A novel frequency modulation method and system for a molten salt energy storage coupled thermal power unit

Abstract

The present invention discloses a novel frequency modulation method and system for a molten salt energy storage coupled thermal power unit. The method includes: monitoring the grid frequency through a frequency detection module and dividing levels according to the deviation amplitude; collecting data through a parameter acquisition module, performing denoising processing, and using a frequency modulation control module for primary frequency modulation; decomposing the frequency signal by the wavelet packet decomposition method, and the thermal power unit and the molten salt energy storage module cooperate to perform secondary frequency modulation; separating the high and low frequency components by using the ensemble empirical mode decomposition method, and the thermal power unit and the molten salt energy storage module cooperate to perform tertiary frequency modulation; recording the frequency fluctuations and output conditions through a data recording and feedback module, and adjusting parameters according to the feedback data; monitoring the status of each module in real time, and if the fluctuations exceed the safe range or a fault occurs, starting the fault detection and standby module; after the frequency is stable, the system gradually exits the frequency modulation mode and returns to the initial monitoring state, and all modules enter the standby state. The present invention effectively improves the grid frequency modulation response speed and stability.

Description

Technical Field

[0001] The present invention relates to the technical field of power grid frequency modulation, and particularly relates to a novel frequency modulation method and system for molten salt energy storage coupled with thermal power units. Background Art

[0002] The combined thermal energy storage and frequency modulation can significantly improve the frequency modulation performance of thermal power units, and can quickly and effectively reduce the shortage of system frequency modulation capacity. Traditional frequency modulation methods mainly rely on the fast response ability of thermal power units, but limited by the response speed and regulation flexibility of thermal power units themselves, they cannot meet the fast response requirements of modern power grids for frequency fluctuations. This leads to difficulties in maintaining power grid stability under large-amplitude frequency fluctuations, and there are defects such as low frequency regulation accuracy and long response time.

[0003] Currently, in practical applications, the frequency modulation effect of the molten salt energy storage module and the thermal power unit is easily affected by multiple factors such as the operating state of the equipment, the frequency and amplitude of frequency fluctuations; the current frequency modulation system lacks a flexible hierarchical response mechanism, resulting in insufficient fineness of frequency modulation control and difficulty in achieving effective regulation under different frequency deviation amplitudes.

[0004] In view of the above problems, the present invention provides a novel frequency modulation method and system for molten salt energy storage coupled with thermal power units. Through a frequency detection module, real-time frequency monitoring is achieved. Combining advanced algorithms such as wavelet packet decomposition and ensemble empirical mode decomposition, the frequency signal is decomposed, and the frequency modulation requirements are flexibly allocated to the thermal power unit and the molten salt energy storage module. Under different frequency fluctuation conditions, this system can achieve hierarchical frequency modulation and adaptive adjustment, ensuring that the system has higher frequency modulation accuracy and response speed. Summary of the Invention

[0005] In view of the above problems, the present invention provides a novel frequency modulation method and system for molten salt energy storage coupled with thermal power units to solve the problem that the frequency modulation effect of the existing molten salt energy storage module and the thermal power unit is easily affected by multiple factors such as the operating state of the equipment, the frequency and amplitude of frequency fluctuations.

[0006] To solve the above technical problems, the present invention provides the following technical solutions:

[0007] The present invention provides a novel frequency modulation method for molten salt energy storage coupled with thermal power units, which is characterized by including:

[0008] Step S1, monitoring the power grid frequency through a frequency detection module and dividing levels according to the deviation amplitude;

[0009] Wherein in step S1, the following sub-steps are further included:

[0010] S1-1. Using a frequency detection module, the synchronous phasor measurement device is used to monitor the changes in voltage and current in real time, capture the minute fluctuations in frequency, and continuously detect the frequency fluctuations of the power grid.

[0011] S1-2. Classify the frequency levels according to the amplitude of the frequency deviation, and divide the fluctuation situation into three levels, specifically as follows:

[0012] Level 1: Mild frequency fluctuation, with a deviation within 0.1 Hz.

[0013] Level 2: Moderate frequency fluctuation, with a deviation between 0.1 - 0.2 Hz.

[0014] Level 3: High frequency fluctuation, with a deviation exceeding 0.2 Hz.

[0015] Step S2. Collect data through the parameter acquisition module, perform denoising processing, and use the frequency modulation control module for primary frequency modulation.

[0016] Among them, in step S2, the following sub-steps are also included:

[0017] S2-1. Obtain temperature, pressure, rotational speed, and power parameters through the temperature sensor, pressure sensor, rotational speed sensor, and power sensor in the parameter acquisition module.

[0018] S2-2. Use the double-threshold method combined with a moving average filter to remove noise, and combine the three-sigma rule and the local outlier factor algorithm for outlier detection, identify and remove or correct abnormal data points, specifically as shown in equations (1) - (4):

[0019] Equation (1)

[0020] Equation (2)

[0021] Equation (3)

[0022] Equation (4)

[0023] Among them, is a certain data point in the original data sequence, is the data point after being processed by the double-threshold method, , are the upper and lower threshold values respectively, is invalid data; is the smoothed data value after moving average filtering, is the size of the moving window, i is the relative position of the data point, is used to initialize the window of the filter, Data points after being processed by the double-threshold method, data points at time t-i; is the mean value of the data, is the standard deviation, is a certain data point in the dataset; is the local outlier factor of point p, k is the number of neighbors, is the set of k neighbors of point p, o is a neighbor of point p, is the local reachability density of point p, is the local reachability density of point o;

[0024] S2-3, through the frequency modulation control module, uses the fuzzy adaptive PID algorithm to dynamically adjust according to different frequency deviation situations, specifically as shown in Equation (5):

[0025] Equation (5)

[0026] where, is the error value, is the parameter automatically adjusted by the fuzzy controller according to the real-time frequency error;

[0027] S2-4, after the frequency adjustment is completed, return to the monitoring mode.

