A wide-band AC / DC magnetic sensor with a milliampere to hundred-ampere range and a large dynamic range

Abstract

The present invention discloses a wide-band AC / DC magnetic sensor with a large dynamic range from milliampere to hundred-ampere, comprising: a first sensing circuit, a second sensing circuit, a power frequency current conditioning circuit, and a weak current conditioning circuit. The first sensing circuit and the power frequency current conditioning circuit use tunneling magnetoresistance technology and the principle of magnetic balance to sense the wide-band mixed current to be measured and extract the power frequency current from the wide-band mixed current to be measured, and input the power frequency current into the second sensing circuit; the second sensing circuit uses the principle of magnetic balance to sense the wide-band mixed current to be measured, receives the power frequency current, offsets the power frequency portion thereof, uses tunneling magnetoresistance technology to sense the offset weak current, and the weak current conditioning circuit measures the weak current. By implementing the present invention, a power frequency current conditioning circuit is provided in combination with the first sensing circuit to extract the power frequency current, and the power frequency current is input into the second sensing circuit to offset the power frequency portion, thereby avoiding the problem that the large power frequency current may cause the inability to measure the weak current.

Description

Technical Field

[0001] The present invention relates to the field of electrical measurement technology, and in particular to a wide-band AC / DC magnetic sensor with a large dynamic range from milliampere to hundred-ampere levels. Background Art

[0002] Broadband hybrid current measurement is in high demand in future power systems. A typical scenario involves connecting distributed power sources (DGs), requiring simultaneous measurement of 50 Hz power frequency load current, DC, and harmonic components. This ensures that the DC and harmonic components of the DGs remain low, preventing damage to the grid's safe operation. Another typical scenario involves locating single-phase ground faults on a line. This involves actively injecting a high-frequency current of several hundred Hz, which travels along the ground to the fault point. The fault's location can be determined by determining whether a high-frequency characteristic signal is present in current sensors near the fault point.

[0003] Typically, the amplitudes of the various frequency components of a broadband mixed current can vary significantly. For example, when troubleshooting a ground fault, the high-frequency injection current ranges from hundreds of milliamperes to amperes, while the power-frequency load current is in the hundreds of amperes. Therefore, a current sensor is required that can simultaneously and accurately measure the various frequency components of the mixed current with amplitudes of varying magnitudes. Traditional technologies such as shunts, current transformers, and fiber-optic current transformers are limited by sensitivity, size, and mounting methods, making it difficult to measure weak currents. Furthermore, when using tunneling magnetoresistance technology for broadband circuit measurements, the power-frequency load current can cause the chip to saturate, making weak current measurements impossible. Summary of the Invention

[0004] In view of this, an embodiment of the present invention provides a wide-band AC / DC magnetic sensitive sensor with a large dynamic range from milliampere to hundred-ampere level, so as to solve the technical problem in the prior art of using tunneling magnetoresistance technology for wide-band circuit measurement, in which the power frequency load current causes chip saturation and weak current measurement cannot be performed.

[0005] The technical solutions provided by the embodiments of the present invention are as follows:

[0006] A first aspect of an embodiment of the present invention provides a wide-band AC / DC magnetic sensor with a large dynamic range from milliampere to hundred-ampere, comprising: a first sensing circuit, a second sensing circuit, an industrial frequency current conditioning circuit, and a weak current conditioning circuit, wherein the first sensing circuit and the second sensing circuit are respectively connected to the industrial frequency current conditioning circuit, and the second sensing circuit is connected to the weak current conditioning circuit; the first sensing circuit and the industrial frequency current conditioning circuit use tunneling magnetoresistance technology and magnetic balance principle to sense the wide-band mixed current to be measured and extract the industrial frequency current from the wide-band mixed current to be measured, obtain the industrial frequency feedback current and input it into the second sensing circuit; the second sensing circuit uses the magnetic balance principle to sense the wide-band mixed current to be measured, receives the industrial frequency feedback current to offset the industrial frequency part of the wide-band mixed current to be measured, uses tunneling magnetoresistance technology to sense the weak current remaining after offsetting the industrial frequency part, and the weak current conditioning circuit measures the weak current.

[0007] Optionally, the first induction circuit includes: a first magnetic core with an air gap, a first feedback coil and a high saturation magnetoresistance chip, the first feedback coil is wound on the first magnetic core, the high saturation magnetoresistance chip is arranged in the air gap, and the high saturation magnetoresistance chip uses tunneling magnetoresistance technology to sense the broadband mixed current to be measured.

