CN109698632B

CN109698632B - Current equalizing circuit and current equalizing system for inverter high frequency parallel connection

Info

Publication number: CN109698632B
Application number: CN201711002462.7A
Authority: CN
Inventors: 毛云鹤; 武志贤; 刘彦丁
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2017-10-24
Filing date: 2017-10-24
Publication date: 2020-12-15
Anticipated expiration: 2037-10-24
Also published as: CN109698632A

Abstract

The application discloses a current-sharing circuit and a current-sharing system when inverters are connected in parallel at high frequency, which are used for realizing current sharing among the inverters and can be applied to a wireless charging scene in the field of electric automobiles. To at least two of the following inverters: a first inverter and a second inverter; the output end of the first inverter and the output end of the second inverter are connected in parallel at a common parallel point; the current equalizing circuit comprises: the inductor comprises a first inductor component, a second inductor component and a capacitor component; the first inductance assembly is connected between the output end of the first inverter and the public parallel point, and the second inductance assembly is connected between the output end of the second inverter and the public parallel point; the capacitor assembly is connected between the common parallel point and the post-stage equipment connected with the current equalizing circuit; the first inductance component and the second inductance component are connected in parallel to form an equivalent inductance; the capacitor assembly and the equivalent inductor form series resonance, and the frequency of the series resonance is the same as the switching frequency of the inverter. The circuit ensures the current sharing of the inverters when the inverters are connected in parallel, and the heat distribution of each inverter is uniform, thereby improving the power density and the working efficiency.

Description

Current equalizing circuit and current equalizing system for inverter high frequency parallel connection

Technical Field

The application relates to the technical field of power electronics, in particular to a current equalizing circuit and a current equalizing system when inverters are connected in parallel at high frequency.

Background

With the exhaustion of energy and the increasing environmental pollution, new energy vehicles, such as electric vehicles, are becoming more popular. However, the charging problem of the electric automobile becomes an urgent problem to be solved, the development of the wired charging pile is very fast at present, but one problem faced by the charging is that the charging time with low power is long, and if the electric automobile can be filled with oil like a fuel automobile, the charging power must be increased quickly. Therefore, the wired charging is developed in the direction of 350kW and 500 kW.

However, the problem faced by wired charging is that wired charging requires an operator to manually insert and pull out a charging gun, and the operation in a thunderstorm day is dangerous to be shocked.

In addition, after the battery voltage range of the electric vehicle is determined, the charging power is larger, the charging cable of the charging gun is thicker and heavier, and even the charging cable is held by a person, so that a mechanical device is needed for assisting the operation. In addition, the cables are easy to damage due to frequent plugging and unplugging, and the maintenance cost is high.

In order to solve the above problems of wired charging, wireless charging techniques have been developed.

The power supply and the load which are charged wirelessly are not electrically connected, and a charging gun is not needed. Moreover, the charging is automatically carried out, and the charging process is safe and convenient.

However, wireless charging and wired charging face the same problem, namely that wireless charging also needs to be developed in the direction of fast charging. In the process of developing a wireless charging system towards high power, a single machine structure and a multi-machine parallel structure are provided.

When a mode of connecting a plurality of modules in parallel is adopted for power supply, the parallel connection among the high-frequency modules may cause the output current of each parallel module to be uneven due to the parameter difference, the driving delay and the like of each parallel module, some modules have large output current, and some modules have small output current, so that the heating among inverters is inconsistent, and even the explosion is caused in severe cases.

In the conventional technology, a larger design margin is reserved, so that the module with the most serious heat generation can meet the requirement of temperature rise, but too large redundancy design can reduce the power density of the system and reduce the reliability.

Disclosure of Invention

The application provides a current-sharing circuit and a current-sharing system for high-frequency parallel connection of inverters, which can ensure that current sharing is realized between inverters with output ends connected in parallel.

In a first aspect, a current sharing circuit for high-frequency parallel connection of inverters is provided, which is applied to at least the following two inverters: a first inverter and a second inverter; the output end of the first inverter and the output end of the second inverter are connected in parallel at a common parallel point;

the current equalizing circuit comprises: the inductor comprises a first inductor component, a second inductor component and a capacitor component;

the first inductance assembly is connected between the output end of the first inverter and the common parallel point, and the second inductance assembly is connected between the output end of the second inverter and the common parallel point;

the capacitor assembly is connected between the common parallel point and the post-stage equipment connected with the current equalizing circuit;

the first inductance component and the second inductance component are connected in parallel to form an equivalent inductance;

the capacitance component forms a series resonance with the equivalent inductance.

In a first possible implementation manner of the first aspect, the common parallel point includes a positive common parallel point and a negative common parallel point;

the first inductive component includes: a first inductor and a second inductor; the first inductor is connected between a positive output terminal of the first inverter and the positive common parallel point; the second inductor is connected between the negative output end of the first inverter and the negative common parallel point;

the second inductive component comprises: a third inductor and a fourth inductor; the third inductor is connected between the positive output terminal of the second inverter and the positive common parallel point; the fourth inductor is connected between the negative output end of the second inverter and the negative common parallel point;

the capacitance assembly includes: a first capacitor and a second capacitor; the first capacitor is connected between the positive common parallel point and equipment connected with the rear stage of the inverter; the second capacitor is connected between the negative common parallel point and a device connected at the rear stage of the inverter.

With reference to the first aspect and any one of the foregoing possible implementation manners, in a second possible implementation manner, the common parallel point includes a positive common parallel point and a negative common parallel point;

the first inductive component includes: a first inductor; the first inductor is connected between a positive output terminal of the first inverter and the positive common parallel point;

the second inductive component comprises: a third inductor; the third inductor is connected between the positive output terminal of the second inverter and the positive common parallel point;

the capacitance assembly includes: a first capacitor; the first capacitor is connected between the positive common parallel point and equipment connected with the rear stage of the inverter; or, the capacitive component comprises: a second capacitor; the second capacitor is connected between the negative common parallel point and a device connected with the rear stage of the inverter.

With reference to the first aspect and any one of the foregoing possible implementation manners, in a third possible implementation manner, the common parallel point includes a positive common parallel point and a negative common parallel point;

the first inductive component includes: a second inductor; the second inductor is connected between the negative output end of the first inverter and the negative common parallel point;

the second inductive component comprises: a fourth inductor; the fourth inductor is connected between the negative output end of the second inverter and the negative common parallel point;

the capacitance assembly includes: a second capacitor; the second capacitor is connected between the negative common parallel point and equipment connected with the rear stage of the inverter; or, the capacitive component comprises: a first capacitor; the first capacitor is connected between the positive common parallel point and a device connected at the rear stage of the inverter.

