CN117375448A

CN117375448A - Inverter and control method

Info

Publication number: CN117375448A
Application number: CN202311592069.3A
Authority: CN
Inventors: 徐安安; 汪昌友; 孙维
Original assignee: Sungrow Power Supply Co Ltd
Current assignee: Sungrow Power Supply Co Ltd
Priority date: 2023-11-23
Filing date: 2023-11-23
Publication date: 2024-01-09

Abstract

The application discloses an inverter and a control method, the inverter includes: the switching device comprises an inverter circuit, an electrolytic capacitor, a switching switch and a film capacitor; the membrane capacitor is connected in parallel between the positive input end and the negative input end of the inverter circuit, and the electrolytic capacitor and the switching switch are connected in series and then connected in parallel at two ends of the membrane capacitor; the inverter realizes the input or the cut-off of at least part of the electrolytic capacitor by controlling the state of the switching switch according to the output reactive power. In order to improve the service life of the electrolytic capacitor, the electrolytic capacitor is connected into a circuit when needed, and the electrolytic capacitor is disconnected from the circuit when not needed. For example, most of the working scenes of the inverter are in full active state, namely, when reactive power is not output, so that no electrolytic capacitor is needed to participate in the working, or only a small amount of electrolytic capacitors are needed to participate in the working. When the inverter needs to output reactive power or is in transient state excessive working condition, all or part of electrolytic capacitors are put into operation. Wherein, the excessive suspension includes, but is not limited to, the situation that the power grid is over-voltage, under-voltage and the like.

Description

Inverter and control method

Technical Field

The application relates to the technical field of power electronics, in particular to an inverter and a control method.

Background

At present, a direct current bus capacitor connected with an input end of an inverter circuit in an inverter comprises a film capacitor, an electrolytic capacitor and an inhibition inductor, wherein the film capacitor is generally connected between a positive input end and a negative input end of the inverter circuit in parallel, and the electrolytic capacitor and the inhibition inductor are connected in series and then connected at two ends of the film capacitor in parallel.

When the inverter works, the electrolytic capacitor can always participate in the work, and the service life of the electrolytic capacitor can be reduced due to longer working time of the electrolytic capacitor.

Disclosure of Invention

In view of the above, the present application provides an inverter and a control method capable of improving the lifetime of an electrolytic capacitor.

The application provides an inverter, comprising: the switching device comprises an inverter circuit, an electrolytic capacitor, a switching switch and a film capacitor;

the membrane capacitor is connected in parallel between the positive input end and the negative input end of the inverter circuit, and the electrolytic capacitor and the switching switch are connected in series and then connected in parallel at two ends of the membrane capacitor;

and the inverter realizes the input or the cutting off of at least part of the electrolytic capacitor by controlling the state of the switching switch according to the output reactive power.

Preferably, the method further comprises: a controller and a suppression inductor; the electrolytic capacitor and the suppression inductor are connected in series and then connected in parallel at two ends of the membrane capacitor;

the electrolytic capacitor is connected with the suppression inductor through the switching switch;

the controller is used for controlling the switching switch to be switched off when the inverter works without outputting reactive power; and when the inverter works in a reactive power output or transient transition state, the switching switch is controlled to be closed.

Preferably, the electrolytic capacitor corresponds to the following two switching switches: the first switching switch and the second switching switch, the suppression inductance includes the following two: a first suppression inductance and a second suppression inductance;

the first end of the electrolytic capacitor is connected with the first suppression inductor through the first switching switch; the second end of the first suppression inductor is connected with the first end of the film capacitor;

the second end of the electrolytic capacitor is connected with a second suppression inductor through a second switching switch; the second end of the second suppression inductor is connected with the second end of the film capacitor.

