A method and system for operating a low frequency transformer

Abstract

The application relates to the technical field of low-frequency transformer operation control, in particular to a low-frequency transformer operation control method and system. The method comprises the following steps: acquiring electric quantity information of the output side of a low-frequency transformer, and predicting a load impact according to the electric quantity information; acquiring first operation state information, and evaluating an instantaneous dynamic margin index of the low-frequency transformer according to the first operation state information; in response to the load impact and the instantaneous dynamic margin index, adjusting the physical response characteristics of the low-frequency transformer before the load impact occurs; and distributing and adjusting active power and reactive power output by the low-frequency transformer according to an instantaneous power demand change trend. The method solves the problems of poor output voltage stability and slow response speed of the existing low-frequency transformer when facing complex load working conditions of rapidity, nonlinearity and continuous reactive power impact.

Description

Technical Field

[0001] This application relates to the field of low-frequency transformer operation control technology, and more specifically, to a low-frequency transformer operation control method and system. Background Technology

[0002] In industrial production lines, the stability of the output voltage of low-frequency transformers determines equipment operation and product quality. However, they often need to cope with drastic load changes such as the start-up and shutdown of large motors and rapid load changes, posing challenges to traditional control methods. After long-term operation, the output-side current sensor is affected by micro-vibrations and temperature cycles. Fatigue of sensitive components, impedance drift, or micro-cracks in solder joints can cause response hysteresis and slight nonlinearity, resulting in time lag and amplitude deviation in the sampled signal when the current changes rapidly. This error is not obvious in steady state but becomes prominent in high-rate transients and accumulates under frequent transients. Because the feedforward compensation model is based on ideal sensor settings, when the input current data is biased, the compensation amount and timing produce regular system deviations, making it difficult for the feedforward to fully offset voltage fluctuations. The feedback loop is forced to adjust more frequently and with greater amplitude, resulting in an increase in voltage overshoot / undershoot events in the log. The adaptive adjustment program of the control system should optimize parameters during oscillations or overshoots, but it may mistakenly judge this feedback overwork caused by feedforward failure as feedback overexcitation, thus continuously and automatically reducing the integral gain. The decrease in integral gain weakens the ability to correct persistent errors, resulting in slower voltage recovery and greater fluctuations under transient conditions.

[0003] This ultimately leads to a chain reaction of deterioration: sensor aging → current data distortion → systematic error in feedforward compensation → overworking of feedback → misjudgment of adaptive control and reduction of integral gain → further decline in control performance. As a result, the voltage stability and response speed of the transformer under complex loads with rapid, nonlinearity and continuous reactive power impact are significantly lower than the design expectations, and due to the coupling of multiple links, it is difficult to troubleshoot using conventional methods.

[0004] To address the aforementioned issues, existing technologies urgently need improvement. Summary of the Invention

[0005] This application discloses a low-frequency transformer operation control method and system, which aims to solve the problems of poor output voltage stability and slow response speed of existing low-frequency transformers when facing complex load conditions with rapid, nonlinear and continuous reactive power impacts.

[0006] The technical solution of this application is as follows: In a first aspect, this application discloses a low-frequency transformer operation control method, the method comprising: Acquire electrical information from the output side of the low-frequency transformer, identify the instantaneous power demand change trend of the load based on the electrical information, and predict load impact. The electrical information includes output side voltage information and output side current information. The first operating status information inside the low-frequency transformer is obtained, and the current ability of the low-frequency transformer to withstand instantaneous impact is evaluated based on the first operating status information to obtain an instantaneous dynamic margin index characterizing the withstand capability. The first operating status information includes winding temperature information, core operating status information and / or power switching device temperature information. In response to load surges and instantaneous dynamic margin indicators, the physical response characteristics of the low-frequency transformer are adjusted before the load surge occurs to provide additional voltage support. Adjusting the physical response characteristics of the low-frequency transformer includes: adjusting the excitation voltage, adjusting the switching frequency and / or control parameters of the power converter associated with the low-frequency transformer. Based on the instantaneous power demand change trend, the active power and reactive power output of the low-frequency transformer are distributed and regulated. The distribution and regulation include: implementing reactive power compensation control based on the instantaneous power demand change trend, and / or implementing harmonic suppression based on the current harmonic characteristics of the low-frequency transformer output side.

[0007] Furthermore, in response to load surges and instantaneous dynamic margin indicators, the physical response characteristics of the low-frequency transformer are adjusted before the load surge occurs to provide additional voltage support, including: Spectral analysis of the output current information is performed to identify the characteristics of high-frequency current components; Vibration signals and local temperature data inside a low-frequency transformer are acquired to assess the resonance risk inside the transformer, and thermal stress indices characterizing thermal stress are determined based on the local temperature data. When the instantaneous dynamic margin index meets the preset margin triggering condition, and before the load impact occurs, the switching frequency of the power converter is adjusted according to the characteristics of the high-frequency current component, resonance risk and thermal stress index, as well as the inherent resonant frequency of the low-frequency transformer, so as to provide additional voltage support to suppress the low-frequency reactive power impact and reduce the resonance risk caused by the switching frequency of the power converter and the frequency and / or inherent resonant frequency of the high-frequency current component. When the resonance risk still meets the preset risk triggering conditions, adjust the control parameters of the power converter.

[0008] Furthermore, based on the electricity information, the instantaneous power demand change trend of the load is identified to predict load surges, including: Obtain the second operating status information of the load, and identify the operating mode of the load based on the second operating status information; Instantaneous reactive power and its rate of change are calculated based on output-side voltage and current information to characterize the trend of instantaneous power demand changes. Spectral analysis is performed on the output-side current information to extract high-frequency current component features; The analysis results are obtained by combining the operating mode, the rate of change of instantaneous reactive power and the characteristics of high-frequency current components, and by analyzing whether the low-frequency reactive power impact and high-frequency current component characteristics reflected by the rate of change of instantaneous reactive power are consistent with the operating mode, based on the correlation rules between the operating mode and the pre-stored electrical energy characteristics. When the analysis results are consistent, a warning signal characterizing the load impact is generated and output. The warning signal includes indication information that the load impact is about to occur. When the rate of change of instantaneous reactive power is detected to meet the preset low-frequency reactive power impact criterion, and the analysis results are inconsistent, and the high-frequency current component characteristics match the high-frequency interference characteristics corresponding to the operating mode, the warning signal is suppressed. Suppressing the warning signal includes not outputting the warning signal and / or not allowing the warning signal to trigger the adjustment of the physical response characteristics of the low-frequency transformer.

[0009] Furthermore, based on the first operating state information, the current ability of the low-frequency transformer to withstand instantaneous impacts is assessed to obtain an instantaneous dynamic margin index characterizing the withstand capability, including: Obtain the first historical calibration data of the internal sensors corresponding to the first operating status information; Obtain the operating environment parameters of the internal sensors; Based on the first historical calibration data, working environment parameters, and the type of internal sensor, the first operating status information is corrected to compensate for nonlinear drift and measurement deviation caused by long-term operation of the internal sensor. The ability of a low-frequency transformer to withstand instantaneous impacts is assessed based on the revised first operating status information, and the instantaneous dynamic margin index is determined accordingly.

[0010] Furthermore, based on the electricity information, the instantaneous power demand change trend of the load is identified, including: Obtain the environmental parameters of the voltage sensor corresponding to the output voltage information and the environmental parameters of the current sensor corresponding to the output current information; Acquire second historical calibration data for the voltage and current sensors; Based on the environmental parameters of the voltage sensor, the environmental parameters of the current sensor, the second historical calibration data, and the types of the voltage sensor and the current sensor, the output voltage information and the output current information are corrected to compensate for the measurement deviation caused by sensor nonlinear drift or random noise. Calculate the instantaneous reactive power based on the corrected output voltage and current information. Adaptive filtering is applied to instantaneous reactive power. The instantaneous power demand trend can be identified by the rate of change of the filtered instantaneous reactive power.

[0011] Furthermore, the ability of the low-frequency transformer to withstand transient impacts is assessed based on the revised first operating status information, and instantaneous dynamic margin indicators are determined accordingly, including: Acquire partial discharge signals that characterize the insulation state of low-frequency transformers; The thermal margin is determined based on the corrected winding temperature information, the core margin is determined based on the corrected core operating status information, the power switch margin is determined based on the corrected power switching device temperature information, and the insulation margin is determined based on the partial discharge signal. The instantaneous power is calculated based on the output voltage and current information, and the low-frequency transformer is judged to be in short-circuit impact condition or overload operation condition based on the rate of change of instantaneous power. When it is determined that the short-circuit impact condition is underway, the first margin weighting information of thermal margin and magnetic core margin is adjusted based on the rate of change of magnetic core flux density information, the rate of rise of power switching device temperature information, and the intensity of partial discharge signal in the magnetic core working status information. When it is determined that the operation is under overload conditions, the second margin weight information of thermal margin and insulation margin is adjusted according to the rising rate of winding temperature information, the absolute value of power switching device temperature information and the duration of partial discharge signal. Based on the adjusted first margin weight information or the adjusted second margin weight information, the thermal margin, core margin and insulation margin are weighted and fused to obtain a weighted fusion result. The weighted fusion result is then constrained and corrected based on the power switch margin to determine the instantaneous dynamic margin index.