[0008] Optionally, the second induction circuit includes: a second magnetic core with an air gap, a second feedback coil and a high-sensitivity magnetoresistive chip, the second feedback coil is wound on the first magnetic core, the high-sensitivity magnetoresistive chip is arranged in the air gap, and the high-sensitivity magnetoresistive chip uses tunneling magnetoresistive technology to sense and offset the weak current remaining after the power frequency part.

[0009] Optionally, the industrial frequency current conditioning circuit includes: a compensation circuit, a sampling resistor, a current mirror circuit and a bandpass filter; one end of the compensation circuit is connected to the high saturation magnetoresistance chip, the other end of the compensation circuit is connected to one end of the first feedback coil, the other end of the first feedback coil is connected to one end of the current mirror circuit through the sampling resistor, and the compensation circuit is used to record the wide-band mixed current to be measured induced by the high saturation magnetoresistance chip; the other end of the current mirror circuit is connected to one end of the bandpass filter, and the other end of the bandpass filter is connected to the second feedback coil, the current mirror circuit is used to copy and output the wide-band mixed current to be measured recorded by the compensation circuit, and the bandpass filter is used to extract the industrial frequency current from the wide-band mixed current to be measured output by the current mirror circuit to obtain the industrial frequency feedback current and input it into the second feedback coil.

[0010] Optionally, the compensation circuit includes an amplifying circuit, an integrating circuit, a filtering circuit and a push-pull output circuit connected in sequence.

[0011] Optionally, the current mirror circuit includes: a first resistor, a first transistor and a second transistor, one end of the first resistor is connected to the other end of the compensation circuit, the other end of the first resistor is connected to the collector and base of the first transistor and the base of the second transistor, the emitter of the first transistor is connected to the emitter of the second transistor and grounded, and the collector of the second transistor is connected to one end of the bandpass filter.

[0012] Optionally, the bandpass filter includes a first capacitor, a second capacitor and a second resistor, one end of the first capacitor is connected to the other end of the current mirror circuit and one end of the second resistor, the other end of the second resistor is connected to one end of the second capacitor, and the other end of the first capacitor is connected to the other end of the second capacitor and grounded.

[0013] Optionally, the weak current conditioning circuit includes: an amplifying and filtering circuit and a notch filter.

[0014] Optionally, the milliampere to hundred-ampere wide dynamic range AC / DC magnetic sensor further includes: a power supply for supplying power to the first sensing circuit, the second sensing circuit, the power frequency current conditioning circuit and the weak current conditioning circuit.

[0015] Optionally, the power supply is supplied by external input electrical energy, photovoltaic energy storage or magnetic field energy extraction.

[0016] The technical solution of the present invention has the following advantages:

[0017] The embodiment of the present invention provides a wide-band AC / DC magnetic sensor with a large dynamic range from milliampere to hundred-ampere, which uses tunneling magnetoresistance technology to sense the wide-band mixed current to be measured, giving full play to the advantages of tunneling magnetoresistance current measurement technology such as high sensitivity, low power consumption, simple structure and non-invasiveness. At the same time, an industrial frequency current conditioning circuit is provided in combination with the first sensing circuit to adopt the magnetic balance principle to realize the measurement of the wide-band mixed current to be measured and the extraction of the industrial frequency current. The obtained industrial frequency feedback current is input into the second sensing circuit, and the industrial frequency part of the wide-band mixed current to be measured sensed by the second sensing circuit is offset, thereby avoiding the problem that the large industrial frequency current may cause the second sensing circuit to saturate and the weak current measurement cannot be performed.