Preferably, the electrolytic capacitor comprises at least two of: a first electrolytic capacitor and a second electrolytic capacitor; the first electrolytic capacitor corresponds to the first switching switch and the second switching switch, and the second electrolytic capacitor corresponds to the third switching switch and the fourth switching switch; the suppression inductance includes two of the following: a first suppression inductance and a second suppression inductance;

the first end of the first electrolytic capacitor is connected with the first node, the first end of the first switching switch is connected with the first node, the second end of the first switching switch is connected with the first end of the first suppression inductor, and the second end of the first suppression inductor is connected with the first end of the film capacitor; the second end of the first electrolytic capacitor is connected with a second node, the first end of the second switching switch is connected with the second node, the second end of the second switching switch is connected with the first end of the second suppression inductor, and the second end of the second suppression inductor is connected with the second end of the film capacitor;

the first end of the second electrolytic capacitor is connected with the third switching switch, the second end of the third switching switch is connected with the first node, the second end of the second electrolytic capacitor is connected with the first end of the fourth switching switch, and the second end of the fourth switching switch is connected with the second node.

Preferably, the controller is specifically configured to control the first, second, third and fourth switching switches to be turned off when the inverter is operated without outputting reactive power. Or controlling the first and second switching switches to be opened, and controlling the third and fourth switching switches to be closed;

the controller is particularly used for controlling the first switching switch, the second switching switch, the third switching switch and the fourth switching switch to be closed when the inverter works in a reactive power output or transient transition state; or, the first and second switching switches are controlled to be closed.

the first end of the first electrolytic capacitor is connected with the first node through a first switching switch, the first end of the first suppression inductor is connected with the first node, and the second end of the first suppression inductor is connected with the first end of the film capacitor; the second end of the first electrolytic capacitor is connected with a second node through a second switching switch, the first end of the second suppression inductor is connected with the second node, and the second end of the second suppression inductor is connected with the second end of the film capacitor;

the first end of the second electrolytic capacitor is connected with a third node through a third switching switch, the third node is connected with the first node, the second end of the second electrolytic capacitor is connected with a fourth node through a fourth switching switch, and the fourth node is connected with the second node.

Preferably, the controller is specifically configured to control the first switching switch, the second switching switch, the third switching switch, and the fourth switching switch to be turned off when the inverter is operated without outputting reactive power; or controlling the first and second switching switches to be opened, and controlling the third and fourth switching switches to be closed;

the controller is particularly used for controlling the first switching switch, the second switching switch, the third switching switch and the fourth switching switch to be closed when the inverter works in a reactive power output or transient transition state; or, controlling the first and second switching switches to be closed; or, the third and fourth switching switches are controlled to be closed.

Preferably, the controller is further configured to obtain a first time when the first electrolytic capacitor is connected to the suppression inductor, and obtain a second time when the second electrolytic capacitor is connected to the suppression inductor; when the inverter works in a reactive power output or transient transition state, the first time is longer than the second time, the third switching switch and the fourth switching switch are controlled to be closed, and otherwise, the first switching switch and the second switching switch are controlled to be closed.

The application also provides a control method of the inverter, wherein the inverter comprises the following steps: inverter circuit, electrolytic capacitor, suppression inductance and film capacitance; the membrane capacitor is connected in parallel between the positive input end and the negative input end of the inverter circuit, and the electrolytic capacitor and the suppressing inductor are connected in series and then connected in parallel at two ends of the membrane capacitor;

the control method comprises the following steps:

obtaining the current working condition of the inverter;

according to the magnitude of reactive power required to be output by the inverter, the state of the switching switch is controlled to realize the input or the cutting off of at least part of the electrolytic capacitor.

Preferably, according to the magnitude of reactive power that the inverter needs to output, the switching switch is controlled to implement at least partial switching or cutting of the electrolytic capacitor, and specifically includes:

when the inverter works without outputting reactive power, the switching switch is controlled to be switched off; and when the inverter works in a reactive power output or transient transition state, the switching switch is controlled to be closed.

Preferably, the electrolytic capacitor includes a first electrolytic capacitor and a second electrolytic capacitor;

the method further comprises the steps of:

obtaining a first time when the first electrolytic capacitor is connected with the suppression inductor, and obtaining a second time when the second electrolytic capacitor is connected with the suppression inductor;

when the inverter works in a reactive power output or transient transition state, the first time is longer than the second time, the third switching switch and the fourth switching switch are controlled to be closed, and otherwise, the first switching switch and the second switching switch are controlled to be closed.

