Saturation-resistant current transformer based on virtual air-gap magnetic circuit design and control method thereof

Abstract

The application discloses an anti-saturation current transformer based on a virtual air gap magnetic circuit design and a control method thereof. The transformer comprises a core, a primary winding, a secondary winding, a compensation winding, a detection unit, a control unit and a power driving unit. The primary winding and the secondary winding are wound on the core to perform normal current transformation. The compensation winding is wound on the core. The detection unit and the control unit obtain a detection signal and extract a magnetic bias feedback, calculate a compensation ampere-turn instruction and convert the compensation ampere-turn instruction into a compensation current instruction to generate a PWM. The power driving unit drives a power inverter circuit based on the PWM to make the compensation winding generate a compensation magnetic potential which is equal in amplitude and opposite in direction to the magnetic bias potential, thereby offsetting the magnetic flux working point deviation caused by the magnetic bias. The application can realize the anti-saturation effect of the equivalent virtual air gap without introducing a physical air gap, can significantly improve the anti-saturation capability of the transformer under the DC magnetic bias working condition, and can maintain the transformation precision under the normal power frequency measurement condition.

Description

Technical Field

[0001] This invention belongs to the field of magnetic circuit design, measurement and protection technology of current transformers, and relates to an anti-saturation current transformer based on virtual air gap magnetic circuit design and its control method. Background Technology

[0002] In DC industrial load scenarios such as high-voltage direct current (HVDC) transmission, urban rail transit traction power supply, and electrolytic plating, the primary current, in addition to the power frequency AC component, often has a non-negligible DC component or low-frequency bias component. The bias originates from factors including converter control strategies, fluctuations in the operating status of the traction rectifier, DC load start-up and shutdown, and imbalance faults. For traditional closed-core current transformers, the DC bias is equivalent to an additional magnetomotive force, causing the core flux operating point to shift unidirectionally along the magnetization curve, resulting in a decrease in effective permeability and premature entry into the saturation region. After saturation, the transformer's secondary current will exhibit distortion phenomena such as amplitude attenuation, waveform clipping, and phase shift, leading to amplified metering errors, inaccurate protection settings, and increased risks of relay protection maloperation / failure to operate. Under severe operating conditions, it may also cause reliability issues such as secondary-side overheating and accelerated insulation aging, affecting the long-term stable operation of the system.

[0003] In existing technologies, physical air gaps are typically created in the iron core to reduce the equivalent magnetic permeability of the magnetic circuit in order to improve the saturation threshold. However, physical air gaps significantly increase the excitation current demand, leading to increased transformer ratio and phase errors, making it difficult to meet the requirements of high-precision metering or high-sensitivity protection. Furthermore, the consistency of air gap fabrication and assembly is difficult to guarantee, easily introducing discrete errors and temperature drift issues. Additionally, it reduces the structural strength of the iron core, increases leakage flux, and deteriorates electromagnetic compatibility. For high-current, large dynamic range applications, physical air gaps also increase volume and weight, increasing the difficulty of on-site installation and maintenance, and raising overall costs. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an anti-saturation current transformer and its control method based on a "virtual air gap" magnetic circuit design. By adding a compensation winding and coordinating detection and closed-loop control, a compensation ampere-turn with equal amplitude and opposite direction to the bias magnetomotive force is actively generated, keeping the main core operating point in the linear region, thereby obtaining the anti-saturation capability of an equivalent "virtual air gap".

[0005] The present invention adopts the following technical solution.

[0006] An anti-saturation current transformer based on virtual air gap magnetic circuit design, the anti-saturation current transformer includes an iron core, a primary winding, a secondary winding, a compensation winding, a detection unit, a control unit, and a power drive unit; The primary and secondary windings are wound on the iron core and are used for the normal transmission of the measured current. The compensation winding is wound on the iron core and does not participate in the normal transmission of the measured current. The detection unit and the control unit are connected to acquire detection signals characterizing the core flux bias, magnetic density bias and / or excitation current components, extract the bias feedback quantity based on the detection signals, calculate the compensation ampere-turn command based on the deviation between the bias feedback quantity and the target value, and convert the compensation ampere-turn command into a compensation current command to generate a PWM drive signal. The power drive unit is used to drive the power inverter circuit based on the PWM drive signal, so that the compensation winding outputs a compensation current and generates a compensation magnetomotive force that is equal in amplitude and opposite in direction to the bias magnetomotive force, so as to counteract the magnetic flux operating point offset caused by the bias magnetomotive force, so that the iron core works in the linear region and realizes the equivalent virtual air gap anti-saturation.

[0007] Preferably, the compensation winding is disposed in the winding window area of ​​the iron core and is wound on the same column and in the same window as the secondary winding, located on the outside or inside of the secondary winding. Furthermore, an insulating isolation layer and / or a shielding layer are provided between the compensation winding and the secondary winding to achieve electrical isolation between the compensation winding and the secondary winding and reduce the coupling interference of the compensation high-frequency drive to the secondary side.

[0008] Preferably, the number of turns of the compensation winding Based on the maximum uncompensated bias ampere-turns The power drive unit allows a maximum compensation current. The equivalent magnetic coupling coefficient between the compensating winding and the iron core and safety margin coefficient Determined, satisfies:

[0009] And the cross-sectional area of ​​the conductor of the compensation winding Based on the maximum compensation current and the allowable current density Confirmed, satisfied:

[0010] Wherein, the safety margin coefficient The equivalent magnetic coupling coefficient is greater than 1. The coupling efficiency coefficient is used to compensate for the effect of the winding magnetomotive force on the main magnetic circuit of the iron core.

[0011] Preferably, the detection unit includes a detection winding, which collects induced voltage and inputs it to the control unit as a detection signal characterizing the magnetic flux bias of the iron core. The control unit integrates and corrects the drift of the induced voltage to obtain a magnetic flux estimate, and extracts its bias component as the bias feedback quantity.

[0012]

[0013] in, To detect the induced voltage in the winding, To detect the number of turns in the winding, The sampling period is For the first The magnetic flux estimate at each sampling time. The drift suppression leakage coefficient; , The rate of change threshold; , These are the upper and lower limits of the leakage coefficient, respectively; The rate of change of the induced voltage in the winding is detected at adjacent sampling times.

[0014] Preferably, the detection unit includes a magnetic field sensor, which is used to acquire the magnetic flux density signal of the iron core as a raw detection signal characterizing the magnetic flux density bias of the iron core and output it to the control unit. The control unit is used to extract the bias component of the magnetic flux density signal to obtain the magnetic flux density bias component as the bias feedback quantity.

[0015] Preferably, the magnetic field sensor is one or more of a Hall sensor, a magnetoresistive sensor, or a fluxgate sensor.