[0018] The wide-band AC / DC magnetic sensor with a milliampere to 100-ampere wide dynamic range, provided by the embodiments of the present invention, employs a high-saturation magnetoresistive chip and a high-sensitivity magnetoresistive chip. The high-saturation magnetoresistive chip measures high-amplitude power-frequency currents and simultaneously injects the power-frequency current into a second feedback coil to offset the induced magnetic field generated by the high-amplitude power-frequency current, thus preventing saturation of the high-sensitivity tunneling magnetoresistive chip. As a result, the high-sensitivity tunneling magnetoresistive chip can operate normally, measuring the weak DC, harmonic, and interharmonic components superimposed on the high-amplitude power-frequency current. This sensor can be applied to scenarios such as high-precision harmonic and DC bias current monitoring in distributed power supply access scenarios and single-phase ground fault detection based on high-frequency injection. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 This is a structural block diagram of a wide-band AC / DC magnetic sensor with a large dynamic range from milliampere to hundred-ampere level according to an embodiment of the present invention;

[0021] Figure 2 Schematic diagram of the structure of a wide-band AC / DC magnetic sensor with a large dynamic range from milliampere to hundred-ampere level according to an embodiment of the present invention;

[0022] Figure 3 A schematic structural diagram of a wide-band AC / DC magnetic sensor with a large dynamic range from milliampere to hundred-ampere level in another embodiment of the present invention;

[0023] Figure 4 A schematic diagram of a partial circuit structure of a wide-band AC / DC magnetic sensor with a large dynamic range from milliampere to hundred-ampere levels according to an embodiment of the present invention;

[0024] Figure 5 Schematic diagram of the structure of a weak current measurement circuit in an embodiment of the present invention;

[0025] Figure 6 A signal chain logic diagram consisting of the connection relationship of various circuits in an embodiment of the present invention;

[0026] Figure 7 This is a signal chain logic diagram based on actual parameter simulation in an embodiment of the present invention;

[0027] FIG8( a ) and FIG8 ( b ) are schematic diagrams of the power frequency current waveform and the weak current waveform respectively obtained by simulation in an embodiment of the present invention;

[0028] FIG9( a ) and FIG9 ( b ) are schematic diagrams of the magnitude of the induced magnetic field when the overhead line active injection method is applied to the ground fault detection scenario according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] As mentioned in the background technology section, traditional current meters, current transformers, and fiber-optic current transformers are limited by sensitivity, size, and installation methods, making it difficult to measure weak currents. In recent years, tunneling magnetoresistive (TMR) technology has garnered widespread attention due to its high sensitivity, adjustable magnetic saturation range, compact size, and non-invasive nature. In related technologies, TMR technology is used for broadband current measurement by combining a closed-loop sensor based on a high-sensitivity TMR sensor chip with an open-loop sensor based on a low-sensitivity sensor chip, thereby increasing the sensor's range.

[0030] However, this technology is not suitable for large dynamic range and wide-band mixed current measurement because the power frequency load current is generally large, which will cause the high-sensitivity sensor chip to saturate and cannot measure weak DC, harmonic and interharmonic components.

[0031] In view of this, an embodiment of the present invention proposes a wide-band AC / DC magnetic sensor with a large dynamic range from milliampere to hundred-ampere. By setting a first sensing circuit, a second sensing circuit, an industrial frequency current conditioning circuit and a weak current conditioning circuit, the first sensing circuit and the industrial frequency current conditioning circuit use tunneling magnetoresistance technology and the principle of magnetic balance to sense the wide-band mixed current to be measured and extract the industrial frequency current from the wide-band mixed current to be measured, and obtain the industrial frequency feedback current to input into the second sensing circuit; the second sensing circuit uses the principle of magnetic balance to sense the wide-band mixed current to be measured, receives the industrial frequency feedback current to offset the industrial frequency part of the wide-band mixed current to be measured, and uses tunneling magnetoresistance technology to sense the weak current remaining after offsetting the industrial frequency part, and the weak current conditioning circuit measures the weak current. By extracting the power frequency current and inputting it into the second sensing circuit, the power frequency portion of the broadband mixed current to be measured is offset, thus avoiding the problem of saturation and inability to measure weak currents when the second sensing circuit uses tunneling magnetoresistance technology for current measurement. At the same time, the arrangement of the first sensing circuit, the second sensing circuit, the power frequency current conditioning circuit, and the weak current conditioning circuit enables the measurement of both power frequency and weak currents. This solves the problem in related technologies where traditional current transformers have difficulty measuring weak currents in broadband mixed currents.