From this, this application has following beneficial effect:

in order to increase the service life of the electrolytic capacitors, at least part of the electrolytic capacitors are connected to the circuit when needed, and at least part of the electrolytic capacitors can be disconnected from the circuit when not needed. For example, most of the working scenes of the inverter are in full active state, namely, when reactive power is not output, so that no electrolytic capacitor is needed to participate in the working, or only a small amount of electrolytic capacitors are needed to participate in the working. When the inverter needs to output reactive power or is in transient state excessive working condition, all or part of electrolytic capacitors are put into operation. Wherein, the excessive suspension includes, but is not limited to, the situation that the power grid is over-voltage, under-voltage and the like.

Drawings

Fig. 1 is a schematic diagram of a conventional inverter;

fig. 2 is a schematic diagram of an inverter according to an embodiment of the present disclosure;

fig. 3 is a schematic diagram of yet another inverter provided in an embodiment of the present application;

fig. 4 is a schematic diagram of another inverter according to an embodiment of the present disclosure;

fig. 5A is a schematic diagram of yet another inverter provided in an embodiment of the present application;

fig. 5B is a schematic diagram of another inverter according to an embodiment of the present disclosure;

fig. 6 is a schematic diagram of yet another inverter according to an embodiment of the present disclosure;

fig. 7 is a schematic diagram of another inverter according to an embodiment of the present disclosure;

fig. 8 is a schematic diagram of yet another inverter provided in an embodiment of the present application;

fig. 9 is a flowchart of a control method of an inverter according to an embodiment of the present application.

Detailed Description

In order to enable those skilled in the art to better understand and implement the technical solutions provided in the embodiments of the present application, a specific application scenario is first described below with reference to the accompanying drawings.

Referring to fig. 1, a schematic diagram of a conventional inverter is shown.

The inverter provided by the embodiment of the application comprises: an inverter circuit 100, an electrolytic capacitor C1, a suppression inductance, and a film capacitor C2; in this application, two suppression inductors are taken as an example, and the first suppression inductor L1 and the second suppression inductor L2, it should be understood that the inverter may also include only one suppression inductor.

In fig. 1, only one membrane capacitor and one electrolytic capacitor are illustrated, and in an actual product, the number of membrane capacitors may be plural, and the number of electrolytic capacitors may be plural. The specific number of the film capacitor and the electrolytic capacitor is not particularly limited in the embodiment of the present application.

The membrane capacitor C2 is connected in parallel between the positive input end and the negative input end of the inverter circuit 100, and the electrolytic capacitor C1 and the suppression inductors (L1 and L2) are connected in series and then connected in parallel at two ends of the membrane capacitor C2; the capacitance value of the film capacitor is generally small, the film capacitor is used for absorbing high-frequency ripple current, and the film capacitor cannot absorb low-frequency ripple current, so that the film capacitor cannot support the output of reactive power of the inverter and cannot replace the electrolytic capacitor.

Conventionally, the electrolytic capacitor C1 is always connected in the circuit to participate in the operation, which reduces the service life of the electrolytic capacitor C1.

In order to improve the service life of the electrolytic capacitor, the electrolytic capacitor is connected into the circuit when needed, and the electrolytic capacitor is disconnected from the circuit when not needed. For example, most of the working scenes of the inverter are in full active state, namely, when reactive power is not output, so that no electrolytic capacitor is needed to participate in the working, or only a small amount of electrolytic capacitors are needed to participate in the working. When the inverter needs to output reactive power or is in transient state excessive working condition, all or part of electrolytic capacitors are put into operation. Wherein, the excessive suspension includes, but is not limited to, overvoltage, undervoltage and other conditions of the power grid, and the inverter is required to participate in voltage or frequency adjustment.

In order to make the above objects, features and advantages of the present application more comprehensible, embodiments accompanied with figures and detailed description are described in further detail below.

Referring to fig. 2, a schematic diagram of an inverter according to an embodiment of the present application is shown.

The inverter provided by the embodiment of the application comprises: an inverter circuit 100, an electrolytic capacitor C1, a switching switch S, a suppression inductance, and a film capacitor C2; in this application, two suppression inductors are taken as an example, and the first suppression inductor L1 and the second suppression inductor L2, it should be understood that the inverter may also include only one suppression inductor.

