Inverter and grid-connected and off-grid switching device and method thereof

Abstract

The invention provides an inverter and a grid-connected and off-grid switching device and method thereof, and the device comprises a grid-connected switch which is disposed between an AC side grid-connected port of the inverter and a power grid; the off-grid switch is arranged between the alternating current side off-grid port of the inverter and the load; the grounding switch is configured to be used for controlling connection and disconnection between a neutral line of the inverter and a protective ground line; the control module is configured to control the grid-connected switch and the off-grid switch to be switched on and control the grounding switch to be switched off when the inverter is in a grid-connected state; and when the inverter is in the off-grid state, the grid-connected switch is controlled to be switched off, and the off-grid switch and the grounding switch are controlled to be switched on. The device ensures that the grounding switch and the grid-connected switch are not in a conducting state at the same time, and the safety of the inverter is ensured.

Description

Technical Field

[0001] The present application relates to the technical field of photovoltaic energy storage inverters, and in particular to an inverter and a grid-connected and off-grid switching device and method thereof. Background Art

[0002] In related technologies, with the rapid development of new energy, in order to adapt to various application scenarios, inverters often need to be able to work both in off-grid and grid-connected states. However, how to safely and reliably switch the inverter is a technical problem that needs to be solved. Summary of the Invention

[0003] Based on this, it is necessary to provide an on-grid and off-grid switching device and method for an inverter to address the above technical problems, which can achieve safe and reliable on-grid and off-grid switching of the inverter.

[0004] In a first aspect, the present application provides a grid-connected and off-grid switching device for an inverter, comprising:

[0005] The grid-connected switch is provided between the AC-side grid-connected port of the inverter and the power grid;

[0006] The off-grid switch is installed between the off-grid port on the AC side of the inverter and the load;

[0007] A grounding switch configured to control the connection between the neutral line of the inverter and the protective ground line;

[0008] The control module is configured to: when the inverter is in the grid-connected state, control the grid-connected switch and the off-grid switch to be closed, and control the grounding switch to be opened; when the inverter is in the off-grid state, control the grid-connected switch to be opened and control the off-grid switch and the grounding switch to be closed.

[0009] According to the above description, the grid-connected and off-grid switching device provided in the present application controls the grid-connected switch and the off-grid switch to be closed and the grounding switch to be disconnected when the inverter is in the grid-connected state; when the inverter is in the off-grid state, the grid-connected switch is controlled to be disconnected and the off-grid switch and the grounding switch are controlled to be closed, thereby ensuring that the grounding switch and the grid-connected switch will not be in the on state at the same time, thereby ensuring the safety of the inverter.

[0010] Furthermore, the control module includes a processor, which is used to control the grid-connected switch, the off-grid switch and the grounding switch according to the following method steps:

[0011] Detect whether the grid voltage is normal. When the grid voltage is normal, detect whether the grounding switch is disconnected. If the grounding switch is disconnected, control the grid-connected switch to close, so that the inverter can operate in the grid-connected state.

[0012] When the grid voltage state is abnormal, it detects whether the grid-connected switch is disconnected. When the grid-connected switch is disconnected, it detects whether the grounding switch is closed. If the grounding switch is closed, the off-grid switch is controlled to close, so that the inverter can operate in an off-grid state.

[0013] Furthermore, the control module further includes:

[0014] a grid voltage sampling unit configured to sample the grid voltage and, based on the sampled grid voltage, output a voltage status signal indicating whether the grid voltage status is abnormal;

[0015] a feedback unit configured to monitor the on / off state of the grounding switch and output a feedback signal representing the on / off state of the grounding switch;

[0016] The hardware locking unit is configured to receive a voltage status signal and a feedback signal to implement the following interlocking actions: when the grid voltage status is abnormal or the grounding switch is closed, a grid connection prohibition enable signal is output to the grid connection switch; when the grid voltage status is normal and the grounding switch is open, a grid connection permission enable signal is output;

[0017] The hardware locking unit is further configured to output an off-grid prohibition enable signal to the off-grid switch when the grid voltage state is abnormal and the grounding switch is disconnected.