With reference to the first aspect and any one of the foregoing possible implementation manners, in a fourth possible implementation manner, the common parallel point includes a positive common parallel point and a negative common parallel point;

the capacitance assembly includes: a first capacitor and a second capacitor; the first capacitor is connected between the positive common parallel point and equipment connected with the rear stage of the inverter; the second capacitor is connected between the negative common parallel point and equipment connected with the rear stage of the inverter;

or the like, or, alternatively,

With reference to the first aspect and any one of the foregoing possible implementation manners, in a fifth possible implementation manner, the common parallel point includes a positive common parallel point and a negative common parallel point;

With reference to the first aspect and any one of the foregoing possible implementation manners, in a sixth possible implementation manner, an input end of the first inverter is connected to a first direct current source; the input end of the second inverter is connected with a second direct current source;

or the like, or, alternatively,

and the input end of the first inverter and the input end of the second inverter are connected with the same direct current source.

With reference to the first aspect and any one of the foregoing possible implementation manners, in a seventh possible implementation manner, the number of levels of the first inverter and the second inverter is N, where N is an integer greater than or equal to 2.

In a second aspect, a current sharing system for high-frequency parallel connection of inverters is provided, which includes the current sharing circuit for high-frequency parallel connection of inverters, and further includes: a transmitting circuit and at least two of the following inverters: a first inverter and a second inverter;

the inverter is used for inverting the direct current provided by the direct current source into alternating current;

and the transmitting circuit is used for transmitting the alternating current to charge a load.

In a first possible implementation manner of the second aspect, the transmitting circuit includes: a transmit compensation network and a transmit coil;

the capacitance component in the current sharing circuit is integrated with the emission compensation network.

With reference to the second aspect and any one of the foregoing possible implementation manners, in a second possible implementation manner, the transmitting circuit transmits the alternating current in an inductive coupling manner or in a transformer manner.

With reference to the second aspect and any one of the foregoing possible implementation manners, in a third possible implementation manner, the first inverter and the second inverter have the same structure.

In a third aspect, a current sharing circuit is provided, the current sharing circuit comprising: the inductor comprises a first inductor component, a second inductor component and a capacitor component;

the first inductance component is connected between the output end of the first device to be current-equalized and the common parallel point, and the second inductance component is connected between the output end of the second device to be current-equalized and the common parallel point;

The output voltage of the middle points of the bridge arms of the first inverter and the second inverter is square wave, and the frequency of the square wave is the same as the switching frequency of the inverters.

According to the technical scheme, the embodiment of the application has the following advantages:

and a current-sharing circuit is connected in series with the output end of each inverter and comprises an inductance component and a capacitance component, wherein the inductance and the capacitance form series resonance, and the frequency of the series resonance is the same as the switching frequency of the inverter. The current-sharing circuit inhibits the circulation phenomenon generated among the inverters by connecting the inductance assembly in series at the output end of the inverter, and improves the current sharing degree. And the capacitor component is connected in series behind the common parallel point, so that in the operation process of the current equalizing circuit, the equivalent inductance of the inductor component and the capacitor component generate series resonance, further the voltage drop generated on the inductor component is offset, and the problem of voltage drop generated by the inductor component is solved. The current-sharing circuit solves the problem of non-current sharing when a plurality of inverters are connected in parallel. And then can guarantee that each inverter heat distributes evenly, reduces the maintenance cost, has improved power density and whole work efficiency.

Drawings

Fig. 1 is a schematic diagram of an LCL topology applied to the field of induction heating in the prior art;

fig. 2 is a circuit diagram of a current sharing circuit when inverters are connected in parallel at a high frequency according to an embodiment of the present application;

fig. 3 is a circuit diagram of a current sharing circuit when inverters are connected in parallel at a high frequency according to a second embodiment of the present application;

fig. 4a is a circuit diagram of a current sharing circuit when inverters are connected in parallel at a high frequency when the inverters are in a full-bridge configuration according to the second embodiment of the present application;

fig. 4b is a circuit diagram of a current sharing circuit when inverters are connected in parallel at a high frequency according to a second embodiment of the present application;

fig. 4c is a circuit diagram of a current sharing circuit when still another inverter is connected in parallel at a high frequency according to the second embodiment of the present application;

fig. 5 is a circuit diagram of a current sharing circuit when inverters are connected in parallel at a high frequency according to a third embodiment of the present application;

fig. 6a is a circuit diagram of a current sharing circuit when inverters are connected in parallel at a high frequency when the inverters are in a full-bridge configuration according to a third embodiment of the present application;

fig. 6b is a circuit diagram of a current sharing circuit when inverters are connected in parallel at a high frequency according to another embodiment of the present application;

fig. 6c is a circuit diagram of a current sharing circuit when still another inverter is connected in parallel at a high frequency according to the third embodiment of the present application;

fig. 7 is a circuit diagram of a current sharing circuit when inverters are connected in parallel at a high frequency according to a fourth embodiment of the present application;

fig. 8a is a circuit diagram of a current sharing circuit when inverters are connected in parallel at a high frequency when the inverters are in a full-bridge configuration according to an embodiment of the present application;

fig. 8b is a circuit diagram of a current sharing circuit when inverters are connected in parallel at a high frequency according to another embodiment of the present application;

fig. 8c is a circuit diagram of a current sharing circuit when still another inverter is connected in parallel at a high frequency according to the fourth embodiment of the present application;

fig. 9 is a circuit diagram of a current sharing circuit when inverters are connected to the same dc power source and the inverters are connected in parallel at a high frequency according to an embodiment of the present application;

fig. 10 is a circuit diagram of a current sharing circuit when inverters are connected in parallel at a high frequency, which is applied to a plurality of inverters according to an embodiment of the present application;

fig. 11 shows an output voltage waveform and an output current waveform of an inverter obtained without the current equalizing circuit processing when inverters are connected in parallel at a high frequency according to the embodiment of the present application;

fig. 12 shows an output voltage waveform and an output current waveform of an inverter obtained after the inverter is processed by a current equalizing circuit when connected in parallel at a high frequency according to an embodiment of the present application;

fig. 13 shows another inverter output voltage waveform and output current waveform obtained without the current equalizing circuit processing when the inverters are connected in parallel at high frequency according to the embodiment of the present application;

fig. 14 shows another inverter output voltage waveform and output current waveform obtained after the current equalizing circuit processing when the inverters are connected in parallel at high frequency according to the embodiment of the present application;

fig. 15 is a structural diagram of a current equalizing system when inverters are connected in parallel at a high frequency according to a fifth embodiment of the present application;

fig. 16 is a structural diagram of a current equalizing system when inverters are connected in parallel at a high frequency according to a sixth embodiment of the present application;

FIG. 17 is a diagram of the connection structure of electronic components in the emission compensation network that may be integrated with the current sharing capacitors;

fig. 18 is a structural diagram of a current equalizing system when another inverter is connected in parallel at a high frequency according to a sixth embodiment of the present application.

