阅读说明：本技术 一种基于耦合变压器的逆变电路 (Inverter circuit based on coupling transformer ) 是由 崔彬 余仕君 胡小明 肖旭潘 于 2021-02-01 设计创作，主要内容包括：本发明提供一种基于耦合变压器的逆变电路,包括正母线、负母钱、第一开关桥臂、第二开关桥臂、耦合变压器及耦合电感,其中,第一开关桥臂和第二开关桥臂并联在正母线和负母钱之间,耦合变压器与耦合电感串联以构成磁性元器件,磁性元器件一端连接于第一开关桥臂和第二开关桥臂的桥臂中点,磁性元器件另一端用于连接交流电网或交流电压源或负载,耦合变压器在耦合变压器的磁芯上的耦合方式为反向耦合,耦合电感在耦合电感的磁芯上的耦合方式为正向耦合,第一开关桥臂的驱动脉冲的相位与第二开关桥臂的驱动脉冲的相位相差180度。本发明能够大幅度减小了磁性元器件的体积,进而降低了磁性元器件的损耗和成本,提升了整机的效率。(The invention provides an inverter circuit based on a coupling transformer, which comprises a positive bus, a negative bus, a first switch bridge arm, a second switch bridge arm, a coupling transformer and a coupling inductor, wherein the first switch bridge arm and the second switch bridge arm are connected in parallel between the positive bus and the negative bus, the coupling transformer and the coupling inductor are connected in series to form a magnetic component, one end of the magnetic component is connected to the middle point of the bridge arms of the first switch bridge arm and the second switch bridge arm, the other end of the magnetic component is used for connecting an alternating current power grid or an alternating current voltage source or a load, the coupling mode of the coupling transformer on a magnetic core of the coupling transformer is reverse coupling, the coupling mode of the coupling inductor on the magnetic core of the coupling inductor is forward coupling, and the phase difference between the driving pulse of the first switch bridge arm and the driving pulse of the second switch bridge arm is. The invention can greatly reduce the volume of the magnetic component, further reduce the loss and the cost of the magnetic component and improve the efficiency of the whole machine.)

1. An inverter circuit based on a coupling transformer, comprising: the circuit comprises a positive bus, negative bus bars, a first switch bridge arm, a second switch bridge arm, a coupling transformer and a coupling inductor, wherein the first switch bridge arm and the second switch bridge arm are connected between the positive bus and the negative bus bars in parallel, the coupling transformer is connected with the coupling inductor in series to form a magnetic component, one end of the magnetic component is connected to the middle point of the bridge arms of the first switch bridge arm and the second switch bridge arm, and the other end of the magnetic component is used for connecting an alternating current power grid or an alternating current voltage source or a load;

the coupling mode of the coupling transformer on the magnetic core of the coupling transformer is reverse coupling, the coupling mode of the coupling inductor on the magnetic core of the coupling inductor is forward coupling, and the phase difference between the driving pulse of the first switch bridge arm and the driving pulse of the second switch bridge arm is 180 degrees.

2. The coupling transformer-based inverter circuit according to claim 1, wherein one end of a primary winding of the coupling transformer is connected to a bridge arm midpoint of the first switching bridge arm, the other end of the primary winding of the coupling transformer is connected to one end of a primary winding of the coupling inductor, one end of a secondary winding of the coupling transformer is connected to a bridge arm midpoint of the second switching bridge arm, the other end of the secondary winding of the coupling transformer is connected to one end of a secondary winding of the coupling inductor, and a common junction of the other end of the primary winding of the coupling inductor and the other end of the secondary winding is used for connecting an ac power grid or an ac voltage source or a load.

3. The coupling transformer-based inverter circuit according to claim 1, wherein one end of a primary winding of the coupling inductor is connected to a bridge arm midpoint of the first switching bridge arm, the other end of the primary winding of the coupling inductor is connected to one end of a primary winding of the coupling transformer, one end of a secondary winding of the coupling inductor is connected to a bridge arm midpoint of the second switching bridge arm, the other end of the secondary winding of the coupling inductor is connected to one end of a secondary winding of the coupling transformer, and a common junction of the other end of the primary winding of the coupling transformer and the other end of the secondary winding is used for connecting an ac power grid or an ac voltage source or a load.

4. The coupling transformer based inverter circuit according to claim 1, wherein the first switching leg comprises two first switching tubes, and the two first switching tubes are connected in series to form the first switching leg;

the second switch bridge arm comprises two second switch tubes which are connected in series to form the second switch bridge arm;

the first switch tube and the second switch tube send the driving pulse in a PWM (pulse width modulation) sine pulse width modulation mode.