[0016] Preferably, the detection unit includes a primary current detection module and a secondary current detection module, used to acquire the primary current of the primary winding and the secondary current of the secondary winding as raw detection signals and output them to the control unit; The control unit is used to estimate the excitation current based on the primary current and the secondary current, and to extract the DC and / or low-frequency components of the excitation current as the bias feedback quantity. The formula for estimating the excitation current is:

[0017] in, The primary current of the primary winding, This refers to the secondary current of the secondary winding. The number of turns in a primary winding. The number of turns in the secondary winding. The obtained excitation current is used for estimation.

[0018] Preferably, the control unit includes a state estimation module, a biased magnetic outer loop controller, a compensation current inner loop, and a PWM generation module; The state estimation module is used to perform magnetic flux state, magnetic density state and / or excitation current state estimation based on the original detection signal output by the detection unit, and extract the corresponding bias feedback quantity. The bias magnetic field outer-loop controller is configured to calculate the compensation ampere-turn command according to the deviation between the bias magnetic field feedback amount and the target value ; The compensation current inner loop is configured to convert the compensation ampere-turn command into a compensation current command according to the number of turns of the compensation winding , and compare the compensation current command with the fed-back compensation current , and generate a PWM driving quantity according to the current deviation obtained by comparison; The PWM generation module is configured to output a PWM driving signal based on the PWM driving quantity.

[0019] Preferably, the power driving unit comprises an isolation driving circuit, a full-bridge or half-bridge power inverter circuit and a current sampling circuit; The isolation driving circuit is configured to drive the full-bridge or half-bridge power inverter circuit according to the PWM driving signal; The full-bridge or half-bridge power inverter circuit is configured to convert the DC bus voltage into a bidirectional compensation current, and output the compensation current to the compensation winding, so that the compensation winding outputs the compensation current to generate a compensation magnetomotive force opposite to the direction of the bias magnetic field magnetomotive force; The current sampling circuit is configured to perform sampling on the compensation current, and input the sampling result to the compensation current inner loop of the control unit to perform closed-loop correction of the compensation current.

[0020] Preferably, the control unit is provided with a transparent constraint, the transparent constraint acts on the compensation control channel, and the compensation control channel comprises a control link from the extraction of the bias magnetic field feedback amount to the generation of the compensation current command; the transparent constraint comprises at least one of the following: Performing low-pass filtering on the compensation control channel; Setting notch / band-stop filtering for the power frequency component in the compensation control channel; Performing bandwidth limitation on the compensation current command.

[0021] Preferably, the control unit is provided with a hierarchical response strategy, and the hierarchical response strategy is realized by changing the compensation ampere-turn command, comprising: When | | < T1, no compensation or micro-compensation is performed, and the compensation ampere-turn command satisfies:

[0022] wherein is the micro-compensation gain; is the deviation between the bias magnetic field feedback amount and the target value; T1 is the first threshold; When T1 ≤ | ∣<T2, proportional enhancement compensation is performed, and the compensated ampere-turn instruction satisfies:

[0023] wherein and are enhancement compensation coefficients; T2 is the second threshold; When ∣ ∣≥T2, strong compensation is entered and the compensation current is limited, and the compensated ampere-turn instruction satisfies:

[0024] wherein and are strong compensation coefficients, is the compensated ampere-turn limit value.

[0025] A control method for the anti-saturation current transformer based on virtual air-gap magnetic circuit design comprises the following steps: S1: The detection unit acquires an original detection signal characterizing core magnetic flux bias, magnetic density bias and / or excitation current component, and sends the original detection signal to the control unit; S2: The control unit obtains a bias magnetic feedback quantity according to the original detection signal; S3: The bias magnetic outer loop controller of the control unit calculates and outputs a compensated ampere-turn instruction according to the deviation between the bias magnetic feedback quantity and a target value; S4: The compensation current inner loop of the control unit converts the compensated ampere-turn instruction into a compensation current instruction, compares the compensation current instruction with the fed-back compensation current, generates a PWM drive signal according to the comparison result, drives the power inverter circuit, enables the compensation winding to output the compensation current, generates a compensation magnetomotive force opposite to the direction of the bias magnetomotive force, and offsets the magnetic flux working point offset caused by bias magnetism.

[0026] Preferably, the original detection signals of the magnetic flux bias and the excitation current component are acquired simultaneously, and the respective bias magnetic feedback quantities are extracted; when the difference between the two corresponding bias magnetic feedback quantities exceeds a preset threshold, an alarm is output and a degraded compensation mode or a compensation deactivation mode is entered; wherein, the degraded compensation mode is: only retaining the bias magnetic feedback quantity based on the excitation current, calculating the compensated ampere-turn instruction, and imposing a limit on the compensation current instruction; The compensation deactivation mode is: turning off the PWM drive signal and stopping the power inverter circuit from outputting the compensation current.

[0027] Preferably, the method further comprises: When the sampled value of the output compensation current of the compensation winding exceeds a preset overcurrent threshold, limiting the compensation current instruction and reducing the compensation output; When the magnetic flux bias detection or magnetic density bias detection signal is lost, abnormally saturated, or the magnetic flux estimation drift exceeds the preset drift threshold, the corresponding bias outer loop is stopped and the degradation compensation mode based on the excitation current component is switched. When the excitation current detection also becomes abnormal, or the above abnormality lasts for more than the preset duration, or a hardware failure occurs, the compensation output is disabled and an alarm signal is output, so that the current transformer enters the uncompensated safe operation state.

[0028] A terminal includes a processor and a storage medium; the storage medium is used to store instructions; the processor is used to perform operations according to the instructions to execute the steps of the method.

[0029] A computer-readable storage medium having a computer program stored thereon that, when executed by a processor, implements the steps of the method.

[0030] Compared with the prior art, the beneficial effects of the present invention include at least the following: This invention acquires detection signals characterizing the core magnetic flux bias, magnetic density bias, and / or excitation current components through a detection unit. The control unit calculates a compensation ampere-turn command based on the deviation between the bias feedback and the target value, and converts it into a compensation current command to generate a PWM drive signal. The power drive unit outputs a compensation magnetomotive force opposite to the bias magnetomotive force based on the PWM drive compensation winding, so that the core operates in the linear region, achieving equivalent virtual air gap anti-saturation. At the same time, by setting transparent constraints on the compensation control channel, the compensation mainly acts on the DC and / or low-frequency bias components, thereby maintaining transmission accuracy under normal power frequency measurement conditions.

