A grid-connected and off-grid switching architecture

Abstract

This application discloses a grid-connected / off-grid switching architecture for use in grid-connected power generation systems. It includes a transfer switch located between the three-phase AC circuit of an inverter and three loads. The three loads are connected to the three-phase AC circuit of the inverter via connection terminals. The transfer switch is adapted to connect the three-phase AC circuit of the inverter to the three loads correspondingly when the system is grid-connected. When the system is off-grid, the transfer switch is adapted to connect the three-phase AC circuit of the inverter to at least one of the three loads correspondingly to form a power supply loop. The advantages of this application are: compared to traditional methods of using energy storage systems to supply power to off-grid loads, this application eliminates the need for energy storage converters, energy storage batteries, and other external equipment to achieve the off-grid load function of a three-phase grid-connected inverter, thereby effectively saving user costs.

Description

Technical Field

[0001] This application relates to the field of new energy power generation technology, and in particular to a grid-connected / off-grid switching architecture. Background Technology

[0002] In practical applications of inverter systems, the AC side of the inverter system is connected to the power grid, and the load is connected between the AC side of the inverter system and the power grid. Inverter systems are mainly categorized into grid-connected and off-grid power generation systems. Off-grid power generation systems are equipped with off-grid energy storage devices, allowing the load to continue receiving power even when the inverter system is disconnected from the grid. Grid-connected power generation systems, however, only support grid-connected operation and cannot operate off-grid; that is, the inverter will cease functioning when the grid loses power, resulting in the load being unable to use electricity. To meet the power needs of users during abnormal mains power outages, users often need to select off-grid energy storage devices, which increases their operating costs. Utility Model Content

[0003] One objective of this application is to provide a switching architecture that can solve at least one of the defects in the above-mentioned background art.

[0004] To achieve at least one of the above objectives, the technical solution adopted in this application is as follows: a grid-connected / off-grid switching architecture applied to a grid-connected power generation system, including a transfer switch and a controller; the transfer switch is disposed between the three-phase AC circuit of the inverter and three loads, and the three loads are connected to the three-phase AC circuit of the inverter through connection terminals; the transfer switch is adapted to connect the three-phase AC circuit of the inverter to the three loads correspondingly when connected to the grid; the controller is communicatively connected to the inverter, and the controller is adapted to control the inverter to start up when disconnected from the grid, while the transfer switch connects the three-phase AC circuit of the inverter to at least one of the three loads to form a power supply circuit.

[0005] Preferably, the three load types include single-phase loads and three-phase loads; for three-phase loads being disconnected from the grid, the inverter performs three-phase disconnection; for single-phase loads being disconnected from the grid, the inverter performs single-phase disconnection; the transfer switch is adapted to connect the three-phase AC circuit of the inverter to the connection terminals of the three loads when the inverter performs three-phase disconnection; the transfer switch is adapted to connect a portion of the AC phase of the inverter to the neutral point of the three loads when the inverter performs single-phase disconnection, while connecting the remaining AC phase of the inverter to the connection terminals of the corresponding lines of the three loads.

[0006] Preferably, the transfer switch is adapted to connect one phase of the inverter's AC side to the neutral point of the three loads when the inverter performs single-phase off-grid operation, while connecting the remaining two phases of the inverter's AC side to the connection terminals of the corresponding two of the three loads.

[0007] Preferably, the transfer switch is a multi-contact switch, which includes a first contact and a second contact; the first contact is located at the neutral point of the three loads, and the second contact is located at the connection terminal of one of the three loads; the transfer switch is adapted to engage with the first contact when performing single-phase off-grid operation, and the transfer switch is adapted to engage with the second contact when the inverter performs three-phase off-grid operation.

[0008] Preferably, the transfer switch includes a first switch and a second switch; the first switch is disposed between one phase of the AC side of the inverter and the neutral point of the three loads, and the second switch is disposed between one phase of the AC side of the inverter and the terminal of one of the three loads; the first switch is adapted to be closed when performing single-phase off-grid operation, at which time the second switch is in the open state; the second switch is adapted to be closed when the inverter performs three-phase off-grid operation, at which time the first switch is in the open state.

