Device and method for measuring voltage of DC distribution network based on TMR micro-current measurement principle

Abstract

The present invention discloses a device and method for measuring the voltage of a DC distribution network based on the principle of TMR microcurrent measurement, and belongs to the field of sensor technology application. The device of the present invention includes: a high-resistance resistor, a DC bus voltage connected to the DC distribution network to be measured, the DC bus voltage is converted into a DC small current signal, and the DC small current signal is transmitted to a current transformer; a current transformer receives a DC small current signal, and converts the DC small current signal into an AC microcurrent signal at a preset ratio and transmits it to a diode rectifier bridge; a diode rectifier bridge receives an AC microcurrent signal, and converts the AC microcurrent signal into a DC microcurrent signal, and transmits it to a TMR microcurrent measurement bridge; a microcurrent measurement bridge receives a DC microcurrent signal, and outputs the magnetic field generated by the DC microcurrent signal in the form of a differential voltage, and measures the differential voltage. The present invention makes up for the shortcomings of accuracy and stability in measuring voltage based on a voltage divider structure.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology applications, and more particularly, to a device and method for measuring the voltage of a DC distribution network based on the TMR microcurrent measurement principle. Background Art

[0002] my country has been conducting a number of research projects and conducting demonstration projects for DC distribution networks, including the Haining Jianshan AC / DC Hybrid Distribution Network Project (±10kV) in Zhejiang Province, the Hangzhou Jiangdong New City Flexible DC Distribution Network Project (±10kV), and the Shangyu AC / DC Hybrid Microgrid Demonstration Project (560V). However, in-depth research into energy metering methods and instrumentation suitable for DC distribution networks has been lacking. Accurately measuring the voltage and current of the DC busbar is crucial for measuring energy in DC distribution networks.

[0003] Currently, for DC power in power systems, the most commonly used voltage sensors are primarily resistive or RC DC voltage dividers. Commonly used current sensors include zero-flux current transformers, active photoelectric current transformers, all-fiber current sensors, and Hall current sensors. In recent decades, with the in-depth study of the magnetoresistance effect, anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), and tunnel magnetoresistance (TMR) technologies have gradually matured and been applied to current measurement. TMR elements, with their high sensitivity, wide linear range, low power consumption, and low temperature drift, have emerged as a prominent technology in current measurement. However, to be suitable for voltage measurement in DC distribution networks, traditional voltage sensors based on the voltage divider principle lack accuracy and stability, and the high-performance TMR elements have yet to be used in voltage measurement. Summary of the Invention

[0004] In response to the above problems, the present invention proposes a device for measuring the voltage of a DC distribution network based on the principle of TMR measurement of microcurrent, comprising:

[0005] A high-resistance resistor is connected to the DC bus voltage of the DC distribution network to be measured, the DC bus voltage is converted into a DC low current signal, and the DC low current signal is transmitted to the current transformer;

[0006] The current transformer receives a DC low current signal and converts the DC low current signal into an AC micro current signal at a preset ratio and transmits it to the diode rectifier bridge;

[0007] The diode rectifier bridge receives the AC microcurrent signal, converts the AC microcurrent signal into a DC microcurrent signal, and transmits it to the TMR microcurrent measurement bridge;

[0008] The micro-current measurement bridge receives the DC micro-current signal and outputs the magnetic field generated by the DC micro-current signal in the form of a differential voltage. The differential voltage is measured and the output differential voltage is the DC distribution network voltage.

[0009] The micro-current measurement bridge includes: a current-carrying U-shaped conductor, a first MTJ element, a second MTJ element, a third MTJ element, a fourth MTJ element and a reference power supply;

[0010] One end of the U-shaped conductor is an output resistor, which receives a DC micro-current signal. The DC micro-current signal flows under the third MTJ element, the second MTJ element, the first MTJ element, and the fourth MTJ element, and outputs the magnetic field generated by the DC micro-current signal in the form of a differential voltage. The other end of the U-shaped conductor is used as a secondary measurement end of a micro-current measurement bridge to measure the differential voltage.

[0011] One end of the first MTJ element and one end of the second MTJ element are commonly connected to the positive input end of the reference voltage source, and one end of the third MTJ element and one end of the fourth MTJ element are commonly connected to the negative input end of the reference voltage source;

[0012] The other end of the first MTJ element and the other end of the third MTJ element are commonly connected to the positive polarity end of the secondary measurement end, and the other end of the second MTJ element and the other end of the fourth MTJ element are commonly connected to the negative polarity end of the secondary measurement end.