[0031] This invention utilizes an active magnetic field compensation system comprised of a detection unit, a control unit, a power drive unit, and a compensation winding to achieve an anti-saturation effect of an equivalent virtual air gap without introducing a physical air gap. This significantly improves the anti-saturation capability of current transformers under DC bias conditions and maintains transmission accuracy under normal power frequency measurement conditions. It is suitable for HVDC DC bias measurement and protection, rail transit traction current measurement, and DC industrial load metering and monitoring scenarios such as electrolysis / electroplating.

[0032] This invention relates to an anti-saturation current transformer and its control method that can suppress the effects of DC / low-frequency bias without introducing a physical air gap in the iron core. It can detect the shift of the iron core magnetic flux operating point in real time when bias occurs and actively generate an equivalent compensation magnetomotive force, so that the iron core can work in the linear region for a long time. At the same time, it remains transparent to the normal transmission of power frequency and its harmonics, without reducing the original measurement accuracy. It also has the characteristics of fast response, stability and reliability, and ease of engineering implementation and maintenance, so as to meet the application requirements of metering and protection in complex DC bias scenarios.

[0033] This invention provides a parameterized calculation relationship between the number of turns in the compensation winding and the cross-sectional area of ​​the conductor. Specifically, the number of turns in the compensation winding is associated with the maximum ampere-turns of the bias to be compensated, the maximum allowable compensation current of the power drive unit, the equivalent magnetic coupling coefficient, and the safety margin coefficient. The cross-sectional area of ​​the conductor is associated with the maximum compensation current and the allowable current density. This allows the number of turns in the compensation winding and the cross-sectional area of ​​the conductor to be directly matched with the bias compensation requirements and driving capability, thereby improving the determinism, engineering adaptability, feasibility, and compensation efficiency of the parameter design.

[0034] This invention integrates and corrects the induced voltage, and adaptively adjusts the drift suppression leakage coefficient according to the rate of change of the induced voltage at adjacent sampling times. This can balance the anti-drift stability during long-term operation with the sensitivity of bias magnetic component extraction, thereby improving the reliability of bias magnetic detection under complex working conditions. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the overall structure of the anti-saturation current transformer of the present invention.

[0036] Figure 2 This is the composition of the detection unit, control unit, and power drive unit of the present invention.

[0037] Figure 3 This is a schematic diagram illustrating the principle of how DC bias causes the magnetic flux operating point to shift and how compensation ampere-turns cancel each other out to form a "virtual air gap".

[0038] Figure 4 This is a flowchart of the control strategy and method of the present invention.

[0039] Figure 1 and Figure 2 The reference numerals in the attached diagram are as follows: 100-Anti-saturation current transformer body; 110-Iron core; 120-Primary winding; 130-Secondary winding; 140-Compensation winding; 150-Detection unit; 160-Control unit; 170-Power drive unit. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0041] Embodiment 1 of this invention addresses the problem that in scenarios such as DC power transmission, rail transit traction, electrolytic plating, and electrolytic hydrogen production, the presence of DC or low-frequency bias components in the primary current causes the magnetic flux operating point of a traditional closed-core 110 current transformer to shift and enter deep saturation, leading to secondary current distortion, increased error, or even failure. This invention provides an anti-saturation current transformer based on a virtual air-gap magnetic circuit design. This is achieved by adding a compensation winding 140 driven by a high-frequency inverter power circuit outside the primary winding 120 and secondary winding 130. The compensation winding 140 does not participate in normal current transmission; the current is acquired in real time through a detection unit 150. The 110 core is characterized by magnetic flux / magnetic density or excitation current. A high-speed closed-loop negative feedback control system, consisting of a state estimation module and a digital controller (outer bias loop controller, inner compensation current loop), is constructed to address DC and low-frequency bias components. When the magnetic flux deviation caused by bias approaches the saturation threshold, the control circuit calculates and injects a compensation ampere-turn with equal amplitude and opposite direction to the bias magnetomotive force, keeping the operating point of the 110 core in the linear region. This achieves anti-saturation capability with an equivalent virtual air gap without introducing a physical air gap. Simultaneously, transparent constraints are set for the AC current components at power frequency and higher orders, without affecting normal transmission accuracy. This system is suitable for DC bias measurement and protection in DC power transmission, traction current measurement in rail transit, and DC industrial load metering and monitoring in electrolysis / electroplating, etc. Figure 1 As shown, the dashed box contains the anti-saturation current transformer body 100, which includes an iron core 110, a primary winding 120, a secondary winding 130, a compensation winding 140, and a detection winding. Outside the dashed box are a detection unit 150, a control unit 160, a power drive unit 170, and a metering / protection device connected to the anti-saturation current transformer body 100.

[0042] In this embodiment, the anti-saturation current transformer body 100 is used to maintain normal transmission capability when there is a DC component or low-frequency bias component in the primary current, so as to avoid the iron core 110 from entering deep saturation, which would lead to distortion of the secondary current waveform, increased error, or even failure of the transformer.

[0043] The primary winding 120 and the secondary winding 130 are wound on the iron core 110 to form a closed magnetic circuit for normal transmission of the measured current; the primary winding 120 is connected in series to the measured circuit, and the secondary winding 130 is connected to a metering or protection device to output a secondary current signal. The compensation winding 140 is wound on the iron core 110 and does not participate in the normal transmission of the measured current. It is only driven by the power drive unit 170 to output the compensation current to generate the compensation magnetomotive force when the bias magnetism occurs. More preferably, the spatial arrangement of the compensation winding 140, the primary winding 120, and the secondary winding 130 on the iron core 110 is such that the compensation winding 140 is set in the winding window area of ​​the iron core 110 and can be wound on the same column and in the same window as the secondary winding 130 to improve the control efficiency of the magnetic flux of the iron core 110. The compensation winding 140 is located outside or inside the secondary winding 130. Furthermore, an insulating layer and / or a shielding layer are provided between the compensation winding 140 and the secondary winding 130 to achieve electrical isolation between the compensation winding 140 and the secondary winding 130 and reduce the coupling interference of the compensation high-frequency drive to the secondary side.

[0044] Optionally, the number of turns of the compensation winding 140 is selected based on the maximum magnetomotive force to be canceled and the power drive capability. Furthermore, the cross-sectional area of ​​the 140mm conductor in the compensation winding is selected based on the maximum compensation current and the allowable current density, with copper conductors or copper busbars preferred, while also meeting the requirements for temperature rise and insulation level.

[0045] Preferably, the number of turns of the compensating winding 140 Based on the maximum uncompensated bias ampere-turns The power drive unit allows a maximum compensation current. The equivalent magnetic coupling coefficient between the compensating winding and the iron core and safety margin coefficient Confirmed, satisfied:

[0046] And the conductor cross-sectional area of ​​the compensation winding 140 Based on the maximum compensation current and the allowable current density Confirmed, satisfied:

[0047] Wherein, the safety margin coefficient The equivalent magnetic coupling coefficient is greater than 1. The coupling efficiency coefficient is used to compensate for the effect of the winding magnetomotive force on the main magnetic circuit of the iron core.