5. The coupling transformer based inverter circuit according to claim 4, wherein the first switching tube is any one or a combination of a metal-oxide semiconductor field effect transistor, an insulated gate bipolar transistor and a silicon controlled rectifier;

the second switch tube is any one or a combination of a plurality of metal-oxide semiconductor field effect transistors, insulated gate bipolar transistors and silicon controlled rectifiers.

6. The coupling transformer-based inverter circuit according to claim 1, wherein the coupling transformer core is a high frequency soft magnetic core, the high frequency soft magnetic core comprising any one of a ferrite core, an amorphous alloy core, and an oriented silicon steel core.

7. The coupling transformer-based inverter circuit according to claim 1, wherein the core of the coupling inductor is a high-frequency soft magnetic core having an air gap, and the high-frequency soft magnetic core having an air gap comprises any one of a ferrosilicon core, a ferrosilicoaluminum core, and a ferropowder core.

8. The coupling transformer based inverter circuit according to claim 1, wherein a turn ratio of a primary winding to a secondary winding of the coupling transformer is N: N, where N is a positive integer.

9. The coupling transformer based inverter circuit according to claim 1, wherein a turn ratio of a primary winding to a secondary winding of the coupling inductor is M: M, wherein M is a positive integer.

10. The coupling transformer based inverter circuit of claim 1, further comprising: the high-voltage direct-current power supply comprises a battery pack, a first capacitor, a second capacitor, a third capacitor and a zero potential node, wherein the positive electrode of the battery pack is connected to the positive bus, the negative electrode of the battery pack is connected to the negative bus, the first capacitor is connected with the second capacitor in series to form a series branch, the series branch is connected between the positive bus and the negative bus and is respectively connected with the battery pack, the first switch bridge arm and the second switch bridge arm in parallel, the common connection point of the first capacitor and the second capacitor and one end of the third capacitor are respectively connected to the zero potential node, and the other end of the third capacitor is connected to one end of the magnetic component, which is used for connecting an alternating-current power grid or an alternating-current voltage source or a load.

Technical Field

The present disclosure relates to inverter circuits, and particularly to an inverter circuit based on a coupling transformer.

Background

An Inverter Circuit (Inverter Circuit) corresponds to a Rectifier Circuit (Rectifier Circuit), which is intended to convert direct current into alternating current. In recent years, inverter circuits have been widely used in industry, and among them, half-bridge inverter circuits are most prominently used in dc to ac power supplies.

In the prior art, a half-bridge inverter circuit mainly comprises a switch branch serving as a bridge arm and an inductor serving as a magnetic component and connected with the switch branch, and when the power of the half-bridge inverter circuit is large (such as larger than 20 KW), the size of the inductor is large, so that the loss and cost of the magnetic component are high, and the efficiency of the whole inverter is not ideal. In order to solve the above-mentioned problem that exists among the half-bridge inverter circuit, research and development personnel try to change half-bridge inverter circuit's structure, split into two crisscross and parallelly connected two way switch branch roads with original switch branch road all the way, increase another inductance on original an inductance's basis simultaneously, however, research and development personnel discover that the total volume of two inductances in the half-bridge inverter circuit after the change is still great, magnetic component's loss, the cost and the loss of the magnetic component among the half-bridge inverter circuit before the change, the cost differs a little, the efficiency of whole machine is still unsatisfactory.

Therefore, it is necessary to improve the structure of the inverter circuit.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the inverter circuit based on the coupling transformer solves the problem that in the prior art, the overall efficiency is low due to the fact that loss and cost of magnetic components are high.

In order to solve the technical problems, the invention adopts the technical scheme that:

the embodiment of the invention provides an inverter circuit based on a coupling transformer, which comprises: the circuit comprises a positive bus, negative bus bars, a first switch bridge arm, a second switch bridge arm, a coupling transformer and a coupling inductor, wherein the first switch bridge arm and the second switch bridge arm are connected between the positive bus and the negative bus bars in parallel, the coupling transformer is connected with the coupling inductor in series to form a magnetic component, one end of the magnetic component is connected to the middle point of the bridge arms of the first switch bridge arm and the second switch bridge arm, and the other end of the magnetic component is used for connecting an alternating current power grid or an alternating current voltage source or a load;

the coupling mode of the coupling transformer on the magnetic core of the coupling transformer is reverse coupling, the coupling mode of the coupling inductor on the magnetic core of the coupling inductor is forward coupling, and the phase difference between the driving pulse of the first switch bridge arm and the driving pulse of the second switch bridge arm is 180 degrees.

