Method and device for preventing inverter harmonic waves from influencing operation of electric energy meter

Abstract

The invention discloses a method and device for preventing inverter harmonic waves from affecting operation of an electric energy meter, and the method comprises the following steps: a harmonic attenuation device is installed on an inverter line bus, and the harmonic attenuation device comprises an LC resonance circuit and a control circuit; dynamically matching the winding inductor and the safety capacitor based on the harmonic frequency spectrum characteristic of the inverter; a temperature sensing module is integrated on the body of each power resistor branch; the MCU microcontroller judges whether to trigger power resistor branch switching or not based on the temperature data and a preset temperature control strategy; after a relay switching action is triggered, a dynamic compensation strategy is generated to dynamically adjust inductance, capacitance and resistance topology so as to realize frequency stabilization and impedance matching; and executing closed-loop feedback optimization and health assessment based on the harmonic suppression effect after dynamic compensation and the system operation state. The invention has the following advantages and effects: the dynamic tracking of the LC resonant frequency on the harmonic dominant frequency is realized, and the thermal runaway problem of the harmonic energy absorption unit is synchronously solved.

Description

Technical Field

[0001] The present invention relates to the field of electrical engineering, and in particular to a method and device for preventing inverter harmonics from affecting the operation of an electric energy meter. Background Art

[0002] With the increasing popularity of renewable energy power generation systems (such as photovoltaic and wind power), inverters are widely used as core power conversion devices. However, during operation, inverters generate high-frequency harmonics. When these harmonics are transmitted through the grid power lines to the energy meter, they interfere with the normal operation of the sampling circuit, resulting in significant increase in energy measurement errors.

[0003] In existing technologies, fixed-parameter LC filters are typically used to suppress harmonics, but their resonant frequency cannot adaptively track changes in the harmonic main frequency. For example, when the inverter load fluctuates or the grid impedance changes, the harmonic spectrum characteristics shift. The fixed LC filter detunes, resulting in a decrease in suppression efficiency. However, residual harmonics can still interfere with the current / voltage sampling module of the energy meter through capacitive coupling or electromagnetic induction. Furthermore, the harmonic energy absorption units in traditional solutions, such as power resistors, are prone to overheating and failure due to continuous operation, and the lack of a multi-channel redundant switching mechanism further reduces system reliability.

[0004] Therefore, how to achieve dynamic tracking of the LC resonant frequency to the harmonic main frequency and simultaneously solve the thermal runaway problem of the harmonic energy absorption unit has become the core technical challenge in suppressing the impact of inverter harmonics on the operation of the electricity meter. Summary of the Invention

[0005] The purpose of the present invention is to provide a method and device for preventing inverter harmonics from affecting the operation of an electric energy meter, so as to solve the problems raised in the background technology.

[0006] The above technical objectives of the present invention are achieved through the following technical solutions:

[0007] The present invention provides a method for preventing inverter harmonics from affecting the operation of an electric energy meter, comprising the following steps:

[0008] S100: Install a harmonic attenuation device on the inverter line bus, the harmonic attenuation device comprising an LC resonant circuit and a control circuit; the LC resonant circuit comprises a winding inductor, a safety capacitor, and two parallel power resistor branches, and is directly connected to the grid power line, with a pressure-sensitive module provided in parallel on the grid power line; the control circuit comprises an MCU microcontroller;

[0009] S200, based on the harmonic spectrum characteristics of the inverter, dynamically matching the inductance value of the winding inductor and the capacitance value of the safety capacitor, so that the resonant frequency of the LC resonant circuit adaptively tracks the main harmonic frequency, and achieving harmonic energy absorption through the heat loss of the power resistor;

[0010] S300, integrates a temperature sensor module on the body of each power resistor branch to collect the operating temperature of each power resistor in real time and feeds the temperature data back to the MCU microcontroller;

[0011] S400, the MCU microcontroller determines whether to trigger power resistor branch switching based on the temperature data and a preset temperature control strategy; when it is detected that the temperature of a power resistor branch exceeds a safety threshold, the MCU microcontroller switches to another power resistor branch through a relay to achieve alternating switching of the two power resistor branches;

[0012] S500, after the relay switching action is triggered, generates a dynamic compensation strategy to dynamically adjust the inductance, capacitance and resistance topology to achieve frequency stability and impedance matching;

[0013] S600: Based on the harmonic suppression effect after dynamic compensation and the system operating status, perform closed-loop feedback optimization and health assessment.

[0014] By adopting the above technical solution, a LC resonant circuit is combined with two parallel power resistor branches to achieve layered processing of harmonics of different frequencies. The LC resonant circuit accurately filters out harmonic components of specific frequencies, while the power resistor branches absorb the remaining harmonic energy through heat loss, forming a complementary mechanism that effectively reduces the harmonic content in the power grid and ensures the signal purity of the electricity meter sampling circuit. Based on the real-time harmonic spectrum characteristics, the inductor and capacitor parameters are dynamically adjusted to ensure that the LC resonant frequency always follows the changes of the harmonic main frequency. This overcomes the detuning problem of traditional fixed filters caused by grid load fluctuations or environmental factors and improves the stability of harmonic suppression under complex operating conditions. By alternating the two power resistor branches, the risk of overheating caused by long-term operation in a single branch is avoided, the heat loss pressure is evenly distributed, and the service life of the power resistors is significantly extended, while ensuring the continuity and safety of the harmonic energy absorption process. In combination with a dynamic compensation strategy and a health assessment module, the system status is monitored in real time and parameters are adjusted, effectively offsetting the effects of component aging, temperature drift, or grid impedance changes, maintaining the long-term stability of harmonic suppression performance and reducing the need for manual intervention.

[0015] Further configuration is that the S200 specifically includes the following steps:

[0016] S210, installing a high-frequency current sensor and a voltage sampling circuit at the input and output ends of the power line of the power grid, respectively, collecting harmonic current signals in the power line of the power grid through the high-frequency current sensor, and synchronously obtaining harmonic voltage waveforms through the voltage sampling circuit, then transmitting the harmonic current signals and voltage waveforms to a signal conditioning module for filtering, amplification, and analog-to-digital conversion to generate digitized harmonic spectrum data;

[0017] The harmonic spectrum data is stored in the buffer area of ​​the MCU microcontroller in segments according to a preset time window, and marked with a timestamp and grid load status;

[0018] S220, extracting the latest harmonic spectrum data from the cache area of ​​the MCU microcontroller, extracting the main harmonic frequency and its amplitude ratio through a fast Fourier transform algorithm, and calculating the energy weight value corresponding to the main harmonic frequency;

[0019] Based on the main harmonic frequency and harmonic energy weight values, calling a resonant frequency optimization model to determine a target resonant frequency;

[0020] According to the target resonant frequency and the nominal values ​​of the current winding inductance and safety capacitor, combined with the energy weight value, reversely calculate the required inductance adjustment amount and capacitance adjustment amount, wherein the higher the energy weight value, the higher the calculation priority of the corresponding inductance adjustment amount and capacitance adjustment amount;

[0021] The inductance adjustment amount and the capacitance adjustment amount are encoded into the inductance-capacitance adjustment instruction and sent to the parameter adjustment interface integrated in the MCU microcontroller through the SPI communication protocol. Then, the equivalent value of the winding inductance and the safety capacitance is adjusted in real time through the parameter adjustment circuit composed of an adjustable inductor and an adjustable capacitor.