[0012] Furthermore, the low-frequency transformer is judged to be under short-circuit impulse or overload operation conditions based on the instantaneous power change rate, including: Spectral analysis of the output current information is performed to obtain the characteristics of the high-frequency current components; Obtain the voltage sensor noise parameters corresponding to the output voltage information and the current sensor noise parameters corresponding to the output current information; Signal verification is performed based on the rate of change of instantaneous power, the characteristics of high-frequency current components, and the noise parameters of voltage and current sensors. When the signal verification result shows that the instantaneous power change rate meets the preset operating condition criteria, and the high-frequency current component characteristics, voltage sensor noise parameters and current sensor noise parameters are all within the corresponding preset normal ranges, the judgment result of short-circuit impact condition or overload operation condition is output. When the high-frequency current component characteristics, voltage sensor noise parameters, or current sensor noise parameters exceed the corresponding preset normal range, no judgment result is output and / or the judgment result is not allowed to trigger the adjustment of the first margin weight information or the second margin weight information.

[0013] Furthermore, based on the instantaneous power demand change trend, the active and reactive power output of the low-frequency transformer are allocated and adjusted, including: Based on the instantaneous power demand change trend, determine the target allocation ratio of active power and reactive power output by the low-frequency transformer. When the instantaneous dynamic margin index meets the preset margin constraint, the active power distribution of the low-frequency transformer is adjusted by controlling the control parameters of the power converter so that the active power distribution meets the target distribution ratio. When the instantaneous dynamic margin index meets the preset margin constraint, the reactive power distribution of the low-frequency transformer is adjusted by controlling the control parameters of the power converter so that the reactive power distribution of the low-frequency transformer meets the reactive power distribution requirements corresponding to the target distribution ratio. Based on the current harmonic characteristics of the output current information, a harmonic suppression command is generated, and the control parameters of the power converter are adjusted to implement harmonic suppression, so that the amplitude of at least one preset target harmonic component in the output current information is within the corresponding preset amplitude suppression threshold range. When the instantaneous dynamic margin index does not meet the preset margin constraint, the reactive power allocation and / or active power allocation shall be reduced, and / or the control gain corresponding to the harmonic suppression command shall be limited.

[0014] Furthermore, the target allocation ratio of active power to reactive power output from the low-frequency transformer is determined, including: The reactive power target compensation amount is determined based on the instantaneous power demand change trend, and the active power target support amount is determined based on the deviation between the output voltage information and the preset voltage reference. When the instantaneous dynamic margin index meets the preset margin constraint, the target allocation ratio is determined based on the ratio of the reactive power target compensation amount to the active power target support amount. When the instantaneous dynamic margin index does not meet the preset margin constraint, the reactive power target compensation amount and / or active power target support amount are reduced synchronously according to the preset derating factor in order to update the target allocation ratio.

[0015] Secondly, this application also discloses a low-frequency transformer operation control system, which includes: The power information acquisition module is used to acquire power information from the output side of the low-frequency transformer, identify the instantaneous power demand change trend of the load based on the power information, and predict load impact. The power information includes output voltage information and output current information. The operating status acquisition module is used to acquire the first operating status information inside the low-frequency transformer, and to evaluate the current ability of the low-frequency transformer to withstand instantaneous impacts based on the first operating status information, so as to obtain an instantaneous dynamic margin index characterizing the withstand capability. The first operating status information includes winding temperature information, core operating status information and / or power switching device temperature information. The physical response adjustment module is used to adjust the physical response characteristics of the low-frequency transformer in response to load surges and instantaneous dynamic margin indicators before load surges occur, so as to provide additional voltage support. Adjusting the physical response characteristics of the low-frequency transformer includes: adjusting the excitation voltage, adjusting the switching frequency and / or control parameters of the power converter associated with the low-frequency transformer. The power distribution and regulation module is used to distribute and regulate the active and reactive power output of the low-frequency transformer according to the instantaneous power demand change trend. The distribution and regulation includes: implementing reactive power compensation control according to the instantaneous power demand change trend, and / or implementing harmonic suppression according to the current harmonic characteristics of the low-frequency transformer output side.

[0016] Beneficial Effects: This application, through comprehensive analysis of power information and internal operating status information, can more accurately predict load surges and assess the transformer's withstand capacity in real time, thus proactively intervening before load surges occur, rather than passively responding. This forward-looking control strategy, combined with intelligent allocation and adjustment of active and reactive power, can significantly improve the output voltage stability and response speed of low-frequency transformers when facing complex load conditions with rapid, nonlinear, and continuous reactive power surges. Compared with existing technologies, this application avoids performance degradation caused by sensor degradation and internal logic misjudgments in the control system, achieving refined and adaptive control of the transformer's operating status, thereby overcoming the comprehensive control problems that traditional control systems struggle to solve, and exhibiting significant and superior technical effects. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating a low-frequency transformer operation control method provided in this application.

[0018] Figure 2 A flowchart of a low-frequency transformer operation control system provided in this application.

[0019] In the diagram: 1. Power information acquisition module; 2. Operating status acquisition module; 3. Physical response adjustment module; 4. Power distribution adjustment module. Detailed Implementation

[0020] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. The components of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0021] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0022] In industrial production, low-frequency transformers are critical power conversion devices, and the stability of their output voltage is essential for the normal operation of the production line and product quality. However, after long-term operation, existing transformer control systems exhibit systematic deviations in their feedforward compensation models when facing rapidly changing loads due to nonlinear drift and response hysteresis in core components such as current sensors. This deviation causes the feedback regulation logic to overwork passively and may be misjudged by the adaptive regulation program, resulting in an incorrect reduction of the integral gain. Ultimately, this leads to the transformer's output voltage stability and response speed falling far short of design expectations when dealing with complex load conditions, creating a comprehensive control problem that is difficult to solve using conventional methods.

[0023] Reference Figure 1 In response, this application proposes a low-frequency transformer operation control method, the method comprising: S1000: Acquires electrical information from the output side of the low-frequency transformer, identifies the instantaneous power demand change trend of the load based on the electrical information, and predicts load impact. The electrical information includes output side voltage information and output side current information. S2000: Obtain the first operating status information inside the low-frequency transformer, evaluate the current ability of the low-frequency transformer to withstand instantaneous impact based on the first operating status information, and obtain the instantaneous dynamic margin index characterizing the withstand capability. The first operating status information includes winding temperature information, core operating status information and / or power switching device temperature information. S3000: In response to load surges and instantaneous dynamic margin indicators, adjust the physical response characteristics of the low-frequency transformer before the load surge occurs to provide additional voltage support. Adjusting the physical response characteristics of the low-frequency transformer includes: adjusting the excitation voltage, adjusting the switching frequency and / or control parameters of the power converter associated with the low-frequency transformer. S4000: Based on the instantaneous power demand change trend, the active power and reactive power output of the low-frequency transformer are distributed and regulated. The distribution and regulation include: implementing reactive power compensation control based on the instantaneous power demand change trend, and / or implementing harmonic suppression based on the current harmonic characteristics of the low-frequency transformer output side.

[0024] Specifically, low-frequency transformers typically refer to transformers operating within the standard frequency range of power systems (such as 50Hz or 60Hz). Their main function is to transform voltage and current, and they are widely used in industrial production. Electrical quantity information refers to various electrical parameters used to describe the operating status of a power system, such as voltage, current, and power. Load impact refers to the phenomenon of drastic fluctuations in power system voltage or current caused by rapid load changes (such as the start-up and shutdown of high-power equipment or rapid load changes). Instantaneous power demand change trend refers to the dynamic changes in the load's demand for active and reactive power over a short period of time. First operating status information refers to the operating parameters of key components inside the low-frequency transformer and key components of the power converter associated with it, such as winding temperature information, core operating status information, and power switching device temperature information, used to characterize the health and withstand capacity of the low-frequency transformer. The instantaneous dynamic margin index is an indicator that quantifies the ability of a low-frequency transformer to maintain stable operation under instantaneous impacts; it comprehensively considers the withstand limits of multiple aspects such as heat, magnetism, and insulation. Physical response characteristics refer to the inherent response behavior of a low-frequency transformer under electrical excitation, such as the response of its output voltage to the input excitation voltage, and its response to changes in the switching frequency and control parameters of the power converter. A power converter is a power electronic device that works in conjunction with a low-frequency transformer to achieve flexible control and regulation of voltage, current, and frequency; examples include active power filters and static var generators.