[0028] Step S3, decompose the frequency signal by the wavelet packet decomposition method, and the thermal power unit and the molten salt energy storage module work together for secondary frequency modulation;

[0029] Among them, in step S3, the following sub-steps are also included:

[0030] S3-1, allocate the frequency modulation demand to the thermal power unit module and the molten salt energy storage module according to the frequency fluctuation signal. The thermal power unit module is responsible for the preliminary adjustment, and the molten salt energy storage module is responsible for frequency stabilization;

[0031] S3-2, use the wavelet packet decomposition technology to decompose the frequency modulation signal into high-frequency and low-frequency components. The high-frequency part is responded by the thermal power unit module, and the low-frequency part is borne by the molten salt energy storage module, specifically as shown in Equation (6) - Equation (7):

[0032] Equation (6)

[0033] Equation (7)

[0034] Among them, the decomposition level is n, the wavelet packet decomposition coefficient is d, the frequency band node number is represented by j, the low-pass filter coefficient is represented by b, the high-pass filter coefficient is represented by a, the low-pass filter coefficient is represented by l, and the frequency band number is represented by k;

[0035] S3-3. The thermal power unit module undertakes the rapid frequency regulation task to cope with instantaneous frequency fluctuations; the molten salt energy storage module provides support for the low-frequency component.

[0036] S3-4. Monitor the frequency recovery situation in real time and adjust the output of the molten salt energy storage module according to the frequency change.

[0037] Step S4. Use the ensemble empirical mode decomposition method to separate the high-frequency and low-frequency components. The thermal power unit module and the molten salt energy storage module work together, and the combined heat and power supply module and the molten salt energy storage module cooperate to adjust to cope with large fluctuations for tertiary frequency modulation.

[0038] Among them, in step S4, the following sub-steps are also included:

[0039] S4-1. Decompose the load command into a high-frequency signal and a low-frequency signal through the ensemble empirical mode decomposition method, specifically as shown in Equation (8) - Equation (10):

[0040] Equation (8)

[0041] Equation (9)

[0042] Equation (10)

[0043] Among them, is the signal to be decomposed, is the -th order intrinsic mode component of the original signal, is the decomposition residue, is the decomposition order; represents the high-frequency signal, represents the low-frequency signal, and d represents the wavelet packet decomposition coefficient; Equation (9) is the sum of the intrinsic mode components with orders less than or equal to for the higher-frequency part; Equation (10) is the sum of the intrinsic mode components with orders greater than and the residue for the lower-frequency part;

[0044] S4-2. The thermal power unit module and the molten salt energy storage module work together. The molten salt energy storage module provides long-term output to cope with continuous low-frequency fluctuations, and the thermal power unit module responds to short-term high-frequency fluctuations.

[0045] S4-3. When the grid frequency fluctuates significantly and continuously, the thermal energy of the molten salt energy storage module is transferred to the grid through the thermoelectric conversion device.

[0046] S4-4. The molten salt energy storage module adjusts the heat supply output through the combined heat and power supply module, and uses the feedforward control strategy to link the demand at the heat supply end with the output of the molten salt energy storage module.

[0047] Step S5: Record the frequency fluctuation and output situation through the data recording and feedback module, and adjust the parameters according to the feedback data;

[0048] Among them, in step S5, the following sub-steps are also included:

[0049] S5-1: Through the data recording and feedback module, during the frequency modulation process, record the frequency fluctuation situation and the output data of the thermal power generation unit module and the molten salt energy storage module in real time;

[0050] S5-2: According to the real-time monitoring data, use the data feedback mechanism and intelligent control algorithm to adjust the output parameters of the thermal power generation unit module and the molten salt energy storage module.

[0051] Step S6: Monitor the status of each module in real time. If the fluctuation exceeds the safe range or a fault occurs, immediately start the fault detection and standby module;

[0052] Among them, in step S6, the following sub-steps are also included:

[0053] S6-1: Through the fault detection and standby module, monitor the operating status of the thermal power generation unit module and the molten salt energy storage module in real time, and judge whether there is an abnormal status in the operating status;

[0054] S6-2: Use the overrun judgment mechanism to start the standby energy storage device when it is detected that the frequency fluctuation meets the third-level standard or a device failure occurs.

[0055] Step S7: Through the reset and recovery module, after the frequency is stable, the system gradually exits the frequency modulation mode, resumes to the initial monitoring state, and all modules enter the standby state.

[0056] Among them, in step S7, the following sub-steps are also included:

[0057] S7-1: Through the reset and recovery module, after the frequency returns to the stable state, adopt the phased exit method to gradually reduce the output of the molten salt energy storage module and the thermal power generation unit module, and return to the initial monitoring mode;

[0058] S7-2: After detecting that the data remains within the normal range for a period of time, trigger the automatic reset mechanism in the reset and recovery module to make each module return to the standby state after the frequency modulation task is completed.