[0022] By adopting the above technical solution, high-frequency sensors are deployed at the input and output ends of the power grid to achieve synchronous capture and digital processing of harmonic current and voltage waveforms, ensure the integrity and real-time performance of spectrum analysis, and provide a reliable data basis for dynamic frequency matching; the main harmonic frequency is quickly extracted from the spectrum data through the fast Fourier transform algorithm, and the energy weight value is calculated based on the amplitude ratio to accurately quantify the impact of each harmonic component on the electricity meter measurement, and preferentially suppress the most harmful harmonic frequency band; through the coordinated adjustment of the adjustable inductor and adjustable capacitor, the synchronous optimization of the inductance and capacitance values ​​is achieved, ensuring that the resonant frequency accurately matches the target value, avoiding the resonance point offset or suppression efficiency drop caused by the adjustment of a single parameter.

[0023] A further configuration is to adjust the equivalent values ​​of the winding inductance and the safety capacitance in real time through a parameter adjustment circuit composed of an adjustable inductor and an adjustable capacitor, including:

[0024] The adjustable inductor receives the inductance adjustment value instruction from the parameter adjustment interface, drives the magnetic core displacement through the stepper motor, changes the effective number of turns of the inductor coil, and makes the equivalent value of the winding inductance match the target inductance;

[0025] The adjustable capacitor receives the capacitance adjustment instruction from the parameter adjustment interface and dynamically adjusts the equivalent capacitance of the safety capacitor by adjusting the bias voltage of the varactor diode array;

[0026] After the adjustment is completed, the real-time resonant frequency of the LC resonant circuit is verified through an impedance analyzer feedback loop, and if the deviation from the target resonant frequency exceeds a preset tolerance, a secondary calibration is triggered;

[0027] The calibrated inductance value, capacitance value and energy weight value are updated to the parameter database of the MCU microcontroller and used as the benchmark reference value for subsequent dynamic matching.

[0028] By adopting the above technical solution, the magnetic core displacement is driven by a stepper motor, and the effective number of turns of the inductor coil is linearly changed, thereby achieving high-precision continuous adjustment of the inductance, avoiding instantaneous current shocks or resonant frequency jumps caused by traditional tap switching, and improving system stability; the bias voltage of the varactor diode array is used to adjust the equivalent capacitance value, thereby achieving stepless and smooth adjustment of the capacitance value, with fast response speed and no mechanical wear, adapting to the rapid changes of high-frequency harmonics and extending the service life of the components; the resonant frequency is verified in real time by an impedance analyzer, and secondary calibration is triggered for deviations that exceed the limit, ensuring that the adjustment results of the inductance and capacitance parameters always meet the target requirements, eliminating errors caused by nonlinear characteristics of the components or environmental interference; the calibrated parameters and energy weight values ​​are stored in a database to form a historical reference benchmark, optimize the decision-making efficiency of subsequent parameter adjustments, reduce repeated calculation resource consumption, and improve the overall response speed of the system.

[0029] Further configuration is that the S400 specifically includes the following steps:

[0030] S410: Setting a dynamic temperature threshold for each power resistor branch; specifically, including:

[0031] Extracting historical temperature data from the parameter database of the MCU microcontroller, including the peak temperature, average temperature rise rate and continuous working time of the power resistor;

[0032] The current ambient temperature value is obtained in real time through the ambient temperature sensor, and the grid load current fluctuation rate is monitored in real time through the high-frequency current sensor;

[0033] Then, the temperature threshold is dynamically calculated, and the calculated dynamic temperature threshold is associated with the corresponding power resistor number, and stored in the temperature control strategy configuration table of the MCU microcontroller;

[0034] S420: Introducing a temperature hysteresis control algorithm during the switching process; specifically, including:

[0035] Setting a hysteresis temperature range for each power resistor branch based on the temperature threshold;

[0036] When the real-time temperature of a power resistor branch exceeds the hysteresis temperature range for the first time, it is marked as an overheat warning state and the switching countdown is started;

[0037] If the real-time temperature falls back to the hysteresis temperature range during the countdown period, the warning is cancelled; otherwise, the relay switching action is triggered;

[0038] After the switching is completed, the hysteresis bandwidth of the hysteresis temperature range is dynamically modified according to the load fluctuation rate.

[0039] By adopting the above technical solution, historical temperature data, ambient temperature, load current fluctuation rate and component working status are comprehensively considered to dynamically generate adaptive temperature thresholds, avoid over-protection or under-protection problems caused by single threshold setting, and improve the accuracy of the temperature control strategy; by setting the hysteresis temperature range and combining it with the countdown mechanism, instantaneous temperature fluctuations or noise interference are effectively filtered, and the switching action is triggered only in case of continuous overheating, reducing unnecessary frequent operation of the relay, mechanical loss and the probability of system malfunction; the hysteresis range width is corrected in real time according to the load current fluctuation rate, the tolerance range is expanded in high-fluctuation scenarios to enhance anti-interference ability, and the range is narrowed in stable working conditions to improve response sensitivity, thereby achieving flexible optimization of the temperature control strategy; the dynamic temperature threshold is bound to the branch number and stored, supporting the MCU microcontroller to independently analyze the health status and predict faults of each power resistor, facilitating rapid location of abnormal branches and execution of targeted maintenance.

[0040] Further configuration is that the S500 specifically includes the following steps:

[0041] S510: After the relay switching action is triggered, based on the switched power resistor number and the corresponding thermal inertia parameter, obtaining the equivalent impedance change of the power resistor in real time; wherein the thermal inertia parameter includes the material specific heat capacity, heat dissipation coefficient and current ambient temperature of the power resistor, and calculating the equivalent impedance change;

[0042] S520: Invoking a multi-parameter collaborative optimization model through the MCU microcontroller, combining the equivalent impedance change, the real-time harmonic spectrum data, and the historical attenuation effect records in the parameter database to generate a dynamic compensation strategy;

[0043] S530: Synchronously adjusting the core displacement of the adjustable inductor, the bias voltage of the adjustable capacitor, and the parallel topology of the power resistance branch according to the dynamic compensation strategy; including:

[0044] If the switching of the power resistance branch causes a parallel impedance mismatch of the power resistance branch, the parallel configuration of the power resistance branch is dynamically adjusted through a topology reconstruction module.

[0045] By adopting the above technical solution, combining the thermal properties of materials and environmental parameters, a thermal-impedance correlation model of the power resistor is established, and the equivalent impedance offset caused by temperature changes is calculated in real time, providing high-precision input data for dynamic compensation, avoiding the failure of resonance suppression due to impedance mismatch; balancing the resonant frequency stability and impedance matching requirements through the objective function, dynamically adjusting the optimization weight factor, adapting to the priority differences in different harmonic scenarios, and achieving the global optimal configuration of system performance; when the power resistor branch switching causes impedance mismatch, by adjusting the inductance, capacitance parameters and virtual impedance compensation, the system equivalent impedance is quickly reconstructed, the harmonic suppression function is restored, and the impact of transient disturbances in the power grid on the electricity meter is minimized; ensuring that the adjustment process of the inductance and capacitance parameters is strictly synchronized in timing and amplitude, avoiding instantaneous offset of the resonance point or fluctuation of suppression performance due to asynchronous parameter changes, and maintaining the dynamic stability of the system.

[0046] Further, in S530, if the switching of the power resistor branch causes a parallel impedance mismatch of the power resistor branch, the parallel configuration of the power resistor branch is dynamically adjusted by the topology reconstruction module, including:

[0047] S530.1. Deploy current sensors and voltage sensors at the input and output ends of the two power resistor branches, respectively, to monitor the current and voltage values ​​of each branch in real time. Calculate the real-time impedance value of each power resistor branch and upload the data to the MCU.

