A magnetic field energy harvesting self-powered electromagnetic sensor and its interference suppression method

Abstract

The present invention provides a magnetic field energy harvesting self-powered electromagnetic sensor and an interference suppression method thereof. The magnetic sensor includes: a magnetic field energy harvesting device, a rectifying circuit, a discharging protection circuit, a micro energy management circuit, a TMR sensing circuit, and a control circuit. The steps of the interference suppression method include: adjusting the cable current, obtaining the upper and lower limits of the current excitation when the sensor is in three working states, as well as the TMR output values without energy harvesting interference and with energy harvesting interference; selecting points within each current range to obtain the TMR output functions without energy harvesting interference and with energy harvesting interference, and fitting to obtain the correction algorithms corresponding to the three working states; segmentally fitting the TMR output function with energy harvesting interference according to the corresponding correction algorithm to obtain the cable current value after interference suppression. Through the spatial position layout of each circuit in the magnetic field energy harvesting self-powered electromagnetic sensor, the interference of the alternating magnetic field generated by the magnetic field energy harvesting output on magnetic sensing is reduced, and the interference suppression method can improve the accuracy of cable current monitoring based on magnetic sensing.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular, to a magnetic field energy harvesting self-powered electromagnetic sensor and an interference suppression method thereof. Background Art

[0002] As the main carrier for electric energy transmission in the power transmission and distribution network, cables play a crucial role. In order to ensure the reliable and safe operation of cables, it is necessary to monitor the magnitude of the current in the cables using tunnel magnetoresistance (TMR) sensors. Currently, such sensors are mainly powered by batteries. However, due to the limitations of capacity and lifespan, the batteries need to be replaced regularly, which incurs high costs and is inconvenient. Therefore, an attractive and promising new power supply scheme is needed to enable the TMR to achieve continuous self-power supply.

[0003] Currently, common power supply methods include solar and wind power supply, vibration energy harvesting power supply, radio frequency energy harvesting power supply, and magnetic field energy harvesting, etc. Solar and wind power supply is greatly affected by weather, resulting in unstable power supply; vibration energy harvesting is not suitable because continuous vibration is required while the cable environment is relatively stable; moreover, both vibration energy harvesting and radio frequency energy harvesting have extremely low output power and cannot maintain the power supply of the TMR sensor; in contrast, magnetic field energy harvesting is gradually applied to the power supply of TMR sensors due to its advantages of simple structure, low cost, and relatively stable power supply.

[0004] Magnetic energy harvesting technology (MEH) is based on the law of electromagnetic induction and converts the magnetic field energy near the cable into electrical energy to power the TMR sensor. MEH is divided into invasive MEH and non-invasive MEH. Invasive MEH needs to clamp its magnetic core on the cable, so the size of its magnetic core needs to change according to the cross-sectional size of the cable, and the installation is extremely inconvenient. Moreover, the magnetic core of invasive MEH is prone to saturation under the condition of hundreds of amperes of cable current, resulting in low reliability. Non-invasive MEH only needs to be placed in an alternating magnetic field to harvest energy, with convenient and flexible installation. Additionally, the magnetic core of non-invasive MEH is non-closed and is difficult to saturate even under thousands of amperes of current, which is an effective way for the TMR sensor to achieve self-power supply.

[0005] The working principle of TMR is based on the magnetoresistance effect and the tunneling effect. The magnetization direction of the free layer changes with the external magnetic field. When the external magnetic field changes, the tunneling effect will change accordingly, which will change the magnitude of the resistance state. The output of TMR is related to the change in the resistance value, that is, related to the external magnetic field strength. However, when non-invasive MEH is working, the induced current in the energy harvesting coil and the current in the AC outgoing line will generate a new magnetic field, which will affect the surrounding spatial magnetic field, resulting in a change in the magnetic field strength in the near-field space, thereby affecting the output of TMR and the monitoring of the cable current.

[0006] In actual work, since the sensitive direction of the TMR is consistent with the magnetic flux convergence direction of the energy harvesting device, when a shielding device is used to weaken the interference magnetic field around the TMR, it will inevitably affect the energy harvesting effect of the energy harvesting device. Currently, in order to avoid the problem of affecting the energy harvesting effect, the main method adopted is a compensation algorithm based on data fitting. When the relative positions of the fixed energy harvesting device and the TMR sensor are kept unchanged, data fitting is used to form an inverse function for inferring the TMR output. However, the above method does not consider that the TMR sensor will have different working states when the current excitation changes, and the accuracy of the formed inverse function for inferring the TMR output is not high, resulting in low reliability for cable current monitoring. Summary of the Invention

[0007] To solve the deficiencies existing in the prior art, the present invention provides a magnetic field energy harvesting self-powered electromagnetic sensor and its interference suppression method. Specifically, by designing a magnetic field energy harvesting self-powered TMR sensor and establishing the spatial layout and connection relationships among various parts of the device and the circuit, the interference of magnetic field energy harvesting on magnetic sensing is reduced; by adjusting the magnitude of the cable current, the magnetic field energy harvesting self-powered TMR sensor is made to be in three working states, and the upper and lower limits of the current excitation when the sensor is in the three working states are obtained; experimental data are obtained by evenly distributing selected points within each current range, and three correction algorithms are obtained based on data fitting; by judging the working states of two indication pins output by the operation state monitoring unit, the inverse function for inferring the TMR output is corrected and fitted in segments, and an accurate cable current value is obtained based on the TMR output voltage value.

[0008] The above technical objectives of the present invention are achieved through the following technical solutions:

[0009] The present invention, in a first aspect, proposes a magnetic field energy harvesting self-powered electromagnetic sensor, which includes a magnetic field energy harvesting device, a rectifying circuit, a discharging and protecting circuit, a micro energy management circuit, a TMR sensing circuit, and a control circuit;

[0010] The magnetic field energy harvesting device includes an H-shaped magnetic core and an energy harvesting coil. The energy harvesting coil is wound around the H-shaped magnetic core, and the magnetic core with the energy harvesting coil wound around it is placed closely above the single-core cable; the two AC output lines connecting the coil are placed closely beside the magnetic core parallel to the single-core cable;

[0011] The rectifying circuit is connected to the rear end of the magnetic field energy harvesting device, and the internal AC wiring of the rectifying circuit is perpendicular to the single-core cable;

[0012] The discharging and protecting circuit is connected to the rear end of the rectifying circuit through two DC output lines;

[0013] The TMR sensing circuit includes a TMR chip. The TMR sensing circuit is placed parallel and closely above a single-core cable, and the magnetic field direction generated by the single-core cable is kept parallel to the sensitive axis direction of the TMR chip. The TMR chip is closely attached to the edge of the energy-taking magnetic core and the AC outgoing line.