[0032] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0033] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components; wireless connections or wired connections. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0035] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0036] The embodiment of the present invention provides a wide frequency AC / DC magnetic sensor with a large dynamic range from milliampere to hundred ampere. Figure 1 As shown, it includes: a first sensing circuit 10, a second sensing circuit 20, a power frequency current conditioning circuit 40 and a weak current conditioning circuit 30. The first sensing circuit 10 and the second sensing circuit 20 are respectively connected to the power frequency current conditioning circuit 40, and the second sensing circuit 20 is connected to the weak current conditioning circuit 30; the first sensing circuit 10 and the power frequency current conditioning circuit 40 use tunneling magnetoresistance technology and magnetic balance principle to sense the broadband mixed current to be measured and extract the power frequency current from the broadband mixed current to be measured, obtain the power frequency feedback current and input it into the second sensing circuit 20; the second sensing circuit 20 uses the magnetic balance principle to sense the broadband mixed current to be measured, receives the power frequency feedback current to offset the power frequency part of the broadband mixed current to be measured, and uses tunneling magnetoresistance technology to sense the weak current remaining after offsetting the power frequency part, and the weak current conditioning circuit 30 measures the weak current. It should be noted that the power frequency feedback current input into the second sensing circuit is the power frequency current in the broadband mixed current to be measured extracted by the power frequency current conditioning circuit. This power frequency current is input into the second sensing circuit to realize a negative feedback function. Therefore, the power frequency current input into the second sensing circuit is referred to as the power frequency feedback current.

[0037] The embodiment of the present invention provides a wide-band AC / DC magnetic sensor with a large dynamic range from milliampere to hundred-ampere, which uses tunneling magnetoresistance technology to sense the wide-band mixed current to be measured, giving full play to the advantages of tunneling magnetoresistance current measurement technology such as high sensitivity, low power consumption, simple structure and non-invasiveness. At the same time, an industrial frequency current conditioning circuit is provided in combination with the first sensing circuit to adopt the magnetic balance principle to achieve the measurement of the wide-band mixed current to be measured and the extraction of the industrial frequency current. The industrial frequency current is input into the second sensing circuit, and the industrial frequency portion of the wide-band mixed current to be measured sensed by the second sensing circuit is offset, thereby avoiding the problem that the large industrial frequency current may cause the second sensing circuit to saturate and make it impossible to measure weak currents.

[0038] In one embodiment, if Figure 2 and Figure 3 As shown, the first sensing circuit 10 includes: a first magnetic core 11 with an air gap, a first feedback coil 12, and a high-saturation magnetoresistive chip. The first feedback coil 12 is wound around the first magnetic core 11, and the high-saturation magnetoresistive chip is disposed in the air gap. The high-saturation magnetoresistive chip uses tunneling magnetoresistive technology to sense the broadband mixed current to be measured. The second sensing circuit 20 includes: a second magnetic core 21 with an air gap, a second feedback coil 22, and a high-sensitivity magnetoresistive chip. The second feedback coil 22 is wound around the first magnetic core 11, and the high-sensitivity magnetoresistive chip is disposed in the air gap. The high-sensitivity magnetoresistive chip uses tunneling magnetoresistive technology to sense the weak current remaining after offsetting the power frequency component.

[0039] Specifically, if Figure 2 As shown, in order to facilitate the first induction circuit and the second induction circuit to sense the broadband mixed current to be measured, the first magnetic core and the second magnetic core can be set on the outside of the conductor to be measured, such as a copper busbar, so that the conductor to be measured passes through the inner holes of the first magnetic core and the second magnetic core. At the same time, the first feedback coil and the second feedback coil are respectively wound on the two magnetic cores, and the high saturation magnetoresistive chip and the high sensitivity magnetoresistive chip are respectively set in the air gap of the corresponding magnetic cores. When the broadband mixed current to be measured passes through the conductor to be measured, the first feedback coil and the second feedback coil wound on the first magnetic core and the second magnetic core respectively constitute the secondary coils corresponding to the conductor to be measured, thereby realizing the sensing of the broadband mixed current to be measured in the conductor to be measured; at the same time, the power frequency current conditioning circuit is combined with the power frequency current sensed and extracted by the first induction circuit as the power frequency feedback current and input into the second induction circuit. The second feedback coil in the second induction circuit receives the power frequency feedback current, thereby offsetting the power frequency portion of the broadband mixed current to be measured sensed by it as the secondary coil, thereby facilitating the high sensitivity magnetoresistive chip to sense the remaining weak current in the broadband mixed current to be measured.