[0048] S530.2. The MCU microcontroller determines the impedance mismatch type based on a preset impedance matching threshold:

[0049] If the real-time impedance value of a power resistor branch is less than the minimum value of the impedance matching threshold, and the impedance of the other power resistor branch is normal, it is determined to be a first-type single-channel impedance mismatch;

[0050] If the real-time impedance value of a power resistor branch is greater than the maximum value of the impedance matching threshold, and the impedance of the other power resistor branch is normal, it is determined to be a second-type single-channel impedance mismatch;

[0051] If the real-time impedance values ​​of the two power resistance branches are both less than the minimum value of the impedance matching threshold, it is determined to be a first-type dual-path impedance mismatch;

[0052] If the real-time impedance values ​​of the two power resistance branches are both greater than the maximum value of the impedance matching threshold, it is determined to be a second type of dual-path impedance mismatch;

[0053] If the real-time impedance value of one power resistor branch is less than the minimum value of the impedance matching threshold, and the real-time impedance value of the other power resistor branch is greater than the maximum value of the impedance matching threshold, it is determined to be a third type of dual-path impedance mismatch;

[0054] S530.3. Trigger the following reconstruction actions based on the impedance mismatch type:

[0055] If the impedance mismatch type is the first type of single-path impedance mismatch, the faulty power resistance branch is disconnected and the normal power resistance branch is kept to work independently;

[0056] If the impedance mismatch type is the second type of single-path impedance mismatch, connect a spare redundant power resistor branch or adjust the parameters of the normal power resistor branch;

[0057] If the impedance mismatch type is the first type of dual-path impedance mismatch, all impedance branches are disconnected and load reduction protection is activated;

[0058] If the impedance mismatch type is the second type of dual-path impedance mismatch, try resetting the relay or enabling virtual impedance compensation;

[0059] If the impedance mismatch type is the third type of dual-path impedance mismatch, the short-circuited / overloaded impedance branch is processed first, and then the compensation strategy is implemented for the open-circuited / abnormal resistance impedance branch;

[0060] S530.4. In the single power resistance branch operating mode, adjust the series resonance parameters using the adjustable inductor and the adjustable capacitor:

[0061] S530.5. If both power resistance branches are mismatched and cannot be restored, the inverter output power is forcibly reduced by the MCU microcontroller and an audible and visual alarm is triggered.

[0062] By adopting the above technical solution, the mismatch type is divided into multiple dimensions through preset impedance matching thresholds, and independent response strategies are designed for different fault modes such as short circuit, open circuit, and overload, thereby improving the accuracy and efficiency of fault handling; the short-circuited or overloaded branch is quickly physically isolated and switched to the normal branch for independent operation, minimizing the system function interruption time and ensuring the continuity of harmonic suppression; when the branch is open or the resistance value is abnormal, virtual impedance is generated through software algorithms to compensate for the actual impedance loss, avoiding delays in hardware topology adjustment and maintaining the stability of the overall system impedance and harmonic absorption efficiency; for the simultaneous occurrence of short-circuit and open-circuit composite faults, the short-circuited branch that may cause equipment damage or safety risks is prioritized, and then the open-circuit anomaly is gradually repaired to ensure that the fault handling process complies with safety regulations and operating logic; when both branches are unavailable, the inverter output power is forcibly limited to a safe range and an alarm is triggered to prevent the accumulation of harmonic energy from causing equipment overheating or grid voltage collapse, thereby ensuring the safety of the system and personnel.

[0063] Further configuration is that the S600 specifically includes the following steps:

[0064] S610: deploying a harmonic suppression effect evaluation model in the MCU microcontroller, collecting the total harmonic distortion of the voltage of the power line of the power grid, the benchmark total harmonic distortion, and the measured value rate of the measurement error of the electric energy meter in real time, and calculating a comprehensive suppression effectiveness index, which is then stored in the historical performance record table in the parameter database;

[0065] S620: Based on the comprehensive suppression effectiveness index and the historical performance record table, perform dynamic parameter recalibration:

[0066] If the comprehensive suppression effectiveness index is lower than a preset threshold, a parameter backtracking analysis is triggered; the current inductance value, capacitance value, and power resistance configuration parameters are extracted from the parameter database, compared with the historical optimal parameter combination, and a parameter deviation report is generated;

[0067] recalculating the target resonant frequency through the resonant frequency optimization model according to the parameter deviation report, and updating the dynamic compensation strategy through the multi-parameter collaborative optimization model;

[0068] S630: Perform system health status diagnosis, including:

[0069] The temperature sensor module collects real-time temperature data of the power resistor, calculates the average operating temperature based on the time series, and obtains the actual number of relay switching times through the relay drive record of the MCU microcontroller; and calculates the health score by combining the fault log of the MCU microcontroller, the maximum allowable operating temperature of the power resistor, and the rated life of the relay;

[0070] S640: If the health score is lower than a preset safety threshold, a maintenance warning signal is triggered and a maintenance recommendation list is generated. The maintenance recommendation list includes: power resistor life warning, adjustable inductor core wear reminder, safety capacitor capacitance drift warning, and varistor module aging detection recommendation. At the same time, the MCU microcontroller automatically reduces the grid load current to a safe range and locks the parameter adjustment interface to prevent overload operation.

[0071] S650, upload the optimized parameter configuration, health score and maintenance recommendation list to the cloud management platform through the communication module, and simultaneously update the local parameter database.

[0072] By adopting the above technical solution, the suppression effect is quantified through the dual indicators of voltage harmonic distortion and electricity meter measurement error, which comprehensively reflects the system performance, avoids the one-sidedness of single indicator evaluation, and supports more scientific optimization decisions; when performance degradation is detected, the historical optimal parameters are automatically traced back and the target configuration is recalculated to eliminate the impact of component aging or environmental drift, so that the system performance is restored to a state close to the initial state, and the effective life of the equipment is extended; by quantifying key indicators such as power resistor temperature rise and relay switching times, the remaining life of the components and the potential failure risk are predicted, providing data support for preventive maintenance and reducing the probability of sudden failure downtime; based on the health score, a list of recommendations covering multiple dimensions such as component replacement, parameter calibration, and mechanical maintenance is automatically generated to guide operation and maintenance personnel in targeted operations, reduce blind inspections and resource waste, and improve maintenance efficiency; local data is uploaded to the cloud management platform through encrypted communication, and historical data is analyzed using big data and machine learning to generate long-term optimization strategies and feedback to the local system to achieve continuous improvement in suppression efficiency.

[0073] It is further configured that the generation of the maintenance suggestion list in S640 further includes the following steps:

[0074] For power resistor life warning, the remaining life percentage is dynamically calculated based on the ratio of cumulative working time to rated life, and the failure time is predicted in combination with the temperature rise curve;

[0075] For adjustable inductor core wear, the degree of core mechanical loss is assessed by measuring the deviation between the stepper motor's drive current fluctuation rate and the core displacement feedback signal.

[0076] For the capacitance drift of safety capacitors, the real-time capacitance measurement data of the impedance analyzer feedback loop is compared with the nominal value to generate a capacitance deviation alarm level;

[0077] For aging of the varistor module, the transient suppression response time and clamping voltage offset are collected to determine whether the varistor module needs to be replaced.

[0078] By adopting the above technical solution, the deviation between the stepper motor drive current and the displacement feedback signal is analyzed to indirectly evaluate the mechanical wear status of the magnetic core, avoiding the complex process of traditional disassembly and detection, and reducing maintenance costs and operational risks; the impedance analysis loop is used to continuously monitor the changes in capacitor capacitance, and the alarm level is divided according to the deviation amplitude. A graded response strategy is supported to ensure timely calibration or replacement when the capacitance is abnormal, thereby ensuring the stability of the resonant frequency; through the joint analysis of transient response time and clamping voltage offset, the aging degree of the pressure-sensitive module can be accurately judged, avoiding the misjudgment of a single parameter, and improving the reliability and accuracy of aging detection.