[0048] This invention provides a parameterized calculation relationship between the number of turns in the compensation winding and the cross-sectional area of ​​the conductor. Specifically, the number of turns in the compensation winding is associated with the maximum ampere-turns of the bias to be compensated, the maximum allowable compensation current of the power drive unit, the equivalent magnetic coupling coefficient, and the safety margin coefficient. The cross-sectional area of ​​the conductor is associated with the maximum compensation current and the allowable current density. This allows the number of turns in the compensation winding and the cross-sectional area of ​​the conductor to be directly matched with the bias compensation requirements and driving capability, thereby improving the determinism, engineering adaptability, feasibility, and compensation efficiency of the parameter design.

[0049] The detection unit 150 and the control unit 160 are connected to acquire detection signals characterizing the magnetic flux bias, magnetic density bias and / or excitation current components of the iron core 110, extract the bias feedback quantity based on the detection signals, calculate the compensation ampere-turn command according to the deviation between the bias component and the target value, and convert the compensation ampere-turn command into a compensation current command to generate a PWM drive signal in combination with the feedback compensation current. More preferably, the detection unit 150 is used to acquire detection signals characterizing the magnetic flux bias, magnetic density bias and / or excitation current components of the core 110; the control unit 160 extracts DC and / or low-frequency bias components based on the detection signals and calculates compensation ampere-turn commands. Preferably, the detection unit 150 includes a detection winding, which collects induced voltage and inputs it into the control unit 160 as a detection signal characterizing the magnetic flux bias of the iron core 110. The control unit 160 integrates and corrects the drift of the induced voltage to obtain a magnetic flux estimate, and extracts its bias component as a bias feedback quantity.

[0050] in, To detect the induced voltage in the winding, To detect the number of turns in the winding, The sampling period is For the first The magnetic flux estimate at each sampling time. This is the drift suppression leakage coefficient.

[0051] The drift suppression leakage coefficient It adaptively adjusts with the rate of change of induced voltage to retain the tracking capability of DC and / or low-frequency bias components while suppressing integral drift.

[0052] Specifically, the drift suppression leakage coefficient The rate of change of the induced voltage in the winding is adaptively determined based on the rate of change of the induced voltage detected at adjacent sampling times; let the rate of change of the induced voltage be:

[0053] The drift suppression leakage coefficient satisfy:

[0054] in, , The rate of change threshold, and > ≥0; , These are the upper and lower limits of the leakage coefficient, respectively. > >0.

[0055] This invention adaptively adjusts the drift suppression leakage coefficient based on the rate of change of induced voltage at adjacent sampling times: when the rate of change of induced voltage is small, the leakage coefficient is increased to enhance the suppression capability of slow-varying integral drift; when the rate of change of induced voltage is large, the leakage coefficient is decreased to retain the tracking capability of true DC and / or low-frequency bias magnetic components. This balances long-term drift stability with the sensitivity of bias magnetic component extraction, improving the reliability of bias magnetic detection under complex operating conditions.

[0056] Preferably, the detection unit 150 includes a magnetic field sensor, which is used to acquire the magnetic flux density signal of the iron core 110 as a raw detection signal characterizing the magnetic flux density bias of the iron core 110 and output it to the control unit 160; the control unit 160 is used to extract the bias component of the magnetic flux density signal to obtain the magnetic flux density bias component as the bias feedback quantity.

[0057] The magnetic field sensor is one or more of a Hall sensor, a magnetoresistive sensor, or a fluxgate sensor.

[0058] Preferably, the detection unit 150 includes a primary current detection module and a secondary current detection module, used to acquire the primary current of the primary winding 120 and the secondary current of the secondary winding 130 as raw detection signals and output them to the control unit 160; the control unit 160 is used to estimate the excitation current based on the primary current and the secondary current, and extract the DC and / or low-frequency components of the excitation current as the bias feedback quantity. The formula for estimating the excitation current is:

[0059] in, For the primary current of the primary winding 120, This refers to the secondary current of the secondary winding 130. For a single winding of 120 turns, The number of turns for the secondary winding is 130. The obtained excitation current is used for estimation.

[0060] The control unit 160 includes a state estimation module, a biased magnetic outer loop controller, a compensation current inner loop, and a PWM generation module. The state estimation module is used to perform magnetic flux state, magnetic density state and / or excitation current state estimation based on the original detection signal output by the detection unit 150, and extract the corresponding bias feedback quantity. The bias outer loop controller is used to calculate the compensation ampere-turn command based on the deviation between the bias feedback quantity and the target value, wherein the target value is a zero bias reference value or a preset bias reference value; Preferably, the bias feedback quantity is set as follows: , the target value is , then the deviation satisfies:

[0061] the compensation ampere-turn instruction is calculated based on the deviation ; the compensation current inner loop is configured to convert the compensation ampere-turn instruction into a compensation current instruction according to the number of turns of the compensation winding 140 , and compare the compensation current instruction with the actual compensation current feedback , and generate a PWM driving quantity according to the current deviation obtained by comparison; the PWM generation module is configured to output a PWM driving signal based on the PWM driving quantity; wherein, the formula for converting the compensation ampere-turn instruction into the compensation current instruction is as follows:

[0062] wherein, is the compensation ampere-turn instruction, is the number of turns of the compensation winding 140, is the compensation current instruction.

[0063] the control unit 160 sets a transparent constraint, the transparent constraint acts on the compensation control channel, and the compensation control channel comprises a control link from bias magnetic feedback quantity extraction, bias magnetic outer loop control to the compensation current inner loop and compensation current instruction generation (which can be understood as Figure 2 the channel where the bias magnetic outer loop controller and the compensation current inner loop are located in); the transparent constraint includes at least one of the following: performing low-pass filtering on the compensation control channel; setting notch / band-stop filtering for the power frequency component in the compensation control channel; performing bandwidth limitation on the compensation current instruction.

[0064] the control unit 160 sets a hierarchical response strategy: when the bias magnetic component is lower than a first threshold, no compensation or micro-compensation is performed; when the bias magnetic component is between the first threshold and a second threshold, the compensation is enhanced proportionally; when the bias magnetic component exceeds the second threshold, strong compensation is entered and the compensation current is limited in amplitude.