[0009] Preferably, each phase of the three-phase AC circuit of the inverter is connected to the corresponding path of the three loads and the neutral point by the aforementioned transfer switch, and the three transfer switches are redundant with each other.

[0010] Preferably, the controller is also communicatively connected to the transfer switch, and the controller is adapted to identify the state of the power grid and control the transfer switch to perform corresponding actions.

[0011] Preferably, the transfer switch is communicatively connected to the inverter, and the controller is communicatively connected to the inverter; the controller is adapted to send a control signal to the inverter to control the operation of the transfer switch, and the inverter is adapted to forward the received control signal to the transfer switch.

[0012] Preferably, the changeover switch is adapted to communicate independently with the controller, and the controller directly sends control signals to the changeover switch.

[0013] Preferably, in a grid-connected power generation system, the three-phase AC circuit of the inverter is connected to the power grid via a circuit breaker, the controller is communicatively connected to the circuit breaker, the controller is adapted to control the circuit breaker to close when connected to the grid, and the controller is adapted to control the circuit breaker to open when disconnected from the grid.

[0014] Compared with the prior art, the beneficial effects of this application are as follows:

[0015] Compared to the traditional method of using energy storage systems to power off-grid loads, this application can realize the off-grid load function of a three-phase grid-connected inverter without configuring energy storage converters, energy storage batteries and other external equipment, thereby effectively saving user costs. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the architecture of Embodiment 1 of this application.

[0017] Figure 2 This is a schematic diagram of the architecture for grid connection in Embodiment 1 of this application.

[0018] Figure 3 This is a schematic diagram of the architecture for three-phase off-grid operation in Embodiment 1 of this application.

[0019] Figure 4 This is a schematic diagram of the architecture for single-phase off-grid operation in Embodiment 1 of this application.

[0020] Figure 5 This is a schematic diagram of the architecture of Embodiment 2 of this application.

[0021] Figure 6 This is a schematic diagram of the architecture of Embodiment 3 of this application.

[0022] In the diagram: power generation unit 110, inverter 120, three-way load 200, power grid 300, transfer switch 410, controller 420. Detailed Implementation

[0023] The present application will now be further described in conjunction with specific embodiments. It should be noted that, in the description of this specification, the use of terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicates that the specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0024] In the description of this application, it should be noted that the directional terms such as "center", "lateral", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", and "counterclockwise" indicate the orientation and positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. They should not be construed as limiting the specific protection scope of this application.

[0025] It should be noted that the terms "first," "second," etc., in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0026] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0027] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0028] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0029] To make it easier to understand, we can first give a simple description of the traditional architecture of grid-connected power generation systems.

[0030] like Figure 1As shown, the grid-connected power generation system mainly includes a power generation unit 110 and an inverter 120. The inverter 120 can be labeled as DC / AC. The DC side of the inverter 120 can be connected to the power generation unit 110. The three-phase AC circuits L1, L2, and L3 of the inverter 120 can be connected to the power grid 300 through a circuit breaker K. The three-phase AC circuits L1, L2, and L3 of the inverter 120 are also connected to three loads 200, which include loads Load1, Load2, and Load3. Load1 is connected to the single-phase AC circuit L1 of the inverter 120 through connection terminal a1, Load2 is connected to the single-phase AC circuit L2 of the inverter 120 through connection terminal a2, and Load3 is connected to the single-phase AC circuit L3 of the inverter 120 through connection terminal a3. The connection point for the three loads 200 is located between the AC side of the inverter 120 and the circuit breaker K; the circuit breaker K is generally a normally open switch.

[0031] It should be understood that grid-connected power generation systems can be applied to photovoltaic power generation, wind power generation, and hydropower generation, etc. The type of power generation unit 110 varies depending on the power generation scenario. Taking photovoltaic power generation as an example, the power generation unit 110 of its grid-connected power generation system uses photovoltaic modules (PV). There can be multiple photovoltaic modules (PV), which can be connected to the DC side of the inverter 120 through series or parallel connections. If the grid-connected power generation system adopts a three-phase four-wire control method, the neutral point of the three loads 200 and the power grid 300 are also connected via the N line.