[0079] The present invention also provides a device for preventing inverter harmonics from affecting the operation of an electric energy meter, comprising a harmonic attenuation device installed on an inverter line bus; the harmonic attenuation device is composed of an LC resonant circuit and a control circuit;

[0080] The LC resonant circuit includes a winding inductor, a safety capacitor, and two parallel power resistors. The LC resonant circuit is directly connected to the power line of the power grid; a pressure sensitive module is arranged in parallel on the power line of the power grid;

[0081] The control circuit includes two temperature acquisition chips, a relay, and an MCU microcontroller; the two power resistors serve as two independent power resistance branches; the two temperature acquisition chips are respectively installed on the bodies of the two power resistors, for collecting their temperature signals in real time and transmitting them to the MCU microcontroller; the MCU microcontroller determines whether to switch the power resistance branch based on a preset temperature threshold, and triggers the switching action by controlling the relay to achieve alternating switching of the two power resistance branches.

[0082] In summary, the present invention has the following beneficial effects:

[0083] The LC resonant frequency is dynamically tracked to the main harmonic frequency, and the thermal runaway problem of the harmonic energy absorption unit is solved simultaneously. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] Figure 1 It is a schematic diagram of the main process of the embodiment;

[0085] Figure 2 2 is a flow chart of adjusting the equivalent values ​​of the winding inductance and the safety capacitance in real time by using a parameter adjustment circuit composed of an adjustable inductor and an adjustable capacitor in S220 of an embodiment;

[0086] Figure 3 Schematic diagram of the process of S500 in the embodiment;

[0087] Figure 4 A partial flow chart of S530 in the embodiment;

[0088] Figure 5 2 is a structural block diagram of the harmonic attenuation device in the embodiment. DETAILED DESCRIPTION

[0089] The present invention will be further described in detail below with reference to the accompanying drawings.

[0090] As attached Figures 1 to 5 As shown;

[0091] This embodiment discloses a method for preventing inverter harmonics from affecting the operation of an electric energy meter, comprising the following steps:

[0092] S100. Install a harmonic attenuation device on the inverter line bus. The harmonic attenuation device includes an LC resonant circuit and a control circuit. The LC resonant circuit is composed of a winding inductor, a safety capacitor, and two parallel power resistor branches, and is directly connected to the grid power line. A pressure-sensitive module is provided in parallel with the grid power line. The control circuit includes an MCU microcontroller.

[0093] S200, based on the harmonic spectrum characteristics of the inverter, dynamically matches the inductance value of the winding inductor and the capacitance value of the safety capacitor, so that the resonant frequency of the LC resonant circuit adaptively tracks the main harmonic frequency, and achieves harmonic energy absorption through the heat loss of the power resistor;

[0094] S300, integrates a temperature sensor module on the body of each power resistor branch to collect the operating temperature of each power resistor in real time and feeds the temperature data back to the MCU microcontroller;

[0095] The S400 and MCU microcontrollers determine whether to trigger power resistor branch switching based on temperature data and a preset temperature control strategy. When it detects that the temperature of a power resistor branch exceeds a safety threshold, it switches to another power resistor branch through a relay, achieving alternating switching of the two power resistor branches.

[0096] S500, after the relay switching action is triggered, generates a dynamic compensation strategy to dynamically adjust the inductance, capacitance and resistance topology to achieve frequency stability and impedance matching;

[0097] S600: Based on the harmonic suppression effect after dynamic compensation and the system operating status, perform closed-loop feedback optimization and health assessment.

[0098] In S100, the pressure-sensitive module can directly use a pressure-sensitive resistor;

[0099] A further optimization is that the varistor module is composed of a combination of multi-stage varistors and transient suppression diodes, and through topology optimization, the clamping voltage of the varistor module is matched with the rated voltage of the grid to achieve full-band suppression of lightning surges and short-time pulse groups.

[0100] Specifically, S200 includes the following steps:

[0101] S210. Install a high-frequency current sensor and a voltage sampling circuit at the input and output ends of the power line of the power grid, respectively. Collect harmonic current signals in the power line of the power grid through the high-frequency current sensor, and synchronously obtain harmonic voltage waveforms through the voltage sampling circuit. Then, transmit the harmonic current signal and voltage waveform to a signal conditioning module for filtering, amplification, and analog-to-digital conversion to generate digitized harmonic spectrum data.

[0102] The harmonic spectrum data is segmented and stored in the MCU microcontroller's buffer area according to the preset time window, and marked with the timestamp and grid load status;

[0103] S220, extracting the latest harmonic spectrum data from the cache area of ​​the MCU microcontroller, extracting the main harmonic frequency and its amplitude ratio using a fast Fourier transform algorithm, and calculating the energy weight value corresponding to the main harmonic frequency; the energy weight value is defined as W, and its value is obtained by dividing the amplitude ratio of the main harmonic by the total harmonic amplitude;

[0104] Based on the main harmonic frequency and harmonic energy weight values, a resonant frequency optimization model is called to determine the target resonant frequency;

[0105] The resonant frequency optimization model includes the following formulas:

[0106] f target =k·f base (1+α·W)

[0107] Among them, k is the frequency offset coefficient, α is the weight correction factor, and f target is the target resonant frequency, f base is the main harmonic frequency;

[0108] Based on the target resonant frequency and the nominal values ​​of the current winding inductance and safety capacitor, combined with the energy weight value, the required inductance adjustment and capacitance adjustment are reversely calculated. The higher the energy weight value, the higher the calculation priority of the corresponding inductance adjustment and capacitance adjustment.

[0109] The inductance adjustment amount and the capacitance adjustment amount are encoded into inductance-capacitance adjustment instructions and sent to the parameter adjustment interface integrated in the MCU microcontroller through the SPI communication protocol. Then, the equivalent values ​​of the winding inductance and safety capacitance are adjusted in real time through the parameter adjustment circuit composed of an adjustable inductor and an adjustable capacitor.

[0110] Specifically, the equivalent values ​​of the winding inductance and safety capacitance are adjusted in real time through a parameter adjustment circuit composed of an adjustable inductor and an adjustable capacitor, including:

[0111] The adjustable inductor receives the inductance adjustment value instruction from the parameter adjustment interface, drives the magnetic core displacement through the stepper motor, changes the effective number of turns of the inductor coil, and makes the equivalent value of the winding inductance match the target inductance;

[0112] The adjustable capacitor receives the capacitance adjustment instruction from the parameter adjustment interface and dynamically adjusts the equivalent capacitance of the safety capacitor by adjusting the bias voltage of the varactor diode array;

[0113] After the adjustment is completed, the real-time resonant frequency of the LC resonant circuit is verified through the impedance analyzer feedback loop. If the deviation from the target resonant frequency exceeds the preset tolerance, a secondary calibration is triggered;

[0114] The calibrated inductance value, capacitance value and energy weight value are updated to the parameter database of the MCU microcontroller and serve as the benchmark reference value for subsequent dynamic matching.

[0115] The calculation of the energy weight value further includes:

[0116] The amplitude ratio of the main harmonic frequency is normalized and mapped to the range of 0 to 1. Then, based on the normalized amplitude ratio and the preset electricity meter error sensitivity curve, the energy weight value is dynamically corrected to preferentially suppress the harmonic frequency band that has the greatest impact on the electricity meter measurement.

[0117] Example 1

[0118] Normalized amplitude ratio: The third harmonic amplitude is detected to account for 25%, and the normalized value is 0.25;

[0119] According to the error sensitivity curve of the electric energy meter, the third harmonic sensitivity coefficient is 0.8, and the corrected energy weight value is 0.2.

