Grid-connected and off-grid switching circuit, grid-connected and off-grid switching device and inverter

Abstract

The utility model discloses a grid-connected and off-grid switching circuit, a grid-connected and off-grid switching device and an inverter, and belongs to the technical field of power electronics. The grid-connected and off-grid switching circuit is provided with an inverter node, a power grid node and a load node, the grid-connected and off-grid switching circuit comprises a first load branch line, a second load branch line, a load bus and a grid-connected bus, the first side of the grid-connected bus is connected with the inverter node, and the second side of the grid-connected bus is connected with the power grid node; the first side of the first load branch line is connected with the first side of the grid-connected bus, the first side of the second load branch line is connected with the second side of the grid-connected bus, the second side of the first load branch line and the second side of the second load branch line are both connected with the first side of the load bus, and the second side of the load bus is connected with the load node; and controllable switches are arranged on the first load branch line, the second load branch line and the grid-connected bus. The configuration of the load power supply path is more flexible, and when the inversion node and the power grid node need to be isolated, the power supply can be conveniently accessed from the corresponding node, thereby improving the isolation effect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power electronics, and particularly relates to a parallel-off-grid switching circuit, a parallel-off-grid switching device and an inverter. BACKGROUND

[0002] With the popularization of photovoltaic and energy storage applications, various application scenarios have brought unprecedented differentiation of product demand. In application scenarios where power grid power supply is unstable, photovoltaic and energy storage inverters are required to have both grid-connected and off-grid working modes, and there will naturally be a parallel-off-grid switching process. In the prior art, a photovoltaic and energy storage inverter provided with a parallel-off-grid switching circuit has a single load power supply path during operation, and there is even a problem that electrical isolation between the inverter and the power grid cannot meet the safety specification requirements. CONTENT OF THE UTILITY MODEL

[0003] The application aims to at least solve one of the technical problems existing in the prior art. To this end, the application provides a parallel-off-grid switching circuit, a parallel-off-grid switching device and an inverter, which have low load power supply path conduction loss, flexible configuration, and especially facilitate the access of power from the corresponding node when the inverter node and the power grid node need to be isolated, thereby improving the isolation effect.

[0004] In a first aspect, the application provides a parallel-off-grid switching circuit, which has an inverter node, a power grid node and a load node, and includes: a first load branch, a second load branch, a load bus and a grid-connected bus, the first side of the grid-connected bus is electrically connected to the inverter node, the second side of the grid-connected bus is electrically connected to the power grid node, the first side of the first load branch is electrically connected to the first side of the grid-connected bus, the first side of the second load branch is electrically connected to the second side of the grid-connected bus, the second side of the first load branch and the second side of the second load branch are both electrically connected to the first side of the load bus, and the second side of the load bus is electrically connected to the load node.

[0005] Among them, controllable switches are arranged on the first load branch, the second load branch and the grid-connected bus.

[0006] According to the parallel-off-grid switching circuit of the application, the load bus is electrically connected to the grid-connected bus through at least two load branches, the load power supply path has low conduction loss, the configuration is more flexible, and especially when the inverter node and the power grid node need to be isolated, it is convenient to access power from the corresponding node, thereby improving the isolation effect.

[0007] According to an embodiment of the application, the grid-connected bus is provided with a switching unit including at least two levels of switches, and the connection node of the first side of the first load branch to the grid-connected bus is located between the switching unit and the inverter node.

[0008] According to one embodiment of the present application, the connection node of the first side of the second load branch and the grid-connected bus is located between two adjacent switches in the switch unit.

[0009] According to one embodiment of the present application, the off-grid switching circuit further comprises:

[0010] At least one extension branch, the first side of the extension branch is electrically connected with the load bus, the second side of the extension branch is used for electrically connecting with the extension device, and a controllable switch is arranged on the extension branch.