[0014] The micro energy management circuit includes a state monitoring unit. The micro energy management circuit is connected to the backend of the discharge circuit, and the front ends of the TMR sensing circuit and the control circuit. The rectifier circuit, the discharge circuit and the micro energy management circuit are integrated and placed parallel to the TMR sensing circuit. The AC wiring in the rectifier circuit is perpendicular to the magnetic sensitive direction of the TMR sensing circuit.

[0015] The control circuit is connected to the state monitoring unit in the micro energy management circuit and placed parallel to the micro energy management circuit.

[0016] A second aspect of the present invention mentions an interference suppression method for a magnetic field energy-taking self-powered electromagnetic sensor, which is used to operate the above-mentioned magnetic field energy-taking self-powered electromagnetic sensor, and includes the following steps:

[0017] Step 1: By adjusting the cable current, the magnetic field energy-taking self-powered electromagnetic sensor is respectively in an unsaturated state, a lightly saturated state and a heavily saturated state, and the upper and lower limits of the current excitation and the output values of the TMR without energy-taking interference and the output values of the TMR affected by energy-taking interference in the three working states of the sensor are obtained.

[0018] Step 2: According to the upper and lower limits of the current excitation in the unsaturated state, the lightly saturated state and the heavily saturated state, in the output values of the TMR without energy-taking interference and the output values of the TMR affected by energy-taking interference in each current range, points are selected evenly to obtain experimental data, and combined with the cable current, the output functions of the TMR without energy-taking interference and the output functions of the TMR affected by energy-taking interference in the three working states are obtained.

[0019] Step 3: Based on the output functions of the TMR without energy-taking interference in the unsaturated state, the lightly saturated state and the heavily saturated state, the output functions of the TMR affected by energy-taking interference in the unsaturated state, the lightly saturated state and the heavily saturated state are respectively fitted to obtain the correction algorithms corresponding to the three working states.

[0020] Step 4: According to the operation state monitoring unit to judge the working state, the output functions of the TMR affected by energy-taking interference in the unsaturated state, the lightly saturated state and the heavily saturated state are segmented and fitted according to the corresponding correction algorithms, and the corrected cable current values in the three working states obtained are combined to obtain the cable current value after interference suppression.

[0021] Preferably, in step 1, while the energy collected by the magnetic field energy extraction device powers the load, it also charges the energy storage capacitor. When the energy storage capacitor is not fully charged, it is in an unsaturated state;

[0022] When the energy storage capacitor is fully charged and continuously powers the load, but the voltage of the discharge protection circuit does not exceed the discharge voltage value, it is in a lightly saturated state;

[0023] When the voltage of the discharge protection circuit exceeds the discharge voltage value and the discharge is started, it is in a heavily saturated state.

[0024] Preferably, by adjusting the cable current, the magnetic field energy extraction self-powered electromagnetic sensor operates in an unsaturated state, and the upper and lower limits of the current excitation when the sensor operates in the unsaturated state are obtained;

[0025] Adjust the cable current so that the magnetic field energy extraction self-powered electromagnetic sensor operates in a lightly saturated state, and obtain the upper and lower limits of the current excitation when the sensor operates in the lightly saturated state;

[0026] Adjust the cable current so that the magnetic field energy extraction self-powered electromagnetic sensor operates in a heavily saturated state, and obtain the upper and lower limits of the current excitation when the sensor operates in the heavily saturated state.

[0027] Preferably, in step 2, according to the upper and lower limits of the current excitation when the sensor operates in the unsaturated state, experimental data of no energy extraction interference and energy extraction interference are obtained within this current range. The relationship curves between the cable current and the TMR output with energy extraction interference and the relationship curves between the cable current and the TMR output without energy extraction interference in the unsaturated state are plotted, and the TMR output function without energy extraction interference and the TMR output function with energy extraction interference in the unsaturated state are obtained.

[0028] Preferably, in step 2, according to the upper and lower limits of the current excitation when the sensor operates in the lightly saturated state, experimental data of no energy extraction interference and energy extraction interference are obtained within this current range. The relationship curves between the cable current and the TMR output with energy extraction interference and the relationship curves between the cable current and the TMR output without energy extraction interference in the lightly saturated state are plotted, and the TMR output function without energy extraction interference and the TMR output function with energy extraction interference in the lightly saturated state are obtained.

[0029] Preferably, in step 2, according to the upper and lower limits of the current excitation of the sensor in the heavy saturation state, experimental data of the TMR output without and with energy extraction interference in this current range are obtained, and the relationship curves between the cable current and the TMR output with energy extraction interference and between the cable current and the TMR output without energy extraction interference in the heavy saturation state are plotted, and the TMR output function without energy extraction interference and the TMR output function with energy extraction interference in the heavy saturation state are obtained.

[0030] Preferably, in step 3, based on the TMR output function without energy extraction interference in the unsaturated state, the TMR output function with energy extraction interference in the unsaturated state is curve-fitted to obtain the correction algorithm A;

[0031] Based on the TMR output function without energy extraction interference in the light saturation state, the TMR output function with energy extraction interference in the light saturation state is curve-fitted to obtain the correction algorithm B;

[0032] Based on the TMR output function without energy extraction interference in the heavy saturation state, the TMR output function with energy extraction interference in the heavy saturation state is curve-fitted to obtain the correction algorithm C.

[0033] Preferably, in step 4, the two operational comparators of the operating state monitoring unit compare the positive input voltage with the negative input voltage to monitor three working states, specifically including:

[0034] When the positive input voltage of comparator 1 < the negative input voltage and at the same time the positive input voltage of comparator 2 < the negative input voltage, the micro energy management circuit is in the unsaturated state;

[0035] When the positive input voltage of comparator 1 ≥ the negative input voltage and at the same time the positive input voltage of comparator 2 < the negative input voltage, the micro energy management circuit is in the light saturation state;

[0036] When the positive input voltage of comparator 1 ≥ the negative input voltage and at the same time the positive input voltage of comparator 2 ≥ the negative input voltage, the micro energy management circuit is in the heavy saturation state.