[0120] Specifically, S400 includes the following steps:

[0121] S410: Setting a dynamic temperature threshold for each power resistor branch; specifically, including:

[0122] Extract historical temperature data from the MCU microcontroller's parameter database, including the peak temperature, average temperature rise rate, and continuous working time of the power resistor;

[0123] The current ambient temperature value is obtained in real time through the ambient temperature sensor, and the grid load current fluctuation rate is monitored in real time through the high-frequency current sensor;

[0124] Then, the temperature threshold is dynamically calculated, and the calculated dynamic temperature threshold is associated with the corresponding power resistor number and stored in the temperature control strategy configuration table of the MCU microcontroller;

[0125] The formula for dynamically calculating the temperature threshold is as follows:

[0126] T th =T base +β1·ΔT hist +β2·|T env -T ref ∣+β3·δ+β4·r avg ·t op

[0127] Among them, T th is the temperature threshold; T base is the rated operating temperature of the power resistor; ΔT histThe peak temperature of the power resistor and T base The difference between env is the current ambient temperature; T ref is the ambient temperature reference value, the default value is 25℃; t op is the continuous working time; β1, β2, β3 and β4 are the corresponding weight coefficients optimized by experimental data;

[0128] S420: Introducing a temperature hysteresis control algorithm during the switching process; specifically, including:

[0129] Setting a hysteresis temperature range for each power resistor branch based on a temperature threshold;

[0130] When the real-time temperature of a power resistor branch exceeds the hysteresis temperature range [T th -ΔH,T th +ΔH], it is marked as an overheat warning state and the switching countdown is started; ΔH is the hysteresis bandwidth, which is calculated based on the thermal inertia coefficient of the power resistor;

[0131] If the real-time temperature falls back to the hysteresis temperature range during the countdown period, the warning is cancelled; otherwise, the relay switching action is triggered;

[0132] After the switching is completed, the hysteresis bandwidth of the hysteresis temperature range is dynamically modified according to the load fluctuation rate.

[0133] Specifically corrected by the following formula:

[0134] ΔH new =ΔH·(1+γ·δ / 100)

[0135] Where ΔH new is the corrected hysteresis bandwidth; δ is the grid load current fluctuation rate monitored in S410; γ is the adjustable sensitivity coefficient.

[0136] Specifically, S500 includes the following steps:

[0137] S510: After the relay switching action is triggered, based on the switched power resistor number and the corresponding thermal inertia parameter, obtain the equivalent impedance change of the power resistor in real time; wherein the thermal inertia parameter includes the material specific heat capacity, heat dissipation coefficient and current ambient temperature of the power resistor, and calculate the equivalent impedance change;

[0138] The equivalent impedance change is calculated using the following formula:

[0139] ΔR eq =R base ·(1+λ·(T current -T base ))

[0140] Where, ΔR eq is the equivalent impedance change, R base is the nominal resistance of the power resistor, λ is the material temperature coefficient, T current is the real-time temperature of the power resistor body, T base is the rated temperature;

[0141] S520, calling a multi-parameter collaborative optimization model through the MCU microcontroller, combining equivalent impedance change, real-time harmonic spectrum data, and historical attenuation effect records in the parameter database to generate a dynamic compensation strategy;

[0142] The multi-parameter collaborative optimization model includes the following objective functions:

[0143] Minimize(Δf 2 +η·ΔR eq 2 )

[0144] Wherein, Δf is the resonant frequency offset; η is the weight factor used to balance the priority between frequency offset compensation and impedance matching;

[0145] Example 2

[0146] Objective function: Minimize(Δf 2 +0.5·ΔR eq 2 );

[0147] If the resonant frequency shift Δf=2Hz and the impedance change ΔReq=1Ω, the optimization target value is 2 2 +0.5×1 2 =4.5.

[0148] S530, synchronously adjusting the core displacement of the adjustable inductor, the bias voltage of the adjustable capacitor, and the parallel topology of the power resistance branch according to the dynamic compensation strategy; including:

[0149] The stepper motor of the adjustable inductor drives the displacement of the magnetic core to make the inductance value meet the target impedance requirement; the bias voltage of the varactor diode array is adjusted to make the equivalent capacitance of the safety capacitor and the adjusted inductance value form a complementary resonance;

[0150] If the switching of the power resistance branch causes a parallel impedance mismatch of the power resistance branch, the parallel configuration of the power resistance branch is dynamically adjusted through a topology reconstruction module.

[0151] Specifically, in S530, if the switching of the power resistor branch causes a parallel impedance mismatch of the power resistor branch, the parallel configuration of the power resistor branch is dynamically adjusted by the topology reconstruction module, including:

[0152] S530.1. Deploy current sensors and voltage sensors at the input and output ends of the two power resistor branches, respectively, to monitor the current and voltage values ​​of each branch in real time. Calculate the real-time impedance value of each power resistor branch and upload the data to the MCU.

[0153] S530.2, the MCU microcontroller determines the impedance mismatch type based on the preset impedance matching threshold:

[0154] If the real-time impedance value of a power resistor branch is less than the minimum value of the impedance matching threshold, and the impedance of the other power resistor branch is normal, it is determined to be a first-type single-channel impedance mismatch;

[0155] If the real-time impedance value of a power resistor branch is greater than the maximum value of the impedance matching threshold, and the impedance of the other power resistor branch is normal, it is determined to be a second-type single-channel impedance mismatch;

[0156] If the real-time impedance values ​​of the two power resistor branches are both less than the minimum value of the impedance matching threshold, it is determined to be a first-class dual-path impedance mismatch; both the first-class single-path impedance mismatch and the first-class dual-path impedance mismatch are manifested as a short circuit or overload;

[0157] If the real-time impedance values ​​of the two power resistor branches are both greater than the maximum value of the impedance matching threshold, it is determined to be a second-type dual-path impedance mismatch; both the second-type single-path impedance mismatch and the second-type single-path impedance mismatch are manifested as an open circuit or abnormal resistance value;

[0158] If the real-time impedance value of one power resistor branch is less than the minimum value of the impedance matching threshold, and the real-time impedance value of the other power resistor branch is greater than the maximum value of the impedance matching threshold, it is determined to be a third type of dual-path impedance mismatch;

[0159] S530.3. Trigger the following reconstruction actions based on the impedance mismatch type:

[0160] If the impedance mismatch type is the first type of single-path impedance mismatch, the faulty power resistance branch is disconnected and the normal power resistance branch is kept to work independently;

[0161] If the impedance mismatch type is the second type of single-path impedance mismatch, connect a spare redundant power resistor branch or adjust the parameters of the normal power resistor branch;

[0162] If the impedance mismatch type is the first type of dual-path impedance mismatch, all impedance branches are disconnected and load reduction protection is activated;

[0163] If the impedance mismatch type is the second type of dual-path impedance mismatch, try resetting the relay or enabling virtual impedance compensation;

[0164] If the impedance mismatch type is the third type of dual-path impedance mismatch, the short-circuited / overloaded impedance branch is processed first, and then the compensation strategy is implemented for the open-circuited / abnormal resistance impedance branch;

[0165] S530.4. In the single power resistor branch operating mode, the series resonant parameters are adjusted using the adjustable inductor and adjustable capacitor:

[0166] Make the impedance of the remaining effective impedance branch satisfy:

[0167] Z total =Z remaining ·Z virtual / (Z remaining +Z virtual )

[0168] Among them, Z total is the total equivalent impedance of the system after adjustment, Z remaining is the impedance of the remaining effective impedance branch, Z virtual Compensation impedance generated for the virtual impedance module;

[0169] S530.5. If both power resistor branches are mismatched and cannot be restored, the inverter output power is forced to be reduced through the MCU microcontroller and an audible and visual alarm is triggered.

