Method and apparatus for demodulation of zero flux current transformer

Abstract

A method and apparatus for demodulating a zero-flux current transformer, the method comprising: acquiring the induced voltage signals of a first core and a second core, the amplitude of a primary current, and the ambient temperature; and obtaining the time difference Δ between the saturation zero-crossing points of the two cores based on the induced voltage signals of the first core and the second core. t and Δ t The signal-to-noise ratio of the channel and the amplitude difference Δ of the peak voltage before saturation of the two iron cores. V and Δ V The signal-to-noise ratio of the channel; based on the primary current amplitude, ambient temperature, and Δ... t The signal-to-noise ratio and Δ of the channel V The signal-to-noise ratio of the channel is obtained as Δ. t Channel weighting coefficient w 1 and Δ V Channel weighting coefficient w 2; Based on Δ t Δ V , w 1 and w 2. Obtain the fusion error signal; output the fusion error signal to the feedback controller to generate a feedback current to maintain the zero flux state. The method and apparatus provided in this embodiment of the invention can achieve high-precision and highly robust current measurement across the entire range and under all operating conditions.

Description

Technical Field

[0001] This invention relates to the field of power system measurement technology, and more specifically, to a method and apparatus for demodulating a zero-flux current transformer. Background Technology

[0002] Zero-Flux Current Transformer (ZCT) eliminates hysteresis and nonlinearity by introducing feedback current to make the net ampere-turns in the magnetic core zero, thus enabling control of the primary current. I p High-precision, high-bandwidth measurement. Currently, its performance bottleneck mainly lies in the accuracy and robustness of error signal extraction.

[0003] In a typical dual-core zero-flux structure, two identical iron cores, T1 and T2, share the same excitation source, with their primary windings connected in reverse series. When the primary current... I p When = 0, the magnetization of the two iron cores is symmetrical; when I p When the bias magnetic field is zero, the symmetry is broken, generating an observable differential signal. Currently, there are two main types of error extraction methods: 1. Time difference Δ t Principle: The bias magnetic field causes the saturation times of the two iron cores to be staggered, with a time difference Δ. t = t z1 - t z2 and I p Approximately proportional: Δ t = k 1 I p ,in k 1 is the proportionality coefficient, which depends on the core material, excitation frequency, and winding parameters.

[0004] Advantages: Δ t It has high theoretical sensitivity to weak currents, especially in the low current region, and its linearity is excellent. It is also unaffected by analog front-end gain drift, making it suitable for high-resolution measurements.

[0005] Disadvantages: Δ t The practical measurability is limited by the hardware time resolution. Typical zero-crossing detection circuits based on FPGAs or high-speed comparators have inherent time jitter (typically on the order of 100 ps). I p When it is extremely small (e.g., <0.1% of the nominal value), the resulting Δ tIf the jitter level is less than this, it can cause a sharp deterioration in the signal-to-noise ratio (SNR), or even be overwhelmed by quantization noise. Furthermore, Δ t Highly sensitive to ambient temperature—the permeability of the iron core changes with temperature, altering the saturation threshold and hysteresis loop shape, thereby causing… k 1. Drift further degrades long-term stability under low current.

[0006] 2. Voltage amplitude difference Δ V Principle: Due to the effect of the bias magnetic field, the peak magnetic flux reached by the two iron cores before saturation is different, resulting in a different peak value of their induced voltage. V p1 and V p2 A difference exists. The difference Δ between the peak voltages of the two iron cores before saturation. V = V p1 - V p2 Similarly with I p Proportional: Δ V = k 2 I p .in k 2 is another proportionality coefficient, reflecting the magnetoelectric conversion efficiency and the gain of the signal conditioning circuit.

[0007] Advantages: Δ V It does not rely on precise timing measurements and is insensitive to high-frequency switching noise and clock jitter. By employing a high-resolution ADC in conjunction with digital filtering, it can effectively suppress background noise in the low-frequency range and improve the signal-to-noise ratio of weak signals. Therefore, in the ultra-low current region, when Δ t When hardware fails due to its limits, Δ V This often becomes a more reliable source of error. Furthermore, Δ V It is relatively insensitive to temperature-induced saturation point shifts and exhibits good long-term stability.

[0008] Disadvantages: Under high current or high dynamic conditions, Δ V It is susceptible to amplitude distortion due to analog front-end nonlinearity (such as op-amp slew rate limitation and ADC input bandwidth) and common-mode interference coupling. At the same time, its accuracy is highly dependent on the gain matching and temperature drift characteristics of the signal conditioning circuit. If precise calibration is not performed, systematic deviations may be introduced.

