Self-oscillation type alternating current and direct current zero-flux current transformer

Abstract

The utility model discloses a self-oscillation type alternating-current and direct-current zero-flux current transformer which is characterized in that the alternating-current and direct-current zero-flux current transformer comprises a first direct-current magnetic modulation coil T1, a second direct-current magnetic modulation coil T2, an intermediate-frequency alternating-current coil T3, a high-frequency alternating-current coil T4 and a circuit module; the first direct-current magnetic modulation coil T1 comprises a first direct-current magnetic modulation coil iron core C1, a first direct-current magnetic modulation coil excitation winding W1 and a first section of secondary winding Ws; the second direct-current magnetic modulation coil iron core T2 comprises a second direct-current magnetic modulation coil iron core C2, a second direct-current magnetic modulation coil excitation winding W2 and a second section of secondary winding Ws; the first direct-current magnetic modulation coil excitation winding W1 and the second direct-current magnetic modulation coil excitation winding W2 have the same number of turns and are uniformly and densely wound on the circumferences of the first direct-current magnetic modulation coil iron core C1 and the second direct-current magnetic modulation coil iron core C2 respectively.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of current transformers, and more particularly, to a self-excitation oscillation type AC / DC zero flux current transformer. BACKGROUND

[0002] The AC / DC zero flux current transformer is widely used in high-accuracy AC / DC zero flux current measurement scenes in the fields of power, industry, railway, medical treatment, etc. Due to its characteristics of high precision, fast response and wide frequency band, the AC / DC zero flux current transformer effectively guarantees the smooth, accurate and high-performance application of the electrical control system.

[0003] The AC / DC zero flux current transformer mainly consists of DC measurement and AC measurement. The AC measurement mainly depends on the active compensation current transformer, and the technology is relatively mature. The core principle of the DC measurement is the flux gate technology. The AC / DC zero flux detector thereof is two pairs of opposite and symmetrical iron cores connected in series. The two pairs of symmetrical iron cores are excited by a square wave, a triangular wave or a sine wave. The demodulation circuit senses the even harmonic wave generated due to the DC flux of the primary winding, and drives the operational amplifier to excite the secondary winding to generate a DC compensation current, so as to reach the AC / DC zero flux state of the DC ampere-turn balance. The size of the secondary DC current can accurately reflect the size of the primary DC current.

[0004] The traditional AC / DC zero flux current transformer needs to generate an excitation signal of a certain frequency through a crystal oscillator, and then a complex phase-sensitive demodulation circuit or a peak difference demodulation circuit is used to demodulate the measured DC signal. The circuit technology of the excitation and demodulation scheme is complex, and the cost and energy consumption are high. This has become one of the problems restricting the popularization and application of the AC / DC zero flux technology.

[0005] At the same time, the DC obtained by the demodulation inevitably brings about ripple, and for high-frequency measurement, the ripple current is equivalent to a certain internal harmonic disturbance. The ripple caused by the asymmetry of the magnetic properties of the iron core is called induced ripple, and the ripple caused by the excitation circuit, the demodulation circuit and other electronic parts is called modulation ripple. The size of the ripple will affect the effect of the DC measurement. Therefore, reducing the ripple has become one of the difficulties of the flux gate technology. SUMMARY

[0006] According to the present application, a self-excitation oscillation type AC / DC zero flux current transformer is provided to solve the technical problems of the traditional AC / DC zero flux current transformer, i.e. the circuit technology of the excitation and demodulation scheme is complex, the cost and energy consumption are high, and the DC obtained by the demodulation inevitably brings about ripple.

[0007] According to a first aspect of the present application, a self-excitation oscillation type AC / DC zero flux current transformer is provided, comprising:

[0008] The AC-DC zero magnetic flux current transformer comprises a first DC magnetic modulation wire package T1, a second DC magnetic modulation wire package T2, a middle frequency AC wire package T3, the high frequency AC wire package T4 and a circuit module;

[0009] The first DC magnetic modulation wire package T1 comprises a first DC magnetic modulation wire package core C1, a first DC magnetic modulation wire package excitation winding W1 and a first section of secondary winding W s The second DC magnetic modulation wire package core T2 comprises a second DC magnetic modulation wire package core C2, a second DC magnetic modulation wire package excitation winding W2 and a second section of secondary winding W s ;

[0010] The number of turns of the first DC magnetic modulation wire package excitation winding W1 and the second DC magnetic modulation wire package excitation winding W2 are equal, and are uniformly and densely wound on the circumferences of the first DC magnetic modulation wire package core C1 and the second DC magnetic modulation wire package core C2 respectively.

[0011] Optionally, the middle frequency AC wire package T3 comprises a middle frequency AC wire package core C3, a middle frequency AC wire package detection winding W3 and a third section of secondary winding W s ;

[0012] The middle frequency AC wire package detection winding W3 is uniformly and densely wound on the circumference of the middle frequency AC wire package core C3;

[0013] The middle frequency AC wire package core C3 is surrounded outside the first DC magnetic modulation wire package core C1 and the second DC magnetic modulation wire package core C2, and the middle frequency AC wire package core C3 functions as a magnetic shield of the first DC magnetic modulation wire package core C1 and the second DC magnetic modulation wire package core C2 in addition to being an induction core of a middle frequency signal.