[0065] Specifically, the hierarchical response strategy is implemented by changing the compensation ampere-turn instruction, including: When | | < T1, no compensation or micro-compensation is performed, and the compensation ampere-turn instruction satisfies:

[0066] wherein is a micro-compensation gain that is zero or smaller than a first proportionality coefficient; is the deviation between the bias magnetic feedback quantity and the target value; T1 is a first threshold; When T1≤| |<T2, proportional enhanced compensation is performed, and the compensated ampere-turn instruction satisfies:

[0067] wherein and are enhanced compensation coefficients; T2 is a second threshold; When | |≥T2, strong compensation is entered and the compensation current is limited, and the compensated ampere-turn instruction satisfies:

[0068] wherein and are strong compensation coefficients, is the compensated ampere-turn limit value.

[0069] In specific implementation, , , are non-negative gain coefficients, and satisfy: ; , are non-negative nonlinear enhancement coefficients, and satisfy: 0≤ k 3≤ k 4; T1 and T2 are the first threshold and the second threshold respectively, and satisfy: ; Preferably, the micro-compensation gain coefficient may be 0 to 0.2, the enhanced compensation coefficient may be 0.2 to 1.0, and the strong compensation coefficient may be 1.0 to 2.5; the nonlinear enhancement coefficient may be 0 to 0.2, may be 0.2 to 0.8, and preferably satisfies ≥ , so that the nonlinear enhancement effect in the strong compensation region is higher than that in the enhanced compensation region.

[0070] Preferably, the first threshold T1 and the second threshold T2 may be determined according to the maximum absolute value of the bias magnetic feedback quantity under the rated working condition , wherein:

[0071] And T2 > T1.

[0072] The power drive unit 170 is used to drive the power inverter circuit based on the PWM drive signal, so that the compensation winding 140 outputs a compensation current to generate a compensation magnetomotive force that is equal in amplitude and opposite in direction to the bias magnetomotive force, so as to counteract the magnetic flux operating point offset caused by the bias magnetomotive force, so that the iron core 110 works in the linear region and realizes the equivalent virtual air gap anti-saturation.

[0073] More preferably, the power drive unit 170 drives the compensation winding 140 to generate a compensation magnetomotive force that is equal in amplitude and opposite in direction to the bias magnetomotive force, so as to counteract the magnetic flux operating point shift caused by the bias magnetomotive force, so that the iron core 110 operates in the linear region, thereby forming an anti-saturation effect of an equivalent virtual air gap. The power drive unit 170 includes an isolation drive circuit, a full-bridge or half-bridge power inverter circuit, and a current sampling circuit; The full-bridge inverter circuit or half-bridge inverter circuit has the ability to output compensation current in both directions to achieve the switching of compensation ampere-turns in the positive and negative directions.

[0074] like Figure 2 As shown, the power drive unit 170 includes an isolation drive circuit, a full-bridge or half-bridge power inverter circuit, and a current sampling circuit. The isolation drive circuit is used to drive the full-bridge or half-bridge power inverter circuit according to the PWM drive signal; The full-bridge or half-bridge power inverter circuit is used to convert the DC bus voltage into bidirectional compensated current and output the compensated current. To the compensation winding 140, so that the compensation winding 140 outputs a compensation current. This generates a compensating magnetomotive force that is opposite to the direction of the bias magnetomotive force. The current sampling circuit is used for... Sampling is performed, and the sampling results are input into the compensation current inner loop of the control unit 160 for compensation current closed-loop correction.

[0075] like Figure 3 As shown, this invention cancels the DC bias magnetomotive force by the compensating magnetomotive force generated by the compensating winding 140, causing the magnetic flux operating point of the iron core 110 to return to the linear region, thereby achieving the anti-saturation effect of the equivalent virtual air gap. The virtual air gap is not a physical air gap created on the iron core 110, but rather an equivalent magnetomotive force voltage drop formed in the magnetic circuit through active compensation, avoiding the problems of increased excitation current and decreased measurement accuracy caused by a physical air gap.

[0076] Embodiment 2 of the present invention provides a control method for an anti-saturation current transformer based on a virtual air gap magnetic circuit design, comprising the following steps: S1: The detection unit 150 acquires the original detection signal characterizing the magnetic flux bias, magnetic density bias and / or excitation current component of the iron core 110, and sends the original detection signal to the control unit 160. S2: The control unit 160 performs state estimation and bias component extraction based on the original detection signal to obtain the bias magnetic feedback quantity; S3: The bias magnetic outer loop controller of the control unit 160 calculates and outputs a compensation ampere-turn command based on the deviation between the bias magnetic feedback and the target value; S4: The inner loop of the compensation current of the control unit 160 converts the compensation ampere-turn command into a compensation current command, compares the compensation current command with the actual compensation current feedback, generates a PWM drive signal based on the comparison result, drives the power inverter circuit, and causes the compensation winding 140 to output a compensation current, generating a compensation magnetomotive force opposite to the direction of the bias magnetomotive force, thus offsetting the magnetic flux operating point offset caused by the bias magnetomotive force.

[0077] More preferably, the detection unit 150 acquires the magnetic flux / magnetic density or excitation current characterization of the iron core 110 in real time, the control unit 160 extracts the DC and low-frequency bias components based on the characterization and outputs compensation commands, and the power drive unit 170 drives the compensation winding 140 to output compensation current according to the compensation commands, thereby generating compensation magnetomotive force to counteract the bias influence.

[0078] In this embodiment, the detection unit 150 is used to acquire a detection signal that characterizes the offset of the magnetic flux operating point of the iron core 110. The detection signal can be a magnetic flux / magnetic density characterization quantity.

[0079] In one implementation, the detection unit 150 includes a detection winding. By acquiring the induced voltage of the detection winding, the control unit 160 integrates and corrects the drift to obtain a magnetic flux estimate, thereby extracting the magnetic flux bias component as the bias feedback quantity. In another implementation, the detection unit 150 includes a magnetic field sensor to acquire a magnetic flux density signal at a specified position on the iron core 110, and the control unit 160 extracts the magnetic flux density bias component as a bias feedback quantity.

[0080] Specifically, the induced voltage collected by the detection winding of the detection unit 150 satisfies the following formula, and the control unit 160 performs integration and drift correction to obtain the magnetic flux estimate and its bias component as the bias feedback quantity:

[0081] in, To detect the induced voltage in the winding, To detect the number of turns in the winding, It has a core with a magnetic flux of 110. This is a drift correction term.

[0082] The flux estimation signal is incorporated into a high-pass filter drift correction algorithm: Will A first- or second-order digital high-pass filter is input, with its cutoff frequency set below the power frequency to ensure that the power frequency and its harmonic components remain unaffected while suppressing slow-varying drift components close to DC. Simultaneously, the control unit 160 performs low-pass filtering or moving average on the flux estimation signal after high-pass filtering, extracting its slow-varying bias component as the bias feedback quantity. The cutoff frequency of the high-pass filter is set to 0.05–1 Hz to balance drift suppression with low-frequency bias tracking capability.