[0009] The current ZCT demodulation scheme uses a single parameter (Δ only). t Or only Δ V ), unable to achieve full-range performance: using Δ t At low currents, spurious fluctuations may be introduced due to hardware limitations; using Δ VUnder high current, nonlinearity may amplify errors; moreover, existing solutions lack a mechanism for sensing and responding to real-time operating conditions (such as current level, temperature, and SNR of each channel). In HVDC systems, single-parameter solutions are insufficient to meet the dual requirements of "wide dynamic range + high reliability". Summary of the Invention

[0010] In view of this, the present invention proposes a method and apparatus for demodulating a zero flux current transformer, which aims to solve one or more of the technical problems mentioned in the background section above.

[0011] In a first aspect, embodiments of the present invention provide a method for demodulating a zero-flux current transformer, employing a dual-core differential structure. The method includes: acquiring the induced voltage signals of the first and second cores, the primary current amplitude, and the ambient temperature; and obtaining the time difference Δ between the zero-crossing saturation points of the two cores based on the induced voltage signals of the first and second cores. t and Δ t The signal-to-noise ratio of the channel and the amplitude difference Δ of the peak voltage before saturation of the two iron cores. V and Δ V The signal-to-noise ratio of the channel; based on the primary current amplitude, ambient temperature, and Δ... t The signal-to-noise ratio and Δ of the channel V The signal-to-noise ratio of the channel is obtained as Δ. t Channel weighting coefficient w 1 and Δ V Channel weighting coefficient w 2, of which w 1+ w 2=1; based on Δ t Δ V , w 1 and w 2. Obtain the fusion error signal; output the fusion error signal to the feedback controller to generate a feedback current to maintain the zero flux state.

[0012] Furthermore, the data based on the primary current amplitude, ambient temperature, and Δ... t The signal-to-noise ratio and Δ of the channel V The signal-to-noise ratio of the channel is obtained as Δ. t Channel weighting coefficient w 1 and Δ V Channel weighting coefficient w 2, including: based on Δ t and Δ V The relative magnitudes of the channel signal-to-noise ratios yield the weighting coefficients. w 1 and w 2. Basic weights; weighting coefficients are based on primary current amplitude and ambient temperature respectively. w 1 and w The base weights of 2 are adjusted to obtain the final weight coefficients.w 1 and w 2.

[0013] Furthermore, the weighting coefficients based on the primary current amplitude... w 1 and w The basic weights of 2 are adjusted, including: obtaining the current confidence factor based on the primary current amplitude, and using the current confidence factor to adjust the weight coefficients. w 1 and w The base weights of 2 are adjusted.

[0014] Furthermore, the weighting coefficients are based on ambient temperature. w 1 and w The basic weights of 2 are adjusted, including: when the ambient temperature exceeds the calibrated operating range, the weighting coefficients are adjusted. w 1. Apply temperature decay.

[0015] Furthermore, the method also includes: after the duration of the primary current amplitude exceeding a preset current threshold reaches a preset time, using a current confidence factor to adjust the weighting coefficients. w 1 and w The base weights of 2 are adjusted.

[0016] Furthermore, the Δ-based t Δ V , w 1 and w 2. Obtain the fusion error signal, including: obtaining the fusion error signal using the following formula: ;in, For Δ t Δ V Dimensionless quantity.

[0017] Secondly, embodiments of the present invention also provide a device for demodulating a zero-flux current transformer, employing a dual-core differential structure. The device includes: an acquisition unit for acquiring the induced voltage signals of the first and second cores, the primary current amplitude, and the ambient temperature; and a first processing unit for obtaining the time difference Δ between the saturation zero-crossing points of the two cores based on the induced voltage signals of the first and second cores. t and Δ t The signal-to-noise ratio of the channel and the amplitude difference Δ of the peak voltage before saturation of the two iron cores. V and Δ V The signal-to-noise ratio of the channel; the second processing unit, used to base the signal-to-noise ratio on the primary current amplitude, ambient temperature, and Δ. t The signal-to-noise ratio and Δ of the channel V The signal-to-noise ratio of the channel is obtained as Δ. t Channel weighting coefficient w 1 and Δ V Channel weighting coefficient w2, of which w 1+ w 2=1; the third processing unit, used for processing based on Δ t Δ V , w 1 and w 2. Obtain the fusion error signal; feedback unit, used to output the fusion error signal to the feedback controller to generate feedback current to maintain the zero flux state.