[0170] Specifically, S600 includes the following steps:

[0171] S610: Deploy a harmonic suppression effect evaluation model in the MCU microcontroller to collect the total harmonic distortion of the voltage of the power line of the power grid, the benchmark total harmonic distortion, and the measured value rate of the metering error of the electric energy meter in real time, calculate and obtain a comprehensive suppression effectiveness index, and then store it in a historical performance record table in the parameter database;

[0172] The harmonic suppression effect evaluation model calculates the comprehensive suppression effectiveness index using the following formula:

[0173] E=α·(1-THD current / THD base )+β·(1-ΔMeter current / ΔMeter threshold )

[0174] Among them, THD current Total harmonic distortion of voltage collected in real time; THD base It is the benchmark total harmonic distortion when the harmonic attenuation device is not connected; ΔMeter current ΔMeter is the measured value of the electric energy meter measurement error collected in real time; threshold is the preset maximum allowable measurement error threshold; α and β are weight coefficients;

[0175] S620: Based on the comprehensive suppression effectiveness index and the historical performance record table, perform dynamic recalibration of parameters:

[0176] If the comprehensive suppression effectiveness index falls below a preset threshold, a parameter backtracking analysis is triggered. The current inductance, capacitance, and power resistance configuration parameters are extracted from the parameter database, compared with the historical optimal parameter combination, and a parameter deviation report is generated.

[0177] Based on the parameter deviation report, the target resonant frequency is recalculated through the resonant frequency optimization model, and the dynamic compensation strategy is updated through the multi-parameter collaborative optimization model;

[0178] S630: Perform system health status diagnosis, including:

[0179] The temperature sensor module collects real-time temperature data from the power resistor and calculates the average operating temperature based on the time series. The actual number of relay switching times is obtained through the MCU microcontroller's relay driver records. The health score is calculated by combining the MCU microcontroller's fault log, the maximum allowable operating temperature of the power resistor, and the rated life of the relay.

[0180] The health score formula is:

[0181] H=γ·(T max -T avg ) / T max +δ·(N switch_max -N switch ) / N switch_max

[0182] Among them, H is the health score; T avg is the average operating temperature of the power resistor; T max is the maximum allowable operating temperature of the power resistor; N switch is the actual switching times of the relay; N switch_max is the rated life of the relay; γ and δ are weight factors.

[0183] If the health score falls below a preset safety threshold, the S640 triggers a maintenance warning signal and generates a maintenance recommendation list. This list includes warnings for power resistor life, adjustable inductor core wear, safety capacitor drift, and varistor module aging detection. The MCU automatically reduces the grid load current to a safe range and locks the parameter adjustment interface to prevent overload operation.

[0184] The S650 uploads the optimized parameter configuration, health score, and maintenance recommendation list to the cloud management platform via the communication module, and simultaneously updates the local parameter database. The communication module uses an encrypted transmission protocol to ensure data integrity and real-time performance. The cloud management platform analyzes historical data based on a machine learning algorithm, generates a long-term harmonic suppression strategy, and transmits it back to the local MCU, forming a closed-loop optimization link.

[0185] Specifically, generating the maintenance suggestion list in S640 further includes the following steps:

[0186] For power resistor life warning, the remaining life percentage is dynamically calculated based on the ratio of cumulative working time to rated life, and the failure time is predicted in combination with the temperature rise curve;

[0187] For adjustable inductor core wear, the degree of core mechanical loss is assessed by measuring the deviation between the stepper motor's drive current fluctuation rate and the core displacement feedback signal.

[0188] For capacitance drift of safety capacitors, the real-time capacitance measurement data from the impedance analyzer feedback loop is compared with the nominal value to generate a capacitance deviation alarm level.

[0189] For aging of the varistor module, the transient suppression response time and clamping voltage offset are collected to determine whether the varistor module needs to be replaced.

[0190] This embodiment also discloses a device for preventing inverter harmonics from affecting the operation of an electric energy meter;

[0191] The harmonic attenuation device comprises a harmonic attenuation device installed on the inverter line bus; the harmonic attenuation device comprises an LC resonant circuit and a control circuit;

[0192] The LC resonant circuit includes a winding inductor L1, a safety capacitor C1, and two parallel power resistors (R1 and R2). The LC resonant circuit is directly connected to the power line of the power grid; a pressure sensitive module RV1 is set in parallel on the power line of the power grid;

[0193] The control circuit includes two temperature acquisition chips, relay RE1, and MCU microcontroller; the two power resistors serve as two independent power resistance branches; the two temperature acquisition chips are installed on the bodies of the two power resistors, respectively, for real-time acquisition of their temperature signals and transmission to the MCU microcontroller; the MCU microcontroller determines whether to switch the power resistance branch based on the preset temperature threshold, and triggers the switching action by controlling the relay to realize alternating switching of the two power resistance branches.

[0194] Example 3

[0195] In the application, the inverter generates 5th harmonics (250Hz, amplitude accounting for 30%), causing the measurement error of the electricity meter to exceed the tolerance by up to 3.2%.

[0196] The harmonic attenuation device increases the 5th harmonic energy absorption rate to 85%, and reduces the voltage THD from 15% to 3.5%; at the same time, the electricity meter error is restored to within 0.5%; and the power resistor branch is switched every 30 minutes under the temperature control strategy, extending its service life by 20%.

[0197] Example 4

[0198] In S100, a harmonic attenuation device is installed on the power line of the power grid between the output terminal of the inverter and the electric energy meter. The device includes:

[0199] LC resonant circuit: It consists of a winding inductor with a rated inductance of 5mH, a safety capacitor with a rated capacitance of 10μF, and two parallel power resistor branches. Each power resistor branch has a resistance of 10Ω and a power of 500W.

[0200] Varistor module: A multi-stage varistor of model VDR-20D471K and a transient suppression diode of model SMBJ48CA are connected in series. The clamping voltage is set to the rated voltage of the grid 220V±10%.

[0201] Control circuit: The MCU microcontroller uses STM32F407, which integrates SPI communication interface, ADC sampling module and relay drive circuit.

[0202] The hardware connections are as follows:

[0203] The LC resonant circuit is directly connected in parallel with the power line of the power grid, and the pressure sensitive module is connected across the power lines LN;

[0204] The two power resistance branches are connected to the LC resonant circuit through the HF115F relay switch;

[0205] A high-frequency current sensor model LEM LA-55P is installed at the power line input, and a voltage sampling circuit with a voltage divider ratio of 1000:1 is connected to the ADC pin of the MCU.

[0206] In S200, the high-frequency current sensor captures the harmonic current signal at a sampling rate of 1MHz, and the voltage sampling circuit synchronously acquires the harmonic voltage waveform;

[0207] The signal conditioning module performs second-order Butterworth low-pass filtering, amplification, and 16-bit ADC conversion on the original signal to generate digital harmonic spectrum data.

[0208] The MCU microcontroller performs a 1024-point FFT operation on the spectrum data in the buffer area and extracts the harmonic components with an amplitude exceeding 15% as the main harmonic frequency;

[0209] The calculated energy weight value is 0.25 / 0.8=0.3125.

[0210] Call the resonant frequency optimization model, set parameters k = 1.05, α = 0.2, and calculate the target resonant frequency f target =161.72Hz;

[0211] Based on the target frequency, the LC parameters are reversed and the required inductance is calculated to be 4.8mH and the capacitance to be 9.6μF.

[0212] The adjustable inductor uses a stepper motor with a step angle of 1.8° to drive the magnetic core to move, changing the effective number of turns of the coil and adjusting the inductance value from 5mH to 4.8mH.

[0213] The adjustable capacitor adjusts the bias voltage through the varactor diode array to adjust the capacitance from 10μF to 9.6μF;

[0214] The impedance analyzer integrated into the MCU microcontroller verifies that the adjusted resonant frequency is 161.5 Hz with an error of less than 0.2%, meeting the preset tolerance.

