Electric heating fused salt control method for fused salt heat storage

Abstract

The invention relates to the field of fused salt heat storage control, and particularly discloses an electric heating fused salt control method for fused salt heat storage, which comprises the following steps: S1, generating a surplus electric power curve according to power generation and power utilization end predicted power, judging a charging condition based on surplus electric quantity and stability, and if yes, predicting a charging starting moment, duration and average power, and triggering heat storage; s2, monitoring key temperature parameters of the system, and judging and executing preheating in combination with an allowable injection temperature interval and a uniformity requirement; s3, after the charging starting time is reached, the electric heating power is determined based on the cold tank state, the target heat storage temperature and the charging duration, and the flow of the molten salt pump is adjusted according to the average charging power and fluctuation; and S4, the heat storage state and the charging power are monitored in real time in the heating process, and charging is stopped when the heat tank is nearly full or the charging condition is not met. Through dynamic optimization of the safe preheating and heating process before charging, the absorption capacity, the operation safety and the overall efficiency of the heat storage system are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of molten salt heat storage control, and relates to a molten salt heat storage electric heating molten salt control method. BACKGROUND

[0002] As a highly efficient large-scale heat storage method, molten salt heat storage technology has attracted widespread attention in recent years in the fields of renewable energy consumption, power grid peak shaving, and industrial waste heat utilization. This technology converts surplus power or off-peak power into heat energy stored in molten salt, and releases it when needed for power generation or heating, thereby improving energy utilization efficiency and system operation flexibility. In a molten salt heat storage system, electric heating of molten salt is a key link for the conversion of electrical energy to thermal energy, and the control strategy directly affects the heat storage efficiency, system safety, and operation economy.

[0003] Existing molten salt heat storage electric heating control methods mostly focus on temperature and flow regulation during the heating process. For example, the Chinese patent with the authorization announcement number CN115615010B discloses a molten salt heat storage system electric heating molten salt temperature control method and system, which predicts molten salt flow based on total electric heating power, and corrects the flow through multi-stage electric heater power distribution and outlet temperature prediction to stabilize the control scheme of molten salt temperature. Although this method can to some extent avoid fluctuations in molten salt temperature, it still has the following shortcomings: (1) Existing methods usually take fixed or preset power input as a premise, without fully considering the time-varying, intermittent, and fluctuating nature of surplus power on the grid side, and cannot dynamically decide the heating time and power according to real-time power prediction at the power generation end and the power consumption end, resulting in insufficient consumption of surplus power by the heat storage system and delayed response.

[0004] (2) Existing control processes mostly directly enter the main heating stage without systematically evaluating and preheating controlling the temperature state of key parts of the heat storage system before charging. Directly injecting molten salt or starting heating in a low-temperature environment can easily cause molten salt solidification, equipment thermal stress damage, and other safety hazards.

[0005] (3) Existing methods mostly rely on fixed time or simple threshold for the termination of the heating process, without considering the dynamic changes of heat tank heat storage state and real-time charging power conditions, which may cause energy waste due to continued ineffective heating when the heat storage is full, or affect the overall efficiency and safety of the system due to failure to exit in time when external power conditions deteriorate.

[0006] Therefore, there is an urgent need for a molten salt heat storage electric heating control method that can intelligently respond to changes in surplus power, ensure safe system startup, and intelligently determine the charging end time, to improve the overall economy, safety, and adaptability of the heat storage system. SUMMARY

[0007] To address the above problems, this invention proposes an electric heating molten salt control method for molten salt thermal storage. The specific technical solution is as follows: An electric heating molten salt control method for molten salt thermal storage includes the following steps: Step S1: Based on the predicted power data of the power generation end and the power consumption end, generate a surplus power curve. Based on the surplus power and the stability of the surplus power, determine whether the charging conditions are met. If they are met, predict the start time, duration, and average power of charging, trigger molten salt thermal storage, and proceed to step S2. Otherwise, continue to monitor the surplus power.

[0008] Step S2: Monitor the current key temperature parameters of the thermal storage system, and determine whether preheating is required based on the allowable injection temperature range and temperature uniformity requirements. If preheating is required, preheat before the start of charging and proceed to step S3 after completion. If preheating is not required, proceed directly to step S3.

