Day-ahead and intra-day scheduling method for regional water-energy coupled system with seawater desalination plants

Abstract

The application discloses a seawater desalination plant containing regional water-energy coupling system day-ahead-intra-day two-stage scheduling method, relates to the technical field of power system scheduling, and comprises the following steps: based on the principle of satisfying seawater desalination process constraints, a seawater desalination load model is constructed; the principle of wind power consumption is analyzed for the seawater desalination load model, and a wind power consumption mechanism is constructed; the wind power consumption mechanism is used to reduce the peak shaving pressure of motor units and inhibit the fluctuation of net load; in the day-ahead scheduling stage, a pre-distribution scheme of thermal power units and storage batteries is obtained by solving a day-ahead scheduling model; in the intra-day scheduling stage, an intra-day scheduling model is constructed to dynamically optimize the seawater desalination load power, the output deviation of thermal power units, and the charging and discharging strategies of storage batteries and super capacitors. Through two-stage scheduling, the wind power uncertainty is coped with, the system flexibility is improved, the wind power abandonment rate and operation cost are reduced, and efficient collaborative utilization of energy and water resources is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of power system dispatching, and in particular to a two-stage dispatching method for a regional water-energy coupling system including a seawater desalination plant, including a day-ahead and intraday scheduling method. Background Art

[0002] With the significant expansion of wind power capacity, China's installed wind power capacity is projected to reach 521 GW by the end of 2024, an 18% annual increase. However, the randomness and volatility of wind power generation complicates grid connection, leading to significant curtailment. Traditionally, deep peaking of thermal power units (reducing the minimum stable combustion load to 30%-35%, with some advanced units reaching 20%-25%) is effective when the proportion of renewable energy is low. However, as the proportion of renewable energy increases, relying solely on deep peaking of thermal power to meet demand becomes difficult, leading to increased curtailment and reduced economic profitability of thermal power plants.

[0003] To address this issue, relevant research has been conducted from the perspective of demand-side response. Some studies have incorporated demand response mechanisms into system optimization by building integrated energy system planning models, achieving improved economic benefits and reduced environmental costs. Other studies have proposed a two-layer robust optimization method based on demand response and thermal comfort, reducing CO2 emissions while also lowering economic costs. Still other studies have constructed a two-layer optimization model for multi-microgrid integrated energy systems that incorporates energy storage and demand response, effectively improving system efficiency and reducing carbon emissions. Regarding load regulation, research has found that including high-energy-consuming loads such as fused magnesium and electrolytic aluminum in grid dispatch as interruptible loads can significantly reduce wind curtailment and system operating costs.

[0004] However, existing research still has shortcomings. Specifically, the proportion of adjustable loads in demand-side response is limited, and consumer electricity consumption behavior is influenced by multiple factors, making accurate prediction difficult and increasing the uncertainty of demand response strategies. Furthermore, the distribution of flexible resources varies across different regions, and there is a lack of research on coordinated scheduling specifically for coastal areas.

[0005] Currently, no effective solutions have been proposed for the problems in related technologies. Summary of the Invention

[0006] To address the challenges of the prior art, this paper proposes a two-stage scheduling method for a regional water-energy coupling system, including a desalination plant, both day-ahead and intraday. This method aims to overcome these technical issues. The goal is to provide a two-stage scheduling method for a regional water-energy coupling system, including a desalination plant, to effectively enhance the wind power absorption capacity of the power system and reduce system operating costs.

[0007] To this end, the specific technical solutions adopted in the present invention are as follows:

[0008] A two-stage scheduling method for a regional water-energy coupled system including a desalination plant: day-ahead and intraday scheduling.

[0009] In the established regional water-energy coupling framework system including desalination plants, a desalination load model is constructed based on the principle of satisfying desalination process constraints.

[0010] Based on the frequency component coordinated regulation mechanism of the net load and combined with the variational mode decomposition algorithm, the wind power absorption principle of the seawater desalination load model is analyzed and a wind power absorption mechanism is constructed;

[0011] The wind power absorption mechanism is utilized to reduce the peak load regulation pressure of the generator units and suppress net load fluctuations. During the day-ahead dispatch phase, a day-ahead dispatch model is constructed with the optimization objectives of minimizing the penalty costs for wind curtailment, the coal consumption costs and startup and shutdown costs of thermal power units, and the charging and discharging costs of batteries. By solving the day-ahead dispatch model, a pre-allocation plan for the operation of thermal power units and batteries is obtained.

[0012] During the intraday scheduling stage, the pre-allocation plan of the thermal power units and battery operations is used as the initial condition. Based on the constraints of supercapacitor operating costs and intraday plan adjustment costs, an intraday scheduling model is constructed to dynamically optimize the desalination load power, thermal power unit output deviation, and battery and supercapacitor charging and discharging strategies.

[0013] Furthermore, the regional water-energy coupling framework system including the desalination plant includes:

[0014] Construct a power supply system including wind power, thermal power units and batteries; construct a water supply system including seawater desalination load and supercapacitors;

[0015] By coupling the power supply system and the water supply system, a regional water-energy coupling framework system including a seawater desalination plant is obtained to achieve the coordinated optimization of energy and water resources, which is managed and regulated by the dispatching center.

[0016] Furthermore, based on the principle of satisfying the desalination process constraints, the desalination load model is constructed, including:

[0017] Based on the power, efficiency, water flow rate, upper and lower limits of water flow rate, head, and working status values ​​of the water intake pump during the seawater desalination process, and combined with the water density and gravity acceleration, the water intake pump constraint conditions are established; the correlation conditions for the power consumed by the high-pressure pump during the seawater desalination process are constructed;

[0018] Based on the principle that the working pressure of the reverse osmosis unit is higher than the transmembrane osmotic pressure, and combined with the life factor of the reverse osmosis unit, the reverse osmosis unit constraint conditions, reverse osmosis unit ramp constraint conditions and reverse osmosis unit start and stop constraint conditions are established;

[0019] Using the water levels, bottom areas, and total number of desalination units of the clean water and product water tanks, combined with the ratio of pretreated seawater to feed water flow, the product water tank effluent flow, the effluent flow of the reverse osmosis unit, the influent flow of the reverse osmosis unit, the intake flow of the intake pump, the upper and lower limits of the clean water tank water level, and the upper and lower limits of the product water tank water level, establish the constraints for the clean water and product tanks;

[0020] Using the water levels and upper and lower limits of the water level difference of the clear water tank and product water tank within the scheduling period, the scheduling continuity constraint conditions are established;

[0021] A seawater desalination load model is constructed, which includes water intake pump constraints, correlation conditions of high-pressure pump power consumption, reverse osmosis unit constraints, reverse osmosis unit ramp constraints, reverse osmosis unit start and stop constraints, clear water tank and product water tank constraints, and scheduling continuity constraints.

[0022] Furthermore, based on the principle that the working pressure of the reverse osmosis unit is higher than the transmembrane osmotic pressure, and combined with the life factor of the reverse osmosis unit, the reverse osmosis unit constraint conditions, reverse osmosis unit ramping constraints, and reverse osmosis unit start-stop constraints are established, including:

[0023] Based on the principle that the working pressure of the reverse osmosis unit is higher than the transmembrane osmotic pressure, and using the upper and lower limits of the transmembrane net pressure of the reverse osmosis unit, the operating status value of the reverse osmosis unit, the working pressure of the reverse osmosis unit and the transmembrane osmotic pressure difference, the reverse osmosis unit constraint conditions are established;

[0024] Establish the reverse osmosis unit climbing constraint conditions based on the reverse osmosis unit's climbing power upper and lower limits, the upper and lower limits of the working pressure increase and decrease per unit time period, the working pressure, and the high-pressure pump power;

[0025] According to the single start-up and shutdown cost of the seawater desalination unit, the maximum start-up and shutdown cost within the scheduling cycle, the total number of scheduling periods, and the operating status value of the reverse osmosis unit, the start-up and shutdown constraints of the reverse osmosis unit are established.

[0026] Furthermore, based on the frequency component coordinated regulation mechanism of the net load and combined with the variational mode decomposition algorithm, the wind power absorption principle of the seawater desalination load model is analyzed, and a wind power absorption mechanism is constructed, including:

[0027] According to the minimum output limit of the boiler and turbine of the thermal power unit and the load adjustment speed of the thermal power unit, the minimum technical output model of the thermal power unit is established;

[0028] According to the minimum technical output model of the thermal power unit, determine the limitations of the thermal power unit on technical output and ramp rate;

[0029] Based on the limitations of thermal power generation units on technical output and ramp rate, the regulation pressure of thermal power generation units is reduced by regulating the desalination load power. The net load is decomposed into components of different frequencies using the variational mode decomposition algorithm.