[0011] In a second aspect, the present application provides a grid-connected and off-grid switching device, which comprises:

[0012] The grid-connected module comprises:

[0013] The grid-connected bus, the first side of the grid-connected bus is used for electrically connecting with the alternating current side of the inverter circuit, and the second side of the grid-connected bus is provided with a power grid interface;

[0014] The first power interface is electrically connected with the first side of the grid-connected bus;

[0015] The second power interface is electrically connected with the second side of the grid-connected bus;

[0016] The off-grid module comprises:

[0017] The first load branch and the second load branch;

[0018] The load bus, the first side of the load bus is electrically connected with the first side of the first load branch and the first side of the second load branch respectively, and the second side of the load bus is provided with a load interface;

[0019] The third power interface is electrically connected with the second side of the first load branch;

[0020] The fourth power interface is electrically connected with the second side of the second load branch;

[0021] The off-grid module and the grid-connected module are detachably connected with the first power interface for connecting with the third power interface, the second power interface is used for connecting with the fourth power interface, and the first load branch, the second load branch and the grid-connected bus are all provided with controllable switches.

[0022] According to the grid-connected and off-grid switching device of the present application, the load bus is electrically connected with the grid-connected bus through at least two load branches, the conduction loss of the load power supply path is low, the configuration is more flexible, and especially when the inverter node and the power grid node need to be isolated, the power supply can be easily accessed from the corresponding node, and the isolation effect is improved.

[0023] According to one embodiment of the present application, the grid-connected bus is provided with a switching unit comprising at least two switches, and the connection node of the first power interface with the grid-connected bus is located between the switching unit and the AC side of the inverter circuit.

[0024] According to one embodiment of the present application, the connection node of the second power interface with the grid-connected bus is located between two adjacent switches in the switching unit.

[0025] According to one embodiment of the present application, the off-grid module further comprises:

[0026] The extension interface is electrically connected with the load bus.

[0027] In a third aspect, the present application provides an inverter comprising the aforementioned grid-off switching circuit, or comprising the aforementioned grid-off switching device.

[0028] According to the inverter of the present application, the load bus is electrically connected with the grid-connected bus through at least two load branches, the load power supply path has low conduction loss, and the configuration is more flexible, especially when the inverter node and the grid node need to be isolated, the power supply can be easily accessed from the corresponding node, and the isolation effect is improved.

[0029] According to one embodiment of the present application, the inverter comprises:

[0030] The inverter circuit, the AC side of the inverter circuit is electrically connected with the inverter node;

[0031] The voltage detection circuit, the input end of the voltage detection circuit is respectively electrically connected with the AC side of the inverter circuit, the load node and the grid node;

[0032] The first current detection circuit, the input end of the first current detection circuit is electrically connected with the AC side of the inverter circuit;

[0033] The second current detection circuit, the input end of the second current detection circuit is electrically connected with the grid node;

[0034] The driving unit, the input end of the driving unit is respectively electrically connected with the output end of the voltage detection circuit, the output end of the first current detection circuit and the output end of the second current detection circuit, and the output end of the driving unit is electrically connected with the driving end of each controllable switch.

[0035] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0036] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description, taken in conjunction with the accompanying drawings, in which:

[0037] Figure 1is a structural schematic diagram of a parallel off-grid switching circuit provided by an embodiment of the present application;

[0038] Figure 2 is a structural schematic diagram of a parallel off-grid switching circuit provided by an embodiment of the present application;

[0039] Figure 3 is a structural schematic diagram of a parallel off-grid switching circuit provided by an embodiment of the present application;

[0040] Figure 4 is a power supply working condition schematic diagram of a parallel off-grid switching circuit provided by an embodiment of the present application;

[0041] Figure 5 is a power supply working condition schematic diagram of a parallel off-grid switching circuit provided by an embodiment of the present application;

[0042] Figure 6 is a power supply working condition schematic diagram of a parallel off-grid switching circuit provided by an embodiment of the present application;

[0043] Figure 7 is a power supply working condition schematic diagram of a parallel off-grid switching circuit provided by an embodiment of the present application;

[0044] Figure 8 is a structural schematic diagram of a parallel off-grid switching circuit provided by an embodiment of the present application;

[0045] Figure 9 is a structural schematic diagram of a parallel off-grid switching circuit provided by an embodiment of the present application;

[0046] Figure 10 is a structural schematic diagram of a parallel off-grid switching device provided by an embodiment of the present application;

[0047] Figure 11 is a structural schematic diagram of an inverter provided by an embodiment of the present application.

