An outlet temperature stabilization control method and system for an electrically heated molten salt system

Abstract

The present application belongs to the field of new energy and energy saving technology, and particularly relates to a kind of electric heating molten salt system outlet temperature stable control method and system. Including: collecting wind and light fluctuation data, combining molten salt system thermal inertia introduces frequency band fluctuation weight coefficient, calculates wind and light fluctuation real-time power regulation demand;Adjustment demand is adaptively distributed to electric heating array, and the real-time target heating power of each electric heater is obtained;Based on target heating power, introduce thermal inertia lag compensation term, deduce thermal inertia compensation molten salt target volume flow;Introduce molten salt viscosity-temperature correction coefficient to correct target volume flow, obtain molten salt flow deviation value with viscosity correction;Based on incremental PID control algorithm, convert flow deviation value into frequency regulation instruction of molten salt pump. The present application realizes the adaptive response to wind and light fluctuation and the precise stable control of molten salt outlet temperature.

Description

Technical Field

[0001] This invention belongs to the field of new energy and energy-saving technology, specifically relating to a method and system for stabilizing the outlet temperature of an electrically heated molten salt system. Background Technology

[0002] Electric heating molten salt thermal energy storage technology, with its advantages of high thermal density, wide operating temperature range, and controllable cost, has become one of the core technologies for renewable energy consumption, improving the flexibility of thermal power units, and industrial clean heating. In scenarios with a high proportion of wind and solar power integration, the electric heating molten salt system can adjust the electric heating power to absorb fluctuations in wind and solar output, converting curtailed wind and solar power into thermal energy for storage. Then, through the heat exchange electric heating molten salt system, it can provide industrial users with stable steam or hot water, achieving on-site consumption and efficient utilization of renewable energy.

[0003] Existing electrically heated molten salt systems generally face two major technical contradictions in responding to fluctuations in wind and solar power output: First, to achieve full absorption of wind and solar power, the electric heating power needs to change rapidly in real time with the output. However, molten salt itself has significant thermal inertia, and frequent fluctuations in heating power can easily lead to large fluctuations in the molten salt outlet temperature, failing to meet the stringent requirements of industrial users for the stability of thermal parameters, and even causing safety risks such as local overheating leading to molten salt decomposition and equipment corrosion failure. Second, to ensure the stability of the molten salt outlet temperature, existing technologies often limit the adjustment rate and range of electric heating power, making it impossible to fully respond to fluctuations in wind and solar power output, significantly reducing the renewable energy absorption rate, and violating the core objective of the construction of electrically heated molten salt systems.

[0004] Specifically, existing related technologies have the following clear drawbacks: 1. Existing power demand calculation methods often directly use the static difference between wind and solar power output and base load as the adjustment target, without distinguishing the frequency characteristics of wind and solar fluctuations. High-frequency, short-cycle power fluctuations will cause the electric heating molten salt system to be frequently adjusted, exacerbating the fluctuation of molten salt temperature and increasing the mechanical and electrical losses of the equipment. 2. The power distribution of existing electric heating arrays is mostly based on the uniform distribution according to the heating area, without considering the differences in the real-time operating temperature and electrothermal conversion efficiency of individual electric heaters. This can easily lead to local overheating of electric heaters with small temperature margins, causing safety problems such as molten salt decomposition and equipment corrosion. At the same time, it reduces the overall electrothermal conversion efficiency of the electric heating molten salt system. 3. Existing methods for matching molten salt flow rate and heating power are mostly based on the steady-state convective heat transfer energy conservation formula, without considering the temperature response lag caused by the thermal inertia of the electrically heated molten salt system. Under dynamic conditions where the heating power changes rapidly, overshoot or undershoot of the molten salt outlet temperature is likely to occur, making it impossible to achieve precise temperature control. 4. The flow control of existing molten salt pumps mostly adopts conventional PID control algorithms, which do not take into account the significant characteristics of the dynamic viscosity of molten salt changing with temperature. Changes in the inlet temperature of molten salt will cause deviations in the actual flow rate at the same pump frequency, further amplifying the fluctuations in the outlet temperature of molten salt, resulting in poor control robustness. 5. Existing technologies mostly optimize single links and have not formed a full-link linkage control method from wind and solar power fluctuation power quantification, power allocation, flow matching to closed-loop control at the execution end. There is a lack of data linkage between links, and it is impossible to achieve coordinated optimization of absorption rate and temperature stability. Summary of the Invention

[0005] This invention provides a method and system for stabilizing the outlet temperature of an electrically heated molten salt system, in order to solve the technical problems existing in the prior art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for stabilizing the outlet temperature of an electrically heated molten salt system includes the following steps: Real-time wind and solar fluctuation data are collected. Combined with the thermal inertia characteristics of the electrically heated molten salt system, frequency band fluctuation weight coefficients are introduced to assign differentiated response weights to the wind and solar fluctuation data and calculate the real-time power adjustment demand for wind and solar fluctuations. Adaptive allocation of electric heating array to the real-time power adjustment demand of wind and solar fluctuations, and obtain the real-time target heating power of each electric heater in the electric heating array; Based on the real-time target heating power of each electric heater in the electric heating array, a thermal inertia hysteresis compensation term based on the rate of change of heating power is introduced to derive the target volumetric flow rate of molten salt with thermal inertia compensation. A molten salt viscosity-temperature correction coefficient is introduced to correct the target volumetric flow rate of the molten salt with thermal inertia compensation, thereby obtaining the molten salt flow rate deviation value with viscosity correction. Based on the incremental PID control algorithm and combined with the characteristics of molten salt pump flow control, the molten salt flow deviation value with viscosity correction is converted into a frequency adjustment command for the molten salt pump.

[0007] The real-time acquired wind and solar power fluctuation data, combined with the thermal inertia characteristics of the electrically heated molten salt system, introduces frequency band fluctuation weighting coefficients to assign differentiated response weights to the wind and solar power fluctuation data, and calculates the real-time power adjustment demand for wind and solar power fluctuations. Specifically, based on the thermal inertia characteristics of the electrically heated molten salt system, frequency band fluctuation weighting coefficients are introduced to reduce the response weight of short-period high-frequency fluctuations in the wind and solar power fluctuation data, while providing a full response to long-period low-frequency fluctuations, thus deriving the real-time power adjustment demand for wind and solar power fluctuations. The formula for calculating the real-time power adjustment demand for wind and solar power fluctuations is as follows:

[0008] in, Let t be the real-time power output of the wind farm. Let t be the real-time output value of the photovoltaic power station. This is the basic operating power for an electrically heated molten salt system. The weighting coefficients are for short-cycle, high-frequency fluctuations on the 1-minute timeframe. This represents the absolute value of the maximum fluctuation in the total power output sequence of wind and solar power over the past minute within the statistical period. This represents the absolute value of the maximum fluctuation in the total power output sequence of wind and solar power over the past 10 minutes within the statistical period. This refers to the rated total heating power of the electrically heated molten salt system.