[0018] Furthermore, the hardware locking unit includes a logic gate circuit;

[0019] The grid voltage sampling unit is configured to generate a low-level voltage state signal when the grid voltage state is abnormal, and to generate a high-level voltage state signal when the grid voltage state is normal;

[0020] The feedback unit is configured to generate a high-level feedback signal when the grounding switch is closed, and to generate a low-level feedback signal when the grounding switch is open;

[0021] The logic gate circuit is configured to output a high-level grid connection enable signal when the received voltage state signal is at a high level and the feedback signal is at a low level; otherwise, output a low-level grid connection disable enable signal.

[0022] Furthermore, the logic gate circuit includes:

[0023] a first XOR gate, wherein input terminals of the first XOR gate receive a voltage state signal and a feedback signal respectively;

[0024] an OR gate, wherein one input terminal of the OR gate is connected to the output terminal of the first XOR gate, and the other input terminal of the OR gate receives a voltage state signal;

[0025] a second XOR gate, one input terminal of the second XOR gate being connected to the output terminal of the OR gate, and the other input terminal of the second XOR gate receiving a feedback signal;

[0026] The output end of the OR gate serves as the enable signal output port of the off-grid switch, and the output end of the second XOR gate serves as the enable signal output port of the grid-connected switch.

[0027] Furthermore, the hardware locking unit also includes a first diode and a second diode, the cathode of the first diode is connected to the output end of the OR gate, the anode of the first diode is connected to the control end of the off-grid switch, the cathode of the second diode is connected to the output end of the second XOR gate, and the anode of the second diode is connected to the control end of the grid-connected switch.

[0028] Furthermore, the hardware locking unit is further configured to: when the grounding switch is in a closed state, output an off-grid enabling signal to the off-grid switch.

[0029] In a second aspect, the present application further provides a method for switching an inverter on and off the grid, using the above-mentioned on and off-grid switching device, the method comprising:

[0030] Detect whether the grid voltage is normal. When the grid voltage is normal, detect whether the grounding switch is disconnected. If the grounding switch is disconnected, control the grid-connected switch to close, so that the inverter can operate in the grid-connected state.

[0031] When the grid voltage state is abnormal, it detects whether the grid-connected switch is disconnected. When the grid-connected switch is disconnected, it detects whether the grounding switch is closed. If the grounding switch is closed, the off-grid switch is controlled to close, so that the inverter can operate in an off-grid state.

[0032] In a third aspect, the present application further provides an inverter, which includes an inverter circuit and the on-grid and off-grid switching device as described above.

[0033] Furthermore, the inverter is used in a three-phase system, the off-grid switch is an off-grid relay, the grid-connected switch is a grid-connected relay, and the grounding switch is a grounding relay. The grid-connected switch is arranged between the AC side grid-connected port of the inverter and the power grid, the off-grid switch is arranged between the AC side off-grid port of the inverter and the load, and the grounding switch is arranged between the neutral line and the ground line of the inverter.

[0034] For the detailed description of the second and third aspects and their various implementations in this application, reference may be made to the detailed description of the first aspect and its various implementations. For the beneficial effects of the second and third aspects and their various implementations, reference may be made to the beneficial effects analysis of the first aspect and its various implementations, and no further details will be given here. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A diagram of a device for switching an inverter on and off the grid provided in an embodiment of the present application;

[0036] Figure 2 Schematic diagram of the solar storage system provided in the embodiment of the present application;

[0037] Figure 3 A processor control block diagram provided for an embodiment of the present application;

[0038] Figure 4 A schematic diagram of a control module provided in an embodiment of the present application;

[0039] Figure 5 A circuit diagram of a feedback unit provided in an embodiment of the present application;

[0040] Figure 6 A diagram of the system architecture for the collaborative operation and interlocking of software and hardware provided in the embodiments of the present application;

[0041] Figure 7 A flow chart of controlling an inverter to switch from a grid-connected mode to an off-grid mode provided in an embodiment of the present application;

[0042] Figure 8 A flow chart of controlling an inverter to switch from an off-grid mode to a grid-connected mode provided in an embodiment of the present application;

[0043] Figure 9 A flowchart of hardware logic action interlocking and safety authentication of the inverter provided in an embodiment of the present application;

[0044] Figure 10 A schematic diagram of a three-phase system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0046] like Figure 1 As shown, an embodiment of the present application provides an inverter on-grid and off-grid switching device, comprising a grid-connected switch 11, an off-grid switch 12, and a grounding switch 13. The grid-connected switch is disposed between the AC-side grid-connected port of the inverter and the grid; the off-grid switch is disposed between the AC-side off-grid port of the inverter and the load; and the grounding switch is configured to control the connection between the neutral line of the inverter and the protective ground line.