[0030] The supercapacitors in the desalination plant are used to smooth the first frequency component of the net load; the desalination load, batteries and thermal power units are used to smooth the second frequency component of the net load.

[0031] Furthermore, in the day-ahead dispatch phase, a day-ahead dispatch model is constructed with the optimization objectives of minimizing the wind power curtailment penalty cost, the coal consumption cost and startup and shutdown cost of thermal power units, and the battery charging and discharging cost. By solving the day-ahead dispatch model, the pre-allocation scheme for the thermal power units and battery operations is obtained, including:

[0032] Determine the time resolution for the day-ahead dispatch phase. Based on this time resolution, obtain day-ahead wind power forecast data and load forecast data. Build a day-ahead dispatch model based on the optimization objectives of minimizing wind curtailment penalty costs, coal consumption costs and startup and shutdown costs of thermal power units, and battery charging and discharging costs.

[0033] By solving the day-ahead dispatch model, the output curve and start-stop status of the thermal power units are determined, and the battery charge and discharge plan is formulated;

[0034] The output curve of the thermal power unit, the start-stop status, and the battery charge and discharge plan are used as a pre-allocation plan for the thermal power unit and the battery operation.

[0035] Furthermore, the constraints of the day-ahead scheduling model include:

[0036] Based on the principle that active power and load are equal in any period, the power balance constraint condition of the day-ahead stage is established, and the wind power grid power is constrained with the wind power forecast power as the upper limit;

[0037] Use the battery charging and discharging power from the grid, charging and discharging limits, and charging and discharging state parameters to construct battery charging and discharging constraint conditions;

[0038] The battery capacity constraint is constructed using the battery storage capacity, charge and discharge efficiency, maximum capacity, upper and lower storage limits, charge and discharge power from the power grid, and charge and discharge status parameters.

[0039] Furthermore, during the intraday scheduling phase, the pre-allocation scheme for the thermal power units and battery operations is used as the initial condition. Based on the constraints of supercapacitor operating costs and intraday plan adjustment costs, an intraday scheduling model is constructed to dynamically optimize the desalination load power, thermal power unit output deviation, and battery and supercapacitor charging and discharging strategies, including:

[0040] Determine the time resolution of the intraday scheduling stage, and obtain the scheduling plan within several time ranges based on the time resolution of the intraday scheduling stage;

[0041] The dispatch plan uses updated ultra-short-term forecasts of wind power and load, and after frequency decomposition using the variational mode decomposition algorithm, the first frequency component is adjusted by supercapacitors, while the second frequency component is coordinated by the desalination load and batteries.

[0042] Based on the day-ahead scheduling, the optimization objectives of the intraday scheduling phase, namely the operating cost of the newly added supercapacitors and the cost of adjusting the intraday plan, are determined. An intraday scheduling model is constructed to dynamically optimize the desalination load power, the output deviation of the thermal power units, and the charging and discharging strategies of batteries and supercapacitors.

[0043] Furthermore, the time resolution of the day-ahead scheduling stage is greater than that of the intraday scheduling stage, so as to achieve the goals of day-ahead peak shaving and valley filling and intraday smoothing of power fluctuations.

[0044] Furthermore, the constraints of the intraday scheduling model include:

[0045] Based on the principle that active power and load are equal in any period, the power balance constraint condition within the day is constructed;

[0046] Using the supercapacitor charging and discharging power, charging and discharging limit and charging and discharging state parameters from the grid, the supercapacitor charging and discharging constraint conditions are constructed;

[0047] The supercapacitor capacity constraint conditions are constructed using the supercapacitor's storage capacity, charging and discharging efficiency, maximum capacity, upper and lower storage limits, charging and discharging power from the power grid, and charging and discharging state parameters.

[0048] The beneficial effects of the present invention are:

[0049] The present invention provides a framework system for a regional hydro-energy coupling system including a seawater desalination plant. Secondly, the operating characteristics of the seawater desalination load are analyzed and a model is constructed. On this basis, the principle of wind power absorption by the seawater desalination load is analyzed. Then, considering the seawater desalination load characteristics, the charging and discharging characteristics of batteries and supercapacitors, a two-stage day-ahead and intraday optimization scheduling method for the regional hydro-energy coupling system is established with the goal of minimizing the costs of wind power abandonment, energy storage charging and discharging, and thermal power unit operation. Finally, the rationality and effectiveness of the proposed two-stage day-ahead and intraday scheduling method for the regional hydro-energy coupling system including a seawater desalination plant are verified through specific cases, and good results are achieved. The present invention fully utilizes the adjustability of the seawater desalination load and the buffering capacity of the water storage tank, addresses wind power uncertainty through two-stage scheduling, improves system flexibility, reduces wind abandonment rate and operating costs, and achieves efficient and coordinated utilization of energy and water resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0051] Figure 1 This is a structural diagram of a regional water energy coupling system including a seawater desalination plant according to the present invention;

[0052] Figure 2 This is a schematic diagram of the reverse osmosis seawater desalination technology of the present invention;

[0053] Figure 3 It is a schematic diagram of the reverse osmosis process of the present invention;

[0054] Figure 4 This is a schematic diagram of the analysis principle of wind power consumption based on seawater desalination load in the present invention;

[0055] Figure 5 This is a two-stage optimization scheduling flow chart of the present invention: day-ahead and intraday;

[0056] Figure 6 This is a day-ahead and day-intraday prediction curve diagram of conventional load, wind power output and residential water flow of the present invention;

[0057] Figure 7 This is a one-day-ahead scheduling result diagram for the scenario of the present invention;

[0058] Figure 8 This is the scheduling result diagram of the scenario of the present invention two days ago;

[0059] Figure 9 This is a comparison chart of the desalination load and energy storage operation conditions of scenarios one and two in the present invention;

[0060] Figure 10 This is the operating status diagram of the clear water tank of the present invention;

[0061] Figure 11 This is the operating status diagram of the product pool of the present invention;

[0062] Figure 12 This is a comparison chart of wind power output and abandoned wind volume before and after the seawater desalination load adjustment of the present invention;

[0063] Figure 13 This is a diagram of the scheduling results within one day of the scenario of the present invention;

[0064] Figure 14 This is a diagram of the scheduling results within two days of the scenario of the present invention;

[0065] Figure 15This is a diagram of the energy storage and seawater desalination operation status of the intraday scenario of the present invention;

[0066] Figure 16 This is a diagram of the energy storage and seawater desalination operation status of the second intraday scenario of the present invention;

[0067] Figure 17 This is a diagram of the operating status of the daily clear water tank of the present invention;

[0068] Figure 18 This is a diagram of the operating status of the product pool within a day of the present invention;

[0069] Figure 19 This is a comparison diagram of wind power output and abandoned wind volume before and after daily seawater desalination load regulation of the present invention;

[0070] Figure 20 This is a comparison chart of the daily supercapacitor output and its SOC of the present invention;

[0071] Figure 21 4 is a flow chart of a two-stage day-ahead and intraday scheduling method for a regional water-energy coupling system including a seawater desalination plant according to an embodiment of the present invention. DETAILED DESCRIPTION

[0072] To further illustrate each embodiment, the present invention provides drawings, which are part of the disclosure of the present invention. They are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. By referring to these contents, ordinary technicians in this field should be able to understand other possible implementation methods and advantages of the present invention. The components in the figures are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0073] According to an embodiment of the present invention, a two-stage day-ahead and intraday scheduling method for a regional water-energy coupling system including a seawater desalination plant is provided, which involves optimized modeling of seawater desalination load, construction of a framework for a regional water-energy coupling system including a seawater desalination plant, and a two-stage day-ahead and intraday scheduling model for the regional water-energy coupling system.

[0074] The present invention will now be further described with reference to the accompanying drawings and specific embodiments. Figure 21 As shown, the day-ahead and intraday two-stage scheduling method for a regional water-energy coupling system including a seawater desalination plant according to an embodiment of the present invention includes:

[0075] S1. Under the established regional water-energy coupling framework system containing seawater desalination plants, a seawater desalination load model is constructed based on the principle of satisfying seawater desalination process constraints.

[0076] S2. Based on the frequency component coordinated regulation mechanism of the net load and combined with the variational mode decomposition algorithm, the wind power absorption principle of the seawater desalination load model is analyzed and a wind power absorption mechanism is constructed.

[0077] S3. Utilize the wind power absorption mechanism to reduce the peak load regulation pressure of the generator units and suppress the net load fluctuation. In the day-ahead dispatch stage, with the optimization objectives of minimizing the penalty cost for wind power abandonment, the coal consumption cost and start-up and shutdown cost of the thermal power units, and the battery charging and discharging cost, a day-ahead dispatch model is constructed. By solving the day-ahead dispatch model, a pre-allocation plan for the operation of the thermal power units and the battery is obtained.