Detailed Description

The current-sharing circuit and the wireless charging system when the inverters are connected in parallel at high frequency provided by the embodiment of the application are used for guaranteeing that current sharing is realized among the inverters of which the output ends are connected in parallel.

With the popularization of electric vehicles, the charging problem of the electric vehicles is more and more concerned. At present, the electric automobile is charged mainly by a wired charging pile, however, the charging power of the wired charging pile is small, and the electric automobile is charged by the wired charging pile for a long time. If the electric automobile needs to be charged quickly, the charging power of the wired charging pile needs to be improved. And improve wired charging pile's charging power, then can appear that the manual work introduced in the background art can't take the charging cable, to the maintenance cost improvement scheduling problem of charging cable.

In order to solve the problems of wired charging, wireless charging technology for electric vehicles is developed. The wireless charging technology is used for realizing the rapid charging of the electric automobile, and the charging power also needs to be improved. Specifically, the output ends of the plurality of high-frequency inverter modules are connected in parallel to provide a larger output power as a charging power to charge the electric vehicle.

When the mode that the output ends of a plurality of high-frequency inversion modules are connected in parallel is adopted, because each high-frequency parallel module possibly has difference in the aspects of parameters, drive delay and the like, the current output by each high-frequency parallel module is uneven, namely, the current output by some modules is large, and the current output by some modules is small, so that the heating of each high-frequency parallel module is different, and the phenomenon of explosion even possibly occurs in severe cases.

At present, a scheme that a plurality of inverter output ends are connected in parallel for current sharing is provided, and the scheme is a high-frequency heating power supply inverter main circuit of a liquid-cooled polysilicon reduction furnace.

However, the inventor researches and discovers that the inverter main circuit has the following defects:

the inverter main circuit adopts the current sharing reactor to inhibit the rapid change of current so as to realize the current sharing of the output current of the three inverter modules, but the voltage drop can be correspondingly generated when the current flows through the current sharing reactor, and therefore, the voltage applied to the electromagnetic induction coil can be reduced. If the voltage applied to the electromagnetic induction coil is kept constant, the dc bus voltage needs to be further increased, and an increase in the dc bus voltage will result in a reduction in the efficiency of the rectifier circuit and the inverter circuit, and a voltage stress of the switching tube when the same current flows increases, which increases the cost of the switching tube.

In addition, a scheme for carrying out current sharing by connecting a plurality of inverter output ends in parallel is provided.

Fig. 1 shows a topological structure diagram of an inductor-capacitor-inductor (LCL) applied in the field of induction heating.

In the system, the output ends of a plurality of inverters are connected with an inductor and then connected in parallel, the voltage at two ends of an output capacitor C is designed to be far higher than the voltage difference of the middle point of a bridge arm of the inverter, and the quality factor Q of a resonance circuit formed by the inductor and the output capacitor is further improvedVoltage V across the output capacitor C₂The current of each inverter is equal to the reactance of the resonance inductor divided by the voltage at the two ends of the output capacitor C, and the current of each inverter is equal as long as the reactance of the inductor connected with the output end of each inverter is equal, so that the current equalizing effect is achieved.

However, the inventor researches and discovers that the LCL topology corresponding to fig. 1 mainly has the following defects:

a high quality factor Q means that the reactive power in the system increases much, which leads to an increase in the total current in the inverter and thus to increased losses in the system. In addition, if the output capacitor C is realized by one capacitor, because the voltage and power level of a single capacitor are insufficient, the output capacitor C needs to be realized by connecting a plurality of capacitors in series and in parallel, and the connection of a plurality of capacitors in series and in parallel will bring new problems of current sharing and voltage sharing.

In summary, the two schemes both bring new problems when solving the current sharing problem of the inverters, and cannot effectively solve the current sharing problem when the inverters are connected in parallel.

In order to solve the above problem, an embodiment of the present application provides a current sharing circuit, including: the inductor comprises a first inductor component, a second inductor component and a capacitor component; the first inductance component is connected between the output end of the first device to be equalized and the common parallel point, and the second inductance component is connected between the output end of the second device to be equalized and the common parallel point; the capacitor assembly is connected between the common parallel point and the post-stage equipment connected with the current equalizing circuit; the first inductance component and the second inductance component are connected in parallel to form an equivalent inductance; the capacitance component forms a series resonance with the equivalent inductance. The first device to be current-shared may be a first inverter, and the second device to be current-shared may be a second inverter.

The current-sharing circuit provided by the embodiment of the application solves the problem of uneven current existing when a plurality of inverters are connected in parallel at high frequency in a high-power application occasion, and when the plurality of inverters are connected in parallel at high frequency, the current-sharing circuit provided by the embodiment of the application can ensure that each inverter realizes current sharing, so that the heat distribution is uniform, the maintenance cost is reduced, and the power density and the overall working efficiency are improved.

Example one

Referring to fig. 2, a circuit diagram of a current sharing circuit when inverters are connected in parallel at a high frequency is provided in this embodiment.

The current equalizing circuit is applied to at least two inverters: a first inverter 201 and a second inverter 202. The output of the first inverter 201 and the output of the second inverter 202 are connected in parallel at a common parallel point.

The method provided by the embodiment of the application is suitable for high-frequency parallel connection of the inverters. The high-frequency parallel connection means that the midpoint voltage of a high-frequency output bridge arm of the inverter is connected in parallel, and the frequency is generally from hundreds of Hz to hundreds of kHz. The high frequency output voltage of the inverter is different from the power frequency output voltage of the inverter, the high frequency output voltage of the inverter is usually a square wave with the same switching frequency, and the power frequency output voltage of the inverter is usually a sine wave of the mains frequency. For the power frequency output of the inverter, high-frequency harmonic belongs to interference signals and needs to be filtered. The high frequency output of the inverter is a square wave with the same switching frequency, so that the high frequency signal is not an interference signal.

The current sharing circuit is suitable for inverters with two or more output ends connected in parallel, and for convenience of description, the embodiment is described by taking the example that the output ends of two inverters are connected in parallel.

The current sharing circuit includes a first inductive component 203, a second inductive component 204, and a capacitive component 205.

The first inductance component 203 and the second inductance component 204 each include at least one inductance, and the capacitance component 205 includes at least one capacitance. The inductance assembly and the capacitance assembly are connected in series between the output end of the inverter and the post-stage equipment.

Specifically, the common parallel points include a positive common parallel point a and a negative common parallel point B.