[0009] Step S3: After the charging start time is reached, the thermal storage system is started to heat up. The electric heating power is determined based on the cold tank status data, the target thermal storage temperature and the charging time. The molten salt pump flow rate is set and adjusted based on the average charging power and power fluctuation.

[0010] Step S4: During the heating process, monitor the heat storage status and charging power change trend in real time. When the hot tank is close to full storage or the charging conditions are no longer met, terminate the charging and exit the molten salt heat storage.

[0011] Compared with the prior art, the electric heating molten salt control method for molten salt thermal storage described in this invention has the following beneficial effects: 1. By generating a surplus power curve and judging charging conditions, predicting charging periods and average power based on surplus power and stability, this invention enables the thermal storage system to accurately capture and utilize the surplus power window of the power grid, solving the problem that the prior art ignores the dynamics of power supply and demand and cannot actively adapt to intermittent surplus power.

[0012] 2. By monitoring key temperature parameters and combining the allowable injection temperature range and uniformity requirements, this invention intelligently judges and executes preheating to ensure that the temperature of key parts of the system is within a safe range before molten salt injection and main heating is started. This effectively prevents solidification risks and structural damage, and ensures the long-term safe operation of the system.

[0013] 3. This invention achieves intelligent closed-loop management of the charging process by monitoring the heat storage status and charging power trend of the hot tank in real time, and intelligently terminating charging when the tank is full or the power is insufficient. This prevents overheating and energy waste, and ensures timely and safe shutdown when external power conditions deteriorate, thereby improving the system's automation level, safety, and overall operational efficiency. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the method flow of the present invention.

[0016] Figure 2 This is a schematic diagram of the overall control flow of the present invention.

[0017] Figure 3 This is a flowchart of the heating termination determination process of the present invention. Detailed Implementation

[0018] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of an electrically heated molten salt control method for molten salt heat storage proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0020] The specific scheme of the electrically heated molten salt control method for molten salt heat storage provided by the present invention will be described in detail below with reference to the accompanying drawings.

[0021] Please see Figure 1 and Figure 2 As shown, the present invention provides an electric heating molten salt control method for molten salt thermal storage, which includes the following steps: Step S1: Generate a surplus power curve based on the predicted power data of the power generation end and the power consumption end, and determine whether the charging conditions are met based on the surplus power and the stability of the surplus power. If the conditions are met, predict the start time, duration and average power of charging, trigger molten salt thermal storage and proceed to step S2; otherwise, continue to monitor the surplus power.

[0022] In one embodiment of the present invention, to achieve efficient and safe charging control of the molten salt thermal storage system, it is first necessary to identify whether there is surplus power available for thermal storage based on power prediction data from the power generation and consumption ends, and determine whether it meets the charging conditions. If the conditions are met, the start time, duration, and average power of charging are further predicted, thereby triggering the molten salt thermal storage process and providing a basis for subsequent heating control.

[0023] Considering that power prediction data for both the power generation and consumption ends are usually in time series form, in order to accurately identify surplus power, it is necessary to align the two in time series and calculate the difference between the power generation and consumption ends point by point, thereby generating a surplus power power curve that reflects the change of surplus power over time, providing a data basis for subsequent judgment on whether charging conditions are met.

[0024] Based on this, in a preferred embodiment of the present invention, the method for generating surplus power curves includes: obtaining the predicted power time series of the power generation end and the power consumption end, and performing time series alignment.

[0025] Starting from the first time point of the time series, the power generation power and power consumption power corresponding to that time point are obtained. The power generation power is subtracted from the power consumption power to calculate the surplus power corresponding to the first time point.

[0026] By sequentially traversing each time point in the time series, the surplus power corresponding to each time point is calculated to form a surplus power sequence.

[0027] Based on the surplus power sequence, a surplus power curve is generated with time as the horizontal axis and surplus power as the vertical axis.

[0028] After generating the surplus power curve, it is possible to further determine whether there is a charging opportunity that can be used for molten salt thermal storage based on the curve.

[0029] Since the surplus power curve may contain segments with large fluctuations or short durations, directly using it for charging may lead to frequent system start-stops or low efficiency. Therefore, it is necessary to identify the target curve segment above the baseline (i.e., when the surplus power is zero) and assess whether the corresponding surplus power reaches the set threshold. At the same time, it is necessary to determine whether the surplus power in this segment is stable, thereby comprehensively determining whether the charging conditions are met.