[0014] Optionally, the high frequency AC wire package T4 comprises a high frequency AC wire package core C4, a high frequency AC wire package detection winding W4 and a fourth section of secondary winding W s ;

[0015] The high frequency AC wire package detection winding W4 is uniformly and densely wound on the circumference of the high frequency AC wire package core C4;

[0016] The middle frequency AC wire package core C3 is surrounded outside the high frequency AC wire package core C4, and functions as a magnetic shield of the high frequency AC wire package core C4 in addition to being an induction core of a middle frequency signal.

[0017] Optionally, the AC-DC zero magnetic flux current transformer further comprises a primary winding W p The primary winding W p is a one-turn through conductor passing through the center apertures of the first DC magnetic modulation wire package T1, the second DC magnetic modulation wire package T2, the middle frequency AC wire package T3 and the high frequency compensation wire package T4;

[0018] Secondary winding W s The first DC magnetic modulation wire package T1, the second DC magnetic modulation wire package T2, the intermediate frequency AC wire package T3, and the high frequency compensation wire package T4 are uniformly and densely wound on the whole wire package circumference.

[0019] Optionally, the circuit module comprises a self-oscillating circuit, a low-pass filter, a band-pass filter, a high-pass filter, an intermediate frequency signal amplifier, a high frequency signal amplifier, a power amplifier, and a load resistor.

[0020] The self-oscillating circuit comprises a first threshold voltage setting resistor R1, a second threshold voltage setting resistor R2, a first excitation current sampling resistor R3, a second excitation current sampling resistor R4, and a comparator.

[0021] Optionally, the first DC magnetic modulation wire package core C1 and the first DC magnetic modulation wire package excitation winding W1 form a non-linear inductor L1, the second DC magnetic modulation wire package core C2 and the second DC magnetic modulation wire package excitation winding W2 form a non-linear inductor L2, and the self-oscillating circuit and the non-linear inductors L1 and L2 form a self-oscillating circuit.

[0022] Optionally, the negative input end of the comparator is connected to the non-polarity end of the first excitation current sampling resistor R3 and the non-polarity end of the first DC magnetic modulation wire package excitation winding W1, respectively, the other end of the first excitation current sampling resistor R3 is grounded, the positive input end of the comparator is connected to one end of the first threshold voltage setting resistor R1 and one end of the second threshold voltage setting resistor R2, respectively, one end of the second threshold voltage setting resistor R2 is grounded, the other end of the second threshold voltage setting resistor R2 is connected to the polarity end of the first DC magnetic modulation wire package excitation winding W1, the output end of the comparator is connected to the non-polarity end of the second DC magnetic modulation wire package excitation winding W2, the polarity end of the second DC magnetic modulation wire package excitation winding W2 is connected to one end of the second excitation current sampling resistor R4, the other end of the second excitation current sampling resistor R4 is grounded, the output end of the comparator is also connected to the input end of the low-pass filter, the non-polarity end of the intermediate frequency AC wire package detection winding W3 is connected to the band-pass filter, and the non-polarity end of the high frequency AC wire package detection winding W4 is connected to the high-pass filter.

[0023] The output voltage signal of the low-pass filter and the output voltage of the band-pass filter are added and connected to the first end of the intermediate frequency signal amplifier; the first end of the high frequency signal amplifier is connected to the voltage output end of the high-pass filter, the output voltage signal of the tail end and the output voltage of the high frequency signal amplifier are added and connected to the first end of the power amplifier, and the second end of the power amplifier is connected to the polarity end of the secondary winding W s , the load resistor is connected to the non-polarity end of the secondary winding W s .

[0024] Optionally, the self-oscillating circuit is in different working states, and the comparator output alternately changes two limit voltages ±U s , assuming that at the initial moment the positive input voltage U p of the comparator is greater than the negative input voltage U n of the comparator, at this moment the output voltage of the comparator is the positive limit voltage U s , and U p = U s *R1 / (R1+R2), the output voltage of the comparator is U s , which acts on the nonlinear inductance L1 of the first DC magnetic modulation line package excitation winding W1, so that the excitation current I ex1 in the nonlinear inductance L1 increases from zero, and the voltage U n on the excitation current sampling resistor R3 in the same loop also increases accordingly, when the voltage increases to U n > U p , the output of the comparator flips to the negative limit voltage -U s , and U p = -U s *R1 / (R1+R2), -U s acts on the nonlinear inductance L1 of the excitation winding W1, so that the excitation current I ex1 begins to decrease to a negative value, and the voltage U n on the first excitation current sampling resistor R3 in the same loop also decreases to a negative value accordingly, when the voltage increases to U n <U p , the comparator will output the positive limit voltage U s again, due to the symmetry of the excitation performance of the core T1, the comparator will continuously output the positive voltage U s and the positive voltage -U s with a fixed period t1 and t2, that is, a square wave signal with a period of t1+t2 and an amplitude of U s .