The membrane capacitor C2 is connected in parallel between the positive input end and the negative input end of the inverter circuit 100, and the electrolytic capacitor C1 and the suppression inductors (L1 and L2) are connected in series and then connected in parallel at two ends of the membrane capacitor C2;

when the inverter works at full active power output, the electrolytic capacitor C1 is disconnected with the suppressing inductors (L1 and L2).

It should be understood that the electrolytic capacitor C1 is disconnected from the suppressing inductance, a switch may be connected in a series path, and whether the electrolytic capacitor C1 is connected to the circuit may be realized by controlling the state of the switch. The suppression inductor is used for suppressing the high-frequency ripple, preventing the high-frequency ripple from flowing to the electrolytic capacitor C1, and the suppression inductor does not need to suppress the high-frequency ripple when the electrolytic capacitor C1 is not connected to the circuit, so that the suppression inductor may not participate in the operation, and disconnect the connection with the inverter circuit 100.

The inverter provided in the embodiment of the application further includes: a controller (not shown in the figure); in fig. 2, two ends of the switching switch S are respectively connected to a first end of the electrolytic capacitor C1 and a first end of the first suppression inductor L1, a second end of the first suppression inductor L1 is connected to a positive input end of the inverter circuit 200, a first end and a second end of the second suppression inductor L2 are respectively connected to a second end of the electrolytic capacitor C1 and a second end of the film capacitor C2, a first end of the film capacitor C2 is connected to a positive input end of the inverter circuit 200, and a second end of the film capacitor C2 is connected to a negative input end of the inverter circuit 200.

In fig. 2, the switching switch S is connected between C1 and L1, and in addition, the switching switch S may be connected between C1 and L2, as shown in fig. 3, and the number of the switching switches may be one, as shown in fig. 2 and 3, or two, as shown in fig. 4, including the first switching switch S1 and the second switching switch S2. The first switch S1 is connected at the same position as the switch S in fig. 2, the second switch S2 is connected at the same position as the switch S in fig. 3, and the electrolytic capacitor corresponds to the following two switches: the first switching switch S1 and the second switching switch S2, the suppression inductance includes two of: a first suppression inductance L1 and a second suppression inductance L2; the first end of the electrolytic capacitor C1 is connected with the first suppression inductor through the first switching switch S1; the second end of the first suppression inductor L1 is connected with the first end of the film capacitor C2; the second end of the electrolytic capacitor C1 is connected with a second suppression inductor L2 through a second switching switch S2; the second end of the second suppression inductor L2 is connected to the second end of the film capacitor C2.

The two on-off switches S1 and S2 in fig. 4 are operated simultaneously, for example, when C1 needs to be accessed, S1 and S2 are closed simultaneously; when C1 needs to be resected, S1 and S2 are disconnected simultaneously.

The controller is used for controlling the switching switch S to be switched off when the inverter works without outputting reactive power output; and when the inverter works in a reactive power output or transient transition state, the switching switch S is controlled to be closed.

The embodiment of the present application is not particularly limited to the type of the switching switch S, and may be, for example, a switching device such as a MOS transistor, an IGBT, or a relay.

The controller automatically switches the electrolytic capacitor according to the operation condition of the inverter. For example, the inverter is in a state of not outputting reactive power, and at the moment, the electrolytic capacitor is not required to participate in work, the controller automatically controls the switching switch to be opened, namely the electrolytic capacitor is cut off, and when the inverter is detected to need to generate reactive power, the controller automatically controls the switching switch to be closed, and the electrolytic capacitor is put into work.

Specific implementations of electrolytic capacitors including a plurality of them are described below.

Referring to fig. 5A, a schematic diagram of yet another inverter according to an embodiment of the present application is shown.

