Grid-connected power converter and power supply system

Abstract

Provided in the present application are a grid-connected power converter and a power supply system. The grid-connected power converter comprises a direct-current bus, a first direct-current switch, a second direct-current switch, a soft-start circuit, an inverter circuit, a grid-connected switch and a controller, wherein a direct-current input end of the inverter circuit is configured to be connected to a photovoltaic module or an energy storage battery by means of the direct-current bus; the first direct-current switch and the second direct-current switch are both connected in series to the direct-current bus; the soft-start circuit is connected in parallel to the second direct-current switch, and is configured to regulate the voltage across the second direct-current switch; an alternating-current output end of the inverter circuit is configured to be connected to a power grid by means of the grid-connected switch; and the controller is configured to control the first direct-current switch to be closed, control the second direct-current switch to be closed when the voltage across the second direct-current switch is less than or equal to a first voltage threshold value, and control the grid-connected switch to be closed after the second direct-current switch is closed. The present application can reduce switch ablation, and ensure the grid-connection safety of the grid-connected power converter; moreover, the present application can reduce the production costs, and has high applicability.

Description

Grid-connected power converter and power supply system

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of China on February 23, 2024, with application number 202410206217.1, and priority to the Chinese patent application entitled “Grid-connected power converter and power supply system”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of power supply control technology, and in particular to a grid-connected power converter and power supply system. Background Art

[0003] The grid-connected power converter can be disconnected from the grid by controlling the switch to be disconnected. When the grid-connected power converter control switch is switched from open to closed, the grid-connected power converter is connected to the grid and can supply power to the grid.

[0004] However, when the switch is open, a voltage difference exists across the terminals. When the grid-connected power converter is connected to the grid, the moment the switch switches from open to closed, a large current is generated due to the voltage across the terminals, causing switch corrosion, which in turn affects the grid connection safety of the grid-connected power converter. Therefore, how to reduce switch corrosion to ensure the safe connection of the grid-connected power converter is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0005] The present application provides a grid-connected power converter and power supply system, which can reduce switch ablation, ensure the grid connection safety of the grid-connected power converter, reduce production costs, and have high applicability.

[0006] In the first aspect, the present application provides a grid-connected power converter, which includes a DC bus, a first DC switch, a second DC switch, a soft-start circuit, an inverter circuit, a grid-connected switch and a controller, wherein the inverter circuit is used to convert DC power into AC power, the DC input end of the inverter circuit is used to be connected to a photovoltaic component or an energy storage battery through the DC bus, the first DC switch and the second DC switch are both connected in series to the DC bus, the soft-start circuit is connected in parallel with the second DC switch, the soft-start circuit is used to adjust the voltage across the second DC switch, and the AC output end of the inverter circuit is used to be connected to the power grid through the grid-connected switch; the controller is used to control the first DC switch to close, and after the first DC switch is closed and when the voltage across the second DC switch is less than or equal to the first voltage threshold, the second DC switch is controlled to close, and after the second DC switch is closed, the grid-connected switch is controlled to close. In the present application, when the grid-connected power converter is switched to grid-connected, the controller can control the first DC switch and the second DC switch to close when the voltage at both ends is less than or equal to the first voltage threshold, so as to reduce switch burning, thereby achieving safe grid connection of the grid-connected power converter. Only one grid-connected switch is set in the grid-connected power converter to connect to the power grid, which can effectively reduce production costs.

[0007] In conjunction with the first aspect, in a first possible implementation, the controller is configured to control the grid-connected switch to close after the second DC switch is closed and when the voltage across the grid-connected switch is less than or equal to a second voltage threshold. In this application, the grid-connected power converter controls the grid-connected switch to close when the voltage across the grid-connected switch is less than or equal to the second voltage threshold by the controller, thereby reducing ablation when the grid-connected switch is closed and further improving the grid-connected security of the grid-connected power converter.

[0008] In combination with any one of the first possible implementations of the first aspect to the first possible implementation of the first aspect, in a second possible implementation, the soft-start circuit includes a third DC switch; the controller is configured to control the first DC switch to close, and after the first DC switch is closed, control the third DC switch to close to adjust the voltage across the second DC switch, and after the third DC switch is closed and when the voltage across the second DC switch is less than or equal to the first voltage threshold, control the second DC switch to close. In the present application, the grid-connected power converter controls the closing order of the first DC switch, the second DC switch, and the third DC switch through the controller, so that the first DC switch and the second DC switch can be closed without causing ablation.

[0009] In combination with any one of the first possible implementations of the first aspect to the first aspect, in a third possible implementation, the soft-start circuit includes a third DC switch; the controller is used to control the first DC switch to close, and after the first DC switch is closed, the third DC switch is controlled to close to adjust the voltage across the second DC switch, and after the third DC switch is closed and when the voltage across the second DC switch is greater than or equal to a third voltage threshold, the first DC switch is controlled to open, and after the first DC switch is opened, the second DC switch is controlled to close, and after the second DC switch is closed and when the voltage across the first DC switch is greater than or equal to the third voltage threshold, the first DC switch is controlled to close, and the third voltage threshold is greater than the first voltage threshold. In the present application, the grid-connected power converter can remove the oxide layer of the first DC switch by controlling the first DC switch to close when the voltage across the two ends is greater than or equal to the third voltage threshold, thereby extending the service life of the first DC switch and ensuring the safe grid connection of the grid-connected power converter.

[0010] In combination with any one of the first aspects to the first possible implementation of the first aspect, in a fourth possible implementation, the soft-start circuit includes a third DC switch; the controller is used to control the first DC switch to close, and after the first DC switch is closed, control the third DC switch to close to adjust the voltage across the second DC switch, and after the third DC switch is closed and when the voltage across the second DC switch is greater than or equal to a third voltage threshold, control the second DC switch to close, and the third voltage threshold is greater than the first voltage threshold. In the present application, the grid-connected power converter can remove the oxide layer of the second DC switch by controlling the second DC switch to close when the voltage across the second DC switch is greater than or equal to the third voltage threshold, thereby extending the service life of the second DC switch and ensuring safe grid connection of the grid-connected power converter.

[0011] In the second aspect, the present application also provides a grid-connected power converter, which includes a DC bus, a first DC switch, a second DC switch, an inverter circuit, a grid-connected switch, and a controller, wherein the inverter circuit is used to convert DC power into AC power, the DC input end of the inverter circuit is used to connect to a photovoltaic module or an energy storage battery through the DC bus, the first DC switch and the second DC switch are both connected in series to the DC bus, and the AC output end of the inverter circuit is used to connect to the grid through the grid-connected switch; the controller is used to control the grid-connected switch to close when the voltage difference across the grid-connected switch is less than or equal to a second voltage threshold, and after the grid-connected switch is closed, control the first DC switch and the second DC switch to close. In the present application, when the grid-connected power converter is switched to the grid, the controller controls the grid-connected switch to close when the voltage across the two ends is less than or equal to the second voltage threshold, so as to reduce the erosion of the grid-connected switch, thereby achieving safe grid connection of the grid-connected power converter, and only one grid-connected switch is provided in the grid-connected power converter to connect to the grid, which can effectively reduce production costs.

[0012] In conjunction with the second aspect, in a first possible implementation, the controller is configured to control the first DC switch and the second DC switch to close after the grid-connected switch is closed and when the voltage difference between the first DC switch and the second DC switch is less than or equal to a first voltage threshold. In this application, the grid-connected power converter controls the first DC switch and the second DC switch to close when the voltage between the first DC switch and the second DC switch is less than or equal to the first voltage threshold by the controller, thereby reducing erosion of the first DC switch and the second DC switch and further improving the grid-connected security of the grid-connected power converter.