[0018] Furthermore, the second processing unit is also configured to: based on Δ t and Δ V The relative magnitudes of the channel signal-to-noise ratios yield the weighting coefficients. w 1 and w 2. Basic weights; weighting coefficients are based on primary current amplitude and ambient temperature respectively. w 1 and w The base weights of 2 are adjusted to obtain the final weight coefficients. w 1 and w 2.

[0019] Furthermore, the weighting coefficients based on the primary current amplitude... w 1 and w The basic weights of 2 are adjusted, including: obtaining the current confidence factor based on the primary current amplitude, and using the current confidence factor to adjust the weight coefficients. w 1 and w The base weights of 2 are adjusted.

[0020] Furthermore, the weighting coefficients are based on ambient temperature. w 1 and w The basic weights of 2 are adjusted, including: when the ambient temperature exceeds the calibrated operating range, the weighting coefficients are adjusted. w 1. Apply temperature decay.

[0021] Furthermore, the second processing unit is also configured to: after the duration for which the primary current amplitude exceeds a preset current threshold reaches a preset time, apply a current confidence factor to the weighting coefficients. w 1 and w The base weights of 2 are adjusted.

[0022] Furthermore, the third processing unit is also configured to: obtain the fusion error signal using the following formula: ;in, For Δ t Δ V Dimensionless quantity.

[0023] Thirdly, embodiments of the present invention also provide a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the methods provided in the above embodiments.

[0024] Fourthly, embodiments of the present invention also provide an electronic device, including: a processor; a memory for storing executable instructions of the processor; the processor being configured to read the executable instructions from the memory and execute the instructions to implement the methods provided in the above embodiments.

[0025] The method and apparatus for demodulating a zero-flux current transformer provided in this invention obtain the time difference Δ between the saturation zero-crossing points of the two cores based on the induced voltage signals of the first and second cores. t and Δ t The signal-to-noise ratio of the channel and the amplitude difference Δ of the peak voltage before saturation of the two iron cores. V and Δ V The signal-to-noise ratio of the channel, combined with the primary current amplitude and ambient temperature, is dynamically adjusted to Δ. t and Δ V The weighting coefficients of the channels are used to obtain the fusion error signal, which enables high-precision and robust current measurement across the entire range and under all operating conditions. Attached Figure Description

[0026] Figure 1 A schematic diagram of a dual-core differential structure according to an embodiment of the present invention is shown; Figure 2 An exemplary flowchart of a method for demodulating a zero-flux current transformer according to an embodiment of the present invention is shown; Figure 3 A schematic diagram of a device for demodulating a zero-flux current transformer according to an embodiment of the present invention is shown. Detailed Implementation

[0027] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0028] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0029] Figure 1 A schematic diagram of a dual-core differential structure according to an embodiment of the present invention is shown. Figure 1 As shown, the zero-flux current transformer adopts a dual-core differential structure, including a first core T1 and a second core T2 of the same material and size, as well as excitation windings connected in reverse series.

[0030] Figure 2 An exemplary flowchart of a method for demodulating a zero-flux current transformer according to an embodiment of the present invention is shown.

[0031] like Figure 2 As shown, the method includes: Step S201: Obtain the induced voltage signal, primary current amplitude, and ambient temperature of the first and second iron cores.

[0032] Specifically, by employing a zero-crossing detection and peak sampling circuit, an analog-to-digital converter (ADC) can be used to synchronously sample the induced voltage signals of the first and second iron cores. This allows for the determination of the zero-crossing times of the two iron cores at saturation and the maximum peak amplitude at saturation. Preferably, the ADC is a high-speed synchronous ADC. The ambient temperature can be obtained using a temperature sensor. Primary current amplitude | I p It can be estimated based on the fusion error signal of the previous cycle.

[0033] In a zero-flux closed-loop control system, the feedback current I fb Under steady state and primary current I p satisfy: N p · I p = N fb · I fb ,in N p This refers to the number of turns in a single winding (usually 1). N fb Let be the number of turns in the feedback coil. Therefore, the magnitude of the primary current can be estimated using the following formula: |I p | = ( N fb / N p ) · | I fb | Among them, | I fbThe value represents the amplitude of the feedback current in the previous control cycle, which can be calculated by converting the voltage across the sampling resistor using an ADC.

[0034] Step S202: Based on the induced voltage signals of the first and second iron cores, obtain the time difference Δ between the zero-crossing points of the two iron cores' saturation. t and Δ t The signal-to-noise ratio of the channel and the amplitude difference Δ of the peak voltage before saturation of the two iron cores. V and Δ V The signal-to-noise ratio of the channel.