[0025] During implementation, the electrical quantity information of the low-frequency transformer output side is first acquired. This information is collected by voltage and current sensors and converted into digital signals by an analog-to-digital converter before being input into the system. For example, voltage sensors can be capacitive or resistive voltage dividers; current sensors can be Hall effect sensors or Rogowski coils. Subsequently, based on the output voltage and current information, the instantaneous power demand trend of the load is identified to predict load surges. For example, by calculating instantaneous active and reactive power and analyzing their rate of change, direction of change, and magnitude of change, it can be determined whether an impending surge is imminent. In particular, when instantaneous reactive power experiences a significant increase or decrease within a very short period, load surges can be predicted.

[0026] Simultaneously, the system acquires the initial operating status information of the low-frequency transformer to assess its current ability to withstand instantaneous impacts and generate an instantaneous dynamic margin index. This initial operating status information includes the winding temperature information and core operating status information within the low-frequency transformer body, as well as the temperature information of the power switching devices in the power converter associated with the transformer. For example, the winding temperature information can be acquired by a resistance temperature detector (RTD) or thermocouple sensor; the core operating status information can be acquired by a flux sensor or magnetic field strength sensor to reflect the flux density or magnetic field strength and assess the degree of saturation; and the power switching device temperature information can be acquired by an infrared sensor or a built-in temperature sensor. The system maps the winding temperature information, core operating status information, and power switching device temperature information into corresponding margin components and obtains the instantaneous dynamic margin index through a preset comprehensive margin model, which characterizes the currently available instantaneous withstand margin.

[0027] When a load surge is predicted and early intervention is required based on instantaneous dynamic margin indicators, the physical response characteristics of the low-frequency transformer can be adjusted before the load surge occurs to provide additional voltage support. Adjusting the excitation voltage can be achieved by controlling the voltage regulator on the primary side of the low-frequency transformer, for example, by changing the tap position or controlling the output voltage of the series transformer. Adjusting the switching frequency of the power converter associated with the low-frequency transformer can be achieved by changing the frequency of the PWM signal. Adjusting control parameters may include modifying parameters such as the gain and dead time of the PI controller inside the power converter to improve output voltage support capability and suppress voltage drops or overshoots before the surge occurs.

[0028] Based on this, the active and reactive power output of the low-frequency transformer is distributed and regulated according to the instantaneous power demand change trend. This distribution and regulation includes reactive power compensation control based on the instantaneous power demand change trend, and / or harmonic suppression based on the current harmonic characteristics of the low-frequency transformer output side. For example, when a significant increase in instantaneous reactive power demand is detected, the power converter can be instructed to output additional reactive power for compensation to maintain system voltage stability. Reactive power compensation can be achieved by switching capacitor banks or reactor banks, or by adjusting the output reactive current of the active power filter. When the output current information shows significant current harmonics, a harmonic suppression command can be generated. By adjusting the control parameters of the power converter, it generates a compensation current equal in magnitude and opposite in direction to the harmonic current to cancel the harmonics and improve power quality.

[0029] In another embodiment of this application, S3000 is further proposed to include: S3100: Performs spectrum analysis on the output current information to identify high-frequency current component characteristics; S3200: Acquire vibration signals and local temperature data inside the low-frequency transformer to assess the resonance risk inside the low-frequency transformer, and determine the thermal stress index characterizing thermal stress based on the local temperature data. S3300: When the instantaneous dynamic margin index meets the preset margin triggering condition, and before the load impact occurs, the switching frequency of the power converter is adjusted according to the characteristics of the high-frequency current component, resonance risk and thermal stress index, as well as the inherent resonant frequency of the low-frequency transformer, thereby providing additional voltage support to suppress low-frequency reactive power impact and reduce the resonance risk caused by the switching frequency of the power converter and the frequency and / or inherent resonant frequency of the high-frequency current component. S3400: Adjust the control parameters of the power converter when the resonance risk still meets the preset risk triggering conditions.

[0030] Spectrum analysis of the output current information involves using signal processing techniques such as Fourier transform to convert the time-domain signal of the low-frequency transformer's output current into a frequency-domain signal, thereby identifying the fundamental frequency, harmonics, and other high-frequency components. The purpose is to accurately determine the nonlinear characteristics of the load or the high-frequency current components introduced by external interference. These components may couple with the switching frequency of the power converter or the inherent resonant frequency of the low-frequency transformer, triggering resonance.

[0031] Furthermore, acquiring vibration signals and local temperature data inside the low-frequency transformer refers to real-time monitoring of the mechanical vibration and local hot spot temperature of key components such as the transformer windings and core using vibration and temperature sensors installed inside the transformer. Vibration signals can directly reflect the presence of abnormal mechanical stress or resonance phenomena inside the transformer, while local temperature data can indicate the presence of overheating risk or thermal stress concentration. Based on the local temperature data, thermal stress indicators characterizing thermal stress can be determined, such as calculating temperature gradients, temperature rise rates, or margins relative to the material's thermal limit. The purpose is to quantify the transformer's ability to withstand thermal loads under instantaneous impacts, providing crucial safety boundaries for subsequent physical response adjustments.

[0032] In practical applications, when the instantaneous dynamic margin meets the preset margin triggering conditions and before the load surge occurs, the switching frequency of the power converter is adjusted based on the characteristics of the high-frequency current components, resonance risk, thermal stress indicators, and the inherent resonant frequency of the low-frequency transformer. This means that, provided the transformer has a certain withstand capacity, the system will comprehensively consider external high-frequency interference, the possibility of internal resonance, the level of thermal stress, and the transformer's own physical resonant point to intelligently select a switching frequency that meets the preset target. This adjustment aims to provide necessary voltage support to suppress low-frequency reactive power surges, while actively avoiding or reducing the risk of resonance between the power converter's switching frequency and the frequency of the high-frequency current components and / or the inherent resonant frequency, thereby preventing overvoltage, overcurrent, or mechanical damage caused by resonance.

[0033] Furthermore, when the resonance risk still meets the preset risk triggering conditions, the control parameters of the power converter are adjusted. This is a secondary protection or optimization mechanism. Even after adjusting the switching frequency, if the vibration signal or spectrum analysis results still show a high resonance risk, the system will further fine-tune the control parameters of the power converter, such as changing its gain, phase, or damping characteristics, to enhance the stability of the system, actively suppress residual resonance effects, and ensure the safe and stable operation of the low-frequency transformer under complex operating conditions.

[0034] In another embodiment of this application, the step of identifying the instantaneous power demand change trend of the load based on power information to predict load surges includes: S1100: Obtain the second operating status information of the load and identify the operating mode of the load based on the second operating status information; S1200: Calculates instantaneous reactive power and its rate of change based on output-side voltage and current information to characterize the trend of instantaneous power demand changes; S1300: Performs spectral analysis on the output-side current information to extract high-frequency current component features; S1400: Based on the operating mode, the rate of change of instantaneous reactive power, and the characteristics of high-frequency current components, a joint judgment is made. Based on the correlation rules between the operating mode and the pre-stored electrical energy characteristics, the analysis is conducted to determine whether the low-frequency reactive power impact and high-frequency current component characteristics reflected by the rate of change of instantaneous reactive power are consistent with the operating mode, and the analysis results are obtained. S1500: When the analysis results are consistent, generate and output a warning signal characterizing the load impact. The warning signal includes indication information that the load impact is about to occur. S1600: When the rate of change of instantaneous reactive power is detected to meet the preset low-frequency reactive power impact criterion, and the analysis results are inconsistent, and the high-frequency current component characteristics match the high-frequency interference characteristics corresponding to the operating mode, the warning signal is suppressed. Suppressing the warning signal includes not outputting the warning signal and / or not allowing the warning signal to trigger the adjustment of the physical response characteristics of the low-frequency transformer.

[0035] Specifically, acquiring the second operating status information of the load refers to obtaining non-electrical information related to the load's operation through additional sensors or system interfaces, such as the load's mechanical state, control commands, and duty cycle. The purpose is to provide more comprehensive contextual information for subsequent load pattern recognition. Identifying the load's operating mode based on the second operating status information can be understood as using this non-electrical information, combined with preset rules or machine learning models, to determine the load's current operating state, such as startup, stable operation, shutdown, or switching. The purpose is to provide crucial background information for predicting load surges.