[0009] The adaptive allocation of the real-time power adjustment demand for wind and solar power fluctuations to the electric heating array to obtain the real-time target heating power of each electric heater in the electric heating array is specifically as follows: During the heat flow distribution process of the electric heating molten salt system, the real-time electrothermal conversion efficiency and real-time temperature margin of a single electric heater are used as correction terms to adaptively assign weights to each electric heater in the electric heating array. Based on the weight allocation of each electric heater, the real-time power adjustment demand for wind and solar power fluctuations is allocated to each electric heater in the electric heating array to obtain the real-time target heating power of each electric heater in the electric heating array. The calculation formula for the real-time target heating power of each electric heater in the electric heating array is as follows:

[0010] in, Let be the real-time target heating power of the i-th electric heater in the electric heating array. To meet the real-time power adjustment requirements for wind and solar power fluctuations. Let i be the effective heating area of ​​the i-th electric heater. Let be the real-time electrothermal conversion efficiency of the i-th electric heater. Let i be the real-time temperature margin of the i-th electric heater. This represents the total number of electric heaters in the electric heating array. This is the sequence number variable for the electric heaters in the electric heating array. Let n be the effective heating area of ​​the nth electric heater in the electric heating array. Let be the real-time electrothermal conversion efficiency of the nth electric heater in the electric heating array.

[0011] The step of using the real-time electrothermal conversion efficiency and real-time temperature margin of a single electric heater as correction terms specifically involves: real-time acquisition of the input power of the electric heater, the inlet and outlet temperatures of the molten salt, and the molten salt flow rate; calculation of the real-time electrothermal conversion efficiency of a single electric heater; and calculation of the real-time temperature margin of a single electric heater using the maximum allowable operating temperature and the real-time outlet temperature. The formula for calculating the real-time electrothermal conversion efficiency of a single electric heater is as follows:

[0012] in, Let be the real-time electrothermal conversion efficiency of the i-th electric heater. The specific heat capacity of molten salt at constant pressure. The density of molten salt, The real-time molten salt flow rate of the i-th electric heater branch. Let be the real-time outlet temperature of the i-th electric heater. Let be the real-time inlet temperature of the i-th electric heater. Let be the real-time input electrical power of the i-th electric heater.

[0013] The formula for calculating the real-time temperature margin of a single electric heater is as follows:

[0014] in, Let i be the real-time temperature margin of the i-th electric heater. This is the maximum permissible operating temperature of the molten salt.

[0015] The method involves deriving the target volumetric flow rate of molten salt based on the real-time target heating power of each electric heater in the electric heating array, using a thermal inertia hysteresis compensation term based on the rate of change of heating power. Specifically, based on the classical energy conservation formula for convective heat transfer, a thermal inertia hysteresis compensation term based on the rate of change of heating power is introduced. According to the real-time target heating power of each electric heater in the electric heating array, the thermal inertia hysteresis compensation term is used to offset the temperature response hysteresis caused by the thermal inertia of the molten salt, thereby calculating the corresponding thermal inertia-compensated target volumetric flow rate of the molten salt. The formula for calculating the target volumetric flow rate of the molten salt with thermal inertia compensation is as follows:

[0016] in, Let be the real-time target heating power of the i-th electric heater in the electric heating array. The thermal inertia time constant of the electrically heated molten salt system. Let be the real-time target heating power change rate of the i-th electric heater. Set the outlet temperature for the molten salt. Let be the real-time temperature of the molten salt inlet of the i-th electric heater. This is a thermal inertia hysteresis compensation term. The specific heat capacity of molten salt at constant pressure. ρ is the density of the molten salt.

[0017] A molten salt viscosity-temperature correction coefficient is introduced to correct the target volumetric flow rate of the molten salt with thermal inertia compensation. This offsets the impact of viscosity changes caused by variations in the molten salt inlet temperature on the actual flow rate, making the flow deviation calculation more closely reflect the actual operating characteristics of the electrically heated molten salt system, thus obtaining a molten salt flow deviation value with viscosity correction. The formula for calculating the molten salt flow deviation with viscosity correction is as follows:

[0018] in, For the system control cycle of the electrically heated molten salt system, The dynamic viscosity of the molten salt at its rated operating temperature. For the first The control cycle of an electrically heated molten salt system is the actual volumetric flow rate of the molten salt in the i-th electric heater. For the first The real-time temperature of the molten salt inlet of the i-th electric heater in the control cycle of an electrically heated molten salt system. The dynamic viscosity of molten salt. The real-time temperature of the molten salt inlet is At that time, the dynamic viscosity of molten salt, This is the viscosity-temperature correction factor for molten salt.

[0019] The introduction of a molten salt viscosity-temperature correction coefficient to correct the target volumetric flow rate of the molten salt with thermal inertia compensation is specifically as follows: when the real-time temperature of the molten salt inlet of the i-th electric heater... When the temperature is below the rated temperature, the molten salt viscosity-temperature correction factor is greater than 1, and the target flow rate setpoint is increased synchronously to offset the flow loss caused by the increase in viscosity; when the real-time temperature of the molten salt inlet of the i-th electric heater... When the temperature is equal to the rated temperature, the viscosity-temperature correction factor of the molten salt is equal to 1, and no correction is made.

[0020] The incremental PID control algorithm, combined with the characteristics of molten salt pump flow control, converts the viscosity-corrected molten salt flow deviation value into a frequency adjustment command for the molten salt pump. Specifically, based on the characteristics of molten salt pump flow control, the incremental PID control algorithm is discretized and adapted, clarifying the dimensional matching relationship between the control period and each coefficient. Incremental output is used to convert the viscosity-corrected molten salt flow deviation value into a frequency adjustment command for the molten salt pump. The frequency adjustment command is the adjustment value of the molten salt pump frequency, and the calculation formula for the molten salt pump frequency adjustment command is as follows:

[0021] in, For the system control cycle of the electrically heated molten salt system, For the first Within each system control cycle, the output frequency adjustment value of the molten salt pump corresponding to the i-th electric heater in the branch is... For the first Within one system control cycle, the output frequency adjustment value of the molten salt pump in the branch corresponding to the i-th electric heater. This refers to the proportional coefficient in the incremental PID control algorithm. The integral coefficients of the PID control algorithm are... These are the differential coefficients of the incremental PID control algorithm. The control cycle of the incremental PID control algorithm. For the first The viscosity-corrected molten salt flow rate deviation value for each system control cycle. For the first -1 system control cycle of molten salt flow deviation with viscosity correction. For the first -2 system control cycles of molten salt flow deviation with viscosity correction.

[0022] A stable control system for the outlet temperature of an electrically heated molten salt system includes a power demand calculation module, a power allocation module, a flow matching module, a viscosity correction module, and a frequency control module. The power demand calculation module is used to collect wind and solar fluctuation data in real time. Combining the thermal inertia characteristics of the electric heating molten salt system, it introduces frequency band fluctuation weight coefficients to assign differentiated response weights to the wind and solar fluctuation data and calculate the real-time power adjustment demand of wind and solar fluctuations. The power allocation module is used to adaptively allocate the power demand of the electric heating array according to the real-time power adjustment requirements of wind and solar fluctuations, and obtain the real-time target heating power of each electric heater in the electric heating array. The flow matching module is used to derive the thermal inertia-compensated target volumetric flow rate of molten salt by introducing a thermal inertia hysteresis compensation term based on the real-time target heating power of each electric heater in the electric heating array. The viscosity correction module is used to introduce a molten salt viscosity-temperature correction coefficient to correct the target volumetric flow rate of the molten salt with thermal inertia compensation, thereby obtaining the molten salt flow rate deviation value with viscosity correction. The frequency control module is used to convert the molten salt flow deviation value with viscosity correction into the frequency adjustment command of the molten salt pump based on the incremental PID control algorithm and combined with the characteristics of molten salt pump flow control.

