CN106992683B

CN106992683B - Voltage source and current source combined excitation non-contact conversion circuit

Info

Publication number: CN106992683B
Application number: CN201710147968.0A
Authority: CN
Inventors: 陈乾宏; 柯光洁; 张钰晟
Original assignee: Nanjing University of Aeronautics and Astronautics
Current assignee: Nanjing University of Aeronautics and Astronautics
Priority date: 2017-03-14
Filing date: 2017-03-14
Publication date: 2023-04-14
Anticipated expiration: 2037-03-14
Also published as: CN106992683A

Abstract

The invention discloses a voltage source and current source combined excitation non-contact conversion circuit, which comprises a first non-contact conversion module branch and a second non-contact conversion module branch, wherein the voltage source and the current source are combined and excited by utilizing the characteristic that the output characteristic of a non-contact converter under the excitation of a constant voltage source is inversely proportional to the primary and secondary coupling coefficients of a non-contact transformer and the output characteristic is directly proportional to the primary and secondary coupling coefficients of the non-contact transformer under the excitation of a constant current source, so that the change of the system output characteristic caused by the change of the coupling coefficient is eliminated or greatly reduced, the design of a post-stage circuit is facilitated, the energy transmission capability of a single non-contact power supply system under different use conditions is improved, and the fault tolerance and the applicability of the system are effectively improved.

Description

Voltage source and current source combined excitation non-contact conversion circuit

Technical Field

The invention discloses a non-contact converter excited by a voltage source and a current source in a composite mode, and belongs to the field of electric energy conversion.

Background

The non-contact power supply realizes wireless power supply by magnetic field coupling, namely, a non-contact transformer with completely separated primary and secondary sides is adopted to transmit electric energy by coupling of a high-frequency magnetic field, so that the primary side (power supply side) and the secondary side (power utilization side) are not physically connected in the energy transfer process. Compared with the traditional contact type power supply, the non-contact type power supply has the advantages of convenient and safe use, no spark and electric shock hazard, no dust accumulation and contact loss, no mechanical abrasion and corresponding maintenance problems, suitability for various severe weathers and environments, convenient realization of automatic power supply and good application prospect.

A complete wireless power transmission system consists of an electrically isolated primary side and a secondary side. The whole system comprises 3 core units: the high-frequency power conversion unit, the resonance compensation unit and the non-contact conversion unit. The non-contact conversion unit belongs to loose coupling, and has the defects of low coupling and large leakage inductance compared with a tight coupling transformer, if compensation is not carried out, a large amount of reactive power exists in the whole system, so that the transmission power and the whole efficiency of the system are greatly reduced, and the popularization and the application of a non-contact power supply technology are restricted. Meanwhile, because the primary side and the secondary side of the wireless power transmission system are completely separated, various working conditions such as the relative position change of the primary side and the secondary side and the change of the distance of the dead angle to the air gap exist in practical application, so that the circuit parameters of the transformer are greatly changed, and the working performance of the non-contact converter is influenced. Except for the parameter change of the non-contact transformer circuit caused by the relative position change of the primary side and the secondary side, the wireless power transmission system is similar to a common power supply, and can adapt to different application objects, load attributes and power levels.

The non-contact power supply system aims to reduce the power capacity requirement of a non-contact power supply system on a primary power supply side and improve the secondary side energy transmission capability. Usually, the primary and secondary sides of the non-contact transformer respectively adopt a capacitance compensation method to eliminate the influence of leakage inductance, that is, a resonance compensation unit in the wireless power transmission system. Chwei-Sen Wang; stielau, o.h.; covic, G.A., "Design connections for a connected electric field battery charger," Industrial Electronics, IEEE Transactions on, vol.52, no.5, pp.1308,1314, oct.2005, gave the characterization of the four basic compensation forms of the original side-by-side string parallel, string parallel, parallel and parallel strings. Other different compensation methods have been discussed in different articles. Generalizing the different compensation topologies can be found: 1. different compensation networks have different input and output characteristics, and the output characteristics of the non-contact converter are closely related to the coupling coefficient; 2. the value of the primary and secondary compensation capacitors is calculated under the condition that the primary and secondary air gaps of the non-contact transformer are fixed, and when the primary and secondary air gaps change or shift and dislocation occur, namely the coupling coefficient changes, the resonance frequency point can shift the original design reference point, so that the energy transmission capability and the applicability of the non-contact power supply system are greatly limited; 3. a compensation topology can provide limited voltage, current, and power to a powered device.

In order to improve the energy transmission capability of a non-contact power supply system under the condition of primary and secondary side dislocation offset, mickel Budhia, john T.Boys, grant A.Covic and Chang-Yu Huang, "Development of a Single-side Magnetic coupling for Electric Vehicle steering Systems" IEEE Transactions on Industrial Electronics, vol.60, no.1, january 2013 proposes to superpose a third winding (Q winding for short) superposed with a secondary side winding in the middle of two secondary side windings (DD winding for short) of a non-contact transformer, so as to reduce the lateral dislocation sensitivity of secondary output power and better solve the problem that the Magnetic Flux transmission capability of the transformer is influenced by the fact that the induction blind spot of 'completely offsetting' is positioned in the process of dislocation. However, the winding structure of the DDQ can only improve the output characteristics of the non-contact transformer under the condition of transverse dislocation, and the output characteristics of the winding structure of the DDQ still change greatly for the change of the vertical distance of the primary side and the secondary side (namely the change of the air gap). In consideration of the uncertainty of the air gap size and the misalignment condition before the primary side and the secondary side of the non-contact transformer in practical application, further research and study are still needed.

How to obtain a high-efficient reliable wireless power transmission circuit, namely can improve the output stability of the non-contact converter in the condition of air gap change and dislocation of the primary side and the secondary side of the transformer; the invention can also adapt to the power consumption requirements of different loads, and becomes the design key point of the invention.

Disclosure of Invention

The purpose of the invention is as follows: aiming at the prior art, the non-contact converter excited by the voltage source and the current source in a composite mode is provided, and the stability of the output characteristic under the condition of variable coupling coefficients is effectively improved.

The technical scheme is as follows: a voltage source and current source combined excitation non-contact conversion circuit comprises a first non-contact conversion module branch and a second non-contact conversion module branch; the first non-contact conversion module branch is formed by sequentially connecting a first input source, a first primary side compensation network, a first non-contact transformer, a first secondary side compensation network, a first rectification circuit and a first filter network in series, the second non-contact conversion module branch is formed by sequentially connecting a second input source, a second primary side compensation network, a second non-contact transformer, a second secondary side compensation network, a second rectification circuit and a second filter network in series, and the output of the first filter network and the output of the second filter network are connected in series or in parallel and then connected to two ends of a load; for the first non-contact transformer and the second non-contact transformer, the current flowing into the primary winding of one non-contact transformer is a constant quantity, and the current flowing into the primary winding of the other non-contact transformer is a variable quantity which is changed along with the load and the coupling coefficient.

Furthermore, the constant current flowing into the primary winding of one of the non-contact transformers is realized by an LC conversion network or a control circuit.

Further, the first input source and the second input source are obtained by converting an alternating current constant voltage source or an alternating current constant current source, or a direct current input source and an inverter circuit.