[0078] S4. During the intraday scheduling phase, the pre-allocation scheme of the thermal power units and the battery operation is used as the initial condition. Based on the constraints of the supercapacitor operating cost and the intraday plan adjustment cost, an intraday scheduling model is constructed to dynamically optimize the desalination load power, the output deviation of the thermal power units, and the charging and discharging strategies of the batteries and supercapacitors.

[0079] In one embodiment, a regional water energy coupling framework system including a seawater desalination plant includes:

[0080] Construct a power supply system including wind power, thermal power units and batteries; construct a water supply system including seawater desalination loads and supercapacitors; couple the power supply system and the water supply system to obtain a regional hydropower coupling framework system including a seawater desalination plant, which is used to achieve the coordinated optimization of energy and water resources, and is managed and regulated by the dispatching center.

[0081] In one embodiment, based on the principle of satisfying seawater desalination process constraints, constructing a seawater desalination load model includes:

[0082] Based on the power, efficiency, water flow rate, upper and lower limits of water flow rate, head and working status values ​​of the water intake pump in the seawater desalination process, and combined with the density of water and gravity acceleration, the water intake pump constraint conditions are established; the correlation conditions of the power consumed by the high-pressure pump in the seawater desalination process are constructed; based on the principle that the working pressure of the reverse osmosis unit is higher than the transmembrane osmotic pressure, and combined with the life factor of the reverse osmosis unit, the reverse osmosis unit constraint conditions, reverse osmosis unit climbing constraints and reverse osmosis unit start and stop constraints are established; using the water level, bottom area, and total number of seawater desalination units of the clear water tank and product water tank, and combined with the ratio of pretreated seawater to feed water flow, product The constraints of the clean water tank and the product tank are established by taking into account the outflow rate of the product tank, the outflow rate of the reverse osmosis unit, the inflow rate of the reverse osmosis unit, the inflow rate of the water intake pump, the upper and lower limits of the water level of the clean water tank, and the upper and lower limits of the water level of the product tank. The scheduling continuity constraints are established by using the water levels and the upper and lower limits of the water level difference of the clean water tank and the product tank within the scheduling period. A desalination load model is constructed, which includes the constraints of the water intake pump, the correlation conditions of the power consumed by the high-pressure pump, the constraints of the reverse osmosis unit, the ramp constraints of the reverse osmosis unit, the start and stop constraints of the reverse osmosis unit, the constraints of the clean water tank and the product tank, and the scheduling continuity constraints.

[0083] In one embodiment, based on the principle that the working pressure of the reverse osmosis unit is higher than the transmembrane osmotic pressure, and in combination with the lifespan of the reverse osmosis unit, the reverse osmosis unit constraint conditions, reverse osmosis unit ramping constraint conditions, and reverse osmosis unit start-stop constraint conditions are established, including:

[0084] Based on the principle that the working pressure of the reverse osmosis unit is higher than the transmembrane osmotic pressure, and using the upper and lower limits of the reverse osmosis unit's net transmembrane pressure, the operating status value characterizing the reverse osmosis unit, the working pressure of the reverse osmosis unit and the transmembrane osmotic pressure difference, the reverse osmosis unit constraint conditions are established; according to the upper and lower limits of the reverse osmosis unit's ramping power, the upper and lower limits of the working pressure increase and decrease per unit time period, the working pressure and the high-pressure pump power, the reverse osmosis unit ramping constraint conditions are established; according to the single start-up and shutdown cost of the seawater desalination unit, the maximum start-up and shutdown cost within the scheduling cycle, the total number of scheduling periods, and combined with the operating status value of the reverse osmosis unit, the reverse osmosis unit start-up and shutdown constraint conditions are established.

[0085] In one embodiment, based on the frequency component coordinated regulation mechanism of the net load and combined with the variational mode decomposition algorithm, the wind power absorption principle of the seawater desalination load model is analyzed, and the wind power absorption mechanism is constructed, including:

[0086] Based on the minimum output limits of the boilers and turbines of the thermal power units, as well as the load regulation speed of the thermal power units, a minimum technical output model of the thermal power units is established; based on the minimum technical output model of the thermal power units, the limitations of the thermal power units in terms of technical output and ramp rate are determined; based on the limitations of the thermal power units in terms of technical output and ramp rate, the regulation pressure of the thermal power units is reduced by regulating the seawater desalination load power; the variational mode decomposition algorithm is used to decompose the net load into components of different frequencies; the supercapacitors in the seawater desalination plant are used to smooth the first frequency component of the net load; and the seawater desalination load, batteries and thermal power units are used to smooth the second frequency component of the net load.

[0087] In one embodiment, during the day-ahead scheduling phase, a day-ahead scheduling model is constructed with the optimization objectives of minimizing the wind curtailment penalty cost, the coal consumption cost and startup and shutdown cost of thermal power units, and the battery charging and discharging cost. By solving the day-ahead scheduling model, a pre-allocation plan for the thermal power units and battery operations is obtained, including:

[0088] Determine the time resolution of the day-ahead dispatch stage, and based on the time resolution of the day-ahead dispatch stage, obtain the day-ahead wind power forecast data and load forecast data, and construct a day-ahead dispatch model based on the optimization objectives of minimizing the wind curtailment penalty cost, the coal consumption cost and start-up and shutdown cost of the thermal power unit, and the battery charging and discharging cost; by solving the day-ahead dispatch model, determine the output curve and start-up and shutdown status of the thermal power unit, and formulate a battery charging and discharging plan; use the output curve and start-up and shutdown status of the thermal power unit and the battery charging and discharging plan as a pre-allocation plan for the work of the thermal power unit and the battery.

[0089] In one embodiment, the constraints of the day-ahead scheduling model include:

[0090] Based on the principle that active power and load are equal in any period of time, the power balance constraint condition of the day-ahead stage is constructed, and the wind power grid-connected power is constrained with the predicted wind power of the day-ahead as the upper limit; the battery charge and discharge power from the grid, charge and discharge limit and charge and discharge status parameters are used to construct the battery charge and discharge constraint condition; the battery storage capacity, charge and discharge efficiency, maximum capacity, upper and lower storage capacity limits, charge and discharge power from the grid and charge and discharge status parameters are used to construct the battery capacity constraint.

[0091] In one embodiment, during the intraday scheduling phase, the pre-allocation plan for the thermal power units and the battery operation is used as the initial condition. Based on the constraints of the supercapacitor operation cost and the intraday plan adjustment cost, an intraday scheduling model is constructed to dynamically optimize the desalination load power, the output deviation of the thermal power units, and the charging and discharging strategies of the batteries and supercapacitors. The model includes:

[0092] Determine the time resolution of the intraday scheduling stage, and obtain scheduling plans within several time ranges based on the time resolution of the intraday scheduling stage; in the scheduling plan, based on the updated ultra-short-term forecast of wind power and load, and after frequency decomposition based on the variational mode decomposition algorithm, adjust the first frequency component through supercapacitors, and coordinately adjust the second frequency component through the desalination load and batteries; based on the day-ahead scheduling, determine the optimization objectives of the intraday scheduling stage for the operating cost of the newly added supercapacitor and the cost of adjusting the intraday plan, and construct an intraday scheduling model to dynamically optimize the desalination load power, thermal power unit output deviation, and the charging and discharging strategies of batteries and supercapacitors.

[0093] In one embodiment, the time resolution of the day-ahead scheduling phase is greater than the time resolution of the intraday scheduling phase, so as to achieve the goals of day-ahead peak shaving and valley filling and intraday smoothing of power fluctuations.

[0094] In one embodiment, the constraints of the intraday scheduling model include:

[0095] Based on the principle that active power and load are equal in any period of time, the power balance constraint conditions of the intraday stage are constructed; the supercapacitor charging and discharging power, charging and discharging limits and charging and discharging state parameters of the supercapacitor from the power grid are used to construct the supercapacitor charging and discharging constraint conditions; the supercapacitor capacity constraint conditions are constructed using the supercapacitor's storage capacity, charging and discharging efficiency, maximum capacity, upper and lower storage capacity limits, charging and discharging power from the power grid and charging and discharging state parameters.

[0096] In order to facilitate understanding of the above technical solutions of the present invention, the working principle of the present invention in actual process is described in detail below.

[0097] First, a framework system of a regional water-energy coupling system containing a seawater desalination plant is given; secondly, the operating characteristics of the seawater desalination load are analyzed and a model is constructed, and on this basis, the principle of wind power absorption by the seawater desalination load is analyzed; then, considering the seawater desalination load characteristics, battery and supercapacitor charging and discharging characteristics, a two-stage day-ahead and intraday optimization scheduling method for the regional water-energy coupling system is established with the goal of minimizing the costs of wind curtailment, energy storage charging and discharging, and thermal power unit operation; finally, the rationality and effectiveness of the proposed two-stage day-ahead and intraday scheduling method for the regional water-energy coupling system containing a seawater desalination plant are verified through a specific case, and good results are achieved.