[0025] Optionally, when a direct current flows in the primary winding W p , the symmetry of the core excitation performance is destroyed, a bias proportional to the direct current is generated, which causes the time of the comparator outputting the positive limit voltage U s and the negative limit voltage -U s to be inconsistent t1≠t2, and the degree of inconsistency Δt is proportional to the direct current flowing in the primary winding;

[0026] The comparator output square wave signal excites two anti-parallel first DC magnetic modulation line packages T1 and second DC magnetic modulation line packages T2, so that the same excitation generates magnetic fluxes with equal size and opposite directions in the first DC magnetic modulation line package T1 and the second DC magnetic modulation line package T2, which offset each other.

[0027] The low-pass filter filters the high-frequency signal of the square wave voltage signal of the comparator output, and directly converts it into a corresponding direct current voltage signal;

[0028] The band-pass filter filters the low-frequency and high-frequency parts of the alternating voltage signal induced in the intermediate-frequency alternating current line package detection winding W3, and amplifies and outputs the intermediate-frequency alternating voltage small signal and the direct current voltage small signal through the intermediate-frequency amplifier;

[0029] The high-pass filter filters the low-frequency part of the alternating voltage signal induced in the high-frequency alternating current line package detection winding W4, and then amplifies and outputs the high-frequency alternating voltage small signal through the high-frequency amplifier.

[0030] Optionally, the power amplifier further amplifies the voltage signal to drive the secondary winding and the load resistor to output a secondary current;

[0031] The load resistor converts the current signal into a voltage signal;

[0032] The second direct current magnetic modulation line package excitation winding W s When there is a ripple current, the ripple magnetic flux will generate an induced potential on the high-frequency alternating current line package detection winding W4 of the high-frequency induction line package, and drive the high-frequency signal amplifier and the power amplifier to generate an opposite current in the secondary winding, so as to offset the ripple and high-frequency harmonics until the ripple magnetic flux induced in the high-frequency alternating current line package T4 is zero.

[0033] Therefore, when the AC / DC zero magnetic flux current transformer adopts phase-sensitive demodulation, the system ripple is mainly the modulation ripple; when the AC / DC zero magnetic flux current transformer adopts peak difference demodulation, the system ripple includes the induced ripple and the modulation ripple. Regardless of the excitation demodulation mode, a complex crystal oscillator excitation and demodulation circuit is needed. At the same time, the existing AC / DC zero magnetic flux transformer generally adopts a three-core four-winding structure, and the induced ripple and the modulation ripple are amplified by the signal amplifier and the power amplifier and then output to the secondary winding. The ripple cannot be simply eliminated by a filter circuit because when there is a high-frequency signal in the primary, the secondary cannot normally react to the primary signal waveform after filtering. The self-oscillation circuit does not permit the generation of a high-frequency signal oscillation excitation by a crystal oscillator. At the same time, the demodulation circuit is a simple low-pass filter circuit which is easy to implement. At the same time, a high-frequency induction line package T4 is added, and through negative feedback and the principle of AC / DC zero magnetic flux, the secondary can accurately perceive the primary high-frequency signal, and at the same time, the ripple signal generated in the system can be greatly offset, so as to achieve the effect of significantly reducing the system ripple interference. BRIEF DESCRIPTION OF DRAWINGS

[0034] The exemplary embodiments of this application can be more completely understood in consideration of the following detailed description in connection with the following drawings, in which:

[0035] Figure 1Structure principle diagram of self-excitation oscillation type AC / DC zero magnetic flux current standarder described in the embodiment;

[0036] Figure 2 Structure principle diagram of self-excitation oscillation type AC / DC zero magnetic flux current standarder described in the embodiment;

[0037] Figure 3 DC core excitation curve diagram described in the embodiment;

[0038] Wherein, T1-first DC magnetic modulation wire package, T2-second DC magnetic modulation wire package, T3-medium frequency AC wire package, T4-high frequency AC wire package, C1-first DC magnetic modulation wire package core, C2-second DC magnetic modulation wire package core, C3-medium frequency AC wire package core, C4-high frequency AC wire package core, W1-first DC magnetic modulation wire package excitation winding, W2-second DC magnetic modulation wire package excitation winding, W3-medium frequency AC wire package detection winding, W4-high frequency AC wire package detection winding, W p Primary winding, W s Secondary winding, R1-first threshold voltage setting resistance, R2-second threshold voltage setting resistance, R3-first excitation current sampling resistance, R4-second excitation current sampling resistance, I p Primary current, I s Secondary current, I ex1 T1 wire package excitation current, I ex2 T2 wire package excitation current, U p Positive input voltage of comparator, U n Negative input voltage of comparator, U s Output voltage of comparator, U dc Output DC voltage of low pass filter, U acm Output medium frequency AC voltage of medium frequency signal amplifier, U ach Output high frequency AC voltage of high frequency signal amplifier, I dc Primary DC current, I s Secondary current. DETAILED DESCRIPTION

[0039] The present application will now be described with reference to the attached drawings, which are provided as non-limiting examples in order to provide a thorough and complete disclosure of the present application and fully convey the scope of the application to those skilled in the art. The terms of construction in the exemplary embodiments shown in the drawings are not a limitation of the present application. In the drawings, the same elements / elements are designated with the same reference numerals.

[0040] The terms used herein, including technical terms, have meanings commonly understood by those skilled in the art, unless otherwise specified. In addition, it is to be understood that the terms defined by commonly used dictionaries are to be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and not be interpreted in an idealized or overly formal sense unless otherwise indicated.

