CN216215912U

CN216215912U - Inverter and auxiliary power supply circuit thereof

Info

Publication number: CN216215912U
Application number: CN202122434130.4U
Authority: CN
Inventors: 李福印; 陈长春; 丁杰
Original assignee: Sungrow Power Supply Co Ltd
Current assignee: Sungrow Power Supply Co Ltd
Priority date: 2021-10-09
Filing date: 2021-10-09
Publication date: 2022-04-05
Anticipated expiration: 2031-10-09

Abstract

The utility model provides an inverter and an auxiliary power supply circuit thereof, wherein the auxiliary power supply circuit can take power from the alternating current side of the inverter through a second unit, and then output and provide auxiliary power supply through a third unit to realize the auxiliary power supply function; and moreover, the first unit can realize unidirectional conduction from the second unit to the direct-current bus of the inverter, and further can receive the output of the second unit and supply power to the direct-current bus so as to provide direct-current bus voltage when the inverter enters an SVG mode.

Description

Inverter and auxiliary power supply circuit thereof

Technical Field

The utility model relates to the technical field of inverters, in particular to an inverter and an auxiliary power supply circuit thereof.

Background

Electrical loads in the power grid, such as motors, transformers, etc., are mostly inductive loads, and during operation, corresponding reactive power needs to be provided to these devices. After reactive power compensation equipment such as a parallel capacitor is installed in the power grid, reactive power consumed by the inductive load can be provided, the reactive power supplied by the power supply of the power grid to the inductive load and transmitted by a line is reduced, and reactive power compensation is realized; however, the traditional capacitance compensation method needs to increase the investment of the reactive compensation device, and the realization cost is high.

Considering that an inverter of a photovoltaic system is in an idle state at night and a power grid has a reactive compensation requirement at night, the inverter can supplement reactive power for the power grid in real time when not generating power at night, and a Static Var Generator (SVG) function at night is realized; and a reactive power compensation device is not required to be added to the system, so that the cost is saved.

When the SVG function is realized at night, the inverter needs to be awakened, and the inverter is started, wherein the starting condition is that the direct-current bus voltage is established; under the condition of no photovoltaic input power at night, in order to meet the startup condition and enable the inverter to enter the SVG mode, a bus pre-charging circuit is required to be arranged in the prior art to convert electric energy received from a power grid and supply the converted voltage to a direct current bus of the inverter.

SUMMERY OF THE UTILITY MODEL

In view of the above, the present invention provides an inverter and an auxiliary power supply circuit thereof, which multiplex the auxiliary power supply circuit of the inverter to provide a dc bus voltage when entering the SVG mode, thereby eliminating a bus pre-charging circuit separately provided in the prior art.

In order to achieve the above purpose, the embodiments of the present invention provide the following technical solutions:

a first aspect of the present invention provides an auxiliary power supply circuit for an inverter, including: a first unit, a second unit, and a third unit; wherein:

the first end of the first unit is connected with a direct current bus of the inverter;

the input end of the second unit is connected with the alternating current side of the inverter;

the second end of the first unit is connected with the output end of the second unit, and the connecting point is connected with the input end of the third unit;

the output end of the third unit is used as the output end of the auxiliary power supply circuit;

the first unit can be conducted in one direction at least, and the conducting direction is as follows: from its second end to its first end.

Optionally, the first unit is a bidirectional conducting branch.

Optionally, the method further includes: and the power supply distribution module is connected between the output end of the third unit and the output end of the auxiliary power supply circuit.

Optionally, the second unit is an AC/DC conversion circuit.

Optionally, the first unit is a DC/DC conversion circuit.

Optionally, the third unit includes: a positive connection cable and a negative connection cable.

Optionally, the third unit further includes: the controllable switch is arranged on the positive connecting cable; and/or a controllable switch arranged on the negative connection cable;

and when the inverter enters an SVG mode and the voltage of a direct current bus of the inverter is less than a preset value, the controllable switch is in a disconnected state.

Optionally, the controllable switch is: an Insulated Gate Bipolar Transistor (IGBT), a Metal Oxide Semiconductor Field Effect Transistor (MOSFET), a relay, a contactor, or any combination of the IGBT and the MOSFET.

