Matching method of off-grid seawater desalination system

Abstract

The invention discloses a matching method of an off-grid seawater desalination system. The matching method comprises the following steps: determining the treatment capacity of a seawater desalination device according to an island condition gap; collecting annual actual data of local light energy and wind energy of the island; drawing up a strategy for actively adjusting the operation load of the seawater desalination device; writing a simulation running program according to the formulated strategy; the simulation operation program can calculate required technical index parameters according to a unit wind power or photovoltaic power generation curve under the condition of given wind power, photovoltaic and energy storage installed capacity; assuming that a plurality of groups of wind power, photovoltaic and energy storage installed capacity schemes are combined, respectively calculating required technical index parameters of each scheme by utilizing a simulation running program, and selecting a scheme which can meet the required technical index parameters and has the lowest ton water cost as a final installed capacity scheme. According to the scheme, under the condition that stable operation of the seawater desalination equipment is guaranteed, the cost performance of correspondingly equipped power generation equipment is high, and the purpose of saving overall investment is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of seawater desalination, and in particular relates to a matching method for an off-grid seawater desalination system. Background Art

[0002] Islands are far from the land and lack fresh water resources, so desalination facilities are usually used to produce fresh water. However, because islands are far from the land, it is difficult to lay power grids.

[0003] With the development of new energy technologies, it is becoming increasingly popular to use solar energy and wind energy, which are within reach, as island power generation equipment. However, solar energy and wind energy are very sensitive to weather and climate, and their stability, continuity and reliability are very poor. They are a kind of random energy. This characteristic of solar energy and wind energy brings certain difficulties to the operation of island desalination devices. According to the different relationships between power generation equipment and the large power grid, it can be divided into grid-connected type, non-grid-connected type (connected to the grid but not connected to the grid) and off-grid type (island type). The first two types of power generation equipment are physically connected to the large power grid. Even as an independent power source, they can still rely on the support of the large power grid to ensure the relative stability of power supply through technical means. Their power supply characteristics are basically the same as those of conventional power grid power supply. The third type of off-grid type refers to power generation equipment that is not physically connected to the large power grid and operates truly independently.

[0004] my country's remote islands are sparsely populated. Building power grids on islands requires huge investment and low economic benefits, so independent power generation systems are generally used. At the same time, fresh water resources on islands are scarce, and seawater desalination technology is needed to produce fresh water. Seawater desalination requires power supply, so seawater desalination equipment on islands needs to be able to operate safely and stably for a long time without the support of the power grid.

[0005] With the development of new energy technologies, it is becoming increasingly popular to use solar energy and wind energy as island power generation equipment. However, solar energy and wind energy are very sensitive to weather and climate, and their stability, continuity and reliability are very poor. They are a kind of random energy. Although the characteristics of solar energy and wind energy in various regions generally follow certain rules over a long period of time, their intensity is constantly changing all the time. Not only does it change from year to year, but it also has irregular pulsating changes in a very short period of time. Seawater desalination equipment requires a stable power supply. If the unstable power generation equipment and the power consumption equipment with stable demand cannot be organically combined, the power generation equipment will have a poor cost performance and thus affect the investment, or the seawater desalination equipment will not be able to operate well. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a matching method for an off-grid desalination system to solve the problem that the existing solution cannot achieve long-term safe and stable operation of seawater desalination equipment on islands without power grid support. This solution formulates a coordination strategy to coordinate the design of solar energy, wind energy and seawater desalination devices, aiming to match and design a cost-effective new energy power supply system according to the processing capacity, operation mode and the changing laws of solar energy and wind energy of the seawater desalination device, so as to achieve the overall investment of the off-grid desalination system as much as possible while meeting the water supply requirements.