[0036] The calculation of instantaneous reactive power and its rate of change based on output-side voltage and current information to characterize the trend of instantaneous power demand changes involves using real-time acquired output-side voltage and current information to calculate instantaneous reactive power through instantaneous power theory, and further calculating the rate of change of instantaneous reactive power over time. The rate of change of instantaneous reactive power directly reflects the load's instantaneous demand for reactive power and is a key indicator for predicting low-frequency reactive power surges.

[0037] In practical applications, spectral analysis of output-side current information to extract high-frequency current component characteristics involves using signal processing techniques such as Fourier transform to decompose the output-side current information into components of different frequencies and identifying the frequency, amplitude, phase, and other characteristics of the high-frequency components. These high-frequency current component characteristics can be used to characterize the nonlinear properties of the load, harmonic interference, or specific types of high-frequency disturbances, thus providing additional criteria for subsequent joint judgments.

[0038] Furthermore, a joint judgment is made based on the operating mode, the rate of change of instantaneous reactive power, and the characteristics of high-frequency current components. Following the correlation rules between the operating mode and pre-stored electrical characteristic features, the system analyzes whether the low-frequency reactive power impact reflected by the rate of change of instantaneous reactive power and the characteristics of high-frequency current components are consistent with the operating mode. The resulting analysis means that the system uses the operating mode as a background constraint, the rate of change of instantaneous reactive power as the primary criterion for low-frequency reactive power impact, and the characteristics of high-frequency current components as interference verification or type identification criteria. These are compared with pre-stored electrical characteristic correlation rules to determine whether the currently observed low-frequency reactive power impact and its accompanying high-frequency characteristics conform to the expected electrical behavior under that operating mode. For example, under a specific operating mode, if the rate of change of instantaneous reactive power and the characteristics of high-frequency current components satisfy the electrical characteristic correlation rules corresponding to that operating mode, then the analysis result is consistent.

[0039] When the analysis results are consistent, an early warning signal characterizing the load impact is generated and output. The early warning signal includes indication information that the load impact is about to occur. It means that after confirming the existence of a low-frequency reactive power impact symptom consistent with the operating mode under the constraints of the operating mode, the system outputs an early warning signal to provide a trigger basis for adjusting the physical response characteristics of the low-frequency transformer before the load impact occurs.

[0040] When the rate of change of instantaneous reactive power meets the preset low-frequency reactive power impulse criterion, and the analysis results are inconsistent, and the high-frequency current component characteristics match the high-frequency interference characteristics corresponding to the operating mode, the warning signal is suppressed. Suppressing the warning signal includes not outputting the warning signal and / or not allowing the warning signal to trigger the adjustment of the physical response characteristics of the low-frequency transformer. This means that even when the low-frequency reactive power impulse criterion is met, the system still performs consistency verification and interference matching verification. If the low-frequency reactive power impulse symptoms are found to be inconsistent with the operating mode, and the high-frequency current component characteristics are more consistent with the high-frequency interference characteristics corresponding to the operating mode, it is determined to be an operating disturbance or normal transient rather than a real load impulse, thereby suppressing the warning signal and avoiding unnecessary control actions.

[0041] The proposed solution constructs a multi-dimensional load impact prediction mechanism by introducing the second operating state information of the load, calculating the instantaneous reactive power and its rate of change, and performing spectral analysis on the output current information to extract high-frequency current component characteristics. It also performs consistency analysis by associating the operating mode with pre-stored power characteristics.

[0042] In another embodiment of this application, the step of assessing the current ability of a low-frequency transformer to withstand instantaneous impacts based on first operating state information to obtain an instantaneous dynamic margin index characterizing the withstand capability includes: S2100: Obtain the first historical calibration data of the internal sensor corresponding to the first operating status information; S2200: Acquires the operating environment parameters of the internal sensors; S2300: Based on the first historical calibration data, working environment parameters and the type of internal sensor, the first operating status information is corrected to compensate for nonlinear drift and measurement deviation caused by long-term operation of internal sensors. S2400: Evaluate the ability of a low-frequency transformer to withstand instantaneous impacts based on the corrected first operating status information, and determine the instantaneous dynamic margin index accordingly.

[0043] Internal sensors refer to various sensors used to monitor the internal operating status of low-frequency transformers, such as temperature sensors, magnetic field sensors, and vibration sensors. The first historical calibration data can be understood as the performance parameters, error curves, or correction coefficients obtained from calibration or testing of these internal sensors under different operating conditions and time points. Its purpose is to provide a benchmark for subsequent data correction. The operating environment parameters of the internal sensors refer to the environmental conditions in which the internal sensors operate, such as ambient temperature, humidity, and electromagnetic interference intensity. These parameters may affect the measurement accuracy and stability of the internal sensors. Based on the first historical calibration data, operating environment parameters, and the type of internal sensor, the first operating status information is corrected. This correction process aims to compensate for nonlinear drift and measurement deviations caused by long-term operation of the internal sensors.

[0044] Nonlinear drift refers to the loss of linearity between the output of an internal sensor and the actual physical quantity, while measurement deviation refers to the systematic or random difference between the output value of the internal sensor and the true value. By combining the first historical calibration data and the operating environment parameters of the internal sensor, a correction model or lookup table can be established to precisely adjust the original first operating state information, thereby obtaining more accurate and reliable internal operating state data. Finally, the ability of the low-frequency transformer to withstand instantaneous impacts is evaluated based on the corrected first operating state information, and the instantaneous dynamic margin index is determined accordingly. After obtaining the corrected accurate operating state information, this information can be used in conjunction with a preset evaluation model or algorithm to comprehensively analyze the low-frequency transformer's ability to withstand instantaneous impacts under the current state. For example, based on the corrected winding temperature information, core operating state information, and / or power switching device temperature information, thermal margin, core margin, and / or power switching margin can be determined, and the thermal margin, core margin, and / or power switching margin can be comprehensively quantified into an instantaneous dynamic margin index, which can intuitively reflect the remaining capacity of the low-frequency transformer when facing sudden load impacts.

[0045] This application can significantly improve the accuracy and reliability of evaluating the instantaneous dynamic margin index of low-frequency transformers. Traditional methods may produce misjudgments due to nonlinear drift and measurement deviation caused by long-term operation of internal sensors, thereby affecting the prediction of load impacts and the adjustment of physical response characteristics.

[0046] In another embodiment of this application, the step of identifying the instantaneous power demand change trend of the load based on power information to predict load surges includes: S1001: Obtain the environmental parameters of the voltage sensor corresponding to the output voltage information and the environmental parameters of the current sensor corresponding to the output current information; S1002: Acquire the second historical calibration data of the voltage sensor and current sensor; S1003: Based on the environmental parameters of the voltage sensor, the environmental parameters of the current sensor, the second historical calibration data, and the types of the voltage sensor and the current sensor, the output voltage information and the output current information are corrected to compensate for the measurement deviation caused by sensor nonlinear drift or random noise. S1004: Calculate the instantaneous reactive power based on the corrected output voltage and current information. S1005: Adaptive filtering of instantaneous reactive power; S1006: Identify the trend of instantaneous power demand change based on the rate of change of the filtered instantaneous reactive power.

[0047] Specifically, the environmental parameters of the voltage sensor and the current sensor refer to the external conditions that affect the measurement accuracy of the sensors, such as ambient temperature, humidity, and electromagnetic interference intensity. These parameters can be monitored in real time using additional environmental sensors or estimated using preset models. Secondly, historical calibration data refers to the deviation data obtained by calibrating the voltage and current sensors under different operating conditions using standard equipment. This data can be stored in the control system's memory for subsequent data correction.

[0048] The correction of output voltage and current information aims to eliminate or reduce the impact of nonlinear drift and random noise that may occur in the sensor during long-term operation on the measurement results. Various algorithms can be used in the correction process, such as lookup table-based compensation, polynomial fitting correction, and Kalman filtering, with the goal of improving the accuracy of the original electrical information.

[0049] In practical applications, instantaneous reactive power is calculated based on the corrected output voltage and current information. Instantaneous power theory (such as PQ theory) can be used for the calculation, with the aim of obtaining the real-time reactive power demand of the load.

[0050] Furthermore, adaptive filtering of instantaneous reactive power refers to dynamically adjusting the filter parameters based on the dynamic characteristics of instantaneous reactive power, so as to effectively filter out noise while preserving the true trend of instantaneous reactive power changes as much as possible. For example, adaptive Kalman filters, adaptive median filters, or adaptive filtering methods based on wavelet transform can be used, with the aim of smoothing data, reducing noise interference, and highlighting the true characteristics of instantaneous reactive power changes.

[0051] Therefore, identifying the trend of instantaneous power demand changes based on the rate of change of filtered instantaneous reactive power can be achieved by calculating the derivative of instantaneous reactive power with respect to time or by using the difference method. By analyzing the magnitude, direction, and duration of its rate of change, it is possible to accurately determine whether the load is in a state of increasing, decreasing, or stable instantaneous reactive power demand, thus providing a reliable basis for predicting load surges.