[0023] Compared with the prior art, the present invention has the following beneficial effects: This invention effectively solves the core contradiction in existing technologies—the inability to simultaneously achieve renewable energy consumption and temperature stability—through a collaborative optimization design across the entire supply chain, thus realizing the safe and efficient operation of the electrically heated molten salt system. In the power demand calculation stage, this invention employs differentiated weight adjustments across frequency bands, adopting different response strategies for wind and solar power fluctuations of different cycles. It appropriately reduces the response level to short-cycle high-frequency fluctuations while maintaining a full response to long-cycle low-frequency fluctuations. This filters out interference from small-amplitude high-frequency fluctuations, preventing frequent system adjustments and mitigating the amplitude of molten salt temperature fluctuations. Simultaneously, it reduces mechanical and electrical losses in the equipment, ensures a sufficient response to effective fluctuations, and maintains the system's renewable energy consumption capacity. In the power distribution stage of the electric heating array, this invention abandons the traditional method of uniform distribution based on heating area. Instead, it adaptively adjusts the distribution weight according to the actual operating status of each electric heater and its respective electrothermal conversion efficiency and temperature margin. This allows electric heaters with higher operating efficiency and more sufficient temperature margin to bear more regulatory load, avoiding local overheating caused by overload in some electric heaters, thus preventing the safety risks of molten salt decomposition and equipment corrosion at the source. It also fully taps the operating potential of each electric heater, improving the overall electrothermal conversion efficiency of the entire system. In the molten salt flow matching stage, this invention no longer relies on the traditional steady-state convective heat transfer energy conservation formula. Instead, it introduces a thermal inertia lag compensation mechanism for changes in heating power. This mechanism can predict the temperature response delay caused by power changes in advance and dynamically adjust the target flow rate of the molten salt. Under dynamic operating conditions with rapid changes in heating power, it avoids temperature overshoot or undershoot and achieves precise control of the molten salt outlet temperature. In the flow control stage of the molten salt pump, this invention introduces a viscosity-temperature correction mechanism to address the significant temperature-dependent variation of molten salt dynamic viscosity. This mechanism can adjust the target flow rate setting in real time based on changes in inlet temperature. When the inlet temperature is too low, causing an increase in molten salt viscosity, the flow rate setting is automatically adjusted to offset the actual flow deviation caused by viscosity changes. This significantly improves the accuracy of flow control, effectively suppresses the amplification effect of temperature fluctuations, and significantly enhances the robustness of the control algorithm. The entire control method establishes a complete link from the quantification of fluctuating wind and solar power output to closed-loop control at the execution end. Data from each link can be linked and coordinated, moving beyond local optimization of a single link. This truly achieves synergistic optimization of new energy absorption capacity and outlet temperature stability, enabling the electrically heated molten salt system to fully respond to fluctuations in wind and solar power output, maximize the absorption of new energy electricity, and provide stable and reliable thermal parameters for industrial users, comprehensively ensuring the safe and efficient operation of the system. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a method for stabilizing the outlet temperature of an electrically heated molten salt system according to an embodiment of the present invention. Detailed Implementation

[0025] To further understand the content of this invention, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments are merely illustrative and not limiting of the invention.

[0026] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0027] Example 1 This embodiment proposes a method for stabilizing the outlet temperature of an electrically heated molten salt system, combined with... Figure 1 As shown, the specific steps include: First, wind and solar power fluctuation data from wind farms and photovoltaic power plants are acquired. Unlike directly calculating demand based on the power balance equation, this embodiment fully considers the thermal inertia characteristics inherent in the electrically heated molten salt system. Due to the large heat capacity of the electrically heated molten salt system, it has a natural smoothing effect on short-term power fluctuations. Therefore, this step introduces frequency band fluctuation weighting coefficients to assign differentiated response weights to wind and solar power fluctuations of different periods. Specifically: for short-period high-frequency fluctuations, their response weights are reduced, and the thermal inertia of the molten salt itself is used for smoothing, avoiding frequent adjustments of the electrically heated molten salt system; for long-period low-frequency fluctuations, a full response is provided to ensure the absorption rate of new energy. This achieves precise quantification of power regulation demand from the source and outputs real-time power regulation demand for wind and solar power fluctuations that can balance the stability of the electrically heated molten salt system and the absorption rate.

[0028] After obtaining the total power regulation demand, it needs to be allocated to specific heating equipment. However, traditional allocation methods often distribute the power evenly according to the heating area, ignoring the differences in the operating status of individual heating equipment. Therefore, in this embodiment, the real-time power regulation demand of wind and solar fluctuations is adaptively allocated to the electric heating array. The total power demand is reasonably allocated to each electric heater in the electric heating array, and the real-time target heating power of each electric heater in the electric heating array is obtained, avoiding the risk of local overheating or equipment failure.

[0029] In flow matching for outlet temperature control of an electrically heated molten salt system, when the heating power changes rapidly, the change in outlet temperature often lags behind the change in power due to the thermal inertia of the molten salt and heating pipes. Directly using the steady-state energy conservation formula to calculate the flow rate can lead to temperature overshoot or undershoot. Therefore, this embodiment introduces a thermal inertia lag compensation term based on the rate of change of heating power when deriving the target volumetric flow rate of the molten salt. This term senses the speed and direction of power change and derives the thermal inertia-compensated target volumetric flow rate of the molten salt for the real-time target heating power of each electric heater in the electric heating array.

[0030] Molten salt, as a fluid, exhibits a dynamic viscosity that changes significantly with temperature. When the molten salt inlet temperature fluctuates, even with a constant pump frequency, the actual flow rate will deviate due to changes in pipeline resistance caused by viscosity variations. Directly using the theoretically calculated target flow rate for control introduces a systemic error into the electrically heated molten salt system. Therefore, this embodiment introduces a molten salt viscosity-temperature correction coefficient to correct the thermal inertia-compensated target volumetric flow rate of the molten salt, obtaining a viscosity-corrected molten salt flow rate deviation value. This correction coefficient allows for dynamic adjustment of the target flow rate setpoint based on inlet temperature changes, offsetting flow loss or gain caused by viscosity variations. This makes the calculated flow rate deviation value more closely reflect the actual operating characteristics of the electrically heated molten salt system, thereby improving control robustness.

[0031] An incremental PID (Proportional-Integral-Derivative) control algorithm is employed to convert the flow deviation into a frequency adjustment command for the molten salt pump inverter. This embodiment, considering the characteristics of molten salt pump flow control, discretizes and adapts the incremental PID control algorithm, clarifying the dimensional matching relationship between the control cycle and each coefficient. Ultimately, by adjusting the frequency of the molten salt pump, the actual flow rate of the molten salt is precisely controlled, bringing it close to the target flow rate, thereby achieving precise and stable control of the molten salt outlet temperature.

[0032] Through the synergistic effect of the above steps, this embodiment constructs a complete method for stabilizing the outlet temperature of an electrically heated molten salt system. From the source quantification of power input, adaptive allocation of array power, thermal inertia compensation and viscosity correction of flow rate, to the final frequency closed-loop control, the method is progressively improved and effectively solves the problem of unstable temperature control of the electrically heated molten salt system under wind and solar fluctuations.