[0030] Based on this, in a preferred embodiment of the present invention, the method for determining whether the charging conditions are met includes: using a straight line with zero surplus power as a baseline.

[0031] Identify the curve segment in the surplus power curve that is above the baseline and denote it as the target curve segment.

[0032] The surplus power corresponding to each target curve segment is calculated based on the area enclosed by the target curve segment and the baseline, and it is determined whether the surplus power corresponding to each target curve segment is stable.

[0033] The number of target curve segments with surplus electricity exceeding a set threshold and stable surplus electricity is counted.

[0034] If there is at least one target curve segment that meets the above conditions, then the charging conditions are deemed to be met; otherwise, the charging conditions are deemed not to be met.

[0035] In a preferred embodiment of the present invention, the method for determining whether the surplus power corresponding to the target curve segment is stable includes: obtaining the surplus power corresponding to each point on the target curve segment.

[0036] Determine whether the following conditions are met simultaneously: (1) The surplus power at each point is greater than the preset available power threshold.

[0037] (2) The change in surplus power between adjacent data points is less than the set fluctuation threshold.

[0038] If both conditions are met, the surplus power corresponding to the target curve segment is determined to be stable; otherwise, it is determined to be unstable.

[0039] If the charging conditions are met, it is necessary to further predict the start time, duration, and average power of charging from the target curve segment that meets the conditions, so as to provide time and power basis for the subsequent specific execution of molten salt thermal storage.

[0040] Based on this, in a preferred embodiment of the present invention, the method for predicting the start time, duration and average power of charging includes: if there is only one target curve segment that meets the conditions, then the time point corresponding to the start point of the target curve segment is taken as the start time of charging, the interval between the time points corresponding to the start and end points is taken as the charging duration, and the average value of the surplus power corresponding to each point on the target curve segment is taken as the average charging power.

[0041] If there are multiple target curve segments that meet the conditions, the time point corresponding to the starting point of the target curve segment with the earliest starting point is taken as the charging start time, the cumulative value of the charging time corresponding to each target curve segment is taken as the final charging time, and the average value of the charging average power corresponding to each target curve segment is taken as the final charging average power.

[0042] It should be noted that when multiple target curve segments that meet the conditions are discontinuous, the charging process may include at least one charging period, and the charging periods may be discontinuous.

[0043] In another specific embodiment, if there are multiple target curve segments that meet the conditions, one of the target curve segments is selected as the charging period. The curve segment with the largest surplus power or the most stable surplus power is preferred. The time point corresponding to its starting point is the charging start time, the interval between the time points corresponding to its starting point and the ending point is the charging duration, and the average value of the surplus power corresponding to each point on the curve segment is taken as the average charging power.

[0044] It should be noted that in practical applications, there may be multiple target curve segments that meet the conditions, and their time distribution may be continuous or intermittent. To adapt to different operating strategies, this invention provides multiple charging period selection methods: one can select the earliest starting curve segment for continuous charging, or accumulate the total duration of multiple curve segments for intermittent charging, or select the curve segment with the largest or most stable surplus power as the optimal charging period, thereby improving the flexibility and economy of the thermal storage system.

[0045] After predicting the charging period, it is necessary to monitor the status of the thermal storage system before charging begins, especially the monitoring of key temperature parameters, to ensure that the system is in a state where molten salt can be safely injected.

[0046] Step S2: Monitor the current key temperature parameters of the thermal storage system, and determine whether preheating is required based on the allowable injection temperature range and temperature uniformity requirements. If preheating is required, preheat before the start of charging and proceed to step S3 after completion. If preheating is not required, proceed directly to step S3.

[0047] After molten salt thermal storage is triggered, key temperature parameters of the thermal storage system must be monitored before charging begins to determine whether the system has reached the permissible temperature conditions for molten salt injection. If not, preheating is required before the start of charging to avoid equipment damage and operational risks caused by molten salt solidification or uneven temperature.

[0048] Given the high freezing point of molten salt, directly injecting it into a system with an excessively low temperature can easily lead to localized solidification, blockage, or stress concentration. Therefore, it is necessary to determine the permissible injection temperature range based on the freezing point and safety margin of the molten salt, and to comprehensively assess whether the system has reached the safe operating threshold by considering the uniformity requirements of equipment temperature difference, pump body temperature difference, and other factors.