[0048] Reference signs:

[0049] Grid-connected bus 10, load bus 20, first load branch 21, second load branch 22, switching unit 30, expansion branch 40, expansion device 50, grid-connected module 60, first power interface 61, second power interface 62, off-grid module 70, third power interface 71, fourth power interface 72, inverter circuit 80, voltage detection circuit 91, first current detection circuit 92, second current detection circuit 93, driving unit 94, load interface 95, grid interface 96, first to fifth switches K1-K5. DETAILED DESCRIPTION

[0050] Embodiments of the present application are described below in detail with reference to the accompanying drawings, wherein the same or similar components or components having the same or similar functions are denoted by the same or similar reference numerals throughout the drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as a limitation on the present application.

[0051] In the following description, "circuitry" refers to a conductive loop formed by at least one element or sub-circuit through electrical or electromagnetic connection. When it is said that an element or circuit is "coupled to" or "connected to" another element or that the element / circuit is "coupled between" or "connected between" two nodes, it can be directly coupled or connected to another element or there can be an intermediate element, and the connection between elements can be physical, logical, or a combination thereof. On the contrary, when it is said that an element is "directly coupled to" or "directly connected to" another element, it means that there is no intermediate element between the two.

[0052] In the description, the terms "first", "second", and the like are used to distinguish similar objects, and are not used to describe a particular order or sequence. It should be understood that the numerical descriptors used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than that illustrated or described here, and the objects distinguished by "first", "second", etc. are usually a class, and do not limit the number of objects, for example, the first object can be one or more. In addition, "and / or" in the specification and claims means at least one of the connected objects, and the character " / ", generally means that the objects before and after are in an "or" relationship.

[0053] In addition, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the exemplary description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0054] With the popularization of photovoltaic and energy storage applications, various application scenarios have brought unprecedented differentiation of product demand. In most application scenarios, photovoltaic and energy storage inverters are required to have both grid-connected and off-grid working modes, and there will naturally be a process of switching between grid-connected and off-grid working modes.

[0055] In the related art, part of the light storage inverter can only work in parallel with the grid. If the switching between the grid-connected mode and the off-grid mode is to be realized, an additional grid-connected and off-grid switching distribution box needs to be equipped, which is high in cost. The light storage inverter provided with the grid-connected and off-grid switching circuit has a single load power supply path in the running process, and the electrical isolation between the inverter and the grid cannot meet the safety specification requirements.

[0056] With reference to Figure 1 , Figure 1 A grid-connected and off-grid switching circuit provided by an embodiment of the present application is shown. An embodiment of the present application provides a grid-connected and off-grid switching circuit, which has an inversion node, a grid node and a load node, and includes: a first load branch 21, a second load branch 22, a load bus 20 and a grid-connected bus 10. The first side of the grid-connected bus 10 is electrically connected to the inversion node, and the second side of the grid-connected bus 10 is electrically connected to the grid node. The first side of the first load branch 21 is electrically connected to the first side of the grid-connected bus 10, and the first side of the second load branch 22 is electrically connected to the second side of the grid-connected bus 10. The second side of the first load branch 21 and the second side of the second load branch 22 are both electrically connected to the first side of the load bus 20, and the second side of the load bus 20 is electrically connected to the load node. Controllable switches are arranged on the first load branch 21, the second load branch 22 and the grid-connected bus 10.

[0057] As an example, the grid-connected and off-grid switching circuit can be arranged in an inverter. The inverter can include an inversion circuit and ports connected to the grid and the load. The inversion node of the grid-connected and off-grid switching circuit can be the alternating current side of the inversion circuit, the grid node of the grid-connected and off-grid switching circuit can be the port in the inverter for connecting to the grid, and the load node of the grid-connected and off-grid switching circuit can be the port in the inverter for connecting to the load.

[0058] The inverter can be a single-phase inverter or a three-phase inverter. The grid-connected bus 10 refers to the line connected between the alternating current side of the inversion circuit and the grid. When the inverter is a single-phase inverter, the grid-connected bus 10 includes one live wire and one neutral wire, and when the inverter is a three-phase inverter, the grid-connected bus 10 includes three live wires and one neutral wire.