[0083] The magnetic field sensor of the detection unit 150 is one or more of a Hall sensor, a magnetoresistive sensor, or a fluxgate sensor, used to directly acquire the magnetic flux density signal of the iron core 110 and extract the magnetic flux density bias component as the bias feedback quantity by the control unit 160.

[0084] The detection unit 150 includes primary current detection and secondary current detection. The control unit 160 estimates the excitation current by calculating the difference between the primary current (based on the turns ratio) and the secondary current, and extracts the DC and / or low-frequency components of the excitation current as the bias feedback quantity. The excitation current estimation satisfies the following formula:

[0085] in, For primary current, Secondary current, For one-time equivalent number of turns, For the second number of turns, To estimate the excitation current.

[0086] In this embodiment, the control unit 160 performs closed-loop compensation control based on the detection signal of the detection unit 150 to form an equivalent virtual air gap with anti-saturation capability.

[0087] The control unit 160 extracts components from the detection signal to obtain DC and / or low-frequency bias magnetic components, calculates compensation ampere-turn commands based on the deviation between the bias magnetic components and the target value, and then converts the compensation ampere-turn commands into compensation current commands to drive the compensation winding 140 to output compensation current.

[0088] Specifically, the state estimation module of the control unit 160 estimates the magnetic flux or magnetic density state based on the detection signal. The digital controller executes dual closed-loop control of the bias outer loop and the compensation current inner loop, and converts the compensation ampere-turn command into a compensation current command. The conversion relationship between the compensation ampere-turn command and the compensation current command satisfies the following formula:

[0089] in, To compensate for the Amz directive, To compensate for the 140 turns of the winding, This is a current compensation command.

[0090] The control unit 160 sets transparent constraints on the power frequency and its harmonic frequency bands. The transparent constraints include at least one of the following: low-pass filtering of the compensation control channel, notch / band-stop filtering of the power frequency, or bandwidth limitation of the compensation command, so that the compensation loop mainly acts on the DC and low-frequency bias components.

[0091] The control unit 160 is configured with a graded response strategy: when the bias magnetic component is below the first threshold, no compensation or slight compensation is performed; when the bias magnetic component is between the first threshold and the second threshold, compensation is enhanced proportionally; when the bias magnetic component exceeds the second threshold, strong compensation is performed and the compensation current is limited.

[0092] In this embodiment, the power drive unit 170 drives the compensation winding 140 according to the PWM signal output by the control unit 160 to achieve rapid, bidirectional output of the compensation current, thereby generating a compensation magnetomotive force with the same amplitude and opposite direction to the bias magnetomotive force, canceling the magnetic flux operating point offset caused by the bias magnetomotive force, and enabling the iron core 110 to operate in the linear region for a long time. The power drive unit 170 can adopt a full-bridge or half-bridge inverter structure, and can be set with compensation current sampling and overcurrent, overvoltage, and temperature rise protection functions to improve the system's operational safety and reliability.

[0093] More preferably, the original detection signals of the magnetic flux bias and excitation current components are acquired simultaneously and their bias feedback quantities are extracted respectively. When the difference between the bias feedback quantities corresponding to the two exceeds a preset threshold, an alarm is output and the system enters a degraded compensation mode or a disabled compensation mode. The degradation compensation mode is as follows: stop the bias outer loop control based on the magnetic flux bias branch, retain only the bias feedback based on the excitation current branch, calculate the compensation ampere-turn command, and apply a limit to the compensation current command. The deactivation compensation mode is as follows: turn off the PWM drive signal and stop the power inverter circuit from outputting compensation current.

[0094] The method further includes: When the output compensation current sampling value of the compensation winding 140 exceeds the preset overcurrent threshold, the compensation current command is limited and the compensation output is reduced. When the magnetic flux bias detection branch or magnetic flux density bias detection branch loses its signal, becomes abnormally saturated, or the magnetic flux estimation drift exceeds a preset drift threshold, the bias outer loop based on the corresponding branch is stopped and the system switches to a degraded compensation mode based on the excitation current component. Specifically, the detection unit 150 is responsible for acquiring the original detection signals of the magnetic flux bias, magnetic flux density bias, and / or excitation current component, and the control unit 160 judges the signal status of each detection branch. When the magnetic flux bias detection branch or magnetic flux density bias detection branch experiences signal loss, abnormal saturation, or magnetic flux estimation drift exceeding the limit, the control unit 160 determines that the corresponding branch is abnormal, stops the bias outer loop control based on that branch, no longer uses the magnetic flux bias / magnetic flux density bias signal corresponding to that branch for compensation, and executes / switches to subsequent degraded compensation based on the excitation current component or disables compensation logic.

[0095] When the excitation current detection branch also malfunctions, or the aforementioned malfunction persists for more than a preset duration, or a hardware failure occurs, the compensation output is disabled and an alarm signal is output, causing the current transformer to enter an uncompensated safe operating state. That is, when the magnetic flux bias detection branch or the magnetic density bias detection branch malfunctions, the excitation current detection branch can still maintain normal operation, and the control unit 160 continues to extract the bias feedback quantity based on the excitation current component and perform degraded compensation; only when the excitation current detection branch also malfunctions, or the aforementioned malfunction persists for more than a preset duration, or a hardware failure occurs, will the compensation output be disabled and an alarm signal be output.

[0096] like Figure 4 As shown in this embodiment of the invention, the control method includes: High-frequency sampling is performed on the magnetic flux / magnetic density or excitation current characterization signal, and compensation current feedback is obtained; The magnetic flux / magnetic density estimation value is obtained through the state estimation module; the estimation value is low-pass filtered to extract the DC and / or low-frequency bias magnetic components; wherein, redundant estimation of magnetic flux bias and excitation current bias can be used simultaneously, and when the difference between the two exceeds a preset threshold, an alarm is output and the system enters the degradation compensation mode or the compensation mode is disabled. Based on the deviation between the bias magnetic component and the target value, the outer loop controller outputs a compensation ampere-turn command; the compensation ampere-turn command is then converted into a compensation current command. The PWM drive power drive unit 170 power inverter circuit is generated by controlling the inner loop current, so that the compensation winding 140 outputs a compensation magnetomotive force that is equal in amplitude and opposite in direction to the bias magnetomotive force. At the same time, a transparent constraint is applied to the compensation control channel, so that the compensation mainly acts on the DC and low-frequency bias magnetic components while remaining transparent to the power frequency and higher-order AC current components to be measured. It also implements compensation current limiting and protection and degradation strategies such as overcurrent, overvoltage, and sensor malfunction: when the current sampling value of the compensation winding 140 exceeds the preset overcurrent threshold, the compensation current command is limited and the compensation output is reduced; when the magnetic flux bias detection or magnetic density bias detection signal is lost, abnormally saturated, or the magnetic flux estimation drift exceeds the preset drift threshold, the compensation outer loop based on magnetic flux bias is stopped and switched to the degradation compensation mode based on excitation current bias; when the excitation current detection is also abnormal, or the above abnormalities continue for more than the preset duration or a hardware failure occurs, the compensation output is disabled and an alarm signal is output, so that the current transformer enters the uncompensated safe operation state.