[0059] Furthermore, a new type of frequency modulation system for a molten salt energy storage coupled with a thermal power generation unit includes:

[0060] Frequency detection module, parameter acquisition module, frequency modulation control module, thermal power generation unit module, molten salt energy storage module, combined heat and power module, data recording and feedback module, fault detection and standby module, reset and recovery module;

[0061] The frequency detection module is used to continuously monitor the grid frequency to obtain grid frequency deviation information, and transmit the detected frequency data to the system to trigger corresponding frequency modulation responses;

[0062] The parameter acquisition module includes temperature, pressure, rotational speed, and power sensors, and is used to collect the operating parameters of the thermal power generation unit module and the molten salt energy storage module in real time;

[0063] The frequency modulation control module includes a fuzzy adaptive PID controller and an algorithm processor, and triggers corresponding frequency modulation operations according to different levels of frequency deviation, and is used to analyze data and adjust the output parameters of the thermal power generation unit module and the molten salt energy storage module;

[0064] The thermal power generation unit module is used to quickly respond to high-frequency frequency fluctuations. When the grid frequency undergoes instantaneous fluctuations, it quickly adjusts the output power to help the grid return to a stable state;

[0065] The molten salt energy storage module is used to handle low-frequency fluctuations and long-term frequency stability, provide continuous power output, and at the same time provide additional power support for the system through a thermoelectric conversion device when the grid frequency fluctuates;

[0066] The cogeneration module is connected to the molten salt energy storage module, and can adjust the heating output according to the situation of grid frequency fluctuations, and link the heating demand with the power output of the energy storage system through feedforward control;

[0067] The data recording and feedback module is used to record and store various data of the system during the frequency modulation process, including frequency fluctuations, output conditions of the thermal power generation unit module and the molten salt energy storage module;

[0068] The fault detection and standby module is used to monitor the status of the entire system in real time. When it detects that the frequency fluctuation in the system exceeds the safe range or a certain module fails, it immediately starts the standby energy storage device;

[0069] The reset and recovery module is responsible for gradually exiting the frequency modulation mode, returning the system to the initial monitoring state, setting all modules to the standby state, and gradually restoring the heat of the molten salt energy storage module to the normal level to prepare for the next frequency modulation demand.

[0070] Compared with the prior art, the beneficial effects of the present invention are:

[0071] The novel frequency modulation method for a molten salt energy storage coupled thermal power unit of the present invention includes: monitoring the grid frequency through a frequency detection module and dividing levels according to the deviation amplitude; collecting data through a parameter acquisition module, performing denoising processing, and using a frequency modulation control module for primary frequency modulation; decomposing the frequency signal by the wavelet packet decomposition method, and the thermal power unit and the molten salt energy storage module work together for secondary frequency modulation; separating the high and low frequency components using the ensemble empirical mode decomposition method, the thermal power unit module and the molten salt energy storage module work together, and the combined heat and power supply module and the molten salt energy storage module cooperate to adjust to cope with large fluctuations for tertiary frequency modulation; recording the frequency fluctuations and output conditions through a data recording and feedback module, and adjusting parameters according to the feedback data; monitoring the status of each module in real time, and immediately starting the fault detection and standby module if the fluctuations exceed the safe range or a fault occurs; through the reset and recovery module, after the frequency stabilizes, the system gradually exits the frequency modulation mode, resumes to the initial monitoring state, and all modules enter the standby state.

[0072] The novel frequency modulation system for a molten salt energy storage coupled thermal power unit includes: a frequency detection module, a parameter acquisition module, a frequency modulation control module, a thermal power unit module, a molten salt energy storage module, a combined heat and power supply module, a data recording and feedback module, a fault detection and standby module, and a reset and recovery module.

[0073] The present invention performs hierarchical processing on the frequency signal through algorithms such as wavelet packet decomposition and ensemble empirical mode decomposition, and hands over the high-frequency fluctuations to the thermal power unit for response, while the low-frequency fluctuations are gently adjusted by the molten salt energy storage module. This hierarchical frequency modulation strategy effectively improves the accuracy and response speed of frequency modulation, and can better meet the adjustment requirements for different frequency fluctuation amplitudes.

[0074] During the frequency modulation process of the system of the present invention, the data recording and feedback module records the frequency fluctuations and output conditions in real time, and dynamically adjusts the outputs of the thermal power unit and the molten salt energy storage module according to the feedback data, ensuring that the system can automatically optimize the frequency modulation parameters according to the real-time situation, thereby further improving the frequency modulation effect and system stability.

[0075] The present invention introduces a fault detection and standby module. When the frequency fluctuations in the system exceed the safe range or a device failure occurs, the system will immediately start the standby energy storage device to prevent large fluctuations in the grid frequency caused by device failures, effectively improving the reliability and safety of the system, and ensuring the frequency stability of the power grid in case of emergencies. Brief Description of the Drawings

[0076] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0077] Figure 1 is the flowchart of the method of the present invention;

[0078] Figure 2 is the system architecture diagram of the present invention. Specific embodiments

[0079] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but is merely for the selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0080] Please refer to Figure 1 is the flowchart of a novel frequency modulation method for a molten salt energy storage coupled thermal power unit provided by an embodiment of the present invention, including the following steps:

[0081] Step S1, monitoring the grid frequency through a frequency detection module and dividing into levels according to the deviation amplitude;

[0082] Among them, in step S1, the following sub-steps are further included:

[0083] S1-1, through the frequency detection module, using a synchronized phasor measurement unit to monitor the changes in voltage and current in real time, capturing minute frequency fluctuations, and continuously detecting the grid frequency fluctuations;

[0084] S1-2, dividing the frequency levels according to the frequency deviation amplitude, classifying the fluctuation conditions into three levels, specifically as follows:

[0085] Level 1: Mild frequency fluctuation, with a deviation within 0.1 Hz;

[0086] Level 2: Moderate frequency fluctuation, with a deviation between 0.1 - 0.2 Hz;

[0087] Level 3: High frequency fluctuation, with a deviation exceeding 0.2 Hz.