[0047] The on-grid and off-grid switching device provided in the embodiment of the present application also includes a control module, which is configured to: when the inverter is in a grid-connected state, control the grid-connected switch and the off-grid switch to be closed, and control the grounding switch to be disconnected; when the inverter is in an off-grid state, control the grid-connected switch to be disconnected and control the off-grid switch and the grounding switch to be closed.

[0048] The on-grid and off-grid switching device provided by the embodiment of the present application can realize safe and reliable on-grid and off-grid switching of the inverter. Specifically, the inverter can be used in energy storage systems, and can also be used in photovoltaic storage systems. Taking photovoltaic storage systems as an example, Figure 2 As shown, the DC side of the inverter is connected to the photovoltaic cell and the energy storage device, the AC side grid-connected port of the inverter is connected to the grid through the grid-connected switch, the AC side off-grid port of the inverter is connected to the load through the off-grid switch, and the neutral line of the inverter can be grounded through the grounding switch.

[0049] The inverter can include two modes, one of which is the grid-connected mode. In the grid-connected mode, the grid-connected switch is closed and the photovoltaic storage system is connected to the grid. At this time, photovoltaic power generation can be input into the grid through the inverter, or the grid can also transmit electricity to the photovoltaic storage system (such as using the grid to charge the energy storage device during the off-peak period). In the grid-connected mode, the off-grid switch can be closed or not according to actual needs. When both the grid-connected switch and the off-grid switch are closed, the photovoltaic cell and the energy storage battery meet the household energy-saving needs under the regulation of the EMS. Another mode of the inverter is the off-grid mode. In the off-grid mode, the grid-connected switch is disconnected and the off-grid switch is closed. At this time, the grid-connected port is vacant, and the off-grid port is controlled by the inverter as a power port. Photovoltaic cells or energy storage devices can be used to power the load through the inverter.

[0050] To ensure safe and reliable on-grid and off-grid switching of the inverter, the on-grid and off-grid switching device provided herein controls the closing of the grid-connected and off-grid switches and the disconnection of the grounding switch when the inverter is in the grid-connected state. At this point, the inverter is connected to the main grid and operates in current source mode. Because the inverter's neutral line is grounded at either the far or near end when connected to the main grid, disconnecting the grounding switch ensures safe operation of the inverter.

[0051] When the inverter is in the off-grid state, the grid-connected switch is controlled to be disconnected, and the off-grid switch and the grounding switch are controlled to be closed. In this way, the neutral line of the inverter is short-circuited with the ground line in the off-grid mode to simulate the connection method of the real grid, so that the inverter itself acts as a "grid" and operates in the form of a voltage source to provide power to the load.

[0052] According to the above description, the on-grid and off-grid switching device provided in the embodiment of the present application can realize safe and reliable on-grid and off-grid switching of the inverter.

[0053] As an optional implementation, in the grid-connected and off-grid switching device provided in an embodiment of the present application, the control module further includes a processor, and the processor is configured to control the grid-connected switch, the off-grid switch, and the grounding switch according to the following method steps:

[0054] Detect whether the grid voltage is normal. When the grid voltage is normal, detect whether the grounding switch is disconnected. If the grounding switch is disconnected, control the grid-connected switch to close, so that the inverter can operate in the grid-connected state.

[0055] When the grid voltage state is abnormal, it detects whether the grid-connected switch is disconnected. When the grid-connected switch is disconnected, it detects whether the grounding switch is closed. If the grounding switch is closed, the off-grid switch is controlled to close, so that the inverter can operate in an off-grid state.

[0056] Specifically, such as Figure 3 As shown, the processor controls the inverter through software control as follows: the processor detects whether the grid voltage state is normal. If the grid voltage state is normal, it first detects whether the grounding switch is disconnected. When it is determined through software detection means that the grounding switch is disconnected, the grid-connected switch is controlled to be closed, and the inverter is connected to the grid for operation; if it is determined through software detection means that the grounding switch is turned on (such as the switch fault is attracted), the processor will wait until the grounding switch is disconnected before controlling the grid-connected switch to be turned on, thereby ensuring that the grounding switch and the grid-connected switch will not be turned on at the same time, ensuring the safe operation of the inverter.