In the practical product of the inverter provided by the embodiment of the application, the inverter comprises at least two electrolytic capacitors, and because the bus voltage is higher, a single electrolytic capacitor cannot meet the requirement, for example, two electrolytic capacitors can be connected in series. The common point of the two electrolytic capacitors connected in series is connected with the midpoints of the upper bus and the lower bus of the inverter. The bus bar herein refers to a direct current bus bar. Referring to fig. 5B, the electrolytic capacitor may include only C11a and C11B, or may include C11a, C11B, C12a, and C12B. Wherein, C11a and C11b are connected in series, and the common point of C11a and C11b connects the midpoint N of the upper bus and the lower bus of the inverter. The common point of C12a and C12b connects the midpoint N of the upper and lower bus bars of the inverter. For example, it is necessary to disconnect C12a and C12b from inverter circuit 100, and control S21 only, or S22 only, and it is not possible to completely disconnect C12a and C12b from inverter circuit 100.

The following description is continued with reference to fig. 5A for convenience of description. The number of electrolytic capacitors is not particularly limited in the embodiments of the present application, and if the capacitance of a single electrolytic capacitor is sufficient to withstand the busbar voltage, only one electrolytic capacitor may be used, like C11 and C12 in fig. 5, for example, C11 directly connects the upper busbar and the lower busbar. The electrolytic capacitor comprises at least two of the following: a first electrolytic capacitor C11 and a second electrolytic capacitor C12; the first electrolytic capacitor C11 corresponds to the first and second switching switches S11 and S12, and the second electrolytic capacitor C12 corresponds to the third and fourth switching switches S21 and S22; the suppression inductance includes two of the following: a first suppression inductance L1 and a second suppression inductance L2;

the first end of the first electrolytic capacitor C11 is connected with a first node, the first end of the first switching switch S11 is connected with the first node A, the second end of the first switching switch S11 is connected with the first end of the first suppression inductor L1, and the second end of the first suppression inductor L1 is connected with the first end of the film capacitor C2; the second end of the first electrolytic capacitor C11 is connected with the second node B, the first end of the second switching switch S12 is connected with the second node B, the second end of the second switching switch S12 is connected with the first end of the second suppression inductor L2, and the second end of the second suppression inductor L2 is connected with the second end of the film capacitor C2.

The first end of the second electrolytic capacitor C12 is connected with the third switching switch S21, the second end of the third switching switch S21 is connected with the first node A, the second end of the second electrolytic capacitor C12 is connected with the first end of the fourth switching switch S22, and the second end of the fourth switching switch S22 is connected with the second node B.

The working principle of fig. 5A is that the controller is specifically configured to control the first switch S11, the second switch S12, the third switch S21 and the fourth switch S22 to be turned off when the inverter is not outputting reactive power;

when the inverter works in a reactive power output or transient transition state, all electrolytic capacitors can be used, and part of electrolytic capacitors can also be used. For example, the controller controls the first, second, third, and fourth switching switches S11, S12, S21, and S22 to be all closed; or, the first and second switching switches S11 and S12 are controlled to be closed.

Since S11 and S12 in fig. 5A are located on the trunk, when S11 is open, S21 is closed, and C12 cannot access the circuit, and similarly, when S12 is open, S22 is closed, and C12 cannot access the trunk.

Fig. 5A illustrates the description taking two electrolytic capacitors as an example, each electrolytic capacitor corresponds to two switching switches, and it should be understood that each electrolytic capacitor may also correspond to one switching switch, for example, in fig. 5A, S11 and S21 may be included only, or S12 and S22 may be included only.

Next, a structure similar to that of fig. 5A, including three electrolytic capacitors, is described, as shown in fig. 6, which is a schematic diagram of still another inverter according to an embodiment of the present application.

The three electrolytic capacitors are C11, C12 and C13 respectively, wherein C11 corresponds to the switching switches S11 and S12, C12 corresponds to the switching switches S21 and S22, and C13 corresponds to the switching switches S31 and S32. Wherein the first end and the second end of C11 are connected to the first node a and the second node B, respectively. The first end and the second end of C12 are connected to the third node C and the fourth node D, respectively.

The embodiment of the application also provides another connection mode of the switching switch, referring to fig. 7, which is a schematic diagram of another inverter provided in the embodiment of the application.