[0088] It should be noted that the synchronized phasor measurement unit (PMU) synchronously measures the voltage and current phasors of each node in the power grid based on the precise time signal provided by the global positioning system;

[0089] The PMU measures the amplitude and phase angle of voltage and current in real time, generates accurate phasor data. These phasors represent the instantaneous state of the power grid and can quickly reflect the dynamic changes of the power system. When a fault occurs in the power grid, the PMU can quickly locate the fault location by analyzing the abnormal changes in the phasor data, helping the power grid system to isolate the fault and reduce the scope of the accident impact.

[0090] Step S2, collect data through the parameter acquisition module, perform denoising processing, and use the frequency modulation control module for primary frequency modulation;

[0091] Among them, in step S2, the following sub-steps are also included:

[0092] S2-1, obtain temperature, pressure, speed, and power parameters through the temperature sensor, pressure sensor, speed sensor, and power sensor in the parameter acquisition module;

[0093] S2-2, use the double-threshold method combined with the moving average filter to remove noise, combine the three-sigma rule and the local outlier factor algorithm for outlier detection, identify and remove or correct abnormal data points, specifically as shown in equations (1)-(4):

[0094] Equation (1)

[0095] Equation (2)

[0096] Equation (3)

[0097] Equation (4)

[0098] Among them, is a certain data point in the original data sequence, is the data point after being processed by the double-threshold method, and are the upper and lower threshold values respectively, is invalid data; is the smoothed data value after moving average filtering, is the size of the moving window, i is the relative position of the data point, is used to initialize the window of the filter, is the data point at time t-i of the data point after being processed by the double-threshold method; is the mean value of the data, is the standard deviation, is a certain data point in the dataset; is the local outlier factor of point p, k is the number of neighbors, is the set of k neighbors of point p, o is a neighbor of point p, is the local reachability density of point p, is the local reachability density of point o;

[0099] S2-3. Through the frequency modulation control module, the fuzzy adaptive PID algorithm is used to dynamically adjust according to different frequency deviation conditions, specifically as shown in Equation (5):

[0100] Equation (5)

[0101] where is the error value, is the parameter automatically adjusted by the fuzzy controller according to the real-time frequency error;

[0102] S2-4. After the frequency adjustment is completed, return to the monitoring mode.

[0103] It should be noted that the double-threshold method combined with the moving average filter is used to remove noise for processing the noise signal in the data, enhancing the smoothness and accuracy of the signal: The moving average filter smooths the data by taking the average of a group of consecutive data points, thereby reducing the influence of random noise. By continuously moving the window to calculate the local average of the current data point, the data becomes smoother. The double-threshold method introduces two thresholds, usually a high threshold and a low threshold. During data processing, if a certain data point exceeds the high threshold, it is considered that the fluctuation of this point may be a signal rather than noise, and this point is retained; if the data point is lower than the low threshold, it is considered that the fluctuation is not significant and may be noise, and this point is filtered out; the values between the high and low thresholds need to be further processed, either retained or smoothed.

[0104] The three-sigma rule combined with the local outlier factor algorithm is used for outlier detection to detect outliers in the data and identify abnormal system states or faults: The three-sigma rule is based on the assumption of a normal distribution, believing that the data within three standard deviations above and below the mean is normal data, and the data outside this range is abnormal data; the local outlier factor algorithm is an unsupervised outlier detection algorithm that determines whether a point is an outlier by comparing the density of each data point with other points in its neighborhood; the combination of the three-sigma rule and the local outlier factor algorithm can timely eliminate noise interference when obvious global outliers are detected, and at the same time identify potential local outlier data.

[0105] The fuzzy adaptive PID algorithm is an intelligent control algorithm that combines fuzzy logic and PID control. It can automatically adjust the parameters of the PID controller according to the system state and is applicable to nonlinear or dynamically changing systems. The fuzzy controller first obtains the current error of the system (the difference between the actual value and the target value) and the change rate of the error. These two values are used as input variables to judge the state of the system. Based on the preset fuzzy rule base, the error and the change rate of the error are transformed into fuzzy linguistic variables, and the combination of these variables is used to determine the increment of the PID parameters. The fuzzy controller calculates the appropriate adjustment amount of the PID parameters through fuzzy inference according to the rule base and the input variables. These adjustments are processed in the steps of fuzzification, inference, and defuzzification, and specific values are output. The results of the fuzzy inference are applied to the PID controller to update the values in real time, enabling the PID controller to better adapt to the current state of the system.