Further, the first primary side compensation network and the second primary side compensation network, and the first secondary side compensation network and the second secondary side compensation network in the two non-contact conversion modules are series single-capacitor compensation, parallel single-capacitor compensation, series-parallel capacitor compensation, parallel-series capacitor compensation, series/parallel LC network compensation, LCL form compensation, LCC form compensation, or a combination form of any structure of the above.

Furthermore, secondary circuits of the two non-contact conversion modules are shared to form a non-contact transformer structure with a primary double-winding secondary single winding.

Further, the winding structure of the first non-contact transformer and the second non-contact transformer is a single coil structure, a double coil structure or a multi-coil structure, and the primary side magnetic core and/or the secondary side magnetic core are U-shaped, I-shaped, edge-expanded type with the bottoms of two side columns expanding outwards along the side edges, cross-shaped or a combination of the shapes.

Has the advantages that: compared with the prior art, the voltage source and current source compound excitation non-contact conversion circuit has the main technical characteristics that the output characteristic of a non-contact converter under the excitation of a constant voltage source is inversely proportional to the primary and secondary coupling coefficients (mutual inductance) of a non-contact transformer, and the output characteristic is proportional to the primary and secondary coupling coefficients (mutual inductance) of the non-contact transformer under the excitation of a constant current source, so that the voltage source and the current source are compounded and excited to be combined for output, the change of the system output characteristic caused by the change of the coupling coefficient (mutual inductance) is eliminated or greatly reduced, the design of a post-stage circuit is facilitated, the energy transmission capability of a single non-contact power supply system under different use conditions is improved, and the fault tolerance and the applicability of the system are effectively improved.

Drawings

Fig. 1 is a conventional single power supply-driven non-contact conversion circuit.

Fig. 2 is a general circuit of an ac/ac non-contact conversion unit with single power supply excitation, fig. 2 (a) is a schematic diagram of a single voltage power supply excitation and a corresponding compensation network circuit, and fig. 2 (b) is a schematic diagram of a single current power supply excitation and a corresponding compensation network circuit.

Fig. 3 is a schematic diagram of two-terminal network equivalent circuits of different ports of the single-power-supply-excited ac/ac non-contact conversion unit shown in fig. 2, fig. 3 (a) is a schematic diagram of an equivalent two-terminal network of an input source and a primary side compensation network, fig. 3 (b) is a schematic diagram of a universal equivalent two-terminal network of the input source and the primary side compensation network, fig. 3 (c) is a schematic diagram of an equivalent impedance circuit on the right side of a primary side input port of a non-contact transformer, fig. 3 (d) is a two-terminal network on the left side of an output port of the non-contact transformer obtained based on a mutual inductance model of the non-contact transformer, and fig. 3 (e) is a schematic diagram of a universal current-voltage-current conversion circuit.

Fig. 4 (a) is a schematic circuit diagram of a circuit structure of a voltage source and current source compound excitation contactless conversion circuit according to an embodiment of the present invention, and fig. 4 (b), fig. 4 (c), and fig. 4 (d) are all equivalent conversion circuits of fig. 4 (a).

Fig. 5 is a schematic circuit diagram of a second embodiment of the voltage source and current source compound excitation contactless conversion circuit of the present invention.

Fig. 6 (a) is a schematic diagram of a three-circuit structure of an embodiment of the voltage source and current source compound excitation contactless conversion circuit of the present invention, and fig. 6 (b) is a fundamental wave equivalent circuit of fig. 6 (a).

FIG. 7 is a schematic diagram of a fourth circuit of the voltage source and current source combined excitation contactless conversion circuit according to the embodiment of the present invention.

Fig. 8 is a five-circuit schematic diagram of the voltage source and current source combined excitation non-contact conversion circuit embodiment of the invention.

Fig. 9 is a six-circuit schematic diagram of an embodiment of a voltage source and current source compound excitation non-contact conversion circuit of the invention.

FIG. 10 is a schematic circuit diagram of a voltage source and current source combined excitation contactless conversion circuit according to an embodiment of the present invention.

Fig. 11 (a) is a structural diagram of a non-contact transformer used in a first test example of the voltage source and current source compound excitation non-contact conversion circuit of the present invention, fig. 11 (b) is a simulation result of the output voltage gain under a heavy load condition of the test example, and fig. 11 (c) is a simulation result of the output voltage gain under a light load condition of the test example.

FIG. 12 is a simulation result of the output voltage of the voltage source and current source combined excitation non-contact transformation circuit test example two under different load conditions.

Fig. 13 is a schematic diagram of a voltage source and current source compound excitation non-contact conversion circuit structure of the present invention.

Detailed Description

The invention is further explained below with reference to the drawings.

Fig. 1 is a conventional single-power-supply-excited non-contact conversion circuit, which comprises an inverter bridge, a non-contact transformer, a primary and secondary side compensation network and an output rectification filter part. The inverter bridge has many optional circuits including push-pull, half-bridge, full-bridge, etc. and may be divided into voltage source fed inverter bridge and current source fed inverter bridge based on the input power source characteristic. To highlight the design emphasis of the present invention, the ac/ac non-contact transformation unit in the dotted line frame in fig. 1 is taken as the research object of the present invention. The output of the inverter bridge is equivalent to an alternating current source, and the rectifying and filtering circuit is equivalent to a load resistor.

Fig. 2 is a general circuit of an ac/ac non-contact conversion unit with single power supply excitation, which includes an input ac source 1, a primary side compensation network 2, a non-contact transformer 3, a secondary side compensation network 4, and an equivalent load 5. According to the different characteristics of the input power, the non-contact converter can be divided into a voltage source input type non-contact converter and a current source input type non-contact converter, and the different input source characteristics need to correspond to different compensation topologies, as shown in fig. 2 (a) and fig. 2 (b), respectively. The compensation network is composed of inductance, capacitance and other resonance elements, wherein Z _P1 、Z _P2 、Z _S1 、Z _S2 The primary side compensation T network and the secondary side compensation T network series compensation reactance parameters G of the voltage source input type non-contact converter respectively _P 、G _S Parallel compensation conductance parameters of a primary side compensation T network and a secondary side compensation T network of the voltage source input type non-contact converter are respectively set; g _P1 、G _P2 、G _S1 、G _S2 Parallel compensation electricity of primary and secondary side compensation pi network of current source input type non-contact converterParameter of conductance, Z _P 、Z _S And the series compensation reactance parameters are respectively the primary side compensation pi network and the secondary side compensation pi network of the current source input type non-contact converter. When the series compensation reactance parameter is zero, the corresponding branch is short-circuited; and when the parallel compensation conductance parameter is zero, the corresponding branch is disconnected. Therefore, by changing the values of the parameters of the compensation T network and the pi network, different compensation modes can be realized.

