaic power and the curtailment penalty cost coefficient during the working period.

[0013] In this solution, by analyzing the sources of pollutant treatment costs, the operating costs of each unit, the curtailment penalty costs of wind power and photovoltaic power, the composition and influencing factors of each cost can be clearly understood. After understanding the sources of costs and penalties, resource allocation can be optimized accordingly. For example, reducing pollutant emissions to lower treatment costs, or optimizing the consumption of wind and photovoltaic power to reduce curtailment penalty costs, thereby improving resource utilization efficiency; by analyzing the sources of costs and penalties, the links with higher costs can be identified and corresponding measures can be taken to reduce costs. For example, optimizing the operation strategy of variable-speed pumped storage units to reduce start-up costs, or improving the scheduling of wind and photovoltaic power to reduce curtailment penalty costs, thereby enhancing the overall economic benefits.

[0014] Preferably, in S2, the stable operation constraints of the unit include the constraints of variable-speed pumped storage units and the operation constraints of thermal power units.

[0015] In this solution, by constructing an objective function and related constraint conditions with the lowest operating cost, the least curtailment of wind and photovoltaic power, and the minimum pollutant emissions as the optimization objectives, the combined operation takes into account both economy and environmental protection, which is relatively comprehensive.

[0016] Preferably, the constraints of the variable-speed pumped storage unit include the output constraint of the variable-speed pumped storage unit, the operation state constraint, the storage capacity constraint, and the reservoir head constraint; The output constraint of the variable-speed pumped storage unit limits the power generation power and pumping power of the variable-speed pumped storage unit within the preset pumped storage operation power range; The operation state constraint limits that only the power generation state or the pumping state exists when the same variable-speed pumped storage unit is operating; The storage capacity constraint limits the water storage volume of the upper reservoir of the variable-speed pumped storage unit within the preset water storage volume range when the variable-speed pumped storage unit is operating; The reservoir head constraint limits the head size of the pumped storage power station within the preset head range at different time periods when the variable-speed pumped storage unit is working.

[0017] In this solution, by reasonably restricting the operating range and status of the unit, it is ensured that the variable-speed pumped-storage unit can quickly respond to the demand changes of the power system, enhancing the regulation ability and stability of the system; through the optimization of the constraint conditions, the additional losses and maintenance costs caused by the unit's overload, frequent status switching or improper reservoir management are reduced, thereby reducing the overall operating cost; by restricting the operating parameters of the unit, it is ensured that the variable-speed pumped-storage unit plays a stable regulating role in the power system, balancing the volatility of wind and solar power generation, and improving the reliability of the power system; through the reasonable design of the constraint conditions, the variable-speed pumped-storage unit can better cooperate with the operation of wind and solar power generation, reduce the phenomena of wind and light abandonment, and improve the utilization rate of renewable energy.

[0018] Preferably, the operating constraints of the thermal power unit include the output constraint and the ramp rate constraint of the thermal power unit; The thermal power output constraint limits the power generation power of the thermal power unit within the preset thermal power generation operating power range; The ramp rate constraint limits the maximum upward ramp rate and the maximum downward ramp rate of the thermal power unit.

[0019] In this solution, by setting clear boundary conditions for the operation of the thermal power unit, it helps to formulate a more scientific dispatching strategy, achieve the economic and stability goals of system operation, helps to ensure the safe, efficient and stable operation of the thermal power unit, thereby reducing the operating cost, while enhancing the regulation ability of the power system and the consumption ability of renewable energy, and providing a scientific basis for the optimal dispatching of the power system.

[0020] Preferably, the power balance equation of the power balance constraint is expressed as follows: P h,t +P wd,t +P pv,t +P g,t =P load,t +P p,t In the formula, P wd,t is the actual grid-connected power of wind power in period t; P pv,t is the actual grid-connected power of photovoltaic power generation in period t; P load,t is the total load in period t, P h,t is the power generation power of the thermal power unit; P g,t is the power generation power of the variable-speed pumped-storage unit; P p,t is the pumping power of the variable-speed pumped-storage unit.

[0021] In this solution, during the coordinated control of variable-speed pumped storage and wind-solar power, it is necessary to ensure the balance between the overall power generation and consumption. Therefore, the sum of the actual grid-connected power of wind power, the actual grid-connected power of photovoltaic power generation, the power generation of thermal power units, and the power generation of variable-speed pumped storage units should be equal to the sum of the pumping power of variable-speed pumped storage units and the total load, so as to ensure the stable operation among the units.

[0022] Preferably, the formula for the wind-solar power output constraint is expressed as follows: In the formula, P wdg,t , P pvg,t are the wind-solar power generation at time t, and P wd,t is the actual grid-connected power of wind power at time t; P pv,t is the actual grid-connected power of photovoltaic power generation at time t.