[0106] Step S3: Decompose the frequency signal by the wavelet packet decomposition method, and the thermal power unit and the molten salt energy storage module work together for secondary frequency regulation;

[0107] In step S3, the following sub-steps are further included:

[0108] S3-1: Allocate the frequency regulation demand to the thermal power unit module and the molten salt energy storage module according to the frequency fluctuation signal. The thermal power unit module is responsible for preliminary regulation, and the molten salt energy storage module is responsible for frequency stabilization;

[0109] S3-2: Use the wavelet packet decomposition technology to decompose the frequency regulation signal into high-frequency and low-frequency components. The high-frequency part is responded by the thermal power unit module, and the low-frequency part is borne by the molten salt energy storage module, specifically as shown in Equation (6) - Equation (7):

[0110] Equation (6)

[0111] Equation (7)

[0112] Where the decomposition level is n, the wavelet packet decomposition coefficient is d, the frequency band node number is represented by j, the low-pass filter coefficient is represented by b, the high-pass filter coefficient is represented by a, the low-pass filter coefficient is represented by l, and the frequency band number is represented by k;

[0113] S3-3: The thermal power unit module undertakes the task of rapid frequency regulation to cope with instantaneous frequency fluctuations; the molten salt energy storage module provides support for the low-frequency components;

[0114] S3-4: Real-time monitor the frequency recovery situation and adjust the output of the molten salt energy storage module according to the change of the frequency.

[0115] It should be noted that after the initial signal (0, 0) is collected, the high-frequency signal (1, 1) and the low-frequency signal (1, 0) are obtained through the wavelet packet decomposition technique. These two signals are decomposed by wavelet packet again, and this process is repeated three times; finally, according to the frequency, the frequencies of each sub-signal are arranged.

[0116] The characteristic of the thermal power generation unit module is its fast response speed, which can adjust the output power within a short time and is suitable for dealing with instantaneous frequency fluctuations, that is, the changes in high-frequency components; when the grid frequency suddenly has small but rapid fluctuations, the thermal power generation unit module can respond immediately and quickly balance the power demand of the grid by adjusting its own output to prevent excessive frequency deviation.

[0117] The advantage of the molten salt energy storage module lies in its large energy storage capacity and stable energy output, which is suitable for dealing with slow frequency changes, that is, the fluctuations of low-frequency components. Low-frequency fluctuations are usually caused by large and continuous load changes and require long-term power balance; the molten salt energy storage module provides a stable power output by slowly releasing or absorbing energy to help the system cope with this long-term frequency fluctuation and maintain the frequency stability of the power grid.

[0118] Step S4, using the ensemble empirical mode decomposition method to separate high- and low-frequency components, the thermal power generation unit module and the molten salt energy storage module work together, and the combined heat and power supply module and the molten salt energy storage module cooperate to adjust to cope with large fluctuations for tertiary frequency modulation;

[0119] Among them, in step S4, the following sub-steps are also included:

[0120] S4-1, through the ensemble empirical mode decomposition method, decompose the load command into a high-frequency signal and a low-frequency signal, specifically as shown in equations (8)-(10):

[0121] Equation (8)

[0122] Equation (9)

[0123] Equation (10)

[0124] Among them, is the signal to be decomposed, is the th order intrinsic mode component of the original signal, is the decomposition residue, is the decomposition order; represents the high-frequency signal, represents the low-frequency signal, and d represents the wavelet packet decomposition coefficient; Equation (9) is the sum of the intrinsic mode components with orders less than or equal to which is the higher-frequency part; Equation (10) is for the orders greater than The sum of the intrinsic mode components and the remainder is the part with a lower frequency;

[0125] S4-2. The thermal power unit module and the molten salt energy storage module work together. The molten salt energy storage module provides long-term output to cope with continuous low-frequency fluctuations, and the thermal power unit module responds to short-term high-frequency fluctuations;

[0126] S4-3. When the grid frequency fluctuates significantly continuously, the thermal energy of the molten salt energy storage module is transferred to the grid through a thermoelectric conversion device;

[0127] S4-4. The molten salt energy storage module adjusts the heat supply output through a combined heat and power module, and uses a feedforward control strategy to link the demand at the heat supply end with the output of the molten salt energy storage module.

[0128] It should be noted that ensemble empirical mode decomposition is a signal processing method, which is an improvement of empirical mode decomposition. It is often used to decompose complex signals into multiple intrinsic mode functions, and can better process the noise and unstable components in the signal, and more finely analyze the frequency components and characteristics of the signal.

[0129] The load instruction is a control signal issued by the system, which is used to adjust the power output of each module to meet the grid demand; during the grid frequency regulation process, the load instruction is used to indicate the thermal power unit or energy storage module to increase or decrease the power output to achieve frequency stability. These instructions are usually generated by the frequency regulation control module based on real-time frequency deviation, load demand and system status information.

[0130] The process of the feedforward control strategy is as follows: The system monitors the parameters at the heat supply end to predict the future heat supply demand; according to the predicted demand, the system adjusts the output of the molten salt energy storage module without waiting for the actual change to occur, ensuring that the heat supply end can obtain the required heat when the change occurs; the output of the heat supply end and the molten salt energy storage module are linked under the feedforward control strategy to achieve a fast response, reduce the fluctuations at the heat supply end, and improve the stability of the heat supply and power regulation of the system.

[0131] Step S5. Record the frequency fluctuations and output conditions through the data recording and feedback module, and adjust the parameters according to the feedback data;

[0132] Among them, in step S5, the following sub-steps are also included:

[0133] S5-1. Through the data recording and feedback module, during the frequency regulation process, the frequency fluctuation conditions and the output data of the thermal power unit module and the molten salt energy storage module are recorded in real time;

[0134] S5-2. According to the real-time monitoring data, use the data feedback mechanism and intelligent control algorithm to adjust the output parameters of the thermal power unit module and the molten salt energy storage module.