[0013] In combination with any one of the second aspect to the first possible implementation of the second aspect, in the second possible implementation, the grid-connected power converter further includes a third DC switch, the third DC switch being connected in parallel with the second DC switch; a controller for controlling the first DC switch to close, controlling the third DC switch to close after the first DC switch is closed, controlling the first DC switch to open after the third DC switch is closed and when the voltage difference across the second DC switch is greater than or equal to a third voltage threshold, controlling the second DC switch to close after the first DC switch is opened, controlling the first DC switch to close after the second DC switch is closed and when the voltage difference across the first DC switch is greater than or equal to a third voltage threshold, controlling the first DC switch to close, the third voltage threshold being greater than the first voltage threshold. In the present application, the grid-connected power converter can remove the oxide layer of the first DC switch by controlling the first DC switch to close when the voltage across the two ends is greater than or equal to the third voltage threshold, thereby extending the service life of the first DC switch and ensuring the safe grid connection of the grid-connected power converter.

[0014] In combination with any one of the second aspect to the first possible implementation of the second aspect, in a third possible implementation, the grid-connected power converter further includes a third DC switch, the third DC switch being connected in parallel with the second DC switch; the controller is configured to control the first DC switch to close, and after the first DC switch is closed, control the third DC switch to close, and after the third DC switch is closed and when the voltage difference across the second DC switch is greater than or equal to a third voltage threshold, control the second DC switch to close, the third voltage threshold being greater than the first voltage threshold. In the present application, the grid-connected power converter can remove the oxide layer of the second DC switch by controlling the second DC switch to close when the voltage across the second DC switch is greater than or equal to the third voltage threshold, thereby extending the service life of the second DC switch and ensuring safe grid connection of the grid-connected power converter.

[0015] In a third aspect, the present application also provides a power supply system, which includes an energy storage battery and the grid-connected power converter described in the first or second aspect above, and the grid-connected power converter is used to convert direct current from the energy storage battery into alternating current.

[0016] It should be understood that the implementation and beneficial effects of the above-mentioned aspects of the present application can be referenced to each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG1 is a schematic structural diagram of an energy storage power station provided in an embodiment of the present application;

[0018] FIG2 is a schematic structural diagram of a grid-connected power converter provided in an embodiment of the present application;

[0019] FIG3 is another structural diagram of a grid-connected power converter provided in an embodiment of the present application;

[0020] FIG4 is another structural diagram of a grid-connected power converter provided in an embodiment of the present application;

[0021] FIG5 is another structural diagram of a grid-connected power converter provided in an embodiment of the present application;

[0022] FIG6 is another structural diagram of the grid-connected power converter provided in an embodiment of the present application. DETAILED DESCRIPTION

[0023] The power supply system provided in the embodiments of the present application can be a new energy power station, an energy storage power station, a flexible power transmission system, or a microgrid, and is suitable for different application scenarios, such as photovoltaic power supply scenarios and energy storage power supply scenarios. For ease of understanding, the following description uses an energy storage power station as the power supply system and an energy storage power supply scenario as an example.

[0024] Please refer to Figure 1, which is a structural schematic diagram of an energy storage power station provided in an embodiment of the present application. The energy storage power station 100 shown in Figure 1 includes an energy storage battery 110 and a grid-connected power converter 120. The output end of the above-mentioned energy storage battery 110 is connected to the DC end of the grid-connected power converter 120, and the AC end of the grid-connected power converter 120 is connected to the power grid. When the energy storage power station 100 is connected to the power grid through the grid-connected power converter 120, the energy storage battery 110 can exchange electric energy with the power grid through the grid-connected power converter 120. Furthermore, the above-mentioned energy storage power station 100 can also be disconnected from the grid through the grid-connected power converter 120 to achieve energy utilization optimization.

[0025] The energy storage power station 100 provided in the embodiment of the present application is provided with multiple switches in the grid-connected power converter 120. When the above-mentioned multiple switches are disconnected, the grid-connected power converter 120 is disconnected from the grid, and the energy storage power station 100 is off-grid. On the contrary, the above-mentioned multiple switches are closed, the grid-connected power converter 120 is connected to the grid, and the energy storage power station 100 is grid-connected. The grid-connected power converter 120 can control the multiple switches to close when the voltage at both ends is small, so as to reduce the ablation of the switches and ensure the safety of grid connection. At the same time, the grid-connected power converter 120 is only provided with one grid-connected switch to connect to the grid, which can effectively reduce production costs.

[0026] The above is only an example of the application scenarios of the power supply system provided by this application, and is not an exhaustive list. This application does not limit the application scenarios.

[0027] It is understood that, as can be seen from the above content, the power supply system can achieve switching between the grid-connected state and the off-grid state by connecting the grid-connected power converter to the grid or off-grid. To this end, the embodiment of the present application provides a grid-connected power converter that can achieve off-grid and grid-connected state. For ease of understanding, the working principle of the grid-connected power converter provided in the embodiment of the present application is illustrated below with reference to Figures 2 to 6.

[0028] As shown in Figure 2, the grid-connected power converter 200 includes a DC bus, a first DC switch 220, a second DC switch 230, an inverter circuit 240, a grid-connected switch 250, a controller 260, and a soft-start circuit 270. The DC bus may specifically include a positive DC bus 211 and a negative DC bus 212. The first DC switch 220 is connected in series to the positive DC bus 211, and the second DC switch 230 is connected in series to the negative DC bus 212. The soft-start circuit 270 is connected in parallel to the second DC switch 230. The AC output terminal i3 of the inverter circuit 240 is connected to one end of the grid-connected switch 250, and the other end of the grid-connected switch 250 is connected to the power grid.

[0029] It is understood that, in the energy storage power supply scenario, the energy storage battery connected to the grid-connected power converter 200 in FIG2 can be understood as the energy storage battery 110 in the energy storage power station shown in FIG1 above. In addition, in the photovoltaic power supply scenario, the DC input terminal of the inverter circuit 240 in the grid-connected power converter 200 can be connected to a photovoltaic array, or, in the wind power supply scenario, the DC input terminal of the inverter circuit 240 in the grid-connected power converter 200 can also be connected to a wind power generation DC source. This application does not provide examples one by one here.

[0030] It is understood that when the first DC switch 220, the second DC switch 230, and the grid-connected switch 250 are all closed, the energy storage battery can exchange electrical energy with the grid through the grid-connected power converter 200, that is, the grid-connected power converter 200 is connected to the grid. When the first DC switch 220, the second DC switch 230, or the grid-connected switch 250 is disconnected, the energy storage battery cannot interact with the grid, that is, the grid-connected power converter 200 is off-grid. Thus, it can be seen that the grid-connected power converter 200 can be disconnected by controlling the first DC switch 220, the second DC switch 230, or the grid-connected switch 250 to disconnect.