[0033] Example 2 Based on the method for stabilizing the outlet temperature of an electrically heated molten salt system proposed in Example 1, this example provides a detailed description, and the specific implementation method is as follows: Step 1: Real-time acquisition of wind and solar power fluctuation data. Combining this with the thermal inertia characteristics of the electrically heated molten salt system, a frequency band fluctuation weighting coefficient is introduced. The response weight for short-period high-frequency fluctuations in the wind and solar power fluctuation data is reduced, while long-period low-frequency fluctuations receive a full response. This allows for the derivation of the real-time power adjustment demand for wind and solar power fluctuations. Specifically, the electrically heated molten salt system has a large heat capacity, and its temperature changes exhibit significant hysteresis. This thermal inertia characteristic gives the electrically heated molten salt system a natural ability to smooth out short-term power fluctuations. Based on this, this embodiment divides wind and solar power fluctuation data into different frequency bands and assigns differentiated response weights. For short-period high-frequency fluctuations, such as fluctuations with a period of less than 1 minute, the electrically heated molten salt system reduces its response weight, utilizing the thermal inertia of the molten salt itself to smooth out the fluctuations and avoid temperature oscillations caused by frequent adjustments by the electrically heated molten salt system. For long-period low-frequency fluctuations, such as fluctuations with a period of about 10 minutes, the electrically heated molten salt system responds fully to ensure the full absorption of renewable energy. The formula for calculating the real-time power adjustment demand for wind and solar power fluctuations is as follows:

[0034] in, The real-time power output of the wind farm at time t is expressed in kW. It is acquired in real time through the SCADA electric heating molten salt system of the wind farm, and the sampling period is consistent with the system control period. The real-time output value of the photovoltaic power station at time t is expressed in kW. It is acquired in real time through the SCADA electric heating molten salt system of the photovoltaic power station, and the sampling period is consistent with the system control period. The basic operating power of the electric heating molten salt system, in kW, is the minimum heating power set to ensure the minimum operational stability of the electric heating molten salt system. It is determined based on the minimum industrial heat load requirements and the design parameters of the electric heating molten salt system. It is a dimensionless weighting coefficient for short-cycle high-frequency fluctuations on the 1-minute level. It is determined based on the thermal inertia time constant of the electrically heated molten salt system and is used to reduce the response weight of high-frequency fluctuations to avoid frequent adjustments of the electrically heated molten salt system. It is a dimensionless weighting coefficient for long-cycle, low-frequency fluctuations at the 10-minute level. It is determined according to the policy requirements for new energy consumption and the project design objectives, and is used to ensure the full consumption of long-cycle, continuous fluctuations. The maximum absolute value of the total wind and solar power output sequence in the past minute within the statistical period, in kW, is obtained by performing a first-order difference calculation on the total wind and solar power output time series in the past minute and taking the maximum absolute value of the difference result. The maximum absolute value of the total wind and solar power output sequence over the past 10 minutes within the statistical period, expressed in kW, is obtained by performing a first-order difference calculation on the time series of total wind and solar power output over the past 10 minutes and taking the maximum absolute value of the difference result. 1 represents the rated total heating power of the electric heating molten salt system, in kW; 2 represents the rated parameters of the equipment determined during the design phase of the electric heating molten salt system, which are fixed values.

[0035] The embodiment introduces a frequency band fluctuation weight coefficient to assign differentiated response weights to wind and solar fluctuations of different periods, quantifies the target total power that the electric heating molten salt system needs to respond to due to wind and solar fluctuations, and solves the core contradiction in the existing technology that "full response to fluctuations will lead to temperature runaway, and stable temperature will not be able to fully absorb the power." Through frequency band weight allocation, it takes into account both the renewable energy absorption rate and the stability of the electric heating molten salt system operation.

[0036] Step Two: In the heat flow distribution process of the electric heating molten salt system, the system uses the real-time electrothermal conversion efficiency and real-time temperature margin of a single electric heater as correction terms to adaptively assign weights to each electric heater in the electric heating array. Based on these weights, the real-time power adjustment demand due to wind and solar power fluctuations is allocated to each heater in the array, obtaining the real-time target heating power for each heater. This ensures that heaters with higher electrothermal conversion efficiency and larger temperature safety margins receive more heating power, guaranteeing that the total heating power accurately responds to the real-time power adjustment demand due to wind and solar power fluctuations obtained in Step One. At the same time, it avoids the safety risks of local overheating from the root cause, improving the overall operating efficiency and safety of the system. The real-time target heating power calculation formula for each electric heater in the electric heating array is as follows:

[0037] in, The real-time target heating power of the i-th electric heater in the electric heating array is expressed in kW. The effective heating area of ​​the i-th electric heater is given in units of . , which are the design parameters of the electric heater at the time of manufacture, and are fixed values; Let be the real-time electrothermal conversion efficiency of the i-th electric heater, which is dimensionless and is calculated by real-time acquisition of the electric heater input power, molten salt inlet and outlet temperatures, and molten salt flow rate. The real-time temperature margin of the i-th electric heater is expressed in °C and is calculated using the maximum allowable operating temperature of the electric heater and the real-time outlet temperature. is the total number of electric heaters in the electric heating array, dimensionless; is the number of devices determined during the system design phase, a fixed value. The dimensionless variable representing the index of the electric heaters in the electric heating array is used to iterate through all the electric heaters in the array and calculate the sum of the total assigned weights; where, The total weight assigned to all electric heaters in the electric heating array is dimensionless; it is calculated by summing the parameters of each electric heater in the array, where... Let n be the effective heating area of ​​the nth electric heater in the electric heating array. This represents the real-time electrothermal conversion efficiency of the nth electric heater in the electric heating array. This is achieved by adjusting the real-time power demand based on wind and solar power fluctuations. The power is rationally and adaptively distributed to each electric heater in the array, ensuring a precise response of the total heating power to wind and solar power fluctuations, optimizing load allocation, avoiding the risk of local overheating, and improving the system's operational safety and electrothermal conversion efficiency. In actual operation, due to factors such as the aging degree of electric heaters, scaling conditions, and differences in branch flow rates, the electrothermal conversion efficiency of each electric heater often varies. If power is forcibly and evenly distributed, inefficient electric heaters will consume more power than they generate, while efficient electric heaters will be underutilized. More seriously, if an electric heater is already close to the overheating threshold, continuing to allocate high power will cause a shutdown failure. This embodiment introduces real-time electrothermal conversion efficiency and real-time temperature margin as correction terms to dynamically adjust the power weight of each electric heater. This ensures a precise response of the total heating power to wind and solar power fluctuations, avoids the risk of local overheating at its source, and improves the overall operational efficiency and safety of the system.

[0038] The real-time electrothermal conversion efficiency of a single electric heater is calculated by collecting real-time data on the input power, inlet and outlet temperatures of the molten salt, and the molten salt flow rate. The real-time temperature margin of the single electric heater is then calculated using its maximum allowable operating temperature and real-time outlet temperature. The formula for calculating the real-time electrothermal conversion efficiency of a single electric heater is as follows:

[0039] in, Let be the real-time electrothermal conversion efficiency of the i-th electric heater. The specific heat capacity of molten salt at constant pressure. The density of molten salt, Let i be the real-time molten salt flow rate of the i-th electric heater. Let be the real-time outlet temperature of the i-th electric heater. Let be the real-time inlet temperature of the i-th electric heater. Let be the real-time input electrical power of the i-th electric heater. The real-time temperature margin calculation formula for a single electric heater is as follows:

[0040] in, This represents the real-time temperature margin of the i-th electric heater, in °C. Where is the maximum allowable operating temperature of the molten salt, and represents the physical properties of the molten salt material. Data is collected in real time via a thermocouple at the outlet of the electric heater.