[0013] Optionally, the high-resistance resistor is the primary measurement end of the device, and the current transformer is used to electrically isolate the primary measurement end.

[0014] Optionally, the high-resistance resistor is composed of multiple resistors with the same resistance connected in series, one end of which is connected to a DC bus voltage measurement point of the DC distribution network, and the other end of which is connected to a reference point via a current-carrying conductor.

[0015] Optionally, the current transformer comprises: a current-carrying conductor, a first secondary winding, and a second secondary winding;

[0016] The current-carrying conductor serves as the primary winding of the current transformer, and the primary winding comprises: a first iron core and a second iron core;

[0017] One end of the first secondary winding is connected in series with the second secondary winding in reverse direction, and the other end of the first secondary winding is connected to the diode rectifier bridge.

[0018] Optionally, a diode rectifier bridge includes: a first diode, a second diode, a third diode and a fourth diode;

[0019] The cathode of the first diode and the cathode of the second diode are commonly connected to the secondary measurement end of the current-carrying U-shaped conductor, and the anode of the third diode and the anode of the fourth diode are commonly connected to one end of the output resistor of the current-carrying U-shaped conductor.

[0020] The present invention also proposes a method for measuring the voltage of a DC distribution network based on the principle of TMR measurement of microcurrent, comprising:

[0021] A high-resistance resistor is connected to the DC bus voltage of the DC distribution network to be measured, converts the DC bus voltage into a DC low current signal, and transmits the DC low current signal to a current transformer;

[0022] The current transformer receives a DC low current signal and converts the DC low current signal into an AC micro current signal at a preset ratio and transmits it to the diode rectifier bridge;

[0023] The diode rectifier bridge receives the AC microcurrent signal, converts the AC microcurrent signal into a DC microcurrent signal and transmits it to the TMR microcurrent measurement bridge;

[0024] The microcurrent measurement bridge receives the DC microcurrent signal and outputs the magnetic field generated by the DC microcurrent signal in the form of a differential voltage. The differential voltage is measured, and the output differential voltage is the DC distribution network voltage.

[0025] The present invention converts voltage measurement into current measurement, making up for the shortcomings of accuracy and stability in voltage measurement based on a voltage divider structure, and broadening the application scope of DC distribution network voltage measurement beyond magnetic field, current and displacement. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a structural diagram of a device for measuring DC distribution network voltage based on the TMR microcurrent measurement principle of the present invention;

[0027] Figure 2 This is a structural logic diagram of a device for measuring DC distribution network voltage based on the TMR microcurrent measurement principle of the present invention;

[0028] Figure 3 This is a diagram of the structure of a diode rectifier bridge of a device for measuring DC distribution network voltage based on the TMR microcurrent measurement principle of the present invention;

[0029] Figure 4 This is a flow chart of a method for measuring DC distribution network voltage based on the TMR microcurrent measurement principle of the present invention. DETAILED DESCRIPTION

[0030] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to provide a thorough and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments shown in the accompanying drawings is not intended to limit the present invention. In the accompanying drawings, identical elements are denoted by the same reference numerals.

[0031] Unless otherwise specified, the terms used herein (including technical terms) have the meanings commonly understood by those skilled in the art. In addition, it is understood that terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0032] The present invention proposes a device for measuring the voltage of a DC distribution network based on the principle of TMR measurement of microcurrent. Figure 1 Shown, including:

[0033] A high-resistance resistor is connected to the DC bus voltage of the DC distribution network to be measured, the DC bus voltage is converted into a DC low current signal, and the DC low current signal is transmitted to the current transformer;

[0034] The current transformer receives a DC low current signal and converts the DC low current signal into an AC micro current signal at a preset ratio and transmits it to the diode rectifier bridge;

[0035] The diode rectifier bridge receives the AC microcurrent signal, converts the AC microcurrent signal into a DC microcurrent signal, and transmits it to the TMR microcurrent measurement bridge;

[0036] The microcurrent measurement bridge receives the DC microcurrent signal and outputs the magnetic field generated by the DC microcurrent signal in the form of a differential voltage. The differential voltage is measured, and the output differential voltage is the DC distribution network voltage.

[0037] The high-resistance resistor is the primary measuring end of the device, and the current transformer is used to electrically isolate the primary measuring end.