The positive output of the first inverter 201 and the positive output of the second inverter 202 are connected in parallel at a positive common parallel point a, and the negative output of the first inverter 201 and the negative output of the second inverter 202 are connected in parallel at a negative common parallel point B.

A first inductive component 203 is connected between the output of the first inverter 201 and the common parallel point and a second inductive component 204 is connected between the output of the second inverter 202 and the common parallel point.

The capacitor assembly 205 is connected between the common parallel point and the subsequent devices connected to the current equalizing circuit. As shown in fig. 2 as a back-end device 206, the back-end device 206 may be a transmit compensation network, a transmit coil, or the like for delivering electrical energy to a load.

The first inductance component 203 and the second inductance component 204 are connected in parallel to form an equivalent inductance.

The capacitance component 205 and the equivalent inductance form a series resonance, and the frequency of the series resonance is the same as the switching frequency of the inverter.

In this embodiment, the first inductance component 203 and the second inductance component 204 are respectively connected in series to the output ends of the first inverter 201 and the second inverter 202, and the first inductance component 203 and the second inductance component 204 can suppress the circulating current between the first inverter 201 and the second inverter 202, thereby improving the current sharing rate of the inverters.

In addition, the capacitor assembly 205 can form a series resonance with the equivalent inductor, so as to offset a voltage drop generated by the first inductor assembly 203 and the second inductor assembly 204, and ensure that the output voltage of the inverter is kept unchanged while achieving a current sharing effect.

The resonant frequency of the series resonance formed by the capacitor assembly 205 and the equivalent inductor in series is the same as the switching frequency of the first inverter 201 and the second inverter 202. Assume that the switching frequencies of the first inverter 201 and the second inverter 202 are both f_sIn order to ensure that the capacitance component 205 can counteract the voltage drop generated across the first inductance component 203 and the second inductance component 204, it is necessary to ensure that the frequency of the series resonance formed between the capacitance component 205 and the equivalent inductance is equal to the switching frequency of the inverter, i.e. the frequency of the series resonance is also f_s. Because only if the frequency of the series resonance is the same as the frequency of the inverter switching tube, the inductive reactance of the inductive component is offset by the capacitive reactance of the capacitive component, from the inductive component and the capacitorThe voltage drop on the inductance component and the capacitance component is zero, so that the voltage on the resonance network is equal to the fundamental voltage of the inverter. However, in actual operation, due to the difference in device parameters, the switching frequencies of the two inverters may not be identical, and there may be a slight difference. In the embodiment of the present application, it is desirable that the resonant frequency is defined to be the same as the switching frequency of the inverter. Even if the switching frequencies of the two inverters are different in actual operation, the difference between the two inverters is within a certain range, i.e., the switching frequencies of the two inverters can be considered to be approximately the same.

However, if the frequency of the series resonance is not the same as the switching frequency of the inverter, a voltage will still be divided across the inductive and capacitive components, resulting in a voltage across the resonant network that is lower than the fundamental voltage of the inverter.

The working principle of the current sharing circuit provided in this embodiment is specifically described:

the output terminals of the first inverter 201 are connected to a common parallel point through a first inductive component 203, and the output terminals of the second inverter 202 are connected to the common parallel point through a second inductive component 204, assuming that the inductance value of the first inductive component 203 is L₁The value of the second inductive component 204 is L₂The equivalent inductance value formed by the first inductance component 203 and the second inductance component 204 connected in parallel is L_eq，γ₁The first inductance component 203 is relative to the equivalent inductance L_eqRatio of (a) to (b), gamma₂The second inductance component 204 is equivalent to the equivalent inductance L_eqSatisfies the relationship of formula (1):

wherein, γ₁And gamma₂Satisfies the relationship of the formula (2):

γ₁+γ₂＝1 (2)

equivalent inductance L formed by connecting the first inductance component 203 and the second inductance component 204 in parallel_eqThe calculation can be performed using equation (3):

further, in the current sharing circuit including the capacitor 205, the equivalent inductance L is assumed to be_eqThe capacitance of the capacitance element 205 constituting the series resonance is C_eqTherefore, the calculation formula (4) of the corresponding series resonance frequency is as follows:

from the structure of the current sharing circuit shown in fig. 2 and equations (1) to (4), the relation equation (5) can be derived, and then the differential mode fundamental wave output currents of the first inverter and the second inverter connected in parallel satisfy equation (5), where equation (5a) represents the differential mode fundamental wave output current of the first inverter, equation (5b) represents the differential mode fundamental wave output current of the second inverter, and the inverter differential mode fundamental output current, i.e., the inverter high-frequency output voltage U₁、U₂Current at resonant frequency ω corresponding to output equivalent impedance Z:

by U_kThe midpoint voltage difference of the inverter bridge arm is represented as shown in equation (6):

wherein, U_kaAnd U_kbThe voltage is the fundamental wave voltage of the middle point of the bridge arm of the inverter relative to the middle point of the bus, and Z is the equivalent impedance of the equipment connected with the rear stage of the inverter. The voltage across the back-end device 206 in FIG. 2 is divided by the current through the back-end device to obtain the equivalent impedanceZ, when the equivalent impedance Z satisfies the relationship of the formula (7), the equivalent impedance Z in the formula (5) can be ignored

That is, the expressions (5a) and (5b) are converted to the expressions (8a) and (8b), respectively.

|Z|＜＜|jωL_eq| (7)

As can be seen from equations (8a) and (8b), the output current of each inverter is related to the ratio of the connected inductance component to the equivalent inductance, and the weighted average output voltage of the inverter, and not only is the amplitude and phase of the output voltage of the single inverter affected, i.e., the ratio of the inductance component to the equivalent inductance, will determine the current sharing degree of the output currents of the inverters.

The above embodiment is described by taking the example where the output terminals of two inverters are connected in parallel. When the number of the inverters is greater than 2, the operation principle of the current equalizing circuit provided by the embodiment of the application is still the same as the principle. The number of the inverters is at least two, and the number of the inductance components corresponds to the number of the inverters, namely the number of the inductance components is equal to the number of the inverters. Moreover, when the current sharing circuit provided in this embodiment is applied to more than two inverters, the equivalent inductance formed by connecting the inductance components connected in series with the inverters in parallel still needs to be ensured to form series resonance with the capacitance component.