Optionally, the third unit is a DC/DC conversion circuit.

Optionally, the first unit includes: the positive pole is connected the cable way with the negative pole.

Optionally, the first unit further includes: the controllable switch is arranged on the positive connecting cable; and/or a controllable switch arranged on the negative connection cable.

Optionally, except that when the inverter enters the SVG mode and the dc bus voltage thereof is less than the preset value, the controllable switches are all in a unidirectional conduction state, and the power transmission direction of the first unit is: from the dc bus to the third cell.

A second aspect of the present invention provides an inverter, comprising: a DC/AC main power loop and an auxiliary power supply circuit for an inverter as described in any of the preceding paragraphs;

and the direct current side of the DC/AC main power loop is connected with a direct current bus.

Optionally, the method further includes: at least one DC/DC conversion circuit;

the DC/DC conversion circuit is connected with the direct current bus.

According to the auxiliary power supply circuit of the inverter, power can be taken from the alternating current side of the inverter through the second unit, and then output and auxiliary power supply are provided through the third unit, so that the auxiliary power supply function of the inverter is realized; and moreover, the first unit can realize unidirectional conduction from the second unit to the direct-current bus of the inverter, and further can receive the output of the second unit and supply power to the direct-current bus so as to provide direct-current bus voltage when the inverter enters an SVG mode.

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 obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

Fig. 1 is a schematic structural diagram of an auxiliary power supply circuit of an inverter according to an embodiment of the present invention;

fig. 2 is another schematic structural diagram of an auxiliary power supply circuit of an inverter according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of an auxiliary power supply circuit of an inverter according to an embodiment of the present invention;

fig. 4 is a schematic diagram of another specific structure of an auxiliary power supply circuit of an inverter according to an embodiment of the present invention;

FIG. 5 is a logic diagram illustrating operation of the auxiliary power circuit of FIG. 4 according to an embodiment of the present invention;

fig. 6 is a schematic diagram of another specific structure of an auxiliary power supply circuit of an inverter according to an embodiment of the present invention;

fig. 7 is a schematic diagram of another specific structure of the auxiliary power supply circuit of the inverter according to the embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In this application, 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 utility model provides an auxiliary power supply circuit of an inverter, which is used for multiplexing the auxiliary power supply circuit of the inverter to provide direct-current bus voltage when entering an SVG mode, and a bus pre-charging circuit which is independently arranged in the prior art is omitted.

Referring to fig. 1, the auxiliary power supply circuit of the inverter includes: a first unit 101, a second unit 102, and a third unit 103; wherein:

the first end of the first unit 101 is connected to a dc Bus (Bus + and Bus-as shown in the figure) of the inverter; specifically, the first terminal of the first unit 101 includes a positive electrode and a negative electrode, the positive electrode is connected to Bus +, and the negative electrode is connected to Bus-.

The input of the second unit 102 is connected to the ac side of the inverter (L1, L2, L3 as shown in the figure); in fig. 1, a three-phase inverter is illustrated as an example, in this case, two cables at the input end of the second unit 102 may be respectively connected to any two of L1, L2, and L3 shown in fig. 1, and in fig. 1, L1 and L2 are illustrated as an example, but are not limited thereto, and are within the scope of the present application depending on the specific application environment; for a single-phase inverter, two cables at the input end of the second unit 102 may be connected to the L-phase and the N-phase, respectively.

The second end of the first unit 101 is connected with the output end of the second unit 102, and the connection point is connected with the input end of the third unit 103; the second end of the first unit 101, the output end of the second unit 102 and the input end of the third unit 103 are all direct current sides, the anode of the second end of the first unit 101, the anode of the output end of the second unit 102 and the anode of the input end of the third unit 103 are connected, and the cathode of the second end of the first unit 101, the cathode of the output end of the second unit 102 and the cathode of the input end of the third unit 103 are connected.

The output terminal of the third unit 103 serves as the output terminal of the auxiliary power supply circuit to provide auxiliary power supply.

The first unit 101 can be at least unidirectionally conducted, and the conducting direction thereof is: from its second end to its first end, as indicated by the dashed arrow in fig. 1.