[0023] In this solution, by setting the upper and lower limits of wind-solar power output, the output ratio of wind-solar power generation and other power sources (such as thermal power, hydropower, pumped storage, etc.) can be reasonably allocated, avoiding resource waste and improving the overall energy utilization efficiency; setting the wind-solar power output constraint can combine the accommodation capacity of the power system to avoid wind-solar power generation exceeding the system load demand or transmission capacity, thereby reducing the phenomenon of wind and light abandonment and improving the utilization rate of renewable energy; by restricting the wind-solar power output, the demand for reserve capacity (such as the peak regulation cost of thermal power units) and grid regulation cost caused by the volatility of wind-solar power generation can be reduced, thereby reducing the overall operating cost of the system.

[0024] Preferably, in S3, based on the nonlinear programming method, the objective function, that is, the total cost, is solved on the basis of satisfying the constraint conditions to obtain the optimal operation method for the coordinated control of variable-speed pumped storage and wind-solar power, including the following steps: Construct the objective function C total , and the formula is expressed as follows: minC total = C h + C zl + C pg + C wd + C pv Among them, C h is the operating cost of thermal power units, C zl is the pollution control cost, C pg is the operating cost of variable-speed pumped storage units, C wd is the penalty cost for wind abandonment, C pv is the penalty cost for light abandonment; Construct a nonlinear programming solution model, using algorithm parameters, cost coefficients, and constraint condition parameters as model inputs, and using a preset initial point as the iteration starting point for calculation and output to obtain an approximate objective function value; Repeat the calculation steps with the approximate objective function value as the iteration starting point until the maximum number of iterations is reached, and output the optimal objective function value. Take the optimal output of thermal power units, the optimal output of variable-speed pumped storage units, and the optimal grid-connected power of wind and light corresponding to the optimal objective function value as the regulation reference values to obtain the best operation method for the joint regulation of variable-speed pumped storage and wind and light.

[0025] In this solution, the objective function is solved by using the nonlinear programming method. This method has the advantages of a wide application range, strong flexibility, and easy search for the global optimal solution. The original nonlinear optimization problem is decomposed into a series of quadratic programming sub-problems for approximate solution. In each iteration step, the constraint conditions are linearized at the current point, and a quadratic model of the approximate objective function is constructed to form a quadratic programming sub-problem. By solving this quadratic programming sub-problem, a new iteration point can be obtained, and then this process is continuously repeated until the convergence condition is met, so as to approach the optimal solution of the original nonlinear optimization problem.

[0026] Advantages of the present invention: (1) By introducing external energy storage and involving variable-speed pumped storage in the joint regulation of wind, light, and thermal power, the present invention can better absorb wind and light power generation, reduce the phenomenon of wind and light abandonment, improve the utilization rate of renewable energy, and promote the development of clean energy. (2) With the goal of minimizing the total cost, the present invention optimizes the operation strategy, reduces the additional cost during the joint operation of wind and light power generation and the pumped storage system, and improves the economic benefits. (3) By constructing the constraint conditions for the joint operation of variable-speed pumped storage and wind and light, the present invention ensures the stability of the system during operation, reduces the uncertainty brought by the volatility of wind and light power generation, and improves the reliability of the power grid.

[0027] The above description of the invention content is only an overview of the technical solution of the present invention. In order to understand the technical means of the present invention more clearly, it can be implemented according to the content of the specification. And in order to make the above and other objects, features, and advantages of the present invention more obvious and understandable, the following specific embodiments of the present invention are specifically given. Description of the Drawings

[0028] By reading the detailed description of the non-restrictive embodiments with reference to the following drawings, other features, objects, and advantages of the present invention will become more obvious. The drawings are only used for the purpose of showing the preferred embodiments and are not considered as limiting the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components.

[0029] Figure 1 It is a flowchart of the operation method for the joint regulation of variable-speed pumped storage and wind and light based on nonlinear programming of the present invention. Figure 2Flow chart for solving the objective function by using the nonlinear programming method in the present invention; Figure 3 Output curve of each unit on a typical spring day in the first embodiment of the present invention; Figure 4 Output curve of each unit on a typical spring day in the second embodiment of the present invention; Figure 5 Output curve of each unit on a typical summer day in the first embodiment of the present invention; Figure 6 Output curve of each unit on a typical summer day in the second embodiment of the present invention; Figure 7 Output curve of each unit on a typical autumn day in the first embodiment of the present invention; Figure 8 Output curve of each unit on a typical autumn day in the second embodiment of the present invention; Figure 9 Output curve of each unit on a typical winter day in the first embodiment of the present invention; Figure 10 Output curve of each unit on a typical winter day in the second embodiment of the present invention. Detailed implementation manners