[0038] A micro-current measurement bridge, comprising: a current-carrying U-shaped conductor, a first MTJ element, a second MTJ element, a third MTJ element, a fourth MTJ element, and a reference power supply;

[0039] One end of the U-shaped conductor is an output resistor, which receives a DC micro-current signal. The DC micro-current signal flows under the third MTJ element, the second MTJ element, the first MTJ element, and the fourth MTJ element, and outputs the magnetic field generated by the DC micro-current signal in the form of a differential voltage. The other end of the U-shaped conductor is used as a secondary measurement end of a micro-current measurement bridge to measure the differential voltage.

[0040] One end of the first MTJ element and one end of the second MTJ element are commonly connected to the positive input end of the reference voltage source, and one end of the third MTJ element and one end of the fourth MTJ element are commonly connected to the negative input end of the reference voltage source;

[0041] The other end of the first MTJ element and the other end of the third MTJ element are commonly connected to the positive polarity end of the secondary measurement end, and the other end of the second MTJ element and the other end of the fourth MTJ element are commonly connected to the negative polarity end of the secondary measurement end.

[0042] The high-resistance resistor is composed of multiple resistors with the same resistance connected in series, one end of which is connected to a DC bus voltage measurement point of the DC distribution network, and the other end of which is connected to a reference point through a current-carrying conductor.

[0043] A current transformer, comprising: a current-carrying conductor, a first secondary winding, and a second secondary winding;

[0044] The current-carrying conductor serves as the primary winding of the current transformer, and the primary winding comprises: a first iron core and a second iron core;

[0045] One end of the first secondary winding is connected in series with the second secondary winding in reverse direction, the other end of the first secondary winding is connected to a diode rectifier bridge, and the second secondary winding is connected to an excitation demagnetization device.

[0046] A diode rectifier bridge comprises a first diode, a second diode, a third diode and a fourth diode;

[0047] The cathode of the first diode and the cathode of the second diode are commonly connected to the secondary measurement end of the current-carrying U-shaped conductor, and the anode of the third diode and the anode of the fourth diode are commonly connected to one end of the output resistor of the current-carrying U-shaped conductor.

[0048] The present invention will be further described below in conjunction with embodiments:

[0049] like Figure 1 and Figure 2 As shown, Figure 2 for Figure 1 The logic diagram of the present invention comprises: a high-resistance resistor, a Kramer-type current transformer, a diode rectifier bridge, and a TMR microcurrent measuring bridge, wherein the microcurrent measuring bridge is a TMR microcurrent measuring bridge, and the current transformer is a Kramer-type current transformer;

[0050] A high-resistance resistor is connected to the current transformer, a diode rectifier bridge is connected in parallel with the current transformer, and a microcurrent measurement bridge is connected in parallel with the diode rectifier bridge.

[0051] The high-resistance resistor is used to convert the DC bus voltage to be measured into a small DC current signal, which flows through the primary side of the Kramer current transformer (the conductor passing through the double iron core).

[0052] The Kramer type current transformer is used to proportionally reflect the DC small current signal flowing through its primary winding (the conductor passing through the double iron core) into an AC micro-current signal flowing through the secondary winding, and to achieve electrical isolation for the primary measurement end;

[0053] The diode rectifier bridge is used to convert the AC micro-current signal at the input end into a DC micro-current signal, ensuring that the micro-current signal measured by the TMR micro-current measurement bridge at the secondary measurement end is a DC variable;

[0054] The TMR microcurrent measurement bridge is used to output the magnetic field generated by the DC microcurrent signal in the form of a differential voltage, thereby reflecting the transformation of the DC bus voltage at the primary measurement end.

[0055] The high-resistance resistor can actually be composed of several precise resistors R1, R2, ..., Rn with the same resistance value connected in series.

[0056] One end of the combined high-resistance resistor is connected to the DC bus voltage measurement point, and the other end is connected to the reference location through a current-carrying conductor, forming a small current situation that is approximately open circuit between the DC bus voltage measurement point and the reference location. The DC bus voltage to be measured is basically borne by the high-resistance resistor.

[0057] The Kramer-type current transformer includes a current-carrying conductor w1 as a primary winding, a first core Core1, a second core Core2, a first secondary winding w21, and a second secondary winding w22. The first secondary winding w21 and the second secondary winding w22 are connected in reverse series via a respective end. The other end of the first secondary winding w21 is connected to the anode of the first diode D1 and the cathode of the third diode D3 in the diode rectifier bridge.