Now, with reference to the working principle of the current sharing circuit when two inverters are connected in parallel provided by the above embodiment, the working principle of the current sharing circuit when N inverters are connected in parallel is introduced:

assuming that the switching frequencies of the N inverters are f_sEach of the N inverters is connected in parallel to a common parallel point by an inductive component, wherein it is assumed thatThe inductance component connected with the N inverters in parallel is L₁～L_n，L₁～L_nThe inductance components are connected in parallel to form an equivalent inductance L_eq，γ₁～γ_nRespectively an inductance component L₁～L_nRelative to the equivalent inductance L_eqSatisfies the relationship of equation (9):

wherein, γ₁～γ_nSatisfies the relationship of the formula (10):

the inductance components are connected in parallel to form an equivalent inductance L_eqThe calculation method of (2) is as follows:

further, the current sharing circuit provided in this embodiment further includes a capacitor 205, and an equivalent capacitance of the capacitor 205 is C_eqEquivalent inductance L_eqA series resonance can be formed, and the calculation method of the resonance frequency ω of the series resonance is as follows (12):

according to the circuit structure provided by the embodiment and the expressions (9) to (12), the expression (13) can be derived, the differential mode fundamental wave output current of the ith parallel inverter satisfies the expression (13), and the inverter differential mode basic output current, namely the inverter output voltage U₁～U_nCurrent corresponding to the resonant frequency ω of the output equivalent impedance Z:

voltage U_kThe calculation method is as follows, wherein the calculation method is as follows (14):

when the current sharing circuit provided in this embodiment works, the equivalent impedance Z can be obtained by dividing the voltage detected at the two ends of the post-stage device by the current flowing through the post-stage device, and when the equivalent impedance Z satisfies the relationship of equation (15):

|Z|＜＜|jωL_eq| (15)

at this time, the former term in the formula (13) can be ignored, resulting in the formula (16):

as can be seen from equation (16), the output current of each inverter is related to the ratio of the connected inductance component to the equivalent inductance, and the weighted average output voltage of the inverter, and not only the amplitude and phase of the output voltage of a single inverter, i.e. the ratio of the inductance component to the equivalent inductance, will determine the current sharing degree of the output current of the inverter.

According to the current-sharing circuit provided by the embodiment, the inductor assembly is connected in series with the output end of the inverter, so that the circulation phenomenon among the inverters is inhibited, and the current sharing degree is improved. And the capacitor assembly is connected in series behind the common parallel point, so that in the operation process of the current-sharing circuit, the equivalent inductance of the inductor assembly and the capacitor assembly generate series resonance, further the voltage drop generated on the inductor assembly is offset, and the problem of voltage drop generated by the inductor assembly is solved. The current-sharing circuit solves the problem of non-current sharing when a plurality of inverters are connected in parallel. And then can guarantee that each inverter heat distributes evenly, reduces the maintenance cost, has improved power density and whole work efficiency.

The inductor component in the current-sharing circuit provided in the above embodiment may specifically be an inductor, the capacitor component may specifically be a capacitor, and when the inductor component specifically is an inductor and the capacitor component specifically is a capacitor, the current-sharing circuit provided in the embodiment of the present application may have the following three implementation manners:

in a first implementation, each inductor assembly comprises two inductors, wherein one inductor is connected between the positive output terminal of the inverter and the positive common parallel point, and the other inductor is connected between the negative output terminal of the inverter and the negative common parallel point. The capacitor assembly comprises two capacitors which are respectively connected between the positive common parallel point, the negative common parallel point and the post-stage equipment. Each inductance assembly comprises two inductances, and the capacitance assembly can also comprise only one capacitance which can be connected between a positive or negative common parallel point and a subsequent device.

In a second implementation, only one inductor is included in each inductor assembly, and each inductor is connected between the positive output terminal of the inverter and the positive common parallel point. The capacitor assembly comprises two capacitors which are respectively connected between the positive common parallel point, the negative common parallel point and the post-stage equipment. The capacitor assembly also includes only one capacitor connected between the positive or negative common shunt point and the subsequent device.

In a third implementation, only one inductor is included in each inductor assembly, and each inductor is connected between the negative output terminal of the inverter and the negative common parallel point. The capacitor assembly comprises two capacitors which are respectively connected between the positive common parallel point, the negative common parallel point and the post-stage equipment. The capacitor assembly may include only one capacitor connected between the positive or negative common parallel point and the subsequent device.

The following respectively describes the above three implementation methods, and first describes the current sharing circuit in the first implementation manner.

Example two

Referring to fig. 3, a circuit diagram of another current sharing circuit for high-frequency parallel connection of inverters according to this embodiment is provided.

As shown in fig. 3, the common parallel points include a positive common parallel point a and a negative common parallel point B.

The first inductance assembly includes: a first inductance L11 and a second inductance L12.

A first inductor L11 is connected between the positive output of the first inverter and the positive common parallel point a; the second inductor L12 is connected between the negative output of the first inverter and the negative common shunt point B.

The second inductance assembly includes: a third inductance L21 and a fourth inductance L22.

A third inductor L21 is connected between the positive output of the second inverter and the positive common parallel point a; the fourth inductor L22 is connected between the negative output of the second inverter and the negative common shunt point B.

The capacitor assembly includes: a first capacitor C1 and a second capacitor C2.

The first capacitor C1 is connected between the positive common parallel point a and the inverter post-connected device; the second capacitor C2 is connected between the negative common parallel point B and the device connected at the subsequent stage of the inverter.

The operation principle of the current equalizing circuit provided in this embodiment is the same as that of the current equalizing circuit provided in the first embodiment. Specifically, in the current sharing circuit provided in this embodiment, the first inductor L11 and the second inductor L12 in the first inductor assembly, and the third inductor L21 and the fourth inductor L22 in the second inductor assembly are used to suppress the current output by each inverter, so that the current output by the first inverter and the current output by the second inverter achieve the effect of current sharing.

The first inductor L11 and the second inductor L12, and the third inductor L21 and the fourth inductor L22 in the second inductor assembly are connected in parallel to form an equivalent inductor, specifically, the first inductor L11 and the second inductor L12 are connected in series to form a first equivalent inductor (L11+ L12), the third inductor L21 and the fourth inductor L22 in the second inductor assembly are connected in series to form a second equivalent inductor (L21+ L22), and the first equivalent inductor and the second equivalent inductor are connected in parallel to form an equivalent inductor.

The first capacitor C1 and the second capacitor C2 are connected in series to obtain an equivalent capacitor, the equivalent capacitor and the equivalent inductor can form series resonance, and voltage drop generated on each inductor is counteracted through the series resonance between the equivalent inductor and the equivalent capacitor. The output voltage of the inverter is kept unchanged while the current equalizing effect is achieved.

In addition, the inverter applied to the current sharing circuit provided in this embodiment may be a full-bridge structure, as shown in fig. 4 a.