[0030] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific implementation manners described herein are only the best embodiments of the present invention, which are only used to explain the present invention and do not limit the protection scope of the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0031] Before discussing the exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe the operations (or steps) as sequential processes, many of the operations (or steps) can be implemented in parallel, concurrently or simultaneously. In addition, the order of the operations can be rearranged. The process can be terminated when its operations are completed, but it can also have additional steps not included in the drawings; the process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0032] Embodiment: As Figure 1 shown, to solve the problem that the existing combined regulation method has a poor effect in solving the problem of wind and light accommodation by using the complementary characteristics between energy storage and thermal power and wind and light, this embodiment provides a variable-speed pumped storage and wind-light combined regulation operation method based on nonlinear programming, including the following steps: S1: Collect the relevant parameters, wind and light output data, and load data of each unit to construct a variable-speed pumped storage and wind-light combined operation model. Construct an objective function with the lowest operating cost, the least curtailment of wind and light, and the minimum pollutant emissions as the goals, and calculate the total cost during combined operation.

[0033] In this embodiment, the total cost includes the operating cost of thermal power units, the operating cost of variable-speed pumped storage units, the penalty cost for curtailment of wind and light, and the pollutant treatment cost.

[0034] By considering the operating costs of each unit in the combined regulation, the treatment costs of pollutants generated during the operation of each unit, and the penalty costs for curtailment of wind and light in this embodiment, all the objects that need to be regulated during combined regulation are fully considered, providing a data basis for subsequent optimization goals of minimizing operating cost, minimizing curtailment of wind and light, and minimizing pollutant emissions.

[0035] In this embodiment, the operating cost of the thermal power unit is the sum of the coal consumption cost, start-up cost, and shutdown cost of the thermal power unit. The specific formula is as follows: C h = C hm + C hq + C ht The coal consumption cost of the thermal power unit is the sum of the values obtained by multiplying the power generation power of each time period during the working period of the thermal power unit by the coal consumption cost coefficient. The specific formula is as follows: The start-up cost of the thermal power unit is the sum of the values obtained by multiplying the number of times the thermal power unit changes from the shutdown state to the operating state during the working period by the single start-up cost of the thermal power unit. The specific formula is as follows: The shutdown cost of the thermal power unit is the sum of the values obtained by multiplying the number of times the thermal power unit changes from the operating state to the shutdown state during the working period by the single shutdown cost of the thermal power unit. The specific formula is as follows: In the formula, C hm is the coal consumption cost of the thermal power unit; C hq is the start-up cost of the thermal power unit; C ht is the shutdown cost of the thermal power unit; T is the total number of time periods in the regulation cycle; u h,t is the operating state variable of the thermal power unit at time t, taking values of 0 or 1. When u h,t = 1, it means the unit is operating; when u h,t = 0, it means the unit is in the shutdown state; a h1 , a h2 , a h3is the coal consumption cost coefficient; s hq is the single start-up cost of the unit that becomes operational during period t; s ht is the single shutdown cost of the unit that becomes shutdown during period t.

[0036] In this embodiment, by analyzing the types of operating costs generated in thermal power units, the operating costs of thermal power units are decomposed into coal consumption costs, start-up costs, and shutdown costs, which can more clearly understand the proportion of each cost in the total cost and provide a basis for subsequent cost control. For example, after clarifying the sources of each cost, the operating strategy of thermal power units can be optimized accordingly. For example, reducing the frequency of start-up and shutdown to reduce start-up and shutdown costs, or reducing coal consumption costs by adjusting the power generation, thereby improving the operating efficiency; by analyzing the cost composition, the links with higher costs can be identified and corresponding measures can be taken to reduce costs. For example, optimizing the unit start-up and shutdown plan or improving the coal combustion efficiency, thereby enhancing the economic benefits of thermal power units.

[0037] In this embodiment, the pollutant treatment cost is calculated based on the types of pollutants, the emissions of the corresponding pollutant types, and the corresponding treatment costs. The main pollutants and their treatment costs are shown in Table 1: Table 1. Main pollutants and treatment costs generated by burning 1t of coal Pollutant m <![CDATA[Emission D m / kg]]> <![CDATA[Governance cost s zlm / yuan·kg-1]]> <![CDATA[CO2]]> 1731.00 0.13 <![CDATA[SO2]]> 1.25 6.00 <![CDATA[NO x > 8.00 8.00 Ash residue 130.00 0.22 The specific calculation formula for the pollutant treatment cost is as follows: In the formula, m is the type of pollutant; D m is the emission of the m-th pollutant; s zlm is the treatment cost of the m-th pollutant.

[0038] The operating cost of the variable-speed pumped-storage unit is the sum of the start-up costs of the pumping condition and the power generation condition during the working period of the variable-speed pumped-storage unit. The specific formula for the cost is as follows: C pg = C pstart + C gstart In the formula, C pstart is the start-up cost of the pumping condition; C gstart is the start-up cost of the power generation condition; s pstart is the single start-up cost of the unit in the pumping condition during period t; s gstart is the single start-up cost of the unit in the pumping condition during period t; u g,t and u p,t are the description coefficients of the operating conditions of the variable-speed pumped-storage unit, taking values of 0 or 1. When u g,t = 1, it means that the variable-speed pumped-storage unit is discharging water for power generation. When up,t When u = 1, it indicates that the variable-speed pumped storage unit is pumping water. When u g,t = u p,t = 0, it indicates that the unit is in an idle state.