[0031] It should be noted that when the grid-connected power converter 200 is off-grid, it is assumed that the first DC switch 220 is disconnected, while the second DC switch 230 and the grid-connected switch 250 are closed. At this time, the voltage or current fluctuation of the power grid will affect the inverter circuit 240, and the energy storage battery and the inverter circuit 240 will affect each other. Similarly, if the grid-connected switch 250 is disconnected, while the first DC switch 220 and the second DC switch 230 are closed, the energy storage battery and the inverter circuit 240 will affect each other, thereby reducing the stability and safety of the inverter circuit 240. Therefore, when the grid-connected power converter 200 provided in the embodiment of the present application is off-grid, the first DC switch 220, the second DC switch 230 and the grid-connected switch 250 are all disconnected, which can ensure the stability of the grid-connected power converter when it is off-grid.

[0032] In general, the grid-connected power converter 200 provided in the embodiment of the present application is provided with a first DC switch 220 and a second DC switch 230 on the DC bus, and a grid-connected switch 250 is provided between the AC output terminal i3 of the inverter circuit and the grid. Grid connection can be achieved by controlling the first DC switch 220, the second DC switch 230, and the grid-connected switch 250 to be closed. Alternatively, the grid-connected power converter 200 can be disconnected by controlling the first DC switch 220, the second DC switch 230, and the grid-connected switch 250 to be disconnected.

[0033] In some feasible implementations, the grid-connected power converter 200 can control the on / off of the first DC switch 220, the second DC switch 230, and the grid-connected switch 250 through a controller 260. The controller 260 and the grid-connected power converter 200 can be independent devices, and the controller 260 can be disposed inside or outside the grid-connected power converter 200. Alternatively, in other cases, the controller 260 can also be a related control device within the grid-connected power converter 200.

[0034] In some feasible embodiments, when the grid-connected power converter 200 switches from grid-connected to grid-off, the controller 260 can first control the grid-connected switch 250 to be disconnected, and then control the first DC switch 220 and the second DC switch 230 to be disconnected. The controller 260 first controls the grid-connected switch 250 to be disconnected, thereby disconnecting the inverter circuit 240 from the grid. This can reduce the impact of grid voltage fluctuations on the inverter circuit 240. Furthermore, when the grid-connected switch 250 is disconnected, the controller 260 then controls the first DC switch 220 and the second DC switch 230 to be disconnected. This can also reduce the impact of the grid voltage on the first DC switch 220 and the second DC switch 230, thereby achieving stable off-grid operation.

[0035] It should be noted that in the grid-connected power converter 200 provided in the embodiment of the present application, since the grid-connected switch 250 is disposed between the power grid and the inverter circuit 240, the voltage across the grid-connected switch 250 varies significantly. In some application scenarios, the two ends of the grid-connected switch 250 may become stuck under the action of high voltage, making it impossible for the controller 260 to control the grid-connected switch 250 to be safely disconnected, thereby causing the grid-connected power converter 200 to experience an off-grid fault.

[0036] In some feasible embodiments, in order to avoid the grid-connected switch from sticking, which causes the grid-connected power converter to be unable to safely disconnect from the grid, a conventional grid-connected power converter is connected to the grid via two grid-connected switches connected in series. When one of the grid-connected switches becomes stuck or otherwise fails, the grid-connected power converter can be safely disconnected from the grid by controlling the other grid-connected switch to disconnect. However, the above conventional grid-connected power converter needs to be provided with two grid-connected switches, which increases production costs. In particular, when the grid to which the grid-connected power converter is connected is a three-phase AC grid, two grid-connected switches connected in series need to be provided when the grid-connected power converter is connected to each phase of the grid, which significantly increases production costs.

[0037] Compared to conventional grid-connected power converters, the grid-connected power converter 200 provided in the embodiment of the present application is connected to the grid via only one grid-connected switch 250, which can effectively reduce production costs. Furthermore, when the grid-connected switch 250 becomes stuck, the grid-connected power converter 200 can control the first DC switch 220 and the second DC switch 230 to disconnect, thereby ensuring that the grid-connected power converter 200 can be safely disconnected from the grid.

[0038] In some feasible embodiments, the grid-connected power converter 200 can determine whether the grid-connected switch 250 is stuck by detecting the voltage across the grid-connected switch 250. Specifically, when the grid-connected switch 250 is disconnected, the controller 260 can obtain the voltage across the grid-connected switch 250 and determine whether the voltage across the grid-connected switch 250 is greater than a voltage difference threshold to determine whether the grid-connected switch 250 is stuck. The voltage difference threshold can be understood as the minimum value of the voltage across the grid-connected switch 250 when the grid-connected switch 250 is disconnected when the grid-connected switch 250 is not stuck. When the grid-connected switch 250 is closed, the controller 260 can send a control signal to the grid-connected switch 250 to control the grid-connected switch 250 to disconnect. The controller 260 obtains the voltage across the grid-connected switch 250 after it is disconnected to determine whether the grid-connected switch 250 is safely disconnected without sticking.

[0039] For example, it is assumed that the voltage difference threshold of the grid-connected switch 250 is 20 volts, that is, when the grid-connected switch 250 is not stuck, the voltage across the two ends of the grid-connected switch 250 is greater than 20 volts when the grid-connected switch 250 is disconnected. When the controller 260 obtains that the voltage across the two ends of the grid-connected switch 250 is 25 volts, it indicates that the grid-connected switch 250 is not stuck. When the controller 260 obtains that the voltage across the two ends of the grid-connected switch 250 is 10 volts, it indicates that the grid-connected switch 250 has stuck and the grid-connected switch 250 cannot be safely disconnected. It can be seen from the above that in the case where the grid-connected switch 250 is stuck, when the grid-connected power converter 200 needs to be disconnected from the grid, the controller 260 can control the first DC switch 220 and the second DC switch 230 to be disconnected to ensure that the grid-connected power converter 200 is safely disconnected from the grid.

[0040] In some feasible embodiments, it should be noted that if the voltage difference between the two ends of the first DC switch 220 is large before it is closed, a large current will flow through the first DC switch 220 at the moment the controller 260 controls the first DC switch 220 to close, causing corrosion in the first DC switch 220. Similarly, if the voltage difference between the two ends of the second DC switch 230 or the grid-connecting switch 250 is large before it is closed, corrosion will also occur at the moment of closing, thereby affecting the safety of the grid-connected power converter.

[0041] To this end, when the grid-connected power converter 200 provided in the embodiment of the present application is connected to the grid, the first DC switch 220, the second DC switch 230 and the grid-connected switch 250 can be controlled to close when the voltage difference between the two ends is small, thereby reducing the ablation of each switch and ensuring that the grid-connected power converter 200 is safely connected to the grid.

[0042] In some feasible embodiments, when the grid-connected power converter 200 switches from off-grid to grid-connected, the controller 260 in the grid-connected power converter 200 may first control the first DC switch 220 to close. At this time, as shown in FIG2 , since the second DC switch 230 is disconnected, the energy storage battery fails to form a current loop through the first DC switch 220 and the second DC switch 230, and the voltage difference across the first DC switch 220 is 0 volts (or close to 0 volts). Therefore, in the embodiment of the present application, the controller 260 controls the first DC switch 220 to close when the voltage difference across the first DC switch 220 is small, thereby reducing the ablation of the first DC switch 220.

[0043] After controlling the first DC switch 220 to close with a voltage close to zero across its terminals, the controller 260 can adjust the voltage across the second DC switch via the soft-start circuit 270 and control the second DC switch 230 to close when the voltage across the second DC switch 230 is less than or equal to a first voltage threshold. The first voltage threshold can be understood as the maximum voltage across the second DC switch 230 at the moment of closing when ablation does not occur. In other words, when the voltage across the second DC switch 230 at the moment of closing is less than or equal to the first voltage threshold, ablation will not occur when the second DC switch 230 is closed. Conversely, when the voltage across the second DC switch 230 at the moment of closing is greater than the first voltage threshold, ablation will occur when the second DC switch 230 is closed.