[0037] Preferably, by judging the positive input voltage and the negative input voltage of the two operational comparators of the operating state monitoring unit, the circuit state in three working states is monitored, and the specific process includes:

[0038] When the positive input voltage of comparator 1 < the negative input voltage and at the same time the positive input voltage of comparator 2 < the negative input voltage, the energy collected by the energy harvesting device from the magnetic field powers the load and charges the energy storage capacitor;

[0039] When the positive input voltage of the operational comparator 1 ≥ the negative input voltage, and at the same time the positive input voltage of the operational comparator 2 < the negative input voltage, the energy storage capacitor stops charging, and the collected energy continuously powers the load;

[0040] When the positive input voltage of the operational comparator 1 ≥ the negative input voltage, and at the same time the positive input voltage of the operational comparator 2 ≥ the negative input voltage, the zener diode D0 breaks down reversely, and the discharge protection circuit starts to discharge.

[0041] Preferably, the process of segmentally fitting the TMR output backstepping function according to the corresponding correction algorithm includes:

[0042] When the positive input voltage U of the operational comparator 1 of the operation status monitoring unit 正1 < the negative input voltage U of the operational comparator 1 负1 At this time, the TMR output backstepping function is fitted according to the correction algorithm A, and the TMR output value is substituted into the correction algorithm A to obtain the corrected cable current value under the current working state;

[0043] When the positive input voltage U of the operational comparator 1 of the operation status monitoring unit 正1 ≥ the negative input voltage U of the operational comparator 1 负1 , and the positive input voltage U of the operational comparator 2 正2 < the negative input voltage U of the operational comparator 2 负2 At this time, the TMR output backstepping function is fitted according to the correction algorithm B, and the TMR output value is substituted into the correction algorithm B to obtain the corrected cable current value under the current working state;

[0044] When the positive input voltage U of the operational comparator 2 of the operation status monitoring unit 正2 ≥ the negative input voltage U of the operational comparator 2 负2 At this time, the TMR output backstepping function is fitted according to the correction algorithm C, and the TMR output value is substituted into the correction algorithm C to obtain the corrected cable current value under the current working state.

[0045] The beneficial effects of the present invention are as follows. Compared with the prior art, the present invention proposes a magnetic field energy harvesting self-powered electromagnetic sensor and its interference suppression method. Specifically, a magnetic field energy harvesting self-powered TMR sensor is designed, and the spatial layout and connection relationship between various devices and circuits are established to reduce the interference of magnetic field energy harvesting on magnetic sensing. At the same time, considering the three working states of the TMR sensor, a three-segment correction algorithm is obtained based on data fitting. By judging the working state of the indication pin output by the operation state monitoring unit, the inverse function of the TMR output is segmented and corrected and fitted, and the accurate cable current value is obtained according to the TMR output voltage value, further improving the sensing accuracy. This magnetic field energy harvesting self-powered electromagnetic sensor and its interference suppression method can not only realize the self-power supply of the TMR sensor based on magnetic field energy harvesting, but also effectively solve the problem of insufficient sensing accuracy caused by the non-linear interference of the magnetic field energy harvesting device on magnetic sensing in different working states, improve the accuracy of the TMR output in the magnetic field energy harvesting self-powered electromagnetic sensor, and further improve the accuracy of cable current monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0047] Figure 1 It is the structural composition of a magnetic field energy harvesting and magnetic sensing integrated TMR sensor designed in the embodiment of the present invention;

[0048] Figure 2 It is the spatial layout and connection relationship between various devices and circuits of the TMR sensor designed in the embodiment of the present invention;

[0049] Figure 3 It is a schematic circuit diagram of the circuit models of the magnetic field energy harvesting device, rectifier circuit, discharge circuit and micro energy management circuit in the embodiment of the present invention;

[0050] Figure 4 It is the circuit diagram of the operation state monitoring unit of the TMR sensor designed in the embodiment of the present invention;

[0051] Figure 5 It is a diagram of the H-shaped magnetic core energy harvesting device with a magnetic core size of 5 cm × 5 cm × 8 cm in the embodiment of the present invention;

[0052] Figure 6 It is the segmented fitting result of the TMR output in the working state I of the energy management circuit considering the influence of the H-shaped magnetic core energy harvesting device with a magnetic core size of 5 cm × 5 cm × 8 cm in the embodiment of the present invention;

[0053] Figure 7 It is the piecewise fitting result of the TMR output in the second working state of the energy management circuit considering the influence of the H-shaped core energy extraction device with a core size of 5 cm × 5 cm × 8 cm in the embodiment of the present invention;

[0054] Figure 8 It is the piecewise fitting result of the TMR output in the third working state of the energy management circuit considering the influence of the H-shaped core energy extraction device with a core size of 5 cm × 5 cm × 8 cm in the embodiment of the present invention;

[0055] Figure 9 It is the algorithm flowchart of the piecewise fitting of the TMR output inverse function in the embodiment of the present invention;

[0056] Figure 10 It is the three-section function curve of the cable current and the TMR output in the embodiment of the present invention. Specific Embodiments

[0057] In order to make the objectives, technical solutions and advantages of the present invention clearer and more definite, the present invention will be further described in detail below with reference to the accompanying drawings. The specific embodiments described herein are only used to explain the present invention, but are not limited to the present invention.

[0058] Embodiment 1 of the present invention designs a magnetic field energy extraction self-powered TMR sensor, and establishes the spatial layout and connection relationship between various devices and circuits. The magnetic field energy extraction self-powered TMR sensor includes a magnetic field energy extraction device, a rectification circuit, a discharge protection circuit, a micro energy management circuit, a TMR sensing circuit, and a control circuit, as shown in the appendix Figure 1 as shown.

[0059] The magnetic field energy extraction device is composed of an H-shaped core and an energy extraction coil. The energy extraction coil is wound around the H-shaped core, and the core with the energy extraction coil is placed closely above the single-core cable; the two AC outgoing lines connecting the coil are placed closely beside the core parallel to the single-core cable.