Fig. 3 is a two-terminal network equivalent circuit of different ports of the single-power-supply-excited ac/ac non-contact conversion unit shown in fig. 2. Based on thevenin's theorem and norton's theorem, the input ac source 1 and the primary side compensation network 2 in fig. 2 can be equivalent to a two-terminal network with an AB as a port, and the external characteristics of the equivalent two-terminal network are the same as the external characteristics of the original circuit topology output. Considering the different possibilities of taking values of the primary compensation network parameters, there are four possible equivalent circuit forms shown in fig. 2 (a), where v _e1 、v _e2 、i _e1 、i _e2 Being an equivalent controlled source, Z _ev 、Z _ei 、G _ev 、G _ei The source impedance is divided for the left side two terminal network of AB. According to thevenin equivalence, a controlled voltage source is connected with an impedance in series, so that the controlled voltage source is equivalent to a controlled current source connected with an impedance in parallel, namely, the diagram (1) and the diagram (4) in the diagram (a) in the diagram 2 can be considered to be equivalent; according to the characteristics of the voltage source and the current source, the parallel impedance of the voltage source is equivalent to the voltage source, and the series impedance of the current source is equivalent to the current source. The input ac source 1 and the primary compensation network 2 of the single-source-driven contactless converter can thus be further equivalent to two-terminal networks as shown in fig. 3 (b), in which the controlled voltage source v is _e Controlled current source i _e Related to the parameters and working frequency of the resonant elements such as inductance and capacitance in the input AC power supply and compensation network, except for the source impedance Z _e The parameters of the resonant elements such as inductance and capacitance in the compensation network and the working frequency are related, and the parameters are not related to the circuit parameters of the non-contact transformer.

Based on the series-parallel relationship between the mutual inductance model of the non-contact transformer and the impedance, the non-contact transformer 3, the secondary compensation network 4 and the load resistor 5 in the right circuit of the port AB in fig. 2 can be equivalent to a two-terminal network shown in fig. 3 (c), wherein Z is _TS Is the non-contact transformer secondary loop impedance. Also based on the mutual inductance model of the contactless transformer, a two-terminal network on the left side of the CD port can be obtained as shown in fig. 3 (d). And the two-end network on the right side of the CD port is a passive impedance connection network which is formed by connecting the inductor, the capacitor and the load resistor of the secondary side resonance network in series and parallel, and is irrelevant to the circuit parameters of the non-contact transformer.

Based on the two-terminal network equivalent circuit of different ports of the single-power-supply excitation ac/ac non-contact conversion unit shown in fig. 3, the output voltage at two ends of the load resistor can be obtained through solving. When the left two-terminal network of the AB port is equivalent to a controlled voltage source connected in series to divide the source impedance, the output voltage across the load can be expressed as:

and H is the voltage division coefficient of the load resistor on the passive network at the two ends of the right side of the CD. As can be seen from the foregoing analysis, Z in the formula (1) _TS 、H、Z _e 、v _e Are independent of non-contact transformer parameters, so when j ω L _P +Z _e When the inductance is not less than 0, the output voltage varies inversely with the mutual inductance of the primary side and the secondary side of the non-contact transformer, and the current flowing into the primary side winding varies with the mutual inductance of the non-contact transformer and the load variation.

When the two-terminal network on the left side of the AB port is equivalent to a controlled current source, that is, when the current flowing into the primary winding is a constant value, the output voltage across the load can be expressed as:

it can be seen from the formula (2) that when the input alternating current power supply (1) and the primary side compensation network (2) are equivalent to a controlled current source, the output voltage changes linearly with the mutual inductance of the primary side and the secondary side of the non-contact transformer. By combining the formula (1) and the formula (2), it can be found that when the input port of the non-contact transformer is respectively used as the input of a voltage source and a current source, the voltages at two ends of the load resistor of the non-contact transformer respectively show opposite change trends along with the mutual inductance change of the non-contact transformer, namely when the non-contact transformer is used as the input of the voltage source, the output voltage is gradually changed along with the mutual inductance M; and when the non-contact transformer is used as the current source input, the output voltage is changed along with the mutual inductance M in an increasing mode.

Based on such circuit characteristics, the operation principle of the present invention can be explained, and thus the technical solution and the embodiment of the present invention are introduced.

It should be noted that the current source in the non-contact converter excited by the voltage source and the current source in the invention refers to that the current flowing into the primary winding of the non-contact transformer is a constant current source, and can be obtained by exciting the primary winding of the series transformer for the actual current source, or exciting the series LC topology transformation through the actual external voltage source, as shown in the left circuit of fig. 3 (e), or controlling the current flowing into the primary winding to be a constant quantity through the control circuit; the voltage source in the present invention can be an actual voltage source, or can be obtained by an actual external current source to excite the parallel LC topology transformation, as shown in the right circuit of fig. 3 (e).

The first embodiment is as follows:

fig. 4 is a circuit diagram showing a first embodiment of the contactless converter driven by a voltage source and a current source in a composite mode. The non-contact converter circuit shown in fig. 4 (a) is a DC-DC converter circuit, and includes two non-contact converters, in which a branch 1 and a branch 2 are connected in parallel at a DC input side and connected in series at a DC output side. Each path of non-contact conversion module comprises a direct current input voltage source 1_1, an inverter 1_2, a primary side compensation network 2, a non-contact transformer 3, a secondary side compensation network 4, a rectification circuit 5_1, a filter circuit 5_2 and a load resistor 5_3, wherein the direct current input voltage source 1_1 and the load resistor 5_3 are shared by two paths. In order to distinguish the branch 1 from the branch 2, the reference numeral "F" is used to denote the branch 1, the reference numeral "S" is used to denote the branch 2, the first subscript "F" or "S" of the circuit components in the two non-contact conversion modules is used to distinguish the branch 1 from the branch 2, and the second subscript is used to distinguish the same components in each branch. In the circuit shown in FIG. 4 (a), U _in For a DC input voltage source, S _x1 ～S _x4 Is a primary side inversion full-bridge switching tube, C _xP Compensating the capacitance for the primary side, C _xS Compensating the capacitance for the secondary side，L _xP Self-inductance of primary winding of non-contact transformer, L _xS Self-inductance of secondary winding of non-contact transformer, M _x Mutual inductance of primary and secondary windings of non-contact transformer, L _xq To compensate for inductance in series, D _x1 ～D _x4 Is a secondary side rectifier diode, C _xf Is a filter capacitor, R _L For load resistance, x in the subscripts represents "F" or "S".

The output of the DC input voltage source 1_1 and the inverter circuit F1_2 is an AC square wave, so the left circuit of the port FaFb can be equivalent to a square wave AC input voltage source u _Fab (ii) a Similarly, the left circuit of the SaSb port can be equivalent to a square wave AC input voltage source u _Sab (ii) a After being rectified by the two non-contact converters, the direct current sides are connected in series, the two paths share the same load, and based on the basic theorem of the circuit, the load resistor 5_3 can be equivalent to two resistors R _FL 、R _SL The two non-contact conversion modules are connected in series, so that the two non-contact conversion modules can be disconnected at the source side and the load side, and an equivalent rear circuit is shown in fig. 4 (b). In order to improve the efficiency of the non-contact converter, the converter is generally designed to work near a resonance frequency point, the resonance inductance current is approximate to sine, and then a fundamental wave approximate analysis method can be adopted to approximately replace the variables in the resonance network with fundamental wave components. When the rectifier bridge is continuously conducted, the voltage and the current of the middle point of the bridge arm are always in the same phase, and the secondary side rectifier bridge 5_1, the filter link 5_2 and the load 5_3 can be equivalent to a linear resistor R _E . Based on the fundamental analysis, the circuit topology of the embodiment shown in FIG. 4 (a) can be further equivalent to that shown in FIG. 4 (c), where u is _xs 、i _xs 、u _xo 、i _xo The fundamental components of the input voltage, current, output voltage, current, respectively, x in the subscript denotes "F" or "S". As can be seen from fig. 4 (c), each branch line constituent unit corresponds one-to-one to fig. 2 (a).