[0041] According to a first aspect of the present application, there is provided a self-oscillating AC / DC zero flux current transformer, comprising:

[0042] The AC / DC zero flux current transformer comprises a first DC magnetic modulation wire package T1, a second DC magnetic modulation wire package T2, a middle frequency AC wire package T3, the high frequency AC wire package T4 and a circuit module;

[0043] The first DC magnetic modulation wire package T1 comprises a first DC magnetic modulation wire package core C1, a first DC magnetic modulation wire package excitation winding W1 and a first section of secondary winding W s The second DC magnetic modulation wire package core T2 comprises a second DC magnetic modulation wire package core C2, a second DC magnetic modulation wire package excitation winding W2 and a second section of secondary winding W s ;

[0044] The number of turns of the first DC magnetic modulation wire package excitation winding W1 and the second DC magnetic modulation wire package excitation winding W2 are equal, and are uniformly and densely wound on the circumferences of the first DC magnetic modulation wire package core C1 and the second DC magnetic modulation wire package core C2, respectively.

[0045] Optionally, the middle frequency AC wire package T3 comprises a middle frequency AC wire package core C3, a middle frequency AC wire package detection winding W3 and a third section of secondary winding W s ;

[0046] The middle frequency AC wire package detection winding W3 is uniformly and densely wound on the circumference of the middle frequency AC wire package core C3;

[0047] The middle frequency AC wire package core C3 is surrounded outside the first DC magnetic modulation wire package core C1 and the second DC magnetic modulation wire package core C2, and the middle frequency AC wire package core C3, in addition to being an induction core of a middle frequency signal, also serves as a magnetic shield of the first DC magnetic modulation wire package core C1 and the second DC magnetic modulation wire package core C2.

[0048] Optionally, the high frequency AC wire package T4 comprises a high frequency AC wire package core C4, a high frequency AC wire package detection winding W4 and a fourth section of secondary winding W s ;

[0049] The high frequency AC wire package detection winding W4 is uniformly and densely wound on the circumference of the high frequency AC wire package core C4;

[0050] The middle frequency AC line package iron core C3 is surrounded by the high frequency AC line package iron core C4, and in addition to being an inductive iron core for middle frequency signals, it also serves as a magnetic shield for the high frequency AC line package iron core C4.

[0051] Optionally, the AC-DC zero flux current transformer further comprises a primary winding W p a primary winding W p is a single turn of a through conductor, and passes through the central apertures of the first DC magnetic modulation line package T1, the second DC magnetic modulation line package T2, the middle frequency AC line package T3, and the high frequency compensation line package T4;

[0052] a secondary winding W s is uniformly and densely wound around the overall line package circumference formed by the first DC magnetic modulation line package T1, the second DC magnetic modulation line package T2, the middle frequency AC line package T3, and the high frequency compensation line package T4.

[0053] Optionally, the circuit module comprises a self-oscillating oscillator, a low pass filter, a band pass filter, a high pass filter, a middle frequency signal amplifier, a high frequency signal amplifier, a power amplifier, and a load resistor.

[0054] The self-oscillating oscillator comprises a first threshold voltage setting resistor R1, a second threshold voltage setting resistor R2, a first excitation current sampling resistor R3, a second excitation current sampling resistor R4, and a comparator.

[0055] Optionally, the first DC magnetic modulation line package iron core C1 and the first DC magnetic modulation line package excitation winding W1 form a non-linear inductor L1, the second DC magnetic modulation line package iron core C2 and the second DC magnetic modulation line package excitation winding W2 form a non-linear inductor L2, and the self-oscillating oscillator and the non-linear inductors L1 and L2 form a self-oscillating circuit.

[0056] Optionally, the negative input terminal of the comparator is connected to the non-polarity terminal of the first excitation current sampling resistor R3 and the first DC magnetic modulation line package excitation winding W1, respectively, the other terminal of the first excitation current sampling resistor R3 is grounded, the positive input terminal of the comparator is connected to one terminal of the first threshold voltage setting resistor R1 and the second threshold voltage setting resistor R2, respectively, one terminal of the second threshold voltage setting resistor R2 is grounded, the other terminal of the second threshold voltage setting resistor R2 is connected to the polarity terminal of the first DC magnetic modulation line package excitation winding W1, the output terminal of the comparator is connected to the non-polarity terminal of the second DC magnetic modulation line package excitation winding W2, the polarity terminal of the second DC magnetic modulation line package excitation winding W2 is connected to one terminal of the second excitation current sampling resistor R4, the other terminal of the second excitation current sampling resistor R4 is grounded, the output terminal of the comparator is also connected to the input terminal of the low pass filter, the non-polarity terminal of the middle frequency AC line package detection winding W3 is connected to the band pass filter, and the non-polarity terminal of the high frequency AC line package detection winding W4 is connected to the high pass filter.

[0057] The output voltage signal of the low-pass filter is added to the output voltage of the band-pass filter and connected to the first terminal of the intermediate frequency (IF) signal amplifier. The first terminal of the high-frequency (HF) signal amplifier is connected to the voltage output terminal of the high-pass filter, and the output voltage signal of the second terminal is added to the output voltage of the HF signal amplifier and connected to the first terminal of the power amplifier. The second terminal of the power amplifier is connected to the secondary winding W. s Polarity connection, load resistor and secondary winding W s Non-polar terminal connection.