[0035] (1) Δ t、 Δ V This can be obtained through analysis of the sampled signal. Using a high-speed comparator or the zero-crossing detection module inside the FPGA, the zero-crossing moments of the induced voltage signals of the first and second iron cores are detected respectively. t z1 and t z2 Taking the difference between the two yields: Δ t = t z1 - t z2 Using a peak sampling circuit or ADC synchronous sampling, the peak values ​​of the induced voltages of the first and second iron cores before saturation are recorded respectively. V p1 and V p2 Taking the difference between the two, we get: Δ V = V p1 - V p2 (2) Calculation method of signal-to-noise ratio: Signal-to-noise ratio (SNR) of the Δt channel t Defined as: SNR t = 20log 10 (Δ t signal / Δ t noise ) Where, Δ t signal Δ measured in the current period t Absolute value; Δ t noise As the system's static noise floor, it can be used in primary current I p Under the condition of =0, continuous measurement nOne cycle (e.g.) n Δ =1000) t The value is taken as its standard deviation as Δ. t noise .

[0036] Δ V Channel signal-to-noise ratio (SNR) V Defined as: SNR V = 20log 10 (Δ V signal / Δ V noise ) Where, Δ V signal Δ measured in the current period V Absolute value; Δ V noise The measurement was also performed under the condition that I_p=0, and Δ was taken. V The standard deviation of the value is used as Δ V noise .

[0037] Step S203: Based on the primary current amplitude, ambient temperature, Δ t The signal-to-noise ratio and Δ of the channel V The signal-to-noise ratio of the channel is obtained as Δ. t Channel weighting coefficient w 1 and Δ V Channel weighting coefficient w 2, of which w 1+ w 2 = 1.

[0038] Further, step S203 includes: Based on Δ t and Δ V The relative magnitudes of the channel signal-to-noise ratios yield the weighting coefficients. w 1 and w The base weight is 2; The weighting coefficients are based on the primary current amplitude and ambient temperature, respectively. w 1 and w The base weights of 2 are adjusted to obtain the final weight coefficients. w 1 and w 2.

[0039] Specifically, the relative magnitude of the signal-to-noise ratio of the two channels is used as the basis for weight allocation; when Δ t The channel signal-to-noise ratio is higher than Δ V When using channels, the basic weights are directed towards... w 1. Tilt; conversely, tilt towards. w 2. Inclined.

[0040] Weight adjustment can be controlled by an adaptive function. One possible approach is to use a sigmoid function to adjust the weights based on the signal-to-noise ratio, as follows: First, define the signal-to-noise ratio difference factor: δ = SNR t - SNR V SNR t and SNR V The unit for all numbers is decibel (dB).

[0041] but w The base weight w1_base is determined by the following formula: w1_base = 1 / (1 + exp(-αδ)) w2_base = 1 - w1_base Where α is the sensitivity coefficient, with a value ranging from 0.1 to 0.5, and α can be taken as 0.2. At δ=0, w1_base=0.5; when δ>0, w1_base>0.5, and the larger δ is, the closer w1_base is to 1; when δ<0, w1_base<0.5, and the smaller δ is, the closer w1_base is to 0.

[0042] As a simplified alternative, a piecewise linear function can also be used: • If δ ≥ 10 dB, then w1_base = 0.9 • If δ ≤ -10 dB, then w1_base = 0.1 If -10 dB < δ < 10 dB, then w1_base = 0.5 + 0.4(δ / 10) The above schemes can all achieve a continuous and monotonic mapping of signal-to-noise ratio differences to weight coefficients; these are merely examples. Furthermore, other adaptive functions can be used for weight adjustment as needed.

[0043] Furthermore, based on the primary current amplitude, the weighting coefficients are adjusted. w 1 and w The basic weights of 2 have been adjusted, including: Based on the magnitude of the primary current, a current confidence factor is obtained, and the current confidence factor is used to adjust the weighting coefficients. w 1 and w The base weights of 2 are adjusted.

[0044] Specifically, a confidence factor related to the magnitude of the primary current is introduced, which characterizes Δ tThe theoretical validity of the channel at the current current level; when the current is below a preset threshold. I th When the current is significantly higher than the threshold, the confidence factor approaches zero; when the current is significantly higher than the threshold, the confidence factor approaches zero. I th When the confidence factor approaches its maximum value, at the threshold... I th A smooth transition is achieved nearby; this confidence factor is used to weight and adjust the base weights. The preset current threshold is also included. I th Based on the system time measurement resolution and signal noise level settings, it is used to characterize Δ t Is the channel within its effective working range?