The primary side compensation network F2 of the branch 1 and the primary side self-inductance of the non-contact transformer F3 form an LCL compensation topology, and L is designed _Fq Primary side self-inductance L of non-contact transformer F3 _FP Equal to, C _FP And L _FP The resonance and secondary side compensation network F4 is single-capacitor series compensationCapacitor C _FS Secondary side self-inductance L of non-contact transformer F3 _FS And (4) resonating. At the resonant frequency point, the equivalent primary side input voltage source F1 based on thevenin and the primary side compensation network F3 are equivalent to a controlled current source, as shown in fig. 4 (d), at this time, the current flowing into the primary side winding of the branch 1 is only excited by the actual voltage source and the resonant inductor L _Fq In relation to the inductive reactance of when the voltage source excites U _in When the current flowing into the primary winding of the branch circuit 1 is constant, the current does not change along with the position change of the primary side and the secondary side of the non-contact transformer and the load change. The primary side compensation network S2 of the branch circuit 2 is series capacitance compensation and compensation capacitance C _SP Self-inductance L of primary side of non-contact transformer S3 _SP The secondary self-inductance of the resonant, non-contact transformer S3 and the secondary compensation network S4 form an LCL compensation topology, and L is designed _Sq Secondary side self-inductance L of non-contact transformer S3 _SS Equal, C _SS And L _SS And (5) resonating. And a network at the port AB of the branch 2 is an input voltage source series resonant impedance, when the coupling coefficient of the transformer changes or the load changes, the input impedance equivalent to the primary side changes, and the current flowing into the primary side winding of the non-contact transformer of the branch 2 also changes. Therefore, the input ports of the non-contact transformers of the two non-contact conversion modules are respectively the input of a voltage source and a current source. The output characteristics of the two non-contact conversion modules are discussed below based on a mutual inductance model of the transformer. The resonance inductance and capacitance meet:

wherein ω is ₀ Is the resonant frequency. The input voltage and current of the non-contact converter of the branch 1 shown in fig. 4 (c) satisfy the following requirements:

wherein Z _Fr The reflected impedance of the secondary side of the non-contact transformer of branch 1,

simplifying equation (4) and fully compensating for the input impedance Z of branch 1 _Fin And the effective value U of the output voltage _FOS Respectively as follows:

wherein U is _Fs Is the effective value of the fundamental wave of the input voltage. As can be seen from equation (5), the output voltage U _FOS Mutual inductance M between primary side and secondary side of non-contact transformer with branch 1 _F Positive correlation is achieved, and the output voltage is independent of the load resistance value; the input impedance is always pure impedance at the complete compensation frequency point, and the impedance is related to the load resistance and the mutual inductance.

In the same way, the input impedance Z of branch 2 at the complete compensation point can be determined _Sin And the effective value U of the output voltage _SOS Respectively as follows:

wherein U is _Ss The fundamental effective value of the input voltage of branch 2. As can be seen from equation (6), the output voltage U _SOS Mutual inductance M between primary side and secondary side of non-contact transformer of branch 2 _S Inversely proportional and the output voltage is independent of the load resistance value; the input impedance is always pure impedance at the complete compensation frequency point, and the impedance is related to the load resistance and the mutual inductance. By combining the formula (5) and the formula (6), the total output voltage gain U is obtained _o Comprises the following steps:

in the wireless charging system, the primary side of a non-contact transformer is generally fixed, the secondary side of the non-contact transformer is movable, when the primary side and the secondary side of the non-contact transformer move relatively, the secondary side of the two non-contact transformers in the embodiment moves in the same direction relative to the primary side, the mutual inductance M of the two transformers changes in the same trend, and a combination formula (7) shows that the output voltage of the first embodiment of the invention is not monotonous along with the change of the mutual inductance M, and through reasonably designing the parameters of the transformers, the mutual compensation of the output voltages of two non-contact transformation modules can be effectively realized, and the stability of the total output voltage of the system under the condition of variable coupling coefficients is improved; meanwhile, as can be seen from the formula (7), the output voltage of the first embodiment of the invention is independent of the load resistance under the complete compensation condition, that is, the output voltage can be constant under the variable load condition; by combining the two non-contact conversion modules in the formulas (5) and (6) with the input impedance expression, it can be found that the input impedance of the first embodiment of the present invention is always pure resistive under the condition of complete compensation, that is, the working frequency is slightly greater than the complete compensation frequency to ensure that the two non-contact conversion modules always work in a weak inductance region, thereby implementing ZVS of the switching tube and improving the system efficiency.

When deviating from the complete compensation point, if the air gaps of the primary and secondary sides of the contactless transformer in branch 1 and branch 2 become smaller at the same time, M _F ，M _S At the same time become larger, at which time L _FP 、L _FS 、L _SP 、L _SS The constant gain points of the branch 1 and the branch 2 are changed along with the change, the voltage gain of the branch 1 is increased, the voltage gain of the branch 2 is reduced, and the overall voltage gain can be compensated if the working frequency also moves to the low frequency; if the air gaps of the primary and secondary sides of the non-contact transformer in branch 1 and branch 2 become larger at the same time, M _F ，M _S At the same time become smaller, at this time L _FP 、L _FS 、L _SP 、L _SS The constant gain points of the branch 1 and the branch 2 are changed along with the change, the voltage gain of the branch 1 is decreased, the voltage gain of the branch 2 is increased, and the whole voltage gain can be compensated if the working frequency is also moved to high frequency.

In order to make the output voltage gain adapt to the mutual inductance change in a wider range, the mutual inductance value corresponding to the output voltage extreme point is required to be ensured to be in a working range. From the mathematical function characteristic of the formula (7), two non-contact transformer parameters need to be designed to satisfy the formula (8) at the complete compensation point.

The winding structures of the non-contact transformer F3 and the second non-contact transformer S3 are a single coil structure, a double coil structure or a multi-coil structure, and the primary side magnetic core and/or the secondary side magnetic core are U-shaped, I-shaped, edge-expanded type with the bottoms of two side columns expanding outwards along the side edges, cross-shaped or the combination of the shapes.

The second embodiment:

fig. 5 is a circuit diagram showing a non-contact converter driven by a voltage source and a current source in a compound mode according to a second embodiment of the invention. In the two-way non-contact converter shown in fig. 5, branch 1 and branch 2 are connected in series on the dc output side. The branch 1 consists of an alternating current input current source F1, a primary side compensation network F2, a non-contact transformer F3, a secondary side compensation network F4, a rectification circuit F5_1, a filter circuit F5_2 and a load resistor 5_3, wherein a direct current input voltage source 1_1 and the load resistor 5_3 are in common use in two ways; the branch 2 is composed of a direct current input voltage source S1_1, an inverter S1_2, a primary side compensation network S2, a non-contact transformer S3, a secondary side compensation network S4, a rectification circuit S5_1, a filter circuit S5_2 and a load resistor 5_3. Comparing fig. 5 with fig. 4 (a), it can be seen that the difference between the second embodiment and the first embodiment is the input source, in the first embodiment shown in fig. 4 (a), the input current source of the primary port of the contactless transformer of the branch 1 is obtained by equivalent transformation of a dc input voltage source 1_1, an inverter F2, and a primary compensation network F3; in the second embodiment shown in fig. 5, the input current source of the primary port of the non-contact transformer in the branch 1 is the external dc excitation source F1. Based on thevenin equivalent, in the second embodiment, the ac input current source satisfies:

the parameters on the right of the middle sign in equation (9) are the circuit parameters in the first embodiment shown in fig. 4. When the equation (9) is satisfied, it can be known from the two-port equivalent model that the second embodiment and the first embodiment have the same output characteristics, and the description thereof is omitted here.