[0059] The grid-connected bus 10 is electrically connected between the inversion node and the grid node, and when the grid-connected bus 10 is turned on, the grid-connected operation of the inversion circuit 80 can be realized, and in the grid-connected state, the inversion circuit 80 can realize the bidirectional flow of electric energy with the grid. The first load branch 21 is electrically connected between the first side of the grid-connected bus 10 and the load bus 20, and when the first load branch 21 is turned on, the inversion circuit 80 can supply power to the load. The second load branch 22 is electrically connected between the second side of the grid-connected bus 10 and the load bus 20, and the second load branch 22 can provide a path for the inversion circuit 80 to supply power to the load and for the grid to supply power to the load. The first load branch 21 and the second load branch 22 provide two paths for the inversion circuit 80 to supply power to the load, making the configuration of the load power supply path more flexible.

[0060] The load bus 20 can be used to provide electric energy transmitted by the first load branch 21 and / or the second load branch 22 to the load, realizing the centralized distribution of electric energy from the two branches to the load.

[0061] The first load branch 21, the second load branch 22 and the grid-connected bus 10 are each provided with a controllable switch, and the turning on and turning off of the controllable switch can realize the switching of the inversion circuit 80 between the grid-connected state and the off-grid state.

[0062] It should be noted that the number of controllable switches on each line can be selected according to the actual application scenario, which is not limited here.

[0063] As an example, the grid-connected bus 10 is provided with a first switch K1, and the first end of the first switch K1 can serve as the first side of the grid-connected bus 10, and the second end of the first switch K1 can serve as the second side of the grid-connected bus 10.

[0064] In other examples, the grid-connected bus 10 is provided with a first switch K1 and a second switch K2 in series, the first side of the grid-connected bus 10 is the first end of the first switch K1, and the second side of the grid-connected bus 10 is the second end of the first switch K1. The first side of the first load branch 21 is electrically connected to the first end of the first switch K1, and the first side of the second load branch 22 is electrically connected to the connection node of the first switch K1 and the second switch K2.

[0065] Compared with the above example, the grid-connected bus 10 is further provided with a second switch K2, forming a two-stage switch. Therefore, when the grid-connected bus 10 is disconnected, there are two-stage switches turned off between the inversion node and the grid node, realizing the electrical isolation between the inversion node and the grid node.

[0066] When the inverter is in grid-connected operation, the second switch K2 and the first switch K1 are both turned on, so as to realize the conduction of the power supply path between the inverter node and the grid node; when the grid supplies power to the load, the second switch K2 and the controllable switch on the second load branch 22 are both turned on, so as to realize the conduction of the power supply path between the grid and the load.

[0067] The type of the controllable switch can also be limited according to the actual application scenario, which is not limited here. For example, the controllable switch can be a MOSET (Metal-Oxie-Semicouctor iel-Eect Trasistor, metal-oxide semiconductor field effect transistor), an IGBT (Isulate-Gate Bipolar Trasistor, insulated gate bipolar transistor), or a relay, etc.

[0068] Reference Figure 2 and Figure 3 It should be noted that the off-grid switching circuit provided by the embodiments of the present application is applicable to both single-phase inverters and three-phase inverters. Figure 2 The circuit topology of the present embodiment applied to a single-phase inverter is shown, Figure 3 The circuit topology of the present embodiment applied to a three-phase inverter is shown. The circuit principles applied to single-phase inverters and three-phase inverters can both refer to the above-mentioned embodiments, which will not be described here again.

[0069] According to the off-grid switching circuit of the present application, the load bus 20 is electrically connected to the grid-connected bus 10 through at least two load branches, and the configuration of the load power supply path is more flexible, especially when the inverter node and the grid node need to be isolated, it is convenient to access the power supply from the corresponding node, and the isolation effect is improved.

[0070] In some embodiments, the grid-connected bus 10 is provided with a switching unit 30 including at least two levels of switches, and the connection node of the first load branch 21 and the grid-connected bus 10 is located between the switching unit 30 and the inverter node.

[0071] The connection node between the first side of the first load branch 21 and the grid-connected bus 10 and the inverter node is provided with a switching unit 30 including at least two levels of switches, which can realize electrical isolation between the inverter node and the grid node when the switching unit 30 is turned off.

[0072] The number of switches in the switching unit 30 can be selected according to the actual application scenario, which is not limited here. For example, the switching unit 30 can include two levels of switches in series, or three levels of switches in series.