[0040] When current flows through the conductor being measured, the two magnetic cores concentrate the induced magnetic field generated by the conductor in space. The magnetic field in the air gap is stronger, so placing the chip in the air gap makes it easier to sense current. High-saturation magnetoresistive chips have lower sensitivity than high-sensitivity magnetoresistive chips, but they are less likely to saturate when current is high. Therefore, high-saturation magnetoresistive chips are used to sense large currents, i.e., industrial frequency currents, while high-sensitivity magnetoresistive chips are used to sense small currents, i.e., weak currents.

[0041] In one embodiment, if Figure 4 As shown, the power frequency current conditioning circuit 40 includes: a compensation circuit 41, a sampling resistor R B , current mirror circuit 42 and bandpass filter 43; one end of the compensation circuit 41 is connected to the high saturation magnetoresistive chip, the other end of the compensation circuit 41 is connected to one end of the first feedback coil 12, and the other end of the first feedback coil 12 is connected to the sampling resistor R B One end of the current mirror circuit 42 is connected, and the compensation circuit 41 is used to record the broadband mixed current to be measured induced by the high saturation magnetoresistive chip; the other end of the current mirror circuit 42 is connected to one end of the bandpass filter 43, and the other end of the bandpass filter 43 is connected to the second feedback coil 22. The current mirror circuit 42 is used to copy and output the broadband mixed current to be measured recorded by the compensation circuit 41, and the bandpass filter 43 is used to extract the industrial frequency current from the broadband mixed current to be measured output by the current mirror circuit 42 to obtain the industrial frequency feedback current and input it into the second feedback coil 22.

[0042] Specifically, if Figure 4 As shown, the compensation circuit includes an amplifier circuit, an integration circuit, a filter circuit and a push-pull output circuit connected in sequence. Among them, the amplifier circuit mainly includes the first operational amplifier U1, the integration circuit mainly includes the second operational amplifier U2, the filter circuit mainly includes the third operational amplifier U3, the push-pull output circuit includes the third transistor Q3, the fourth transistor Q4, the first diode D1 and the second diode D2. At the same time, the compensation circuit also includes other resistors, capacitors, etc., which work together with the main components to achieve corresponding functions. At the same time, Figure 4 In the example, the first feedback coil 12 is equivalent to the tenth resistor R10, the eleventh resistor R11, the first inductor AM1 and the second inductor AM2; the second feedback coil is equivalent to the twelfth resistor R12 and the third inductor L1. In addition, Figure 4 Where I represents the broadband mixed current to be measured flowing through the conductor to be measured, n1 represents the primary coil, and n2 represents the secondary coil.

[0043] like Figure 4As shown, the current mirror circuit includes: a first resistor R1, a first transistor Q1, and a second transistor Q2, one end of the first resistor R1 is connected to the other end of the compensation circuit, the other end of the first resistor R1 is connected to the collector and base of the first transistor Q1 and the base of the second transistor Q2, the emitter of the first transistor Q1 is connected to the emitter of the second transistor Q2 and is grounded, and the collector of the second transistor Q2 is connected to one end of the bandpass filter. The bandpass filter includes a first capacitor C1, a second capacitor C2, and a second resistor R2, one end of the first capacitor C1 is connected to the other end of the current mirror circuit and one end of the second resistor R2, the other end of the second resistor R2 is connected to one end of the second capacitor C2, and the other end of the first capacitor C1 is connected to the other end of the second capacitor C2 and is grounded.

[0044] Specifically, by setting an amplifier circuit, an integration circuit, a filter circuit and a push-pull output circuit in the compensation circuit, the amplifier circuit and the integration circuit constitute a proportional integrator, and the compensation circuit is connected to the high saturation magnetoresistive chip. The proportional integrator can record the current output and historical output of the high saturation magnetoresistive chip. Since the output of the high saturation magnetoresistive chip is proportional to the error between the primary current and the secondary current passing through the first magnetic core, the proportional-integrator records the error between the primary current and the secondary current. The output of the compensation circuit is connected to one end of the first feedback coil, and the other end of the first feedback coil is connected to the sampling resistor of the power frequency current conditioning circuit. Figure 3 and Figure 4 As shown, the output of the compensation circuit is recorded as the main output terminal, and the output of the current mirror circuit is recorded as the auxiliary output terminal.