[0135] It should be noted that when the grid frequency fluctuation is detected, the system will analyze the amplitude and frequency components of the fluctuation to determine the high-frequency components that require rapid response and the low-frequency components that require continuous regulation;

[0136] The thermal power generation unit module is mainly responsible for responding to short-term high-frequency fluctuations. By adjusting its output power, that is, accelerating or slowing down the fuel supply, rapidly increasing or decreasing the power generation, it helps the power grid to cope with instantaneous frequency changes; the molten salt energy storage module is suitable for coping with low-frequency fluctuations and long-term frequency stability requirements. By adjusting its thermoelectric conversion output, the molten salt energy storage module can provide continuous power support and gradually restore the frequency to a stable state.

[0137] Step S6, monitor the status of each module in real time. If the fluctuation exceeds the safe range or a fault occurs, immediately start the fault detection and standby module;

[0138] Among them, in step S6, the following sub-steps are also included:

[0139] S6-1, through the fault detection and standby module, monitor the operating status of the thermal power generation unit module and the molten salt energy storage module in real time, and judge whether there is an abnormal state in the operating status;

[0140] S6-2, utilize the overrun judgment mechanism to start the standby energy storage device when it is detected that the frequency fluctuation meets the third-level standard or a device failure occurs.

[0141] It should be noted that the overrun judgment mechanism is a monitoring and control method used to detect whether system parameters exceed the preset safety thresholds. By setting a set of upper and lower threshold values, it judges whether the key parameters of the system exceed the allowable range; when the parameters exceed these thresholds, the system will trigger an alarm or protection measures to ensure safety and stability.

[0142] According to the frequency fluctuations, they are divided into different levels. Among them, exceeding 0.2Hz is defined as the third-level fluctuation, that is, the highest level of frequency fluctuation; the system divides the frequency deviation into multiple threshold levels, namely the first level, the second level and the third level; each level corresponds to a different frequency deviation range, and the third level is the highest level (exceeding 0.2Hz), indicating that the system is in a state of large fluctuations; the frequency detection module in the system will continuously monitor the grid frequency and compare it with the set threshold levels in real time; if the detected frequency deviation reaches or exceeds 0.2Hz, that is, exceeds the second level, the system will judge it as the third-level fluctuation state. Once the overrun judgment mechanism detects the third-level fluctuation (that is, exceeding 0.2Hz), the system will immediately start the corresponding emergency response to quickly balance the power grid and reduce the impact of the frequency deviation.

[0143] Step S7, through the reset and recovery module, after the frequency is stable, the system gradually exits the frequency modulation mode, resumes to the initial monitoring state, and all modules enter the standby state.

[0144] Among them, in step S7, the following sub-steps are further included:

[0145] S7-1. After the frequency is restored to the stable state through the reset and recovery module, the phased exit method is adopted to gradually reduce the outputs of the molten salt energy storage module and the thermal power unit module, and return to the initial monitoring mode;

[0146] S7-2. After detecting that the data remains within the normal range for a period of time, trigger the automatic reset mechanism in the reset and recovery module to make each module return to the standby state after the frequency modulation task is completed.

[0147] It should be noted that the phased exit method is a strategy for the frequency modulation system to gradually reduce the output of each module when the frequency fluctuation gradually returns to stability, so that the system can smoothly transition to the initial monitoring state; when the grid frequency returns to the safe range, the system will not immediately stop the frequency modulation operation completely, but gradually reduce the power outputs of the thermal power unit and the molten salt energy storage module through the reset and recovery module to avoid the impact on the system caused by sudden changes; the system gradually reduces the frequency modulation output according to the amplitude and stable trend of the frequency deviation, from a higher power regulation to a lower compensation amount until the frequency deviation approaches zero; at each stage, the system will confirm the stability of the frequency before continuing to reduce the output; this phased exit process ensures a smooth transition when exiting the frequency modulation, preventing secondary fluctuations or instantaneous offsets of the frequency caused by rapid switching.

[0148] The automatic reset mechanism means that after the frequency modulation task is completed, each module of the system can automatically return to the standby state to prepare for the next frequency modulation demand; when the frequency is restored to stability and exits the frequency modulation mode, the reset and recovery module will gradually reduce the temperature and power output of the molten salt energy storage module through the automatic reset mechanism and return it to the standby state; during the reset process, the system will monitor the energy state of the energy storage module to ensure that its energy reserve is full to provide sufficient support for the next frequency fluctuation, which includes monitoring the recovery of the power or heat of the energy storage module to ensure that the reserve state is normal; the thermal power unit and other auxiliary modules will also return to the standby state according to the automatic reset mechanism to ensure that the entire system has the ability to respond quickly at any time.

[0149] Please refer to Figure 2 FIG. is a new frequency modulation system architecture diagram of a molten salt energy storage coupled with a thermal power unit provided by an embodiment of the present invention, including:

[0150] A frequency detection module, a parameter acquisition module, a frequency modulation control module, a thermal power unit module, a molten salt energy storage module, a combined heat and power module, a data recording and feedback module, a fault detection and standby module, a reset and recovery module;

[0151] The frequency detection module is used to continuously monitor the grid frequency to obtain the grid frequency deviation information, and transmit the detected frequency data to the system to trigger the corresponding frequency modulation response;

[0152] The parameter acquisition module includes temperature, pressure, rotation speed, and power sensors, and is used to collect the operating parameters of the thermal power generation unit module and the molten salt energy storage module in real time;