[0049] Based on this, in a preferred embodiment of the present invention, the method for determining whether preheating is required includes: monitoring the current key temperature parameters of the thermal storage system, wherein the key temperature parameters include the lowest point temperature of the equipment and the temperature difference of the equipment, the temperature of the molten salt pump body and the temperature difference between the top and bottom of the pump body.

[0050] The allowable injection temperature range is determined based on the freezing point of the molten salt and the preset safety margin.

[0051] Based on the set temperature uniformity requirements, the allowable ranges for the temperature difference of the equipment and the temperature difference between the top and bottom of the molten salt pump body are determined respectively.

[0052] To determine whether the equipment structure safety conditions are met, the conditions are: the temperature at the lowest point of the equipment is within the allowable injection temperature range, and the temperature difference of the equipment is within the corresponding allowable range.

[0053] To determine whether the pump body temperature condition is met, the condition is that the temperature of the molten salt pump body is within the allowable injection temperature range, and the temperature difference between the upper and lower parts of the pump body is within the corresponding allowable range.

[0054] If either the safety conditions of the equipment structure or the temperature conditions of the pump body are not met, it is determined that preheating is required; otherwise, it is determined that preheating is not required.

[0055] It should be noted that the allowable injection temperature is the operational safety threshold. Only after reaching this temperature is it permissible to inject molten salt into the system or start the main process.

[0056] As an example, the molten salt has a freezing point of 220°C and a safety margin of 70-100°C. Based on this, the allowable injection temperature range is determined to be 290°C to 320°C.

[0057] If preheating is required, the preheating system must be started before the start of charging to raise the system temperature to within the allowable injection temperature range and ensure uniform temperature distribution, thus creating conditions for subsequent formal heating.

[0058] To efficiently complete preheating, the required preheating time needs to be estimated based on the difference between the current system's lowest temperature and the target preheating temperature, combined with the heating power of the preheating system. Based on this, the start time of preheating is determined, so that preheating is completed and the system enters the heat preservation state before charging begins, ensuring that the system can enter the formal heating stage at any time.

[0059] Based on this, in a preferred embodiment of the present invention, the method of preheating before the start of charging includes: using the lower limit of the allowable injection temperature range as the preheating target temperature.

[0060] The smaller of the current lowest point temperature of the thermal storage system and the molten salt pump body temperature is used as the preheating starting temperature.

[0061] The required temperature rise is determined based on the preheating target temperature and the preheating start temperature, and the preheating time is estimated by combining the heating power of the preheating system.

[0062] The preheating start time is defined as the time offset forward from the charging start time by the preheating duration.

[0063] Once the preheating start time is reached, preheating is initiated until both the equipment structural safety conditions and the pump body temperature conditions are met simultaneously. At this point, preheating is considered complete, and the system enters a heat preservation state.

[0064] It should be noted that the heating power provided by the preheating system already includes the heat loss power during the heating process.

[0065] It should be noted that after preheating is completed, the system enters the heat preservation state. If the temperature drops below the lower limit of the allowable injection temperature range before the start of charging, preheating will be retried.

[0066] Step S3: After the charging start time is reached, the thermal storage system is started to heat up. The electric heating power is determined based on the cold tank status data, the target thermal storage temperature and the charging time. The molten salt pump flow rate is set and adjusted based on the average charging power and power fluctuation.

[0067] Once the charging start time is reached, the thermal storage system enters the formal heating phase. At this point, the required electric heating power needs to be determined based on the initial state of the molten salt in the cold tank, the target thermal storage temperature, and the charging duration. By adjusting the molten salt pump flow rate, the temperature of the molten salt is made to rise evenly during the heating process, while also adapting to fluctuations in the charging power, ensuring that the thermal storage process is efficient and stable.

[0068] To achieve precise heating, the total heat required to heat the molten salt in the cold tank to the target storage temperature must be calculated based on its temperature, mass, and specific heat capacity. Then, the required average electric heating power is calculated by combining this with the charging time. Simultaneously, this power must be compared with the safe power range of the electric heater to ensure that the heating process operates within the equipment's safe operating capacity.