[0007] According to the technical solution of the present invention, the present invention provides a matching method for an off-grid seawater desalination system, comprising the following steps:

[0008] Step S1, determining the processing capacity of the seawater desalination device according to the gap in the island situation;

[0009] Step S2, collecting actual data of local solar energy and wind energy throughout the year on the island; wherein the actual data throughout the year refers to the hourly power generation of unit wind power and photovoltaic installed capacity throughout the year;

[0010] Step S3, formulating a strategy for active regulation of the operating load of the seawater desalination device;

[0011] Step S4, writing a simulation operation program according to the strategy formulated in step S3; the simulation operation program can calculate the required technical index parameters according to the unit wind power or photovoltaic power generation curve obtained in step S2 under the condition of given wind power, photovoltaic, and energy storage installed capacity; wherein the required technical index parameters include the total water production of seawater desalination throughout the year, the daily water production, and the average ton water cost;

[0012] Step S5, assuming multiple groups of wind power, photovoltaic, and energy storage installed capacity plan combinations, use the simulation operation program written in step S4 to calculate the required technical indicator parameters of each group of wind power, photovoltaic, and energy storage installed capacity plan combinations, and select the plan that can meet the required technical indicator parameters and has the lowest cost per ton of water as the final installed capacity plan.

[0013] Furthermore, step S3 to step S5 include determining the water production system parameters of the seawater desalination device, determining the upper and lower limits of the wind power, photovoltaic and energy storage installed capacity, and then generating a set of wind power, photovoltaic and energy storage installed capacity scheme combinations; then, for a set of wind power, photovoltaic and energy storage installed capacity scheme combinations, simulating the operation of the wind power, photovoltaic, energy storage and seawater desalination devices hour by hour in the simulation operation program, obtaining the data of the required technical indicator parameters, and completing the hourly cycle throughout the year in this way, statistically analyzing the technical indicators of the operation throughout the year, and then comparing or enumerating the next alternative plan through the optimization algorithm, repeating this process and finally selecting the best plan as the recommended plan.

[0014] Furthermore, the strategy described in step S3 includes the following:

[0015] The daily operation time of the desalination device is the water production period, which coincides with photovoltaic power generation;

[0016] During the water production period, the desalination device is judged whether to start according to the power generation situation every hour. The judgment method is that if the power generation provided by wind power and photovoltaic power is expected to be able to maintain the power consumption of the desalination system in the next few hours, the desalination device will start to operate;

[0017] After the desalination device is started, it will give priority to using wind power and photovoltaic real-time power generation for operation; if there is a shortage of wind power and photovoltaic power generation, the desalination device will be maintained by energy storage discharge;

[0018] If the wind power, photovoltaic real-time power generation and the remaining energy storage power are not enough to support the operation of the seawater desalination device, the seawater desalination device will be shut down;

[0019] At the end of each day's water production period, the day's water production is counted. If it does not meet the day's established water production demand, the desalination device will continue to operate for several hours until the water production demand is met or the electricity is exhausted, provided that wind power, photovoltaics, and energy storage can still provide sufficient electricity.

[0020] Furthermore, the water supply period is from 7:00 to 17:00 every day.

[0021] Furthermore, when deciding whether to start the seawater desalination device based on the hourly power generation situation, if it is estimated that the power generation provided by wind power and photovoltaic power in the next 1 to 3 hours can maintain the power consumption of the seawater desalination system, the seawater desalination device will be started and begin to operate.

[0022] Furthermore, steps S3 to S5 specifically include the following contents:

[0023] Four operating states of the desalination device are defined: startup, operation, shutdown, and standby. The desalination device is in one of these states every hour, and it takes one hour of transition from "standby" to "operation" in the "startup" state, and one hour of transition from "operation" to "standby" in the "shutdown" state. Each state has a corresponding power consumption, "operation" has a corresponding water production, and other states have no water production. Starting from the first hour of each year, the required technical indicators and parameters for each hour are calculated hour by hour, including at least power consumption, water production, and power abandonment.

[0024] Step S31, if the current time is before the start of the water production period, the seawater desalination device is in the "standby" state;

[0025] Step S32, during the water production period, if the seawater desalination device is in the "standby" state, read the power generation forecast values ​​of the current hour and the next several hours to determine whether they can meet the power consumption requirements of the seawater desalination device for startup and operation, if yes, the current hour state changes to "startup" and changes to "operation" in the next hour, if not, continue to maintain the "standby" state;