[0098] During the day-ahead scheduling phase, with the goal of minimizing total system cost, an optimization model was constructed that considered the desalination load adjustability and the buffering capacity of the water storage tanks. A preliminary scheduling plan for thermal power unit output, battery charging and discharging, and desalination was developed. During the intraday scheduling phase, variational mode decomposition was used to divide the net load into high-frequency and low-frequency components. Supercapacitors were used to rapidly respond to high-frequency fluctuations. The desalination load was combined with the water storage tanks and batteries, and the thermal power units to respond to the low-frequency components, forming a "high-frequency rapid response and low-frequency coordinated peak-shaving" regulation system. The effectiveness and rationality of the proposed model were then verified in a specific scenario example.

[0099] Follow these steps to implement:

[0100] Step 1: Establish a framework for the regional water-energy coupling system, including a desalination plant, by analyzing its composition and operational characteristics. Within this framework, new coupling elements are incorporated into the basic water-energy coupling system model of the present invention. These elements are embodied in the desalination plant's dual attributes of "controllable electrical load" and "controllable water source," as well as the rapid response mechanism of supercapacitors. These elements enable exploration of the flexibility boundaries of cross-domain coordinated scheduling of water-energy resources in complex scenarios with a high proportion of wind power grid integration.

[0101] Step 2. Considering the power adjustability of the desalination load and the buffering capacity of the water storage tank, a desalination load model is established and its wind power absorption principle is analyzed. The model construction is centered on the reverse osmosis (RO) process, taking into account the power constraints of the water intake pump and high-pressure pump and the dynamic balance of the water level in the water storage tank; the wind power absorption principle analysis is centered on "high-frequency-low-frequency component coordinated regulation". Through variational mode decomposition (VMD), the net load is divided into high-frequency fluctuations (response by supercapacitors) and low-frequency fluctuations (response by the desalination load combined with batteries and thermal power units), and a wind power absorption mechanism of "power adjustment-water storage buffering-multi-energy coordination" is constructed.

[0102] Step 3: Establish an optimized scheduling method for a regional hydro-energy coupling system and verify the rationality and effectiveness of the proposed scheduling model through specific cases. With the goals of day-ahead peak shaving and valley filling and intraday power smoothing, a two-stage scheduling strategy for a regional hydro-energy coupling system including a desalination plant is proposed: day-ahead and intraday.

[0103] Step 4: Verify the rationality and effectiveness of the proposed regional water-energy coupling system optimization scheduling method through specific cases.

[0104] Specifically:

[0105] The regional water-energy coupling system including the desalination plant in step 1 is a comprehensive integrated system, such as Figure 1 As shown in the figure, the distribution network and the water distribution network are coupled together through water distribution pumps to achieve coordinated optimization of energy and water resources, and are uniformly managed and regulated by the dispatching center.

[0106] The regional hydropower coupling system consists of a power supply system and a water supply system. The power supply system includes wind power, thermal power units and batteries. The water supply system uses a desalination plant to produce fresh water for urban water loads. Figure 1 It can be seen that the desalination plant of the present invention is composed of a desalination load (a water intake pump, a desalination device, a clear water tank and a product water tank) and a supercapacitor. The water intake pump is responsible for extracting seawater, and its operating power and water intake flow rate directly affect the production efficiency and energy consumption of the desalination plant. The desalination device is the core part, which uses desalination technology to remove salt from seawater and convert it into usable fresh water. The clear water tank and the product water tank are used to store seawater and fresh water respectively, which can make the water intake pump and the desalination device run in staggered order to increase the operational flexibility of the power grid. The supercapacitor can reduce the impact on the power grid during desalination load regulation. It can quickly respond to changes in load and quickly provide or absorb electrical energy when the desalination equipment starts, stops or the load suddenly changes, maintain the stability of the power grid voltage, and ensure the reliable operation of the power system.

[0107] It can be seen that the regional hydropower coupling system not only couples energy and resources together, but also optimizes scheduling according to the needs of various types of loads at different times. It achieves peak shaving and valley filling through the regulation characteristics of seawater desalination loads and the energy time-shifting characteristics of batteries, thereby improving the regulation flexibility of the system and meeting the needs of various loads.

[0108] In step 2, a seawater desalination load model is established and its wind power absorption principle is analyzed. The specific steps and modeling process are as follows:

[0109] First, let's analyze the load-operating characteristics of seawater desalination. Seawater desalination technology, also known as seawater desalination, focuses on separating the salt from the water in seawater. Thermal (distillation) and membrane methods are commonly used desalination methods. Thermal methods include multi-effect distillation, multi-stage flash evaporation, mechanical vapor compression evaporation, and multi-effect jet evaporation; membrane methods primarily involve reverse osmosis (RO) and electrodialysis. With the continuous development of energy recovery devices, RO technology has become the most energy-efficient desalination technology. Coupled with its low construction cost and small footprint, RO technology has become the most popular desalination technology.

[0110] The principle of RO desalination technology is as follows Figure 2 As shown, due to the difference in liquid concentration on both sides of the osmotic membrane, an osmotic pressure difference is generated. In the absence of external interference, freshwater will spontaneously flow through the osmotic membrane to the more concentrated seawater side until osmotic equilibrium is achieved, at which point a certain height difference will appear between the two liquid levels. When pressure is applied to the seawater side and this pressure exceeds the osmotic pressure, water molecules are forced through the osmotic membrane under pressure to reach the less concentrated freshwater side, thus separating freshwater from seawater. This process is known as the RO process.

[0111] RO desalination plant process flow Figure 3 As shown, the feed seawater is first pumped into the pretreatment unit by a water intake pump. After flocculation, sedimentation, and filtration, it enters the clear water tank. The treated seawater is then pressurized by the high-pressure pump of the reverse osmosis desalination unit, forcing water molecules through a semipermeable membrane into the freshwater side, thereby achieving salt-water separation. The separated freshwater undergoes post-treatment steps such as water quality adjustment to form product water. The remaining salt water still has a high pressure, and this energy is reused in the pressurization of the feed seawater through an energy recovery device, thereby improving system efficiency and reducing energy consumption. The intake pump and high-pressure pump consume a lot of power during the desalination process, making the seawater desalination load a high-energy load. Furthermore, it can be combined with a water storage tank during operation, allowing a certain degree of operational flexibility. Desalination plants can adjust their operating plans. During periods of low electricity demand, they can increase water intake and desalination, storing excess seawater and freshwater in clean water and product tanks. During peak electricity demand, they can reduce water intake and desalination, releasing water from the tanks to meet demand, while also reducing power demand on the grid, achieving a "peak shaving and valley filling" strategy. In summary, desalination loads offer the advantages of power adjustability and flexibility.

[0112] Secondly, the desalination load model is constructed. Assuming that the lift of the water intake pump is fixed, the constraints on its operation are:

[0113] (1);

[0114] Where:P t In 、 q t In and H t In Respectively t Water intake pump power, water flow and head in each period; is the water intake pump efficiency; t Indicates time; ρ and g are the density of water and the acceleration due to gravity, respectively. is a 0-1 variable representing the working status of the water intake pump (1 means running); and Respectively upper and lower limits.

[0115] The power consumed by the high-pressure pump during operation is related to the working pressure, the concentration of the feed seawater, the recovery rate of reverse osmosis, and various parameters of the osmotic membrane, namely:

[0116] (2);

[0117] Where: 、 、 and are the working pressure, inlet flow rate, outlet flow rate and high-pressure pump power of RO unit (reverse osmosis unit) d; and RO units d Permeability coefficient and membrane area of ​​the permeable membrane; is the transmembrane osmotic pressure difference; and is the high-pressure pump power coefficient; is the feed seawater concentration; R is the reverse osmosis recovery rate.

[0118] To ensure that water molecules can pass through the semipermeable membrane smoothly, the operating pressure of the RO unit must be higher than the transmembrane osmotic pressure. However, too high an operating pressure will have an adverse effect on the service life of the semipermeable membrane, so there are the following constraints:

[0119] (3);

[0120] Where: and are the upper and lower limits of the net transmembrane pressure of RO unit d, respectively; It is a 0-1 variable representing the operating status of the RO unit d (1 means running).

[0121] Sudden changes in the operating pressure or power of the RO desalination unit will shorten the service life of the osmotic membrane. Based on this, the following ramp constraints are considered:

[0122] (4);

[0123] Where: and They are the upper and lower limits of the creeping power of RO unit d respectively; and It is the upper and lower limits of the RO unit's working pressure per unit time period.