[0153] The frequency modulation control module includes a fuzzy adaptive PID controller and an algorithm processor, which trigger corresponding frequency modulation operations according to different levels of frequency deviation, and are used to analyze data and adjust the output parameters of the thermal power generation unit module and the molten salt energy storage module;

[0154] The thermal power generation unit module is used to quickly respond to high-frequency frequency fluctuations. When the grid frequency undergoes instantaneous fluctuations, it quickly adjusts the output power to help the grid return to a stable state;

[0155] The molten salt energy storage module is used to handle low-frequency fluctuations and long-term frequency stability, provide continuous power output, and at the same time provide additional power support for the system through a thermoelectric conversion device when the grid frequency fluctuates;

[0156] The cogeneration module is connected to the molten salt energy storage module, and can adjust the heating output according to the situation of grid frequency fluctuations, and link the heating demand with the power output of the energy storage system through feedforward control;

[0157] The data recording and feedback module is used to record and store various data of the system during the frequency modulation process, including frequency fluctuations and the output conditions of the thermal power generation unit module and the molten salt energy storage module;

[0158] The fault detection and standby module is used to monitor the status of the entire system in real time. When it detects that the frequency fluctuation in the system exceeds the safe range or a certain module fails, it immediately starts the standby energy storage device;

[0159] The reset and recovery module is responsible for gradually exiting the frequency modulation mode, returning the system to the initial monitoring state, setting all modules to the standby state, and gradually restoring the heat of the molten salt energy storage module to the normal level to prepare for the next frequency modulation demand.

[0160] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. For those skilled in the art, there are various changes and modifications to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A new frequency modulation method for molten salt energy storage coupled with thermal power units, characterized in that: The following steps are involved: Step S1, monitoring the grid frequency through a frequency detection module and classifying the frequency according to the deviation amplitude; Step S2, collecting data through the parameter collection module, performing denoising, and performing primary frequency modulation using the frequency modulation control module; Step S3, decomposing the frequency signal by wavelet packet decomposition method, and the thermal power unit module and the molten salt energy storage module work together to perform secondary frequency modulation; Step S4, using the ensemble empirical mode decomposition method to separate high and low frequency components, the thermal power unit module and the molten salt energy storage module work together, and the cogeneration module and the molten salt energy storage module coordinate and adjust to perform three-level frequency modulation in response to large fluctuations; Step S5, recording the frequency fluctuation and output status through the data recording and feedback module, and adjusting the parameters according to the feedback data; Step S6, monitor the status of each module in real time, and immediately start the fault detection and backup module if the fluctuation exceeds the safety range or the fault occurs; Step S7, through the reset and recovery module, after the frequency is stabilized, the system gradually exits the frequency modulation mode and returns to the initial monitoring state, and all modules enter the standby state; Wherein step S2 also includes the following sub-steps: S2-1, obtaining temperature, pressure, speed and power parameters through the temperature sensor, pressure sensor, speed sensor and power sensor in the parameter acquisition module; S2-2, the double threshold method is combined with the sliding average filter to remove noise, and the three sigma rule is combined with the local anomaly factor algorithm to detect outliers, identify and remove or correct abnormal data points, as shown in formula (1) to formula (4): Formula (1) Formula (2) Formula (3) （4） in, is a data point in the original data sequence, is the data point processed by the double threshold method, , are the upper and lower thresholds, is invalid data; is the smoothed data value after sliding average filtering, The size of the sliding window, i is the relative position of the data point, The window used to initialize the filter, is the data point processed by the double threshold method, the data point at time ti; is the mean of the data, is the standard deviation, is a data point in the data set; is the local outlier factor of point p, k is the number of neighbors, is the set of k neighbors of point p, o is a neighbor of point p, is the local reachability density of point p, is the local reachability density of point o; S2-3, through the frequency modulation control module, uses the fuzzy adaptive PID algorithm to dynamically adjust according to different frequency deviation conditions, as shown in formula (5): Formula (5) in, is the error value, It is the parameter that the fuzzy controller automatically adjusts according to the real-time frequency error; S2-4, return to monitoring mode after frequency adjustment is completed.

2. According to claim 1, a novel frequency modulation method for molten salt energy storage coupled with a thermal power unit is characterized in that: Wherein step S1 also includes the following sub-steps: S1-1, through the frequency detection module, uses the synchronized phasor measurement device to monitor the changes of voltage and current in real time, captures the slight frequency fluctuations, and continuously detects the frequency fluctuations of the power grid; S1-2, frequency levels are divided according to the frequency deviation amplitude, and the fluctuation is divided into three levels, as follows: Level 1: Mild frequency fluctuation, with deviation within 0.1Hz; Level 2: Moderate frequency fluctuation, with a deviation between 0.1-0.2 Hz; Level 3: High frequency fluctuation, deviation exceeds 0.2Hz.

3. According to claim 1, a novel frequency modulation method for molten salt energy storage coupled with a thermal power unit is characterized in that: Wherein step S3 also includes the following sub-steps: S3-1, according to the frequency fluctuation signal, the frequency regulation demand is allocated to the thermal power unit module and the molten salt energy storage module. The thermal power unit module is responsible for preliminary regulation, and the molten salt energy storage module is responsible for frequency stability; S3-2, using wavelet packet decomposition technology to decompose the frequency modulation signal into high-frequency and low-frequency components, the high-frequency part is responded by the thermal power unit module, and the low-frequency part is borne by the molten salt energy storage module, as shown in formula (6)-formula (7): Formula (6) Formula (7) Among them, the number of decomposition layers is n, the wavelet packet decomposition coefficient is d, the frequency band node number is j, the low-pass filter coefficient is b, the high-pass filter coefficient is a, the low-pass filter coefficient is l, and the frequency band number is k; S3-3, the thermal power unit module undertakes the task of rapid frequency regulation to cope with instantaneous frequency fluctuations; the molten salt energy storage module provides support for low-frequency components; S3-4, monitor the frequency recovery in real time and adjust the output of the molten salt energy storage module according to the frequency change.