[0026] Step S33, during the water production period, if the seawater desalination device is already in the "operation" state, then read the current hourly power generation forecast value, if the "operation" state power consumption can be maintained, then maintain the "operation" state; if it is insufficient, then read the available power of the battery for calculating the energy storage, deduct the power reserved for 1 hour of "shutdown" and several hours of "standby", and add it to the current hourly power generation forecast value as the total available power, and judge whether the "operation" state power consumption can be maintained, if yes, then maintain the "operation" state, if not, then the state of the hour becomes "shutdown" and becomes "standby" in the next hour;

[0027] Step S34, after the water production period ends, count the number of hours in the "operation" state on that day, obtain the total amount of water produced on that day, compare it with the water production demand, and determine whether it meets the requirements. If so, the state of that hour changes to "off", and changes to "standby" in the next hour; if not, continue to maintain the "operation" state under the following two conditions, otherwise the state changes to "off", the first condition is that the current state is still "operation", and the second condition is that the total available power can meet the power consumption of the "operation" state; the calculation method of the total available power in this step is the same as that in step S33, that is, the current hourly power generation plus the available power of the battery for energy storage, minus the power reserved for 1 hour of "shutdown" and several hours of "standby";

[0028] Step S35, after the water production period ends and the desalination device returns to the "standby" state, the water production process for the day ends, and the total water production for the day is counted;

[0029] Step S36, return to step S31 and continue the cycle until the full-year simulation is completed;

[0030] Step S37, statistically calculate the annual operation technical indicators, which at least include the total annual seawater desalination water production, average ton water cost, and abandoned electricity as a basis for scheme comparison.

[0031] Furthermore, the method further includes, in steps S31 to S35, determining the power consumption of the hour according to the state of the seawater desalination device; if there is surplus power and the energy storage battery is not fully charged, charging the energy storage battery; if the energy storage battery is fully charged, discarding the surplus power;

[0032] Furthermore, in step S5, it is necessary to assume that there are more than one hundred groups of wind power, photovoltaic, and energy storage options.

[0033] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0034] The key point of the present invention is to find a design matching strategy that organically coordinates unstable power generation equipment with power consumption equipment with stable demand. The present invention organically combines unstable power generation equipment with power consumption equipment with stable demand through a coordinated matching strategy, so that under the condition of ensuring the stable operation of the seawater desalination equipment, the corresponding power generation equipment has a high cost performance ratio, thereby achieving the purpose of saving overall investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is an overall basic flow chart of the method according to an embodiment of the present invention.

[0036] Figure 2 It is a logic block diagram of the main steps according to an embodiment of the present invention.

[0037] Figure 3 It is a data statistical chart of a certain day according to an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The present invention provides a matching method for an off-grid desalination system, which solves the problem that the existing solution cannot achieve long-term safe and stable operation of seawater desalination equipment on islands without power grid support. The present invention intends to coordinate the design of light energy, wind energy and seawater desalination devices by formulating a coordination strategy, aiming to match and design a cost-effective new energy power supply system according to the processing capacity, operation mode and the changing laws of light energy and wind energy of the seawater desalination device, so as to achieve the overall investment of the off-grid desalination system as much as possible while meeting the water supply requirements.

[0039] See also Figure 1 A matching method for an off-grid seawater desalination system according to an embodiment of the present invention is particularly suitable for an island having wind power, photovoltaic power and corresponding energy storage equipment (referred to as wind power, photovoltaic power and energy storage in the present invention; energy storage is, for example, electrochemical energy storage). The method of the present invention comprises the following steps:

[0040] Step S1, determining the processing capacity of the seawater desalination device according to the gap in the island situation (corresponding to the "water production demand" that the seawater desalination device needs to provide every day).

[0041] Step S2, collecting actual data of local solar energy and wind energy throughout the year on the island; wherein the actual data throughout the year refers to the hourly power generation of unit wind power and photovoltaic installed capacity throughout the year (i.e., unit wind and solar power output data).

[0042] Step S3, formulate a strategy for actively adjusting the operating load of the seawater desalination device, and adjust it according to the changes in the output of wind power and photovoltaic power.

[0043] Step S4, writing a simulation operation program according to the strategy formulated in step S3; the simulation operation program can calculate the required technical indicator parameters based on the unit wind power or photovoltaic power generation curve obtained in step S2 under the condition of given wind power, photovoltaic, and electrochemical energy storage installed capacity; wherein the required technical indicator parameters include, for example, the total water production of seawater desalination throughout the year, the daily water production (such as curve form), the average cost per ton of water, etc.