The specific working principle is as follows:

under normal conditions, the second unit 102 takes power from the ac side of the inverter, converts the power into dc power, and outputs the dc power through the third unit 103 to provide auxiliary power, thereby implementing the original auxiliary power supply function.

In addition, the first unit 101 can be conducted at least from the second end to the first end thereof, that is, the output power of the second unit 102 can be transmitted to the dc bus of the inverter; furthermore, when the inverter needs to enter the SVG mode, the output of the second unit 102 can be received through the first unit 101, and then the power is supplied to the direct current bus, so that the direct current bus voltage is provided, the inverter meets the startup condition of the night SVG function, the inverter enters the SVG mode, and the SVG function is realized.

This supplementary power supply circuit that this embodiment provided not only can realize its original supplementary power supply function, can also provide direct current bus voltage for it when the inverter gets into the SVG mode, has also had bus pre-charge circuit's among the prior art function promptly for need not to set up a bus pre-charge circuit alone again in the inverter, practiced thrift the construction cost of inverter.

In addition to the above embodiment, the first unit 101 is preferably a bidirectional conducting branch, that is, it can be conducted from the second end to the first end, and also from the first end to the second end.

Furthermore, in a normal state, the auxiliary power supply circuit can not only take power from the alternating current side of the inverter through the second unit 102, but also supply auxiliary power through the third unit 103; the first unit 101 can also get electricity from the direct current bus, and auxiliary power supply is provided through the third unit 103; that is, this auxiliary power supply circuit has set up two power supply sources, and both can supply power simultaneously, also can be redundant each other, lose auxiliary power supply when avoiding single power failure, improve auxiliary power supply's reliability.

In practical application, on the basis, the auxiliary power supply circuit can be additionally provided with: the power distribution module 104, as shown in fig. 2, the power distribution module 104 is connected between the output end of the third unit 103 and the output end of the auxiliary power supply circuit.

At this time, when the first unit 101 and the second unit 102 both output the electric energy to the third unit 103, the power distribution module 104 can distribute the output power of the first unit 101 and the second unit 102 through the logic process. For example, in the photovoltaic inverter system, when the output power of the photovoltaic module is large in the daytime, more or even all of the first unit 101 may provide the electric energy source for auxiliary power supply, so as to reduce the power of the second unit 102 that is taken from the ac side, reduce the power conversion link that generates the auxiliary power supply, and avoid the loss of the system power generation.

On the basis of the above embodiment, this embodiment provides a specific implementation form of the auxiliary power supply circuit, as shown in fig. 3 (which is illustrated on the basis of fig. 2), wherein:

the second unit 102 is an AC/DC conversion circuit and can convert AC power on the AC side of the inverter into DC power.

In this case, the AC/DC conversion circuit in the second unit 102 is preferably capable of directly converting the alternating current into the direct current with a voltage suitable for the auxiliary power supply application, and the third unit 103 may include only: the positive pole connecting cable and the negative pole connecting cable are connected without any conversion circuit.

The first unit 101 is a DC/DC conversion circuit, and can convert the DC power output by the second unit 102 into a suitable voltage to be supplied to the DC bus so as to satisfy the start-up condition; and as described in the previous embodiment, the DC/DC conversion circuit is preferably a bidirectional DC/DC conversion circuit, and is also capable of providing another source of electrical energy for auxiliary power supply.

In addition to the structure shown in fig. 3, it is more preferable that, as shown in fig. 4, the third unit 103 further includes: a controllable switch K1 arranged on the positive connection cable; and/or a controllable switch K2 arranged on the negative connecting cable. In fig. 4, the positive electrode and the negative electrode are provided with the corresponding controllable switches, and in practical application, only one of the positive electrode cables, preferably the positive electrode cable, may be provided with one controllable switch, so that the cost can be saved.

The controllable switches K1 and K2 are: any one of an IGBT, a MOSFET, a relay, a contactor, and a combination of an IGBT and a MOSFET; depending on the specific application environment, are all within the scope of the present application.

In fig. 4, when the inverter enters the SVG mode and the dc bus voltage thereof is less than the preset value, at least one of the controllable switches K1 and K2 is in an off state.