Example three:

FIG. 6 shows a non-contact converter excited by a combination of a voltage source and a current source according to the present inventionThe circuit configuration of the third embodiment. In the two-way non-contact converter shown in fig. 6, the branch 1 and the branch 2 are connected in parallel at the dc input side and the dc output side. Each path of non-contact conversion module comprises a direct current input voltage source 1_1, an inverter 1_2, a primary side compensation network 2, a non-contact transformer 3, a secondary side compensation network 4, a rectification circuit 5_1, a filter circuit 5_2 and a load resistor 5_3, wherein the direct current input voltage source 1_1 and the load resistor 5_3 are shared by two paths. In order to distinguish the branch 1 from the branch 2, the branch 1 is represented by "F", the branch 2 is represented by "S", the first subscript "F" or "S" of the circuit components in the two non-contact conversion modules is used for distinguishing the branch 1 from the branch 2, and the second subscript is used for distinguishing the same components in each branch. In the circuit shown in FIG. 6, U _in For a DC input voltage source, S _x1 ～S _x4 Is a primary side inversion full-bridge switching tube, C _xP Compensating the capacitance for the primary side, C _xS Compensating the capacitance for the secondary side, L _xP Self-inductance of primary winding of non-contact transformer, L _xS Self-inductance of secondary winding of non-contact transformer, M _x Mutual inductance of primary and secondary windings of a non-contact transformer, L _xq Compensating the inductance in series, D _x1 ～D _x4 Is a secondary side rectifier diode, C _xf Is a filter capacitor, R _L For load resistance, x in the subscript represents "F" or "S".

Similar to the analysis method of the first embodiment, based on the fundamental wave equivalence, FIG. 6 (a) can be equivalent to FIG. 6 (b), in which u is _xs 、i _xs 、u _xo 、i _xo The fundamental components of the input voltage, current, output voltage, current, respectively, x in the subscript denotes "F" or "S". The primary side compensation network F2 of the branch circuit 1 is an LC network, so that the input voltage source is converted into an input current source, and a capacitor C _FP And L _Fq The resonance secondary side compensation network F4 is a single-capacitor parallel compensation and parallel compensation capacitor C _FS Secondary side self-inductance L of non-contact transformer F3 _FS And (4) resonating. At the resonant frequency point, based on the fact that the Thevenin equivalent primary side input voltage source F1 and the primary side compensation network F3 are equivalent to a controlled current source, the current flowing into the primary side winding of the branch circuit 1 is only excited by the actual voltage source and the resonant inductor L _Fq When the voltage source excites U _in When the current flowing into the primary winding of the branch circuit 1 is constant, the current does not change along with the position change of the primary side and the secondary side of the non-contact transformer and the load change. The primary side compensation network S2 of the branch circuit 2 is series capacitance compensation and compensation capacitor C _SP Self-inductance L of primary side of non-contact transformer S3 _SP Series compensation capacitor C of resonance secondary side compensation network S4 _SS Secondary side self-inductance L of non-contact transformer S3 _SS And (4) resonating. And a network at the port AB of the branch 2 is an input voltage source series resonant impedance, when the coupling coefficient of the transformer changes or the load changes, the input impedance equivalent to the primary side changes, and the current flowing into the primary side winding of the non-contact transformer of the branch 2 also changes. Therefore, the input ports of the non-contact transformers of the two non-contact conversion modules are respectively the input of the voltage source and the current source.

Based on the mutual inductance model of the transformer, the output characteristics of the two non-contact conversion modules can be obtained. The input voltage and the current of the branch circuit 1 non-contact converter and the output voltage meet the following requirements:

wherein, ω is ₀ To the resonant frequency, Z _Fr The reflected impedance of the secondary side of the non-contact transformer of branch 1,

the input voltage and the current of the branch 2 non-contact converter and the output voltage meet the following requirements:

wherein Z _Sr The reflected impedance of the secondary side of the non-contact transformer of branch 2,

simplifying equations (10) and (11) respectively can obtain the outputs of branch 1 and branch 2 when fully compensatedEffective value of current I _FOS 、I _SOS Respectively as follows:

wherein U is _Fs 、U _Ss The fundamental wave effective values of the two paths of input voltage are respectively. As can be seen from equation (12), the output current I _FOS Mutual inductance M between primary side and secondary side of non-contact transformer with branch 1 _F Positive correlation is achieved, and the output current is independent of the load resistance value; output current I _SOS Mutual inductance M between primary side and secondary side of non-contact transformer of branch 2 _S Inversely proportional and independent of the load resistance value. In the embodiment, the total current output by the three non-contact converters in parallel is as follows:

in the embodiment, the secondary sides of the two non-contact transformers have the same movement direction relative to the primary side, the mutual inductance M of the two transformers has the same variation trend, and the combination formula (13) shows that the output current of the third embodiment of the invention is non-monotonous along with the variation of the mutual inductance M, and through reasonably designing the transformer parameters, the mutual compensation of the output currents of the two non-contact transformation modules can be effectively realized, and the stability of the total output current of the system under the condition of variable coupling coefficients is improved; meanwhile, as can be seen from equation (13), the output current of the third embodiment of the present invention is independent of the load resistance under the complete compensation condition, that is, the output current can be constant under the variable load condition.

In order to make the output current gain adapt to the mutual inductance change in a wider range, the mutual inductance value corresponding to the output current extreme point is required to be ensured to be in a working interval. According to the mathematical function characteristic of the formula (13), two non-contact transformer parameters need to be designed to satisfy the formula (14) at a complete compensation point.

Example four:

FIG. 7 showsThe circuit structure diagram of the fourth embodiment of the non-contact converter excited by the voltage source and the current source in a composite mode is shown. In the two-way non-contact converter shown in fig. 7, branch 1 and branch 2 are connected in parallel on the dc output side. The branch circuit 1 consists of a direct current input voltage source F1_1, an inverter F1_2, a primary side compensation network F2, a non-contact transformer F3, a secondary side compensation network F4, a rectification circuit F5_1, a filter circuit F5_2 and a load resistor 5_3, wherein the direct current input voltage source 1_1 and the load resistor 5_3 are in two-way common use; the branch 2 is composed of an alternating current input current source S1, a primary side compensation network S2, a non-contact transformer S3, a secondary side compensation network S4, a rectification circuit S5_1, a filter circuit S5_2 and a load resistor 5_3. In the circuit shown in FIG. 7, U _in For direct current input of voltage source, i _in For an AC input current source, S _F1 ～S _F4 Is a primary side inversion full-bridge switching tube, C _xP Compensating capacitance, C, for the primary side _xS Compensating the capacitance for the secondary side, L _xP Self-inductance of primary winding of non-contact transformer, L _xS Self-inductance of secondary winding of non-contact transformer, M _x Mutual inductance of primary and secondary windings of a non-contact transformer, L _xq To compensate for inductance in series, D _x1 ～D _x4 Is a secondary side rectifier diode, C _xf Is a filter capacitor, R _L For load resistance, x in the subscript represents "F" or "S".