The input end of each inverter is connected with an independent direct current source. The structure of each inverter is the same, and each inverter is a full-bridge structure formed by switching tubes S1-S4, specifically, the switching tubes S1 and S2 form a first bridge arm, and the switching tubes S3 and S4 form a second bridge arm. In first inverter 201, U1a is the midpoint of the first leg and U1b is the midpoint of the second leg. In second inverter 202, U2a is the midpoint of the first leg and U2b is the midpoint of the second leg.

First inductor L11 has one end connected to first leg midpoint U1a in first inverter 201 and the other end connected to positive common parallel point a, and second inductor L12 has one end connected to second leg midpoint U1B in first inverter 201 and the other end connected to negative common parallel point B. Similarly, a third inductor L21 has one end connected to first leg midpoint U2a in second inverter 202 and the other end connected to positive common parallel point a, and a fourth inductor L22 has one end connected to second leg midpoint U2B in second inverter 202 and the other end connected to negative common parallel point B.

Furthermore, as shown in fig. 4b, the capacitor assembly may also comprise only one capacitor: and a first capacitor C1, the first capacitor C1 being connected between the positive common parallel point and the inverter downstream connected device.

Furthermore, as shown in fig. 4C, the capacitor assembly may further include only a second capacitor C2, the second capacitor C2 being connected between the negative common parallel point and the device connected to the rear stage of the inverter.

The current sharing circuit provided by this embodiment may also be applied to inverters with more than two output terminals connected in parallel, for example, three, four, or five inverters. Similarly, an inductor is respectively connected between the positive output end of each inverter and the positive common parallel point and between the negative output end of each inverter and the negative common parallel point, so that the current equalizing effect is achieved when the inverters are connected in parallel at high frequency.

The inductor and the capacitor in the current sharing circuit provided by the embodiment are symmetrically connected, so that the current sharing is realized, and meanwhile, the anti-interference capability of the circuit is improved, for example, the EMI performance is enhanced. The current-sharing circuit provided by the embodiment solves the problem of uneven current existing when a plurality of inverters are connected in parallel at high frequency, so that the heat of each inverter can be uniformly distributed, the maintenance cost is reduced, and the power density and the overall working efficiency are improved.

The following describes the current equalizing circuit in the second implementation manner.

EXAMPLE III

Referring to fig. 5, a circuit diagram of a current sharing circuit for high frequency parallel connection of another inverter provided in this embodiment is shown.

Wherein the common parallel points include a positive common parallel point a and a negative common parallel point B.

The first inductance assembly includes: the first inductance L1.

A first inductor L1 is connected between the positive output of the first inverter and the positive common shunt point a.

The second inductance assembly includes: and a third inductance L3.

A third inductor L3 is connected between the positive output of the second inverter and the positive common shunt point a.

The capacitor assembly includes: a first capacitor C1.

The first capacitor C1 is connected between the positive common parallel point a and the device to which the inverter is connected at the rear stage.

Compared with the current equalizing circuit provided by the second embodiment, the current equalizing circuit provided by the embodiment reduces electronic devices in the circuit, but can still achieve the effect of realizing current equalization when the inverters are connected in parallel at high frequency.

The operation principle of the current equalizing circuit provided in this embodiment is the same as that of the current equalizing circuit provided in the first embodiment. Specifically, in the current sharing circuit provided in this embodiment, the first inductor L1 in the first inductor assembly and the third inductor L3 in the second inductor assembly are used to suppress the current output by each inverter, so that the current output by the first inverter and the current output by the second inverter achieve the effect of current sharing.

The first inductor L1 and the third inductor L3 are connected in parallel to form an equivalent inductor. The equivalent inductor and the first capacitor C1 can form series resonance, and the series resonance between the equivalent inductor and the first capacitor counteracts the voltage drop generated on each inductor, so that the output voltage of the inverter is kept unchanged while the current equalizing effect is achieved.

In addition, the inverter applied to the current sharing circuit provided in this embodiment may be a full-bridge structure, as shown in fig. 6 a.

The input end of each inverter is connected with an independent power supply, the structure of each inverter is the same, each inverter is in a full-bridge structure formed by switching tubes S1-S4, specifically, a first bridge arm is formed by the switching tubes S1 and S2, and a second bridge arm is formed by the switching tubes S3 and S4. In first inverter 201, U1a is the midpoint of the first leg and U1b is the midpoint of the second leg. In second inverter 202, U2a is the midpoint of the first leg and U2b is the midpoint of the second leg.

One end of the first inductor L1 is connected to U1a in the first inverter 201, and the other end of the first inductor L1 is connected to the positive common parallel point a. Similarly, one end of the third inductor L3 is connected to U2a in the second inverter 202, and the other end of the third inductor L3 is connected to the positive common parallel point a.

Furthermore, as shown in fig. 6b, the capacitive assembly may also include only: and a second capacitor C2, the second capacitor C2 being connected between the negative common parallel point and the inverter downstream device.

Furthermore, as shown in fig. 6c, the capacitive assembly may further include two capacitors: a first capacitor C1 and a second capacitor C2, wherein the first capacitor C1 is connected between the positive common parallel point and the inverter post-connected device, and the second capacitor C2 is connected between the negative common parallel point and the inverter post-connected device.

The current sharing circuit provided by the embodiment can also be applied to more inverters with output ends connected in parallel, for example, three, four or five inverters. Similarly, an inductor is connected between the positive output end of each inverter and the positive common parallel point, so that the current sharing effect is achieved when the inverters are connected in parallel at high frequency.

The current-sharing circuit provided by the embodiment reduces the number of inductance devices, further simplifies the circuit structure of the current-sharing circuit, and can reduce the production cost in the production process of mass production of the current-sharing circuit. In addition, the current equalizing circuit provided by the embodiment solves the problem of uneven current existing when a plurality of inverters are connected in parallel at a high frequency, so that the heat of each inverter can be uniformly distributed, the maintenance cost is reduced, and the power density and the overall working efficiency are improved.

The current equalizing circuit in the third implementation manner is described below.

Example four

Referring to fig. 7, a circuit diagram of a current equalizing circuit for high frequency parallel connection of another inverter according to this embodiment is provided.

The common parallel points include a positive common parallel point a and a negative common parallel point B.

The first inductance assembly includes: a second inductance L2.

The second inductor L2 is connected between the negative output terminal of the first inverter 201 and the negative common parallel point B.

The second inductance assembly includes: a fourth inductance L4.

A fourth inductor L4 is connected between the negative output of the second inverter 202 and the negative common shunt point B.

The capacitor assembly includes: a second capacitor C2.

The second capacitor C2 is connected between the negative common parallel point B and the device to which the inverter is connected at the rear stage.

The current-sharing circuit provided by the second embodiment has fewer electronic devices, but can still achieve the effect of current sharing when the inverters are connected in parallel at high frequency.