[0032] When the grid-connected power generation system described above is connected to the grid, simply closing circuit breaker K allows inverter 120 to supply the electrical energy generated by power generation unit 110 to the three loads 200 and / or the power grid 300. Under conventional control methods, when the grid-connected power generation system experiences an abnormal power outage due to a fault or other reasons, causing it to disconnect from the grid, inverter 120 will automatically stop operating. This is because the grid-connected power generation system is equipped with an anti-islanding protection mechanism; islanding can cause equipment damage and a decline in power quality. Therefore, when a power outage is detected in the power grid 300, inverter 120 will automatically trip and disconnect from the power grid 300, thereby stopping power generation; at this time, circuit breaker K is also in the open state.

[0033] This application provides a grid-connected / off-grid switching architecture, applied to the aforementioned grid-connected power generation system, which ensures that the inverter 120 can supply power to at least a portion of the loads of the three loads 200 in off-grid mode. For example... Figure 1As shown, one preferred embodiment includes a transfer switch 410 and a controller 420; the transfer switch 410 is disposed between the three-phase AC circuit of the inverter 120 and the three loads 200, and the controller 420 is communicatively connected to the inverter 120.

[0034] When the grid-connected power generation system is in grid-connected mode, the transfer switch 410 can connect the three-phase AC circuit of the inverter 120 to the three loads 200, so that the power generation unit 110 can supply power to the three loads 200. When the grid-connected power generation system is in off-grid mode, the inverter 120 will automatically shut down. At this time, the controller 120 can control the inverter 120 to restart, and the transfer switch 410 can connect the three-phase AC circuit of the inverter 120 to at least one of the three loads 200 to form a power supply loop.

[0035] Understandably, when the grid-connected power generation system is operating normally, it can be connected to the grid using traditional methods to ensure the normal power supply to the three loads 200. However, when the grid-connected power generation system is disconnected from the grid, the controller 120 can restart the inverter 120 that has been shut down. At the same time, the transfer switch 410 can connect all or part of the phase circuits of the inverter 120 to the three loads 200 according to the off-grid type of the system, so that all or part of the loads can still operate normally. Compared with the traditional method of using an energy storage system to supply power to off-grid loads, this application can realize the off-grid load function of the three-phase grid-connected inverter without configuring an energy storage converter, energy storage battery and other external equipment, thereby effectively saving user costs.

[0036] It should be understood that the three loads 200 include both single-phase and three-phase loads. For three-phase loads to be disconnected from the grid, inverter 120 needs to perform three-phase disconnection; for single-phase loads to be disconnected from the grid, inverter 120 needs to perform single-phase disconnection. Three-phase disconnection means that inverter 120 needs to supply power to the three loads 200 through three-phase control, while single-phase disconnection means that inverter 120 needs to supply power to some of the loads through single-phase control. Therefore, in the three-phase disconnection state, the three loads 200 can operate normally under the control of transfer switch 410 and controller 420. However, in the single-phase disconnection state, at least one load needs to be sacrificed to create a single-phase power supply circuit to ensure the normal operation of the remaining loads.

[0037] Specifically, the transfer switch 410 can connect the three-phase AC circuit of the inverter 120 to the corresponding connection terminals of the three loads 200 when the inverter performs three-phase off-grid operation. When the inverter performs single-phase off-grid operation, the transfer switch 410 can connect a portion of the AC side of the inverter 120 to the neutral point of the three loads 200, while simultaneously connecting the remaining AC side phases of the inverter 120 to the corresponding connection terminals of the three loads 200; thus, the remaining AC side phases of the inverter 120 and the portion of the phases connected to the neutral point of the three loads 200 form a single-phase power supply circuit to provide single-phase power to the corresponding load.

[0038] Understandably, for single-phase off-grid operation, one phase of the AC side of inverter 120 can be connected to the neutral point of the three loads 200, while the remaining two phases of the AC side of inverter 120 are connected to the corresponding two loads. This allows sacrificing one load to ensure normal single-phase operation of the two loads; conversely, sacrificing two loads can also ensure normal single-phase operation of one load. However, to ensure as many loads as possible operate, it is necessary to minimize the sacrifice of loads to ensure the operation of as many loads as possible. Therefore, in this embodiment, it is preferable to sacrifice one load to ensure the normal operation of the remaining two loads. Specifically, when the inverter performs single-phase off-grid operation, the transfer switch 410 can connect one phase of the AC side of inverter 120 to the neutral point of the three loads 200, while simultaneously connecting the remaining two phases of the AC side of inverter 120 to the corresponding two connection terminals of the three loads 200.