[0058] The secondary measuring end of the TMR micro-current measurement bridge and the other end of the current-carrying "U"-shaped conductor are connected to the other end of the output resistor Rout.

[0059] The current-carrying “U”-shaped conductor will flow under the third MTJ element RTMR3 , the second MTJ element RTMR2 , the first MTJ element RTMR1 , and the fourth MTJ element RTMR4 of the TMR micro-current measurement bridge in sequence.

[0060] like Figure 3As shown, one end of RTMR1 is connected to RTMR2, and one end of RTMR2 is connected to one end of RTMR4;

[0061] The other end of RTMR4 is connected to RTMR3, and the other end of RTMR3 is connected to the other end of RTMR1.

[0062] One end of the first MTJ element RTMR1 and one end of the second MTJ element RTMR2 are commonly connected to the positive input terminal of the reference voltage source Vcc, and one end of the third MTJ element RTMR3 and one end of the fourth MTJ element RTMR4 are commonly connected to the negative input terminal of the reference voltage source Vcc; the other end of the first MTJ element RTMR1 and the other end of the third MTJ element RTMR3 are commonly connected to the positive polarity terminal of the secondary side output terminal Vout, and the other end of the second MTJ element RTMR2 and the other end of the fourth MTJ element RTMR4 are commonly connected to the negative polarity terminal of the secondary side output terminal Vout.

[0063] The secondary measuring end of the TMR micro-current measurement bridge and the other end of the current-carrying "U"-shaped conductor are connected to the other end of the output resistor Rout.

[0064] The present invention also proposes a method for measuring the voltage of a DC distribution network based on the principle of TMR measurement of microcurrent. Figure 4 Shown, including:

[0065] A high-resistance resistor is connected to the DC bus voltage of the DC distribution network to be measured, converts the DC bus voltage into a DC low current signal, and transmits the DC low current signal to a current transformer;

[0066] The current transformer receives a DC low current signal and converts the DC low current signal into an AC micro current signal at a preset ratio and transmits it to the diode rectifier bridge;

[0067] The diode rectifier bridge receives the AC microcurrent signal, converts the AC microcurrent signal into a DC microcurrent signal and transmits it to the TMR microcurrent measurement bridge;

[0068] The microcurrent measurement bridge receives the DC microcurrent signal and outputs the magnetic field generated by the DC microcurrent signal in the form of a differential voltage. The differential voltage is measured, and the output differential voltage is the DC distribution network voltage.

[0069] The working principle is analyzed as follows:

[0070] For the magnetic field generated by the "U"-shaped current-carrying conductor at the secondary measuring end, according to the Biot-Savart law: the magnitude of the magnetic induction intensity dB generated by the current element Idl at a point P in space is proportional to the size of the current element Idl.

[0071] The corresponding equation is expressed as:

[0072]

[0073] Using the quantum tunneling method, based on the tunneling coefficient (affected by the magnetic field), the tunneling current of the TMR element at non-zero temperature is expressed as follows:

[0074]

[0075] The voltage across the free layer and the pinned layer in the layered structure of the TMR element is constant, so the magnetic field affects the current flow capacity of the TMR element, resulting in a change in magnetoresistance.

[0076] like Figure 3 In the Wheatstone bridge structure shown, which consists of four TMR elements (with initial magnetic resistance R), the four elements are unshielded and are generally placed facing the "U"-shaped current loop to be measured, with the magnetic field direction parallel to the plane direction of the barrier layer.

[0077] Affected by the direction of the magnetic field, when the angle between the magnetic moment of the free layer and the magnetic moment of the pinned layer approaches 0 degrees, the corresponding MTJ resistance decreases; when it approaches 180 degrees, the corresponding MTJ resistance increases. The bridge accurately represents the rate of change of the MTJ resistance through the differential output voltage.

[0078] The bridge output voltage of four TMR elements is expressed as follows:

[0079]

[0080] Figure 3 The decrease in RTMR1 and RTMR4 is equal to the increase in RTMR2 and RTMR3, both of which are ΔR.

[0081] The output of the bridge is therefore:

[0082]

[0083] In the Kramer current transformer at the primary measuring end, the two secondary windings of the iron core (both with turns w2) are connected in series in opposite directions. Under the action of excitation and demagnetization, the current I1 flowing through the primary conductor (with turns w1) and the rectified current I2 on the secondary side have the following proportional relationship:

[0084]

[0085] The high-resistance resistor occupies most of the voltage between the DC bus voltage measurement point and the reference point. Therefore, the more accurate I2 obtained by the TMR micro-current measurement bridge is mapped to I1 of the primary side of the current transformer through the above formula, and the product of the high-resistance resistor is the DC bus voltage to be measured.