[0073] When the first load branch 21 is turned on, the inverter node is connected to the load node, and the inverter circuit 80 supplies power to the load through the first load branch 21, so that the power supply impedance can be minimized and the energy loss can be reduced.

[0074] In some embodiments, the connection node between the first side of the second load branch 22 and the grid-connected bus 10 is located between two adjacent switches in the switch unit 30.

[0075] The connection node between the first side of the second load branch 22 and the inverter node and the grid node is provided with at least one switch, and the connection node and the grid node are also provided with at least one switch. When the inverter node supplies power to the load through the first load branch 21, the switches in the switch unit 30 are controlled to be turned off, and there are at least two levels of switches turned off between the inverter node and the grid node, so that electrical isolation between the inverter node and the grid node can be achieved.

[0076] Referring to Figures 4 to 7 , as an example, the grid-connected bus 10 is provided with a first switch K1 and a second switch K2 in series, a third switch K3 is provided on the first load branch 21, and a fourth switch K4 is provided on the second load branch 22. The first end of the third switch K3 is electrically connected to the inverter node, and the first end of the fourth switch K4 is electrically connected to the connection node of the first switch K1 and the second switch K2.

[0077] Referring to Figure 4 , when the first switch K1, the third switch K3 and the fourth switch K4 are turned on and the second switch K2 is turned off, the internal resistance of the first switch K1, the third switch K3 and the fourth switch K4 are connected in parallel, the inverter supplies power to the load, and the current will automatically distribute the flow path according to the impedance of each line, so that the power supply impedance can be small.

[0078] Referring to Figure 5 , when the first switch K1, the second switch K2 and the fourth switch K4 are turned off and the third switch K3 is turned on, the inverter supplies power to the grid through the first load branch, and the impedance is small. The inverter and the grid are connected by two levels of switches K1 and K2, which can realize electrical isolation between the inverter and the grid and meet the safety specification requirements.

[0079] Referring to Figure 6 , when the second switch K2 and the fourth switch K4 are turned on and the first switch K1 and the third switch K3 are turned off, the grid supplies power to the load through the second load branch 22, which can maximize the power supply to the load when the inverter fails.

[0080] Referring to Figure 7When the first switch K1, the second switch K2, the third switch K3 and the fourth switch K4 are all turned on, the first load branch and the second load branch are both turned on, the circuit can automatically distribute the current path according to the switch resistance of each line, and the power supply impedance is minimized.

[0081] With reference to Figure 8 , Figure 8 It is shown that the parallel and off-grid switching circuit provided by the embodiment of the application includes an extension branch 40. In some embodiments, the parallel and off-grid switching circuit further includes at least one extension branch 40, the first side of the extension branch 40 is electrically connected with the load bus 20, the second side of the extension branch 40 is used for being electrically connected with the extension device 50, and the extension branch 40 is provided with a controllable switch.

[0082] The extension branch 40 is directly electrically connected with the load bus 20, and can meet the requirements of off-grid safety specifications. The extension branch 40 is provided with a controllable switch, and the extension device 50 can be connected by controlling the controllable switch to be turned on, and the extension device 50 can be disconnected by controlling the controllable switch to be turned off, so that the capacity expansion has flexibility.

[0083] The number of the extension branch 40 and the number of the controllable switch on the extension branch 40 can be selected according to the actual application scene, which is not limited here. For example, the parallel and off-grid switching circuit can include one extension branch 40, and the extension branch 40 includes a fifth switch K5.

[0084] The type of the extension device 50 can be selected according to the actual application scene, which is not limited here. For example, the extension device 50 can be an inverter, a generator or a load.

[0085] With reference to Figure 9 , Figure 9 It is shown that the circuit topology of the embodiment applied to a three-phase inverter. The parallel and off-grid switching circuit provided by the embodiment of the application is suitable for both single-phase inverters and three-phase inverters.