[0215] In S400, historical data is read from the parameter database: the peak temperature of a power resistor is 85°C, the rated temperature T base The temperature is 75℃, the average temperature rise rate is 2℃ / min, and the continuous working time is 30min;

[0216] Real-time ambient temperature T env The temperature is 35℃ and the load current fluctuation rate δ is 15%;

[0217] Substitute into the formula to calculate the dynamic temperature threshold T th It is 84.5℃.

[0218] Set the hysteresis bandwidth ΔH to 5°C and the hysteresis range to [79.5°C, 89.5°C];

[0219] When the temperature of a certain power resistor reaches 80°C, a 10s countdown starts; if the temperature drops below 79°C within 10s, the warning is cancelled; otherwise, the relay switching action is triggered.

[0220] Example 5

[0221] Assume that after the power resistor branch is switched, the impedance of the first power resistor branch drops to 8Ω, which is lower than the minimum threshold value of 9Ω, and the impedance of the second power resistor branch remains at 10Ω.

[0222] The current sensor detects a current of 12.5A and a voltage of 100V in the first power resistor branch, and calculates the real-time impedance to be 8Ω, which is lower than the threshold of 9Ω. This is determined to be a first-class single-channel impedance mismatch.

[0223] Next, disconnect the first power resistor branch and keep the second power resistor branch to work independently;

[0224] Adjust the adjustable inductor to 5.2mH and the adjustable capacitor to 9.8μF to stabilize the LC resonant frequency at 160Hz; the virtual impedance module generates the compensation impedance Z virtual is 2Ω.

[0225] Example 6

[0226] Power resistor average temperature T avg At 78°C, the relay switches N times. switch 120 times, rated life N switch_max 10,000 times;

[0227] The calculated health score is 0.45, which is lower than the preset safety threshold of 0.6, triggering a maintenance warning.

[0228] Example 7

[0229] The generated maintenance recommendation list is as follows:

[0230] Remaining life of power resistor: 2000 cumulative working hours, remaining life 60%;

[0231] Adjustable inductor core wear: Stepper motor current fluctuation rate is 15%, lubrication maintenance is recommended;

[0232] Safety capacitor capacitance drift: measured 9.6μF, deviation 4%, alarm level is low.

[0233] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed. However, as long as such modifications are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A method for preventing inverter harmonics from affecting the operation of an electric energy meter, characterized in that: The following steps are included: S100: Install a harmonic attenuation device on the inverter line bus, the harmonic attenuation device comprising an LC resonant circuit and a control circuit; the LC resonant circuit comprises a winding inductor, a safety capacitor, and two parallel power resistor branches, and is directly connected to the grid power line, with a pressure-sensitive module provided in parallel on the grid power line; the control circuit comprises an MCU microcontroller; S200, based on the harmonic spectrum characteristics of the inverter, dynamically matching the inductance value of the winding inductor and the capacitance value of the safety capacitor, so that the resonant frequency of the LC resonant circuit adaptively tracks the main harmonic frequency, and achieving harmonic energy absorption through the heat loss of the power resistor; S300, integrates a temperature sensor module on the body of each power resistor branch to collect the operating temperature of each power resistor in real time and feeds the temperature data back to the MCU microcontroller; S400, the MCU microcontroller determines whether to trigger the switching of the power resistor branch based on the temperature data and the preset temperature control strategy; when it is detected that the temperature of a power resistor branch exceeds the safety threshold, the MCU microcontroller switches to the other power resistor branch through the relay to achieve alternating switching of the two power resistor branches; S500, after the relay switching action is triggered, generates a dynamic compensation strategy to dynamically adjust the inductance, capacitance and resistance topology to achieve frequency stability and impedance matching; S600: Based on the harmonic suppression effect after dynamic compensation and the system operating status, perform closed-loop feedback optimization and health assessment.

2. The method for preventing inverter harmonics from affecting the operation of an electric energy meter according to claim 1, characterized in that: The S200 specifically includes the following steps: S210, installing a high-frequency current sensor and a voltage sampling circuit at the input and output ends of the power line of the power grid, respectively, collecting harmonic current signals in the power line of the power grid through the high-frequency current sensor, and synchronously obtaining harmonic voltage waveforms through the voltage sampling circuit, then transmitting the harmonic current signals and voltage waveforms to a signal conditioning module for filtering, amplification, and analog-to-digital conversion to generate digitized harmonic spectrum data; The harmonic spectrum data is stored in the buffer area of ​​the MCU microcontroller in segments according to a preset time window, and marked with a timestamp and grid load status; S220, extracting the latest harmonic spectrum data from the cache area of ​​the MCU microcontroller, extracting the main harmonic frequency and its amplitude ratio through a fast Fourier transform algorithm, and calculating the energy weight value corresponding to the main harmonic frequency; Based on the main harmonic frequency and harmonic energy weight values, calling a resonant frequency optimization model to determine a target resonant frequency; According to the target resonant frequency and the nominal values ​​of the current winding inductance and safety capacitor, combined with the energy weight value, reversely calculate the required inductance adjustment amount and capacitance adjustment amount, wherein the higher the energy weight value, the higher the calculation priority of the corresponding inductance adjustment amount and capacitance adjustment amount; The inductance adjustment amount and the capacitance adjustment amount are encoded into the inductance-capacitance adjustment instruction and sent to the parameter adjustment interface integrated in the MCU microcontroller through the SPI communication protocol. Then, the equivalent value of the winding inductance and the safety capacitance is adjusted in real time through the parameter adjustment circuit composed of an adjustable inductor and an adjustable capacitor.

3. The method for preventing inverter harmonics from affecting the operation of an electric energy meter according to claim 2, characterized in that: The equivalent values ​​of the winding inductance and the safety capacitance are adjusted in real time by a parameter adjustment circuit composed of an adjustable inductor and an adjustable capacitor, including: The adjustable inductor receives the inductance adjustment value instruction from the parameter adjustment interface, drives the magnetic core displacement through the stepper motor, changes the effective number of turns of the inductor coil, and makes the equivalent value of the winding inductance match the target inductance; The adjustable capacitor receives the capacitance adjustment instruction from the parameter adjustment interface and dynamically adjusts the equivalent capacitance of the safety capacitor by adjusting the bias voltage of the varactor diode array; After the adjustment is completed, the real-time resonant frequency of the LC resonant circuit is verified through an impedance analyzer feedback loop, and if the deviation from the target resonant frequency exceeds a preset tolerance, a secondary calibration is triggered; The calibrated inductance value, capacitance value and energy weight value are updated to the parameter database of the MCU microcontroller and used as the benchmark reference value for subsequent dynamic matching.

4. The method for preventing inverter harmonics from affecting the operation of an electric energy meter according to claim 1, characterized in that: The S400 specifically includes the following steps: S410: Setting a dynamic temperature threshold for each power resistor branch; specifically, including: Extracting historical temperature data from the parameter database of the MCU microcontroller, including the peak temperature, average temperature rise rate and continuous working time of the power resistor; The current ambient temperature value is obtained in real time through the ambient temperature sensor, and the grid load current fluctuation rate is monitored in real time through the high-frequency current sensor; Then, the temperature threshold is dynamically calculated, and the calculated dynamic temperature threshold is associated with the corresponding power resistor number, and stored in the temperature control strategy configuration table of the MCU microcontroller; S420: Introducing a temperature hysteresis control algorithm during the switching process; specifically, including: Setting a hysteresis temperature range for each power resistor branch based on the temperature threshold; When the real-time temperature of a power resistor branch exceeds the hysteresis temperature range for the first time, it is marked as an overheat warning state and the switching countdown is started; If the real-time temperature falls back to the hysteresis temperature range during the countdown period, the warning is cancelled; otherwise, the relay switching action is triggered; After the switching is completed, the hysteresis bandwidth of the hysteresis temperature range is dynamically modified according to the load fluctuation rate.