[0052] In another embodiment of this application, it is further proposed to evaluate the ability of a low-frequency transformer to withstand instantaneous impacts based on the modified first operating state information, and to determine the instantaneous dynamic margin index accordingly, including: S2410: Acquire partial discharge signals characterizing the insulation state of low-frequency transformers; S2420: Determine the thermal margin based on the corrected winding temperature information, determine the core margin based on the corrected core operating status information, determine the power switch margin based on the corrected power switching device temperature information, and determine the insulation margin based on the partial discharge signal. S2430: Calculates instantaneous power based on output voltage and current information, and determines whether the low-frequency transformer is under short-circuit impact or overload operation based on the rate of change of instantaneous power. S2440: When it is determined that the short-circuit impact condition is underway, the first margin weight information of thermal margin and magnetic core margin is adjusted according to the rate of change of magnetic core flux density information, the rate of rise of power switching device temperature information and the intensity of partial discharge signal in the magnetic core working status information. S2450: When it is determined that the operation is under overload conditions, the second margin weight information of thermal margin and insulation margin is adjusted according to the rising rate of winding temperature information, the absolute value of power switching device temperature information and the duration of partial discharge signal. S2460: Based on the adjusted first margin weight information or the adjusted second margin weight information, the thermal margin, core margin and insulation margin are weighted and fused to obtain a weighted fusion result, and the weighted fusion result is constrained and corrected based on the power switch margin to determine the instantaneous dynamic margin index.

[0053] Specifically, when assessing the ability of a low-frequency transformer to withstand transient impacts, the first step is to acquire a partial discharge signal that characterizes the insulation condition of the transformer. The partial discharge signal is a key indicator for assessing the health of the insulation system; its intensity and frequency reflect the degree of insulation degradation. This signal can be monitored in real time using a partial discharge sensor installed inside the transformer.

[0054] Among these, thermal margin can be understood as the remaining space between the low-frequency transformer winding and its maximum allowable temperature at the current temperature, reflecting the winding's thermal withstand capability. Core margin refers to the remaining space between the magnetic core and its saturation magnetic flux density at the current operating state, reflecting the core's magnetic withstand capability. Power switch margin refers to the remaining space between the power switching device and its maximum allowable temperature at the current temperature, reflecting the power switching device's thermal withstand capability. Insulation margin refers to the remaining space between the low-frequency transformer insulation system and its insulation breakdown threshold at the current partial discharge level, reflecting the insulation system's electrical withstand capability. These margin indicators are determined based on corrected first operating state information, such as corrected winding temperature information, corrected core operating state information, and corrected power switching device temperature information, as well as the acquired partial discharge signals.

[0055] In practical applications, instantaneous power can be obtained by real-time acquisition and calculation of output-side voltage and current information. By analyzing the rate of change of instantaneous power, the current operating condition of the low-frequency transformer can be determined. For example, when the instantaneous power experiences a drastic and significant drop or abnormal fluctuation within a very short period of time, it may be under short-circuit impact conditions; while when the instantaneous power remains above the rated value but the rate of change is relatively gradual, it may be under overload operating conditions.

[0056] Furthermore, when a short-circuit impact condition is identified, since the short-circuit impact primarily affects the magnetic core and power switching devices, and may lead to localized overheating of the windings, it is necessary to dynamically adjust the first margin weighting information of thermal margin and magnetic core margin based on the rate of change of magnetic core flux density information, the rate of temperature rise of power switching devices, and the intensity of partial discharge signals in the magnetic core operating status information. For example, when the rate of change of magnetic core flux density is high, the temperature rise of power switching devices is rapid, and the intensity of partial discharge is large, the weighting of magnetic core margin and thermal margin should be appropriately increased to place greater emphasis on the withstand capability of these critical components.

[0057] As a preferred implementation, when an overload operating condition is identified, since overload operation primarily causes long-term thermal stress on the windings and insulation system, it is necessary to dynamically adjust the weighting information of the second margin of thermal margin and insulation margin based on the rate of temperature rise of the windings, the absolute value of the temperature of the power switching devices, and the duration of the partial discharge signal. For example, when the rate of temperature rise of the windings is fast, the absolute value of the temperature of the power switching devices is high, and the duration of the partial discharge is long, the weighting of thermal margin and insulation margin should be appropriately increased to place greater emphasis on the long-term reliability of these components.

[0058] Therefore, based on the adjusted first or second margin weight information, the thermal margin, core margin, and insulation margin are weighted and fused to obtain a comprehensive weighted fusion result. This weighted fusion result reflects the comprehensive bearing capacity of the main internal components of the low-frequency transformer under current operating conditions. Furthermore, the weighted fusion result is constrained and corrected based on the power switching margin. For example, if the power switching margin is too low, even if other margins are high, it may limit the overall instantaneous dynamic margin index, thus ensuring that the weak points of the entire system are fully considered, and ultimately determining a more accurate and reliable instantaneous dynamic margin index.

[0059] This application's solution addresses the shortcomings of traditional evaluation methods, such as insufficient accuracy and poor adaptability, by introducing multi-dimensional margin indicators and dynamically adjusting their weights according to the specific operating conditions of the low-frequency transformer. A specific example from some preferred embodiments is provided below: Assuming a low-frequency transformer is in operation, its control system first acquires corrected winding temperature information, core operating status information, and power switching device temperature information, as well as partial discharge signals obtained through a partial discharge sensor. Based on this information, the system calculates the current thermal margin, core margin, power switching margin, and insulation margin.

[0060] Specifically, when the system detects that the instantaneous power on the output side suddenly increases from 10kW to 100kW in a very short time, and the rate of change exceeds a preset threshold, it determines that the system is currently under a short-circuit impact condition. At this time, the system dynamically adjusts the first margin weighting information of thermal margin and core margin based on the rate of change of the magnetic core flux density (e.g., from 0.8T / ms to 1.5T / ms), the rate of increase of the power switching device temperature (e.g., from 2 degrees Celsius / second to 10 degrees Celsius / second), and the intensity of the partial discharge signal (e.g., from 50pC to 500pC). For example, the weight of the core margin is increased from 0.3 to 0.5, and the weight of the thermal margin is increased from 0.4 to 0.45, to further emphasize the core and winding's ability to withstand short-circuit impacts.

[0061] Subsequently, if the system detects that the instantaneous power remains around 50kW, significantly higher than the rated power of 30kW, but the rate of change is relatively gradual, it determines that the system is currently operating under overload conditions. At this point, the system dynamically adjusts the weighting of the second margin information for thermal margin and insulation margin based on the rate of increase of winding temperature information (e.g., from 0.5 degrees Celsius per minute to 2 degrees Celsius per minute), the absolute value of power switching device temperature information (e.g., reaching 80 degrees Celsius), and the duration of the partial discharge signal (e.g., lasting 10 minutes). For example, the weight of insulation margin is increased from 0.2 to 0.4, and the weight of thermal margin is increased from 0.45 to 0.5, to place greater emphasis on the thermal stress and aging risks of the winding and insulation system under long-term overload.

[0062] Ultimately, the system will perform a weighted fusion of thermal margin, core margin, and insulation margin based on the adjusted weight information, and combine this with the power switching margin, for example, a current power switching margin of 20%, for constraint correction. For instance, if the weighted fusion result is 70%, but the power switching margin is only 20%, the final instantaneous dynamic margin index may be corrected to 20% or a value slightly higher than 20%, to ensure that the weak links of the entire system are fully considered, thereby providing an accurate decision-making basis for subsequent physical response adjustments.

[0063] In another embodiment of this application, it is further proposed to determine whether a low-frequency transformer is in a short-circuit impulse condition or an overload operation condition based on the rate of change of instantaneous power, including: S2431: Perform spectrum analysis on the output current information to obtain the characteristics of high-frequency current components; S2432: Obtain the voltage sensor noise parameters corresponding to the output side voltage information and the current sensor noise parameters corresponding to the output side current information; S2433: Signal verification is performed based on the rate of change of instantaneous power, high-frequency current component characteristics, and noise parameters of voltage and current sensors. S2434: When the signal verification result is that the instantaneous power change rate meets the preset operating condition criterion, and the high-frequency current component characteristics, voltage sensor noise parameters and current sensor noise parameters are all within the corresponding preset normal range, the judgment result of short-circuit impact condition or overload operation condition is output. S2435: When the high-frequency current component characteristics, voltage sensor noise parameters, or current sensor noise parameters exceed the corresponding preset normal range, no judgment result is output and / or the judgment result is not allowed to trigger the adjustment of the first margin weight information or the second margin weight information.