[0057] If the grid voltage status is abnormal, the software detection method is first used to detect whether the grid-connected switch is disconnected. When the grid-connected switch is disconnected, the software detection method is then used to detect whether the grounding switch is closed. If the grounding switch is closed, the off-grid switch is controlled to close, so that the inverter can operate in the off-grid state. If the software detection method determines that the grounding switch is disconnected, the processor will wait for the grounding switch to be closed before controlling the off-grid switch to be turned on, thereby ensuring that the inverter can operate safely in the off-grid mode.

[0058] As an optional implementation, such as Figure 4 As shown, the control module further includes: a grid voltage sampling unit, a feedback unit and a hardware locking unit.

[0059] The grid voltage sampling unit is configured to sample the grid voltage and, based on the sampled grid voltage, output a voltage status signal indicating whether the grid voltage state is abnormal; the feedback unit is configured to monitor the on / off state of the grounding switch and output a feedback signal indicating the on / off state of the grounding switch; the hardware locking unit is configured to receive the voltage status signal and the feedback signal to implement the following action interlocking: when the grid voltage state is abnormal, or the grounding switch is closed, a grid connection prohibition enable signal is output; when the grid voltage state is normal and the grounding switch is disconnected, a grid connection permission enable signal is output; when the grid voltage state is abnormal and the grounding switch is disconnected, an off-grid prohibition enable signal is output to the off-grid switch.

[0060] Specifically, the grid-connected and off-grid switching device provided by the present application is provided with hardware interlock protection on the basis of the software control of the processor. Through the hardware locking unit, a grid-connected prohibition enable signal is output when the grid voltage state is abnormal, thereby preventing the inverter from being connected to the grid when the grid is abnormal, further ensuring the safe operation of the inverter. In addition, the hardware locking unit is used to output the grid-connected prohibition enable signal when the grounding switch is closed, thereby ensuring that the grounding switch and the grid-connected switch will not be turned on at the same time, further ensuring the safe operation of the inverter. Through the hardware locking unit, a grid-connected permission enable signal is output when the grid voltage state is normal and the grounding switch is disconnected, thereby ensuring that the grounding switch is disconnected during grid-connected operation, further ensuring the safe operation of the inverter. Through the hardware locking unit, when the grid voltage state is abnormal and the grounding switch is disconnected, an off-grid prohibition enable signal is output to the off-grid switch, thereby ensuring that the grounding switch is closed in the off-grid state, further ensuring the safe operation of the inverter.

[0061] As described above, the on-grid and off-grid switching device provided by this application improves the safety of inverter on-grid and off-grid switching through dual software and hardware protection, ensuring the safe operation of the inverter. In addition, hardware response speed is faster than software control, and hardware interlock protection helps to improve the response speed of protection.

[0062] As an optional implementation, the grid voltage sampling unit is configured to generate a low-level voltage status signal when the voltage is abnormal, and to generate a high-level voltage status signal when the voltage is normal; the feedback unit is configured to generate a high-level feedback signal when the grounding switch is closed, and to generate a low-level feedback signal when the grounding switch is open; the logic gate circuit is configured to output a high-level grid connection enable signal when the received voltage status signal is high and the feedback signal is low, otherwise, it outputs a low-level grid connection prohibition enable signal.

[0063] Specifically, one or more of the following indicators can be used to determine whether the grid voltage is abnormal: voltage amplitude, voltage fluctuation amplitude, phase effective value difference, etc. In the embodiment of the present application, when the grid voltage is abnormal, a low-level voltage status signal is generated, and when the grid voltage is normal, a high-level voltage status signal is generated. When the grid voltage is abnormal, the grid-connected switch is automatically controlled to disconnect to ensure that the abnormal grid voltage does not affect the inside of the photovoltaic storage system. When the grid voltage returns to normal, it is necessary to determine whether the grid-connected switch can be closed according to the switching method provided in the present application. The switching method is specifically described later. It is easy to understand that when the voltage is abnormal, a high-level voltage status signal can also be generated, and when the voltage is normal, a low-level voltage status signal can be generated. In this case, in order to achieve the same logical interlocking requirements of the grid-connected and off-grid modes, it is necessary to adaptively adjust the logic gate circuit in the hardware locking unit.