[0039] There are various specific architectures for the changeover switch 410 that can achieve the above functions. For ease of understanding, the following will provide a detailed explanation through three specific embodiments.

[0040] Example 1:

[0041] like Figures 1 to 4 As shown, the changeover switch 410 is a multi-contact switch, which includes a first contact k1 and a second contact k2. The first contact k1 is located at the neutral point of the three loads 200, and the second contact k2 is located at the connection terminal of one of the three loads 200.

[0042] When the grid-connected power generation system is in grid-connected state, the transfer switch 410 can be activated by the second contact k2, thereby connecting the three-phase AC circuit of the inverter 120 to the three loads 200, so that the power generation unit 110 can supply power to the three loads 200; at this time, the circuit breaker K is in the closed state.

[0043] When the grid-connected power generation system is in a three-phase off-grid state, the inverter 120 will automatically shut down. At this time, the controller 120 can control the inverter 120 to restart. At the same time, the transfer switch 410 and the second contact k2 are engaged, thereby connecting the three-phase AC circuit of the inverter 120 to the three loads 200, so that the power generation unit 110 can supply power to the three loads 200. At this time, the circuit breaker K is in the open state.

[0044] When the grid-connected power generation system is in a single-phase off-grid state, the inverter 120 will automatically shut down. At this time, the controller 120 can control the inverter 120 to restart. Simultaneously, the transfer switch 410 and the first contact k1 are engaged, thereby connecting one phase of the AC side of the inverter 120 to the neutral point of the three loads 200, so that the other two phases of the inverter 120 and the phase connected to the neutral point of the three loads 200 form a single-phase power supply circuit. Thus, the power generation unit 110 can supply power to two of the loads. At this time, the circuit breaker K is in the open state.

[0045] To facilitate understanding, the following detailed explanation will take the sacrifice of load Load1 during single-phase off-grid operation as an example.

[0046] like Figure 1 As shown, the transfer switch 410 is installed in the L1 phase circuit of the inverter 120. The first contact k1 is set at the neutral point of the three loads 200, and the second contact k2 is set at the connection terminal a1 of the load Load1. The L2 and L3 phase circuits of the inverter 120 are directly connected to the connection terminals a2 and a3 of the loads Load2 and Load3, respectively.

[0047] When the grid-connected power generation system is in grid-connected state, such as Figure 2 As shown, the changeover switch 410 can be engaged with the second contact k2, thereby connecting the three-phase AC circuits L1 to L3 of the inverter 120 to the connection terminals a1 to a3 of the three loads 200 respectively, so that the generator unit 110 can supply power to the three loads 200; at this time, the circuit breaker K is in the closed state.

[0048] When the grid-connected power generation system is in a three-phase off-grid state, such as Figure 3 As shown, the inverter 120 will automatically shut down. At this time, the controller 120 can control the inverter 120 to restart. At the same time, the transfer switch 410 and the second contact k2 are engaged, thereby connecting the three-phase AC circuits L1 to L3 of the inverter 120 to the connection terminals a1 to a3 of the three loads 200 respectively, so that the power generation unit 110 can supply power to the three loads 200. At this time, the circuit breaker K is in the open state.

[0049] When the grid-connected power generation system is in a single-phase off-grid state, such as Figure 4As shown, the inverter 120 will automatically shut down. At this time, the controller 120 can control the inverter 120 to restart. At the same time, the transfer switch 410 and the first contact k1 are engaged, thereby connecting the L1 phase circuit of the inverter 120 to the neutral point of the three loads 200, so that the L2 and L3 phase circuits of the inverter 120 form a single-phase power supply circuit with the L1 phase circuit respectively; thus, the power generation unit 110 can supply power to the loads Load2 and Load3; at this time, the circuit breaker K is in the open state.