[0124] Considering that frequent start-up and stop of the RO unit will not only damage the service life of the osmotic membrane, but also lead to increased power loss, the present invention adopts the following constraints:

[0125] (5);

[0126] In the formula: C, are the single start-up and shutdown cost of desalination unit d and the maximum start-up and shutdown cost within the scheduling cycle; N is the total number of scheduling periods.

[0127] The clean water tank is used to store pre-treated seawater, while the product water tank is used to store post-treated desalinated water. The constraints of the two are similar in operation:

[0128] (6);

[0129] Where: and They are the water levels of the clean water tank and the product water tank respectively; is the ratio of the flow rate of pretreated seawater to feed water; The outflow rate of the product pool; and are the bottom areas of the clean water tank and product water tank respectively; and Respectively Upper and lower limits; and Respectively The upper and lower limits of ; D is the total number of seawater desalination units. and Express the same meaning. and Express the same meaning.

[0130] To ensure the continuity of scheduling, the remaining water volume in the clean water tank and product water tank after each scheduling cycle should be consistent with the initial water volume, that is:

[0131] (7);

[0132] Where: and To adjust the water level of the initial clear water tank and product water tank; and To adjust the water level of the final clear water tank and product water tank; δ The upper limit of the difference between the clear water tank water levels at the beginning and end of the scheduling period, It is the upper limit of the water level difference between the product pool water level at the beginning and end of the scheduling cycle.

[0133] Finally, the principle of wind power absorption in seawater desalination is analyzed. When renewable energy is connected to the grid in large quantities, thermal power units often need to operate at a lower output level to improve their grid connection efficiency. However, the boilers and turbines of thermal power units have minimum output limits. The output of the steam unit is determined by the amount of steam passing through the impeller. Due to the influence of the steam intake of the steam unit, the load adjustment speed of the thermal power unit is slow. The load adjustment rate of pure condensing thermal power units is only 2%-3% / min, which shows that their adjustment capacity is quite limited. Under normal circumstances, the minimum technical output of a conventional thermal power unit is about 50% of the rated power. Its mathematical model can be briefly expressed as:

[0134] (8);

[0135] Where: For thermal power units j exist t Output during the time period; For thermal power units j exist t -1 period output; and Thermal power units j Uphill climbing output limit and downhill climbing output limit; and Thermal power units j The upper and lower limits of output power; To characterize thermal power units j A 0-1 variable indicating the running status (1 means running).

[0136] In renewable energy power systems, thermal power units are limited by technical output and ramp rate, making it difficult to cope with the sharp fluctuations in wind power output, leading to wind curtailment. To solve this problem, desalination plants can participate in system regulation as flexible resources. By rationally regulating the desalination load power, the regulation pressure of thermal power units can be effectively alleviated. The desalination plant is equipped with supercapacitors with small capacity and fast regulation speed. In order to further improve its capacity utilization, the variational mode decomposition (VMD) method is used to decompose the net load of the system into components of different frequencies. Among them, the high-frequency component has the characteristics of rapid changes and frequent fluctuations, and is quickly adjusted by the supercapacitor. In addition, the charging and discharging functions of the battery can work in conjunction with the desalination plant. When the desalination plant approaches the regulation limit, the battery can supplement the regulation capacity in time to ensure that the system is always in a safe and stable operating state. This collaborative regulation mechanism not only significantly improves the wind power absorption capacity, but also further improves the utilization rate of wind power. The schematic diagram of the analysis principle of wind power absorption based on desalination load is shown as follows. Figure 4 shown.

[0137] Under the traditional dispatching mode, the net load of the power system is:

[0138] (9);

[0139] Where: is the net load; is the net load without considering seawater desalination regulation; When wind power output fluctuates and conventional peak-shaving resources cannot smooth it out, the amount of wind power blocked in the system is:

[0140] (10);

[0141] Where: The amount of blocked wind power; is the minimum output of thermal power units; 0-T3 is the period when wind power is abandoned in the system.

[0142] Based on VMD decomposition, the high-frequency component of the net load has been smoothed by the supercapacitor. If the seawater desalination load is considered to participate in the system peak regulation, the seawater desalination load power during the wind curtailment period is P m , the net load of the power system at this time for:

[0143] (11);

[0144] After the seawater desalination load participates in peak regulation, the wind power blocked in the system is , as shown in formula (12). Comparing formula (11) and formula (12), it can be seen that the seawater desalination load participates in peak regulation, and the blocked wind power is reduced.

[0145] (12);

[0146] This shows that after the supercapacitor smoothes the high-frequency components of the net load, the net load fluctuation is effectively reduced, thereby reducing the regulation of energy storage and desalination. At the same time, based on the participation of the desalination load in peak regulation, the battery absorbs wind power during the wind curtailment period and releases power during the subsequent load peak period, further optimizing system operation. This peak regulation mode composed of a desalination plant and batteries has achieved remarkable results: on the one hand, the supercapacitor reduces the net load fluctuation at the source and reduces system instability; on the other hand, the coordinated peak regulation of the desalination load and the battery significantly reduces the peak-to-valley difference of the system net load, greatly alleviating the peak regulation pressure of the thermal power units, and providing a solid guarantee for the stable and efficient operation of the power system.

[0147] In step 3, an optimization scheduling method for the regional water-energy coupling system was established. As the installed capacity of new energy sources such as wind power increases year by year, its absorption problem becomes increasingly prominent. Although wind power forecasting provides important support for system scheduling, there are inevitably deviations in the forecast results. Simply relying on day-ahead optimization scheduling is difficult to cope with the uncertainty on both the source and load sides. In addition, the prediction accuracy of wind power increases with the decrease of the time scale. With the goal of day-ahead peak shaving and valley filling and intraday smoothing of power fluctuations, a two-stage day-ahead and intraday scheduling strategy for the regional water-energy coupling system containing seawater desalination plants is proposed. The two-stage day-ahead and intraday scheduling process is as follows: Figure 5 shown.

[0148] (1) Day-ahead dispatching stage: The time resolution is 1 hour, and the schedule is prepared every 24 hours. The dispatch center first accesses the day-ahead wind power forecast data and load forecast data, and constructs a day-ahead dispatching model with the optimization objectives of minimizing the wind curtailment penalty cost, the coal consumption cost and start-up and shutdown cost of the thermal power unit, and the battery charging and discharging cost. By solving this model, the output curve and start-up and shutdown status of the thermal power unit are determined, and the battery charging and discharging plan is formulated. These pre-allocation plans will serve as the initial conditions for intraday dispatching, providing a benchmark operating framework for short-term fine dispatching, completing the global coordination of thermal power units and battery resources in advance, and balancing the daytime energy supply and demand.

[0149] (2) Intraday scheduling phase: The time resolution is 15 minutes, and the schedule is made every 15 minutes, and the schedule for the next 4 hours is obtained each time. Each scheduling is based on the updated ultra-short-term forecast of wind power and load, and based on the VMD decomposition of uncertain variables, the high-frequency components are assigned to the supercapacitor with fast adjustment speed for processing, while the low-frequency components are coordinated by the desalination load and the battery. The optimization goal is to dynamically optimize the desalination load power, the output deviation of the thermal power unit, and the charging and discharging strategy of the battery and supercapacitor based on the day-ahead scheduling. This process not only utilizes the power adjustability of the desalination plant and the buffering capacity of the water tank to smooth out load fluctuations, but also reduces the net load change rate through the high-frequency response characteristics of the supercapacitor, ultimately achieving the coordinated scheduling effect of "coarse adjustment to determine the framework on the day-ahead and fine adjustment to smooth out fluctuations within the day", significantly improving the system's adaptability to wind power fluctuations and overall economic efficiency.

[0150] 1. Day-ahead scheduling model:

[0151] Objective function:

[0152] (13);

[0153] (14);

[0154] (15);

[0155] (16);

[0156] (17);

[0157] (18);

[0158] Where: F 1 is the total cost of the system's day-ahead operation, including the operating cost of thermal power units F G , wind curtailment penalty costs F W , start-stop costs 2. Seawater desalination load start-up and shutdown costs , battery operating costs F B ; N G is the number of thermal power units; a j 、 b j 、 c j Thermal power units j Coal consumption cost coefficient, pstart 、 p stop are the costs incurred during a single start-up and shutdown of a thermal power unit, is the total number of desalination units, Desalination unit d Start-up and shutdown costs, is the unit wind curtailment cost, P W-fore、t and P W、t They are the day-ahead wind power forecast and wind power on-grid power at time t respectively. and The charging power and discharging power of the battery at time t are respectively p is the unit charge and discharge cost of the battery; T The scheduling period.

[0159] Constraints:

[0160] 1. Power balance constraint: At any time, the system active power should be equal to the load.

[0161] (19);

[0162] Where: P L、t is the day-ahead load power forecast at time t; P W、t is the wind power grid-connected power at time t; is the RO unit at time t d High-pressure pump power; Take the water pump power at time t.