The inverter provided by the embodiment of the application, the electrolytic capacitor comprises at least two of the following: a first electrolytic capacitor C11 and a second electrolytic capacitor C12; the first electrolytic capacitor C11 corresponds to the first and second switching switches S11 and S12, and the second electrolytic capacitor C12 corresponds to the third and fourth switching switches S21 and S22; the suppression inductance includes two of the following: a first suppression inductance L1 and a second suppression inductance L2;

the first end of the first electrolytic capacitor C11 is connected with a first node through a first switching switch S11, the first end of the first suppression inductor L1 is connected with a first node A, and the second end of the first suppression inductor L1 is connected with the first end of the film capacitor C2; the second end of the first electrolytic capacitor C11 is connected with the second node B through a second switching switch S12, the first end of the second suppression inductor L2 is connected with the second node B, and the second end of the second suppression inductor L2 is connected with the second end of the film capacitor C2;

the first end of the second electrolytic capacitor C12 is connected with a third node C through a third switching switch S21, the third node C is connected with a first node A, the second end of the second electrolytic capacitor C12 is connected with a fourth node D through a fourth switching switch S22, and the fourth node D is connected with a second node B.

The position of the on-off switch shown in fig. 7 is different from that of the on-off switch shown in fig. 5, and in fig. 7, the on-off switches are located on the branch, and the on-off switches corresponding to the electrolytic capacitors do not affect each other, for example, when C11 is connected to the circuit, S11 and S12 may be closed. When the C12 is connected into the circuit, the S21 and the S22 are closed, and the switching switch arranged in the way is controlled more flexibly.

The corresponding working principle of fig. 7 is that the controller is specifically configured to control the first switch S11, the second switch S12, the third switch S21 and the fourth switch S22 to be turned off when the inverter is not outputting reactive power;

the controller is specifically used for controlling the first switching switch S11, the second switching switch S12, the third switching switch S21 and the fourth switching switch S22 to be closed when the inverter works in a reactive power output or transient transition state; or, the first switching switch S11 and the second switching switch S12 are controlled to be closed; or, the third and fourth switching switches S21 and S22 are both controlled to be closed.

Because the switching switches in the inverter provided by the embodiment of the application are not mutually influenced, any electrolytic capacitor can be freely controlled to be connected into or disconnected from the circuit.

In fig. 7, two electrolytic capacitors are taken as an example, and it should be understood that the electrolytic capacitors may be more, for example, three, four, or more.

Referring to fig. 8, a schematic diagram of yet another inverter according to an embodiment of the present application is provided. The inverter shown in fig. 8 includes three electrolytic capacitors, and each electrolytic capacitor corresponds to two switching switches, and the switching switches corresponding to different electrolytic capacitors do not affect each other.

It should be understood that the electrolytic capacitors in fig. 6-8 above may be similar to those shown in fig. 5B, and each electrolytic capacitor may actually include two electrolytic capacitors connected in series, or four electrolytic capacitors connected in series, which is not specifically shown here.

The first end of C11 is connected to the first node a through S11, and the second end of C11 is connected to the second node B through S12. The first end of C12 is connected with the third node C through S21, and the second end of C12 is connected with the fourth node D through S22. The first end of C13 is connected to the fifth node E through S31, and the second end of C13 is connected to the sixth node F through S32.

It should be understood that the corresponding on-off switches on both sides of the same electrolytic capacitor may be controlled by the same driving signal or may be controlled by two independent driving signals, but require simultaneous operation, e.g., S11 and S12 may use the same driving signal or may use two different driving signals. However, when two different drive signals are used, it is necessary to control S11 and S12 to act simultaneously, i.e. to be closed simultaneously, or to be opened simultaneously.

In another implementation manner, the inverter provided by the embodiment of the application can adopt a plurality of switching switches, and according to the input time of each electrolytic capacitor, the service time of each electrolytic capacitor can be balanced, so that a certain electrolytic capacitor is prevented from being input into use for a long time, the service life is seriously attenuated, and the service time of each electrolytic capacitor is balanced as much as possible.

The inverter and the controller provided by the embodiment of the application are further used for obtaining the first time of the first electrolytic capacitor connection suppression inductance and obtaining the second time of the second electrolytic capacitor connection suppression inductance; when the inverter works in a reactive power output or transient transition state, the first time is longer than the second time, the third switching switch and the fourth switching switch are controlled to be closed, and otherwise, the first switching switch and the second switching switch are controlled to be closed.