[0050] In this embodiment, as Figures 1 to 4 As shown, the controller 420 can communicate with the transfer switch 410. The controller 420 can identify the state of the power grid 300 and control the transfer switch 410 to perform corresponding actions based on the identification results.

[0051] Specifically, when the power grid 300 is powered on, the controller 420 can detect and identify that the power grid 300 is normal. At this time, the controller 420 can control the changeover switch 410 to engage with the second contact k2 based on the detection result. When the power grid 300 is de-energized, the controller 420 can detect and identify that there is no power grid 300. At this time, the controller 420 can control the changeover switch 410 to engage with the first contact k1 or the second contact k2 based on the detection result and the type of the three loads 200.

[0052] It is understandable that the controller 420 needs to control not only the transfer switch 410 but also supply power to the inverter 120. Therefore, the controller 420 can communicate with both the inverter 120 and the transfer switch 410, or it can communicate with the inverter 120 and the transfer switch 410. In this case, the controller 420 can send control signals to the inverter 120 to control the operation of the transfer switch 410, and the inverter 120 can forward the received control signals to the transfer switch 410. Both methods can meet the practical needs of this application. Considering that the transfer switch 410 may need to be installed inside the inverter 120, this embodiment preferably uses the method of the controller 420 communicating with the inverter 120 and the inverter 120 communicating with the transfer switch 410.

[0053] In this embodiment, to facilitate the grid connection and off-grid control of the entire grid-connected power generation system, such as... Figures 1 to 4 As shown, the controller 420 can also communicate with the circuit breaker K; thus, the controller 420 can control the circuit breaker K to be energized and closed when connected to the grid, and control the circuit breaker K to be de-energized and open when disconnected from the grid.

[0054] For ease of understanding, the process of switching from grid connection to off-grid and from off-grid to grid connection in Example 1 will be described in detail below.

[0055] When inverter 120 operates in off-grid mode (single-phase or three-phase off-grid), the grid 300 recovers from a power outage. At this time, controller 420 detects the grid 300 recovery and sends grid 300 status information to inverter 120. During off-grid operation, inverter 120 continuously monitors the grid 300 status information transmitted from controller 420. When grid 300 recovery is detected, inverter 120 shuts down and sends a shutdown completion flag to controller 420. After receiving the shutdown completion information from inverter 120, controller 420 sends a control signal to inverter 120 to activate the transfer switch 410 and the second contact k2. Inverter 120 then forwards this control signal to transfer switch 410 to execute the corresponding action. Simultaneously, controller 420 also sends a signal to circuit breaker K to close, causing circuit breaker K to close. After the transfer switch 410 completes its operation, it sends a completion signal to the inverter 120. Upon receiving the signal, the inverter 120 starts up in grid-connected operation mode.

[0056] When inverter 120 is operating in grid-connected mode, and grid 300 experiences a power outage, controller 420 cannot detect grid 300 and sends a status message indicating no grid 300 to inverter 120. During grid-connected operation, inverter 120 continuously monitors the grid 300 status information from controller 420. Upon receiving information that grid 300 has lost power, inverter 120 shuts down. Simultaneously, when controller 420 detects no grid 300, it controls circuit breaker K to open and then sends an off-grid start-up signal to inverter 120. At this time, inverter 120 performs a soft start-up according to the different operating modes of the three loads 200.

[0057] When the three loads 200 are single-phase loads, the inverter 120 operates in single-phase off-grid mode with a slow start; when the three loads 200 are three-phase loads, the inverter 120 operates in three-phase off-grid mode with a slow start. During the slow start process, the controller 420 starts working when its power supply requirements are met. At this time, it controls the transfer switch 410 through the off-grid operation mode information transmitted by the inverter 120. When the inverter 120 operates in single-phase off-grid mode, the transfer switch 410 engages with the first contact k1; when the inverter 120 operates in three-phase off-grid mode, the transfer switch 410 engages with the second contact k2; at the same time, the engagement completion information is transmitted to the inverter 120, and the inverter 120 operates stably off-grid until the voltage value before the grid 300 power failure is reached.