[0044] After controlling the first DC switch 220 and the second DC switch 230 to be closed, the controller 260 may further control the grid-connected switch 250 to be closed, so that the grid-connected power converter 200 is connected to the grid.

[0045] Thus, when the grid-connected power converter 200 provided in the embodiment of the present application is connected to the grid, the controller 260 can first control the first DC switch 220 to be closed, and then the voltage across the second DC switch 230 can be adjusted through the soft-start circuit 270, and the second DC switch 230 can be controlled to be closed when the voltage across the two ends is less than or equal to the first voltage threshold. This can reduce the ablation of the first DC switch 220 and the second DC switch 230, thereby ensuring the safety of the grid-connected power converter 200. The specific implementation principle will not be described in detail here.

[0046] In an embodiment of the present application, when the grid-connected power converter switches from off-grid to grid-connected, the controller first controls the first DC switch to close, so that the first DC switch is closed when the voltage across the two ends is close to 0, thereby reducing the ablation of the first DC switch. Furthermore, the voltage across the second DC switch is adjusted by a soft-start circuit, and the second DC switch is controlled to close when the voltage across the two ends is less than or equal to the first voltage threshold, thereby reducing the ablation of the second DC switch. After the first DC switch and the second DC switch are closed, the grid-connected power converter further controls the grid-connected switch to close by the controller, thereby achieving safe grid connection of the grid-connected power converter. In addition, the grid-connected power converter can be switched to off-grid by controlling the first DC switch, the second DC switch and the grid-connected switch to disconnect. When the grid-connected switch is stuck, the grid-connected power converter can ensure safe off-grid operation by controlling the first DC switch and the second DC switch to disconnect, and only one grid-connected switch is provided in the grid-connected power converter to connect to the grid, which can effectively reduce production costs.

[0047] In some feasible embodiments, please refer to Figure 3, which is another structural schematic diagram of a grid-connected power converter provided in an embodiment of the present application. The grid-connected power converter 300 shown in Figure 3 includes a DC bus, a first DC switch 320, a second DC switch 330, an inverter circuit 340, a grid-connected switch 350, a controller 360, a soft-start circuit 370, and a DC converter 380. The DC bus may specifically include a positive DC bus 311 and a negative DC bus 312. The first DC switch 320 is connected in series to the positive DC bus 311, and the second DC switch 330 is connected in series to the negative DC bus 312. The soft-start circuit 370 is connected in parallel to the second DC switch 330. The AC output terminal i3 of the inverter circuit 340 is connected to one end of the grid-connected switch 350, and the other end of the grid-connected switch 350 is connected to the power grid.

[0048] It is understood that the DC converter 380 can convert the DC power output by the energy storage battery to output DC power with flexible and adjustable voltage and current to the inverter circuit 340. It should be noted that the specific implementation of the grid-connected power converter 300 can refer to the specific implementation of the grid-connected power converter 200, and the present embodiment will not be described in detail here.

[0049] In some feasible embodiments, please refer to Figure 4, which is another structural schematic diagram of a grid-connected power converter provided in an embodiment of the present application. The grid-connected power converter 400 shown in Figure 4 includes a DC bus, a first DC switch 420, a second DC switch 430, an inverter circuit 440, a grid-connected switch 450, a controller 460, a soft-start circuit 470 and a DC converter 480. The above-mentioned DC bus can specifically include a positive DC bus 411 and a negative DC bus 412. Among them, the first DC switch 420 is connected in series to the positive DC bus 411, and the second DC switch 430 is connected in series to the negative DC bus 412. The soft-start circuit 470 is connected in parallel with the second DC switch 430. The AC output terminal i3 of the inverter circuit 440 is connected to one end of the grid-connected switch 450, and the other end of the grid-connected switch 450 is connected to the power grid.

[0050] It is understood that the DC converter 480 can convert the DC power output by the energy storage battery to output DC power with flexible and adjustable voltage and current to the inverter circuit 440. It should be noted that the specific implementation of the grid-connected power converter 400 can refer to the specific implementation of the grid-connected power converter 200, and the present embodiment will not be described in detail here.

[0051] In some feasible implementations, the first DC switch and the second DC switch in FIG. 3 or FIG. 4 may also be disposed inside a DC converter, which is not limited in the embodiment of the present application.

[0052] In some feasible implementations, it should be noted that the grid-connected power converter can also control the second DC switch to be closed by the controller when connected to the grid, and then, when the second DC switch is closed, adjust the voltage across the first DC switch through the soft-start circuit, and control the first DC switch to be closed when the voltage across the first DC switch is less than or equal to the first voltage threshold. In other words, the closing order of the first DC switch and the second DC switch in the grid-connected power converter can be adjusted according to the actual application scenario. For ease of understanding, the embodiments of the present application are described below using the example of the controller first controlling the first DC switch to be closed and then controlling the second DC switch to be closed.

[0053] To facilitate understanding of the specific implementation process of the grid-connected power converter adjusting the voltage across the second DC switch through the soft-start circuit after the controller controls the first DC switch to close, the embodiment of the present application is described in detail in the following with reference to FIG5 .

[0054] In some feasible implementations, please refer to FIG. 5 , which is another schematic diagram of the structure of a grid-connected power converter provided in an embodiment of the present application. The grid-connected power converter 500 shown in FIG. 5 includes a DC bus, a first DC switch 520, a second DC switch 530, an inverter circuit 540, a grid-connected switch 550, a controller 560, a third DC switch 570, a current limiting unit 580, a bus capacitor 590, and a capacitor module 5100. The DC bus may specifically include a positive DC bus 511 and a negative DC bus 512. The first DC switch 520 is connected in series to the positive DC bus 511, and the second DC switch 530 is connected in series to the negative DC bus 512. The third DC switch 570 is connected in series with the current limiting unit 580 and then connected in parallel to both ends of the second DC switch 530. The third DC switch 570 can be understood as being provided in the above-mentioned soft-start circuit. The bus capacitor 590 is connected in parallel between the DC input terminal i1 and the DC input terminal i2 of the inverter circuit 240. The capacitor module 5100 is connected in parallel between two electrodes of the energy storage battery. The AC output terminal i3 of the inverter circuit 540 is connected to one end of the grid-connected switch 550, and the other end of the grid-connected switch 550 is connected to the power grid.

[0055] When the grid-connected power converter 500 switches from an off-grid state to a grid-connected state, as can be seen from the above content, the grid-connected power converter 500 can first control the first DC switch 520 to close through the controller 560, so that the first DC switch 520 is closed without causing ablation. Furthermore, in order to allow the second DC switch 530 to be closed without causing ablation, after the first DC switch 520 is closed, the controller 560 can first control the third DC switch 570 to close to adjust the voltage across the second DC switch 530. It can be understood that after the first DC switch 520 and the third DC switch 570 are closed, the two electrodes of the energy storage battery can form a current loop, so that the energy storage battery can charge the bus capacitor 590. At the same time, during the charging process of the bus capacitor 590, the voltage at one end of the second DC switch 530 connected to the bus capacitor 590 gradually increases, thereby reducing the voltage across the second DC switch 530, so that when the voltage across the second DC switch 530 is less than or equal to the first voltage threshold, the second DC switch 530 is controlled to close without causing ablation.