[0163] 2. Wind power output constraints.

[0164] (20);

[0165] 3. Battery restrictions. Charge and discharge restrictions:

[0166] (twenty one);

[0167] Where: and are the charging and discharging power of the battery from the grid at time t, and They are the battery charge and discharge limits respectively. 、 are binary variables, representing the battery charging and discharging state parameters in time period t. =1, =0 means it is in charging state, =0, =1 means in the energy release state;

[0168] Capacity constraints:

[0169] (twenty two);

[0170] Where: For batteries t The amount of power stored at any time, 、 Especially the charging and discharging efficiency of the battery, is the maximum capacity of the battery, 、 The upper and lower limits of the battery storage capacity are shown in Figure 1-1.

[0171] The compact form of the day-ahead scheduling model can be expressed as:

[0172] (twenty three);

[0173] 2. Intraday Scheduling Model:

[0174] Objective function:

[0175] (twenty four);

[0176] (25);

[0177] Where: F 2 is the total cost of the system's day-ahead operation, including the operating cost of thermal power units F G , wind curtailment penalty costs F W、 Start-stop costs , seawater desalination load start-up and shutdown costs , battery operating costs F B、 Supercapacitor operating costs F SC ; and are respectively the supercapacitor charging power and discharging power at time t, is the unit charge and discharge cost of the supercapacitor.

[0178] Constraints:

[0179] 1) Power balance constraint: At any time, the system active power should be equal to the load.

[0180] (26);

[0181] Where: and are the supercapacitor charging power and discharging power at time t respectively.

[0182] 2) Super capacitor operation constraints. Charge-discharge constraints:

[0183] (27);

[0184] where, and are the super capacitor charge-discharge power from the grid at time t, and are the super capacitor charge-discharge limits. , are binary variables, respectively the super capacitor charge and discharge state parameters at time t, = 1, = 0 indicates the charging state, = 0, = 1 indicates the discharging state.

[0185] Capacity constraints:

[0186] (28);

[0187] where, is the super capacitor storage capacity at time t, , are the super capacitor charge-discharge efficiencies, is the maximum capacity of the super capacitor, , are the super capacitor storage capacity upper and lower limits.

[0188] The compact form of the intra-day dispatch model can be expressed as:

[0189] (29).

[0190] The proposed method for scheduling a regional water-energy coupling system, including a desalination plant, on a day-ahead and intraday basis, establishes a "controllable electrical load-water tank buffer-multi-energy synergy" regulation system to coordinate the desalination load with energy storage equipment and thermal power units on multiple time scales. This significantly improves wind power absorption capacity, reduces system operating costs, and enhances system flexibility. Specifically, this method leverages the power adjustability of the desalination load and the storage capacity of the water tank to increase operating power storage during periods of surplus wind power and reduce power discharge during peak load periods. This method, combined with the differentiated regulation of the high-frequency and low-frequency components of the net load by supercapacitors and batteries, forms a "high-frequency rapid response-low-frequency coordinated peak-shaving" mechanism. The calculation results show that this method can reduce the day-ahead wind curtailment rate from 6.86% to 4.25%, and the total system operating cost from 359,800 yuan to 329,200 yuan, and can also reduce the intraday wind curtailment rate from 6.74% to 4.81%, and the total system operating cost from 372,400 yuan to 342,300 yuan. It effectively solves the problem of wind power consumption and coordinated utilization of water-energy resources in coastal areas, and provides an important reference for the optimal scheduling of regional energy systems.

[0191] To verify the validity and rationality of the model, a simulation analysis is conducted here. The specific conditions and parameters are as follows: 4 thermal power units with a total capacity of 1200MW. The maximum output Pmax and minimum output Pmin of each unit and the operating cost parameters (a, b, c) are shown in Table 1. The total installed capacity of the wind farm is 300MW, the unit wind curtailment penalty cost is 200 yuan / (MW·h), and the conventional load, wind power output and residential water flow forecast values ​​are as follows: Figure 1 As shown in the figure, the power consumption of the water distribution pump calculated based on the residential water flow has been added to the conventional load; the operating parameters of the seawater desalination equipment are shown in Table 2, and the maximum total water production per hour is 6620m 3 The cost of a single start-stop is 50 yuan, and it can run uninterruptedly for 24 hours; the operating parameters of the energy storage equipment are shown in Table 3. The operating cost of the battery is 50 yuan / (MW·h), and the operating cost of the supercapacitor is 40 yuan / (MW·h).

[0192] Figure 6Figure 3 is the day-ahead and intraday forecast curve for conventional load, wind power output, and residential water flow. As can be seen from the figure, the day-ahead forecast value of conventional load is between 496 and 771 MW, and the intraday forecast value is between 476.6 and 805.3 MW, with peaks occurring between 8:00 and 12:00 and 18:00 and 21:00. The day-ahead forecast value of wind power output is between 158 and 300.75 MW, and the intraday forecast value is between 123 and 313 MW, with the highest output between 1:00 and 4:00, 13:00 and 17:00, and 22:00 and 24:00. The day-ahead forecast value of residential water flow is between 2600 and 5700 m3 / h, and the intraday forecast value is between 2650 and 5800 m3 / h, with greater residential water demand between 7:00 and 9:00 and 18:00 and 21:00. It can be seen from the calculation scenario that wind power exhibits an anti-peaking characteristic, which increases the peaking pressure of thermal power units and reduces the utilization rate of wind energy.

[0193] In addition, in order to verify the rationality and effectiveness of the method proposed in this study, the following two scenarios were set up for comparative analysis.

[0194] Scenario 1: This scenario adopts a two-stage optimization scheduling model, namely day-ahead and intraday, in which the desalination load adjustment power limit is set to 0, relying solely on product water pool regulation to meet residents' water needs, thereby maintaining constant power operation.

[0195] Scenario 2: This scenario uses a two-stage optimization scheduling model: day-ahead and intraday. The desalination load can be adjusted up and down, and the product pool can be adjusted to meet residents' water needs, thereby increasing the adjustment range.

[0196] This comparative analysis aims to reveal the potential benefits of regulating desalination load in improving wind power utilization and reducing peak load pressure on thermal power units, thereby reducing the total system operating cost.

[0197] 1. Verification of the day-ahead optimization scheduling model.

[0198] Figure 7 and Figure 8 The scheduling results of scenario 1 and scenario 2 are shown. Figure 7 and Figure 8As can be seen, in Scenario 1 and Scenario 2, to further reduce the operating costs of the thermal power units, thermal power unit 3 assumes the majority of the regulation tasks, while thermal power units 1, 2, and 4 operate at minimum output almost throughout the entire scheduling cycle. This is due to the operating cost per unit of generated power of the thermal power units. The specific parameters are shown in Table 1. In addition, all thermal power units operate at minimum output from 1:00-6:00, 12:00-17:00, and 23:00-24:00. This is due to wind curtailment during these periods, and to reduce curtailment, all thermal power units are operated at their lowest output. Furthermore, compared to the case where the desalination load is not involved in regulation, the participation of the desalination load in regulation, combined with energy storage charging and discharging, makes the system load more stable, thereby reducing the regulation tasks of the thermal power units and reducing wind curtailment during periods of curtailment.

[0199] To further compare and analyze the desalination load and energy storage operation conditions in scenarios 1 and 2, Figure 9 As shown, in scenario one, the desalination load does not participate in regulation, and is only regulated up and down by the energy storage charging and discharging. Since the energy storage is continuously charged or discharged in a short period of time, it reaches the upper or lower capacity limit, which causes the energy storage battery to be unable to operate. In scenario two, the energy storage is still continuously charged or discharged in a short period of time, causing it to reach the upper or lower capacity limit, which causes the energy storage battery to be unable to operate. However, since the desalination load participates in regulation in scenario two, the desalination system can still be regulated up and down when the energy storage is unable to operate, making up for the insufficient regulation capability of the energy storage. In addition, when the wind power output is large and the system conventional load is at a low point, the energy storage is charged. When the wind power output is small and the system conventional load is at a peak point, the energy storage supplies power to the desalination load, reducing the regulation pressure of the thermal power units.

[0200] Figure 10 and Figure 11This figure shows the operating status of the clear water tank and product water tank in the seawater desalination plant in scenario 2. In scenario 2, when wind power output is large and the system conventional load is at a low point (3:00-5:00, 13:00-17:00, and 22:00-24:00), to avoid insufficient downtime or even shutdown of thermal power units, the water intake pump and high-pressure pump are adjusted upward, and the clear water tank and product water tank are stored in advance. Due to the capacity limit of the clear water tank, they are forced to adjust downward at 4:00 and 15:00. To ensure the continuity of the scheduling cycle, the water intake pump is also adjusted downward at 24:00 to maintain the same water level in the clear water tank at the beginning and end. When wind power output is low and the system's conventional load is at its peak (7:00-12:00 and 18:00-22:00), to reduce the upward regulation pressure on the thermal power units, both the intake pump and the high-pressure pump are regulated downward. Simultaneously, the clear water tank and storage tank begin to release water to meet desalination needs and residential water demand. At 12:00 and 22:00, the product water tank is nearly depleted, and the high-pressure pump tends to increase regulation to meet residential water needs. Compared to scenario one, the desalination load can effectively utilize the clear water tank and product water tank as a buffer, allowing for flexible regulation, which reduces the regulation pressure on the thermal power units.