The primary side compensation network F2 of the branch circuit 1 is a single-capacitor series compensation capacitor C _FP Primary side self-inductance L of non-contact transformer F3 _FP The resonance and secondary side compensation network F4 is also a single-capacitor series compensation capacitor C _FS Secondary side self-inductance L of non-contact transformer F3 _FS And (4) resonating. The primary side compensation network S2 of the branch circuit 2 is series capacitance compensation and compensation capacitor C _SP Self-inductance L of primary side of non-contact transformer S3 _SP Secondary side self-inductance L of resonant, non-contact transformer S3 _SS An LCL compensation network is formed with the secondary side compensation network S4 to realize voltage-current conversion and design a resonant inductor L _Sq Secondary side self-inductance L of non-contact transformer S3 _SS Equal, capacitance C _FP And L _Fq And (5) resonating. As can be seen from FIG. 7, the two-terminal AB network of the branch 1 port is an input voltage source series resonance impedance, and the 2 end of the branchThe port AB two-terminal network is an input current source series resonance impedance and can be equivalent to an input current source. Therefore, the input ports of the non-contact transformers of the two non-contact conversion modules are respectively the input of a voltage source and a current source.

By adopting a fundamental wave analysis method and based on a mutual inductance model of the transformer, the output characteristics of the two non-contact conversion modules can be obtained. The input voltage and the current of the branch circuit 1 non-contact converter and the output voltage meet the following requirements:

wherein omega ₀ To the resonant frequency, Z _Fr The reflected impedance of the secondary side of the non-contact transformer of branch 1,

the input voltage and the current of the branch circuit 2 non-contact converter satisfy the following requirements:

the equations (15) and (16) are simplified respectively to obtain the effective values I of the output currents of the

branch circuits

1 and 2 when the compensation is completed _FOS 、I _SOS Input impedance Z _Fin 、Z _Sin Respectively as follows:

wherein U is _Fs 、I _Ss The fundamental wave effective values of the two paths of input voltage and the input current are respectively. As can be seen from equation (17), the output current I _FOS Mutual inductance M between primary side and secondary side of non-contact transformer with branch 1 _F Inversely proportional, and the output current is independent of the load resistance value; output current I _SOS Mutual inductance M between primary side and secondary side of non-contact transformer of branch 2 _S Proportional to the load resistance value and independent of the load resistance value; the input impedance of the two non-contact converters is always pure impedance at a complete compensation frequency point, and the impedance is related to the load resistance and the mutual inductance. In the embodiment, the total current output by the four non-contact converters in parallel is as follows:

in the embodiment, the secondary sides of the two non-contact transformers have the same movement direction relative to the primary side, the mutual inductance M of the two transformers has the same variation trend, and the combination formula (18) shows that the output current of the fourth embodiment of the invention is non-monotonous along with the variation of the mutual inductance M, and through reasonably designing the transformer parameters, the mutual compensation of the output currents of the two non-contact transformation modules can be effectively realized, and the stability of the total output current of the system under the condition of variable coupling coefficients is improved; meanwhile, as can be seen from the equation (18), the output current of the fourth embodiment of the present invention is independent of the load resistance under the complete compensation condition, that is, the output voltage can be constant under the variable load condition; from the expression of the input impedance of the two non-contact transformation modules in the formula (17), it can be found that the input impedance of the fourth embodiment of the present invention is always pure resistance under the condition of complete compensation, that is, the working frequency is slightly greater than the complete compensation frequency to ensure that the two non-contact transformation modules always work in a weak inductance region, thereby implementing ZVS of the switching tube and improving the system efficiency.

In order to adapt the output current gain to the mutual inductance change in a wider range, the mutual inductance value corresponding to the output current extreme point is required to be ensured within a working interval. From the mathematical function characteristic of the equation (18), two non-contact transformer parameters need to be designed to satisfy the equation (19) at the complete compensation point.

Example five:

FIG. 8 shows the voltages of the present inventionThe circuit structure diagram of the fifth embodiment of the non-contact converter excited by the source and the current source in a composite mode. In the two-way non-contact converter shown in fig. 8, the branch 1 and the branch 2 are connected in parallel on the dc output side. The branch 1 consists of an alternating current input current source F1, a primary side compensation network F2, a non-contact transformer F3, a secondary side compensation network F4, a rectification circuit F5_1, a filter circuit F5_2 and a load resistor 5_3; the branch 2 is composed of an alternating current input current source S1, a primary side compensation network S2, a non-contact transformer S3, a secondary side compensation network S4, a rectification circuit S5_1, a filter circuit S5_2 and a load resistor 5_3. In the circuit shown in FIG. 8, i _xin Is an AC input current source, C _xP Compensating capacitance, C, for the primary side _xS Compensating the capacitance for the secondary side, L _xP Self-inductance of primary winding of non-contact transformer, L _xS Self-inductance of secondary winding of non-contact transformer, M _x Mutual inductance of primary and secondary windings of a non-contact transformer, D _x1 ～D _x4 Is a secondary side rectifier diode, L _xf Is a filter inductor, C _xf Is a filter capacitor, R _L For load resistance, x in the subscript represents "F" or "S".

The primary side compensation network F2 of the branch 1 is a single-capacitor parallel compensation and parallel compensation capacitor C _FP Primary side self-inductance L of non-contact transformer F3 _FP The resonance secondary side compensation network F4 is a single-capacitor series compensation capacitor C _FS Secondary side self-inductance L of non-contact transformer F3 _FS And resonance, based on Thevenin equivalence and Noton equivalence, a parallel impedance of a current source can be equivalently transformed into a series impedance of a voltage source, and a circuit on the left side of the port AB of the branch 1 can be equivalently a two-terminal network of a controlled voltage source. The primary side compensation network S2 of the branch circuit 2 is series capacitance compensation and compensation capacitor C _SP Primary side self-inductance L of non-contact transformer S3 _SP The resonance secondary side compensation network S4 is a single-capacitor parallel compensation and parallel compensation capacitor C _SS Secondary side self-inductance L of non-contact transformer S3 _SS And a two-terminal network of the port AB of the branch 2 is an input current source series resonance impedance and can be equivalent to an input current source. Therefore, the input ports of the non-contact transformers of the two non-contact conversion modules are respectively the input of the voltage source and the current source.

By adopting a fundamental wave analysis method and based on a mutual inductance model of the transformer, the output characteristics of the two non-contact conversion modules can be obtained. The input voltage, the current of branch 1 non-contact converter, output voltage satisfies:

wherein ω is ₀ Is the resonant frequency, Z _Fr The reflected impedance of the secondary side of the non-contact transformer of branch 1,

the equations (20) and (21) are respectively simplified to obtain the effective values I of the output currents of the

branch circuits

1 and 2 when the compensation is completed _FOS 、I _SOS Respectively as follows:

in which I _Fin 、I _Sin The effective values of the fundamental waves of the two paths of input current are respectively. As can be seen from equation (22), the output current I _FOS Mutual inductance M between primary side and secondary side of non-contact transformer with branch 1 _F Inversely proportional, and the output current is independent of the load resistance value; output current I _SOS Mutual inductance M between primary side and secondary side of non-contact transformer of branch 2 _S Is proportional and independent of the load resistance. In the embodiment, the total current output by the five non-contact converters in parallel is as follows:

in the embodiment, the secondary sides of the two non-contact transformers have the same movement direction relative to the primary side, the mutual inductance M of the two transformers has the same variation trend, and the combination formula (23) shows that the output current of the fifth embodiment of the invention is non-monotonous along with the variation of the mutual inductance M, and through reasonably designing the transformer parameters, the mutual compensation of the output currents of the two non-contact transformation modules can be effectively realized, and the stability of the total output current of the system under the condition of variable coupling coefficients is improved; meanwhile, as can be seen from equation (23), the output current of the fifth embodiment of the present invention is independent of the load resistance under the complete compensation condition, that is, the output current can be constant under the variable load condition.