In some embodiments, one end of a primary winding of the coupling transformer is connected to a middle point of a bridge arm of the first switching bridge arm, the other end of the primary winding of the coupling transformer is connected to one end of a primary winding of the coupling inductor, one end of a secondary winding of the coupling transformer is connected to a middle point of a bridge arm of the second switching bridge arm, the other end of the secondary winding of the coupling transformer is connected to one end of a secondary winding of the coupling inductor, and a common connection point between the other end of the primary winding of the coupling inductor and the other end of the secondary winding is used for connecting an ac power grid or an ac voltage source or a load.

In some embodiments, one end of a primary winding of the coupling inductor is connected to a middle point of a bridge arm of the first switching bridge arm, the other end of the primary winding of the coupling inductor is connected to one end of a primary winding of the coupling transformer, one end of a secondary winding of the coupling inductor is connected to a middle point of a bridge arm of the second switching bridge arm, the other end of the secondary winding of the coupling inductor is connected to one end of a secondary winding of the coupling transformer, and a common connection point between the other end of the primary winding and the other end of the secondary winding of the coupling transformer is used for connecting an ac power grid or an ac voltage source or a load.

In some embodiments, the first switch bridge arm comprises two first switch tubes, and the two first switch tubes are connected in series to form the first switch bridge arm;

the second switch bridge arm comprises two second switch tubes which are connected in series to form the second switch bridge arm;

the first switch tube and the second switch tube send the driving pulse in a PWM (pulse width modulation) sine pulse width modulation mode.

In some embodiments, the first switching tube is any one of or a combination of a metal-oxide semiconductor field effect transistor, an insulated gate bipolar transistor and a silicon controlled rectifier;

the second switch tube is any one or a combination of a plurality of metal-oxide semiconductor field effect transistors, insulated gate bipolar transistors and silicon controlled rectifiers.

In some embodiments, the core of the coupling transformer is a high frequency soft magnetic core including any one of a ferrite core, an amorphous alloy core, and an oriented silicon steel core.

In some embodiments, the magnetic core of the coupling inductor is a high-frequency soft magnetic core with an air gap, and the high-frequency soft magnetic core with an air gap includes any one of a ferrosilicon powder core, a ferrosilicon-aluminum powder core, and a ferropowder core.

In some embodiments, the primary winding and the secondary winding of the coupling transformer have a turn ratio of N: N, where N is a positive integer.

In some embodiments, the turn ratio of the primary winding to the secondary winding of the coupled inductor is M: M, where M is a positive integer.

In some embodiments, the coupling transformer based inverter circuit further comprises: the high-voltage direct-current power supply comprises a battery pack, a first capacitor, a second capacitor, a third capacitor and a zero potential node, wherein the positive electrode of the battery pack is connected to the positive bus, the negative electrode of the battery pack is connected to the negative bus, the first capacitor is connected with the second capacitor in series to form a series branch, the series branch is connected between the positive bus and the negative bus and is respectively connected with the battery pack, the first switch bridge arm and the second switch bridge arm in parallel, the common connection point of the first capacitor and the second capacitor and one end of the third capacitor are respectively connected to the zero potential node, and the other end of the third capacitor is connected to one end of the magnetic component, which is used for connecting an alternating-current power grid or an alternating-current voltage source or a load.

From the above description, compared with the prior art, the invention has the following beneficial effects:

the magnetic component is composed of a coupling transformer and a coupling inductor which are connected in series, wherein the coupling mode of the coupling transformer on a magnetic core of the coupling transformer is reverse coupling, and the coupling mode of the coupling inductor on the magnetic core of the coupling inductor is forward coupling, so that the inductance of the coupling inductor is greatly reduced, the volume of the magnetic component is greatly reduced, the loss and the cost of the magnetic component are reduced, and the efficiency of the whole machine is improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It is to be understood that the drawings in the following description are of some, but not all, embodiments of the invention. For a person skilled in the art, other figures can also be obtained from the provided figures without inventive effort.