[0060] The rectification circuit is composed of a compensation capacitor and a rectifier bridge, and is connected to the rear end of the magnetic field energy extraction device through two AC outgoing lines. The capacitance value of the compensation capacitor is determined by the self-inductance of the magnetic field energy extraction device and the power frequency.

[0061] The discharge protection circuit is composed of a voltage stabilizing diode and a monitoring resistor, and the discharge protection circuit is connected to the rear end of the rectification circuit through two DC outgoing lines.

[0062] The TMR sensing circuit mainly detects the changes in the surrounding magnetic field through a TMR chip. The TMR sensing circuit is placed parallel and closely above the single-core cable, and the magnetic field direction generated by the single-core cable is kept parallel to the sensitive axis direction of the TMR chip to obtain the maximum output voltage. At the same time, in order to maximize the consideration of the influence of the energy-taking device on current measurement, the TMR chip is closely attached to the edge of the energy-taking magnetic core and the AC outgoing line, and the power frequency magnetic field direction of the internal AC line in the rectifying circuit is perpendicular to the magnetic sensitive direction of the TMR sensing, so as to reduce the interference to the TMR sensing circuit.

[0063] The micro energy management circuit includes a filter capacitor, two-stage DC-DC modules, an energy storage capacitor and a status monitoring unit. The energy storage capacitor is connected in the middle of the two-stage DC-DC modules. The output of the second-stage DC-DC module is a regulated DC voltage. The status monitoring unit realizes the operation status monitoring of the magnetic field energy-taking self-powered electromagnetic sensor by comparing the regulated DC voltage, the voltage across the energy storage capacitor, and the voltage across the monitoring resistor in the discharging circuit. The micro energy management circuit is connected to the rear end of the discharging circuit, and is connected to the front end of the TMR sensing circuit and the control circuit to supply power to the TMR power circuit and the control circuit. The rectifying circuit, the discharging circuit and the micro energy management circuit are integrated and placed parallel to the TMR sensing circuit, so that the AC wiring in the rectifying circuit is perpendicular to the magnetic sensitive direction of the TMR sensing, reducing the interference to the TMR sensor.

[0064] The operation status monitoring unit is composed of a sampling resistor, a voltage dividing resistor, a comparator, an indicating pin and a protection element, etc. It realizes the operation status monitoring of the magnetic field energy-taking self-powered electromagnetic sensor by comparing the regulated DC voltage, the voltage across the energy storage capacitor, and the voltage across the monitoring resistor in the discharging circuit. The circuit diagram of the operation status monitoring unit is as shown in the appendix Figure 4 shown.

[0065] The control circuit is composed of a central processing unit, a memory, an input / output interface, an analog-to-digital converter, etc. The output indicating pin of the operation status monitoring unit is connected to the control circuit.

[0066] The spatial layout and connection relationship between the various parts and circuits of the magnetic field energy-taking and magnetic sensing integrated TMR sensor are as shown in the appendix Figure 2As shown in the figure. The energy-taking magnetic core is placed closely and parallelly directly above the single-core cable, and the two AC outgoing lines connecting the coil are placed closely parallel to the single-core cable beside the magnetic core; the rectifying circuit is connected to the rear end of the magnetic field energy-taking device, and the AC line inside the rectifying circuit is perpendicular to the single-core cable; the discharge protection circuit is connected to the rear end of the rectifying circuit through two DC outgoing lines; the micro energy management circuit is connected to the rear end of the discharge circuit and is connected to the front ends of the TMR sensing circuit and the control circuit to supply power to the TMR power supply circuit and the control circuit; the TMR sensing circuit is placed closely and parallelly directly above the single-core cable, so that the magnetic field direction generated by the single-core cable is parallel to the sensitive axis direction of the TMR chip, and the TMR chip is closely attached to the edges of the energy-taking magnetic core and the AC outgoing lines, and the power frequency magnetic field direction of the AC line inside the rectifying circuit is perpendicular to the magnetic sensitive direction of the TMR sensing to reduce the interference to the TMR sensing circuit; the rectifying circuit, the discharge circuit and the micro energy management circuit are integrated and placed parallel to the TMR sensing circuit; the control circuit is connected to the output indication pin of the operation state monitoring unit and is placed parallel to the micro energy management circuit.

[0067] The circuit model schematic diagrams of the magnetic field energy-taking device, the rectifying circuit, the discharge circuit and the micro energy management circuit are as shown in the appendix Figure 3 As shown in the figure. The single-core cable conducts a power frequency alternating current with a magnitude of I, and the number of turns of the busbar is 1; the number of turns of the energy-taking coil is N, the self-inductance is L, the internal resistance is R, and the mutual inductance between the single-core cable and the energy-taking coil is M; the compensation capacitor is C0; the rectifying bridge is composed of four rectifying diodes D1, D2, D3, and D4; the voltage stabilizing diode is D0, the monitoring resistor is R0, and the voltage across the monitoring resistor is U R ; the filtering capacitor is C1, and the load size is R L , and the voltage across the load is U O ; the energy storage capacitor is C, and the voltage across the energy storage capacitor is U C .

[0068] Embodiment 2 of the present invention provides a method for suppressing interference of a magnetic field energy-taking self-powered electromagnetic sensor, including the following steps:

[0069] Step 1: By adjusting the cable current, the magnetic field energy-taking self-powered electromagnetic sensor is respectively in an unsaturated state, a lightly saturated state and a heavily saturated state, and the upper and lower limits of the current excitation and the output values of the TMR without energy-taking interference and the output values of the TMR affected by energy-taking interference of the sensor in the three working states are obtained;

[0070] The micro energy management circuit has three operating states: unsaturated state, that is, the energy collected by the magnetic field energy harvesting device powers the load and charges the energy storage capacitor at the same time, but the energy storage capacitor is not fully charged; lightly saturated state, that is, the energy storage capacitor is fully charged and continuously powers the load, but the voltage of the discharge protection circuit does not exceed the discharge voltage value; heavily saturated state, that is, the voltage of the discharge protection circuit exceeds the discharge voltage value and the discharge is started.

[0071] The circuit diagram of the operating state monitoring unit is as shown in the appendix Figure 4 shown. U C is the voltage of the energy storage capacitor, U C-Ref is the rated voltage of the set energy storage capacitor, U O is the regulated output voltage of the micro energy management circuit, and satisfies U C-Ref = k1U O , where k1 is a reference coefficient; U R is the voltage of the monitoring resistor, U R-Ref is the set discharge protection voltage, and satisfies U R-Ref = k2U O , where k2 is a reference coefficient.