[0039] The curtailment penalty cost of wind power is calculated based on the curtailment power of wind power and the curtailment penalty cost coefficient during the working period. The specific formula is as follows: In the formula, W wd,t is the curtailment power of wind power at time t; α wd is the curtailment penalty cost coefficient.

[0040] The curtailment penalty cost of photovoltaic power is calculated based on the curtailment power of photovoltaic power and the curtailment penalty cost coefficient during the working period. The specific formula is as follows: In the formula, W pv,t is the curtailment power of photovoltaic power at time t; α pv is the curtailment penalty cost coefficient.

[0041] In this embodiment, by analyzing the sources of pollutant treatment costs, the operating costs of each unit, the curtailment penalty costs of wind power, and the curtailment penalty costs of photovoltaic power, the composition of each cost and its influencing factors can be clearly understood. After understanding the sources of costs and penalties, resource allocation can be optimized accordingly. For example, reducing pollutant emissions to lower treatment costs, or optimizing the consumption of wind and photovoltaic power to reduce curtailment penalty costs, thereby improving resource utilization efficiency; by analyzing the sources of costs and penalties, the links with higher costs can be identified and corresponding measures can be taken to reduce costs. For example, optimizing the operation strategy of variable-speed pumped storage units to reduce start-up costs, or improving the scheduling of wind and photovoltaic power to reduce curtailment penalty costs, thereby enhancing the overall economic benefits.

[0042] S2: Construct unit stable operation constraints, wind and photovoltaic power output constraints, and power balance constraints with the stability of the combined operation of variable-speed pumped storage and wind and photovoltaic power as the goal.

[0043] In this embodiment, the unit stable operation constraints include variable-speed pumped storage unit constraints and thermal power unit operation constraints.

[0044] In this embodiment, by constructing relevant constraint conditions with the minimum operating cost, minimum curtailment of wind and photovoltaic power, and minimum pollutant emissions as the optimization goals, the combined operation takes into account both economic efficiency and environmental protection, which is relatively comprehensive.

[0045] In this embodiment, the variable-speed pumped storage unit constraints include pumped storage output constraints, operating state constraints, reservoir capacity constraints, and reservoir head constraints; The output constraint of the variable-speed pumped storage unit limits the power generation power and pumping power of the variable-speed pumped storage unit within the preset pumped storage operation power range. The specific formula is as follows: In the formula: P g,t and P p,t are the power generation power and pumping power of the variable-speed pumped storage unit at time t respectively; P gmin and P gmax are the minimum and maximum values of the power generation power of the variable-speed pumped storage unit respectively; P pmin and P pmax are the minimum and maximum values of the pumping power of the variable-speed pumped storage unit respectively.

[0046] The operation state constraint limits that only the power generation state or the pumping state exists when the same variable-speed pumped storage unit is operating. The specific formula is as follows: u p,t + u g,t ≤ 1 The reservoir capacity constraint limits the water storage volume of the upper reservoir of the variable-speed pumped storage unit within the preset water storage volume range when the variable-speed pumped storage unit is operating. The specific formula is as follows: In the formula, is the upper reservoir capacity of the variable-speed pumped storage unit at the t-th time period; η p,t is the pumping power-flow conversion coefficient of the unit under the pumping condition at time t; η g,t is the power generation power-flow conversion coefficient of the unit under the power generation condition at time t; P p,t-1 is the pumping power of the unit at the (t - 1)-th time period; P g,t-1 is the power generation power of the unit at the (t - 1)-th time period.

[0047] The specific calculation formulas of η p,t and η g,t are as follows: In the formula, ρ0 is the average density of water; g is the acceleration due to gravity; h av is the average head difference between the upper reservoir and the lower reservoir.

[0048] Therefore, the reservoir capacity constraint of the variable-speed pumped storage unit can be expressed as: In the formula, Q up,max and Q up,min are the maximum and minimum water storage volumes of the upper reservoir of the variable-speed pumped storage unit respectively; is the initial reservoir capacity of the upper reservoir of the unit; is the reservoir capacity of the upper reservoir of the variable-speed pumped storage unit at the end of the regulation operation cycle.

[0049] The head constraint of the reservoir limits the head of the pumped - storage power station within a preset head range during different periods when the variable - speed pumped - storage unit is operating. The specific formula is as follows: h t,min ≤h t ≤h t,max In the formula, h t,min is the minimum head that the pumped - storage power station should maintain at time t; h t,max is the maximum head that the pumped - storage power station should maintain at time t.