[0044] Step S5, assuming multiple groups of wind power, photovoltaic, and electrochemical energy storage installed capacity scheme combinations, respectively use the simulation operation program written in step S4 to calculate the required technical index parameters of each scheme (especially the cost per ton of water), and select the scheme that can meet the remaining required technical index parameters and has the lowest cost per ton of water as the final installed capacity scheme. This step S5 generally requires at least hundreds of groups of candidate schemes to be compared; for example, it is necessary to assume that more than one hundred groups of wind power, photovoltaic, and energy storage candidate schemes are available for comparison and selection. More specifically, there can be two types of methods. One is to list all possible combinations within a certain range and with a certain step length by an exhaustive method when the number of variables is small (for example, when there are only two variables to be determined, photovoltaic and electrochemical energy storage), calculate and compare; the other method is to use an optimization algorithm, take the cost per ton of water as the objective function, and adjust the annual total water production as an inequality constraint, and use a particle swarm algorithm, a genetic algorithm, etc. to find a combination of schemes that meets the requirements and has the lowest cost. These algorithms are mature technologies. The embodiment of the present invention adopts the second method.

[0045] A more specific method flow is as follows Figure 2 As shown. Steps S3 to S5 include determining the water system parameters of the desalination device, determining the upper and lower limits of the wind power, photovoltaic and energy storage installed capacity, and then generating a set of wind power, photovoltaic and energy storage installed capacity scheme combinations. Next, for a set of wind power, photovoltaic and energy storage installed capacity scheme combinations, the operation of wind power, photovoltaic, energy storage and seawater desalination devices (water system) is simulated hourly in the simulation operation program to obtain the data of the required technical indicator parameters such as power generation, power consumption and water production, and complete the hourly cycle throughout the year, calculate the technical indicators of the operation throughout the year, and then compare or enumerate the next alternative plan through the optimization algorithm, repeat this process and finally select the best plan as the recommended plan.

[0046] Further, for the strategy described in step S3, a specific strategy is proposed below, and the principle of the strategy is:

[0047] The daily operating hours of the seawater desalination device are, for example, from 7:00 to 17:00 every day, which is defined as the "water production period". The water production period coincides with photovoltaic power generation, and the specific start and end times can be adjusted according to actual conditions.

[0048] During the water production period, the decision on whether to start the seawater desalination device is made based on the hourly power generation situation. The judgment method is that if it is expected that the power generation provided by wind power and photovoltaic power will be able to maintain the power consumption of the seawater desalination system (water production system) in the next few hours (for example, 1 to 3 hours), the seawater desalination device will be started and begin to operate.

[0049] After the desalination device (water production system) is started, priority will be given to the use of wind power and photovoltaic real-time power generation for operation. If there is insufficient wind power and photovoltaic power generation, it is allowed to rely on energy storage discharge to maintain the operation of the desalination device (water production system).

[0050] If the real-time power generation from wind power, photovoltaic power generation and the remaining power from energy storage are not sufficient to support the operation of the desalination device, the desalination device will be shut down.

[0051] At the end of the designated water production period each day (such as 17:00), the water production for the day is counted. If the water production demand for the day is not met, the desalination device will continue to operate for several hours until the water production demand is met or the electricity is exhausted, provided that wind power, photovoltaic power and energy storage can still provide sufficient electricity.

[0052] According to the above principles, the hourly operation process can be compiled more specifically as follows:

[0053] Four operating states are defined for a desalination device: startup, operation, shutdown, and standby. The desalination device is in one of these states every hour, and it takes one hour of transition from the "startup" state to "standby" to "operation", and one hour of transition from the "shutdown" state to "operation" to "standby". Each state has a corresponding power consumption, "operation" has a corresponding water production, and other states have no water production; see the table below.

[0054] Starting from the first hour of each year, the required technical indicator parameters for each hour are calculated on an hourly basis, including at least power consumption, water production, and power abandonment, and the accumulated data are used for subsequent comparisons.

[0055] Step S31: if the current time is before the start of the water production period (such as before 7:00), the seawater desalination device is in the "standby" state.