[0045] (1) Current confidence factor C I Definition: Current confidence factor C I The theoretical validity of the Δt channel under the current primary current amplitude is defined as follows: C I = · 0, when |I p | ≤ I_th1 · (|I p | -I_th1) / (I_th2 - I_th1), when I_th1<|I p | <I_th2 · 1, when |I p | ≥ I_th2 in: I_th1 is the low threshold, determined based on the time resolution of the system's zero-crossing detection circuit. A typical value is I_th1 = 0.5% × I N , I N This is the rated current.

[0046] I_th2 is the high threshold, determined based on the current level when the signal-to-noise ratio of the Δt channel reaches 20dB. A typical value is I_th2 = 2% × I N (2) The method of adjusting the weights of the confidence factor: The corrected weighting coefficient w1_final is calculated by the following formula: w1_final = w1_base C I +w1_base(1- C I )β Where β is the backoff coefficient (0<β<1), representing the minimum weight that the Δt channel retains in the low current region, and can be taken as β=0.1.

[0047] The physical meaning of this correction method is: when the current is extremely low (|I p When | ≤ I_th1), C I =0, w1_final = w1_base·β, meaning the Δt channel is significantly suppressed; when the current is high (|I p When | ≥ I_th2), C I =1, w1_final = w1_base, meaning the Δt channel is fully trusted; in the intermediate region, the weights transition smoothly as the current increases.

[0048] Furthermore, based on ambient temperature, the weighting coefficients are adjusted. w 1 and w The basic weights of 2 have been adjusted, including: When the ambient temperature exceeds the calibrated operating range, the weighting coefficients are adjusted. w 1. Apply temperature decay.

[0049] Specifically, when the ambient temperature exceeds the equipment's calibrated operating range, a temperature correction factor is generated based on the degree of temperature deviation from the nominal value. This factor monotonically decreases as the absolute value of the temperature deviation increases and applies to... w 1. To suppress the effects of temperature drift.

[0050] (1) Temperature correction factor C T Definition: Assume the equipment's calibrated normal operating temperature range is [T_min, T_max], with typical values ​​of [-40°C, +70°C]. Let the current ambient temperature be T_amb.

[0051] Define temperature deviation: ΔT = · 0, when T_min ≤ T_amb ≤ T_max · T_min - T_amb, when T_amb <T_min · T_amb - T_max, when T_amb>T_max Temperature correction factor C T Defined as: C T = 1. When ΔT = 0 · 1 / (1 + γΔT), when ΔT>0 Where γ is the temperature decay coefficient, with a value ranging from 0.01 to 0.05, and γ=0.02 is recommended.

[0052] Example: If T_amb exceeds the upper limit of 20°C (i.e., ΔT=20), then C_T = 1 / (1+0.02×20) ≈ 0.714.

[0053] (2) How temperature correction is applied to weights: Final weighting coefficients after temperature correction w 1 is: w 1 = w1_final· C T w 2 = 1 - w1 That is: when the ambient temperature exceeds the calibrated range, w 1 is suppressed, and the system automatically reduces its dependence on the Δt channel, instead using the ΔV channel signal, which is relatively insensitive to temperature, more.

[0054] It should be noted that the weighting coefficient calculation functions (such as the Sigmoid function, piecewise linear function), current confidence factor definitions (such as piecewise linear interpolation), and temperature correction factor functions (such as the reciprocal decay function) given in the above embodiments are all specific implementation examples of the present invention, and not limitations on the scope of protection of the present invention. Those skilled in the art will understand the core idea of ​​the present invention—that is, based on the Δt channel and Δ... V Based on the real-time signal-to-noise ratio, primary current amplitude, and ambient temperature of the two channels, and by dynamically adjusting the weighting coefficients of the two channels to achieve the fusion error signal, other equivalent adaptive functions can be selected or designed according to the actual system characteristics (such as hardware time resolution, ADC effective bit depth, core material temperature characteristics, etc.), for example, but not limited to: • Replace the Sigmoid function with the hyperbolic tangent function (tanh) or error function (erf) based on the signal-to-noise ratio difference; • Exponential decay confidence factor C based on current amplitude I =1-e^{-|I p | / I0} replaces the piecewise linear function; • Temperature-based exponential correction factor CT = e^{- γ Δ T Replace the reciprocal function; • Employ fuzzy logic rules or lookup table methods to achieve nonlinear mapping of weight coefficients.

[0055] Any modifications or equivalent substitutions that adopt the multi-information fusion dynamic weight allocation principle proposed in this invention and do not depart from the spirit and essence of this invention shall fall within the protection scope of this invention.