[0097] This invention utilizes an active magnetic field compensation system comprised of a detection unit 150, a control unit 160, a power drive unit 170, and a compensation winding 140. This system achieves an anti-saturation effect of an equivalent virtual air gap without introducing a physical air gap. It can significantly improve the anti-saturation capability of current transformers under DC bias conditions and maintain transmission accuracy under normal power frequency measurement conditions. It is suitable for HVDC DC bias measurement and protection, rail transit traction current measurement, and DC industrial load metering and monitoring scenarios such as electrolysis / electroplating.

[0098] Embodiment 3 of the present invention provides a terminal, including a processor and a storage medium; the storage medium is used to store instructions; the processor is used to perform operations according to the instructions to execute the steps of the method.

[0099] Embodiment 4 of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method.

[0100] Compared with the prior art, the beneficial effects of the present invention include at least the following: This invention acquires detection signals characterizing the core magnetic flux bias, magnetic density bias, and / or excitation current components through a detection unit. The control unit calculates a compensation ampere-turn command based on the deviation between the bias feedback and the target value, and converts it into a compensation current command to generate a PWM drive signal. The power drive unit outputs a compensation magnetomotive force opposite to the bias magnetomotive force based on the PWM drive compensation winding, so that the core operates in the linear region, achieving equivalent virtual air gap anti-saturation. At the same time, by setting transparent constraints on the compensation control channel, the compensation mainly acts on the DC and / or low-frequency bias components, thereby maintaining transmission accuracy under normal power frequency measurement conditions.

[0101] This invention utilizes an active magnetic field compensation system comprised of a detection unit, a control unit, a power drive unit, and a compensation winding to achieve an anti-saturation effect of an equivalent virtual air gap without introducing a physical air gap. This significantly improves the anti-saturation capability of current transformers under DC bias conditions and maintains transmission accuracy under normal power frequency measurement conditions. It is suitable for HVDC DC bias measurement and protection, rail transit traction current measurement, and DC industrial load metering and monitoring scenarios such as electrolysis / electroplating.

[0102] This invention provides a parameterized calculation relationship between the number of turns in the compensation winding and the cross-sectional area of ​​the conductor. Specifically, the number of turns in the compensation winding is associated with the maximum ampere-turns of the bias to be compensated, the maximum allowable compensation current of the power drive unit, the equivalent magnetic coupling coefficient, and the safety margin coefficient. The cross-sectional area of ​​the conductor is associated with the maximum compensation current and the allowable current density. This allows the number of turns in the compensation winding and the cross-sectional area of ​​the conductor to be directly matched with the bias compensation requirements and driving capability, thereby improving the determinism, engineering adaptability, feasibility, and compensation efficiency of the parameter design.

[0103] This invention integrates and corrects the induced voltage, and adaptively adjusts the drift suppression leakage coefficient according to the rate of change of the induced voltage at adjacent sampling times. This can balance the anti-drift stability during long-term operation with the sensitivity of bias magnetic component extraction, thereby improving the reliability of bias magnetic detection under complex working conditions.

[0104] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0105] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0106] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0107] Computer program instructions used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing the status information of the computer-readable program instructions to implement various aspects of this disclosure.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. An anti-saturation current transformer based on a virtual air gap magnetic circuit design, characterized in that, The anti-saturation current transformer includes an iron core (110), a primary winding (120), a secondary winding (130), a compensation winding (140), a detection unit (150), a control unit (160), and a power drive unit (170). The primary winding (120) and the secondary winding (130) are wound on the iron core (110) for normal transmission of the measured current. The compensation winding (140) is wound on the iron core (110) and does not participate in the normal transmission of the measured current; The detection unit (150) and the control unit (160) are connected to acquire detection signals characterizing the magnetic flux bias, magnetic density bias and / or excitation current component of the iron core (110), extract the bias feedback quantity based on the detection signals, calculate the compensation ampere-turn command according to the deviation between the bias feedback quantity and the target value, and convert the compensation ampere-turn command into a compensation current command to generate a PWM drive signal. The detection unit (150) includes a detection winding, which collects induced voltage and inputs it as a detection signal characterizing the magnetic flux bias of the iron core (110) into the control unit (160); the control unit (160) integrates and corrects the induced voltage to obtain a magnetic flux estimate, and extracts its bias component as a bias feedback quantity. in, To detect the induced voltage in the winding, To detect the number of turns in the winding, The sampling period is For the first The magnetic flux estimate at each sampling time. The drift suppression leakage coefficient; , The rate of change threshold; , These are the upper and lower limits of the leakage coefficient, respectively; To detect the rate of change of the winding induced voltage at adjacent sampling times; The power drive unit (170) is used to drive the power inverter circuit based on the PWM drive signal, so that the compensation winding (140) outputs a compensation current and generates a compensation magnetomotive force that is equal in amplitude and opposite in direction to the bias magnetomotive force, so as to offset the magnetic flux operating point offset caused by the bias magnetomotive force, so that the iron core (110) works in the linear region and realizes the equivalent virtual air gap anti-saturation.

2. The anti-saturation current transformer based on virtual air gap magnetic circuit design according to claim 1, characterized in that: The compensation winding (140) is located in the winding window area of ​​the iron core (110) and is wound on the same column and in the same window as the secondary winding (130), located on the outside or inside of the secondary winding (130). Furthermore, an insulating isolation layer and / or a shielding layer are provided between the compensation winding (140) and the secondary winding (130) to achieve electrical isolation between the compensation winding (140) and the secondary winding (130) and reduce the coupling interference of the compensation high-frequency drive to the secondary side.

3. The anti-saturation current transformer based on virtual air gap magnetic circuit design according to claim 1, characterized in that: The number of turns of the compensation winding (140) Based on the maximum uncompensated bias ampere-turns The power drive unit allows a maximum compensation current. The equivalent magnetic coupling coefficient between the compensating winding and the iron core and safety margin coefficient Confirmed, satisfied: And the conductor cross-sectional area of ​​the compensation winding (140) Based on the maximum compensation current and the allowable current density Confirmed, satisfied: Wherein, the safety margin coefficient The equivalent magnetic coupling coefficient is greater than 1. The coupling efficiency coefficient is used to compensate for the effect of the winding magnetomotive force on the main magnetic circuit of the iron core.