Fig. 1 is a schematic circuit diagram of an inverter circuit based on a coupling transformer according to an embodiment of the present invention;

fig. 2 is a schematic circuit diagram of another circuit structure of an inverter circuit based on a coupling transformer according to an embodiment of the present invention;

fig. 3 is a voltage waveform diagram of a connection point of a coupling transformer and a coupling inductor to a zero potential node according to an embodiment of the present invention;

fig. 4 is a voltage waveform diagram of one winding of the coupled inductor according to the embodiment of the present invention.

Detailed Description

For purposes of promoting a clear understanding of the objects, aspects and advantages of the invention, reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements throughout. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Referring to fig. 1, fig. 1 is a schematic circuit structure diagram of an inverter circuit based on a coupling transformer according to an embodiment of the present invention.

As shown in fig. 1, an embodiment of the present invention provides an inverter circuit based on a coupling transformer, including a positive BUS +, a negative BUS, a first switch leg X, a second switch leg Y, a coupling transformer T1, and a coupling inductor L1, where the first switch leg X and the second switch leg Y are connected in parallel between the positive BUS + and the negative BUS, the coupling transformer T1 is connected in series with the coupling inductor L1 to form a magnetic device, one end of the magnetic device is connected to bridge arm midpoints (a and B) of the first switch leg X and the second switch leg Y, and the other end of the magnetic device is used for connecting an ac power grid, an ac voltage source, or a load. It should be noted that the inverter circuit based on the coupling transformer provided in the embodiment of the present invention is a circuit that can be connected to a grid or disconnected from the grid, and when the other end of the magnetic component is connected to an ac grid, it is usually necessary to connect some EMC filter circuits, such as a common mode inductor, an ac capacitor, etc., or to further include components such as a relay and a fuse.

Specifically, the turn ratio of the primary winding to the secondary winding of the coupling transformer T1 is N: N (N is a positive integer), and the coupling mode of the coupling transformer T1 on the magnetic core of the coupling transformer T1 is reverse coupling, that is, the magnetic fluxes generated by i1 and i2 on the magnetic core of the coupling transformer T1 are cancelled out with the currents i1 and i2 as positive directions; the turn ratio of the primary winding to the secondary winding of the coupling inductor L1 is M: M (M is a positive integer), and the coupling mode of the coupling inductor L1 on the magnetic core of the coupling inductor L1 is forward coupling, that is, the magnetic fluxes generated by i1 and i2 on the magnetic core of the coupling inductor L1 are mutually strengthened by taking the currents i1 and i2 as positive directions.

It should be noted that the core of the coupling transformer T1 is a high-frequency soft magnetic core such as a ferrite core. Of course, the core of the coupling transformer T1 is not limited to be ferrite, and in other embodiments, the core of the coupling transformer T1 may be any one of an amorphous alloy core and an oriented silicon steel core, or other high-frequency soft magnetic core, which is not limited in this embodiment of the present invention.

More specifically, the phase difference between the driving pulse of the first switching leg X and the driving pulse of the second switching leg Y is 180 degrees, that is, the driving pulse of the first switching leg X and the driving pulse of the second switching leg Y are staggered by 180 degrees, and at this time, alternating three-level voltages are generated at the leg middle point a of the first switching leg X and the leg middle point B of the second switching leg Y. Therefore, in practical application, the first switch leg X and the second switch leg Y transmit driving pulses to the magnetic component formed by the coupling transformer T1 and the coupling inductor L1 connected in series in an interleaving manner.

It should be noted that the magnetic core of the coupling inductor L1 is a high-frequency soft magnetic core with an air gap, such as a ferrite core. Of course, the magnetic core of the coupling inductor L1 is not limited to be made of iron silicon powder, and in other embodiments, the magnetic core of the coupling inductor L1 may be made of any one of iron silicon powder core and iron powder core, or other forms of high-frequency soft magnetic cores with air gaps. In essence, high-frequency soft magnetic cores such as ferrite cores, amorphous alloy cores and oriented silicon steel cores can be used as the cores of the coupling inductor L1, but in this case, an air gap needs to be added to the magnetic path of the core of the coupling inductor L1. It should be understood that the specific form of the magnetic core of the coupling inductor L1 is determined according to the practical application scenario, and the embodiment of the present invention is not limited thereto.