The operation principle of the current equalizing circuit provided in this embodiment is the same as that of the current equalizing circuit provided in the first embodiment. Specifically, in the current sharing circuit provided in this embodiment, the second inductor L2 in the first inductor assembly and the fourth inductor L4 in the second inductor assembly are used to suppress the current output by each inverter, so that the current output by the first inverter and the current output by the second inverter achieve the effect of current sharing.

The second inductor L2 and the fourth inductor L4 are connected in parallel to form an equivalent inductor. The equivalent inductor and the second capacitor C2 can form series resonance, and the series resonance between the equivalent inductor and the second capacitor counteracts the voltage drop generated on each inductor, so that the output voltage of the inverter is kept unchanged while the current equalizing effect is achieved.

In addition, the inverter applied to the current sharing circuit provided in this embodiment may be a full-bridge structure, as shown in fig. 8 a.

One end of the second inductor L2 is connected to U1B in the first inverter 201, and the other end of the second inductor L2 is connected to the negative common parallel point B. Similarly, one end of the fourth inductor L4 is connected to U2B in the second inverter 202, and the other end of the fourth inductor L4 is connected to the negative common parallel point B.

Furthermore, as shown in fig. 8b, the capacitive assembly may also include only: and a first capacitor C1, the first capacitor C1 being connected between the positive common parallel point and the inverter downstream connected device.

Furthermore, as shown in fig. 8c, the capacitive component may further include two capacitors: a first capacitor C1 and a second capacitor C2, wherein the first capacitor C1 is connected between the positive common parallel point and the inverter post-connected device, and the second capacitor C2 is connected between the negative common parallel point and the inverter post-connected device.

The current sharing circuit provided by the embodiment can also be applied to more than two inverters with output ends connected in parallel, for example, three, four or five inverters. Similarly, an inductor is connected between the negative output end of each inverter and the negative common parallel point, so that the current sharing effect is achieved when the inverters are connected in parallel at high frequency.

It should be noted that the input terminals of the inverters provided in the first to fourth embodiments may be respectively connected to different dc sources, that is, the input terminal of the first inverter is connected to the first dc source, and the input terminal of the second inverter is connected to the second dc source. The input terminals of the inverters may be connected to the same dc source, as shown in fig. 9.

In addition, in the current sharing circuit for high-frequency parallel connection of the inverters provided in the first to fourth embodiments, the number of levels of the applied inverters may be an integer greater than or equal to 2, and is suitable for a two-level inverter, a three-level inverter, a four-level inverter, a five-level inverter, a seven-level inverter, or the like.

In order to be able to provide more power, it is generally necessary to connect a plurality of inverters in parallel at high frequency, as shown in fig. 10, and the output terminals of n inverters 1-n are connected in parallel to provide more power to the load. Fig. 10 shows a plurality of inverter outputs connected in parallel for wireless charging, for example, for charging electric vehicles with high power.

In order to better embody the current sharing effect of the current sharing circuit provided in the above embodiment, a simulation waveform diagram before current sharing and a simulation waveform diagram after current sharing are introduced below.

The upper half of the waveforms in fig. 11 to 14 are output voltage waveforms of the inverter, and the lower half of the waveforms are output current waveforms of the inverter.

In fig. 11 and 12, the waveform 1 corresponds to the first inverter, and the waveform 2 corresponds to the second inverter.

As shown in fig. 11, waveforms of the output voltage and the output current of the inverter which are not processed by the current equalizing circuit are shown.

The input voltage of the inverter 1 is 760V, and the input voltage of the inverter 2 is 380V.

As shown in fig. 12, waveforms of the inverter output voltage and the output current obtained after the current equalizing circuit in the above embodiment are shown, and similarly, the input voltage of the inverter 1 is 760V, and the input voltage of the inverter 2 is 380V.

Through comparison, the output current deviation of the two inverters with different input voltages obtained after the current equalizing circuit provided by the embodiment is very small and basically close to the same.

Each of the waveforms 1 in fig. 13 and 14 corresponds to three inverters without phase shift, and each of the waveforms 2 corresponds to another inverter with a phase shift of 30 ° with respect to the output voltages of the other three inverters.

As shown in fig. 13, the waveforms of the output voltages and the output currents of the inverters obtained when four inverters are connected in parallel at a high frequency are shown, wherein the output voltages of three inverters have no phase shift, the output voltage of the other inverter has a phase shift of 30 ° with the output voltages of the other three inverters, and the input voltages of the four inverters are all 760V.

As shown in fig. 14, waveforms of output voltages and currents of the same four inverters obtained after the current equalizing circuit provided in the above embodiment is used.

Through comparison, voltage sources of different phases are connected in parallel, and the circulating current between inverters obtained without the treatment of the current equalizing circuit is very large, namely 5400A and 1840A. The deviation of the output current of the inverter processed by the current equalizing circuit in the embodiment is only about 20A, and therefore, the current equalizing circuit provided by the embodiment of the application has a good current equalizing effect.

Based on the current sharing circuit for high-frequency parallel connection of inverters provided by the embodiment, the embodiment of the application further provides a current sharing system for high-frequency parallel connection of inverters, and the working principle of the current sharing system is described in detail with reference to the accompanying drawings.

EXAMPLE five

Referring to fig. 15, a structure diagram of a current equalizing system when inverters are connected in parallel at a high frequency is provided in this embodiment.

The current sharing system for high-frequency parallel connection of inverters provided by this embodiment includes the current sharing circuit for high-frequency parallel connection of inverters in the above embodiment, and further includes a transmitting circuit 1503 and at least the following two inverters: a first inverter 201 and a second inverter 202.

And the inverter is used for inverting the direct current provided by the direct current source into alternating current.

The transmitting circuit 1503 is used for transmitting the alternating current to charge the load.

The current equalizing system can be used in the field of wireless charging, for example, when the current equalizing system is used for charging an electric automobile, the current equalizing system can be used for charging a storage battery of the electric automobile, and the load can be the storage battery of the electric automobile. When the flow equalizing system is applied to the field of induction heating, the load can be equipment needing heating, such as various profiles needing heating to melt or deform. Specifically, casting of aluminum equipment and the like can be realized.

As shown in fig. 15, the first inverter 201 is connected to the dc power source Vdc1 for inverting the dc power outputted from the dc power source Vdc1 into ac power, and the second inverter 202 is connected to the dc power source Vdc2 for inverting the dc power outputted from the dc power source Vdc2 into ac power.

It should be noted that the number of the inverters that can be included in the current sharing system provided in this embodiment may be any number greater than or equal to 2, that is, the current sharing system includes at least two inverters, each inverter may be connected to a dc power supply, and of course, each inverter may also be connected to the same dc power supply.