[0201] Comparison of wind power output and wind curtailment before and after seawater desalination load adjustment in scenario 1 and scenario 2, as shown in the figure below: Figure 12 As shown. Figure 12 As can be seen from the data, in scenario one, the day is divided into 24 periods, with 13 periods of planned wind power output being restricted, a maximum blocked power of 50.97 MW, a curtailment rate of 6.86%, and a total restricted power of 372.81 MW·h. In scenario two, there are 12 periods of planned wind power output being restricted, a maximum blocked power of 40.11 MW, a curtailment rate of 4.25%, and a total restricted power of 231.22 MW·h. In the second scenario, due to the adjustment of the desalination load, the system's curtailment rate is 4.25%, a 38.05% reduction from the 6.86% curtailment rate in the first scenario. In summary, the adoption of the desalination load peaking strategy significantly improves wind power absorption and effectively reduces wind curtailment.

[0202] As shown in Table 4, the operating costs of thermal power units in the two scenarios are not much different. However, due to the enhanced system regulation capability and significantly increased wind power absorption in Scenario 2, the system's wind curtailment cost has been significantly reduced. Compared with Scenario 1, the total cost of system operation is lower. The use of seawater desalination load to participate in peak regulation and absorb blocked wind power has achieved considerable economic benefits.

[0203] 2. Verification of intraday optimization scheduling model.

[0204] With the shortening of the time scale of wind power and conventional load forecasting, the accuracy of wind power and conventional load forecasting is gradually improved, and the 15-minute power fluctuation is more detailed than the day-ahead 1h, so the super capacitor in the seawater desalination plant is introduced in the intraday scheduling stage, and the high-frequency component of the net load is decomposed by VMD to improve the capacity utilization.

[0205] Figure 13 and Figure 14 The intraday scheduling results of scenario one and scenario two are shown by Figure 13 and Figure 14 It can be seen that in scenario one and scenario two, in order to further reduce the operating cost of thermal power units, thermal power unit 3 undertakes most of the adjustment tasks, while thermal power units 1, 2 and 4 are almost in minimum output operation throughout the scheduling period. This is due to the influence of the operating cost of thermal power units per unit of power generation, and the specific parameters are shown in Table 1. In addition, all thermal power units from 1 to 18, 48 to 65 and 89 to 96 are in minimum output operation, because wind curtailment occurs in these time periods. In order to reduce wind curtailment, all thermal power units will be in minimum output. At the same time, compared with seawater desalination load not participating in adjustment, seawater desalination load participating in adjustment and coordinating with energy storage charging and discharging make the system load more smooth, thereby reducing the adjustment task of thermal power units and reducing wind curtailment during the period when wind curtailment occurs.

[0206] In order to further compare and analyze the operation of seawater desalination load and energy storage in scenarios one and two, as shown in Figure 15 and Figure 16 The local enlarged view is the operating state of the super capacitor. There is no obvious difference between the high-frequency components of the net load after being smoothed by the super capacitor in the two scenarios. In scenario two, compared with scenario one, when the net load is lower than the lower limit of the thermal power unit output, the seawater desalination load can continue to adjust upward in order to reduce the downward adjustment pressure of the thermal power unit, and when the net load is higher than the lower limit of the thermal power unit output, the seawater desalination load adjusts downward in order to reduce the thermal power unit output. It can be seen that after the high-frequency component of the net load is smoothed by the super capacitor, the net load fluctuation can be reduced to a certain extent, and the adjustment pressure of the thermal power unit is also effectively reduced through the coordination of seawater desalination load and battery.

[0207] Figure 17 and Figure 18 The operating states of the clear water tank and the product water tank in scenario two are shown by Figure 17 and Figure 18It can be seen that when the wind power output is relatively large and the conventional load power consumption is relatively small (1~18, 48~65, 89~96), in order to avoid the situation where the thermal power unit has insufficient capacity to reduce or even stops operating, the water intake pump and the high-pressure pump can adjust the power upward to take water and produce fresh water in advance, and the excess pre-treated water and fresh water are stored in the water tank. When the wind power output is small and the conventional load power consumption is large (19~47, 66~88), in order to reduce the output of the thermal power unit, the water intake pump and the high-pressure pump are adjusted downward to reduce the power consumption. When the water intake is not enough to meet the water demand for desalination, the clear water pool is released to meet the water demand for desalination. When the desalination water output is not enough to meet the water demand of residents, the product water pool is released to meet the water demand of residents. Figure 17 and Figure 18 The figure also shows frequent fluctuations in water intake from the intake pumps. This is due to the low energy consumption of the intake pumps. Even small power fluctuations can lead to large changes in water output. Compared to scenario 1, the desalination load can be flexibly adjusted by effectively utilizing the clear water tank and product water tank as a buffer, which will reduce the regulation pressure on the thermal power units.

[0208] Figure 19 The following chart compares wind power output and wind curtailment before and after desalination load regulation. In scenario one, the day is divided into 96 time periods, with 44 periods of planned wind power output restriction, a maximum blocked power of 70.09 MW, a wind curtailment rate of 6.74%, and a total restricted power of 391.67 MW·h. In scenario two, the day is divided into 96 time periods, with 36 periods of planned wind power output restriction, a maximum blocked power of 63.38 MW, a wind curtailment rate of 4.81%, and a total restricted power of 261.87 MW·h. This shows that scenario two, based on scenario one, reduces the wind curtailment rate by 28.64% by adjusting the desalination load up and down. In summary, the desalination load peaking strategy significantly improves wind power absorption and effectively reduces wind curtailment.

[0209] To further analyze the impact of VMD on supercapacitor charging and discharging, scenario 1 is further divided into two cases: considering VMD and not considering VMD. Figure 20 This is a comparison chart of supercapacitor output and SOC, Figure 20It can be seen that when VMD is not considered, the supercapacitor will charge or discharge continuously in a short period of time, causing its SOC to reach the upper or lower limit, which will cause the supercapacitor to fail to operate. However, when VMD is considered, because the high-frequency component conforms to the operating characteristics of the supercapacitor, the supercapacitor can be charged and discharged in a relatively short period of time, reducing the occurrence of the supercapacitor constantly charging or discharging, fully utilizing the device's responsiveness, and improving SOC utilization. In addition, the supercapacitor output in this example also shows that the supercapacitor still has a certain capacity margin, which is capable of absorbing the wind power generated by the prediction error when the wind power forecast error occurs.

[0210] The optimization results in Table 5 show that the operating costs of thermal power units in the two scenarios are similar. However, when VMD decomposition is considered in both scenarios, the supercapacitor scheduling costs differ. This is due to the influence of the unit wind curtailment cost and the unit supercapacitor scheduling cost. Since scenario one does not consider the regulation of seawater desalination load, the supercapacitor regulation is increased during the period of wind curtailment, resulting in lower supercapacitor regulation costs in scenario two than in scenario one. In addition, since scenario two considers the regulation of seawater desalination load, the regulation of energy storage equipment is reduced, and the wind curtailment rate is also reduced, ultimately resulting in lower total costs than scenario one. This shows that using seawater desalination load to participate in peak regulation and absorb blocked wind power has achieved considerable economic benefits.