[0064] Specifically, spectral analysis of output-side current information refers to converting the time-domain output-side current information into frequency-domain information using signal processing techniques such as Fourier transform, thereby identifying the various frequency components contained therein, especially high-frequency current components. The characteristics of high-frequency current components can be understood as parameters such as the amplitude, frequency, and phase of these high-frequency components. The purpose is to identify high-frequency interference that may be caused by harmonics, noise, or specific load behavior.

[0065] Among them, voltage sensor noise parameters and current sensor noise parameters refer to the statistical characteristics used to characterize the random noise or systematic errors generated by voltage and current sensors during the measurement process, such as the mean, variance, and power spectral density of the noise. These parameters can be obtained through sensor factory calibration data, historical operating data analysis, or real-time noise monitoring. Their purpose is to quantify the uncertainty of sensor measurements and provide a basis for subsequent signal verification.

[0066] In practical applications, signal verification refers to comprehensively considering the rate of change of instantaneous power, the characteristics of high-frequency current components, and sensor noise parameters, and performing cross-validation and consistency checks on these data through preset logical rules or algorithms. For example, it can determine whether the rate of change of instantaneous power matches the load impact type reflected by the characteristics of high-frequency current components, while eliminating misjudgments caused by sensor noise. Its purpose is to improve the accuracy and reliability of operating condition judgment.

[0067] Preset operating condition criteria refer to a set of judgment thresholds or conditions pre-set for short-circuit impact conditions and overload operation conditions. For example, a short-circuit impact condition may correspond to a sharp increase in the instantaneous power change rate exceeding a certain critical value, while an overload operation condition may correspond to an instantaneous power change rate that remains higher than a certain lower threshold.

[0068] The preset normal range refers to the acceptable numerical range set for the high-frequency current component characteristics, voltage sensor noise parameters, and current sensor noise parameters. When these parameters exceed their normal range, it indicates that there may be serious interference or sensor failure, and the instantaneous power change rate data may be unreliable. The system does not output judgment results and / or does not allow judgment results to trigger adjustments to the first or second margin weight information. This means that when signal verification detects abnormal or unreliable data, the system will pause or prevent condition judgments based on this data and subsequent margin weight adjustments to avoid adverse effects caused by erroneous judgments.

[0069] The solution presented in this application effectively improves the accuracy of low-frequency transformer condition judgment by introducing a multi-dimensional signal verification mechanism. In some preferred embodiments, a specific example is provided below for illustration: Assuming a low-frequency transformer is operating under an industrial load, this load may experience transient surges during startup or switching. To accurately determine whether the transformer is under short-circuit surge or overload conditions, the system first continuously monitors the output current. When a sudden increase in the instantaneous power change rate is detected, potentially indicating an impending surge, the system immediately initiates a signal verification process. Specifically, it first performs spectral analysis, such as Fast Fourier Transform (FFT), on the current output current to identify any abnormal high-frequency current components, such as harmonics or high-frequency noise.

[0070] Simultaneously, the system retrieves the noise parameters of the current voltage and current sensors, such as their root mean square noise values, from pre-stored sensor calibration data or real-time monitoring data. Subsequently, the system comprehensively verifies the instantaneous power change rate, the identified high-frequency current component characteristics, and the sensor noise parameters. For example, if the instantaneous power change rate meets the preset criteria for short-circuit impact, but spectrum analysis shows a large amount of high-frequency noise outside the normal range, and the sensor noise parameters also indicate that the sensor is in an abnormal state, then even if the instantaneous power change rate meets the criteria, the system will determine that the data is unreliable, thus not outputting a short-circuit impact condition judgment result and preventing the adjustment of the first margin weight information. Conversely, if the instantaneous power change rate meets the preset criteria, the high-frequency current component characteristics are within the normal range, and the sensor noise parameters also indicate that the sensor is working normally, then the system will be certain that this is a genuine short-circuit impact condition and output the corresponding judgment result, allowing subsequent margin weight adjustments. In this way, the system can effectively avoid misjudgments caused by false signals or sensor failures, ensuring the accuracy and safety of low-frequency transformer operation control.

[0071] In another embodiment of this application, the step of distributing and adjusting the active and reactive power output of the low-frequency transformer according to the instantaneous power demand change trend includes: S4100: Determine the target allocation ratio of active power and reactive power output by the low-frequency transformer based on the instantaneous power demand change trend. S4200: When the instantaneous dynamic margin index meets the preset margin constraint, the active power distribution of the low-frequency transformer is adjusted by controlling the control parameters of the power converter so that the active power distribution meets the target distribution ratio. S4300: When the instantaneous dynamic margin index meets the preset margin constraint, the reactive power distribution of the low-frequency transformer is adjusted by controlling the control parameters of the power converter, so that the reactive power distribution of the low-frequency transformer meets the reactive power distribution requirements corresponding to the target distribution ratio. S4400: Based on the current harmonic characteristics of the output current information, generate a harmonic suppression command and adjust the control parameters of the power converter to implement harmonic suppression, so that the amplitude of at least one preset target harmonic component in the output current information is within the corresponding preset amplitude suppression threshold range. S4500: When the instantaneous dynamic margin index does not meet the preset margin constraint, reduce the reactive power allocation and / or active power allocation, and / or limit the control gain corresponding to the harmonic suppression command.

[0072] Specifically, determining the target allocation ratio of active and reactive power output from a low-frequency transformer refers to calculating the ideal ratio of active and reactive power that the low-frequency transformer should provide under current or predicted load conditions, based on the instantaneous power demand trends of the load. This ratio can be derived from historical data, predictive models, or real-time optimization algorithms, with the aim of optimizing power transmission efficiency and system stability.

[0073] Specifically, when the instantaneous dynamic margin index meets the preset margin constraint, adjusting the active power allocation and reactive power allocation by controlling the control parameters of the power converter means that when the instantaneous dynamic margin index inside the low-frequency transformer is within a safe and acceptable range, the system adjusts the operating state of the power converter according to the target allocation ratio. For example, by changing its modulation depth, duty cycle, or phase angle, the active power allocation and reactive power allocation output by the low-frequency transformer are consistent with the target allocation ratio, thereby fully utilizing the transformer's available capacity while meeting load requirements.

[0074] In practical applications, harmonic suppression is implemented by generating harmonic suppression commands and adjusting the control parameters of the power converter based on the harmonic characteristics of the output current information. This means that the system monitors the current waveform on the output side of the low-frequency transformer in real time and identifies the harmonic components through methods such as spectrum analysis. When the harmonic level exceeds the preset threshold, a corresponding harmonic suppression command is generated, and the control parameters of the power converter are adjusted, such as by injecting reverse harmonic current or adjusting the switching mode, to cancel or weaken the harmonics. This ensures that the amplitude of at least one preset target harmonic component in the output current is suppressed within the corresponding preset amplitude suppression threshold range. The purpose is to improve power quality and protect the load equipment.

[0075] Furthermore, when the instantaneous dynamic margin index does not meet the preset margin constraint conditions, reducing the reactive power allocation and / or active power allocation, and / or limiting the control gain corresponding to the harmonic suppression command, means that when the low-frequency transformer's available margin is insufficient due to its internal state, the system prioritizes protective derating: by reducing the reactive power allocation and / or active power allocation of the low-frequency transformer output, the load is reduced, while the control gain corresponding to the harmonic suppression command is limited, avoiding additional stress caused by overcompensation when the margin is insufficient. Its purpose is to prioritize ensuring the operational safety and lifespan of the low-frequency transformer.

[0076] In some preferred embodiments, it is assumed that a low-frequency transformer is powering an industrial production line containing multiple large inductive loads with rapidly changing instantaneous power demands and significant harmonic currents.

[0077] First, the system predicts the instantaneous power demand trend based on real-time operating data and historical load patterns of the production line, and determines the target allocation ratio of active and reactive power output from the low-frequency transformer accordingly. For example, a higher reactive power compensation target is set when a sharp increase in reactive power demand is predicted. Simultaneously, the system continuously monitors winding temperature, core operating status, and power switching device temperature, and evaluates the instantaneous dynamic margin index. When the instantaneous dynamic margin index meets the preset margin constraints, the power converter adjusts control parameters, such as modulation depth, duty cycle, or phase angle, according to the target allocation ratio to precisely adjust the active and reactive power allocation of the low-frequency transformer output to meet the instantaneous load demand and implement reactive power compensation. Simultaneously, the system generates harmonic suppression commands based on the current harmonic characteristics of the output current information, adjusts the power converter's control parameters, and actively injects reverse harmonic current to suppress the amplitudes of the 5th and 7th harmonic components in the output current information within the preset amplitude suppression threshold range to ensure power quality.