4. The anti-saturation current transformer based on virtual air gap magnetic circuit design according to claim 1, characterized in that: The detection unit (150) includes a magnetic field sensor, which is used to acquire the magnetic flux density signal of the iron core (110) as the original detection signal characterizing the magnetic flux density bias of the iron core (110) and output it to the control unit (160). The control unit (160) is used to extract the bias component of the magnetic flux density signal to obtain the magnetic flux density bias component as the bias feedback quantity.

5. The anti-saturation current transformer based on virtual air gap magnetic circuit design according to claim 4, characterized in that: The magnetic field sensor is one or more of a Hall sensor, a magnetoresistive sensor, or a fluxgate sensor.

6. The anti-saturation current transformer based on virtual air gap magnetic circuit design according to claim 1, characterized in that: The detection unit (150) includes a primary current detection module and a secondary current detection module, which are used to acquire the primary current of the primary winding (120) and the secondary current of the secondary winding (130) as raw detection signals and output them to the control unit (160). The control unit (160) is used to estimate the excitation current based on the primary current and the secondary current, and to extract the DC and / or low-frequency components of the excitation current as the bias feedback quantity. The formula for estimating the excitation current is: in, For the primary current of the primary winding (120), For the secondary current of the secondary winding (130), The number of turns in a single winding (120). The number of turns of the secondary winding (130) The obtained excitation current is used for estimation.

7. The anti-saturation current transformer based on virtual air gap magnetic circuit design according to claim 1, characterized in that: The control unit (160) includes a state estimation module, a biased magnetic outer loop controller, a compensation current inner loop, and a PWM generation module; The state estimation module is used to perform magnetic flux state, magnetic density state and / or excitation current state estimation based on the original detection signal output by the detection unit (150), and extract the corresponding bias feedback quantity. The bias magnetic outer loop controller is used to determine the deviation between the bias magnetic feedback quantity and the target value. Calculate the compensation ampere-turn command; The compensation current inner loop is used to transmit compensation ampere-turn commands. The compensation current command is converted according to the number of turns of the compensation winding (140). and the compensation current command Compensation current with feedback The comparison is used to generate a PWM drive quantity based on the current deviation obtained from the comparison. The PWM generation module is used to output a PWM drive signal based on the PWM drive quantity.

8. The anti-saturation current transformer based on virtual air gap magnetic circuit design according to claim 1, characterized in that: The power drive unit (170) includes an isolation drive circuit, a full-bridge or half-bridge power inverter circuit, and a current sampling circuit. The isolation drive circuit is used to drive the full-bridge or half-bridge power inverter circuit according to the PWM drive signal; The full-bridge or half-bridge power inverter circuit is used to convert the DC bus voltage into bidirectional compensated current and output the compensated current. To the compensation winding (140), so that the compensation winding (140) outputs a compensation current. This generates a compensating magnetomotive force that is opposite to the direction of the bias magnetomotive force. The current sampling circuit is used for... Sampling is performed, and the sampling results are input into the compensation current inner loop of the control unit (160) for compensation current closed-loop correction.

9. The anti-saturation current transformer based on virtual air gap magnetic circuit design according to claim 1, characterized in that: The control unit (160) is provided with a transparent constraint, which acts on the compensation control channel, the compensation control channel including a control link from the extraction of the bias feedback quantity to the generation of the compensation current command; the transparent constraint includes at least one of the following: The compensation control channel is low-pass filtered; Notch / band-stop filtering is applied to the power frequency components in the compensation control channel; Bandwidth limitation is applied to the compensation current command.

10. The anti-saturation current transformer based on virtual air gap magnetic circuit design according to claim 1, characterized in that: The control unit (160) is configured with a tiered response strategy, which is implemented by changing the compensation ampere-turn command, including: When | | <T1, no compensation or slight compensation is performed, and the compensated ampere-turns instruction satisfies: in For micro-compensation gain; T1 represents the deviation between the bias feedback quantity and the target value; T1 is the first threshold. When T1 ≤ | | < T2, proportional enhancement compensation is performed, and the compensated ampere-turns instruction satisfies: in and To enhance the compensation coefficient; T2 is the second threshold; When | When |≥T2, strong compensation is initiated and the compensation current is limited. The compensation ampere-turn command satisfies: in and For strong compensation coefficient, To compensate for the ampere-turn limit.

11. A control method for an anti-saturation current transformer based on virtual air-gap magnetic circuit design as described in any one of claims 1-10, characterized in that, Includes the following steps: S1: The detection unit (150) acquires the original detection signal characterizing the magnetic flux bias, magnetic density bias and / or excitation current component of the iron core (110), and sends the original detection signal to the control unit (160). S2: The control unit (160) obtains the bias feedback amount based on the original detection signal; S3: The bias outer loop controller of the control unit (160) calculates and outputs a compensation ampere-turn command based on the deviation between the bias feedback amount and the target value; S4: The inner loop of the compensation current of the control unit (160) converts the compensation ampere-turn command into a compensation current command, compares the compensation current command with the feedback compensation current, generates a PWM drive signal based on the comparison result, drives the power inverter circuit, and makes the compensation winding (140) output compensation current to generate a compensation magnetomotive force opposite to the direction of the bias magnetomotive force, thus offsetting the magnetic flux operating point offset caused by the bias magnetomotive force.

12. The control method according to claim 11, characterized in that: Simultaneously, the original detection signals of magnetic flux bias and excitation current components are acquired and their bias feedback quantities are extracted respectively. When the difference between the bias feedback quantities of the two exceeds the preset threshold, an alarm is output and the system enters the degradation compensation mode or disables the compensation mode. The degradation compensation mode is as follows: only the bias feedback based on the excitation current is retained, the compensation ampere-turn command is calculated, and the compensation current command is limited. The deactivation compensation mode is as follows: turn off the PWM drive signal and stop the power inverter circuit from outputting compensation current.

13. The control method according to claim 11, characterized in that: The method further includes: When the output compensation current sampling value of the compensation winding (140) exceeds the preset overcurrent threshold, the compensation current command is limited and the compensation output is reduced. When the magnetic flux bias detection or magnetic density bias detection signal is lost, abnormally saturated, or the magnetic flux estimation drift exceeds the preset drift threshold, the corresponding bias outer loop is stopped and the degradation compensation mode based on the excitation current component is switched. When the excitation current detection also becomes abnormal, or the above abnormality lasts for more than the preset duration, or a hardware failure occurs, the compensation output is disabled and an alarm signal is output, so that the current transformer enters the uncompensated safe operation state.

14. A terminal, comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to perform the steps of the method according to any one of claims 11-13.

15. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the program performs the steps of the method according to any one of claims 11-13.

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