[0045] In one embodiment, if Figure 5 As shown, the weak current conditioning circuit includes: an amplifier filter circuit and a trap. Among them, the amplifier filter circuit is mainly composed of a fourth operational amplifier U4 and a thirteenth resistor R13, and the trap includes a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, a fourth capacitor C4, a fifth capacitor C5 and a sixth capacitor C6. Figure 3 As shown, the wide-band AC / DC magnetic sensor with a milliampere to hundred-ampere wide dynamic range also includes a power supply for the first sensing circuit, the second sensing circuit, the power frequency current conditioning circuit, and the weak current conditioning circuit. The power supply is powered by external input power, photovoltaic energy storage, or magnetic field energy extraction.

[0046] like Figure 6 and Figure 7 As shown ( Figure 7 The measurement principle of the wide-band AC / DC magnetic sensor with a large dynamic range from milliampere to hundred-ampere is explained as follows:

[0047] When the broadband mixed current to be measured flows through the conductor to be measured, for the first induction circuit, according to the magnetic potential balance principle of the current transformer, the primary current I1 (broadband mixed current to be measured) and the excitation current I m It forms a balanced relationship with the secondary current I2.

[0048]

[0049] Where n1 is the number of turns of the primary winding. When the conductor to be measured is a single wire or a copper bar structure, n1 is equal to 1. n2 is the number of turns of the secondary winding, that is, the number of turns of the first feedback coil.

[0050] For the first magnetic core, the excitation current generates a magnetic potential in the air gap, and the conversion relationship is:

[0051]

[0052] Where μ0 is the vacuum permeability, A c is the core air gap area, l g is the air gap length, Figure 6 middle,

[0053] Part of the excitation potential is converted into the excitation potential of the secondary winding, as shown in the following formula:

[0054]

[0055] Among them L m is the excitation inductance, V2 is the excitation potential, and the corresponding expression in the Laplace domain is shown as follows:

[0056] V2=sL m I m

[0057] Where s represents the Laplace domain complex frequency.

[0058] At the same time, the excitation magnetic potential excites the high saturation magnetoresistive chip placed in the air gap to generate output, which is recorded as V after the compensation circuit. Amp , and the excitation potential together act on the first feedback coil and the sampling resistor R B In the series circuit formed, the current flowing through the first feedback coil at this time is expressed by the following formula:

[0059]

[0060] Wherein, r2 represents the equivalent resistance of the first feedback coil.

[0061] At this time, the sampling resistor output is:

[0062]

[0063] If the high saturation magnetoresistive chip always works in the linear region, then V Amp Can be expressed as.

[0064]

[0065] where K h is the sensitivity of the high saturation magnetoresistive chip, G c (s) is the transfer function of the compensation circuit.

[0066] When the magnetic balance system composed of the first induction circuit and the power frequency current conditioning circuit enters the magnetic balance state, V2, V Amp , I2, I1 and I m Substitute the expression into the following magnetic potential balance equation:

[0067]

[0068]

[0069] From the above formula, we can see that if the transfer function G of the compensation circuit is reasonably designed, c (s) makes H(s) large enough and stable, then the magnetic balance system can enter the locked state, that is, the secondary current I2 locks the primary current. According to the output expression of the sampling resistor, it can be known that V out1 The output is proportional to the primary current. The primary current, that is, the power frequency current in the broadband mixed current to be measured, can be extracted through a bandpass filter.

[0070] At the same time, the current mirror circuit copies the secondary current I2 and inputs the power frequency part into the second feedback coil of the second magnetic core through the bandpass filter. For the second induction circuit, according to the principle of magnetic potential balance, the primary current I'1 and the excitation current I' m It forms a balanced relationship with the secondary current I'2:

[0071]

[0072] As shown in the above equation, due to the current mirror circuit and bandpass filter, the secondary current I'2 of the second feedback coil on the second magnetic core is the power frequency portion of the secondary current I2 of the first feedback coil on the first magnetic core. Therefore, the power frequency portion of the excitation magnetic potential of the second magnetic core is offset, preventing the high-sensitivity magnetoresistive chip from saturating. At this time, the excitation current I' m The frequency of the high-sensitivity magnetoresistive chip contains only weak characteristic current at the excitation current I' m Under the excitation of , the corresponding voltage signal is generated and sampled by the weak current conditioning circuit.