[0058] Optionally, the self-excited oscillation circuit operates in different states, and the comparator output alternately changes between two limiting levels ±U over time. s Assume the voltage U at the positive input of the comparator at the initial moment p The voltage U at the negative input terminal of the comparator n At this time, the comparator outputs a positive limit voltage U. s , and U p =U s *R1 / (R1+R2), comparator output voltage U s The nonlinear inductance L1 acting on the first DC magnetic modulation coil excitation winding W1 causes the excitation current I in the nonlinear inductance L1 to... ex1 Starting from zero and increasing, the voltage U across the excitation current sampling resistor R3 in the same circuit... n It will also increase similarly when its voltage increases to U. n >U p When this happens, the comparator output flips to the negative limit voltage -U. s , and U p =﹣U s *R1 / (R1+R2),﹣U s The nonlinear inductance L1 acting on the excitation winding W1 causes the excitation current I to... ex1 As the voltage decreases to a negative value, the voltage U across the first excitation current sampling resistor R3 in the same circuit... n It will also decrease to a negative value when its voltage increases to U. n p At this time, the comparator will output a positive limit voltage U. s Due to the symmetry of the excitation properties of the iron core T1, the comparator will continuously output a positive voltage U with fixed periods t1 and t2. s and forward voltage -U s That is, the period is t1+t2 and the amplitude is U s The square wave signal.

[0059] Optionally, the self-excited oscillation circuit, when the primary winding W p When a direct current flows through the iron core, the symmetry of the excitation properties is disrupted, generating a bias proportional to the direct current, which causes the comparator to output a positive limit voltage U.​s and negative limit voltage -U s The time inconsistency t1≠t2, and the degree of inconsistency Δt is proportional to the DC current flowing in the primary winding;

[0060] The comparator output square wave signal excites two anti-connection first DC magnetic modulation line package T1 and second DC magnetic modulation line package T2, and the same excitation generates magnetic flux with equal size and opposite direction in the first DC magnetic modulation line package T1 and the second DC magnetic modulation line package T2, which offset each other;

[0061] The low-pass filter filters the high-frequency signal of the comparator output square wave voltage signal and directly converts it into a corresponding DC voltage signal;

[0062] The band-pass filter filters the low-frequency and high-frequency parts of the AC voltage signal induced in the intermediate-frequency AC line package detection winding W3, and the intermediate-frequency amplifier amplifies and outputs the intermediate-frequency AC voltage small signal and the DC voltage small signal;

[0063] The high-pass filter filters the low-frequency part of the AC voltage signal induced in the high-frequency AC line package detection winding W4, and the high-frequency amplifier amplifies and outputs the high-frequency AC voltage small signal.

[0064] Optionally, the power amplifier further amplifies the voltage signal to drive the secondary winding and the load resistance to output the secondary current;

[0065] The load resistance converts the current signal into a voltage signal;

[0066] The second DC magnetic modulation line package excites the winding W s When the ripple current occurs in the winding W

[0067] Referring to Figure 1 , Figure 1 a principle diagram of a low-ripple AC / DC zero-magnetic-flux current transformer with four iron cores and five windings is given. The AC / DC zero-magnetic-flux current transformer is composed of two DC magnetic modulation line packages, one intermediate-frequency AC line package, one high-frequency compensation line package, and a circuit module. The DC magnetic modulation line package T1 is composed of an excitation winding W1, a secondary winding W s , and an iron core C1, the DC magnetic modulation line package T2 is composed of an excitation winding W2, a secondary winding W s , and an iron core C2, the intermediate-frequency AC line package T3 is composed of a detection winding W3, an iron core C3, and a secondary winding W sThe high-frequency AC line package T4 is composed of a detection winding W4, a core C4 and a secondary winding W s The circuit module is composed of a self-oscillation circuit, a low-pass filter, a band-pass filter, a high-pass filter, an intermediate-frequency signal amplifier, a high-frequency signal amplifier, a power amplifier and a load resistor. The self-oscillation circuit is composed of threshold voltage setting resistors R1 and R2, excitation current sampling resistors R3 and R4 and a comparator. The core C1 and the excitation winding W1 form a non-linear inductor L1, and the core C2 and the excitation winding W2 form a non-linear inductor L2. The self-oscillation circuit and the non-linear inductors L1 and L2 form a self-oscillation circuit.