[0086] The present invention converts voltage measurement into current measurement, and utilizes the principle of TMR elements with high sensitivity, wide linear range and small temperature drift to accurately measure microcurrent, thereby making up for the shortcomings of voltage measurement based on voltage divider structure in terms of accuracy and stability.

[0087] In addition, the present invention broadens the application scope of TMR elements beyond measuring magnetic fields, currents, and displacements, and proposes for the first time the use of TMR elements to measure voltage variables.

Claims

1. A device for measuring the voltage of a DC distribution network based on the principle of TMR measurement of microcurrent, the device comprising: A high-resistance resistor is connected to a DC bus voltage of a DC distribution network to be tested, the DC bus voltage is converted into a DC low current signal, and the DC low current signal is transmitted to a current transformer; A current transformer receives a DC low current signal and converts the DC low current signal into an AC micro current signal at a preset ratio and transmits it to a diode rectifier bridge; The diode rectifier bridge receives the AC micro-current signal, converts the AC micro-current signal into a DC micro-current signal, and transmits it to the TMR micro-current measurement bridge; The micro-current measuring bridge receives the DC micro-current signal and outputs the magnetic field generated by the DC micro-current signal in the form of a differential voltage. The differential voltage is measured and the output differential voltage is the DC distribution network voltage. The micro-current measurement bridge comprises: a current-carrying U-shaped conductor, a first MTJ element, a second MTJ element, a third MTJ element, a fourth MTJ element and a reference power supply; One end of the U-shaped conductor is an output resistor, which receives a DC micro-current signal. The DC micro-current signal flows under the third MTJ element, the second MTJ element, the first MTJ element, and the fourth MTJ element, and the magnetic field generated by the DC micro-current signal is output in the form of a differential voltage. The other end of the U-shaped conductor is used as a secondary measurement end of a micro-current measurement bridge to measure the differential voltage. One end of the first MTJ element and one end of the second MTJ element are commonly connected to the positive input end of the reference voltage source, and one end of the third MTJ element and one end of the fourth MTJ element are commonly connected to the negative input end of the reference voltage source; The other end of the first MTJ element and the other end of the third MTJ element are commonly connected to the positive polarity end of the secondary measurement end, and the other end of the second MTJ element and the other end of the fourth MTJ element are commonly connected to the negative polarity end of the secondary measurement end; The high-resistance resistor is the primary measurement end of the device, and the current transformer is used to electrically isolate the primary measurement end; The high-resistance resistor is composed of a plurality of resistors with the same resistance value connected in series, one end of which is connected to a DC bus voltage measurement point of a DC distribution network, and the other end of which is connected to a reference point via a current-carrying conductor; The current transformer comprises: a current-carrying conductor, a first secondary winding and a second secondary winding; The current-carrying conductor serves as a primary winding of a current transformer, and the primary winding comprises: a first iron core and a second iron core; One end of the first secondary winding is connected in series with the second secondary winding in reverse order, and the other end of the first secondary winding is connected to the diode rectifier bridge.

2. The device according to claim 1, wherein the diode rectifier bridge comprises: a first diode, a second diode, a third diode, and a fourth diode; The cathode of the first diode and the cathode of the second diode are commonly connected to the secondary measurement end of the current-carrying U-shaped conductor, and the anode of the third diode and the anode of the fourth diode are commonly connected to one end of the output resistor of the current-carrying U-shaped conductor.

3. A method for measuring the voltage of a DC distribution network based on the principle of TMR measurement of microcurrent using a device as claimed in any one of claims 1 to 2, the method comprising: A high-resistance resistor is connected to the DC bus voltage of the DC distribution network to be tested, the DC bus voltage is converted into a DC low current signal, and the DC low current signal is transmitted to the current transformer; The current transformer receives a DC low current signal, and converts the DC low current signal into an AC micro current signal at a preset ratio and transmits it to a diode rectifier bridge; The diode rectifier bridge receives the AC micro-current signal, converts the AC micro-current signal into a DC micro-current signal and transmits it to the TMR micro-current measurement bridge; The micro-current measurement bridge receives the DC micro-current signal, and outputs the magnetic field generated by the DC micro-current signal in the form of a differential voltage. The differential voltage is measured, and the output differential voltage is the DC distribution network voltage.

Images