In order to make the output current gain adapt to the mutual inductance change in a wider range, the mutual inductance value corresponding to the output current extreme point is required to be ensured to be in a working interval. From the mathematical function characteristic of the equation (23), two non-contact transformer parameters need to be designed to satisfy the equation (24) at the complete compensation point.

Example six:

fig. 9 shows a circuit configuration diagram of a sixth embodiment of the contactless converter excited by a voltage source and a current source in a composite mode according to the invention. In the two-way non-contact converter shown in fig. 9, branch 1 and branch 2 are connected in parallel on the dc output side. The branch circuit 1 consists of an alternating-current input voltage source F1, a primary side compensation network F2, a non-contact transformer F3, a secondary side compensation network F4, a rectification circuit F5_1, a filter circuit F5_2 and a load resistor 5_3; the branch 2 is composed of an alternating current input current source S1, a primary side compensation network S2, a non-contact transformer S3, a secondary side compensation network S4, a rectification circuit S5_1, a filter circuit S5_2 and a load resistor 5_3. In the circuit shown in FIG. 9, u _Fin For the AC input voltage source, i _Sin Is an AC input current source, C _xP Compensating the capacitance for the primary side, C _xS Compensating the capacitance for the secondary side, L _xP Is not in contact withSelf-inductance of primary winding of transformer, L _xS Self-inductance of secondary winding of non-contact transformer, M _x Mutual inductance of primary and secondary windings of non-contact transformer, L _ST1 、L _ST2 、C _ST Compensating the resonance inductance, capacitance, D of the T-network for the secondary side of branch 2 _x1 ～D _x4 Is a secondary side rectifier diode, L _xf Is a filter inductor, C _xf Is a filter capacitor, R _L For load resistance, x in the subscript represents "F" or "S".

The primary side compensation network F2 and the secondary side compensation network F4 of the branch circuit 1 are both single-capacitor series compensation and series compensation capacitor C _FP 、C _FS Primary side self-inductance L of non-contact transformer F3 respectively _FP Minor edge self-induction L _FS And (4) resonating. The primary side compensation network S2 of the branch circuit 2 is series capacitance compensation and compensation capacitance C _SP Self-inductance L of primary side of non-contact transformer S3 _SP The resonance secondary side compensation network S4 is composed of a T network with series compensation capacitor C connected in series with LCL _SS Secondary side self-inductance L of non-contact transformer S3 _SS The resonant LCL type T network is used for realizing voltage-current conversion and designing a resonant inductor L _ST1 And L _ST2 Resonant capacitor C _ST And L _ST2 Resonant when resonant inductance L _ST1 Secondary side self-inductance L of non-contact transformer S3 _SS When the inductance values are equal, the series compensation capacitor C can be connected _SS And a resonant inductor L _ST1 Equivalent is replaced by a wire. The two-terminal network of branch 1 port AB is input voltage source series resonance impedance, and the two-terminal network of branch 2 port AB is input current source series resonance impedance, can be equivalent to an input current source. Therefore, the input ports of the non-contact transformers of the two non-contact conversion modules are respectively the input of a voltage source and a current source.

wherein Z _Sr For the reflected impedance of the secondary side of the non-contact transformer of branch 2:

by simplifying the equations (25) and (26) respectively, the effective values I of the output currents of the

branch circuits

1 and 2 can be obtained when the compensation is completed _FOS 、I _SOS Respectively as follows:

wherein U is _Fin 、I _Sin The fundamental wave effective values of two paths of input voltage and current are respectively. As can be seen from equation (27), the output current I _FOS Mutual inductance M between primary side and secondary side of non-contact transformer of branch 1 _F Inversely proportional, and the output current is independent of the load resistance value; output current I _SOS Mutual inductance M between primary side and secondary side of non-contact transformer of branch 2 _S Is proportional and independent of the load resistance. In the embodiment, the total current output by the five non-contact converters in parallel is as follows:

in the embodiment, the secondary sides of the two non-contact transformers have the same movement direction relative to the primary side, the mutual inductance M of the two transformers has the same variation trend, and the combination formula (28) shows that the output current of the sixth embodiment of the invention is non-monotonous along with the variation of the mutual inductance M, and through reasonably designing the transformer parameters, the mutual compensation of the output currents of the two non-contact transformation modules can be effectively realized, and the stability of the total output current of the system under the condition of variable coupling coefficients is improved; meanwhile, as can be seen from equation (28), the output current of the sixth embodiment of the present invention is independent of the load resistance under the complete compensation condition, that is, the output current can be constant under the variable load condition.

In order to adapt the output current gain to the mutual inductance change in a wider range, the mutual inductance value corresponding to the output current extreme point is required to be ensured within a working interval. From the mathematical function characteristic of the equation (28), two non-contact transformer parameters need to be designed to satisfy the equation (29) at the complete compensation point.

Example seven:

fig. 10 is a circuit diagram showing a seventh embodiment of the contactless converter driven by a voltage source and a current source in a composite mode according to the invention. In distinction from the first to sixth embodiments, the voltage source and the current source are applied to the primary two-segment winding L of the same contactless transformer 3 in the seventh embodiment _FP 、L _SP And the secondary side is output by a single winding. The seventh embodiment comprises an alternating-current input voltage source F1, a first primary winding compensation network F2, an alternating-current input current source S1, a second primary winding compensation network S2, a non-contact transformer 3, a secondary side compensation network 4, a rectification circuit 5_1, a filter circuit 5_2 and a load resistor 5_3. In the circuit shown in FIG. 9, u _Fin For an AC input voltage source, i _Sin Is an AC input current source, L _FP 、L _SP Self-inductance, C, of two primary windings of a non-contact transformer _FP 、C _SP Compensation capacitors, L, for two primary windings of a non-contact transformer _S Self-inductance of secondary winding of non-contact transformer, C _S Compensating the capacitance for the secondary side, M _F 、M _S Mutual inductance, M, of two primary and secondary windings of a non-contact transformer _FS Is notMutual inductance between two windings on the primary side of a contact transformer, D ₁ ～D ₄ Is a secondary side rectifier diode, L _f Is a filter inductor, C _f Is a filter capacitor, R _L Is a load resistor. Primary winding L _FP The two-terminal network at the left side of the input port AB is an input voltage source series resonance impedance, and a primary winding L _SP The two-terminal network on the left side of the input port AB is an input current source series resonant impedance, which can be equivalent to an input current source. Therefore, the input ports of the two primary windings of the non-contact transformer are respectively the input of a voltage source and a current source.