[0050] In this embodiment, by reasonably restricting the operation range and state of the unit, it is ensured that the variable - speed pumped - storage unit can quickly respond to the demand changes of the power system, enhancing the regulation ability and stability of the system; through the optimization of the constraint conditions, the additional losses and maintenance costs caused by the unit's over - load, frequent state switching, or improper reservoir management are reduced, thereby reducing the overall operation cost; by restricting the operation parameters of the unit, it is ensured that the variable - speed pumped - storage unit plays a stable regulation role in the power system, balancing the volatility of wind and solar power generation, and improving the reliability of the power system; through the reasonable design of the constraint conditions, the variable - speed pumped - storage unit can better cooperate with the operation of wind and solar power generation, reducing the phenomena of wind and light abandonment, and improving the utilization rate of renewable energy.

[0051] In this embodiment, the operating constraints of the thermal power unit include thermal power output constraints and ramp - rate constraints; The thermal power output constraint limits the power generation power of the thermal power unit within a preset thermal power generation operation power range. The specific formula is as follows: u h,t P hmin ≤P h,t ≤u h,t P hmax In the formula, P h,t is the power generation power of the thermal power unit at time t; P hmin is the minimum power generation power of the thermal power unit; P hmax is the maximum power generation power of the thermal power unit.

[0052] The ramp - rate constraint limits the maximum upward ramp - rate and the maximum downward ramp - rate of the thermal power unit. The specific formula is as follows: In the formula, are respectively the maximum upward ramp - rate and the maximum downward ramp - rate of the thermal power unit.

[0053] In this embodiment, clear boundary conditions are set for the operation of thermal power units, which helps to formulate a more scientific dispatching strategy, achieve the goals of economic and stable operation of the system, ensure the safe, efficient and stable operation of thermal power units, thereby reducing the operation cost, and at the same time enhancing the regulation ability of the power system and the consumption ability of renewable energy, providing a scientific basis for the optimal dispatching of the power system.

[0054] In this embodiment, the power balance equation of the power balance constraint is expressed as follows: P h,t +P wd,t +P pv,t +P g,t =P load,t +P p,t In the formula, P wd,t is the actual grid-connected power of wind power in period t; P pv,t is the actual grid-connected power of photovoltaic power generation in period t; P load,t is the total load in period t, P h,t is the power generation of the thermal power unit; P g,t is the power generation of the variable-speed pumped storage unit; P p,t is the pumping power of the variable-speed pumped storage unit.

[0055] In the process of jointly regulating variable-speed pumped storage and wind-solar in this embodiment, it is necessary to ensure the balance between the overall power generation and consumption power. Therefore, the sum of the actual grid-connected power of wind power, the actual grid-connected power of photovoltaic power generation, the power generation of the thermal power unit and the power generation of the variable-speed pumped storage unit should be equal to the sum of the pumping power of the variable-speed pumped storage unit and the total load, so as to ensure the stable operation between the units.

[0056] In this embodiment, the formula of the wind-solar output constraint is expressed as follows: In the formula, P wdg,t 、P pvg,t are the wind-solar power generation in period t, P wd,t is the actual grid-connected power of wind power in period t; P pv,t is the actual grid-connected power of photovoltaic power generation in period t.

[0057] In this embodiment, by setting the upper and lower limits of the wind and light output, the output ratio of wind and light power generation and other power sources (such as thermal power, hydropower, pumped storage, etc.) can be reasonably allocated, resource waste can be avoided, and the overall energy utilization efficiency can be improved; setting the wind and light output constraints can combine with the consumption capacity of the power system to avoid wind and light power generation exceeding the system load demand or transmission capacity, thereby reducing the phenomenon of wind and light abandonment and improving the utilization rate of renewable energy; by constraining the wind and light output, the standby capacity demand (such as the peak shaving cost of thermal power units) and grid regulation cost caused by the volatility of wind and light power generation can be reduced, thereby reducing the overall operation cost of the system.

[0058] S3: Solve the objective function, that is, the total cost, based on the nonlinear programming method under the constraint conditions to obtain the optimal operation method for the combined regulation of variable-speed pumped storage and wind and light.

[0059] In this embodiment, based on the nonlinear programming method, solve the objective function, that is, the total cost, under the constraint conditions to obtain the optimal operation method for the combined regulation of variable-speed pumped storage and wind and light, including the following steps: Construct the objective function C total , and the formula is as follows: minC total =C h +C zl +C pg +C wd +C pv Among them, C h is the operating cost of the thermal power unit, C zl is the pollution control cost, C pg is the operating cost of the variable-speed pumped storage unit, C wd is the penalty cost for wind abandonment, C pv is the penalty cost for light abandonment; Construct a nonlinear programming solution model, and the basic model formula is as follows: Take the algorithm parameters, cost coefficients, and constraint condition parameters as the model inputs, and use the preset initial point as the iteration starting point for calculation and output to obtain an approximate objective function value; Take the approximate objective function value as the iteration starting point and repeat the calculation steps until the maximum number of iterations is reached and output the optimal objective function value; Take the optimal output of the thermal power unit, the optimal output of the variable-speed pumped storage unit, and the optimal grid-connected power of wind and light corresponding to the optimal objective function value as the regulation reference values to obtain the optimal operation method for the combined regulation of variable-speed pumped storage and wind and light.