[0056] Furthermore, the method also includes: When the duration of a single current amplitude exceeding a preset current threshold reaches a preset time, the current confidence factor is used to adjust the weighting coefficients. w 1 and w The base weights of 2 are adjusted.

[0057] Specifically, a hysteresis bandwidth is set in the current threshold switching region. The weight update is only triggered when the current remains stable outside the hysteresis band for a preset time, thus preventing frequent switching near the threshold boundary.

[0058] Step S204: Based on Δ t Δ V , w 1 and w 2. Obtain the fusion error signal.

[0059] Further, step S104 includes: The fusion error signal is obtained using the following formula: ; in, For Δ t Δ V Dimensionless quantity.

[0060] Specifically, for Δ t Δ V Normalization yields dimensionless quantities .

[0061] Step S205: Input the fusion error signal to the feedback controller to generate a feedback current to maintain the zero flux state.

[0062] Specifically, the feedback current output by the H-bridge power amplifier makes the net ampere-turns of the magnetic core approach zero, maintaining a zero flux state.

[0063] In the above embodiment, the time difference Δ between the saturation zero-crossing points of the two iron cores is obtained based on the induced voltage signals of the first and second iron cores. t and Δ t The signal-to-noise ratio of the channel and the amplitude difference Δ of the peak voltage before saturation of the two iron cores. V and Δ V The signal-to-noise ratio of the channel, combined with the primary current amplitude and ambient temperature, is dynamically adjusted to Δ. t and Δ VThe weighting coefficients of the channels are used to obtain the fusion error signal, which enables high-precision and robust current measurement across the entire range and under all operating conditions.

[0064] The specific technical effects are as follows: 1. Full-range accuracy optimization: The ΔV channel is automatically activated in the ultra-low current region (<0.5% of the rated value) to avoid the time resolution limit of the FPGA; the Δt channel is mainly used in the range of 0.5% to full scale to give full play to its wide linearity and high stability advantages and significantly reduce the measurement error in the full dynamic range. 2. Enhanced anti-interference capability: Δ t Insensitive to amplitude noise, Δ V Immune to timing jitter, the two complement each other in their sensitivity to different types of interference, and their fusion effectively improves the overall signal-to-noise ratio and environmental adaptability of the system; 3. Low hardware compatibility and cost: Only the digital signal processing algorithm needs to be upgraded, without modifying the dual-core magnetic circuit structure, excitation circuit or power amplification hardware, and it can be seamlessly integrated into the existing zero-flux current transformer platform.

[0065] Example 1 ZCT System for HVDC Based on FPGA + 24-bit ADC Rated primary current: ±5 kA; Excitation frequency: 10 kHz; Time measurement unit: FPGA, with a typical zero-crossing detection time jitter of 100 ps; Voltage sampling unit: 24-bit ADC (AD7768), effective resolution 21 ENOB; Temperature sensor: PT1000, installed near the iron core; Preset current threshold: Set according to the system's time resolution and noise level, used to distinguish Δ t The effective working range of the channel; The weighting coefficients are adjusted as follows using the zero-flux current transformer demodulation method provided in this embodiment of the invention: If | I p |<threshold and SNRᵥ>SNR t Then reduce w 1. Prioritize the use of Δ V Signal; If | I p |< threshold but SNRᵥ≤SNR t Then improve w 1. Revert to Δ t Signal; If | I p |≥ threshold and SNRt >SNRᵥ, then increase w 1. Main Δ t Signal; If | I p | ≥ threshold but SNR t If ≤ SNRᵥ, then decrease w 1. Switch to Δ V Signal; When the ambient temperature exceeds the calibrated operating range, w 1. Apply temperature decay; A hysteresis mechanism is introduced in the threshold switching region to prevent frequent oscillations.

[0066] Figure 3 A schematic diagram of a device for demodulating a zero-flux current transformer according to an embodiment of the present invention is shown.

[0067] like Figure 3 As shown, the device includes: The acquisition unit 301 is used to acquire the induced voltage signal of the first iron core and the second iron core, the amplitude of the primary current, and the ambient temperature. The first processing unit 302 is used to obtain the time difference Δ between the saturation zero-crossing points of the two iron cores based on the induced voltage signals of the first and second iron cores. t and Δ t The signal-to-noise ratio of the channel and the amplitude difference Δ of the peak voltage before saturation of the two iron cores. V and Δ V The signal-to-noise ratio of the channel; The second processing unit 303 is used to process data based on the primary current amplitude, ambient temperature, and Δ... t The signal-to-noise ratio and Δ of the channel V The signal-to-noise ratio of the channel is obtained as Δ. t Channel weighting coefficient w 1 and Δ V Channel weighting coefficient w 2, of which w 1+ w 2 = 1; The third processing unit 304 is used for processing based on Δ t Δ V , w 1 and w 2. Obtain the fusion error signal; Feedback unit 305 is used to output a fusion error signal to the feedback controller to generate a feedback current to maintain a zero flux state.