[0086] With reference to Figure 10 , Figure 10The parallel-off-grid switching device provided by the embodiments of the present application is shown. One embodiment of the present application provides a parallel-off-grid switching device, which comprises a parallel grid module 60 and an off-grid module 70. The parallel grid module 60 comprises a parallel grid bus 10, a first power interface 61 and a second power interface 62. The first side of the parallel grid bus 10 is used for electrical connection with the alternating current side of an inverter circuit 80, and the second side of the parallel grid bus 10 is provided with a power grid interface 96; the first power interface 61 is electrically connected with the first side of the parallel grid bus 10; the second power interface 62 is electrically connected with the second side of the parallel grid bus 10; the off-grid module 70 comprises a first load branch 21, a second load branch 22, a load bus 20, a third power interface 71 and a fourth power interface 72. The first side of the load bus 20 is electrically connected with the first side of the first load branch 21 and the first side of the second load branch 22 respectively, and the second side of the load bus 20 is provided with a load interface 95; the third power interface 71 is electrically connected with the second side of the first load branch 21; the fourth power interface 72 is electrically connected with the second side of the second load branch 22; wherein the off-grid module 70 is detachably connected with the parallel grid module 60, the first power interface 61 is used for connecting with the third power interface 71, and the second power interface 62 is used for connecting with the fourth power interface 72, and the first load branch 21, the second load branch 22 and the parallel grid bus 10 are all provided with controllable switches.

[0087] The power grid interface 96 is used for electrical connection with a power grid, and the load interface 95 is used for electrical connection with a load.

[0088] In the parallel grid module 60, the parallel grid bus 10 is electrically connected between an inverter node and the power grid interface 96, and in the parallel grid state, the inverter circuit 80 can realize bidirectional flow of electrical energy with the power grid. The first power interface 61 is mainly used for realizing electrical connection between the inverter node and external devices, and the second power interface 62 is mainly used for realizing electrical connection between the second side of the parallel grid bus 10 and external devices.

[0089] In the off-grid module 70, the load bus 20 can be used for providing electrical energy transmitted by the first load branch 21 and / or the second load branch 22 to a load, so as to realize centralized distribution of electrical energy from the two branches to the load. The third power interface 71 is used for connecting with the first power interface 61, and the second power interface 62 is used for connecting with the fourth power interface 72, so as to realize connection between the parallel grid module 60 and the off-grid module 70.

[0090] The off-grid module 70 is connected with the grid-connected module 60 when the first power interface 61 is connected with the third power interface 71 and the second power interface 62 is connected with the fourth power interface 72, and at this time, the grid-off-grid switching device can realize switching between the grid-connected operation state and the off-grid operation state of the inverter circuit 80. When the first power interface 61 is disconnected with the third power interface 71 and the second power interface 62 is disconnected with the fourth power interface 72, the grid-off-grid switching device can only realize grid-connected operation. The off-grid module 70 is detachably connected with the grid-connected module 60, which can improve the flexibility of configuration of the grid-off-grid switching device, and when only grid-connected function is needed, the off-grid module 70 does not need to be configured, thereby saving cost.

[0091] The connection design between the first power interface 61 and the third power interface 71 and between the second power interface 62 and the fourth power interface 72 ensures efficient transmission of power in the grid-connected state and provides necessary physical connection basis for independent operation in the off-grid state, and can realize smooth transition between the two operation states. In addition, the design of the first power interface 61, the second power interface 62, the third power interface 71 and the fourth power interface 72 can realize detachable connection between the grid-connected module 60 and the off-grid module 70, and more easily realize multi-machine parallel connection and power management.

[0092] According to the grid-off-grid switching device, the load bus 20 is electrically connected with the grid-connected bus 10 through at least two load branch lines, and the configuration of the load power supply path is more flexible, especially when the inverter node and the grid node need to be isolated, the power supply can be easily accessed from the corresponding node, and the isolation effect is improved.

[0093] In some embodiments, the grid-connected bus 10 is provided with a switching unit 30 including at least two levels of switches, and the connection node of the first power interface 61 with the grid-connected bus 10 is located between the switching unit 30 and the AC side of the inverter circuit 80.

[0094] At least two levels of switches are arranged between the connection node of the first power interface 61 with the grid-connected bus 10 and the grid node, and when the switching unit 30 is turned off, electrical isolation between the inverter node and the grid node can be realized.

[0095] When operating in off-grid mode, the first power interface 61 is connected with the third power interface 71, and the inverter circuit 80 supplies power to the load through the first load branch line 21, which can realize minimum power supply impedance and reduce energy loss.

[0096] In some embodiments, the connection node of the second power interface 62 with the grid-connected bus 10 is located between two adjacent switches in the switching unit 30.