[0060] Specifically, since non-linear programming has multiple iterative optimization algorithms, such as the gradient descent method, quasi-Newton method, global optimization algorithm, etc., in this embodiment, the Sequential Quadratic Programming (SQP) is selected. This method approximately solves the original non-linear optimization problem by decomposing it into a series of Quadratic Programming (QP) sub-problems. In each iteration step, the SQP algorithm linearizes the constraint conditions at the current point and constructs a quadratic model of the approximate objective function to form a QP sub-problem. By solving this QP sub-problem, a new iteration point can be obtained, and then this process is continuously repeated until the convergence condition is met. In this way, the SQP algorithm can gradually approach the optimal solution of the original non-linear optimization problem.

[0061] The specific solution process is as follows, as Figure 2 shown: Step 1: Set algorithm parameters, such as the maximum number of iterations, maximum allowable error, etc., and input cost coefficients, constraint condition parameters, etc.

[0062] Step 2: Construct an objective function with the goal of minimizing the operating cost, minimizing the curtailment of wind and solar power, and minimizing the pollutant emissions.

[0063] Step 3: Initialize the objective function and select an initial point as the starting point for iteration.

[0064] Step 4: Construct and solve a quadratic programming sub-problem, that is, calculate the approximate objective function value and solve the output of thermal power units, the pumping power and generating power of variable-speed pumped storage units, and the actual grid-connected power of wind and solar power.

[0065] Step 5: Update the iteration point according to the approximate objective function value. If the maximum number of iterations is reached, stop the iteration and proceed to Step 6. If not, repeat Steps 4 and 5.

[0066] Step 6: Output the optimal solution, that is, the objective function value, the output of thermal power units, the output of variable-speed pumped storage units, and the actual grid-connected power of wind and solar power.

[0067] In this embodiment, the non-linear programming method is used to solve the objective function. This method has the advantages of a wide application range, strong flexibility, and easy search for the global optimal solution. By decomposing the original non-linear optimization problem into a series of quadratic programming sub-problems for approximate solution, in each iteration step, by linearizing the constraint conditions at the current point and constructing a quadratic model of the approximate objective function, a quadratic programming sub-problem is formed. By solving this quadratic programming sub-problem, a new iteration point can be obtained, and then this process is continuously repeated until the convergence condition is met, thereby approaching the optimal solution of the original non-linear optimization problem.

[0068] As a further supplement to this embodiment, the following scenario is taken as an example to further illustrate the present solution: Taking a certain area in the south as an example, four typical days in spring, summer, autumn and winter are selected for simulation verification on the MATLABR2020b platform. 24 time periods are formed at 1h intervals. The total installed capacity of thermal power units is 250MW, the total installed capacity of variable-speed pumped storage units is 5.6MW, the maximum number of iterations is 500, and two scenarios are set for comparison: Scenario 1 is the combined regulation and operation of variable-speed pumped storage and wind-solar power, and Scenario 2 does not include variable-speed pumped storage units.

[0069] First, the cost parameter settings are carried out. The specific parameter settings are shown in Table 2: Table 2. Cost parameter settings Cost parameter Value <![CDATA[a h1 > 0.002 <![CDATA[a h2 > 6.15 <![CDATA[a h3 > 380 <![CDATA[s hq (yuan / time)]]> 7000 <![CDATA[s ht (yuan / time)]]> 7000 <![CDATA[s pstart (yuan / time)]]> 1000 <![CDATA[s gstart (yuan / time)]]> 1000 <![CDATA[α wd (Yuan / MWh)]]> 684 <![CDATA[α pv (yuan / MWh)]]> 840 Set the constraint condition parameters. The specific parameter settings are shown in Table 3: Table 3. Constraint condition parameter settings Parameter Value <![CDATA[Q up,max (Ten thousand m 3 )]]> 666.60 <![CDATA[Q0 up (Ten thousand m 3 )]]> 333.30 <![CDATA[h t,min (m)]]> 67.4 <![CDATA[h t,max (m)]]> 87.4 Based on the SQP algorithm of nonlinear programming, solve the combined regulation and operation model of variable-speed pumped storage and wind-solar power to obtain the combined operation strategy, that is, the output curves of each unit within 24 hours of a day in Scenario 1, and compare it with Scenario 2. The specific comparison results are as Figures 3 - 10 shown: Figure 3 It is the output curve diagram of each unit on a typical spring day in Scenario 1; Figure 4 It is the output curve diagram of each unit on a typical spring day in Scenario 2; Figure 5 It is the output curve diagram of each unit on a typical summer day in Scenario 1; Figure 6 It is the output curve diagram of each unit on a typical summer day in Scenario 2; Figure 7 It is the output curve diagram of each unit on a typical autumn day in Scenario 1; Figure 8 It is the output curve diagram of each unit on a typical autumn day in Scenario 2; Figure 9 It is the output curve diagram of each unit on a typical winter day in Scenario 1; Figure 10 It is the output curve diagram of each unit on a typical winter day in Scenario 2.