[0041] Step 3: Based on the classical energy conservation formula for convective heat transfer, this embodiment introduces a thermal inertia hysteresis compensation term based on the rate of change of heating power. When the heating power increases, the molten salt flow rate is increased synchronously to avoid temperature overshoot; when the heating power decreases, the molten salt flow rate is decreased synchronously to avoid temperature undershoot; when the heating power is stable, the compensation term is 1, reverting to the steady-state energy conservation formula. Based on the real-time target heating power of each electric heater in the electric heating array, the thermal inertia hysteresis compensation term is used to offset the temperature response hysteresis caused by the thermal inertia of the molten salt, and the corresponding thermal inertia-compensated target volumetric flow rate of the molten salt is calculated. This achieves the control effect of "synchronous changes in power and flow rate, and stable outlet temperature". The calculation formula for the target volumetric flow rate of the molten salt with thermal inertia compensation is as follows:

[0042] in, The target volumetric flow rate of molten salt in the branch corresponding to the i-th electric heater is expressed in units of... ; It is a dimensionless time unit conversion factor used to convert seconds in the International System of Units (SI) to hours, thereby unifying the units of flow rate. Let be the real-time target heating power of the i-th electric heater in the electric heating array, in units of . ; The thermal inertia time constant of the electrically heated molten salt system, in units of . The thermal inertia time constant was determined by a system step response experiment. The specific method was as follows: when the system was running in steady state, a step change was applied to the heating power, and the time required for the molten salt outlet temperature to reach 63.2% of the steady-state value of the step change was recorded. Let be the real-time target heating power change rate of the i-th electric heater, in units of . By controlling a set number of systems within a certain period of time in the past The time series is obtained by taking the first-order difference derivative. This is a thermal inertia hysteresis compensation term; as the heating power increases, When the compensation term is greater than 1, the target flow rate increases synchronously; when the heating power decreases, When the compensation term is less than 1, the target flow rate decreases synchronously; when the heating power is stable... The compensation term equals 1, and the formula reverts to the steady-state energy conservation equation. This refers to the isobaric specific heat capacity of molten salt, in units of... , which are the thermophysical properties of the molten salt material, determined according to the working temperature range of the molten salt; This is the density of the molten salt, in units of... , which are the thermophysical properties of the molten salt material, determined according to the working temperature range of the molten salt; The set outlet temperature of the molten salt, in °C, is determined based on the heat load requirements of downstream industries and is a fixed control target value set by the system. The real-time temperature of the molten salt inlet of the i-th electric heater is expressed in °C. It is acquired in real time through a thermocouple at the inlet of the electric heater, and the sampling period is consistent with the system control period.

[0043] Traditional energy conservation formulas only apply to steady-state conditions, assuming that power and flow rate changes are synchronized. However, in actual molten salt systems, due to the heat capacity of the heating tube wall and the molten salt itself, there is a significant time lag in the transmission of heating power changes to the molten salt outlet temperature. If the flow rate is calculated directly using the steady-state formula, the flow rate increase lags behind the power increase at the moment of power rise, leading to localized overheating of the heating tube and outlet temperature overshoot; conversely, the flow rate decrease lags behind at the moment of power decrease, resulting in outlet temperature undershoot. Therefore, this embodiment introduces a real-time target heating power change rate. A dynamic compensation mechanism was constructed, which offset the temperature response lag caused by the thermal inertia of molten salt through thermal inertia compensation term. In principle, it eliminated the temperature fluctuation of molten salt outlet caused by heating power fluctuation, provided accurate target value for subsequent actuator control, and significantly improved the temperature control stability of the system under dynamic operating conditions.

[0044] Step 4: Molten salt, as a special heat transfer medium, has physical properties closely related to temperature. Specifically, the dynamic viscosity of molten salt increases significantly as temperature decreases and decreases as temperature increases. In actual operation, the inlet temperature of molten salt is not constant but fluctuates due to factors such as tank level and environmental heat dissipation. When the inlet temperature of molten salt decreases, its dynamic viscosity increases, increasing the flow resistance of the fluid in the pipeline. With the molten salt pump frequency remaining constant, the actual volumetric flow rate decreases. Conversely, when the inlet temperature increases, the viscosity decreases, and the actual flow rate increases. If the target volumetric flow rate calculated in the aforementioned steps is directly used, and the deviation from the actual flow rate is ignored, the influence of viscosity changes will lead to a systematic deviation in flow control, thus affecting the stability of the outlet temperature. Therefore, this embodiment introduces a molten salt viscosity-temperature correction coefficient to correct the thermal inertia-compensated target volumetric flow rate of molten salt. This counteracts the influence of viscosity changes caused by variations in the molten salt inlet temperature on the actual flow rate, making the flow deviation calculation more closely match the actual operating characteristics of the system, and obtaining a molten salt flow deviation value with viscosity correction. The formula for calculating the molten salt flow deviation with viscosity correction is as follows:

[0045] in, For the first The molten salt flow deviation value for each system control cycle, in units of ; This is a dimensionless variable representing the sequence number of the system control cycle for the electrically heated molten salt system. It is used to identify discrete control cycles, and each control cycle completes one calculation and control command update. For the first Within each system control cycle, the target volumetric flow rate of molten salt in the branch corresponding to the i-th electric heater is the input parameter for this formula, and the units are converted to... Enter after, The real-time temperature of the molten salt inlet of the i-th electric heater during the k-th system control cycle; For the first The dynamic viscosity of the molten salt at the corresponding molten salt inlet temperature within each system control cycle, in units of... The viscosity-temperature characteristic of molten salt is calculated in real time using the following formula: ,in , This is the viscosity constant of the molten salt material, obtained through physical property testing of the molten salt material. For real-time acquisition of molten salt inlet temperature ; The dynamic viscosity of the molten salt at its rated operating temperature, in units of... , for molten salt at a set outlet temperature The viscosity value is calculated using the molten salt viscosity-temperature characteristic formula and is a fixed value.

[0046] in, This is the molten salt viscosity-temperature correction factor, dimensionless. When the molten salt inlet temperature is lower than the rated temperature, the molten salt viscosity-temperature correction factor is greater than 1, and the target flow rate setting is increased simultaneously to offset the flow loss caused by the increase in viscosity. When the molten salt inlet temperature is equal to the rated temperature, the molten salt viscosity-temperature correction factor is equal to 1, and no correction is performed. For the first Within each system control cycle, the actual volumetric flow rate of molten salt in the branch corresponding to the i-th electric heater, in units of... The data is collected in real time by electromagnetic flowmeters installed on branch pipelines, and the sampling period is consistent with the system control period.