[0072] The positive input voltage U 正1 of operational comparator 1 is as follows:

[0073] U 正1 = U C R2 / (R1 + R2) (1)

[0074] where, U C is the voltage of the energy storage capacitor, and R1 and R2 are the voltage dividing resistors at the positive input terminal of operational comparator 1.

[0075] The negative input voltage U 负1 of operational comparator 1 is as follows:

[0076] U 负1 = U O R4 / (R3 + R4) (2)

[0077] where, U O is the regulated output voltage of the micro energy management circuit, and R3 and R4 are the voltage dividing resistors at the negative input terminal of operational comparator 1.

[0078] k1 = R4(R1 + R2) / R2(R3 + R4) (3)

[0079] where, k1 is a reference coefficient, R1 and R2 are the voltage dividing resistors at the positive input terminal of operational comparator 1, and R3 and R4 are the voltage dividing resistors at the negative input terminal of operational comparator 1.

[0080] The positive input voltage U 正2The formula is as follows:

[0081] U 正2 = U R R7 / (R6 + R7) (4)

[0082] Wherein, U R is the monitored resistor voltage, and R6 and R7 are the voltage dividing resistors at the positive input terminal of the operational comparator 2.

[0083] The negative input voltage U 负2 of the operational comparator 2 has the following formula:

[0084] U 负2 = U O R9 / (R8 + R9) (5)

[0085] Wherein, U O is the regulated output voltage of the micro energy management circuit, and R8 and R9 are the voltage dividing resistors at the negative input terminal of the operational comparator 2.

[0086] k1 = R9(R6 + R7) / R7(R8 + R9) (6)

[0087] Wherein, k2 is a reference coefficient, R6 and R7 are the voltage dividing resistors at the positive input terminal of the operational comparator 1, and R8 and R9 are the voltage dividing resistors at the negative input terminal of the operational comparator 1.

[0088] The two operational comparators compare the positive input voltage with the negative input voltage, and the operating state monitoring unit outputs 2 indication pins: (1) When the positive input voltage U 正1 of the operational comparator 1 < the negative input voltage U 负1 , and the positive input voltage U 正2 of the operational comparator 2 < the negative input voltage U 负2 , both the indication pin 1 and the indication pin 2 output low levels, and the micro energy management circuit is in an unsaturated state; (2) When the positive input voltage U 正1 ≥ the negative input voltage U 负1 of the operational comparator 1, and the positive input voltage U 正2 < the negative input voltage U 负2 of the operational comparator 2, the indication pin 1 outputs a high level and the indication pin 2 outputs a low level, and the micro energy management circuit is in a lightly saturated state; (3) When the positive input voltage U 正1 ≥ the negative input voltage U 负1 of the operational comparator 1, and the positive input voltage U 正2 ≥ the negative input voltage U 负2When the time is reached, both the indication pin 1 and the indication pin 2 output high level, and the micro energy management circuit is in the re-saturation state.

[0089] When the current is small, the energy management circuit is in the unsaturated state. While the energy harvesting device collects energy to supply power to the load, it also charges the energy storage capacitor, but the energy storage capacitor is not fully charged yet. When the current continues to increase, the energy management circuit is in the light saturation state. The energy storage capacitor is fully charged and continuously supplies power to the load, but the voltage of the discharge circuit does not exceed the discharge voltage value. When the current is too large, the energy management circuit is in the re-saturation state. The voltage of the discharge protection circuit exceeds the discharge voltage value and the discharge is started.

[0090] The positive input voltage and the negative input voltage are compared through two operational comparators. Further, two indication pins are output through the operating state monitoring unit to determine the working state of the magnetic field energy harvesting self-powered electromagnetic sensor and the correction algorithm of the TMR output inverse function. Finally, the TMR output value is substituted into the correction algorithm to obtain the cable current value at this time.

[0091] By adjusting the magnitude of the cable current, the magnetic field energy harvesting self-powered electromagnetic sensor is made to operate in the unsaturated state, and the upper and lower limits of the current excitation of the sensor operating in the unsaturated state are obtained.

[0092] Adjust the magnitude of the cable current so that the magnetic field energy harvesting self-powered electromagnetic sensor operates in the light saturation state, and obtain the upper and lower limits of the current excitation of the sensor operating in the light saturation state.

[0093] Adjust the magnitude of the cable current so that the magnetic field energy harvesting self-powered electromagnetic sensor operates in the re-saturation state, and obtain the upper and lower limits of the current excitation of the sensor operating in the re-saturation state.

[0094] Step 2: According to the upper and lower limits of the current excitation in the unsaturated state, light saturation state, and re-saturation state, in the output values of the TMR without energy harvesting interference and the output values of the TMR affected by energy harvesting interference within each current range, select points evenly distributed to obtain experimental data. Combining with the cable current, the output function of the TMR without energy harvesting interference and the output function of the TMR affected by energy harvesting interference in the three working states are obtained.

[0095] The embodiment of the present invention uses a magnetic core with a size of 5 cm × 5 cm × 8 cm, and the energy harvesting device is as Figure 5 shown. Without the influence of the magnetic core, the energy harvesting coil, and the energized AC outgoing line, that is, under the condition of no interference, adjust the cable current to change within 0 - 1000 A, record 20 groups of measurement values, and draw the function curve of the cable current and the TMR output as shown by the red curve in the following figure.

[0096] Considering the actual situation, the magnetic core, the energy-taking coil and the energized AC outgoing line coexist, that is, under the condition of the influence of the energy-taking device, the cable current is adjusted to change within 0 - 1000A.

[0097] According to the upper and lower limits of the current excitation when the sensor works in the unsaturated state, 10 points are evenly distributed within this current range to obtain experimental data, and the experimental data without energy-taking interference and with energy-taking interference in the unsaturated state are obtained. The working state I relationship curve between the cable current and the TMR output affected by energy-taking interference in the unsaturated state and the working state I relationship curve between the cable current and the TMR output not affected by energy-taking interference in the unsaturated state are plotted, and the TMR output function not affected by energy-taking interference in the unsaturated state and the TMR output function affected by energy-taking interference in the unsaturated state are obtained.