It should be appreciated that the above time balancing applies to the manner of connection of the on-off switches shown in fig. 7 and 8, and each electrolytic capacitor may be independently controlled, so that the sum of the times each electrolytic capacitor operates is equal as much as possible.

Based on the inverter provided in the foregoing embodiments, the embodiments of the present application further provide a control method of the inverter, which is described in detail below with reference to the accompanying drawings.

Referring to fig. 9, a flowchart of a control method of an inverter according to an embodiment of the present application is shown.

The inverter control method provided by the embodiment of the application comprises the following steps: inverter circuit, electrolytic capacitor, suppression inductance and film capacitance; the membrane capacitor is connected in parallel between the positive input end and the negative input end of the inverter circuit, and the electrolytic capacitor and the suppressing inductor are connected in series and then connected in parallel at two ends of the membrane capacitor;

the control method comprises the following steps:

s901: obtaining the current working condition of the inverter;

s902: according to the magnitude of reactive power required to be output by the inverter, the state of the switching switch is controlled to realize the input or the cutting off of at least part of the electrolytic capacitor.

In order to improve the service life of the electrolytic capacitor, the electrolytic capacitor is connected into the circuit when needed, and the electrolytic capacitor is disconnected from the circuit when not needed. For example, most of the working scenes of the inverter are when reactive power is not output, so that no electrolytic capacitor is needed to participate in the working, or only a small amount of electrolytic capacitor is needed to participate in the working. When the inverter needs to output reactive power or is in transient state excessive working condition, all or part of electrolytic capacitors are put into operation. Wherein, the excessive suspension includes, but is not limited to, the situation that the power grid is over-voltage, under-voltage and the like.

According to the magnitude of reactive power to be output by the inverter, the switching state of the switching switch is controlled to realize the input or the cutting of at least part of the electrolytic capacitor, and the method specifically comprises the following steps:

One possible implementation is that the inverter can be controlled to turn off when it is not outputting reactive power, i.e. all electrolytic capacitors are not put into operation; when the inverter works in a reactive power output or transient transition state, the switching switch is controlled to be closed, and then all electrolytic capacitors can be controlled to be put in.

In addition, when the inverter works at reactive power output, only part of electrolytic capacitor input can be controlled.

The electrolytic capacitor comprises a first electrolytic capacitor and a second electrolytic capacitor;

the method further comprises the steps of:

It should be noted that, in the present description, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different manner from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the system or device disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and the relevant points refer to the description of the method section.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present application. 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 application. Thus, the present application 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 inverter, comprising: the switching device comprises an inverter circuit, an electrolytic capacitor, a switching switch and a film capacitor;

2. The inverter according to claim 1, further comprising: a controller and a suppression inductor; the electrolytic capacitor and the suppression inductor are connected in series and then connected in parallel at two ends of the membrane capacitor;

the controller is used for controlling the switching switch to be disconnected when the inverter works without outputting reactive power; and when the inverter works in a reactive power output or transient transition state, the switching switch is controlled to be closed.

3. The inverter of claim 1, wherein the electrolytic capacitor comprises two electrolytic capacitors connected in series, a common point of the two electrolytic capacitors connecting a midpoint of an upper bus and a lower bus of the inverter; the electrolytic capacitor corresponds to the following two switching switches: the first switching switch and the second switching switch, the suppression inductance includes the following two: a first suppression inductance and a second suppression inductance;

the second end of the electrolytic capacitor is connected with the second suppression inductor through the second switching switch; and the second end of the second suppression inductor is connected with the second end of the film capacitor.