[0047] It should be understood that although the above embodiments are illustrated using an inlet temperature lower than or equal to the rated temperature, in actual applications, the inlet temperature may also be higher than the rated temperature. When the inlet temperature is higher than the rated temperature, the viscosity correction coefficient is less than 1, and the system will correspondingly reduce the target flow rate setting to offset the actual flow rate gain caused by the decrease in viscosity and flow resistance, preventing excessive flow rate from causing temperature under-adjustment. This bidirectional correction mechanism ensures that the flow rate deviation calculation is always accurate and reliable under various inlet temperature fluctuation conditions. This embodiment introduces a viscosity correction mechanism to construct a linkage response chain of "temperature-viscosity-flow rate". This correction method not only compensates for the nonlinear effects caused by changes in fluid properties but also significantly improves the accuracy and robustness of the control system. Especially in scenarios where changes in molten salt tank level or a decrease in ambient temperature at night cause inlet temperature fluctuations, this correction mechanism can effectively avoid outlet temperature oscillations caused by flow control deviations, ensuring precise and stable control of the molten salt outlet temperature.

[0048] Step 5: Based on the incremental PID control algorithm and considering the characteristics of molten salt pump flow control, the incremental PID control algorithm was discretized and adapted. The dimensional matching relationship between the control cycle and each coefficient was clarified. Incremental output was adopted to convert the molten salt flow deviation value with viscosity correction into a frequency adjustment command for the molten salt pump. This achieved full-link linkage between the control algorithm and the preceding stages. Furthermore, the incremental output only outputs the frequency change, avoiding integral saturation problems and improving control stability. It also enables bumpless switching, adapting to the operational requirements of industrial sites. The frequency adjustment command for the molten salt pump is the adjustment value of the molten salt pump frequency. The calculation formula for the frequency adjustment command of the molten salt pump is as follows:

[0049] in, For the first Within each system control cycle, the output frequency command of the molten salt pump corresponding to the i-th electric heater in the branch is given in units of... ; For the first -1 system control cycle corresponds to the actual operating frequency of the molten salt pump, in units of The data is acquired in real time through the pump's frequency converter; The proportional gain is the value of the incremental PID control algorithm, in units of 1. It is obtained by tuning through the critical proportionality method or the attenuation curve method, and is used to quickly respond to flow deviations and reduce the static error of the system. These are the integral coefficients of the incremental PID control algorithm, in units of... It is obtained by tuning through the critical proportional method or the attenuation curve method, and is used to eliminate the steady-state deviation of the system and ensure error-free flow control. These are the differential coefficients of the incremental PID control algorithm, in units of... It is obtained by tuning through the critical proportional method or the attenuation curve method, and is used to predict the trend of deviation changes and suppress system overshoot and oscillation. The control cycle of the incremental PID control algorithm is given in units of 1200 m / s. This is a fixed value set for the system, determined based on the system's response characteristics and the control requirements of the industrial site. For the first The molten salt flow deviation value for each system control cycle, in units of ; For the first -1 system control cycle molten salt flow deviation value, in units of It is stored in the controller's register; For the first -2 system control cycles' molten salt flow deviation value, in units of It is stored in the controller's register.

[0050] Through the aforementioned incremental PID closed-loop control, the system accurately converts the flow deviation value calculated in the preceding steps into a frequency adjustment command for the molten salt pump. When the flow deviation is positive, it indicates that the target flow rate is greater than the actual flow rate. The algorithm outputs a positive frequency increment, and the frequency converter increases the pump speed, thereby increasing the flow rate. When the flow deviation is negative, the algorithm outputs a negative frequency increment, reducing the pump speed and decreasing the flow rate. Ultimately, by adjusting the frequency of the molten salt pump, the actual flow rate of the molten salt is controlled to approach the target flow rate, thus achieving precise and stable control of the molten salt outlet temperature. This completes the entire closed-loop control process, from wind and solar power fluctuation data acquisition, power demand quantification, array power allocation, flow thermal inertia compensation and viscosity correction, to the final actuator action.

[0051] Example 3 Based on Embodiment 2, this invention provides a method for stabilizing the outlet temperature of an electrically heated molten salt system. This embodiment applies to an electrically heated molten salt thermal storage system comprising N electric heaters and corresponding N branch molten salt pumps. The system is integrated with wind and solar power plants to absorb wind and solar power waste and provide stable steam to downstream industrial users. The system is equipped with a SCADA data acquisition system for the wind / solar power plant, thermocouples for the inlet and outlet temperatures of the electric heaters, branch electromagnetic flowmeters, frequency converters for the molten salt pumps, and a programmable logic controller (PLC) or distributed control system (DCS). All acquisition and execution devices are communicatively connected to the controller. The control method of this invention is implemented through the controller and executes cyclically according to a fixed control cycle T. The specific implementation steps are as follows: Before the system runs for the first time, the basic parameters are configured. All configuration parameters are stored in the controller's registers, including: (1) The system design parameters are the total number of electric heaters N and the effective heating area of ​​a single electric heater. Total rated heating power of the system Maximum allowable operating temperature of molten salt Molten salt outlet temperature setting ; (2) The physical properties of molten salt are the specific heat capacity of molten salt at constant pressure. molten salt density 1. Molten salt viscosity-temperature characteristic constants A and B; 2. Dynamic viscosity of molten salt at rated operating temperature. ; (3) The control parameter is the 1-minute short-cycle high-frequency fluctuation weighting coefficient. Weighting coefficients for 10-minute long-period low-frequency fluctuations Thermal inertia time constant of electrically heated molten salt system The control period T of the incremental PID control algorithm and the proportional coefficient of the incremental PID control algorithm. Integral coefficients of incremental PID control algorithm The derivative coefficients of the incremental PID control algorithm ; (4) Communication configuration: Configure the communication parameters between the controller and the SCADA system, thermocouples, flow meters, and frequency converters to ensure real-time data acquisition and normal command issuance.

[0052] At the beginning of each control cycle of the system, the controller completes the acquisition and preprocessing of real-time operating data, specifically including: (1) The wind and solar power output data is the real-time wind power output at the current time t. Real-time photovoltaic power output At the same time, the total power output of wind and solar power over the past 10 minutes is cached for calculation of the absolute value of fluctuations; (2) The electric heater operation data is the real-time inlet temperature of each electric heater. Real-time outlet temperature Real-time input power ; (3) The flow rate and pump operation data are the actual volume flow rate of molten salt collected for each branch. Current operating frequency of molten salt pump ; (4) Data preprocessing involves filtering the collected raw data to remove outliers and noise, ensuring the validity of the data.

[0053] The controller obtains wind and solar power fluctuation data based on the collected wind and solar power output data, and calculates the real-time power adjustment demand of the system based on the formula for calculating the real-time power adjustment demand of the wind and solar power fluctuations. Specifically, obtain the absolute value of the maximum fluctuation in the total output of the wind and light over the past minute. The absolute value of the maximum fluctuation in total power output of wind and light over the past 10 minutes Substituting the values ​​into the formula for calculating the real-time power regulation demand due to wind and solar fluctuations, the real-time power regulation demand due to wind and solar fluctuations of the system is calculated. The calculation results are then subjected to amplitude limiting, with the limiting range being the system's base operating power. To the system's rated total heating power This is to avoid calculation results exceeding the operating range of the equipment.

[0054] The controller adjusts the power demand based on real-time wind and solar power fluctuations. Calculate the real-time target heating power of each electric heater in the electric heating array. Specifically, first calculate the real-time electrothermal conversion efficiency of each electric heater. Real-time temperature margin And calculate the total allocation weight of all electric heaters. Finally, the real-time target heating power of each electric heater in the electric heating array is calculated by substituting the formula into the formula. The real-time target heating power of each electric heater in the electric heating array is obtained, and the calculation results of a single electric heater are limited. The limiting range is from the minimum operating power of a single electric heater to its rated power.