[0068] As shown in Figure 2 , the excitation winding W1 of the DC magnetic modulation line package T1 is uniformly wound on the outer wall of the core C1, the excitation winding W2 of the DC magnetic modulation line package T2 is uniformly wound on the outer wall of the core C2, and the two line packages have basically the same size after being wound and can be placed in parallel. The detection winding W3 of the intermediate-frequency AC line package T3 is uniformly wound on the outer wall of the core C3, and the line package is placed outside the DC magnetic modulation line package after being wound, thereby simultaneously playing a role of magnetic shielding of the DC magnetic modulation line package. The detection winding W4 of the high-frequency AC line package T4 is uniformly wound on the outer wall of the core C4, and the line package is placed inside the DC magnetic modulation line package after being wound, thereby also simultaneously playing a role of magnetic shielding of the DC magnetic modulation line package. The four line packages are placed in the relative positions, and finally, the secondary winding is uniformly wound on the outer side to form a whole line package of the AC / DC zero-magnetic-flux current transformer. Figure 2

[0069] When the AC and DC currents exist in the primary winding Wp, the oscillator excites the two reverse-connected DC magnetic modulation line packages T1 and T2 by outputting a square wave, a triangular wave or a sine signal, and the odd harmonic components in the voltage signals induced on W1 and W2 cancel each other out, and the even harmonic components are added. The demodulator converts the even harmonic components into a DC signal and outputs the DC signal;

[0070] As shown in Figure 1 , the self-oscillation circuit is in different working states, and the comparator outputs two limit levels ±U s alternately changing with time. p Assuming that the voltage U n at the input end of the comparator at the initial moment is greater than U s , at this moment, the positive limit voltage U p of the comparator is output, and U s =U s *R1 / (R1+R2), U ex1 acts on the non-linear inductor L1 of the excitation winding W1, so that the excitation current I n in L1 starts to increase, and the voltage U n on the excitation current sampling resistor R3 in the same loop also starts to increase.Also will increase, when the current to the flip current I th , so that U n > U p , the comparator output flip to negative limit voltage -U s , and U p = -U s *R1 / (R1+R2), -U s on the non-linear inductance L1 of the exciting winding W1, so that the excitation current I ex1 starts to decrease to negative value, then the voltage U n on the excitation current sampling resistance R3 in the same loop will also decrease to negative value, when the current to the flip current -I th , so that U n <U p , the comparator will output positive limit voltage U s , due to the symmetry of the core T1 excitation performance, as Figure 3 , I dc is zero, I ex1 from the flip current I th to -I th around the point O, the comparator will continuously output positive voltage U s and negative voltage -U s with fixed period t1 and t2, that is, the square wave signal with period t1+t2 and amplitude U s .

[0071] When the DC current flows in the primary winding W p , the symmetry of the core excitation performance is destroyed, which will produce a bias proportional to the DC, that is, I dc >0, then the core is excited and induced with (I dc , B dc ) as the center, due to the asymmetry and nonlinearity of the core operating point, leading to the time of the comparator output positive limit voltage U s and negative limit voltage -U s is not consistent t1<t2, and the degree of inconsistency Δt=t1-t2 is proportional to the DC flowing in the primary winding, the connected low-pass filter will filter the high-frequency signal of the comparator output square wave voltage signal, thereby directly converted into the corresponding DC voltage signal;

[0072] The AC signal and the DC signal are added to the output of the intermediate frequency signal amplifier. Due to the band-pass filter and the frequency gain characteristics of the amplifier, the DC to intermediate frequency signal can be amplified, and the high frequency signal is attenuated; the high frequency AC coil T4 can amplify the high frequency signal and attenuate the low frequency signal due to the high-pass filter and the frequency gain characteristics of the amplifier; the output of the high frequency AC signal and the output of the intermediate frequency signal amplifier are added to the output of the power amplifier to drive the secondary winding W s The secondary AC and DC current signals proportional to the primary winding W p are generated, and finally the current transformer reaches the negative feedback AC / DC zero flux state, and the secondary current flowing through the load resistor generates the secondary voltage signal.

[0073] The method for reducing the ripple of the AC / DC zero flux current transformer mainly increases the high frequency coil and the negative feedback circuit to offset the ripple and high frequency interference generated by the system. When the secondary winding W s has ripple current I r , according to the Ampere loop law:

[0074]

[0075] Where N2 is the number of turns of the secondary winding, and l is the average magnetic path length of the core C4.

[0076] According to the magnetic characteristics of the core, there are:

[0077] B = μH r (2)

[0078] Where μ is the permeability of the core C4.

[0079] Φ = BS (3)

[0080] Where S is the cross section of the core C4.

[0081] According to the law of electromagnetic induction, the ripple flux φ will generate an induced potential U r on the detection winding W4 of the high frequency induction coil, and drive the high frequency signal amplifier and the power in the secondary winding to generate the anti-phase ripple current I r , so as to offset the ripple current I r , until the ripple flux induced in the coil T4 is zero, that is

[0082] I r = I r '(4)

[0083] Therefore, when the AC-DC zero flux current transformer adopts phase-sensitive demodulation, the system ripple is mainly the modulation ripple; when the AC-DC zero flux current transformer adopts peak difference demodulation, the system ripple includes the induction ripple and the modulation ripple. No matter which excitation demodulation mode is adopted, a complex crystal oscillator excitation and demodulation circuit is needed. Meanwhile, the existing AC-DC zero flux transformer generally adopts a three-core four-winding structure, the induction ripple and the modulation ripple are amplified by a signal amplifier and a power amplifier and then output to the secondary winding, and cannot be simply eliminated by a filter circuit because when there is a high-frequency signal in the primary, the secondary cannot normally reflect the primary signal waveform after filtering. A high-frequency signal oscillation excitation is generated by a self-excitation oscillation circuit without a crystal oscillator, and the demodulation circuit is a simple low-pass filter circuit which is easy to realize, and a high-frequency induction coil T4 is added, through negative feedback and the AC-DC zero flux principle, the secondary can accurately perceive the primary high-frequency signal, and the ripple signal generated in the system can be greatly offset, so that the effect of significantly reducing the system ripple interference is achieved.