4. The inverter of claim 2, wherein the electrolytic capacitor comprises two electrolytic capacitors connected in series, a common point of the two electrolytic capacitors connecting a midpoint of an upper bus and a lower bus of the inverter; the electrolytic capacitor comprises at least two of the following: a first electrolytic capacitor and a second electrolytic capacitor; the first electrolytic capacitor corresponds to a first switching switch and a second switching switch, and the second electrolytic capacitor corresponds to a third switching switch and a fourth switching switch; the suppression inductance comprises the following two components: a first suppression inductance and a second suppression inductance;

the first end of the first electrolytic capacitor is connected with a first node, the first end of the first switching switch is connected with the first node, the second end of the first switching switch is connected with the first end of the first suppression inductor, and the second end of the first suppression inductor is connected with the first end of the film capacitor; the second end of the first electrolytic capacitor is connected with a second node, the first end of the second switching switch is connected with the second node, the second end of the second switching switch is connected with the first end of the second suppression inductor, and the second end of the second suppression inductor is connected with the second end of the membrane capacitor;

5. The inverter of claim 4, wherein the controller is configured to control the first, second, third, and fourth switching switches to be opened when the inverter is operating without outputting reactive power; or controlling the first and second switching switches to be opened, and controlling the third and fourth switching switches to be closed;

the controller is specifically used for controlling the first switching switch, the second switching switch, the third switching switch and the fourth switching switch to be closed when the inverter works in a reactive power output or transient transition state; or, controlling the first and second switching switches to be closed.

6. The inverter of claim 2, wherein the electrolytic capacitor comprises two electrolytic capacitors connected in series, a common point of the two electrolytic capacitors connecting a midpoint of an upper bus and a lower bus of the inverter; the electrolytic capacitor comprises at least two of the following: a first electrolytic capacitor and a second electrolytic capacitor; the first electrolytic capacitor corresponds to a first switching switch and a second switching switch, and the second electrolytic capacitor corresponds to a third switching switch and a fourth switching switch; the suppression inductance comprises the following two components: a first suppression inductance and a second suppression inductance;

the first end of the first electrolytic capacitor is connected with a first node through the first switching switch, the first end of the first suppression inductor is connected with the first node, and the second end of the first suppression inductor is connected with the first end of the membrane capacitor; the second end of the first electrolytic capacitor is connected with a second node through the second switching switch, the first end of the second suppression inductor is connected with the second node, and the second end of the second suppression inductor is connected with the second end of the film capacitor;

the first end of the second electrolytic capacitor is connected with a third node through the third switching switch, the third node is connected with the first node, the second end of the second electrolytic capacitor is connected with a fourth node through the fourth switching switch, and the fourth node is connected with the second node.

7. The inverter of claim 6, wherein the controller is configured to control the first, second, third, and fourth switching switches to be opened when the inverter is operating without outputting reactive power; or controlling the first and second switching switches to be opened, and controlling the third and fourth switching switches to be closed;

the controller is specifically used for controlling the first switching switch, the second switching switch, the third switching switch and the fourth switching switch to be closed when the inverter works in a reactive power output or transient transition state; or, controlling the first and second switching switches to be closed; or, controlling the third and fourth switching switches to be closed.

8. The inverter of claim 6, wherein the controller is further configured to obtain a first time when the first electrolytic capacitor is connected to the suppression inductor and obtain a second time when the second electrolytic capacitor is connected to the suppression inductor; and when the inverter works in a reactive power output or transient transition state, the third switching switch and the fourth switching switch are controlled to be closed, and otherwise, the first switching switch and the second switching switch are controlled to be closed.

9. A control method of an inverter, characterized in that the inverter comprises: inverter circuit, electrolytic capacitor, suppression inductance and film capacitance; the membrane capacitor is connected in parallel between the positive input end and the negative input end of the inverter circuit, and the electrolytic capacitor and the suppression inductor are connected in series and then connected in parallel at two ends of the membrane capacitor;

the control method comprises the following steps:

obtaining the current working condition of the inverter;

10. The control method according to claim 9, wherein the switching or cutting off of at least part of the electrolytic capacitor is achieved by controlling the state of the switching switch according to the amount of reactive power that the inverter needs to output, specifically comprising:

11. The control method according to claim 9 or 10, characterized in that the electrolytic capacitor includes a first electrolytic capacitor and a second electrolytic capacitor;

the method further comprises the steps of:

and when the inverter works in a reactive power output or transient transition state, the third switching switch and the fourth switching switch are controlled to be closed, and otherwise, the first switching switch and the second switching switch are controlled to be closed.