[0078] Subsequently, if a short circuit or severe overload suddenly occurs on the production line, causing the winding temperature to rise rapidly and the magnetic flux density of the core to approach saturation, resulting in a rapid decrease in the instantaneous dynamic margin index and failure to meet the preset margin constraint conditions, the system will immediately reduce the reactive power allocation and / or active power allocation to alleviate the load and limit the control gain corresponding to the harmonic suppression command. This avoids excessive harmonic suppression when the margin is insufficient, which would increase the operating burden. In this way, the system can protect the low-frequency transformer and maintain the overall stable operation of the system while ensuring basic power supply.

[0079] In another embodiment of this application, it is further proposed to determine the target allocation ratio of active power to reactive power output by the low-frequency transformer, specifically including: S4110: Determine the target reactive power compensation amount based on the instantaneous power demand change trend, and determine the target active power support amount based on the deviation between the output side voltage information and the preset voltage reference. S4120: When the instantaneous dynamic margin index meets the preset margin constraint conditions, the target allocation ratio is determined based on the ratio of the reactive power target compensation amount to the active power target support amount. S4130: When the instantaneous dynamic margin index does not meet the preset margin constraint, the reactive power target compensation amount and / or active power target support amount shall be reduced synchronously according to the preset derating factor in order to update the target allocation ratio.

[0080] Specifically, the reactive power target compensation amount refers to the amount of reactive power that needs to be provided by the low-frequency transformer, calculated based on the instantaneous power demand trend of the load, such as the rate of change of instantaneous reactive power or the characteristics of high-frequency current components, in order to maintain system power balance or suppress voltage fluctuations. Its purpose is to respond to the reactive power demand of the load and provide necessary reactive power support. The active power target support amount refers to the amount of active power that needs to be provided by the low-frequency transformer, calculated based on the deviation between the output voltage information and the preset voltage reference, such as voltage dips or overvoltage conditions, in order to stabilize the output voltage. Its purpose is to maintain voltage stability through active power regulation.

[0081] The instantaneous dynamic margin index is a comprehensive indicator characterizing the current ability of a low-frequency transformer to withstand instantaneous impacts. Meeting the preset margin constraints means that the low-frequency transformer has sufficient capacity and stability to cope with current or impending load impacts. When the instantaneous dynamic margin index meets the preset margin constraints, the target allocation ratio is determined based on the ratio of the reactive power target compensation to the active power target support, in order to fully utilize the capacity of the low-frequency transformer and improve the response effect.

[0082] In practical applications, when the instantaneous dynamic margin index does not meet the preset margin constraints, it indicates that the low-frequency transformer may be overloaded, overheated, or approaching its operating limits. In this case, the reactive power target compensation and / or active power target support are simultaneously reduced according to a preset derating factor to update the target allocation ratio. The preset derating factor is a value less than 1, such as 0.8 or 0.9, and its value can be dynamically adjusted based on the low-frequency transformer's design parameters, historical operating data, and real-time operating status. By reducing the reactive power target compensation and / or active power target support, the operating burden of the low-frequency transformer is alleviated, preventing equipment damage or system instability caused by overload or over-impact. Updating the target allocation ratio includes recalculating the target allocation ratio, allowing it to remain unchanged or change, to ensure that the update process is consistent with the derating method of the reactive power target compensation and / or active power target support.

[0083] In some preferred embodiments, the following specific example illustrates the situation: Suppose that during the operation of a low-frequency transformer on an industrial production line, the output voltage information shows a slight drop, while the power information analysis indicates that the instantaneous power demand of the load foreshadows a large reactive power surge.

[0084] First, the system calculates the reactive power target compensation amount of 200kVar based on the instantaneous power demand change trend. At the same time, based on the deviation between the output voltage information and the preset voltage reference, it calculates the active power target support amount of 50kW.

[0085] Next, the system evaluates the instantaneous dynamic margin index of the low-frequency transformer.

[0086] Scenario 1: If the instantaneous dynamic margin index meets the preset margin constraint, it indicates that the transformer currently has sufficient capacity to cope with the impact. In this case, the system will determine the target allocation ratio of active power to reactive power as 1:4 based on the ratio of 200kVar to 50kW.

[0087] Scenario 2: If the instantaneous dynamic margin index does not meet the preset margin constraint conditions, for example, if the winding temperature information or core operating status information shows that the transformer is close to its thermal limit or magnetic saturation point, indicating that the transformer's capacity is limited, the system will simultaneously reduce the reactive power target compensation and active power target support by a preset derating factor of 0.7. The updated reactive power target compensation becomes 200kVar × 0.7 = 140kVar, and the active power target support becomes 50kW × 0.7 = 35kW. Subsequently, the system will update the target allocation ratio to 1:4 based on the ratio of 140kVar to 35kW.

[0088] Reference Figure 2 The specific embodiments of this application also disclose a low-frequency transformer operation control system, including: The power information acquisition module 1 is used to acquire power information on the output side of the low-frequency transformer, identify the instantaneous power demand change trend of the load based on the power information, and predict load impact. The power information includes output side voltage information and output side current information. The operating status acquisition module 2 is used to acquire the first operating status information inside the low-frequency transformer, and to evaluate the current ability of the low-frequency transformer to withstand instantaneous impact based on the first operating status information, so as to obtain an instantaneous dynamic margin index characterizing the withstand capability. The first operating status information includes winding temperature information, magnetic core operating status information and / or power switching device temperature information. The physical response adjustment module 3 is used to adjust the physical response characteristics of the low-frequency transformer in response to load shocks and instantaneous dynamic margin indicators before the load shock occurs, so as to provide additional voltage support. The adjustment of the physical response characteristics of the low-frequency transformer includes: adjusting the excitation voltage, adjusting the switching frequency and / or control parameters of the power converter associated with the low-frequency transformer. The power distribution adjustment module 4 is used to distribute and adjust the active power and reactive power output by the low-frequency transformer according to the instantaneous power demand change trend. The distribution adjustment includes: implementing reactive power compensation control according to the instantaneous power demand change trend, and / or implementing harmonic suppression according to the current harmonic characteristics of the low-frequency transformer output side.

[0089] This application aims to accurately acquire and analyze power information and internal operating status information through the power information acquisition module 1 and the operating status acquisition module 2, combined with the prediction of load impact and the assessment of transformer withstand capacity by the physical response adjustment module 3, to actively adjust the physical response characteristics of the transformer before the load impact occurs, and to intelligently allocate and adjust active power and reactive power through the power distribution adjustment module 4. This effectively solves the problem of decreased control performance caused by sensor aging, feedforward model failure and adaptive program misjudgment in the prior art, and significantly improves the operating stability and response speed of low frequency transformers under complex operating conditions.

[0090] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for controlling the operation of a low-frequency transformer, characterized in that, The method includes: The electrical quantity information of the output side of the low-frequency transformer is obtained, and the instantaneous power demand change trend of the load is identified based on the electrical quantity information in order to predict the load impact. The electrical quantity information includes output side voltage information and output side current information. The first operating status information inside the low-frequency transformer is obtained, and the current ability of the low-frequency transformer to withstand instantaneous impact is evaluated based on the first operating status information to obtain an instantaneous dynamic margin index characterizing the withstand capability. The first operating status information includes winding temperature information, core operating status information and / or power switching device temperature information. In response to the load surge and the instantaneous dynamic margin index, the physical response characteristics of the low-frequency transformer are adjusted before the load surge occurs to provide additional voltage support. The adjustment of the physical response characteristics of the low-frequency transformer includes: adjusting the excitation voltage, adjusting the switching frequency and / or control parameters of the power converter associated with the low-frequency transformer. Based on the instantaneous power demand change trend, the active power and reactive power output of the low-frequency transformer are allocated and adjusted. The allocation and adjustment includes: implementing reactive power compensation control based on the instantaneous power demand change trend, and / or implementing harmonic suppression based on the current harmonic characteristics of the low-frequency transformer output side.

2. The low-frequency transformer operation control method according to claim 1, characterized in that, The method of adjusting the physical response characteristics of the low-frequency transformer in response to the load surge and the instantaneous dynamic margin index before the load surge occurs to provide additional voltage support includes: Spectral analysis is performed on the output-side current information to identify high-frequency current component characteristics; Vibration signals and local temperature data inside a low-frequency transformer are acquired to assess the resonance risk inside the transformer, and thermal stress indices characterizing thermal stress are determined based on the local temperature data. When the instantaneous dynamic margin index meets the preset margin triggering condition, and before the load impact occurs, the switching frequency of the power converter is adjusted according to the high-frequency current component characteristics, the resonance risk, the thermal stress index, and the inherent resonant frequency of the low-frequency transformer, thereby providing additional voltage support to suppress low-frequency reactive power impact and reduce the resonance risk caused by the switching frequency of the power converter and the frequency of the high-frequency current component and / or the inherent resonant frequency. When the resonance risk still meets the preset risk triggering conditions, the control parameters of the power converter are adjusted.