[0058] Example 2:

[0059] Compared to Embodiment 1, the difference in this embodiment is as follows: Figure 5As shown, the transfer switch 410 includes a first switch S1 and a second switch S2. The first switch S1 is located between one phase of the AC side of the inverter 120 and the neutral point of the three loads 200. The second switch S2 is located between one phase of the AC side of the inverter 120 and the terminal of the corresponding load among the three loads 200. The first switch S1 can be closed when the inverter 120 performs single-phase grid disconnection, at which time the second switch S2 is in the open state. The second switch S2 can be closed when the inverter 120 performs three-phase grid disconnection, at which time the first switch S1 is in the open state.

[0060] It is understood that the specific structure and working principle of the first switch S1 and the second switch S2 are well-known technologies to those skilled in the art, and therefore will not be described in detail here. The first switch S1 and the second switch S2 commonly use relays and contactors.

[0061] To facilitate understanding, the following detailed explanation will take the sacrifice of load Load1 during single-phase off-grid operation as an example.

[0062] like Figure 5 As shown, the first switch S1 is installed between the L1 phase circuit of the inverter 120 and the neutral point of the three loads 200, and the second switch S2 is installed between the L1 phase circuit of the inverter 120 and the connection terminal a1 of the load Load1. The L2 and L3 phase circuits of the inverter 120 are directly connected to the connection terminals a2 and a3 of the loads Load2 and Load3, respectively.

[0063] When the grid-connected power generation system is in grid-connected state, the second switch S2 is closed, the first switch S1 is open, and the circuit breaker K is closed. When the grid-connected power generation system is in three-phase off-grid state, the second switch S2 is closed, the first switch S1 is open, and the circuit breaker K is open. When the grid-connected power generation system is in single-phase off-grid state, the second switch S2 is open, the first switch S1 is closed, and the circuit breaker K is open.

[0064] Example 3:

[0065] The difference between this embodiment and Embodiments 1 and 2 is that: Figure 6 As shown, each phase of the three-phase AC circuit of inverter 120 is connected to the corresponding path of the three loads 200 and the neutral point by a transfer switch 410, and the three transfer switches 410 are redundant with each other.

[0066] It is understood that in this embodiment, the changeover switch 410 can be a multi-contact switch as described in Embodiment 1, or a dual-switch structure as described in Embodiment 2. For ease of understanding, the following detailed explanation will take the use of a multi-contact switch 410 as an example.

[0067] Specifically, such as Figure 6As shown, the changeover switch 410 of the L1 phase circuit installed in inverter 120 has a first contact ka1 and a second contact ka2. The first contact ka1 is located at the neutral point of the three loads 200, and the second contact ka2 is located at the connection terminal a1 of load Load1. The changeover switch 410 of the L2 phase circuit installed in inverter 120 has a first contact kb1 and a second contact kb2. The first contact kb1 is located at the neutral point of the three loads 200, and the second contact kb2 is located at the connection terminal a2 of load Load2. The changeover switch 410 of the L3 phase circuit installed in inverter 120 has a first contact kc1 and a second contact kc2. The first contact kc1 is located at the neutral point of the three loads 200, and the second contact kc2 is located at the connection terminal a3 of load Load3.

[0068] It is understandable that, taking the sacrifice of load Load1 when performing single-phase off-grid operation as an example.

[0069] When the grid-connected power generation system is in grid-connected state, the three transfer switches 410 are attracted to the second contacts ka2, kb2 and kc2 respectively, and the circuit breaker K is closed.

[0070] When the grid-connected power generation system is in a three-phase off-grid state, the three transfer switches 410 are engaged with the second contacts ka2, kb2 and kc2 respectively, and the circuit breaker K is disconnected.

[0071] When the grid-connected power generation system is in a single-phase off-grid state, the changeover switch 410 connected to the L1 phase circuit is engaged with its first contact ka1, and the other two changeover switches 410 are engaged with their second contacts kb2 and kc2 respectively, and the circuit breaker K is open. If the changeover switch 410 connected to the L1 phase circuit fails, the changeover switch 410 connected to the L2 phase circuit can be controlled to perform the corresponding function. That is, the changeover switch 410 connected to the L2 phase circuit is controlled to engage with its first contact kb1. At this time, if the changeover switch 410 connected to the L1 phase circuit can engage with its second contact ka2, it will do so; otherwise, it will remain open. Simultaneously, the changeover switch 410 connected to the L3 phase circuit will engage with its second contact kc2. Of course, for a failure of the changeover switch 410 connected to the L1 phase circuit, the function can also be replaced by the changeover switch 410 connected to the L3 phase circuit.