[0056] For example, assuming the first voltage threshold is 5V, after the first DC switch 520 and the third DC switch 570 are closed, the energy storage battery charges the bus capacitor 590. When the controller 560 obtains a voltage of 10V across the second DC switch 530, as described above, ablation will occur when the second DC switch 530 is closed when the voltage across the second DC switch 530 is greater than the first voltage threshold. When the controller 560 obtains a voltage of 5V across the second DC switch 530, i.e., less than or equal to the first voltage threshold of 5V, the controller 560 can control the second DC switch 530 to close without ablation.

[0057] It should also be noted that, because the third DC switch 570 is connected to the current-limiting unit 580, when the third DC switch 570 is closed to form a current loop, the current passing through the third DC switch 570 is very small due to the action of the current-limiting unit 580. Therefore, it does not cause ablation of the third DC switch 570, thereby ensuring the safe operation of the third DC switch. In some application scenarios, the current-limiting unit 580 may be a current-limiting resistor or a diode, which is not limited in this embodiment of the present application.

[0058] As can be seen from the above, the bus capacitor 590 is connected in parallel between the DC input terminal i1 and the DC input terminal i2 of the inverter circuit 240, and is connected to one end of the second DC switch 530, and can adjust the voltage across the second DC switch 530 during charging. Specifically, the bus capacitor 590 may include a capacitor C1 and a capacitor C2 connected in series. It is understood that the grid-connected power converter 500 provided in the embodiment of the present application can also adopt other methods to adjust the voltage across the second DC switch 530 according to the needs of the application scenario, and is not limited to the specific implementation of the bus capacitor 590. The embodiment of the present application does not illustrate them one by one here.

[0059] In some feasible embodiments, after the grid-connected power converter 500 controls the first DC switch 520 and the second DC switch 530 to be closed by the controller 560, the controller 560 may further control the grid-connected switch 550 to be closed when the voltage across the two ends is less than or equal to the second voltage threshold, so as to reduce the ablation when the grid-connected switch 550 is closed, thereby further improving the grid-connected safety of the grid-connected power converter 500. Wherein, the second voltage threshold can be understood as the maximum value of the voltage across the two ends of the grid-connected switch 550 corresponding to the guarantee that the grid-connected switch 550 does not ablate at the moment of closing. That is, when the voltage across the two ends of the grid-connected switch 550 at the moment of closing is less than or equal to the second voltage threshold, ablation will not occur when the grid-connected switch 550 is closed. On the contrary, when the voltage across the two ends of the grid-connected switch 550 at the moment of closing is greater than the second voltage threshold, ablation will occur when the grid-connected switch 550 is closed.

[0060] Specifically, after the first DC switch 520 and the second DC switch 530 are closed, the inverter circuit 540 can invert the DC power provided by the energy storage battery into AC power and output it through the AC output terminal i3. Among them, the controller 560 can adjust the voltage, frequency and other parameters of the AC power output from the AC output terminal i3 by controlling the inverter circuit 540 to adjust the voltage across the grid-connected switch 550. Exemplarily, the controller 560 can adjust the pulse width modulation signal of the inverter circuit 540 so that the inverter circuit 540 inverts the AC power with different parameters according to different pulse width modulation signals, thereby flexibly adjusting the voltage across the grid-connected switch 550. In some application scenarios, the controller 560 can also adopt other methods to adjust the voltage across the grid-connected switch 550, which are not illustrated one by one in the embodiments of this application.

[0061] It can be understood that while the controller 560 adjusts the voltage across the grid-connected switch 550 through the inverter circuit 540, it can also obtain the voltage across the grid-connected switch 550, so as to control the grid-connected switch 550 to close when the voltage across the grid-connected switch 550 is less than or equal to the second voltage threshold, so as to reduce the ablation of the grid-connected switch 550 and further improve the grid-connected safety of the grid-connected power converter 500.

[0062] It should be noted that in the embodiment of the present application, the controller 560 can first detect whether the grid-connected switch 550 is stuck before controlling the grid-connected switch 550 to close. For specific implementation, please refer to the specific implementation method of the grid-connected switch 250 in Figure 2 above. The embodiment of the present application will not be repeated here.

[0063] In some feasible embodiments, as the switch is used for a long time, oxygen and moisture in the environment will gradually form an oxide layer on the metal contact surface of the switch, thereby causing poor contact of the switch. At the same time, the presence of the oxide layer will also increase the equivalent resistance of the switch, resulting in significant heat generation when current passes through the switch. To this end, the grid-connected power converter 500 provided in the embodiment of the present application can perform a deoxidation operation on the first DC switch 520, the second DC switch 530, and the grid-connected switch 550 to remove the oxide layer on the metal contact surfaces of the first DC switch 520, the second DC switch 530, and the grid-connected switch 550, thereby extending the service life of the switch.

[0064] It should be noted that when the first DC switch 520, the second DC switch 530, or the grid-connected switch 550 is closed, the voltage across the terminals is high, which can remove the oxide layer on the metal contact surface. Therefore, in the embodiment of the present application, the grid-connected power converter 500 can control the first DC switch 520, the second DC switch 530, or the grid-connected switch 550 to be closed when the voltage across the terminals is high, thereby performing deoxidation.

[0065] In order to enable the controller 560 to deoxidize the above-mentioned switches (the first DC switch 520, the second DC switch 530 and the grid-connected switch 550) in a timely manner, the controller 560 can obtain the operating temperature of the switch when each switch is closed, and when the operating temperature of the switch is high, it is determined that the oxide layer of the switch needs to be removed. Among them, the judgment standard of the operating temperature of each switch can be adjusted according to the actual application scenario, and the embodiment of the present application is not limited to this. Further, when it is determined that the operating temperature of the switch is high, the controller 560 can control each switch to be disconnected, that is, after the grid-connected power converter 500 is off-grid, deoxidize the switch with the higher operating temperature, and after the deoxidation is completed, control the switch to be disconnected so that the grid-connected power converter 500 continues to remain off-grid before it is needed to be connected to the grid.

[0066] In some feasible embodiments, specifically, when the grid-connected power converter 500 is off-grid, the controller 560 can control the switches to close when the voltage across them is greater than or equal to a third voltage threshold to perform deoxidation. The third voltage threshold can be understood as the minimum value of the voltage across each of the switches when they are closed and the oxide layer is removed. It should be noted that the values ​​of the third voltage thresholds corresponding to different switches may be different, and the present embodiment does not provide examples for each of them.

[0067] It should be noted that when the first DC switch 520, the second DC switch 530, or the grid-connected switch 550 is performing deoxidation, the corresponding third voltage threshold is greater than the first voltage threshold corresponding to the grid connection. For example, the first voltage threshold of the first DC switch 520 or the second DC switch 530 during grid connection is 5 volts, and the third voltage threshold of the first DC switch 520 or the second DC switch 530 during deoxidation is 10 volts.

[0068] In some feasible embodiments, the grid-connected power converter 500 provided in the embodiment of the present application can control the first DC switch 520 to close when the voltage across the first DC switch 520 is greater than or equal to the third voltage threshold by adjusting and obtaining the voltage across the first DC switch 520. Specifically, when the grid-connected power converter 500 is off-grid, the controller 560 can first control the first DC switch 520 to close, and then control the third DC switch 570 to close, to adjust the voltage across the second DC switch 530. The energy storage battery can charge the bus capacitor 590, so that the voltage at the end of the second DC switch 530 connected to the bus capacitor 590 gradually increases, thereby reducing the voltage across the second DC switch 530. Furthermore, when the voltage across the second DC switch 530 is greater than or equal to the third voltage threshold, the controller 560 can control the first DC switch 520 to open, and then control the second DC switch 530 to close. At this time, if the voltage across the first DC switch 520 is greater than or equal to the third voltage threshold, the controller 560 can control the first DC switch 520 to close and remove the oxide layer at the same time.