3. The low-frequency transformer operation control method according to claim 1, characterized in that, The step of identifying the instantaneous power demand change trend of the load based on the power information to predict load surges includes: Obtain the second operating status information of the load, and identify the operating mode of the load based on the second operating status information; The instantaneous reactive power and its rate of change are calculated based on the output-side voltage information and the output-side current information to characterize the trend of instantaneous power demand change. Spectral analysis is performed on the output-side current information to extract high-frequency current component features; The analysis results are obtained by jointly judging the operating mode, the rate of change of instantaneous reactive power, and the characteristics of high-frequency current components, and by analyzing whether the low-frequency reactive power impact reflected by the rate of change of instantaneous reactive power and the characteristics of high-frequency current components are consistent with the operating mode, based on the correlation rules between the operating mode and the pre-stored power characteristics. When the analysis results are consistent, a warning signal characterizing the load impact is generated and output, the warning signal including indication information that the load impact is about to occur; When the rate of change of instantaneous reactive power is detected to meet the preset low-frequency reactive power impact criterion, and the analysis results are inconsistent, and the high-frequency current component characteristics match the high-frequency interference characteristics corresponding to the operating mode, the warning signal is suppressed. Suppressing the warning signal includes not outputting the warning signal and / or not allowing the warning signal to trigger the adjustment of the physical response characteristics of the low-frequency transformer.

4. The low-frequency transformer operation control method according to claim 1, characterized in that, The step of assessing the low-frequency transformer's current ability to withstand instantaneous impacts based on the first operating status information, in order to obtain an instantaneous dynamic margin index characterizing the withstand capability, includes: Obtain the first historical calibration data of the internal sensor corresponding to the first operating status information; Obtain the operating environment parameters of the internal sensors; Based on the first historical calibration data, the working environment parameters, and the type of internal sensor, the first operating status information is corrected to compensate for nonlinear drift and measurement deviation caused by long-term operation of the internal sensor. The ability of the low-frequency transformer to withstand instantaneous impacts is assessed based on the corrected first operating status information, and the instantaneous dynamic margin index is determined accordingly.

5. The low-frequency transformer operation control method according to claim 1, characterized in that, The step of identifying the instantaneous power demand change trend of the load based on the power information includes: Obtain the voltage sensor environmental parameters corresponding to the output-side voltage information and the current sensor environmental parameters corresponding to the output-side current information; Acquire second historical calibration data for the voltage and current sensors; Based on the environmental parameters of the voltage sensor, the environmental parameters of the current sensor, the second historical calibration data, and the types of the voltage sensor and the current sensor, the output voltage information and the output current information are corrected to compensate for measurement deviations caused by sensor nonlinear drift or random noise. The instantaneous reactive power is calculated based on the corrected output-side voltage information and the corrected output-side current information. The instantaneous reactive power is subjected to adaptive filtering. The instantaneous power demand change trend is identified based on the rate of change of the filtered instantaneous reactive power.

6. The low-frequency transformer operation control method according to claim 4, characterized in that, The step of assessing the low-frequency transformer's ability to withstand instantaneous impacts based on the corrected first operating status information, and determining the instantaneous dynamic margin index accordingly, includes: Acquire partial discharge signals that characterize the insulation state of low-frequency transformers; The thermal margin is determined based on the corrected winding temperature information, the core margin is determined based on the corrected core operating status information, the power switch margin is determined based on the corrected power switch device temperature information, and the insulation margin is determined based on the partial discharge signal. The instantaneous power is calculated based on the output voltage information and the output current information, and the low-frequency transformer is judged to be in short-circuit impact condition or overload operation condition based on the rate of change of the instantaneous power. When it is determined that the short-circuit impact condition is underway, the first margin weighting information of thermal margin and magnetic core margin is adjusted according to the rate of change of magnetic core flux density information in the magnetic core working state information, the rate of rise of temperature information of power switching device and the intensity of partial discharge signal. When it is determined that the overload operation condition is in effect, the second margin weighting information of thermal margin and insulation margin is adjusted according to the rising rate of the winding temperature information, the absolute value of the power switching device temperature information, and the duration of the partial discharge signal. Based on the adjusted first margin weight information or the adjusted second margin weight information, the thermal margin, the core margin and the insulation margin are weighted and fused to obtain a weighted fusion result. The weighted fusion result is then constrained and corrected based on the power switch margin to determine the instantaneous dynamic margin index.

7. The low-frequency transformer operation control method according to claim 6, characterized in that, The step of determining whether a low-frequency transformer is in a short-circuit impact condition or an overload operation condition based on the rate of change of instantaneous power includes: Spectral analysis is performed on the output-side current information to obtain high-frequency current component characteristics; Obtain the voltage sensor noise parameters corresponding to the output-side voltage information and the current sensor noise parameters corresponding to the output-side current information; Signal verification is performed based on the instantaneous power change rate, the high-frequency current component characteristics, and the noise parameters of the voltage sensor and the current sensor. When the signal verification result is that the rate of change of instantaneous power meets the preset operating condition criteria, and the high-frequency current component characteristics, the voltage sensor noise parameter and the current sensor noise parameter are all within the corresponding preset normal range, the judgment result of the short-circuit impact condition or the overload operation condition is output. When the high-frequency current component characteristics, the voltage sensor noise parameter, or the current sensor noise parameter exceed the corresponding preset normal range, the determination result is not output and / or the determination result is not allowed to trigger the adjustment of the first margin weight information or the second margin weight information.

8. The low-frequency transformer operation control method according to claim 1, characterized in that, The method of distributing and adjusting the active and reactive power output of the low-frequency transformer according to the instantaneous power demand change trend includes: Based on the instantaneous power demand change trend, determine the target allocation ratio of active power and reactive power output by the low-frequency transformer; When the instantaneous dynamic margin index meets the preset margin constraint, the active power distribution of the low-frequency transformer is adjusted by controlling the control parameters of the power converter so that the active power distribution meets the target distribution ratio. When the instantaneous dynamic margin index meets the preset margin constraint, the reactive power distribution of the low-frequency transformer is adjusted by controlling the control parameters of the power converter so that the reactive power distribution of the low-frequency transformer meets the reactive power distribution requirements corresponding to the target distribution ratio. Based on the current harmonic characteristics of the output current information, a harmonic suppression command is generated, and the control parameters of the power converter are adjusted to implement harmonic suppression, so that the amplitude of at least one preset target harmonic component in the output current information is within the corresponding preset amplitude suppression threshold range. When the instantaneous dynamic margin index does not meet the preset margin constraint, the reactive power allocation and / or the active power allocation are reduced, and / or the control gain corresponding to the harmonic suppression command is limited.

9. The low-frequency transformer operation control method according to claim 8, characterized in that, Determining the target allocation ratio of active power to reactive power output from the low-frequency transformer includes: The reactive power target compensation amount is determined based on the instantaneous power demand change trend, and the active power target support amount is determined based on the deviation between the output side voltage information and the preset voltage reference. When the instantaneous dynamic margin index meets the preset margin constraint, the target allocation ratio is determined based on the ratio of the reactive power target compensation amount to the active power target support amount. When the instantaneous dynamic margin index does not meet the preset margin constraint, the reactive power target compensation amount and / or the active power target support amount are reduced synchronously according to the preset derating coefficient to update the target allocation ratio.

10. A low-frequency transformer operation control system, characterized in that, The system includes: The power information acquisition module is used to acquire power information on the output side of the low-frequency transformer, identify the instantaneous power demand change trend of the load based on the power information, and predict load impact. The power information includes output side voltage information and output side current information. The operating status acquisition module is used to acquire the first operating status information inside the low-frequency transformer, and to evaluate the current ability of the low-frequency transformer to withstand instantaneous impact based on the first operating status information, so as to obtain an instantaneous dynamic margin index characterizing the withstand capability. The first operating status information includes winding temperature information, magnetic core operating status information and / or power switching device temperature information. The physical response adjustment module is used to adjust the physical response characteristics of the low-frequency transformer in response to the load impact and the instantaneous dynamic margin index before the load impact occurs, so as to provide additional voltage support. The adjustment of the physical response characteristics of the low-frequency transformer includes: adjusting the excitation voltage, adjusting the switching frequency and / or control parameters of the power converter associated with the low-frequency transformer. The power distribution adjustment module is used to distribute and adjust the active power and reactive power output by the low-frequency transformer according to the instantaneous power demand change trend. The distribution adjustment includes: implementing reactive power compensation control according to the instantaneous power demand change trend, and / or implementing harmonic suppression according to the current harmonic characteristics of the low-frequency transformer output side.

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