[0068] Furthermore, the second processing unit 302 is also used for: Based on Δ t and Δ VThe relative magnitudes of the channel signal-to-noise ratios yield the weighting coefficients. w 1 and w The base weight is 2; The weighting coefficients are based on the primary current amplitude and ambient temperature, respectively. w 1 and w The base weights of 2 are adjusted to obtain the final weight coefficients. w 1 and w 2.

[0069] Furthermore, based on the primary current amplitude, the weighting coefficients are adjusted. w 1 and w The basic weights of 2 have been adjusted, including: Based on the magnitude of the primary current, a current confidence factor is obtained, and the current confidence factor is used to adjust the weighting coefficients. w 1 and w The base weights of 2 are adjusted.

[0070] Furthermore, based on ambient temperature, the weighting coefficients are adjusted. w 1 and w The basic weights of 2 have been adjusted, including: When the ambient temperature exceeds the calibrated operating range, the weighting coefficients are adjusted. w 1. Apply temperature decay.

[0071] Furthermore, the second processing unit 303 is also used for: When the duration of a single current amplitude exceeding a preset current threshold reaches a preset time, the current confidence factor is used to adjust the weighting coefficients. w 1 and w The base weights of 2 are adjusted.

[0072] Furthermore, the third processing unit 304 is also used for: The fusion error signal is obtained using the following formula: ; in, For Δ t Δ V Dimensionless quantity.

[0073] In the above embodiment, the time difference Δ between the saturation zero-crossing points of the two iron cores is obtained based on the induced voltage signals of the first and second iron cores. t and Δ t The signal-to-noise ratio of the channel and the amplitude difference Δ of the peak voltage before saturation of the two iron cores. V and Δ V The signal-to-noise ratio of the channel, combined with the primary current amplitude and ambient temperature, is dynamically adjusted to Δ. t and Δ VThe weighting coefficients of the channels are used to obtain the fusion error signal, which enables high-precision and robust current measurement across the entire range and under all operating conditions.

[0074] It should be noted that the apparatus provided in the above embodiments is only illustrated by the division of the above functional modules. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. In addition, the apparatus and method embodiments provided in the above embodiments belong to the same concept, and their specific implementation process can be found in the method embodiments, which will not be repeated here.

[0075] This invention also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the zero-flux current transformer demodulation method provided in the above embodiments.

[0076] This invention also provides an electronic device, including: a processor; a memory for storing processor-executable instructions; the processor being configured to read the executable instructions from the memory and execute the instructions to implement the zero-flux current transformer demodulation method provided in the above embodiments.

[0077] The invention has been described with reference to a few embodiments. However, as will be known to those skilled in the art, and as defined in the appended claims, other embodiments besides those disclosed above fall equivalently within the scope of the invention.

[0078] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the art, unless otherwise expressly defined herein. All references to “a / the / the [device, component, etc.]” ​​are openly interpreted as at least one instance of said device, component, etc., unless otherwise expressly stated. The steps of any method disclosed herein need not be performed in the exact order disclosed unless explicitly stated otherwise.

[0079] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0080] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0081] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0082] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0083] 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 scope of protection of the claims of the present invention.

Claims

1. A method of zero flux current transformer demodulation, characterized by, The method employs a dual-core differential structure and includes: Acquire the induced voltage signals of the first and second iron cores, the amplitude of the primary current, and the ambient temperature; Based on the induced voltage signals of the first and second cores, the time difference Δ of the two-core saturation zero-crossing points is obtained t and Δ t The signal-to-noise ratio of the channel, the amplitude difference Δ of the peak voltage before the saturation of the two cores V and Δ V The signal-to-noise ratio of the channel; based on the primary current amplitude, the ambient temperature, Δ t the signal-to-noise ratio of the channel and Δ V the signal-to-noise ratio of the channel, Δ t the weight coefficient of the channel w 1 and Δ V the weight coefficient of the channel w 2, wherein w 1+ w 2=1; based on Δ t , Δ V , w 1 and w 2, a fusion error signal is obtained; The fusion error signal is output to the feedback controller to generate a feedback current to maintain the zero flux state.