[0055] The controller calculates the corresponding thermal inertia-compensated target volumetric flow rate of molten salt based on the real-time target heating power of each electric heater in the electric heating array. Specifically, the real-time rate of change for each electric heater is first calculated. Then, a thermal inertia hysteresis compensation term is introduced. The target volumetric flow rate of molten salt with thermal inertia compensation was calculated. Finally, the calculation results are limited to a range from the minimum flow rate to the rated flow rate of the molten salt pump; and the units of the calculation results are changed from... Convert to This is used for subsequent deviation calculations.

[0056] The controller is based on the thermal inertia-compensated target volumetric flow rate of molten salt. Calculate the molten salt flow deviation with viscosity correction. Specifically, firstly, based on the first Real-time temperature of the molten salt inlet of the i-th heater in each system control cycle The real-time temperature of the molten salt inlet is calculated as follows: At that time, the dynamic viscosity of molten salt And a molten salt viscosity-temperature correction factor is introduced. Obtain the molten salt flow deviation value with viscosity correction. Simultaneously, cache the current cycle's molten salt flow deviation value with viscosity correction. This is used for calculating subsequent control cycles.

[0057] The controller retrieves the cached molten salt flow deviation value with viscosity correction from the previous cycle. Deviation value of molten salt flow rate with viscosity correction from the previous two cycles ; Calculate the frequency adjustment command of the molten salt pump for the current system control cycle. The calculation results are then subjected to amplitude limiting, with the limiting range being the minimum to maximum operating frequency of the molten salt pump inverter; the frequency adjustment command of the molten salt pump for the current control cycle is then applied. The command is sent to the frequency converter of the molten salt pump in the corresponding branch. The frequency converter executes the command to adjust the speed of the molten salt pump, change the molten salt flow rate, and finally achieve stable control of the molten salt outlet temperature.

[0058] After issuing the command for the current control cycle, the controller enters the next control cycle, repeats the above steps, and continuously updates the control command to achieve real-time stable control of the molten salt outlet temperature and full absorption of wind and solar fluctuations.

[0059] Example 4 Based on the method for stabilizing the outlet temperature of an electrically heated molten salt system proposed in Example 1, this example proposes a control system for stabilizing the outlet temperature of an electrically heated molten salt system, including a power demand calculation module, a power allocation module, a flow matching module, a viscosity correction module, and a frequency control module. The power demand calculation module is used to collect wind and solar fluctuation data in real time. Combining the thermal inertia characteristics of the electric heating molten salt system, it introduces frequency band fluctuation weight coefficients to assign differentiated response weights to the wind and solar fluctuation data and calculate the real-time power adjustment demand of wind and solar fluctuations. The power allocation module is used to adaptively allocate the power demand of the electric heating array according to the real-time power adjustment requirements of wind and solar fluctuations, and obtain the real-time target heating power of each electric heater in the electric heating array. The flow matching module is used to derive the thermal inertia-compensated target volumetric flow rate of molten salt by introducing a thermal inertia hysteresis compensation term based on the real-time target heating power of each electric heater in the electric heating array. The viscosity correction module is used to introduce a molten salt viscosity-temperature correction coefficient to correct the target volumetric flow rate of the molten salt with thermal inertia compensation, thereby obtaining the molten salt flow rate deviation value with viscosity correction. The frequency control module is used to convert the molten salt flow deviation value with viscosity correction into the frequency adjustment command of the molten salt pump based on the incremental PID control algorithm and combined with the characteristics of molten salt pump flow control.

[0060] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for stabilizing the outlet temperature of an electrically heated molten salt system, characterized in that, Includes the following steps: Real-time wind and solar fluctuation data are collected. Combined with the thermal inertia characteristics of the electrically heated molten salt system, frequency band fluctuation weight coefficients are introduced to assign differentiated response weights to the wind and solar fluctuation data and calculate the real-time power adjustment demand for wind and solar fluctuations. Adaptive allocation of electric heating array to the real-time power adjustment demand of wind and solar fluctuations, and obtain the real-time target heating power of each electric heater in the electric heating array; Based on the real-time target heating power of each electric heater in the electric heating array, a thermal inertia hysteresis compensation term based on the rate of change of heating power is introduced to derive the target volumetric flow rate of molten salt with thermal inertia compensation. A molten salt viscosity-temperature correction coefficient is introduced to correct the target volumetric flow rate of the molten salt with thermal inertia compensation, thereby obtaining the molten salt flow rate deviation value with viscosity correction. Based on the incremental PID control algorithm and combined with the characteristics of molten salt pump flow control, the molten salt flow deviation value with viscosity correction is converted into a frequency adjustment command for the molten salt pump.

2. The method for stabilizing the outlet temperature of an electrically heated molten salt system according to claim 1, characterized in that, The real-time acquired wind and solar power fluctuation data, combined with the thermal inertia characteristics of the electrically heated molten salt system, introduces frequency band fluctuation weighting coefficients to assign differentiated response weights to the wind and solar power fluctuation data, and calculates the real-time power adjustment demand for wind and solar power fluctuations. Specifically, based on the thermal inertia characteristics of the electrically heated molten salt system, frequency band fluctuation weighting coefficients are introduced to reduce the response weight of short-period high-frequency fluctuations in the wind and solar power fluctuation data, while providing a full response to long-period low-frequency fluctuations, thus deriving the real-time power adjustment demand for wind and solar power fluctuations. The formula for calculating the real-time power adjustment demand for wind and solar power fluctuations is as follows: in, Let t be the real-time power output of the wind farm. Let t be the real-time output value of the photovoltaic power station. This is the basic operating power for an electrically heated molten salt system. The weighting coefficients are for short-cycle, high-frequency fluctuations on the 1-minute timeframe. The weighting coefficients are for low-frequency fluctuations with long periods on the 10-minute timeframe. This represents the absolute value of the maximum fluctuation in the total power output sequence of wind and solar power over the past minute within the statistical period. This represents the absolute value of the maximum fluctuation in the total power output sequence of wind and solar power over the past 10 minutes within the statistical period. This refers to the rated total heating power of the electrically heated molten salt system.

3. The method for stabilizing the outlet temperature of an electrically heated molten salt system according to claim 1, characterized in that, The adaptive allocation of the real-time power adjustment demand for wind and solar power fluctuations to the electric heating array to obtain the real-time target heating power of each electric heater in the electric heating array is specifically as follows: During the heat flow distribution process of the electric heating molten salt system, the real-time electrothermal conversion efficiency and real-time temperature margin of a single electric heater are used as correction terms to adaptively assign weights to each electric heater in the electric heating array. Based on the weight allocation of each electric heater, the real-time power adjustment demand for wind and solar power fluctuations is allocated to each electric heater in the electric heating array to obtain the real-time target heating power of each electric heater in the electric heating array. The calculation formula for the real-time target heating power of each electric heater in the electric heating array is as follows: in, Let be the real-time target heating power of the i-th electric heater in the electric heating array. To meet the real-time power adjustment requirements for wind and solar power fluctuations. Let i be the effective heating area of ​​the i-th electric heater. Let be the real-time electrothermal conversion efficiency of the i-th electric heater. Let i be the real-time temperature margin of the i-th electric heater. This represents the total number of electric heaters in the electric heating array. This is the sequence number variable for the electric heaters in the electric heating array. Let n be the effective heating area of ​​the nth electric heater in the electric heating array. Let be the real-time electrothermal conversion efficiency of the nth electric heater in the electric heating array.