5. The method for preventing inverter harmonics from affecting the operation of an electric energy meter according to claim 1, characterized in that: The S500 specifically includes the following steps: S510: After the relay switching action is triggered, based on the switched power resistor number and the corresponding thermal inertia parameter, obtaining the equivalent impedance change of the power resistor in real time; wherein the thermal inertia parameter includes the material specific heat capacity, heat dissipation coefficient and current ambient temperature of the power resistor, and calculating the equivalent impedance change; S520: Invoking a multi-parameter collaborative optimization model through the MCU microcontroller, combining the equivalent impedance change, the real-time harmonic spectrum data, and the historical attenuation effect records in the parameter database to generate a dynamic compensation strategy; S530: Synchronously adjusting the core displacement of the adjustable inductor, the bias voltage of the adjustable capacitor, and the parallel topology of the power resistance branch according to the dynamic compensation strategy; including: If the switching of the power resistance branch causes a parallel impedance mismatch of the power resistance branch, the parallel configuration of the power resistance branch is dynamically adjusted through a topology reconstruction module.

6. The method for preventing inverter harmonics from affecting the operation of an electric energy meter according to claim 5, characterized in that: In S530, if the switching of the power resistor branch causes a parallel impedance mismatch of the power resistor branch, the parallel configuration of the power resistor branch is dynamically adjusted by a topology reconstruction module, including: S530.

1. Deploy current sensors and voltage sensors at the input and output ends of the two power resistor branches, respectively, to monitor the current and voltage values ​​of each branch in real time. Calculate the real-time impedance value of each power resistor branch and upload the data to the MCU. S530.

2. The MCU microcontroller determines the impedance mismatch type based on a preset impedance matching threshold: If the real-time impedance value of a power resistor branch is less than the minimum value of the impedance matching threshold, and the impedance of the other power resistor branch is normal, it is determined to be a first-type single-channel impedance mismatch; If the real-time impedance value of a power resistor branch is greater than the maximum value of the impedance matching threshold, and the impedance of the other power resistor branch is normal, it is determined to be a second-type single-channel impedance mismatch; If the real-time impedance values ​​of the two power resistance branches are both less than the minimum value of the impedance matching threshold, it is determined to be a first-type dual-path impedance mismatch; If the real-time impedance values ​​of the two power resistance branches are both greater than the maximum value of the impedance matching threshold, it is determined to be a second type of dual-path impedance mismatch; If the real-time impedance value of one power resistor branch is less than the minimum value of the impedance matching threshold, and the real-time impedance value of the other power resistor branch is greater than the maximum value of the impedance matching threshold, it is determined to be a third type of dual-path impedance mismatch; S530.

3. Trigger the following reconstruction actions based on the impedance mismatch type: If the impedance mismatch type is the first type of single-path impedance mismatch, the faulty power resistance branch is disconnected and the normal power resistance branch is kept to work independently; If the impedance mismatch type is the second type of single-path impedance mismatch, connect a spare redundant power resistor branch or adjust the parameters of the normal power resistor branch; If the impedance mismatch type is the first type of dual-path impedance mismatch, all impedance branches are disconnected and load reduction protection is activated; If the impedance mismatch type is the second type of dual-path impedance mismatch, try resetting the relay or enabling virtual impedance compensation; If the impedance mismatch type is the third type of dual-path impedance mismatch, the short-circuited / overloaded impedance branch is processed first, and then the compensation strategy is implemented for the open-circuited / abnormal resistance impedance branch; S530.

4. In the single power resistance branch operating mode, adjust the series resonance parameters using the adjustable inductor and the adjustable capacitor: S530.

5. If both power resistance branches are mismatched and cannot be restored, the inverter output power is forcibly reduced by the MCU microcontroller and an audible and visual alarm is triggered.

7. The method for preventing inverter harmonics from affecting the operation of an electric energy meter according to claim 3, characterized in that: The S600 specifically includes the following steps: S610: deploying a harmonic suppression effect evaluation model in the MCU microcontroller, collecting the total harmonic distortion of the voltage of the power line of the power grid, the benchmark total harmonic distortion, and the measured value rate of the measurement error of the electric energy meter in real time, and calculating a comprehensive suppression effectiveness index, which is then stored in the historical performance record table in the parameter database; S620: Based on the comprehensive suppression effectiveness index and the historical performance record table, perform dynamic parameter recalibration: If the comprehensive suppression effectiveness index is lower than a preset threshold, a parameter backtracking analysis is triggered; the current inductance value, capacitance value, and power resistance configuration parameters are extracted from the parameter database, compared with the historical optimal parameter combination, and a parameter deviation report is generated; recalculating the target resonant frequency through the resonant frequency optimization model according to the parameter deviation report, and updating the dynamic compensation strategy through the multi-parameter collaborative optimization model; S630: Perform system health status diagnosis, including: The temperature sensor module collects real-time temperature data of the power resistor, calculates the average operating temperature based on the time series, and obtains the actual number of relay switching times through the relay drive record of the MCU microcontroller; and calculates the health score by combining the fault log of the MCU microcontroller, the maximum allowable operating temperature of the power resistor, and the rated life of the relay; S640: If the health score is lower than a preset safety threshold, a maintenance warning signal is triggered and a maintenance recommendation list is generated. The maintenance recommendation list includes: power resistor life warning, adjustable inductor core wear reminder, safety capacitor capacitance drift warning, and varistor module aging detection recommendation. At the same time, the MCU microcontroller automatically reduces the grid load current to a safe range and locks the parameter adjustment interface to prevent overload operation. S650, upload the optimized parameter configuration, health score and maintenance recommendation list to the cloud management platform through the communication module, and simultaneously update the local parameter database.

8. The method for preventing inverter harmonics from affecting the operation of an electric energy meter according to claim 7, characterized in that: The generation of the maintenance suggestion list in S640 further includes the following steps: For power resistor life warning, the remaining life percentage is dynamically calculated based on the ratio of cumulative working time to rated life, and the failure time is predicted in combination with the temperature rise curve; For adjustable inductor core wear, the degree of core mechanical loss is assessed by measuring the deviation between the stepper motor's drive current fluctuation rate and the core displacement feedback signal. For the capacitance drift of safety capacitors, the real-time capacitance measurement data of the impedance analyzer feedback loop is compared with the nominal value to generate a capacitance deviation alarm level; For aging of the varistor module, the transient suppression response time and clamping voltage offset are collected to determine whether the varistor module needs to be replaced.

9. A device for preventing inverter harmonics from affecting the operation of an electric energy meter, applied to the method for preventing inverter harmonics from affecting the operation of an electric energy meter according to any one of claims 1 to 8, characterized in that: It includes a harmonic attenuation device installed on the inverter line bus; the harmonic attenuation device is composed of an LC resonant circuit and a control circuit; The LC resonant circuit includes a winding inductor, a safety capacitor, and two parallel power resistors. The LC resonant circuit is directly connected to the power line of the power grid; a pressure sensitive module is arranged in parallel on the power line of the power grid; The control circuit includes two temperature acquisition chips, a relay, and an MCU microcontroller; the two power resistors serve as two independent power resistance branches; the two temperature acquisition chips are respectively installed on the bodies of the two power resistors, for real-time acquisition of their temperature signals and transmission to the MCU microcontroller; The MCU microcontroller determines whether to switch the power resistance branch according to a preset temperature threshold, and triggers the switching action by controlling the relay to achieve alternating switching of the two power resistance branches.

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