[0097] The second power interface 62 is provided with at least one switch between the connection node and the inversion node of the grid-connected bus 10, and at least one switch between the connection node and the grid node. When the inversion node supplies power to the load through the first load branch 21, the switch in the control switch unit 30 is turned off, and there are at least two levels of switches turned off between the inversion node and the grid node, so that electrical isolation between the inversion node and the grid node can be realized.

[0098] In some embodiments, the off-grid module 70 further comprises an expansion interface electrically connected to the load bus 20.

[0099] The expansion interface is mainly used for connecting the expansion device 50 to realize parallel operation of multiple devices. The types of the expansion device 50 include but are not limited to inverters, generators or loads, etc. The expansion interface is electrically connected to the load bus 20, and can meet the requirements of off-grid safety specifications.

[0100] One embodiment of the present application provides an inverter comprising the aforementioned grid-connected / off-grid switching circuit or the aforementioned grid-connected / off-grid switching device.

[0101] The grid-connected / off-grid switching circuit or the grid-connected / off-grid switching device is mainly used for switching the inverter between the grid-connected working state and the off-grid working state.

[0102] The structure and working principle of the grid-connected / off-grid switching circuit and the grid-connected / off-grid switching device can refer to the aforementioned embodiments, which will not be described here.

[0103] According to the inverter of the present application, the load bus 20 is electrically connected to the grid-connected bus 10 through at least two load branches, and the configuration of the load power supply path is more flexible, especially when the inversion node and the grid node need to be isolated, it is convenient to access the power supply from the corresponding node, and the isolation effect is improved.

[0104] Reference Figure 11 , Figure 11 An inverter provided by an embodiment of the present application is shown. In some embodiments, the inverter comprises an inverter circuit 80, a voltage detection circuit 91, a first current detection circuit 92, a second current detection circuit 93 and a driving unit 94. The AC side of the inverter circuit 80 is electrically connected to the inversion node; the input ends of the voltage detection circuit 91 are electrically connected to the AC side of the inverter circuit 80, the load node and the grid node respectively; the input end of the first current detection circuit 92 is electrically connected to the AC side of the inverter circuit 80; the input end of the second current detection circuit 93 is electrically connected to the grid node; the input ends of the driving unit 94 are electrically connected to the output ends of the voltage detection circuit 91, the output end of the first current detection circuit 92 and the output end of the second current detection circuit 93 respectively, and the output end of the driving unit 94 is electrically connected to the driving end of each controllable switch.

[0105] The direct current side of the inverter circuit 80 can be electrically connected with the photovoltaic module and the energy storage device, and the inverter circuit 80 is mainly used for converting the direct current output by the photovoltaic module into alternating current. The alternating current side of the inverter circuit 80 is electrically connected with the inverter node, and is mainly used for providing the converted alternating current to the inverter node.

[0106] The voltage detection circuit 91 detects the voltage of the alternating current side of the inverter circuit 80, the load node and the grid node, so as to determine whether the inverter circuit 80, the load or the grid is faulty.

[0107] The first current detection circuit 92 is used for detecting the current of the alternating current side of the inverter circuit 80, so as to determine whether the inverter circuit 80 is faulty. For example, if the first current detection circuit 92 detects that the current of the alternating current side of the inverter circuit 80 is too large, the inverter circuit 80 can be short-circuit faulty; if the first current detection circuit 92 detects that the current of the alternating current side of the inverter circuit 80 is close to zero, the inverter circuit 80 can be open-circuit faulty.

[0108] The second current detection circuit 93 is used for detecting the current of the grid node, so as to determine whether the grid is faulty. For example, if the second current detection circuit 93 detects that the current of the grid node is too large, the grid can be short-circuit faulty; if the second current detection circuit 93 detects that the current of the grid node is close to zero, the grid can be open-circuit faulty.

[0109] The driving unit 94 is mainly used for driving the corresponding line to be turned on according to the fault condition of the inverter circuit 80 and the grid, so as to realize the switching between the grid-connected state and the off-grid state. For example, when the inverter circuit 80 is faulty, the driving unit 94 can drive the second load branch to be turned on, the first load branch to be turned off, and the switch arranged between the connection node of the second load branch and the grid on the grid-connected branch to be turned on, so that the grid supplies power to the load through the second load branch; when the grid is faulty, the driving unit 94 can drive the first load branch to be turned on, the second load branch to be turned off, and the switch in the switch unit 30 on the grid-connected branch to be turned off, so that the inverter circuit 80 supplies power to the load through the second load branch.