4. The method for stabilizing the outlet temperature of an electrically heated molten salt system according to claim 3, characterized in that, The step of using the real-time electrothermal conversion efficiency and real-time temperature margin of a single electric heater as correction terms specifically involves: real-time acquisition of the input power of the electric heater, the inlet and outlet temperatures of the molten salt, and the molten salt flow rate; calculation of the real-time electrothermal conversion efficiency of a single electric heater; and calculation of the real-time temperature margin of a single electric heater using the maximum allowable operating temperature and the real-time outlet temperature. The formula for calculating the real-time electrothermal conversion efficiency of a single electric heater is as follows: in, Let be the real-time electrothermal conversion efficiency of the i-th electric heater. The specific heat capacity of molten salt at constant pressure. The density of molten salt, Let i be the real-time molten salt flow rate of the i-th electric heater. Let be the real-time outlet temperature of the i-th heater. Let be the real-time inlet temperature of the i-th electric heater. Let be the real-time input electrical power of the i-th electric heater.

5. The method for stabilizing the outlet temperature of an electrically heated molten salt system according to claim 4, characterized in that, The formula for calculating the real-time temperature margin of a single electric heater is as follows: in, Let i be the real-time temperature margin of the i-th electric heater. This is the maximum permissible operating temperature of the molten salt.

6. The method for stabilizing the outlet temperature of an electrically heated molten salt system according to claim 1, characterized in that, The method involves deriving the target volumetric flow rate of molten salt based on the real-time target heating power of each electric heater in the electric heating array, using a thermal inertia hysteresis compensation term based on the rate of change of heating power. Specifically, based on the classical energy conservation formula for convective heat transfer, a thermal inertia hysteresis compensation term based on the rate of change of heating power is introduced. According to the real-time target heating power of each electric heater in the electric heating array, the thermal inertia hysteresis compensation term is used to offset the temperature response hysteresis caused by the thermal inertia of the molten salt, thereby calculating the corresponding thermal inertia-compensated target volumetric flow rate of the molten salt. The formula for calculating the target volumetric flow rate of the molten salt with thermal inertia compensation is as follows: in, Let be the real-time target heating power of the i-th electric heater in the electric heating array. The thermal inertia time constant of the electrically heated molten salt system. Let be the real-time target heating power change rate of the i-th electric heater. Set the outlet temperature for the molten salt. Let be the real-time temperature of the molten salt inlet of the i-th electric heater. This is a thermal inertia hysteresis compensation term. The specific heat capacity of molten salt at constant pressure. ρ is the density of the molten salt.

7. The method for stabilizing the outlet temperature of an electrically heated molten salt system according to claim 6, characterized in that, A molten salt viscosity-temperature correction coefficient is introduced to correct the target volumetric flow rate of the molten salt with thermal inertia compensation. This offsets the impact of viscosity changes caused by variations in the molten salt inlet temperature on the actual flow rate, making the flow deviation calculation more closely reflect the actual operating characteristics of the electrically heated molten salt system, thus obtaining a molten salt flow deviation value with viscosity correction. The formula for calculating the molten salt flow deviation with viscosity correction is as follows: in, For the system control cycle of the electrically heated molten salt system, The dynamic viscosity of the molten salt at its rated operating temperature. For the first The actual volumetric flow rate of molten salt in the i-th electric heater during each system control cycle. For the first The real-time temperature of the molten salt inlet of the i-th heater in each system control cycle. The dynamic viscosity of molten salt. The real-time temperature of the molten salt inlet is At that time, the dynamic viscosity of molten salt, This is the viscosity-temperature correction factor for molten salt.

8. The method for stabilizing the outlet temperature of an electrically heated molten salt system according to claim 7, characterized in that, The introduction of a molten salt viscosity-temperature correction coefficient to correct the target volumetric flow rate of the molten salt with thermal inertia compensation is specifically as follows: when the real-time temperature of the molten salt inlet of the i-th electric heater... When the temperature is below the rated temperature, the molten salt viscosity-temperature correction factor is greater than 1, and the target flow rate setpoint is increased synchronously to offset the flow loss caused by the increase in viscosity; when the real-time temperature of the molten salt inlet of the i-th electric heater... When the temperature is equal to the rated temperature, the viscosity-temperature correction factor of the molten salt is equal to 1, and no correction is made.

9. The method for stabilizing the outlet temperature of an electrically heated molten salt system according to claim 1, characterized in that, The incremental PID control algorithm, combined with the characteristics of molten salt pump flow control, converts the viscosity-corrected molten salt flow deviation value into a frequency adjustment command for the molten salt pump. Specifically, based on the characteristics of molten salt pump flow control, the incremental PID control algorithm is discretized and adapted, clarifying the dimensional matching relationship between the system control cycle and each coefficient. Incremental output is used to convert the viscosity-corrected molten salt flow deviation value into a frequency adjustment command for the molten salt pump. The frequency adjustment command is the adjustment value of the molten salt pump frequency, and the calculation formula for the molten salt pump frequency adjustment command is as follows: in, For the system control cycle of the electrically heated molten salt system, For the first Within each system control cycle, the output frequency adjustment value of the molten salt pump corresponding to the i-th electric heater in the branch is... For the first Within one system control cycle, the output frequency adjustment value of the molten salt pump in the branch corresponding to the i-th electric heater. The proportional coefficient of the PID control algorithm. The integral coefficients of the PID control algorithm are... These are the differential coefficients of the PID control algorithm. The control cycle of the incremental PID control algorithm. For the first The viscosity-corrected molten salt flow rate deviation value for each system control cycle. For the first -1 system control cycle of molten salt flow deviation with viscosity correction. For the first -2 system control cycles of molten salt flow deviation with viscosity correction.

10. A control system for stabilizing the outlet temperature of an electrically heated molten salt system, based on the method for stabilizing the outlet temperature of an electrically heated molten salt system according to any one of claims 1 to 9, characterized in that, It includes a power demand calculation module, a power allocation module, a flow matching module, a viscosity correction module, and a frequency control module; The power demand calculation module is used to collect wind and solar fluctuation data in real time. Combining the thermal inertia characteristics of the electric heating molten salt system, it introduces frequency band fluctuation weight coefficients to assign differentiated response weights to the wind and solar fluctuation data and calculate the real-time power adjustment demand of wind and solar fluctuations. The power allocation module is used to adaptively allocate the power demand of the electric heating array according to the real-time power adjustment requirements of wind and solar fluctuations, and obtain the real-time target heating power of each electric heater in the electric heating array. The flow matching module is used to derive the target volume flow rate of molten salt by introducing a thermal inertia hysteresis compensation term based on the real-time target heating power of each electric heater in the electric heating array. The viscosity correction module is used to introduce a molten salt viscosity-temperature correction coefficient to correct the target volumetric flow rate of the molten salt with thermal inertia compensation, thereby obtaining the molten salt flow rate deviation value with viscosity correction. The frequency control module is used to convert the molten salt flow deviation value with viscosity correction into the frequency adjustment command of the molten salt pump based on the classic incremental PID control algorithm and the characteristics of molten salt pump flow control.

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