[0072] The basic principles, main features, and advantages of this application have been described above. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely the principles of this application. Various changes and modifications can be made to this application without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection claimed by this application is defined by the appended claims and their equivalents.

Claims

1. A parallel and off-grid switching architecture applied to a grid-connected power generation system, in which a three-way load is connected to a three-phase circuit of an AC side of an inverter through a connection terminal, characterized in that, include: Changeover switch; The transfer switch is located between the three-phase AC circuit and the three loads on the inverter side; as well as Controller; the controller is communicatively connected to the inverter; The transfer switch is adapted to connect the three-phase AC circuit of the inverter to the three loads correspondingly when connected to the grid; The controller is adapted to start the inverter when it is off-grid, and the transfer switch connects the three-phase AC circuit of the inverter to at least one of the three loads to form a power supply circuit.

2. The on- and off-grid switching architecture of claim 1, wherein, The three-phase load types include single-phase loads and three-phase loads; for three-phase loads going offline, the inverter performs three-phase offline; for single-phase loads going offline, the inverter performs single-phase offline. The transfer switch is adapted to connect the three-phase AC circuit of the inverter to the three loads when the inverter performs three-phase off-grid operation; the transfer switch is adapted to connect some phases of the inverter's AC side to the neutral point of the three loads when the inverter performs single-phase off-grid operation, while connecting the remaining phases of the inverter's AC side to the corresponding connection terminals of the three loads.

3. The on- and off-grid switching architecture of claim 2, wherein, The transfer switch is adapted to connect one phase of the inverter's AC side to the neutral point of the three loads when the inverter performs single-phase off-grid operation, while connecting the remaining two phases of the inverter's AC side to the corresponding connection terminals of the three loads.

4. The on- and off-grid switching architecture of claim 3, wherein, The changeover switch is a multi-contact switch, and the changeover switch includes: The first contact; the first contact is located at the neutral point of the three-way load; and The second contact is located at the connection end of one of the three loads. The transfer switch is adapted to engage with the first contact when performing single-phase off-grid operation, and the transfer switch is adapted to engage with the second contact when the inverter performs three-phase off-grid operation.

5. The on- and off-grid switching architecture of claim 3, wherein, The changeover switch includes: The first switch; the first switch is located between one phase of the AC side of the inverter and the neutral point of the three loads; and The second switch is located between the terminals of one phase of the AC side of the inverter and one of the corresponding loads among the three loads. The first switch is adapted to be closed when performing single-phase off-grid operation, at which time the second switch is in the open state; the second switch is adapted to be closed when the inverter performs three-phase off-grid operation, at which time the first switch is in the open state.

6. The on- and off-grid switching architecture of claim 3, wherein, Each phase of the three-phase AC circuit of the inverter is connected to the corresponding path of the three loads and the neutral point by the aforementioned transfer switch, and the three transfer switches are redundant with each other.

7. The parallel off-grid switching architecture of any of claims 1-6, wherein, The controller is also in communication with the transfer switch, and the controller is adapted to identify the state of the power grid and control the transfer switch to perform corresponding actions.

8. The on- and off-grid switching architecture of claim 7, wherein, The transfer switch is communicatively connected to the inverter, and the controller is communicatively connected to the inverter. The controller is adapted to send a control signal to the inverter to control the operation of the transfer switch, and the inverter is adapted to forward the received control signal to the transfer switch.

9. The on- and off-grid switching architecture of claim 7, wherein, The changeover switch is adapted to communicate independently with the controller, and the controller directly sends control signals to the changeover switch.

10. The on- and off-grid switching architecture of claim 7, wherein, In a grid-connected power generation system, the three-phase AC circuit of the inverter is connected to the power grid through a circuit breaker; The controller is communicatively connected to the circuit breaker, and the controller is adapted to control the circuit breaker to close when connected to the grid, and the controller is adapted to control the circuit breaker to open when disconnected from the grid.

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