[0084] Those skilled in the art will understand that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present application can be implemented in various computer languages, such as object-oriented programming languages Java and interpreted scripting language JavaScript.

[0085] The present application is described with reference to flowcharts and / or block diagrams according to the methods, devices (systems), and computer program products of the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing apparatus to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing apparatus produce a device that implements the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one flow or multiple flows and / or blocks Figure 1 The functions specified in one flow or multiple flows and / or blocks

[0086] These computer program instructions can also be stored in a computer-readable memory that can guide the computer or other programmable data processing apparatus to work in a specific way, so that the instructions stored in the computer-readable memory produce a product including instruction devices that implement the functions specified in the flowcharts and / or block diagrams. Figure 1one or more processes and / or blocks Figure 1 the function specified in the one or more blocks.

[0087] These computer program instructions can also be loaded into computer or other programmable data processing devices, so that a series of operation steps are performed on the computer or other programmable data processing devices to generate computer-implemented processes, thus the instructions executed on the computer or other programmable data processing devices provide a process for implementing the flow Figure 1 one or more processes and / or blocks Figure 1 the function specified in the one or more blocks.

[0088] Although preferred embodiments of the application have been described, those skilled in the art will recognize that additional modifications and variations may be possible in light of the above disclosure. It is therefore intended that the appended claims cover all such modifications and variations as fall within the scope of the application.

[0089] Obviously, many modifications and variations of the present application are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims and their equivalents, the application can be practiced otherwise than as specifically described.

Claims

1. A self-oscillating AC-DC zero flux current transformer, characterized by, The application relates to an AC-DC zero-flux current transformer. The AC-DC zero-flux current transformer comprises a first DC magnetic modulation wire package T1, a second DC magnetic modulation wire package T2, a middle-frequency AC wire package T3, a high-frequency AC wire package T4 and a circuit module. The first direct-current magnetic modulation wire package T1 includes a first direct-current magnetic modulation wire package core C1, a first direct-current magnetic modulation wire package excitation winding W1, and a first section secondary winding W s The second direct-current magnetic modulation wire package core T2 includes a second direct-current magnetic modulation wire package core C2, a second direct-current magnetic modulation wire package excitation winding W2, and a second section secondary winding W s ; The turns of the first DC magnetic modulation wire package excitation winding W1 and the turns of the second DC magnetic modulation wire package excitation winding W2 are equal and are uniformly densely wound on the circumferences of the first DC magnetic modulation wire package core C1 and the second DC magnetic modulation wire package core C2 respectively.

2. The AC-DC zero-flux current transformer according to claim 1, wherein The intermediate frequency AC line package T3 comprises an intermediate frequency AC line package core C3, an intermediate frequency AC line package detection winding W3 and a third segment secondary winding W s ; The middle-frequency AC wire package detection winding W3 is uniformly densely wound on the circumference of the middle-frequency AC wire package core C3. The middle-frequency AC wire package core C3 is surrounded outside the first DC magnetic modulation wire package core C1 and the second DC magnetic modulation wire package core C2, and the middle-frequency AC wire package core C3 functions as a magnetic shield of the first DC magnetic modulation wire package core C1 and the second DC magnetic modulation wire package core C2 in addition to functioning as a middle-frequency signal induction core.

3. The AC-DC zero-flux current transformer according to claim 2, wherein The high-frequency AC line package T4 includes a high-frequency AC line package core C4, a high-frequency AC line package detection winding W4, and a fourth segment secondary winding W s ; The high-frequency AC wire package detection winding W4 is uniformly densely wound on the circumference of the high-frequency AC wire package core C4. The middle-frequency AC wire package core C3 is surrounded outside the high-frequency AC wire package core C4, and the middle-frequency AC wire package core C3 functions as a magnetic shield of the high-frequency AC wire package core C4 in addition to functioning as a middle-frequency signal induction core.

4. The AC-DC zero-flux current transformer according to claim 3, wherein The AC-DC zero-flux current transformer further comprises a primary winding W p The primary winding W p is a single-turn through conductor, which passes through the center apertures of the first DC magnetic modulation wire package T1, the second DC magnetic modulation wire package T2, the intermediate-frequency AC wire package T3, and the high-frequency compensation wire package T4. Secondary winding W s The first DC magnetic modulation wire package T1, the second DC magnetic modulation wire package T2, the intermediate frequency AC wire package T3 and the high frequency compensation wire package T4 are uniformly and densely wound on the overall wire package circumference.

5. The AC-DC zero-flux current transformer according to claim 1, wherein The circuit module comprises a self-oscillation generator, a low-pass filter, a band-pass filter, a high-pass filter, a middle-frequency signal amplifier, a high-frequency signal amplifier, a power amplifier and a load resistor. The self-oscillation generator comprises a first threshold voltage setting resistor R1, a second threshold voltage setting resistor R2, a first excitation current sampling resistor R3, a second excitation current sampling resistor R4 and a comparator.