[0110] Although the embodiments of the present application have been shown and described, those skilled in the art can understand that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and purposes of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. A grid-tie switching circuit, comprising: The parallel-off-grid switching circuit has an inversion node, a power grid node and a load node, and comprises: a first load branch, a second load branch, a load bus and a grid-connected bus, a first side of the grid-connected bus is electrically connected with the inversion node, a second side of the grid-connected bus is electrically connected with the power grid node, a first side of the first load branch is electrically connected with a first side of the grid-connected bus, a first side of the second load branch is electrically connected with a second side of the grid-connected bus, a second side of the first load branch and a second side of the second load branch are both electrically connected with a first side of the load bus, and a second side of the load bus is electrically connected with the load node. The first load branch, the second load branch and the grid-connected bus are all provided with controllable switches.

2. The on-grid and off-grid switching circuit of claim 1, wherein, The grid-connected bus is provided with a switching unit comprising at least two switches, and a connection node of the first side of the first load branch with the grid-connected bus is located between the switching unit and the inversion node.

3. The on-grid / off-grid switching circuit of claim 2, wherein, A connection node of the first side of the second load branch with the grid-connected bus is located between two adjacent switches in the switching unit.

4. The on-grid / off-grid switching circuit according to any one of claims 1-3, characterized in that, The parallel-off-grid switching circuit further comprises: at least one extension branch, a first side of the extension branch is electrically connected with the load bus, a second side of the extension branch is used for being electrically connected with an extension device, and the extension branch is provided with a controllable switch.

5. A grid-tie and off-grid switching device, characterized by comprises: a grid-connected module, comprising: a grid-connected bus, a first side of the grid-connected bus is used for being electrically connected with an alternating current side of an inversion circuit, and a second side of the grid-connected bus is provided with a power grid interface; a first power interface, which is electrically connected with the first side of the grid-connected bus; a second power interface, which is electrically connected with the second side of the grid-connected bus; an off-grid module, comprising: a first load branch and a second load branch; a load bus, a first side of the load bus is electrically connected with the first side of the first load branch and the first side of the second load branch respectively, and a second side of the load bus is provided with a load interface; a third power interface, which is electrically connected with a second side of the first load branch; a fourth power interface, which is electrically connected with a second side of the second load branch; The off-grid module is detachably connected with the grid-connected module, the first power interface is used for being connected with the third power interface, the second power interface is used for being connected with the fourth power interface, and the first load branch, the second load branch and the grid-connected bus are all provided with controllable switches.

6. The on-grid and off-grid switching device according to claim 5, characterized in that, The grid-connected bus is provided with a switching unit comprising at least two switches, and a connection node of the first power interface with the grid-connected bus is located between the switching unit and the alternating current side of the inversion circuit.

7. The on-grid and off-grid switching device according to claim 6, characterized in that, A connection node of the second power interface with the grid-connected bus is located between two adjacent switches in the switching unit.

8. The off-grid switching device according to any of claims 5-7, characterized in that, The off-grid module further comprises: an extension interface, which is electrically connected with the load bus.

9. An inverter, characterized by comprising: comprises the parallel-off-grid switching circuit according to any one of claims 1-4 or the parallel-off-grid switching device according to any one of claims 5-8.

10. The inverter of claim 9, wherein, The inverter comprises: an inversion circuit, an alternating current side of the inversion circuit is electrically connected with an inversion node; a voltage detection circuit, input ends of the voltage detection circuit are electrically connected with an alternating current side of the inverter circuit, a load node and a grid node respectively; a first current detection circuit, an input end of the first current detection circuit is electrically connected with the alternating current side of the inverter circuit; a second current detection circuit, an input end of the second current detection circuit is electrically connected with the grid node; a driving unit, input ends of the driving unit are electrically connected with output ends of the voltage detection circuit, the first current detection circuit and the second current detection circuit respectively, and output ends of the driving unit are electrically connected with driving ends of the controllable switches.

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