[0056] Step S32, during the water production period (such as 7:00-17:00), if the seawater desalination device is in the "standby" state, read the power generation forecast value of the current hour and the next few hours (such as 2 hours) to determine whether it can meet the power consumption requirements for starting and running the seawater desalination device respectively. If so, the current hour state is changed to "startup" and changed to "running" in the next hour. If not, continue to maintain the "standby" state.

[0057] Step S33, during the water production period (such as 7:00-17:00), if the desalination device is already in the "operation" state, then read the current hourly power generation forecast value, if the "operation" state power consumption can be maintained, then keep the "operation" state; if it is insufficient, then read the battery available power for calculating energy storage, deduct the power reserved for 1 hour of "shutdown" and several hours of "standby" (such as 12 hours), and add it to the current hourly power generation forecast value as the total available power, and judge whether the "operation" state power consumption can be maintained, if yes, then keep the "operation" state, if not, then the state of the hour becomes "shutdown" and becomes "standby" in the next hour;

[0058] Step S34, after the water production period ends (such as after 17:00), the number of hours in the "operation" state of the day is counted to obtain the current total water production of the day, and compared with the water production demand to determine whether the requirements are met (for example, greater than or equal to the water production demand of the day, or the standard for meeting the requirements is set as the current total water production of the day is within a certain range near the water production demand, etc.), if satisfied, the state of the hour becomes "off", and becomes "standby" in the next hour; if not, the "operation" state is maintained under the following two conditions, otherwise the state becomes "off", condition one is that the current state is still "operation", condition two is that the total available power can meet the power consumption of the "operation" state; the total available power calculation method in this step is the same as that in step S33, that is, the current hourly power generation plus the available power of the energy storage battery, minus the power reserved for 1 hour of "shutdown" and several hours of "standby" (such as 12 hours).

[0059] Step S35, after the water production period ends and the desalination device status returns to "standby", the water production process for the day is completed, and the total water production and total shortage for the day are counted (the shortage refers to the difference between the current water production situation and the demand. For example, 0 in the table below means that there is no shortage at present and the water production meets the demand).

[0060] Preferably, in steps S31 to S35, the power consumption for that hour is determined according to the state of the seawater desalination device; if there is surplus power and the energy storage battery is not fully charged, the energy storage battery is charged; if the energy storage battery is fully charged, the surplus power is discarded.

[0061] Step S36, return to step S31 and continue the cycle until the full-year simulation is completed;

[0062] Step S37, statistically calculate the annual operation technical indicators, which at least include the annual total seawater desalination water production, average ton water cost, and abandoned electricity as a basis for scheme comparison.

[0063] Through the above process, the calculation results are obtained. For example, the data for a certain day is as follows: Figure 3 As shown:

[0064] time Battery charge Power generation Battery Discharge load Battery Charging Power abandonment Water production Hour of the day Vacancies Status Number state 1 147.31 0.00 0.50 -0.50 0.00 0.00 0 0 0 4 Standby 2 146.75 0.00 0.50 -0.50 0.00 0.00 0 0 0 4 Standby 3 146.20 0.00 0.50 -0.50 0.00 0.00 0 0 0 4 Standby 4 145.64 0.00 0.50 -0.50 0.00 0.00 0 0 0 4 Standby 5 145.09 0.00 0.50 -0.50 0.00 0.00 0 0 0 4 Standby 6 144.53 0.00 0.50 -0.50 0.00 0.00 0 0 0 4 Standby 7 147.14 3.40 0.00 -0.50 -2.90 0.00 0 0 0 4 Standby 8 136.47 23.00 9.60 -32.60 0.00 0.00 0 0 0 1 start up 9 150.64 53.08 0.00 -32.60 -15.75 -4.73 5 1 0 2 run 10 150.64 76.25 0.00 -32.60 0.00 -43.65 5 2 0 2 run 11 150.64 96.57 0.00 -32.60 0.00 -63.97 5 3 0 2 run 12 150.64 111.58 0.00 -32.60 0.00 -78.98 5 4 0 2 run 13 150.64 115.65 0.00 -32.60 0.00 -83.05 5 5 0 2 run 14 150.64 113.80 0.00 -32.60 0.00 -81.20 5 6 0 2 run 15 150.64 100.55 0.00 -32.60 0.00 -67.95 5 7 0 2 run 16 150.64 81.89 0.00 -32.60 0.00 -49.29 5 8 0 2 run 17 150.64 54.50 0.00 -32.60 0.00 -21.90 5 9 0 2 run 18 150.64 23.74 0.00 -5.50 0.00 -18.24 0 9 0 3 Finish 19 150.64 2.90 0.00 -0.50 0.00 -2.40 0 9 0 4 Standby 20 150.09 0.00 0.50 -0.50 0.00 0.00 0 9 0 4 Standby 21 149.53 0.00 0.50 -0.50 0.00 0.00 0 9 0 4 Standby 22 148.98 0.00 0.50 -0.50 0.00 0.00 0 9 0 4 Standby 23 148.42 0.00 0.50 -0.50 0.00 0.00 0 9 0 4 Standby 24 147.87 0.00 0.50 -0.50 0.00 0.00 0 9 0 4 Standby