2. The method according to claim 1, characterized in that, The Δ t The signal-to-noise ratio of the channel and the Δ V The signal-to-noise ratio of the channel, and the Δ t The weight coefficient of the channel w 1 and the Δ V The weight coefficient of the channel w 2, include: Based on Δ t and Δ V The relative size of the channel signal-to-noise ratio, get the weight coefficient w 1 and w 2 base weight; The base weight of the weight coefficients w 1 and w 2 is corrected based on the amplitude of the primary current and the ambient temperature respectively, to obtain the final weight coefficients w 1 and w 2.

3. The method according to claim 2, characterized in that, The weight coefficient is corrected based on the amplitude of the primary current w 1 and w 2, including: Based on the magnitude of the primary current, a current confidence factor is obtained, and the current confidence factor is used to adjust the weighting coefficients. w 1 and w The basic weights of 2 are adjusted.

4. The method according to claim 2, characterized in that, The weighting coefficients are based on ambient temperature. w 1 and w The basic weights of 2 have been adjusted, including: When the ambient temperature exceeds the calibrated operating range, the weighting coefficients are adjusted. w 1. Apply temperature decay.

5. The method according to claim 3, characterized in that, The method further includes: When the duration of a single current amplitude exceeding a preset current threshold reaches a preset time, the current confidence factor is used to adjust the weighting coefficients. w 1 and w The basic weights of 2 are adjusted.

6. The method according to claim 1, characterized in that, The Δ-based t Δ V , w 1 and w 2. Obtain the fusion error signal, including: The fusion error signal is obtained using the following formula: ； in, For Δ t Δ V Dimensionless quantity.

7. A device for demodulating a zero-flux current transformer, characterized in that, The device, employing a dual-core differential structure, includes: The acquisition unit is used to acquire the induced voltage signal of the first iron core and the second iron core, the amplitude of the primary current, and the ambient temperature. The first processing unit is used to obtain the time difference Δ between the saturation zero-crossing points of the two iron cores based on the induced voltage signals of the first and second iron cores. t and Δ t The signal-to-noise ratio of the channel and the amplitude difference Δ of the peak voltage before saturation of the two iron cores. V and Δ V The signal-to-noise ratio of the channel; The second processing unit is used to process data based on the primary current amplitude, ambient temperature, and Δ. t The signal-to-noise ratio and Δ of the channel V The signal-to-noise ratio of the channel is obtained as Δ. t Channel weighting coefficient w 1 and Δ V Channel weighting coefficient w 2, of which w 1+ w 2 = 1; The third processing unit is used for processing based on Δ t Δ V , w 1 and w 2. Obtain the fusion error signal; The feedback unit is used to output the fusion error signal to the feedback controller to generate a feedback current to maintain the zero flux state.

8. The apparatus according to claim 7, characterized in that, The second processing unit is further configured to: Based on Δ t and Δ V The relative magnitudes of the channel signal-to-noise ratios yield the weighting coefficients. w 1 and w The base weight is 2; The weighting coefficients are based on the primary current amplitude and ambient temperature, respectively. w 1 and w The base weights of 2 are adjusted to obtain the final weight coefficients. w 1 and w 2.

9. The apparatus according to claim 8, characterized in that, The weighting coefficients are based on the primary current amplitude. w 1 and w The basic weights of 2 have been adjusted, including: Based on the magnitude of the primary current, a current confidence factor is obtained, and the current confidence factor is used to adjust the weighting coefficients. w 1 and w The basic weights of 2 are adjusted.

10. The apparatus according to claim 8, characterized in that, The weighting coefficients are based on ambient temperature. w 1 and w The basic weights of 2 have been adjusted, including: When the ambient temperature exceeds the calibrated operating range, the weighting coefficients are adjusted. w 1. Apply temperature decay.

11. The apparatus according to claim 9, characterized in that, The second processing unit is further configured to: When the duration of a single current amplitude exceeding a preset current threshold reaches a preset time, the current confidence factor is used to adjust the weighting coefficients. w 1 and w The basic weights of 2 are adjusted.

12. The apparatus according to claim 7, characterized in that, The third processing unit is further configured to: The fusion error signal is obtained using the following formula: ； in, For Δ t Δ V Dimensionless quantity.

13. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method described in any one of claims 1-6.

14. An electronic device comprising: processor; Memory used to store the processor's executable instructions; The processor is configured to read the executable instructions from the memory and execute the instructions to implement the method according to any one of claims 1-6.

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