[0073] Figure 8(a) and Figure 8(b) are based on Figure 6The established Simulink model and theoretical calculation results clearly demonstrate the waveform changes caused by large-amplitude power-frequency currents and weak currents such as DC, harmonics, and interharmonics. Before 0.2 seconds of the first cycle, the first induction circuit and the power-frequency current conditioning circuit have not yet reached magnetic equilibrium, and the secondary current has not locked onto the primary current. The feedback magnetic potential in the second core does not fully offset the power-frequency magnetic potential in the primary current, causing the output waveform to oscillate. After 0.2 seconds, when the secondary feedback current has locked onto the primary current, the power-frequency feedback magnetic potential in the second core offsets the power-frequency magnetic potential in the primary current. The high-sensitivity magnetoresistive chip is only affected by the high-frequency magnetic potential, outputting a voltage waveform corresponding to the frequency.

[0074] This embodiment of the present invention offsets the induced magnetic field generated by the high-amplitude power-frequency current by injecting power-frequency current into the second feedback coil, thus preventing saturation of the high-sensitivity tunneling magnetoresistive chip. Taking the overhead line active injection method for ground fault detection as an example, assuming the line has a rated current of 600A and operates at 50% of the rated load, the current injected by the high-frequency method is coupled to the line through the grounding point with an amplitude of 0.1A and 800Hz. The comparison of the induced magnetic field generated by a current with a frequency of 50Hz and an amplitude of 300A and a current with a frequency of 800Hz and an amplitude of 0.1A is shown in Figures 9(a) and 9(b). It can be seen that the induced magnetic field generated by a 50Hz current is approximately 70mT, while the induced magnetic field generated by an 800Hz current is approximately 20μT. To measure high-frequency, weak currents, the equivalent magnetic noise of the tunneling magnetoresistive device should be in the nT level. However, the magnetic saturation strength of low-noise, high-sensitivity tunneling magnetoresistive devices typically does not exceed 1mT. Therefore, without offsetting the power frequency magnetic field, the high-sensitivity tunneling magnetoresistive device will always be in a saturated state and unable to accurately measure the magnetic field generated by weak currents. However, the method proposed in this invention can simultaneously measure 600A power frequency current, mA-level DC, harmonics, and interharmonics. Using existing commercial tunneling magnetoresistive sensor chips, the measurement accuracy can be controlled to 0.2%-1%.

[0075] The wide-band AC / DC magnetic sensor with a milliampere to 100-ampere wide dynamic range, provided by the embodiments of the present invention, employs a high-saturation magnetoresistive chip and a high-sensitivity magnetoresistive chip. The high-saturation magnetoresistive chip measures high-amplitude power-frequency currents and simultaneously injects the power-frequency current into a second feedback coil to offset the induced magnetic field generated by the high-amplitude power-frequency current, thus preventing saturation of the high-sensitivity tunneling magnetoresistive chip. As a result, the high-sensitivity tunneling magnetoresistive chip can operate normally, measuring the weak DC, harmonic, and interharmonic components superimposed on the high-amplitude power-frequency current. This sensor can be applied to scenarios such as high-precision harmonic and DC bias current monitoring in distributed power supply access scenarios and single-phase ground fault detection based on high-frequency injection.

[0076] Although exemplary embodiments and their advantages have been described in detail, those skilled in the art may make various changes, substitutions, and modifications to these embodiments without departing from the spirit of the present invention and the scope of protection defined by the appended claims. Such modifications and variations fall within the scope defined by the appended claims. For other examples, those skilled in the art will readily appreciate that the order of the process steps may be varied while remaining within the scope of protection of the present invention.

[0077] Furthermore, the scope of application of the present invention is not limited to the processes, mechanisms, manufactures, compositions of matter, means, methods, and steps of the specific embodiments described in the specification. From the disclosure of the present invention, a person of ordinary skill in the art will readily understand that any currently existing or later developed processes, mechanisms, manufactures, compositions of matter, means, methods, or steps that perform substantially the same functions or achieve substantially the same results as the corresponding embodiments described herein may be applied in accordance with the present invention. Therefore, the claims appended hereto are intended to include within their scope such processes, mechanisms, manufactures, compositions of matter, means, methods, or steps.