[0070] According to the comparison results, in Scheme 1, during three time periods of 1:00 - 5:00, 14:00 - 15:00, and 22:00 - 23:00 in a day, variable-speed pumped storage is used for pumping. At this time, the load demand is not high. The variable-speed pumped storage unit consumes some curtailed wind and solar power through pumping and stores it. During the peak load time periods of 8:00 - 9:00, 11:00 - 13:00, and 17:00 - 18:00, it discharges to respond to a certain load demand, so as to achieve the purpose of promoting the consumption of wind and solar energy. However, due to the differences in seasons and weather, the output of wind and solar energy is different. Therefore, there are slight differences in the pumping time periods and power generation time periods of the variable-speed pumped storage unit. To sum up, in this embodiment, Scheme 1 has a better effect on the consumption of wind and solar energy, that is, the investment of the variable-speed pumped storage unit can achieve the effect of increasing the wind and solar energy consumption rate by 3.718%.

[0071] Then, a cost analysis is carried out on Scheme 1 and Scheme 2. The specific cost comparison results are shown in Table 4 as follows: Table 4. Comparison of Costs for a Typical Day As can be seen from the above table, the cost of Scheme 1 with the variable-speed pumped storage unit is saved by 0.1656×10 7 yuan compared with Scheme 2 without the variable-speed pumped storage unit. This is because the investment of the variable-speed pumped storage unit can better consume wind and solar energy, reduce the operating cost of thermal power units, and the cost of hydropower is low. Therefore, the cost of Scheme 1 is lower, which verifies that the total system cost can be better reduced after adding the variable-speed pumped storage unit.

[0072] It can be seen from the above embodiments that at least the following substantial effects are achieved: (1) By introducing external energy storage in the present invention and having variable-speed pumped storage participate in the joint regulation of wind, solar, and thermal power, it can better consume wind and solar power generation, reduce the phenomenon of curtailed wind and solar energy, improve the utilization rate of renewable energy, and promote the development of clean energy; (2) With the goal of minimizing the total cost, the present invention optimizes the operation strategy to reduce the additional cost during the joint operation of wind and solar power generation and the pumped storage system, thereby improving the economic benefits; (3) By constructing the constraint conditions for the joint operation of variable-speed pumped storage and wind and solar energy, the present invention ensures the stability of the system during operation, reduces the uncertainty brought by the volatility of wind and solar power generation, and improves the reliability of the power grid.

[0073] The above-described specific embodiments are the preferred embodiments of the method for jointly regulating the operation of variable-speed pumped storage and wind and solar energy based on nonlinear programming of the present invention, and do not limit the specific implementation scope of the present invention. The scope of the present invention includes but is not limited to this specific embodiment. Any equivalent changes made in accordance with the shape and structure of the present invention are within the protection scope of the present invention.

Claims

1. A method for coordinated operation control of variable-speed pumped storage and wind-solar power based on nonlinear programming, characterized in that: It includes the following steps: S1. Collect the relevant parameters, wind and light output data, and load data of each unit to construct a variable-speed pumped storage and wind-light combined operation model. Construct an objective function with the lowest operating cost, the least curtailment of wind and light, and the minimum pollutant emissions as the goals, and calculate the total cost during combined operation; S2. Construct unit stable operation constraints, wind and light output constraints, and power balance constraints with the stability of variable-speed pumped storage and wind-light combined operation as the goal; S3. Solve the objective function, that is, the total cost, based on the nonlinear programming method under the constraint conditions to obtain the optimal operation method for the combined regulation of variable-speed pumped storage and wind and light.

2. The operation method for the combined regulation of variable-speed pumped storage and wind and light based on nonlinear programming according to claim 1, characterized in that: In S1, the total cost includes the operating cost of thermal power units, the operating cost of variable-speed pumped storage units, the curtailment penalty cost of wind and light, and the pollutant treatment cost.

3. The operation method for the combined regulation of variable-speed pumped storage and wind and light based on nonlinear programming according to claim 2, characterized in that: The operating cost of the thermal power unit is the sum of the coal consumption cost, start-up cost, and shutdown cost of the thermal power unit; The coal consumption cost of the thermal power unit is the sum of the values obtained by multiplying the power generation power of each time period during the working period of the thermal power unit by the coal consumption cost coefficient; The start-up cost of the thermal power unit is the sum of the values obtained by multiplying the number of times the thermal power unit changes from the shutdown state to the operating state during the working period by the single start-up cost of the thermal power unit; The shutdown cost of the thermal power unit is the sum of the values obtained by multiplying the number of times the thermal power unit changes from the operating state to the shutdown state during the working period by the single shutdown cost of the thermal power unit.