[0069] After controlling the first DC switch 520 to close and remove the oxide layer, the controller 560 may control the first DC switch 520 to open again, so that the grid-connected power converter 500 remains off-grid.

[0070] In some feasible embodiments, the grid-connected power converter 500 provided in the embodiment of the present application can control the second DC switch 530 to close when the voltage at both ends is greater than or equal to the third voltage threshold by adjusting and obtaining the voltage at both ends of the second DC switch 530. Specifically, when the grid-connected power converter 500 is off-grid, the controller 560 can first control the first DC switch 520 to close, and then control the third DC switch 570 to close. To adjust the voltage at both ends of the second DC switch 530. Among them, the energy storage battery can charge the bus capacitor 590, so that the voltage at one end of the second DC switch 530 connected to the bus capacitor 590 gradually increases, and then the voltage at both ends of the second DC switch 530 can be reduced, so that when the voltage at both ends of the second DC switch 530 is greater than or equal to the third voltage threshold, the second DC switch 530 can be controlled to remove the oxide layer while closing.

[0071] After controlling the second DC switch 530 to close and remove the oxide layer, the controller 560 may control the second DC switch 530 to open again, so that the grid-connected power converter 500 remains off-grid.

[0072] In some feasible implementations, the grid-connected power converter 500 provided in the embodiment of the present application can adjust and obtain the voltage across the grid-connected switch 550 to control the grid-connected switch 550 to close when the voltage across the two ends is greater than or equal to the third voltage threshold. Specifically, when the grid-connected power converter 500 is off-grid, the controller 560 can first control the first DC switch 520 to close and the second DC switch 530 to close. At this time, the inverter circuit 540 can invert the DC power provided by the energy storage battery into AC power and output it through the AC output terminal i3. The controller 560 adjusts the voltage, frequency and other parameters of the AC power outputted from the AC output terminal i3 by controlling the inverter circuit 540 to adjust the voltage across the grid-connected switch 550, so that when the voltage across the grid-connected switch 550 is obtained to be greater than or equal to the third voltage threshold, the grid-connected switch 550 can be controlled to remove the oxide layer while closing.

[0073] After controlling the grid-connected switch 550 to close and removing the oxide layer, the controller 560 may control the grid-connected switch 550 to open again, so that the grid-connected power converter 500 remains off-grid.

[0074] In some feasible embodiments, it can be seen from the above content that when the grid-connected power converter is connected to the grid, the voltage across each switch is adjusted by the electric energy provided by the energy storage battery to reduce ablation when each switch is closed. In some application scenarios, the charge of the energy storage battery may not be sufficient to adjust the voltage across each switch, which in turn affects the safe grid connection of the grid-connected power converter. To this end, in an embodiment of the present application, the grid-connected power converter can obtain the charge of the energy storage battery, and when the charge of the energy storage battery is greater than the charge threshold, the grid connection of the grid-connected power converter and the deoxidation of each switch are achieved according to the above content. When the charge of the energy storage battery is less than or equal to the charge threshold, the grid connection of the grid-connected power converter and the deoxidation of each switch are achieved according to the following content. Among them, the charge threshold of the energy storage battery can be understood as the minimum value of the charge of the energy storage battery at which the electric energy stored in the energy storage battery can be used to adjust the voltage across each switch to achieve the grid connection of the grid-connected power converter. For example, in some application scenarios, the charge threshold can be 0.1, that is, when the charge of the energy storage battery is less than or equal to 1, the grid-connected power converter cannot use the power of the energy storage battery to regulate the voltage across each switch, but must use the power of the grid to regulate the voltage across each switch.

[0075] In some feasible embodiments, please refer to Figure 5 again. The grid-connected power converter 500 shown in Figure 5 can obtain the charge of the energy storage battery through the controller 560 when it is off-grid. When the charge of the energy storage battery is less than or equal to the charge threshold, if the grid-connected power converter 500 needs to be connected to the grid, the controller 560 can control the grid-connected switch 550 to close when the voltage difference across the grid-connected switch 550 is less than or equal to the second voltage threshold, and then control the first DC switch 520 and the second DC switch 530 to close, so as to achieve safe grid connection of the grid-connected power converter 500. To facilitate understanding of the specific implementation process of the grid-connected power converter 500 controlling the grid-connected switch 550 to close when the voltage across the grid switch 550 is less than or equal to the second voltage threshold after obtaining the charge of the energy storage battery through the controller 560. The embodiment of the present application will be described in detail in conjunction with Figure 5 below.

[0076] In some feasible embodiments, when the grid-connected power converter 500 switches from off-grid to grid-connected, and the controller 560 obtains that the charge of the energy storage battery is less than or equal to a charge threshold, the controller 560 can obtain the AC power from the grid to generate DC power, and transmit the DC power to the bus capacitor 590 for charging. Furthermore, after the bus capacitor 590 is charged, the controller 560 can control the inverter circuit 540 to invert the power stored in the bus capacitor 590 into AC power, thereby adjusting the voltage across the grid-connected switch 550. This allows the controller 560 to control the grid-connected switch 550 to close when the voltage across the bus capacitor 590 is less than or equal to a second voltage threshold, thereby reducing the erosion of the grid-connected switch 550. Thus, the controller 560 charges the bus capacitor 590 by obtaining power from the grid, allowing the inverter circuit 540 to adjust the voltage across the grid-connected switch 550 based on the DC power provided by the bus capacitor 590, thereby ensuring the safety of the grid-connected power converter 500 when the charge of the energy storage battery is insufficient.

[0077] In some feasible embodiments, after the grid-connected power converter 500 controls the grid-connected switch 550 to close when the voltage at both ends is less than or equal to the second voltage threshold, the controller 560 also controls the first DC switch 520 and the second DC switch 530 to close when the voltage at both ends is less than or equal to the first voltage threshold, so as to reduce the ablation when the first DC switch 520 and the second DC switch 530 are closed, thereby further improving the grid-connected safety of the grid-connected power converter 500.

[0078] Specifically, after the grid-connected switch 550 is closed, the inverter circuit 540 can rectify the AC power provided by the power grid to obtain DC power, and output it to the bus capacitor 590 through the DC input terminal i1 and the DC input terminal i2 for charging. Since the first DC switch 520 and the second DC switch 530 are respectively connected to the bus capacitor 590, the bus capacitor 590 can adjust the voltage across the first DC switch 520 and the second DC switch 530 after charging. Furthermore, the controller 560 can obtain the voltage across the first DC switch 520 and the second DC switch 530 and control the first DC switch 520 and the second DC switch 530 to close when the voltage across the first DC switch 520 and the second DC switch 530 is less than or equal to a first voltage threshold, thereby reducing ablation when the first DC switch 520 and the second DC switch 530 are closed. It should be noted that the controller 560 can control the first DC switch 520 and the second DC switch 530 to close simultaneously, or can control one DC switch to close first and then the other DC switch to close, and this embodiment of the application is not limited to this.