6. The AC-DC zero-flux current transformer according to claim 5, wherein The first DC magnetic modulation wire package core C1 and the first DC magnetic modulation wire package excitation winding W1 form a non-linear inductor L1, the second DC magnetic modulation wire package core C2 and the second DC magnetic modulation wire package excitation winding W2 form a non-linear inductor L2, and the self-oscillation generator, the non-linear inductor L1 and the non-linear inductor L2 form a self-oscillation circuit.

7. The AC-DC zero-flux current transformer according to claim 6, wherein The negative input end of the comparator is connected with the non-polarity end of the first excitation winding W1 and the first excitation current sampling resistor R3, the other end of the first excitation current sampling resistor R3 is grounded, the positive input end of the comparator is connected with the one end of the first threshold voltage setting resistor R1 and the second threshold voltage setting resistor R2, the one end of the second threshold voltage setting resistor R2 is grounded, the other end of the second threshold voltage setting resistor R2 is connected with the polarity end of the first excitation winding W1, the output end of the comparator is connected with the non-polarity end of the second excitation winding W2, the polarity end of the second excitation winding W2 is connected with the one end of the second excitation current sampling resistor R4, the other end of the second excitation current sampling resistor R4 is grounded, the output end of the comparator is connected with the input end of the low-pass filter, the non-polarity end of the intermediate frequency AC line package detection winding W3 is connected with the band-pass filter, and the non-polarity end of the high-frequency AC line package detection winding W4 is connected with the high-pass filter; The output voltage signal of the low-pass filter is added to the output voltage of the band-pass filter and connected to the front end of the intermediate frequency signal amplifier; the voltage output end of the high-pass filter is connected to the front end of the high-frequency signal amplifier, the output voltage signal of the tail end is added to the output voltage of the high-frequency signal amplifier and connected to the front end of the power amplifier, and the tail end of the power amplifier is connected to the non-polar end of the secondary winding W s The load resistor is connected to the non-polar end of the secondary winding W s The non-polar end is connected.

8. The AC / DC zero flux current transformer according to claim 5, wherein, The self-oscillator is in different working states, the comparator output alternately changes two limit voltage ±U s , assuming that the initial time comparator positive input voltage U p > comparator negative input voltage U n , the comparator output positive limit voltage U s , and U p =U s *R1 / (R1+ R2), comparator output voltage U s acts on the nonlinear inductance L1 of the first DC magnetic modulation line package excitation winding W1, so that the excitation current I ex1 in the nonlinear inductance L1 increases from zero, the voltage U n on the excitation current sampling resistor R3 in the same loop will also increase, when its voltage increases to U n >U p , the comparator output flips to negative limit voltage ﹣U s , and U p =﹣U s *R1 / (R1+ R2), ﹣U s acts on the nonlinear inductance L1 of the excitation winding W1, so that the excitation current I ex1 begins to decrease to negative value, the voltage U n on the first excitation current sampling resistor R3 in the same loop will also decrease to negative value, when its voltage increases to U n <U p , the comparator will output positive limit voltage U s , due to the symmetry of the excitation performance of the core T1, the comparator will continuously output positive voltage U s and positive voltage ﹣U s with fixed period t1 and t2, that is, a square wave signal with period t1+t2 and amplitude U s .

9. The AC / DC zero flux current transformer according to claim 8, wherein, The self-excited oscillator, when a primary winding W p A symmetry of the core excitation performance is destroyed when a direct current flows through the primary winding, a bias proportional to the direct current is generated, and a positive limit voltage U s and a negative limit voltage -U s are output by the comparator, and a time inconsistency t1≠t2 between the positive limit voltage and the negative limit voltage is proportional to the direct current flowing through the primary winding. The comparator output square wave signal excites two first DC magnetic modulation line packages T1 and second DC magnetic modulation line packages T2 in reverse connection, and the same excitation generates magnetic fluxes with equal size and opposite directions in the first DC magnetic modulation line package T1 and the second DC magnetic modulation line package T2, which are offset to each other; The low-pass filter filters the high-frequency signal of the comparator output square wave voltage signal and directly converts it into a corresponding DC voltage signal; The band-pass filter filters the low-frequency and high-frequency parts of the AC voltage signal induced in the intermediate frequency AC line package detection winding W3, and outputs the amplified intermediate frequency AC voltage signal and DC voltage signal through the intermediate frequency amplifier; The high-pass filter filters the low-frequency part of the AC voltage signal induced in the high-frequency AC line package detection winding W4, and outputs the amplified high-frequency AC voltage signal through the high-frequency amplifier.

10. The AC / DC zero flux current transformer according to claim 9, wherein, The power amplifier further amplifies the voltage signal to drive the secondary winding and the load resistor to output the secondary current; The load resistor converts the current signal into a voltage signal; The second direct current magnetic modulation wire package exciting winding W s When the ripple current occurs, the ripple magnetic flux will generate an induced potential on the high-frequency AC wire package detection winding W4 of the high-frequency induction wire package, and drive the high-frequency signal amplifier and the power to generate an opposite current in the secondary winding, so as to offset the ripple and high-frequency harmonics until the ripple magnetic flux induced in the high-frequency AC wire package T4 is zero.

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