[0211] Table 1 Thermal power unit operating parameters

[0212]

[0213] Table 2 Seawater desalination equipment operating parameters

[0214]

[0215] Table 3 Energy storage equipment operating parameters

[0216]

[0217] Table 4 Comparison of economic costs of the two scenarios

[0218]

[0219] Table 5 Comparison of economic costs of two scenarios within a day

[0220]

[0221] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A two-stage scheduling method for a regional water-energy coupling system including a seawater desalination plant, characterized by: include: In the established regional water-energy coupling framework system including desalination plants, a desalination load model is constructed based on the principle of satisfying desalination process constraints. The regional water energy coupling framework system including the seawater desalination plant includes: Construct a power supply system including wind power, thermal power units and batteries; construct a water supply system including seawater desalination load and supercapacitors; The power supply system and water supply system are coupled to obtain a regional water-energy coupling framework system including a seawater desalination plant, which is used to achieve the coordinated optimization of energy and water resources and is managed and regulated by the dispatching center; Based on the frequency component coordinated regulation mechanism of the net load and combined with the variational mode decomposition algorithm, the wind power absorption principle of the seawater desalination load model is analyzed and a wind power absorption mechanism is constructed; The frequency component coordinated regulation mechanism based on the net load is combined with the variational mode decomposition algorithm to analyze the wind power absorption principle of the seawater desalination load model and construct a wind power absorption mechanism including: According to the minimum output limit of the boiler and turbine of the thermal power unit and the load adjustment speed of the thermal power unit, the minimum technical output model of the thermal power unit is established; According to the minimum technical output model of the thermal power unit, determine the limitations of the thermal power unit on technical output and ramp rate; Based on the limitations of thermal power generation units on technical output and ramp rate, the regulation pressure of thermal power generation units is reduced by regulating the desalination load power. The net load is decomposed into components of different frequencies using the variational mode decomposition algorithm. The supercapacitors in the desalination plant are used to smooth the first frequency component of the net load; the desalination load, batteries and thermal power units are used to smooth the second frequency component of the net load; The wind power absorption mechanism is utilized to reduce the peak load regulation pressure of the generator units and suppress net load fluctuations. During the day-ahead dispatch phase, a day-ahead dispatch model is constructed with the optimization objectives of minimizing the penalty costs for wind curtailment, the coal consumption costs and startup and shutdown costs of thermal power units, and the charging and discharging costs of batteries. By solving the day-ahead dispatch model, a pre-allocation plan for the operation of thermal power units and batteries is obtained. During the intraday scheduling stage, the pre-allocation plan of the thermal power units and battery operations is used as the initial condition. Based on the constraints of supercapacitor operating costs and intraday plan adjustment costs, an intraday scheduling model is constructed to dynamically optimize the desalination load power, thermal power unit output deviation, and battery and supercapacitor charging and discharging strategies.

2. The method for scheduling a regional water-energy coupling system containing a seawater desalination plant in two stages, day-ahead and day-intraday, according to claim 1, is characterized in that: The seawater desalination load model is constructed based on the principle of satisfying the seawater desalination process constraints, including: Based on the power, efficiency, water flow rate, upper and lower limits of water flow rate, head, and working status of the water intake pump, and combined with the water density and gravitational acceleration, the water intake pump constraint conditions are established. The associated conditions for the power consumed by the high-pressure pump during the seawater desalination process are constructed. Based on the principle that the working pressure of the reverse osmosis unit is higher than the transmembrane osmotic pressure, and combined with the life factor of the reverse osmosis unit, the reverse osmosis unit constraint conditions, reverse osmosis unit ramp constraint conditions and reverse osmosis unit start and stop constraint conditions are established; Using the water levels, bottom areas, and total number of desalination units of the clean water and product water tanks, combined with the ratio of pretreated seawater to feed water flow, the product water tank effluent flow, the effluent flow of the reverse osmosis unit, the influent flow of the reverse osmosis unit, the intake flow of the intake pump, the upper and lower limits of the clean water tank water level, and the upper and lower limits of the product water tank water level, establish the constraints for the clean water and product tanks; Using the water levels and upper and lower limits of the water level difference of the clear water tank and product water tank within the scheduling period, the scheduling continuity constraint conditions are established; A seawater desalination load model is constructed, which includes water intake pump constraints, correlation conditions of high-pressure pump power consumption, reverse osmosis unit constraints, reverse osmosis unit ramp constraints, reverse osmosis unit start and stop constraints, clear water tank and product water tank constraints, and scheduling continuity constraints.

3. The method for scheduling a regional water-energy coupling system containing a seawater desalination plant in two stages, day-ahead and day-intraday, according to claim 2, characterized in that: Based on the principle that the working pressure of the reverse osmosis unit is higher than the transmembrane osmotic pressure, and in combination with the life factor of the reverse osmosis unit, the reverse osmosis unit constraint conditions, reverse osmosis unit ramp constraint conditions and reverse osmosis unit start-stop constraint conditions are established, including: Based on the principle that the working pressure of the reverse osmosis unit is higher than the transmembrane osmotic pressure, and using the upper and lower limits of the transmembrane net pressure of the reverse osmosis unit, the operating status value of the reverse osmosis unit, the working pressure of the reverse osmosis unit and the transmembrane osmotic pressure difference, the reverse osmosis unit constraint conditions are established; Establish the reverse osmosis unit climbing constraint conditions based on the reverse osmosis unit's climbing power upper and lower limits, the upper and lower limits of the working pressure increase and decrease per unit time period, the working pressure, and the high-pressure pump power; According to the single start-up and shutdown cost of the seawater desalination unit, the maximum start-up and shutdown cost within the scheduling cycle, the total number of scheduling periods, and the operating status value of the reverse osmosis unit, the start-up and shutdown constraints of the reverse osmosis unit are established.

4. The method for scheduling a regional water-energy coupling system containing a seawater desalination plant in two stages, day-ahead and day-intraday, according to claim 1, characterized in that: In the day-ahead dispatch phase, a day-ahead dispatch model is constructed with the optimization objectives of minimizing the wind power curtailment penalty cost, the coal consumption cost and startup and shutdown cost of thermal power units, and the battery charging and discharging cost. By solving the day-ahead dispatch model, the pre-allocation scheme for the thermal power units and battery operations is obtained, including: Determine the time resolution for the day-ahead dispatch phase. Based on this time resolution, obtain day-ahead wind power forecast data and load forecast data. Build a day-ahead dispatch model based on the optimization objectives of minimizing wind curtailment penalty costs, coal consumption costs and startup and shutdown costs of thermal power units, and battery charging and discharging costs. By solving the day-ahead dispatch model, the output curve and start-stop status of the thermal power units are determined, and the battery charge and discharge plan is formulated; The output curve of the thermal power unit, the start-stop status, and the battery charge and discharge plan are used as a pre-allocation plan for the thermal power unit and the battery operation.

5. The method for scheduling a regional water-energy coupling system containing a seawater desalination plant in two stages, day-ahead and day-intraday, according to claim 4, characterized in that: The constraints of the day-ahead scheduling model include: Based on the principle that active power and load are equal in any period, the power balance constraint condition of the day-ahead stage is established, and the wind power grid power is constrained with the wind power forecast power as the upper limit; Use the battery charging and discharging power from the grid, charging and discharging limits, and charging and discharging state parameters to construct battery charging and discharging constraint conditions; The battery capacity constraint is constructed using the battery storage capacity, charge and discharge efficiency, maximum capacity, upper and lower storage limits, charge and discharge power from the power grid, and charge and discharge status parameters.

6. The method for scheduling a regional water-energy coupling system including a seawater desalination plant in two stages, day-ahead and day-intraday, according to claim 1, characterized in that: In the intraday scheduling phase, the pre-allocation scheme of the thermal power units and the battery operation is used as the initial condition. Based on the constraints of the supercapacitor operation cost and the intraday plan adjustment cost, an intraday scheduling model is constructed to dynamically optimize the desalination load power, the output deviation of the thermal power units, and the charging and discharging strategies of the batteries and supercapacitors. The model includes: Determine the time resolution of the intraday scheduling stage, and obtain the scheduling plan within several time ranges based on the time resolution of the intraday scheduling stage; The dispatch plan uses updated ultra-short-term forecasts of wind power and load, and after frequency decomposition using the variational mode decomposition algorithm, the first frequency component is adjusted by supercapacitors, while the second frequency component is coordinated by the desalination load and batteries. Based on the day-ahead scheduling, the optimization objectives of the intraday scheduling phase, namely the operating cost of the newly added supercapacitors and the cost of adjusting the intraday plan, are determined. An intraday scheduling model is constructed to dynamically optimize the desalination load power, the output deviation of the thermal power units, and the charging and discharging strategies of batteries and supercapacitors.

7. The method for scheduling a regional water-energy coupling system containing a seawater desalination plant in two stages, day-ahead and day-intraday, according to claim 6, characterized in that: The time resolution of the day-ahead scheduling stage is greater than the time resolution of the intraday scheduling stage, so as to achieve the goals of day-ahead peak shaving and valley filling and intraday smoothing of power fluctuations.

8. The method for scheduling a regional water-energy coupling system including a seawater desalination plant in two stages, day-ahead and day-intraday, according to claim 6, characterized in that: The constraints of the intraday scheduling model include: Based on the principle that active power and load are equal in any period, the power balance constraint condition within the day is constructed; Using the supercapacitor charging and discharging power, charging and discharging limit and charging and discharging state parameters from the grid, the supercapacitor charging and discharging constraint conditions are constructed; The supercapacitor capacity constraint conditions are constructed using the supercapacitor's storage capacity, charging and discharging efficiency, maximum capacity, upper and lower storage limits, charging and discharging power from the power grid, and charging and discharging state parameters.

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