By adopting a fundamental wave analysis method, based on a mutual inductance model of the transformer, a non-contact conversion single-path basic input-output relation shown in fig. 10 can be obtained:

when two windings on the primary side are symmetrically wound, the parameters of the two windings are considered to be the same, and the self-inductance of the windings is uniformly L _p The mutual inductance of the two primary windings and the secondary winding is uniformly expressed by M, the coupling coefficient is uniformly expressed by k, and the output voltage U can be obtained by the equation (30) _o The expression at the fully compensated frequency point is:

wherein M is ₀ And designing a secondary compensation capacitor to compensate the self-inductance value of the secondary side for completely compensating the mutual inductance value of the primary side and the secondary side at the design point. As can be seen from equation (31), the output voltage is not monotonous with the change of the mutual inductance M. Meanwhile, the alternating current input impedances of the two primary windings at the complete compensation point can be derived from the formula (30) as follows:

wherein

k _FS Is the coupling coefficient between the two windings on the primary side. Then when y is a real number, the input impedance Z under variable parameter conditions can be derived _Fin The conditions that the coupling coefficient between the two primary windings needs to meet when the inductance is weak all the time are as follows:

that is, at the full compensation point, the coupling coefficient of the non-contact transformer needs to satisfy:

by substituting equation (35) into equation (33), the input impedance Z can be obtained _Sin The approximation is simplified as follows:

Z _Sin ≈y+jω ₀ L _P (1-k _FS ) (35)

design of omega ₀ L _P (1-k ₁₂ ) When > y, input impedance Z _Sin Approximately pure perceptual. In order to realize ZVS of the switching tube, an input impedance pure resistor is needed, so that a path of series capacitor compensation impedance and a compensation capacitor C are needed to be input into a current source _SP Has a capacitance value of approximately:

test example one:

in order to verify the feasibility of the invention, a PSIM circuit simulation verification was performed by taking the voltage source and current source compound excitation non-contact conversion circuit shown in fig. 3 as an example. The non-contact transformers used in this example are all edge-extended non-contact transformers, and as shown in fig. 11 (a), the present invention is also applicable to other transformer structures. The following table shows the specific parameters of the primary and secondary side self-inductance, mutual inductance and coupling coefficient of the non-contact transformer used in the test varying with the air gap.

Table 1: parameters of a non-contact transformer (F3)

Table 2: parameters of non-contact transformer (S3)

The specific values of the primary and secondary compensation capacitances of branch 1 and branch 2 are shown in table 3 below.

Table 3: parameters of resonant elements

The compensation capacitance of branch 1 and branch 2 is calculated based on formula (3) under the condition of 10cm air gap. Under the condition that the direct-current input voltage is fixed at 400V, the air gap distance between the primary side and the secondary side of the transformer is changed, the output voltage value of the non-contact combined power supply circuit is shown in a table 4, and the output voltage variation curves along with the coupling coefficient under different load conditions are shown in a graph in fig. 11 (b) and a graph in fig. 11 (c). The voltage source and current source compound excitation non-contact conversion circuit provided by the invention can effectively improve the stability of the output characteristic of a non-contact power supply system when a large air gap changes, and simultaneously keeps the output stability of the output voltage characteristic under the variable load condition.

Table 4 (a): heavy load (R) _min ) Two-way output voltage and total output voltage under the condition

Table 4 (a): small load (R) _max ) Two-way output voltage and total output voltage under the condition

Test example two:

in order to verify the feasibility of the present invention, a simulation verification was performed by taking the voltage source and current source compound excitation contactless conversion circuit shown in fig. 10 as an example. The non-contact transformer used in the embodiment is a primary side double-winding single-winding non-contact transformer, two paths of non-contact transformers on the primary side are symmetrically wound, and the self-inductance of the two paths of primary windings is equal and is approximately equal to the mutual inductance value of the secondary winding. Table 5 shows the parameters of the primary and secondary side self-inductance, mutual inductance, and coupling coefficient of the non-contact transformer used in the test, which vary with the air gap.

Table 5: parameters of a non-contact transformer (3)

The specific values of the primary and secondary compensation capacitors, input sources and the like of the branch 1 and the branch 2 are shown in the following table.

Table 6: capacitance value and input source of compensation capacitor

The phase difference between the input alternating current voltage source excitation and the input alternating current source is 180 degrees, and the working frequency is 91kHz. The air gap distance between the primary side and the secondary side of the transformer is changed under the condition of variable load, and the output voltage of the non-contact combined power supply circuit is shown in figure 12. The non-contact combined power supply circuit provided by the invention can effectively improve the stability of the output characteristic of a non-contact power supply system when the air gap changes greatly. In order to realize the soft switching of the inverter corresponding to the input current source side, the input impedance can be adjusted to weak inductance by connecting a capacitor and a small resistor in series at the input side of the current source in practical application.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. A voltage source and current source compound excitation non-contact conversion circuit is characterized in that: the circuit comprises a first non-contact conversion module branch and a second non-contact conversion module branch; the first non-contact conversion module branch circuit is formed by sequentially connecting a first input source (F1), a first primary side compensation network (F2), a first non-contact transformer (F3), a first secondary side compensation network (F4), a first rectification circuit (F5 _ 1) and a first filter network (F5 _ 2) in series, the second non-contact conversion module branch circuit is formed by sequentially connecting a second input source (S1), a second primary side compensation network (S2), a second non-contact transformer (S3), a second secondary side compensation network (S4), a second rectification circuit (S5 _ 1) and a second filter network (S5 _ 2) in series, and the output of the first filter network (F5 _ 2) and the output of the second filter network (S5 _ 2) are connected in series or in parallel and then connected to two ends of a load (5_3); for the first non-contact transformer (F3) and the second non-contact transformer (S3), the current flowing into the primary winding of one non-contact transformer is constant, and the current flowing into the primary winding of the other non-contact transformer is variable quantity which is changed along with the load and the coupling coefficient; one of the first input source (F1) and the second input source (S1) is an alternating current constant voltage source, and the other one is an alternating current constant current source; the alternating current constant voltage source or the alternating current constant current source is obtained by converting a direct current input source and an inverter circuit.

2. The voltage source and current source compound excitation non-contact transformation circuit of claim 1, wherein: the constant current flowing into one path of the primary winding of the non-contact transformer is realized by an LC conversion network or a control circuit.

3. The voltage source and current source compound excitation non-contact conversion circuit according to claim 1, wherein: the first primary side compensation network (F2) and the second primary side compensation network (S2), the first secondary side compensation network (F4) and the second secondary side compensation network (S4) in the two non-contact conversion modules are in the form of series single-capacitor compensation, parallel single-capacitor compensation, series-parallel capacitor compensation, parallel-series capacitor compensation, series/parallel LC network compensation, LCL form compensation, LCC form compensation or a combination of any structures.

4. The voltage source and current source compound excitation non-contact conversion circuit according to claim 1, wherein: and secondary circuits of the two non-contact conversion modules are shared to form a primary double-winding secondary single-winding non-contact transformer structure.

5. The voltage source and current source combined excitation non-contact transformation circuit according to claim 1 or 4, characterized in that: the winding structures of the first non-contact transformer (F3) and the second non-contact transformer (S3) are a single coil structure, a double coil structure or a multi-coil structure, and the primary side magnetic core and/or the secondary side magnetic core are U-shaped, I-shaped, edge-expanded type with the bottoms of two side columns expanded outwards along the side edges, cross-shaped or the combination of the shapes.