Taking a photovoltaic inverter system as an example, the specific working principle is as follows:

the DC/DC conversion circuit takes power from the DC bus in the daytime and outputs the power to the power distribution module 104. The AC/DC conversion circuit takes power from the grid and the output is also sent to the power distribution module 104. The output power of the two conversion circuits is logically distributed by the power distribution module 104.

The DC bus is not powered at night and the power distribution module 104 is powered only by the AC/DC converter circuit. The specific power range is determined by the logic of the power distribution module 104.

And when the direct current bus is not powered at night, after the SVG function is started by the inverter, at least one of the controllable switches K1 and K2 is disconnected, and the bidirectional DC/DC conversion circuit is controlled to charge the direct current bus through the loop (i). The purpose of turning off the controllable switch is to control the output power of the AC/DC conversion circuit to charge the DC bus preferentially in consideration of the design capacity of the AC/DC conversion circuit. When the voltage of the direct-current bus reaches a voltage threshold value required by the SVG starting condition, closing controllable switches K1 and K2, and operating the whole SVG; the operation logic is shown in fig. 5. At this time, the output power of the bidirectional DC/DC conversion circuit and the output power of the AC/DC conversion circuit are both provided to the power distribution module 104.

The inverter works in the SVG mode at night to support the voltage of a power grid, which is a common working requirement, the auxiliary power supply circuit provided by the embodiment can directly pre-charge the direct-current bus through the bidirectional DC/DC conversion circuit under the condition that the direct-current bus is not electrified, and the night SVG function is realized under the condition that an additional bus pre-charging circuit is not needed.

On the basis of the previous embodiment, this embodiment provides another specific implementation form of the auxiliary power supply circuit, as shown in fig. 6 (which is illustrated on the basis of fig. 2), where:

the second unit 102 is an AC/DC conversion circuit, which can convert AC power at the AC side of the inverter into DC power, and the DC side of the inverter can output a voltage level close to the DC bus voltage.

At this time, the third unit 103 is a DC/DC conversion circuit to convert a higher voltage output from the AC/DC conversion circuit into a voltage suitable for an auxiliary power supply application.

Since the AC/DC conversion circuit can output a voltage similar to a DC bus voltage, the first unit 101 may include only: the positive pole is connected the cable way with the negative pole connection cable way, can realize two-way switching on.

Still take a photovoltaic inverter system as an example, the specific working principle is as follows:

the DC/DC conversion circuit in the third unit 103 in daytime can directly take power from the DC bus and output the power to the power distribution module 104. The AC/DC conversion circuit takes power from the power grid, and the output power is converted by the DC/DC conversion circuit and then sent to the power distribution module 104. The power supply distribution module 104 determines the output power of the two conversion circuits logically, and indirectly controls the power taken from the direct current bus.

At night, the direct current bus is not powered, and the power supply distribution module 104 is powered by the third unit 103 through the AC/DC conversion circuit. The specific power range is determined by the logic of the power distribution module 104.

When the DC bus is not powered at night, the inverter turns on the SVG function, and then first controls the DC/DC conversion circuit in the third unit 103 to stop operating, and controls all the output power of the AC/DC conversion circuit to be charged to the DC bus via the loop (i). Of course, the DC/DC converter circuit may maintain output, but output power is low, and the power supply range is small, so that the DC bus is charged with priority. When the voltage of the direct current bus reaches a voltage threshold value required by the starting condition of the SVG, the DC/DC conversion circuit in the third unit 103 outputs normally, and the whole SVG operates. At this time, the output power of the DC bus and the AC/DC conversion circuit are both provided to the power distribution module 104.

On the basis of fig. 6, it is more preferable, referring to fig. 7, that the first unit 101 further includes: a controllable switch K3 arranged on the positive connection cable; and/or a controllable switch K4 arranged on the negative connecting cable. In fig. 7, it is shown that the positive electrode and the negative electrode are provided with the corresponding controllable switches, in practical application, only one of the positive electrode cables, preferably the positive electrode cable, may be provided with one controllable switch, so that the cost can be saved.

The controllable switches K3 and K4 are: any one of an IGBT, a MOSFET, a relay, a contactor, and a combination of an IGBT and a MOSFET; depending on the specific application environment, are all within the scope of the present application.