4. The operation method for the combined regulation of variable-speed pumped storage and wind and light based on nonlinear programming according to claim 2, characterized in that: The pollutant treatment cost is calculated based on the types of pollutants, the emissions of the corresponding pollutant types, and the corresponding treatment costs; The operating cost of the variable-speed pumped storage unit is the sum of the start-up costs of the pumping condition and the power generation condition during the working period of the variable-speed pumped storage unit; The curtailment penalty cost of wind is calculated based on the curtailment power of wind and the curtailment penalty cost coefficient during the working period; The curtailment penalty cost of light is calculated based on the curtailment power of light and the curtailment penalty cost coefficient during the working period.

5. The operation method for the combined regulation of variable-speed pumped storage and wind and light based on nonlinear programming according to claim 1, characterized in that: In S2, the unit stable operation constraints include variable-speed pumped storage unit constraints and thermal power unit operation constraints.

6. The operation method for the combined regulation of variable-speed pumped storage and wind and light based on nonlinear programming according to claim 5, characterized in that: The variable-speed pumped storage unit constraints include variable-speed pumped storage unit output constraints, operation state constraints, reservoir capacity constraints, and reservoir head constraints; The variable-speed pumped storage unit output constraints limit the power generation power and pumping power of the variable-speed pumped storage unit within the preset pumped storage operation power range; The operation state constraints limit that only the power generation state or the pumping state exists when the same variable-speed pumped storage unit is operating; The reservoir capacity constraint limits the water storage in the upper reservoir of the variable-speed pumped-storage unit within a preset water storage range during the operation of the variable-speed pumped-storage unit; The reservoir head constraint limits the head size within a preset head range during different time periods when the pumped-storage power station is operating with the variable-speed pumped-storage unit.

7. The method for jointly regulating and controlling variable-speed pumped storage and wind-solar based on nonlinear programming according to claim 5, wherein: The operating constraints of the thermal power unit include the output constraint and the ramp rate constraint of the thermal power unit; The thermal power output constraint limits the power generation power of the thermal power unit within a preset thermal power generation operating power range; The ramp rate constraint limits the maximum upward ramp rate and the maximum downward ramp rate of the thermal power unit.

8. The method for jointly regulating and controlling variable-speed pumped storage and wind-solar based on nonlinear programming according to claim 1, wherein: The power balance equation of the power balance constraint is expressed as follows: P h,t +P wd,t +P pv,t +P g,t =P load,t +P p,t where P wd,t is the actual grid-connected power of wind power in the t period; P pv,t is the actual grid-connected power of photovoltaic power generation in the t period; P load,t is the total load during period t, P h,t is the power generation of thermal power units; P g,t is the power generation of variable-speed pumped storage units; P p,t is the pumping power of variable-speed pumped storage units.

9. The method for jointly regulating and controlling variable-speed pumped storage and wind-solar based on nonlinear programming according to claim 1, wherein: The formula of the wind-solar output constraint is expressed as follows: Where, P wdg,t , P pvg,t are the wind and solar power generation powers in period t, and P wd,t is the actual grid-connected wind power in period t; P pv,t is the actual grid-connected photovoltaic power in period t.

10. The method for jointly regulating and controlling variable-speed pumped storage and wind-solar based on nonlinear programming according to claim 1, wherein: In S3, based on the nonlinear programming method, the objective function, that is, the total cost, is solved on the basis of satisfying the constraint conditions to obtain the best operation method for jointly regulating and controlling variable-speed pumped storage and wind-solar, including the following steps: Construct the objective function C total , which is expressed by the formula as follows: minC total = C h + C zl + C pg + C wd + C pv Where C h is the operating cost of the thermal power unit, C zl is the pollution control cost, C pg is the operating cost of the variable-speed pumped storage unit, C wd is the curtailment penalty cost for wind power, C pv is the curtailment penalty cost for solar power; Construct a nonlinear programming solution model, use the algorithm parameters, cost coefficients and constraint condition parameters as the model inputs, and use the preset initial point as the iteration starting point to calculate and output an approximate objective function value; Repeat the calculation step with the approximate objective function value as the iteration starting point until the maximum number of iterations is reached and the optimal objective function value is output; Take the optimal output of the thermal power unit, the optimal output of the variable-speed pumped-storage unit and the optimal grid-connected power of the wind-solar corresponding to the optimal objective function value as the regulation reference values to obtain the best operation method for jointly regulating and controlling variable-speed pumped storage and wind-solar.

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