[0079] It should be noted that the controller 560 can obtain the AC power of the power grid through an auxiliary power supply, and obtain DC power through the rectification of the auxiliary power supply. In some application scenarios, the auxiliary power supply can be set inside or outside the controller 560, the input end of the auxiliary power supply is connected to the power grid, the output end is connected to the bus capacitor 590, and the control end is connected to the controller 560. Among them, after the controller 560 obtains that the charge of the energy storage battery is less than or equal to the charge threshold, it can send a control instruction to the auxiliary power supply. After receiving the control instruction, the auxiliary power supply can rectify the AC power of the power grid into DC power and output it to the bus capacitor 590 for charging. In other application scenarios, the controller 560 can also adopt other methods to charge the bus capacitor 590, and the embodiments of this application will not be illustrated one by one here.

[0080] It should be noted that in the embodiment of the present application, the controller 560 can first detect whether the grid-connected switch 550 is stuck before controlling the grid-connected switch 550 to close. For specific implementation, please refer to the specific implementation method of the grid-connected switch 250 in Figure 2 above. The embodiment of the present application will not be repeated here.

[0081] In some feasible embodiments, it can be seen from the above content that in order to deoxidize the first DC switch 520, the second DC switch 530 and the grid-connected switch 550 in a timely manner, the controller 560 can control each switch to be disconnected when it obtains that the operating temperature of the switch is high, that is, after the grid-connected power converter 500 is off the grid, deoxidize the switch, and after the deoxidation is completed, control the switch to be disconnected, so that the grid-connected power converter 500 continues to remain off the grid before it is needed to be connected to the grid.

[0082] It is understandable that when the grid-connected power converter 500 is off-grid, the controller 560 may control the above-mentioned switches to be closed when the voltage across both ends is greater than or equal to the third voltage threshold, so as to deoxidize the switches.

[0083] In some feasible implementations, the grid-connected power converter 500 provided in the embodiment of the present application can adjust and obtain the voltage across the grid-connected switch 550 to control the grid-connected switch 550 to close when the voltage across the two ends is greater than or equal to the third voltage threshold. Specifically, when the charge of the energy storage battery is less than or equal to the charge threshold, the grid-connected power converter 500 can provide the power of the grid to the bus capacitor 590 for charging through the controller 560 when off-grid. Further, the controller 560 can control the inverter circuit 540 to adjust the voltage across the grid switch 550 based on the power stored in the bus capacitor 590. Among them, the controller 560 can adjust the voltage, frequency and other parameters of the AC output terminal i3 by controlling the inverter circuit 540 to adjust the voltage across the grid switch 550, so that when the voltage across the grid switch 550 is greater than or equal to the third voltage threshold, the grid switch 550 can be controlled to remove the oxide layer while closing.

[0084] After controlling the grid-connected switch 550 to close and removing the oxide layer, the controller 560 may control the grid-connected switch 550 to open again, so that the grid-connected power converter 500 remains off-grid.

[0085] In some feasible embodiments, the grid-connected power converter 500 provided in the embodiments of the present application can control the first DC switch 520 to close when the voltage across the first DC switch 520 is greater than or equal to the third voltage threshold by adjusting and obtaining the voltage across the first DC switch 520. Specifically, when the charge of the energy storage battery is less than or equal to the charge threshold, the grid-connected power converter 500 can control the grid-connected switch 550 to close through the controller 560 when off-grid. The controller 560 can then control the inverter circuit 240 to rectify the AC power provided by the grid to obtain DC power, and transmit the DC power to charge the bus capacitor 590. Furthermore, the controller 560 first controls the first DC switch 520 to close, and then controls the third DC switch 570 to close. At this time, the bus capacitor 590 can charge the capacitor module 5100. At the same time, during the charging process of the capacitor module 5100, the voltage at the end of the second DC switch 530 connected to the capacitor module 5100 gradually increases, thereby reducing the voltage across the second DC switch 530. It is understood that when the voltage across the second DC switch 530 is greater than or equal to the third voltage threshold, the controller 560 may control the first DC switch 520 to be open, and then control the second DC switch 530 to be closed. At this time, if the voltage across the first DC switch 520 is greater than or equal to the third voltage threshold, the controller 560 may control the first DC switch 520 to be closed and remove the oxide layer simultaneously.

[0086] In some feasible embodiments, the grid-connected power converter 500 provided in the embodiment of the present application can adjust and obtain the voltage across the second DC switch 530 to control the second DC switch 530 to close when the voltage across the two ends is greater than or equal to the third voltage threshold. Specifically, when the charge of the energy storage battery is less than or equal to the charge threshold, the grid-connected power converter 500 can, when off-grid, first control the grid-connected switch 550 to close through the controller 560 to charge the bus capacitor 590, then control the first DC switch 520 to close, and then control the third DC switch 570 to close. As can be seen from the above content, at this time, the bus capacitor 590 can charge the capacitor module 5100. At the same time, during the charging process of the capacitor module 5100, the voltage at one end of the second DC switch 530 connected to the capacitor module 5100 gradually increases, thereby reducing the voltage across the second DC switch 530, so that when the voltage across the second DC switch 530 is greater than or equal to the third voltage threshold, the second DC switch 530 can be controlled to remove the oxide layer while closing.

[0087] In some feasible embodiments, when the charge of the energy storage battery is less than or equal to the charge threshold, the grid-connected power converter 500 provided in the embodiment of the present application can not only deoxidize the first DC switch 520 and the second DC switch 530 after the grid-connected switch 550 is closed by the controller 560, but can also deoxidize the first DC switch 520 and the second DC switch 530 when the grid-connected switch 550 is not closed. Specifically, after providing power from the grid to the bus capacitor 590 for charging, the controller 560 can control the first DC switch 520 and the second DC switch 530 to remove the oxide layer while closing, according to the closing sequence of the first DC switch 520, the second DC switch 530, and the third DC switch 570 as described above. The embodiments of the present application are not described in detail here.

[0088] After controlling the first DC switch 520 or the second DC switch 530 to close and removing the oxide layer, the controller 560 may control the first DC switch 520 or the second DC switch 530 to open again, so that the grid-connected power converter 500 remains off-grid.

[0089] In an embodiment of the present application, when the charge of the energy storage battery is insufficient, the grid-connected power converter controls the on and off of the first DC switch, the second DC switch, and the grid-connected switch through a controller, so that the grid-connected power converter can be off-grid or grid-connected. Among them, when the grid-connected power converter switches from off-grid to grid-connected, the controller first controls the grid-connected switch to close when the voltage at both ends is less than or equal to the second voltage threshold, thereby reducing the burning of the grid-connected switch. Furthermore, after the grid-connected switch is closed, the controller controls the first DC switch and the second DC switch to close when the voltage at both ends is less than or equal to the first voltage threshold, thereby reducing the burning of the first DC switch and the second DC switch, so as to achieve safe grid connection of the grid-connected power converter. At the same time, when the grid-connected switch is stuck, the grid-connected power converter controls the first DC switch and the second DC switch to be disconnected through the controller, thereby ensuring safe off-grid operation. In addition, in the embodiment of the present application, only one grid-connected switch is provided in the grid-connected power converter to connect to the power grid, which can effectively reduce production costs.