In fig. 7, when the inverter enters the SVG mode and the DC bus voltage is less than the predetermined value, since the DC bus voltage is lower than the output voltage of the AC/DC conversion circuit, even though the first unit 101 is bidirectionally conductive, the power transmission is performed in the direction of the loop (i). And except when the inverter enters the SVG mode and the dc bus voltage thereof is less than the preset value, the controllable switches K3 and K4 are preferably in a unidirectional conducting state, and the power transmission direction of the first unit 101 at this time is: from the dc bus to the third unit 103, the ac side is prevented from transmitting electric energy to the dc bus as much as possible, and the power generation efficiency of the system is improved.

Another embodiment of the present application also provides an inverter, as shown in fig. 1 to 7, including: a DC/AC main power loop and an auxiliary power supply circuit for an inverter as described in any of the above embodiments; the structure and the working principle of the auxiliary power supply circuit can be obtained by referring to the above embodiments, and are not described in detail.

The DC side of the DC/AC main power loop is connected to a DC bus.

In practical applications, the front stage of the DC/AC main power loop may be further provided with: at least one DC/DC conversion circuit; the DC/DC conversion circuit is connected with the DC bus.

In addition, the direct current side of the inverter can receive the electric energy of the photovoltaic array and also can receive the electric energy of the battery system, and the direct current side of the inverter is determined according to the specific application environment and is within the protection scope of the application.

The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, the system or system embodiments are substantially similar to the method embodiments and therefore are described in a relatively simple manner, and reference may be made to some of the descriptions of the method embodiments for related points. The above-described system and system embodiments are only illustrative, wherein the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.

Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

In the above description of the disclosed embodiments, the features described in the embodiments in this specification may be replaced or combined with each other to enable those skilled in the art to make or use the utility model. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the utility model. Thus, the present invention 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.

Claims

1. An auxiliary power supply circuit for an inverter, comprising: a first unit, a second unit, and a third unit; wherein:

2. The auxiliary power supply circuit of an inverter according to claim 1, wherein the first unit is a bidirectional conducting branch.

3. The auxiliary power supply circuit for an inverter according to claim 2, further comprising: and the power supply distribution module is connected between the output end of the third unit and the output end of the auxiliary power supply circuit.

4. An auxiliary power supply circuit for an inverter according to any of claims 1 to 3, wherein said second unit is an AC/DC converter circuit.

5. The auxiliary power supply circuit of the inverter according to claim 4, wherein the first unit is a DC/DC conversion circuit.

6. The auxiliary power supply circuit of the inverter according to claim 5, wherein the third unit comprises: a positive connection cable and a negative connection cable.

7. The auxiliary power supply circuit of the inverter according to claim 6, further comprising in the third unit: the controllable switch is arranged on the positive connecting cable; and/or a controllable switch arranged on the negative connection cable;

8. Auxiliary supply circuit for an inverter according to claim 7, characterized in that the controllable switches are: an Insulated Gate Bipolar Transistor (IGBT), a Metal Oxide Semiconductor Field Effect Transistor (MOSFET), a relay, a contactor, or any combination of the IGBT and the MOSFET.

9. The auxiliary power supply circuit of the inverter according to claim 4, wherein the third unit is a DC/DC conversion circuit.

10. The auxiliary power supply circuit of the inverter according to claim 9, wherein the first unit includes: the positive pole is connected the cable way with the negative pole.

11. The auxiliary power supply circuit of the inverter according to claim 10, further comprising in the first unit: the controllable switch is arranged on the positive connecting cable; and/or a controllable switch arranged on the negative connection cable.

12. The auxiliary power supply circuit of the inverter according to claim 11, wherein the controllable switches are in a one-way conduction state except when the inverter enters the SVG mode and the dc bus voltage of the inverter is smaller than a preset value, and the power transmission direction of the first unit is: from the dc bus to the third cell.

13. An inverter, comprising: a DC/AC main power loop and an auxiliary power supply circuit of an inverter as claimed in any one of claims 1 to 12;

14. The inverter of claim 13, further comprising: at least one DC/DC conversion circuit;

the DC/DC conversion circuit is connected with the direct current bus.