[0098] According to the upper and lower limits of the current excitation when the sensor works in the lightly saturated state, 10 points are evenly distributed within this current range to obtain experimental data, and the experimental data without energy-taking interference and with energy-taking interference in the lightly saturated state are obtained. The working state II relationship curve between the cable current and the TMR output affected by energy-taking interference in the lightly saturated state and the working state II relationship curve between the cable current and the TMR output not affected by energy-taking interference in the lightly saturated state are plotted, and the TMR output function not affected by energy-taking interference in the lightly saturated state and the TMR output function affected by energy-taking interference in the lightly saturated state are obtained.

[0099] According to the upper and lower limits of the current excitation when the sensor works in the heavily saturated state, 10 points are evenly distributed within this current range to obtain experimental data, and the experimental data without energy-taking interference and with energy-taking interference in the heavily saturated state are obtained. The working state III relationship curve between the cable current and the TMR output affected by energy-taking interference in the heavily saturated state and the working state III relationship curve between the cable current and the TMR output not affected by energy-taking interference in the heavily saturated state are plotted, and the TMR output function not affected by energy-taking interference in the heavily saturated state and the TMR output function affected by energy-taking interference in the heavily saturated state are obtained.

[0100] Step 3: Evenly distribute points within each current range to obtain experimental data, and based on data fitting, obtain the correction algorithms corresponding to different working states;

[0101] Based on the TMR output function not affected by energy-taking interference in the unsaturated state, function fitting is performed on the TMR output function affected by energy-taking interference in the unsaturated state to obtain the fitting result of the first-stage TMR output inverse function, and correction algorithm A is obtained.

[0102] The TMR output function affected by energy-taking interference in the unsaturated state is used to perform function fitting on the TMR output function affected by energy-taking interference in the lightly saturated state to obtain the fitting result of the second-stage TMR output inverse function, and correction algorithm B is obtained.

[0103] Based on the TMR output function that is not affected by energy extraction in the re - saturation state, function fitting is performed on the TMR output function affected by energy extraction in the re - saturation state to obtain the fitting result of the third - segment TMR output inverse - deduction function, and correction algorithm C is obtained.

[0104] Working state one is the unsaturated state, working state two is the lightly saturated state, and working state three is the re - saturated state.

[0105] The three - segment function curves of cable current and TMR output are plotted as follows Figure 10 Shown by the blue, yellow, and green segmented curves. The blue curve is the cable current value in working state one under the influence of the energy extraction device; the yellow curve is the cable current value in working state two under the influence of the energy extraction device; the green curve is the cable current value in working state three under the influence of the energy extraction device. Comparing the TMR output curves under the ideal non - interference condition and the actual influence of the energy extraction device, it can be seen from the following figure that after considering the interference of the energy extraction device, the output of TMR is no longer a completely linear function under non - interference conditions.

[0106] According to the three - segment function curves of cable current and TMR output drawn under the condition of the influence of the energy extraction device, the relationship between cable current and TMR output in the three working states is segmented - function - fitted through the Matlab tool to obtain the fitting result of the TMR output segmented inverse - deduction function considering the influence of the energy extraction device I = f(U), and the relationship between cable current and TMR output voltage is obtained, as shown in the appendix Figure 6 、 Figure 7 and Figure 8 shown.

[0107] When fitting the TMR output segmented curve, in working state one, when the fitting function is a fifth - degree polynomial, the accuracy is relatively high. Therefore, the first - segment inverse - deduction fitting function of the TMR output considering the influence of the energy extraction device can be obtained, that is, correction algorithm A is:

[0108] I1=-17050U 5 + 27880U 4 -15930U 3 +3826U 2 +394.1U + 12.3 (5)

[0109] In working state two, when the fitting function is a fourth - degree polynomial, the accuracy is relatively high. Therefore, the second - segment inverse - deduction fitting function of the TMR output considering the influence of the energy extraction device can be obtained, that is, correction algorithm B is:

[0110] I2 = 6573U 4 -22410U 3 +28230U 2 -14740U + 3156 (6)

[0111] In the third working state, when the fitting function is a seventh-degree polynomial, the accuracy is relatively high. Therefore, the third-segment inverse fitting function of the TMR output considering the influence of the energy-taking device can be obtained, that is, the correction algorithm C is as follows:

[0112]

[0113] Where I1, I2, and I3 respectively represent the cable current values in different working states, and U represents the output value of the TMR.

[0114] Step 4: Judge the working state according to the indication pins output by the operation state monitoring unit, segmentally fit the TMR output functions affected by energy-taking interference in the three working states according to the corresponding correction algorithms, obtain the corrected cable current values in the three working states according to the TMR output voltage value, combine the obtained corrected cable current values in the three working states, and obtain the cable current value after suppressing interference, so as to solve the problem of interference of magnetic field energy-taking on the magnetic field around the TMR.

[0115] Write software in the controller to implement segmented correction. Further, the segmented correction includes judging the states of 2 indication pins output by the operation state monitoring unit. The algorithm flowchart of the segmented fitting of the TMR output inverse function is as shown in the appendix Figure 9 as follows:

[0116] When the positive input voltage U 正1 of the arithmetic comparator 1 of the operation state monitoring unit is less than the negative input voltage U 负1 of the arithmetic comparator 1, both the indication pin 1 and the indication pin 2 output low levels, and the TMR output inverse function is fitted according to the correction algorithm A. That is, by substituting the TMR output value into the correction algorithm A, the cable current value at this time can be obtained;

[0117] When the positive input voltage U 正1 of the arithmetic comparator 1 of the operation state monitoring unit is greater than or equal to the negative input voltage U 负1 of the arithmetic comparator 1, and the positive input voltage U 正2 of the arithmetic comparator 2 of the operation state monitoring unit is less than the negative input voltage U 负2 of the arithmetic comparator 2, the indication pin 1 outputs a high level and the indication pin 2 outputs a low level. The TMR output inverse function is fitted according to the correction algorithm B. That is, by substituting the TMR output value into the correction algorithm B, the cable current value at this time can be obtained;

[0118] When the positive input voltage U 正2 of the arithmetic comparator 2 of the operation state monitoring unit is greater than or equal to the negative input voltage U 负2When this occurs, both the indication pin 1 and the indication pin 2 output high levels. The inverse function of the TMR output is fitted according to the correction algorithm C. That is, by substituting the TMR output value into the correction algorithm C, the cable current value at this time can be obtained. Therefore, the segmented correction method based on data fitting proposed by the present invention, considering the influence of the energy harvesting device, can not only achieve self-power supply of the TMR, but also solve the problem of the interference of magnetic field energy harvesting on the magnetic field around the TMR, effectively improving the accuracy of the TMR output in the magnetic field energy harvesting self-powered electromagnetic sensor, and further improving the accuracy of cable current monitoring.