[0090] In some feasible embodiments, when the grid connected to the grid-connected power converter is a three-phase AC grid, the specific implementation of the grid-connected power converter can be shown in FIG6 . Specifically, referring to FIG6 , the grid-connected power converter 600 shown in FIG6 includes a DC bus, a first DC switch 620, a second DC switch 630, an inverter circuit 640, a grid-connected switch 650, a controller 660, a third DC switch 670, a current limiting unit 680, a bus capacitor 690, a filter module 6100, and a capacitor module 6110. The DC bus can specifically include a positive DC bus 611 and a negative DC bus 612. The first DC switch 620 is connected in series to the positive DC bus 611, and the second DC switch 630 is connected in series to the negative DC bus 612. The third DC switch 670 and the current limiting unit 680 are connected in series and then in parallel across the second DC switch 630. The bus capacitor 690 is connected in parallel between the DC input terminals i1 and i2 of the inverter circuit 640. The busbar capacitor 690 includes capacitors C1 and C2 connected in series. The capacitor module 6110 is connected in parallel between the two electrodes of the energy storage battery. The AC output terminal i3 of the inverter circuit 640 is connected to one end of the grid-connected switch 650, and the other end of the grid-connected switch 650 is connected to the power grid.

[0091] Specifically, as shown in FIG6 , when the grid-connected power converter is connected to a three-phase AC grid, the grid-connected switch 650 includes a first grid-connected switch K11, a second grid-connected switch K12, and a third grid-connected switch K13. The filtering module includes an inductor L11, an inductor L12, an inductor L13, a capacitor C11, a capacitor C12, and a capacitor C13. Inductor L11 has one end connected to the AC output terminal i31 of the inverter circuit 640 and the other end connected to the grid inductor L21 via the first grid-connected switch K11. Inductor L12 has one end connected to the AC output terminal i32 of the inverter circuit 640 and the other end connected to the grid inductor L22 via the second grid-connected switch K12. Inductor L13 has one end connected to the AC output terminal i33 of the inverter circuit 640 and the other end connected to the grid inductor L23 via the third grid-connected switch K13. One end of capacitor C11 in the filter module 6100 is connected to inductor L11, one end of capacitor C12 in the filter module 6100 is connected to inductor L12, and one end of capacitor C13 in the filter module 6100 is connected to inductor L13. The other ends of capacitors C11, C12, and C13 are connected. In addition, the power grid shown in Figure 6 is also provided with capacitors C3, C4, and C5. The specific configuration method can be found in Figure 6 and will not be described in detail in this embodiment of the present application.

[0092] It should be noted that the above-mentioned filtering module 6100 is arranged between the inverter circuit 640 and the grid-connected switch 650, and can filter the AC power output by the inverter circuit 640 to ensure that the grid-connected power converter 600 supplies stable power to the grid when connected to the grid.

Claims

1. A grid-connected power converter, characterized in that: The grid-connected power converter includes a DC bus, a first DC switch, a second DC switch, a slow-start circuit, an inverter circuit, a grid-connected switch, and a controller, wherein the inverter circuit is used to convert DC power into AC power, the DC input end of the inverter circuit is used to be connected to a photovoltaic module or an energy storage battery through the DC bus, the first DC switch and the second DC switch are both connected in series to the DC bus, the slow-start circuit is connected in parallel to the second DC switch, the slow-start circuit is used to adjust the voltage across the second DC switch, and the AC output end of the inverter circuit is used to be connected to the power grid through the grid-connected switch; The controller is configured to control the first DC switch to be closed, and after the first DC switch is closed and when the voltage across the second DC switch is less than or equal to a first voltage threshold, control the second DC switch to be closed, and after the second DC switch is closed, control the grid-connected switch to be closed.

2. The grid-connected power converter according to claim 1, characterized in that: The controller is configured to control the grid-connected switch to be closed after the second DC switch is closed and when the voltage across the grid-connected switch is less than or equal to a second voltage threshold.

3. The grid-connected power converter according to claim 1 or 2, characterized in that: The soft-start circuit includes a third DC switch; The controller is configured to control the first DC switch to be closed, and after the first DC switch is closed, control the third DC switch to be closed to adjust the voltage across the second DC switch, and after the third DC switch is closed and when the voltage across the second DC switch is less than or equal to the first voltage threshold, control the second DC switch to be closed.

4. The grid-connected power converter according to claim 1 or 2, characterized in that: The soft-start circuit includes a third DC switch; The controller is configured to control the first DC switch to be closed, and after the first DC switch is closed, control the third DC switch to be closed to adjust the voltage across the second DC switch, and after the third DC switch is closed and when the voltage across the second DC switch is greater than or equal to a third voltage threshold, control the first DC switch to be opened, and after the first DC switch is opened, control the second DC switch to be closed, and after the second DC switch is closed and when the voltage across the first DC switch is greater than or equal to the third voltage threshold, control the first DC switch to be closed, where the third voltage threshold is greater than the first voltage threshold.

5. The grid-connected power converter according to claim 1 or 2, characterized in that: The soft-start circuit includes a third DC switch; The controller is configured to control the first DC switch to be closed, and after the first DC switch is closed, control the third DC switch to be closed to adjust the voltage across the second DC switch, and after the third DC switch is closed and when the voltage across the second DC switch is greater than or equal to a third voltage threshold, control the second DC switch to be closed, where the third voltage threshold is greater than the first voltage threshold.

6. A grid-connected power converter, characterized in that: The grid-connected power converter includes a DC bus, a first DC switch, a second DC switch, an inverter circuit, a grid-connected switch, and a controller, wherein the inverter circuit is used to convert DC power into AC power, the DC input end of the inverter circuit is used to be connected to the photovoltaic module or the energy storage battery through the DC bus, the first DC switch and the second DC switch are both connected in series to the DC bus, and the AC output end of the inverter circuit is used to be connected to the power grid through the grid-connected switch; The controller is configured to control the grid-connected switch to be closed when the voltage difference across the grid-connected switch is less than or equal to a second voltage threshold, and after the grid-connected switch is closed, control the first DC switch and the second DC switch to be closed.

7. The grid-connected power converter according to claim 6, characterized in that: The controller is configured to control the first DC switch and the second DC switch to be closed after the grid-connected switch is closed and when the voltage difference across the first DC switch and the second DC switch is less than or equal to a first voltage threshold.

8. The grid-connected power converter according to claim 6 or 7, characterized in that: The grid-connected power converter further includes a third DC switch, wherein the third DC switch is connected in parallel with the second DC switch; The controller is configured to control the first DC switch to be closed, control the third DC switch to be closed after the first DC switch is closed, control the first DC switch to be opened after the third DC switch is closed and when the voltage difference across the second DC switch is greater than or equal to a third voltage threshold, control the second DC switch to be closed after the first DC switch is opened, and control the first DC switch to be closed after the second DC switch is closed and when the voltage difference across the first DC switch is greater than or equal to a third voltage threshold, where the third voltage threshold is greater than the first voltage threshold.

9. The grid-connected power converter according to claim 6 or 7, characterized in that: The grid-connected power converter further includes a third DC switch, wherein the third DC switch is connected in parallel with the second DC switch; The controller is configured to control the first DC switch to be closed, and after the first DC switch is closed, control the third DC switch to be closed, and after the third DC switch is closed and when the voltage difference across the second DC switch is greater than or equal to a third voltage threshold, control the second DC switch to be closed, where the third voltage threshold is greater than the first voltage threshold.

10. A power supply system, characterized in that: The power supply system includes an energy storage battery and a grid-connected power converter according to any one of claims 1 to 9, wherein the grid-connected power converter is used to convert direct current from the energy storage battery into alternating current.

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