[0065] The statistical technical indicators of the whole year operation include the following table:

[0066]

[0067] It can be seen that by using the matching model of the present invention, more economical wind, light and energy storage can be configured according to the water production capacity of the seawater desalination device and the changing rules of local wind and light resources, so as to optimize the cost performance of the entire off-grid seawater desalination device.

[0068] In summary, the key point of the present invention is to find a design matching strategy that organically coordinates unstable power generation equipment and power consumption equipment with stable demand. The present invention organically combines unstable power generation equipment and power consumption equipment with stable demand through a coordinated matching strategy, so that under the condition of ensuring the stable operation of the seawater desalination equipment, the corresponding power generation equipment has a high cost performance, thereby achieving the purpose of saving overall investment.

Claims

1. A matching method for an off-grid seawater desalination system, characterized in that: The steps include: Step S1, determining the processing capacity of the seawater desalination device according to the gap in the island situation; Step S2, collecting actual data of local solar energy and wind energy throughout the year on the island; wherein the actual data throughout the year refers to the hourly power generation of unit wind power and photovoltaic installed capacity throughout the year; Step S3, formulating a strategy for active regulation of the operating load of the seawater desalination device; Step S4, writing a simulation operation program according to the strategy formulated in step S3; the simulation operation program can calculate the required technical index parameters according to the unit wind power or photovoltaic power generation curve obtained in step S2 under the condition of given wind power, photovoltaic, and energy storage installed capacity; wherein the required technical index parameters include the total water production of seawater desalination throughout the year, the daily water production, and the average ton water cost; Step S5, assuming multiple groups of wind power, photovoltaic, and energy storage installed capacity plan combinations, use the simulation operation program written in step S4 to calculate the required technical indicator parameters of each group of wind power, photovoltaic, and energy storage installed capacity plan combinations, and select the plan that can meet the required technical indicator parameters and has the lowest cost per ton of water as the final installed capacity plan.

2. The matching method of the off-grid seawater desalination system according to claim 1, characterized in that: Steps S3 to S5 include determining the water system parameters of the seawater desalination device, determining the upper and lower limits of the wind power, photovoltaic and energy storage installed capacity, and then generating a set of wind power, photovoltaic and energy storage installed capacity scheme combinations; then, for a set of wind power, photovoltaic and energy storage installed capacity scheme combinations, simulating the operation of the wind power, photovoltaic, energy storage and seawater desalination devices hour by hour in the simulation operation program, obtaining the data of the required technical indicator parameters, and completing the hourly cycle throughout the year in this way, statistically analyzing the technical indicators of the operation throughout the year, and then comparing or enumerating the next alternative plan through the optimization algorithm, repeating this process to finally select the best plan as the recommended plan.