The inverter circuit based on the coupling transformer provided by the embodiment of the invention adopts two parallel-connected switch bridge arms of a first switch bridge arm X and a second switch bridge arm Y, and the phase difference between the driving pulse of the first switch bridge arm X and the driving pulse of the second switch bridge arm Y is 180 degrees, namely the first switch bridge arm X and the second switch bridge arm Y send the driving pulse to the magnetic component in a staggered manner, and the magnetic component is composed of a coupling transformer T1 and a coupling inductor L1 which are connected in series, in the magnetic component, the coupling mode of the coupling transformer T1 on the magnetic core of the coupling transformer T1 is reverse coupling, the coupling mode of the coupling inductor L1 on the magnetic core of the coupling inductor L1 is forward coupling, so that the inductance of the coupling inductor L1 is greatly reduced, the volume of the magnetic component is greatly reduced, and the loss and the cost of the magnetic component are further reduced, the efficiency of the complete machine is improved.

Referring to fig. 2, fig. 3 and fig. 4, fig. 2 is a schematic diagram of another circuit structure of the inverter circuit based on the coupling transformer according to the embodiment of the present invention, fig. 3 is a voltage waveform diagram of a connection point of the coupling transformer and the coupling inductor according to the embodiment of the present invention with respect to a zero potential node, and fig. 4 is a voltage waveform diagram of one winding of the coupling inductor according to the embodiment of the present invention.

As a possible implementation, as shown in fig. 2, first switching leg X may include two first switching tubes Q1 and Q2, two first switching tubes Q1 and Q2 connected in series to form first switching leg X, and second switching leg Y may also include two second switching tubes Q3 and Q4, two second switching tubes Q3 and Q4 connected in series to form second switching leg Y.

Specifically, in the process of sending the driving pulse to the magnetic component in the first switch bridge arm X and the second switch bridge arm Y in a staggered manner, the two first switch tubes Q1 and Q2 in the first switch bridge arm X and the two second switch tubes Q3 and Q4 in the second switch bridge arm Y may both send the driving pulse in a PWM sine pulse width modulation manner, for example, send the driving pulse in a PWM sine pulse width modulation manner of a conventional half-bridge inverter circuit.

More specifically, each of the two first switching transistors Q1 and Q2 in the first switching leg X and each of the two second switching transistors Q3 and Q4 in the second switching leg Y may be a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET). Of course, any one of the two first switching tubes Q1 and Q2 in the first switching leg X and the two second switching tubes Q3 and Q4 in the second switching leg Y is not limited to the MOSFET, and in other embodiments, any one of an Insulated Gate Bipolar Transistor (IGBT) and a Silicon Controlled Rectifier (SCR), other similar components, or a combination of some other components may be used. It should be understood that what type of switching tube is specifically adopted by the two first switching tubes Q1 and Q2 in the first switching leg X and the two second switching tubes Q3 and Q4 in the second switching leg Y is determined according to an actual application scenario, and this is not limited in the embodiment of the present invention.

Further, as shown in fig. 2, the inverter circuit based on the coupling transformer according to the embodiment of the present invention may further include a battery DC, a first capacitor Cp, a second capacitor Cn, a third capacitor C1, and a zero potential node N, wherein an anode of the battery DC is connected to the positive BUS +, a cathode of the battery DC is connected to the negative BUS-, the first capacitor Cp is connected in series with the second capacitor Cn to form a series branch, the series branch is connected between the positive BUS + and the negative BUS-and is respectively connected in parallel with the battery DC, the first switch arm X, and the second switch arm Y, a common node of the first capacitor Cp and the second capacitor Cn, and one end of the third capacitor C1 are respectively connected to the zero potential node N, and the other end of the third capacitor N is connected to one end of the magnetic component for connecting to the ac power grid, the ac voltage source, or the load.

On the basis, a series of experiments show that the waveform of the voltage of the coupling transformer T1 is a high-frequency alternating waveform, the variation frequency of the high-frequency alternating waveform is the switching frequency fs of the two first switching tubes Q1 and Q2 in the first switching leg X and any one of the two second switching tubes Q3 and Q4 in the second switching leg Y, the amplitude is approximately ± Vbus, and when the time is 0 to 10ms, the effective duty cycle of the waveform of the voltage of the coupling transformer T1 is reduced from 50% to the minimum value, and then is increased from the minimum value to 50%, and at this time, the waveform of the voltage of the coupling transformer T1 is periodically changed with 10ms as a period.