The transmitting circuit 1403 transmits the alternating current output from the current equalizing circuit to charge the load.

The current-sharing system provided by the embodiment adopts the current-sharing circuit when the inverters are connected in parallel at high frequency, so that the circulation phenomenon among the inverters is inhibited, and the current sharing degree is improved. And the capacitor assembly is connected in series behind the common parallel point, so that in the operation process of the current-sharing circuit, the equivalent inductance of the inductor assembly and the capacitor assembly generate series resonance, further the voltage drop generated on the inductor assembly is offset, and the problem of voltage drop generated by the inductor assembly is solved. The wireless charging system solves the problem of non-uniform current when a plurality of inverters are connected in parallel. And then can guarantee that each inverter heat distributes evenly, reduces the maintenance cost, has improved power density and whole work efficiency.

Based on the current equalizing system provided in the fifth embodiment, the current equalizing system provided in this embodiment further specifically includes an emission compensation network, and since the emission compensation network generally includes a capacitance component, the capacitance component in the emission compensation network can be directly utilized to form a series resonance with the equivalent inductance.

EXAMPLE six

Referring to fig. 16, a structural diagram of another current equalizing system provided in this embodiment is shown.

The transmitting circuit of the current equalizing system provided in this embodiment includes a transmitting compensation network 1601 and a transmitting coil.

Since the emission compensation network 1601 includes a capacitor, the capacitor component in the current sharing circuit can be integrated with the emission compensation network.

As shown in fig. 17, in a capacitance and inductance connection structure commonly found in

ports

1, 2, 3, and 4 of the transmission compensation network 1601, if, as viewed from points a and B to the right side, the equivalent capacitance of each capacitance device obtained by an equivalent method and the equivalent inductance formed by each inductance device in the current sharing circuit can generate series resonance, it is described that the equivalent capacitance can cancel the voltage drop generated on each inductance. The capacitor device may be a capacitor device added to the circuit or a capacitor device included in the emission compensation network.

As shown in fig. 16, the transmitting circuit may transmit the alternating current in an inductively coupled manner. As shown in fig. 18, the transmitting circuit may also transmit the alternating current in the form of a transformer.

Now, with reference to fig. 16, the operation principle of the current sharing system provided in this embodiment is described:

the transmitting terminal converts the direct current power supply of the direct current power supply into high-frequency alternating current voltage through each inverter, the high-frequency alternating current voltage generates alternating current on the transmitting coil through the transmitting compensation network and the transmitting coil of the transmitting terminal, and the alternating current further generates an alternating magnetic field.

The receiving coil of the receiving end induces a voltage at both ends of the receiving coil by electromagnetic induction, thereby generating a current in the receiving end, and converts the received voltage into a voltage required by the load through the receiving compensation network 1602 and the rectifying circuit 1603.

In the current equalizing system provided by this embodiment, the current equalizing circuit used in the high-frequency parallel connection of the inverters in the above embodiment is adopted, so that the current output by each inverter in the system can achieve the current equalizing effect, the heat inside the system is distributed uniformly, the maintenance cost of the system is reduced, and the overall working efficiency of the system is improved. The current equalizing system is applied to the field of wireless charging of electric automobiles, the electric automobiles are charged through electromagnetic induction, and high-power wireless quick charging of the electric automobiles can be realized due to the fact that the current equalizing system can comprise a plurality of inversion modules.

As mentioned above, the above embodiments are only used to illustrate the technical solutions of the embodiments of the present application, and not to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A current equalizing circuit for high-frequency parallel connection of inverters is characterized by being applied to at least two of the following inverters: a first inverter and a second inverter; the output end of the first inverter and the output end of the second inverter are connected in parallel at a common parallel point;

the capacitance component and the equivalent inductance form series resonance to counteract voltage drop generated on the first inductance component and the second inductance component.

2. The current sharing circuit for high-frequency parallel connection of inverters according to claim 1, wherein the common parallel point comprises a positive common parallel point and a negative common parallel point;

the capacitance assembly includes: a first capacitor and a second capacitor; the first capacitor is connected between the positive common parallel point and the inverter-connected subsequent device; the second capacitor is connected between the negative common parallel point and the inverter-connected subsequent device.

3. The current sharing circuit for high-frequency parallel connection of inverters according to claim 1, wherein the common parallel point comprises a positive common parallel point and a negative common parallel point;

the capacitance assembly includes: a first capacitor; the first capacitor is connected between the positive common parallel point and the inverter-connected subsequent device; or, the capacitive component comprises: a second capacitor; the second capacitor is connected between the negative common parallel point and the inverter-connected subsequent device.

4. The current sharing circuit for high-frequency parallel connection of inverters according to claim 1, wherein the common parallel point comprises a positive common parallel point and a negative common parallel point;

the capacitance assembly includes: a second capacitor; the second capacitor is connected between the negative common parallel point and the post-stage device connected with the inverter; or, the capacitive component comprises: a first capacitor; the first capacitor is connected between the positive common parallel point and the inverter-connected subsequent device.

5. The current sharing circuit for high-frequency parallel connection of inverters according to claim 1, wherein the common parallel point comprises a positive common parallel point and a negative common parallel point;

the capacitance assembly includes: a first capacitor and a second capacitor; the first capacitor is connected between the positive common parallel point and the inverter-connected subsequent device; the second capacitor is connected between the negative common parallel point and the post-stage device connected with the inverter;

or the like, or, alternatively,

6. The current sharing circuit for high-frequency parallel connection of inverters according to claim 1, wherein the common parallel point comprises a positive common parallel point and a negative common parallel point;

7. The current sharing circuit for high-frequency parallel connection of the inverters according to claim 1, wherein an input end of the first inverter is connected with a first direct current source; the input end of the second inverter is connected with a second direct current source;

or the like, or, alternatively,

8. The current sharing circuit for high-frequency parallel connection of the inverters according to claim 1, wherein the number of levels of the first inverter and the second inverter is N, and N is an integer greater than or equal to 2.

9. A current-sharing system for high-frequency parallel connection of inverters, comprising the current-sharing circuit for high-frequency parallel connection of inverters according to any one of claims 1 to 8, further comprising: a transmitting circuit and at least two of the following inverters: a first inverter and a second inverter;

10. The current sharing system for high-frequency parallel connection of inverters according to claim 9, wherein the transmitting circuit comprises: a transmit compensation network and a transmit coil;

11. The system according to claim 10, wherein the transmitting circuit transmits the ac power in an inductive coupling manner or in a transformer manner.

12. The system according to any one of claims 9 to 11, wherein the first inverter and the second inverter have the same structure.