[0119] The beneficial effects of the present invention are as follows: The present invention proposes a magnetic field energy harvesting self-powered electromagnetic sensor and its interference suppression method. Specifically, a magnetic field energy harvesting self-powered TMR sensor is designed, and the spatial layout and connection relationship between various parts of the device and the circuit are established to reduce the interference of magnetic field energy harvesting on magnetic sensing. At the same time, considering the three working states of the TMR sensor, three-segment correction algorithms are obtained based on data fitting. By judging the working state of the indication pins output by the operation state monitoring unit, the inverse function of the TMR output is segmented and corrected and fitted, and the accurate cable current value is obtained according to the TMR output voltage value, further improving the sensing accuracy. This magnetic field energy harvesting self-powered electromagnetic sensor and its interference suppression method can not only achieve self-power supply of the TMR sensor based on magnetic field energy harvesting, but also effectively solve the problem of insufficient sensing accuracy caused by the non-linear interference of the magnetic field energy harvesting device on magnetic sensing in different working states, improve the accuracy of the TMR output in the magnetic field energy harvesting self-powered electromagnetic sensor, and further improve the accuracy of cable current monitoring.

[0120] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A magnetic field energy-taking self-powered electromagnetic sensor, comprising a magnetic field energy-taking device, a rectifier circuit, a discharge protection circuit, a micro-energy management circuit, a TMR sensor circuit and a control circuit; characterized in that: The magnetic field energy harvesting device comprises an H-shaped magnetic core and an energy harvesting coil, wherein the energy harvesting coil is wound on the H-shaped magnetic core, and the magnetic core wound with the energy harvesting coil is placed close to the single-core cable; two AC output lines connecting the coil are placed parallel to the single-core cable and close to the magnetic core; The rectifier circuit is connected to the rear end of the magnetic field energy harvesting device, and the AC wiring inside the rectifier circuit is perpendicular to the single-core cable; The discharge protection circuit is connected to the rear end of the rectifier circuit through two DC output lines; The TMR sensing circuit includes a TMR chip. The TMR sensing circuit is placed in parallel and close to the top of the single-core cable, and the direction of the magnetic field generated by the single-core cable is kept parallel to the sensitive axis direction of the TMR chip. The TMR chip is placed close to the edge of the energy-taking magnetic core and the AC output line. The micro energy management circuit comprises a filter capacitor, a two-stage DC-DC module, an energy storage capacitor and a state monitoring unit. The energy storage capacitor is connected in the middle of the two-stage DC-DC module. The second-stage DC-DC module outputs a regulated DC voltage. The state monitoring unit realizes the operation state monitoring of the magnetic field energy self-supply electromagnetic sensor by comparing the regulated DC voltage, the voltage across the energy storage capacitor, and the voltage across the monitoring resistor in the discharge protection circuit. The micro energy management circuit is connected to the rear end of the discharge protection circuit and to the front end of the TMR sensor circuit and the control circuit. The rectifier circuit, the discharge protection circuit and the micro energy management circuit are integrated together and placed parallel to the TMR sensor circuit, and the AC wiring in the rectifier circuit is perpendicular to the magnetic sensitivity direction of the TMR sensor circuit. The micro energy management circuit has three working states: unsaturated state, light saturated state and heavy saturated state. The control circuit is connected to the state monitoring unit in the micro energy management circuit and is placed in parallel with the micro energy management circuit.

2. A method for suppressing interference of a magnetic field self-powered electromagnetic sensor, used for operating a magnetic field self-powered electromagnetic sensor according to claim 1, characterized in that: The following steps are involved: Step 1: By adjusting the cable current, the magnetic field energy self-powered electromagnetic sensor is in an unsaturated state, a lightly saturated state, and a heavily saturated state, respectively, and the current excitation upper and lower limits of the sensor in the three working states and the output value of the TMR without energy extraction interference and the TMR output value with energy extraction interference are obtained; Step 2: According to the upper and lower limits of current excitation in the unsaturated state, lightly saturated state and heavily saturated state, the output values ​​of the TMR without energy extraction interference and the TMR output values ​​with energy extraction interference in each current range are evenly distributed to obtain experimental data. Combined with the cable current, the output functions of the TMR without energy extraction interference and the TMR output functions with energy extraction interference under the three working conditions are obtained; Step 3: Based on the output functions of the TMR without energy extraction interference in the unsaturated state, the lightly saturated state and the heavily saturated state, the output functions of the TMR with energy extraction interference in the unsaturated state, the lightly saturated state and the heavily saturated state are fitted respectively to obtain the correction algorithms corresponding to the three working states; Step 4: Determine the working state according to the operation state monitoring unit, and fit the TMR output function affected by energy extraction interference in the unsaturated state, lightly saturated state, and heavily saturated state in sections according to the corresponding correction algorithm. Combine the corrected cable current values ​​under the three working states to obtain the cable current value after interference suppression.

3. The interference suppression method of a magnetic field energy self-powered electromagnetic sensor according to claim 2, characterized in that: include: In step 1, the energy collected by the magnetic field energy harvesting device is used to supply power to the load and to charge the energy storage capacitor at the same time, but when the energy storage capacitor is not fully charged, it is in an unsaturated state; The energy storage capacitor is fully charged and continuously supplies power to the load, but the voltage of the discharge protection circuit does not exceed the discharge voltage value, which is a light saturation state; When the voltage of the discharge protection circuit exceeds the discharge voltage value and the discharge is started, it is in a heavy saturation state.