4. According to claim 1, a novel frequency modulation method for molten salt energy storage coupled with a thermal power unit is characterized in that: Wherein step S4 also includes the following sub-steps: S4-1, through the ensemble empirical mode decomposition method, the load command is decomposed into high-frequency signals and low-frequency signals, as shown in formula (8) to formula (10): Formula (8) Formula (9) Formula (10) in, is the signal to be decomposed, is the original signal The natural mode components of order, To decompose the remainder, is the decomposition order; Represents a high frequency signal, represents low-frequency signal, d represents wavelet packet decomposition coefficient; Formula (9) is the order less than or equal to The sum of the natural modal components of is the higher frequency part; Formula (10) is the order greater than The sum of the natural modal components and the remainder is the lower frequency part; S4-2, the thermal power unit module and the molten salt energy storage module work together, the molten salt energy storage module provides long-term output to cope with continuous low-frequency fluctuations, and the thermal power unit module responds to short-term high-frequency fluctuations; S4-3, when the grid frequency continues to fluctuate significantly, the heat energy of the molten salt energy storage module is transferred to the grid through the thermoelectric conversion device; S4-4, the molten salt energy storage module adjusts the heat output through the cogeneration module, and uses the feedforward control strategy to link the demand of the heating end with the output of the molten salt energy storage module.

5. According to claim 1, a novel frequency modulation method for molten salt energy storage coupled with a thermal power unit is characterized in that: Wherein, in step S5, the following sub-steps are also included: S5-1, through the data recording and feedback module, the frequency fluctuation and the output data of the thermal power unit module and the molten salt energy storage module are recorded in real time during the frequency modulation process; S5-2, based on real-time monitoring data, using data feedback mechanism and intelligent control algorithm, adjust the output parameters of the thermal power unit module and the molten salt energy storage module.

6. A novel frequency modulation method for molten salt energy storage coupled with thermal power generation units according to claim 1, characterized in that: Wherein, in step S6, the following sub-steps are also included: S6-1, through the fault detection and backup module, real-time monitoring of the operating status of the thermal power unit module and the molten salt energy storage module, to determine whether there is an abnormal operating status; S6-2, using the over-limit judgment mechanism, starts the backup energy storage device when it is detected that the frequency fluctuation meets the third-level standard or the equipment fails.

7. A novel frequency modulation method for molten salt energy storage coupled with thermal power generation units according to claim 1, characterized in that: Wherein, in step S7, the following sub-steps are also included: S7-1, after the frequency is restored to a stable state through the reset and recovery module, a phased exit method is adopted to gradually reduce the output of the molten salt energy storage module and the thermal power unit module and return to the initial monitoring mode; S7-2, after detecting that the data remains within the normal range for a period of time, triggers the automatic reset mechanism in the reset and recovery module, so that each module returns to the standby state after the frequency modulation task is completed.

8. A novel frequency modulation system for molten salt energy storage coupled with thermal power units, applied to the frequency modulation method according to any one of claims 1 to 7, characterized in that: include: Frequency detection module, parameter acquisition module, frequency modulation control module, thermal power unit module, molten salt energy storage module, combined heat and power module, data recording and feedback module, fault detection and backup module, reset and recovery module; The frequency detection module is used to continuously monitor the grid frequency to obtain grid frequency deviation information, and transmit the detected frequency data to the system to trigger the corresponding frequency modulation response; The parameter acquisition module includes temperature, pressure, speed and power sensors, which are used to collect the operating parameters of the thermal power unit module and the molten salt energy storage module in real time; The frequency modulation control module includes a fuzzy adaptive PID controller and an algorithm processor, which triggers corresponding frequency modulation operations according to different levels of frequency deviation, and is used to analyze data and adjust the output parameters of the thermal power unit module and the molten salt energy storage module; The thermal power unit module is used to quickly respond to high-frequency frequency fluctuations. When the grid frequency fluctuates instantaneously, the output power is quickly adjusted to help the grid return to a stable state; The molten salt energy storage module is used to handle low-frequency fluctuations and long-term frequency stability, provide continuous power output, and provide additional power support to the system through thermoelectric conversion equipment when the grid frequency fluctuates; The cogeneration module is connected to the molten salt energy storage module, and can adjust the heat output according to the fluctuation of the power grid frequency, and link the heat demand with the power output of the energy storage system through feedforward control; The data recording and feedback module is used to record and store various data of the system during the frequency modulation process, including frequency fluctuations, output conditions of the thermal power unit module and the molten salt energy storage module; The fault detection and backup module is used to monitor the status of the entire system in real time. When it is detected that the frequency fluctuation in the system exceeds the safety range or a module fails, the backup energy storage device is immediately started; The reset and recovery module is responsible for gradually exiting the frequency modulation mode, returning the system to the initial monitoring state, setting all modules to standby state, and gradually restoring the heat of the molten salt energy storage module to normal levels in preparation for the next frequency modulation demand.

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