3. The matching method of the off-grid seawater desalination system according to claim 1, characterized in that: The strategy described in step S3 includes the following: The daily operation time of the desalination device is the water production period, which coincides with photovoltaic power generation; During the water production period, the desalination device is judged whether to start according to the power generation situation every hour. The judgment method is that if the power generation provided by wind power and photovoltaic power is expected to be able to maintain the power consumption of the desalination system in the next few hours, the desalination device will start to operate; After the desalination device is started, it will give priority to using wind power and photovoltaic real-time power generation for operation; if there is a shortage of wind power and photovoltaic power generation, the desalination device will be maintained by energy storage discharge; If the wind power, photovoltaic real-time power generation and the remaining energy storage power are not enough to support the operation of the seawater desalination device, the seawater desalination device will be shut down; At the end of each day's water production period, the day's water production is counted. If it does not meet the day's established water production demand, the desalination device will continue to operate for several hours until the water production demand is met or the electricity is exhausted, provided that wind power, photovoltaics, and energy storage can still provide sufficient electricity.

4. The matching method of the off-grid seawater desalination system according to claim 3, characterized in that: The water supply period is from 7:00 to 17:00 every day.

5. The matching method of the off-grid seawater desalination system according to claim 3, characterized in that: When deciding whether to start the seawater desalination device based on the hourly power generation situation, if it is estimated that the power generation provided by wind power and photovoltaic power in the next 1 to 3 hours can maintain the power consumption of the seawater desalination system, the seawater desalination device will be started and operated.

6. The matching method of the off-grid seawater desalination system according to claim 3, characterized in that: Steps S3 to S5 specifically include the following contents: Four operating states of the desalination device are defined: startup, operation, shutdown, and standby. The desalination device is in one of these states every hour, and it takes one hour of "startup" state transition from "standby" to "operation", and one hour of "shutdown" state transition from "operation" to "standby". Each state has corresponding power consumption, "operation" has corresponding water production, and other states have no water production. Starting from the first hour of each year, the required technical indicators and parameters for each hour are calculated hour by hour, including at least power consumption, water production, and power abandonment. Step S31, if the current time is before the start of the water production period, the seawater desalination device is in the "standby" state; Step S32, during the water production period, if the desalination device is in the "standby" state, read the power generation forecast values ​​of the current hour and the next several hours to determine whether they can meet the power consumption requirements of the desalination device for startup and operation, respectively. If yes, the current hour state changes to "startup" and changes to "operation" in the next hour; if no, continue to maintain the "standby" state; Step S33, during the water production period, if the seawater desalination device is already in the "operation" state, then read the current hourly power generation forecast value, if the "operation" state power consumption can be maintained, then maintain the "operation" state; if it is insufficient, then read the available power of the battery for calculating the energy storage, deduct the power reserved for 1 hour of "shutdown" and several hours of "standby", and add it to the current hourly power generation forecast value as the total available power, and judge whether the "operation" state power consumption can be maintained, if yes, then maintain the "operation" state, if not, then the state of the hour becomes "shutdown" and becomes "standby" in the next hour; Step S34, after the water production period ends, the number of hours in the "operation" state of the day is counted to obtain the current total water production of the day, and compared with the water production demand to determine whether the requirements are met. If so, the state of the hour is changed to "off" and changed to "standby" in the next hour; if not, the "operation" state is maintained under the following two conditions, otherwise the state is changed to "off", the first condition is that the current state is still "operation", and the second condition is that the total available power can meet the power consumption of the "operation" state; the calculation method of the total available power in this step is the same as that in step S33, that is, the current hourly power generation plus the available power of the energy storage battery, minus the power reserved for 1 hour of "off" and several hours of "standby"; Step S35, after the water production period ends and the desalination device returns to the "standby" state, the water production process for the day ends, and the total water production for the day is counted; Step S36, return to step S31 and continue the cycle until the full-year simulation is completed; Step S37, statistically calculate the annual operation technical indicators, which at least include the annual total seawater desalination water production, average ton water cost, and abandoned electricity as a basis for scheme comparison.

7. The matching method of the off-grid seawater desalination system according to claim 6, characterized in that: It also includes, in steps S31 to S35, determining the power consumption for that hour according to the state of the seawater desalination device; if there is surplus power and the energy storage battery is not full, charging the energy storage battery; if the energy storage battery is full, discarding the surplus power.

8. The matching method of the off-grid seawater desalination system according to claim 1, characterized in that: In step S5, it is necessary to assume that there are more than one hundred groups of wind power, photovoltaic, and energy storage options.

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