[0069] Based on this, in a preferred embodiment of the present invention, the method for determining the electric heating power includes: obtaining the temperature of the cold tank, the amount of molten salt and the specific heat capacity of the molten salt, and calculating the total heat to be absorbed in combination with the preset target heat storage temperature.

[0070] Based on the total heat to be absorbed and the charging time, the average electric heating power required during the charging period is calculated in reverse.

[0071] The average electric heating power is compared with a pre-stored safe range for electric heating power.

[0072] If the average electric heating power is within the safe range, it is determined as the final electric heating power.

[0073] If the power exceeds the safety range, the upper limit of the safety range will be determined as the final electric heating power.

[0074] It should be noted that the target thermal storage temperature is determined by the downstream power generation or heating efficiency.

[0075] It should be noted that the safe range of electric heating power is determined based on the rated power of the electric heater, the upper limit of the system's heat load, and the grid's regulation capability.

[0076] After determining the electric heating power, it is necessary to further set and dynamically adjust the flow rate of the molten salt pump to achieve coordinated control of heating power and molten salt flow, thereby improving heating efficiency and temperature uniformity.

[0077] The flow rate of the molten salt pump needs to be adjusted to match the changing trend of the charging power: when the charging power increases, the flow rate is increased to avoid local overheating; when the charging power decreases, the flow rate is decreased to ensure that the molten salt absorbs heat sufficiently. Therefore, a power-flow rate matching rule can be established based on historical data or simulation models, and adaptive flow rate adjustment can be achieved through closed-loop control.

[0078] Based on this, in a preferred embodiment of the present invention, the method for setting and adjusting the flow rate of the molten salt pump includes: determining the initial flow rate of the molten salt pump based on the average charging power and in conjunction with a preset matching rule.

[0079] The fluctuation range and trend of charging power are monitored in real time, and the flow rate of the molten salt pump is adjusted accordingly through a closed-loop control algorithm.

[0080] It should be noted that the matching rule is a table or function that establishes the correspondence between charging power and molten salt pump flow rate based on historical data or simulation models.

[0081] It should be noted that when the charging power increases, the flow rate of the molten salt pump is increased to prevent the target thermal storage temperature from exceeding the set range; when the charging power decreases, the flow rate of the molten salt pump is decreased to ensure that the molten salt can be fully heated to close to the target thermal storage temperature.

[0082] During the formal heating process, it is necessary to continuously monitor the changes in heat storage status and charging power. Once the heat tank is close to full or the charging conditions are no longer met, charging should be terminated in time to ensure that the system safely exits the heat storage mode.

[0083] Step S4: During the heating process, monitor the heat storage status and charging power change trend in real time. When the hot tank is close to full storage or the charging conditions are no longer met, terminate the charging and exit the molten salt heat storage.

[0084] During the molten salt heating process, it is necessary to monitor the heat storage status of the hot tank and the changing trend of the external charging power in real time so that charging can be terminated in time when the heat storage is about to be completed or the external power conditions change, so as to avoid overheating, overcharging or equipment idling and ensure the safe and economical operation of the system.

[0085] To achieve intelligent termination of the charging process, specific exit conditions must be set: first, the liquid level in the hot tank reaches a warning value, indicating that the thermal storage is approaching its upper limit; second, the charging power remains below the available power threshold, indicating that the external surplus power is no longer sufficient to meet the continuous heating demand. Heating should be terminated and the thermal storage mode should be exited when either condition is triggered.

[0086] Based on this, in a preferred embodiment of the present invention, see [reference]. Figure 3 As shown, the specific process of step S4 includes: real-time monitoring of the heat storage status and the changing trend of charging power during the heating process.

[0087] When the liquid level in the hot tank reaches the set warning value, it is determined that the hot tank is close to full storage.

[0088] When the charging power remains below the available power threshold, it is determined that the charging conditions are no longer met.

[0089] If either the hot tank is close to full or the charging conditions are no longer met, charging will be terminated and the molten salt thermal storage mode will be exited.

[0090] As an example, the warning value for the hot tank level is 90% of the volume.