[0064] like Figure 5 As shown, an implementation of a feedback unit is provided. The feedback unit includes resistors R1 and R2 and a feedback switch. The power supply VCC is grounded through the series-connected resistors R1 and R2. The connection node between the resistors R1 and R2 is grounded through the feedback switch. The feedback switch is configured to remain closed when the ground switch is disconnected, and remain open when the ground switch is closed. The connection node between the resistors R1 and R2 serves as the output node of the feedback signal. Based on the above, Figure 5 In the feedback unit shown, when the grounding switch is open, the feedback switch remains closed, pulling the potential of the connection node between resistors R1 and R2 to a low level, outputting a low-level feedback signal. When the grounding switch is closed, the feedback switch remains open, pulling the potential of the connection node between resistors R1 and R2 to a high level, outputting a high-level feedback signal. In one embodiment, the feedback switch and the grounding switch can be integrated into a relay with contact state feedback.

[0065] Through Figure 5 The feedback unit shown can monitor the on / off status of the neutral line (N) and the protective earth line (PE) of the grounding switch and generate a corresponding feedback signal according to the on / off status of the grounding switch.

[0066] The logic gate circuit is configured to output a high-level grid connection enable signal only when the received voltage state signal is high and the feedback signal is low; otherwise, it outputs a low-level grid connection prohibition enable signal.

[0067] Specifically, when the voltage status signal received by the logic gate circuit is at a high level and the feedback signal is at a low level, it means that the grid voltage is normal and the grounding switch is in the disconnected state. The logic gate circuit outputs a high-level grid-connection enable signal, allowing the grid-connected switch to be closed to connect the inverter to the grid.

[0068] In all other cases, the logic gate circuit outputs a low-level grid connection disable signal. For example, if the voltage status signal is high but the feedback signal is also high, this means that although the grid voltage is normal, the grounding switch is still closed. To avoid repeated grounding conflicts, the inverter is prohibited from connecting to the grid. Alternatively, if the voltage status signal is low, this means the grid voltage is abnormal. In this case, regardless of whether the feedback signal is high or low, the inverter is not allowed to connect to the grid, thus ensuring the safe operation of the solar-storage system.

[0069] As described above, the grid-connected and off-grid switching device provided in this application implements interlocking between the grid-connected switch and the grounding switch through hardware logic circuit design, ensuring that the grid-connected switch will not close while the grounding switch is on. This approach is more reliable than software-implemented relay interlocking and can ensure safe operation of the inverter.

[0070] As an optional implementation, the logic gate circuit is further configured to output a low-level off-grid disable enable signal when the received voltage status signal is at a low level and the feedback signal is at a low level.

[0071] Specifically, when the voltage status signal is at a low level, it means that the grid voltage is abnormal. Based on the power supply demand of the load without power outage, the inverter should switch from the grid-connected mode to the off-grid mode. However, if the feedback signal is at a low level, it means that the grounding switch is still in the disconnected state. In this case, the grid-connected and off-grid switching device provided in this application prohibits the inverter from switching to the off-grid mode, thereby ensuring the safety of electrical appliances.

[0072] As an optional implementation, the hardware locking unit is further configured to output an off-grid enable signal to the off-grid switch when the grounding switch is closed. Specifically, when the voltage status signal is high, indicating normal grid voltage and the inverter is in grid-connected mode, the logic gate circuit outputs a high-level off-grid enable signal. At this point, the off-grid switch can decide whether to close based on actual needs.

[0073] In order to further illustrate the grid-connected and off-grid switching device provided by the present application, the following exemplary implementation of a logic gate circuit is provided. As an optional implementation, Figure 4 As shown, the logic gate circuit includes: a first XOR gate, an OR gate and a second XOR gate.

[0074] The input ends of the first XOR gate receive the voltage state signal and the feedback signal respectively; one input end of the OR gate is connected to the output end of the first XOR gate, and the other input end of the OR gate receives the voltage state signal; one input end of the second XOR gate is connected to the output end of the OR gate, and the other input end of the second XOR gate receives the feedback signal; the output end of the OR gate is connected to the control end of the off-grid switch, that is, the control end of the off-grid switch receives the off-grid switch drive signal and the off-grid enable signal, and the output end of the OR gate serves as the enable signal output port of the off-grid switch; the output end of the second XOR gate is connected to the control end of the grid-connected switch, that is, the control end of the grid-connected switch receives the grid-connected switch drive signal and the grid-connected enable signal, and the output end of the second XOR gate serves as the enable signal output port of the grid-connected switch.