Claims

1. A wide-band AC / DC magnetic sensor with a milliampere to hundred-ampere range, characterized in that: include: A first induction circuit, a second induction circuit, a power frequency current conditioning circuit, and a weak current conditioning circuit, wherein the first induction circuit and the second induction circuit are respectively connected to the power frequency current conditioning circuit, and the second induction circuit is connected to the weak current conditioning circuit; The first sensing circuit and the power frequency current conditioning circuit use tunneling magnetoresistance technology and magnetic balance principle to sense the broadband mixed current to be measured and extract the power frequency current from the broadband mixed current to be measured, thereby obtaining a power frequency feedback current which is input into the second sensing circuit; The second sensing circuit uses the magnetic balance principle to sense the broadband mixed current to be measured, receives the power frequency feedback current to offset the power frequency portion of the broadband mixed current to be measured, and uses tunneling magnetoresistance technology to sense the weak current remaining after offsetting the power frequency portion. The weak current conditioning circuit measures the weak current; The first sensing circuit includes: a first magnetic core with an air gap, a first feedback coil, and a high saturation magnetoresistive chip, wherein the first feedback coil is wound around the first magnetic core, the high saturation magnetoresistive chip is arranged in the air gap, and the high saturation magnetoresistive chip uses tunneling magnetoresistive technology to sense the broadband mixed current to be measured; The second induction circuit includes: a second magnetic core with an air gap, a second feedback coil and a high-sensitivity magnetoresistive chip, the second feedback coil is wound on the second magnetic core, the high-sensitivity magnetoresistive chip is arranged in the air gap, and the high-sensitivity magnetoresistive chip uses tunneling magnetoresistive technology to sense and offset the weak current remaining after the power frequency part.

2. The wide-band AC / DC magnetic sensor with a large dynamic range from milliampere to hundred-ampere according to claim 1, characterized in that: The power frequency current conditioning circuit includes: a compensation circuit, a sampling resistor, a current mirror circuit and a bandpass filter; One end of the compensation circuit is connected to the high saturation magnetoresistive chip, the other end of the compensation circuit is connected to one end of the first feedback coil, the other end of the first feedback coil is connected to one end of the current mirror circuit via the sampling resistor, and the compensation circuit is used to record the broadband mixed current to be measured induced by the high saturation magnetoresistive chip; The other end of the current mirror circuit is connected to one end of the bandpass filter, and the other end of the bandpass filter is connected to the second feedback coil. The current mirror circuit is used to copy and output the wide-band mixed current to be measured recorded by the compensation circuit, and the bandpass filter is used to extract the industrial frequency current from the wide-band mixed current to be measured output by the current mirror circuit to obtain an industrial frequency feedback current and input it into the second feedback coil.

3. The wide-band AC / DC magnetic sensor with a large dynamic range from milliampere to hundred-ampere according to claim 2, characterized in that: The compensation circuit includes an amplifier circuit, an integration circuit, a filter circuit and a push-pull output circuit which are connected in sequence.

4. The wide-band AC / DC magnetic sensor with a large dynamic range from milliampere to hundred-ampere according to claim 2, characterized in that: The current mirror circuit includes: a first resistor, a first transistor, and a second transistor, one end of the first resistor is connected to the other end of the compensation circuit, the other end of the first resistor is connected to the collector and base of the first transistor and the base of the second transistor, the emitter of the first transistor is connected to the emitter of the second transistor and is grounded, and the collector of the second transistor is connected to one end of the bandpass filter.

5. The wide-band AC / DC magnetic sensor with a large dynamic range from milliampere to hundred-ampere according to claim 2, characterized in that: The bandpass filter includes a first capacitor, a second capacitor and a second resistor, one end of the first capacitor is connected to the other end of the current mirror circuit and one end of the second resistor, the other end of the second resistor is connected to one end of the second capacitor, and the other end of the first capacitor is connected to the other end of the second capacitor and is grounded.

6. The wide-band AC / DC magnetic sensor with a large dynamic range from milliampere to hundred-ampere according to claim 1, characterized in that: The weak current conditioning circuit includes: an amplifying and filtering circuit and a notch filter.

7. The wide-band AC / DC magnetic sensor with a large dynamic range from milliampere to hundred-ampere according to claim 1, characterized in that: Also includes: A power supply is used to supply power to the first induction circuit, the second induction circuit, the power frequency current conditioning circuit and the weak current conditioning circuit.

8. The milliampere to hundred-ampere wide dynamic range AC / DC magnetic sensor according to claim 7, characterized in that: The power supply is supplied by external input electric energy, photovoltaic energy storage or magnetic field energy extraction.

Images