[0091] In this embodiment, the present invention determines the electric heating power based on the cold tank status, the target thermal storage temperature, and the charging time, and adjusts the molten salt pump flow rate in real time according to the fluctuation of the charging power. This achieves dynamic matching between the heating power and the molten salt flow rate, ensuring that the molten salt is stably and uniformly heated to the target temperature, avoiding overheating or underheating, and maximizing the utilization of the thermal storage capacity. This solves the problem of insufficient closed-loop control in the heating process of existing technologies, which may lead to temperature fluctuations or insufficient utilization of thermal storage capacity.

[0092] In summary, this invention generates a surplus power curve based on the predicted power at the power generation and consumption ends, determines charging conditions based on the surplus power and stability, and if the conditions are met, predicts the charging start time, duration, and average power to trigger thermal storage; monitors key temperature parameters of the system, and determines and executes preheating based on the allowable injection temperature range and uniformity requirements; after reaching the charging start time, determines the electric heating power based on the cold tank status, target thermal storage temperature, and charging duration, and adjusts the molten salt pump flow rate according to the average charging power and fluctuations; monitors the thermal storage status and charging power in real time during the heating process, and terminates charging when the hot tank is nearly full or the charging conditions are not met.

[0093] This invention enables intelligent response and safe and efficient utilization of surplus power from the power grid. By safely preheating before charging and dynamically optimizing the heating process, it improves the absorption capacity, operational safety, and overall efficiency of the thermal storage system.

[0094] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0095] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0096] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0097] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0098] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0099] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0100] Finally, 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 within the protection scope of the present invention.

Claims

1. A method for controlling electrically heated molten salt for molten salt thermal storage, characterized in that, Includes the following steps: S1. Based on the predicted power data of the power generation end and the power consumption end, generate the surplus power curve. Based on the surplus power and the stability of the surplus power, determine whether the charging conditions are met. If they are met, predict the start time, duration and average power of charging, trigger molten salt thermal storage and enter S2. Otherwise, continue to monitor the surplus power. S2. Monitor the current key temperature parameters of the thermal storage system, and determine whether preheating is required based on the allowable injection temperature range and temperature uniformity requirements. If preheating is required, preheat before the start of charging and proceed to S3 after completion. If not, execute S3 directly. S3. After the charging start time is reached, the thermal storage system is started to heat up. The electric heating power is determined based on the cold tank status data, the target thermal storage temperature and the charging time. The molten salt pump flow rate is set and adjusted based on the average charging power and power fluctuation. S4. During the heating process, monitor the heat storage status and charging power change trend in real time. When the hot tank is close to full storage or the charging conditions are no longer met, terminate the charging and exit the molten salt heat storage.

2. The method for controlling electrically heated molten salt for molten salt thermal storage according to claim 1, characterized in that: The method for generating the surplus power curve includes: Obtain the predicted power time series for the power generation and consumption ends, and perform time series alignment; Starting from the first time point of the time series, obtain the power generation power and power consumption power corresponding to that time point, subtract the power consumption power from the power generation power, and calculate the surplus power corresponding to the first time point. By sequentially traversing each time point in the time series, the surplus power corresponding to each time point is calculated to form a surplus power sequence. Based on the surplus power sequence, a surplus power curve is generated with time as the horizontal axis and surplus power as the vertical axis.

3. The method for controlling electrically heated molten salt for molten salt thermal storage according to claim 1, characterized in that: The method for determining whether the charging conditions are met includes: The straight line with zero surplus power is used as the baseline; Identify the curve segment in the surplus power curve that is above the baseline and record it as the target curve segment; The surplus power corresponding to each target curve segment is calculated based on the area enclosed by the target curve segment and the baseline, and it is determined whether the surplus power corresponding to each target curve segment is stable. Count the number of target curve segments where the surplus electricity exceeds a set threshold and the surplus electricity is stable. If there is at least one target curve segment that meets the above conditions, then the charging conditions are deemed to be met; otherwise, the charging conditions are deemed not to be met.

4. The method for controlling electrically heated molten salt for molten salt thermal storage according to claim 3, characterized in that: The method for determining whether the surplus power corresponding to the target curve segment is stable includes: Obtain the surplus power corresponding to each point on the target curve segment; Determine whether the following conditions are met simultaneously: (1) The surplus power at each point is greater than the preset available power threshold; (2) The change in surplus power between adjacent data points is less than the set fluctuation threshold; If both conditions are met, the surplus power corresponding to the target curve segment is determined to be stable; otherwise, it is determined to be unstable.