Due to the characteristics of the waveform of the voltage of the coupling transformer T1, the coupling transformer-based inverter circuit provided by the embodiment of the present invention has some beneficial changes, especially in terms of the voltage waveform of the coupling inductor L1: the frequency of the voltage of the coupling inductor L1 is increased by one time relative to the switching frequency fs of any one of the two first switching tubes Q1 and Q2 in the first switching leg X and the two second switching tubes Q3 and Q4 in the second switching leg Y; compared with a traditional half-bridge inverter circuit, the waveform of the voltage of the coupling inductor L1 is changed into a three-level voltage waveform from a two-level voltage waveform; and the currents in the first switch bridge arm X and the second switch bridge arm Y are naturally equalized. Due to the beneficial changes, under the condition that the switching frequencies fs of the two first switching tubes Q1 and Q2 in the first switching bridge arm X and the two second switching tubes Q3 and Q4 in the second switching bridge arm Y are not changed, the inductance of the coupling inductor L1 is greatly reduced compared with a traditional half-bridge inverter circuit, so that the size of a magnetic component is greatly reduced, the loss and the cost of the magnetic component are further reduced, and the efficiency of the whole machine is improved. These beneficial variations can also be demonstrated from fig. 3 and 4.

In addition, in the above magnetic component, the coupling inductor L1 may be connected to the coupling transformer T1, and then the coupling transformer T1 is connected to the first switching leg X and the second switching leg Y, at this time, one end of the primary winding of the coupling transformer T1 is connected to the leg midpoint a of the first switching leg X, the other end of the primary winding of the coupling transformer T1 is connected to one end of the primary winding of the coupling inductor L1, one end of the secondary winding of the coupling transformer T1 is connected to the leg midpoint B of the second switching leg Y, the other end of the secondary winding of the coupling transformer T1 is connected to one end of the secondary winding of the coupling inductor L1, and a common junction between the other end of the primary winding of the coupling inductor L1 and the other end of the secondary winding is used for connecting an ac power grid or an ac voltage.

Specifically, when the coupling transformer T1 is directly connected to the first switching leg X and the second switching leg Y, the dotted end of the primary winding of the coupling transformer T1 is connected to the leg midpoint a of the first switching leg X, the dotted end of the primary winding of the coupling transformer T1 is connected to the dotted end of the primary winding of the coupling inductor L1, the dotted end of the secondary winding of the coupling transformer T1 is connected to the leg midpoint B of the second switching leg Y, the dotted end of the secondary winding of the coupling transformer T1 is connected to the dotted end of the secondary winding of the coupling inductor L1, and a common connection point of the secondary winding of the coupling inductor L1 and the dotted end of the primary winding is used for connecting an ac power grid or an ac voltage source or a load.

Of course, the connection of coupling inductor L1 and coupling transformer T1 to first switch leg X and second switch leg Y is not limited to the above-described form, in other embodiments, coupling transformer T1 may be connected to first switch leg X and second switch leg Y via coupling inductor L1 after coupling inductor L1 is connected, and at this time, one end of a primary winding of the coupling inductor L1 is connected to a bridge arm midpoint A of the first switch bridge arm X, the other end of the primary winding of the coupling inductor L1 is connected to one end of a primary winding of the coupling transformer T1, one end of a secondary winding of the coupling inductor L1 is connected to a bridge arm midpoint B of the second switch bridge arm Y, the other end of a secondary winding of the coupling inductor L1 is connected to one end of a secondary winding of the coupling transformer T1, and a common joint of the other end of the primary winding of the coupling transformer T1 and the other end of the secondary winding is used for connecting an alternating current power grid or an alternating current voltage.

Specifically, when the coupling inductor L1 is directly connected to the first switching leg X and the second switching leg Y, the synonym end of the primary winding of the coupling inductor L1 is connected to the leg midpoint a of the first switching leg X, the synonym end of the primary winding of the coupling inductor L1 is connected to the synonym end of the primary winding of the coupling transformer T1, the synonym end of the secondary winding of the coupling inductor L1 is connected to the leg midpoint B of the second switching leg Y, the synonym end of the secondary winding of the coupling inductor L1 is connected to the synonym end of the secondary winding of the coupling transformer T1, and a common contact of the synonym end of the primary winding of the coupling transformer T1 and the synonym end of the secondary winding is used for connecting an ac power grid or an ac voltage source or a load.

It should be understood that the specific connection form of the coupling inductor L1 and the coupling transformer T1 with the first switch leg X and the second switch leg Y is determined according to an actual application scenario, and this is not limited in the embodiment of the present invention.

It should be noted that, in the summary of the present invention, each embodiment is described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments may be referred to each other.

It is further noted that, in the present disclosure, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined in this disclosure may be applied to other embodiments without departing from the spirit or scope of the disclosure. Thus, the present disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.