4. The interference suppression method of a magnetic field energy self-powered electromagnetic sensor according to claim 3, characterized in that: By adjusting the cable current so that the magnetic field energy self-powered electromagnetic sensor works in an unsaturated state, the upper and lower limits of the current excitation when the sensor works in the unsaturated state are obtained; Adjust the cable current so that the magnetic field energy self-powered electromagnetic sensor works in a light saturation state, and obtain the current excitation upper limit and lower limit of the sensor working in the light saturation state; The cable current is adjusted so that the magnetic field energy self-powered electromagnetic sensor operates in a heavy saturation state, and the current excitation upper limit and lower limit when the sensor operates in the heavy saturation state are obtained.

5. The interference suppression method of a magnetic field energy self-powered electromagnetic sensor according to claim 2, characterized in that: In step 2, according to the upper and lower limits of current excitation when the sensor operates in an unsaturated state, experimental data with and without energy extraction interference in the unsaturated state are obtained within the current range, and a relationship curve between the cable current in the unsaturated state and the TMR output with energy extraction interference and a relationship curve between the cable current in the unsaturated state and the TMR output without energy extraction interference are plotted to obtain a TMR output function without energy extraction interference in the unsaturated state and a TMR output function with energy extraction interference in the unsaturated state.

6. The interference suppression method of a magnetic field energy self-powered electromagnetic sensor according to claim 2, characterized in that: In step 2, according to the upper and lower limits of current excitation when the sensor operates in a light saturation state, experimental data with and without energy extraction interference in the light saturation state are obtained within the current range, and a relationship curve between the cable current in the light saturation state and the TMR output with energy extraction interference and a relationship curve between the cable current in the light saturation state and the TMR output without energy extraction interference are plotted to obtain a TMR output function without energy extraction interference in the light saturation state and a TMR output function with energy extraction interference in the light saturation state.

7. The interference suppression method of a magnetic field energy self-powered electromagnetic sensor according to claim 2, characterized in that: In step 2, according to the upper and lower limits of the current excitation when the sensor works in the heavy saturation state, experimental data without energy extraction interference and with energy extraction interference in the heavy saturation state are obtained within the current range, and the relationship curve between the cable current in the heavy saturation state and the TMR output with energy extraction interference and the relationship curve between the cable current in the heavy saturation state and the TMR output without energy extraction interference are plotted to obtain the TMR output function without energy extraction interference in the heavy saturation state and the TMR output function with energy extraction interference in the heavy saturation state.

8. The interference suppression method of a magnetic field energy self-powered electromagnetic sensor according to claim 2, characterized in that: In step 3, based on the TMR output function that is not disturbed by energy extraction in an unsaturated state, a function fitting is performed on the TMR output function that is disturbed by energy extraction in an unsaturated state to obtain a correction algorithm A; Based on the TMR output function in the light saturation state without interference from energy extraction, the TMR output function in the light saturation state with interference from energy extraction is fitted to obtain a correction algorithm B; Based on the TMR output function in the heavily saturated state without interference from energy extraction, a function fitting is performed on the TMR output function in the heavily saturated state with interference from energy extraction to obtain a correction algorithm C.

9. The interference suppression method of a magnetic field energy self-powered electromagnetic sensor according to claim 2, characterized in that: In step 4, the operation status monitoring unit is composed of a sampling resistor, a voltage dividing resistor, a comparator, an indication pin and a protection element. U C is the voltage of the energy storage capacitor, which is connected to the positive input terminal of the operational comparator I through the voltage divider resistors R1 and R2. U O The regulated output voltage of the micro energy management circuit is connected to the negative input terminal of the operational comparator I through the voltage divider resistors R3 and R4. U R To monitor the resistor voltage, the positive input terminal of the operational comparator II is connected through the voltage divider resistors R6 and R7. U O The regulated output voltage of the micro energy management circuit is connected to the negative input terminal of the operational comparator II through the voltage divider resistors R8 and R9. The two operational comparators of the operation status monitoring unit compare the positive input voltage with the negative input voltage to monitor three working states, including: When the positive input voltage of the operational comparator I is less than the negative input voltage, and the positive input voltage of the operational comparator II is less than the negative input voltage, the micro energy management circuit is in an unsaturated state; When the positive input voltage of the operational comparator I is greater than or equal to the negative input voltage, and the positive input voltage of the operational comparator II is less than the negative input voltage, the micro energy management circuit is in a light saturation state; When the positive input voltage of the operational comparator I is ≥ the negative input voltage, and the positive input voltage of the operational comparator II is ≥ the negative input voltage, the micro energy management circuit is in a heavy saturation state.

10. The interference suppression method of a magnetic field energy self-powered electromagnetic sensor according to claim 9, characterized in that: include: By judging the positive input voltage and negative input voltage of the two operational comparators of the operation status monitoring unit, the circuit status under three working states is monitored. The specific process includes: When the positive input voltage of the operational comparator I is less than the negative input voltage, and the positive input voltage of the operational comparator II is less than the negative input voltage, the energy harvesting device collects energy from the magnetic field to power the load and charge the energy storage capacitor; When the positive input voltage of the operational comparator I is greater than or equal to the negative input voltage, and the positive input voltage of the operational comparator II is less than the negative input voltage, the energy storage capacitor stops charging, and the collected energy continues to supply power to the load; When the positive input voltage of the operational comparator I is greater than or equal to the negative input voltage and the positive input voltage of the operational comparator II is greater than or equal to the negative input voltage, the voltage stabilizing diode D0 breaks down in reverse and the discharge protection circuit starts to discharge.

11. The interference suppression method of a magnetic field energy self-powered electromagnetic sensor according to claim 9, characterized in that: The process of segmentally fitting the TMR output function disturbed by energy extraction according to the corresponding correction algorithm includes: When the positive input voltage of the operational comparator I of the operating status monitoring unit is U 正1 <Negative input voltage of the operational comparator I U 负1 When , substitute the TMR output value into the correction algorithm A to obtain the corrected cable current value in the current working state; When the positive input voltage of the operating status monitoring unit comparator I U 正1 ≥Negative input voltage of operational comparator I U 负1 , the positive input voltage of the operational comparator II U 正2 <Negative input voltage of the operational comparator II U 负2 When , substitute the TMR output value into the correction algorithm B to obtain the corrected cable current value in the current working state; When the positive input voltage of the operating status monitoring unit comparator II is U 正2 ≥Negative input voltage of operational comparator II U 负2 When the TMR output value is substituted into the correction algorithm C, the corrected cable current value in the current working state is obtained.

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