5. The method for controlling electrically heated molten salt for molten salt thermal storage according to claim 3, characterized in that: The method for predicting the start time, duration, and average power of charging includes: If there is only one target curve segment that meets the conditions, the time point corresponding to the starting point of the target curve segment is taken as the charging start time, the interval between the time points corresponding to the starting point and the ending point is taken as the charging duration, and the average value of the surplus power corresponding to each point on the target curve segment is taken as the average charging power. If there are multiple target curve segments that meet the conditions, the time point corresponding to the starting point of the target curve segment with the earliest starting point is taken as the charging start time, the cumulative value of the charging time corresponding to each target curve segment is taken as the final charging time, and the average value of the charging average power corresponding to each target curve segment is taken as the final charging average power.

6. The method for controlling electrically heated molten salt for molten salt thermal storage according to claim 1, characterized in that: The method for determining whether preheating is required includes: Monitor the current key temperature parameters of the thermal storage system, including the lowest point temperature of the equipment and the temperature difference of the equipment, the temperature of the molten salt pump body and the temperature difference between the top and bottom of the pump body; The allowable injection temperature range is determined based on the freezing point of the molten salt and the preset safety margin. Based on the set temperature uniformity requirements, the allowable ranges for the temperature difference of the equipment and the temperature difference between the top and bottom of the molten salt pump body are determined respectively. To determine whether the equipment structure safety conditions are met, the conditions are: the temperature at the lowest point of the equipment is within the allowable injection temperature range, and the temperature difference of the equipment is within the corresponding allowable range. To determine whether the pump body temperature condition is met, the condition is that the temperature of the molten salt pump body is within the allowable injection temperature range, and the temperature difference between the upper and lower parts of the pump body is within the corresponding allowable range. If either the safety conditions of the equipment structure or the temperature conditions of the pump body are not met, it is determined that preheating is required; otherwise, it is determined that preheating is not required.

7. The method for controlling electrically heated molten salt for molten salt thermal storage according to claim 6, characterized in that: The method of preheating before the start of charging includes: The lower limit of the allowable injection temperature range is taken as the preheating target temperature; The smaller of the current lowest point temperature of the thermal storage system equipment and the molten salt pump body temperature is used as the preheating starting temperature. The required temperature rise is determined based on the preheating target temperature and the preheating start temperature, and the preheating time is estimated based on the heating power of the preheating system. The preheating start time is defined as the time when the charging start time is shifted forward by the preheating duration. Once the preheating start time is reached, preheating is initiated until both the equipment structural safety conditions and the pump body temperature conditions are met simultaneously. At this point, preheating is considered complete, and the system enters a heat preservation state.

8. The method for controlling electrically heated molten salt for molten salt thermal storage according to claim 1, characterized in that: The method for determining the electric heating power includes: Obtain the cold tank temperature, molten salt quantity, and specific heat capacity of the molten salt; and calculate the total heat to be absorbed based on the preset target heat storage temperature. Based on the total heat to be absorbed and the charging time, the average electric heating power required during the charging period is calculated in reverse. The average electric heating power is compared with the pre-stored safe range of electric heating power; If the average electric heating power is within the safe range, then it is determined as the final electric heating power; If the power exceeds the safety range, the upper limit of the safety range will be determined as the final electric heating power.

9. The method for controlling electrically heated molten salt for molten salt thermal storage according to claim 1, characterized in that: The method for setting and adjusting the flow rate of the molten salt pump includes: Based on the average charging power and in conjunction with preset matching rules, the initial flow rate of the molten salt pump is determined; The fluctuation range and trend of charging power are monitored in real time, and the flow rate of the molten salt pump is adjusted accordingly through a closed-loop control algorithm.

10. The method for controlling electrically heated molten salt for molten salt thermal storage according to claim 4, characterized in that: The specific process of step S4 includes: The heat storage status and charging power are monitored in real time during the heating process; When the liquid level in the hot tank reaches the set warning value, it is determined that the hot tank is close to full. When the charging power remains below the available power threshold, it is determined that the charging conditions are no longer met. If either the hot tank is close to full or the charging conditions are no longer met, charging will be terminated and the molten salt thermal storage mode will be exited.

Images