[0075] This embodiment implements a hardware interlocking function through logical constraints using two or more electronic components, providing greater reliability than software implementations. Specifically, when operating in both on-grid and off-grid modes, a hardware interlock design is added to the grounding switch between the neutral line N and the protective ground line PE within the inverter, interlocking the operation with the on-grid switch or off-grid switch. This hardware interlock design can be used in conjunction with software interlocking for dual security protection, or it can be used independently to ensure safety.

[0076] As an optional implementation, such as Figure 4 As shown, the hardware locking unit further includes a first diode D1 and a second diode D2, wherein the cathode of the first diode D1 is connected to the output end of the OR gate, the anode of the first diode D1 is connected to the control end of the off-grid switch, the cathode of the second diode D2 is connected to the output end of the second XOR gate, and the anode of the second diode D2 is connected to the control end of the grid-connected switch.

[0077] When the OR gate outputs a high-level signal "1", the first diode D1 is cut off, the off-grid switch group drive will be released and enabled, and the off-grid switch drive signal can be normally input to the off-grid switch, indicating that the inverter is allowed to operate off-grid; when the OR gate outputs a low-level signal "0", the first diode D1 is turned on, the off-grid switch drive signal is pulled low, and the off-grid switch is disabled, that is, the off-grid switch drive signal cannot be normally input to the off-grid switch, indicating that the inverter is not allowed to operate off-grid.

[0078] When the second XOR gate outputs a low-level signal "0", the diode D2 is turned on, the driving signal of the grid-connected switch is pulled low, and the grid-connected switch group drive will be disabled. In other words, the driving signal of the grid-connected switch cannot be normally input to the grid-connected switch, indicating that the inverter is not allowed to be grid-connected; when the second XOR gate outputs a high-level signal "1", the diode D2 is turned off, the grid-connected switch group drive will be released and enabled, and the driving signal of the grid-connected switch can be normally input to the grid-connected switch, indicating that the inverter is allowed to be grid-connected.

[0079] For ease of explanation, when the voltage state is normal, the voltage state signal is recorded as a high-level signal "1"; conversely, when the voltage state is abnormal, the voltage state signal is recorded as a low-level signal "0." When the grounding switch is closed, the feedback signal generated by the feedback unit is recorded as a high-level signal "1," and when the grounding switch is open, the feedback signal generated is recorded as a low-level signal "0." The inputs of the first XOR gate are the voltage state signal and the feedback signal, respectively. Based on the output logic of the XOR gate, the output signal of the first XOR gate can be shown in Table 1 below:

[0080] Voltage status signal Feedback signal The first XOR gate output signal 0 0 0 0 1 1 1 0 1 1 1 0

[0081] The input signal of the OR gate is the output signal of the first XOR gate and the voltage state signal. Combined with Table 1, the input of the OR gate has four conditions as shown in Table 2 below. Therefore, the output signal of the OR gate can be shown in Table 2 below:

[0082]

[0083] The input signal of the second XOR gate is the feedback signal and the output signal of the OR gate. Combined with Table 2, the output signal of the second XOR gate can be shown in Table 3 below:

[0084]

[0085] like Figure 4 As shown, the output of the OR gate can serve as the enable signal output for the off-grid switch. Combined with Table 2, it can be seen that when the logic gate circuit receives a low-level "0" voltage state signal and a low-level "0" feedback signal, the OR gate outputs a low-level "0" off-grid disable enable signal. In all other cases, the OR gate outputs a high-level "1" off-grid enable signal. This ensures that the grounding switch remains closed in the inverter's off-grid mode, shorting the inverter's N and PE lines in this mode to simulate a real grid connection and provide a safe operating environment for electrical appliances.

[0086] The output of the second XOR gate serves as the enable signal output port for the grid-connected switch. As shown in Table 3, the logic gate circuit outputs a high-level grid-connection enable signal only when the voltage status signal is high-level "1" and the feedback signal is low-level "0." Otherwise, it outputs a low-level grid-connection disable signal. In other words, the grid-connected switch can only be closed when the grid voltage is normal and the grounding switch is open. This ensures that the grounding switch is open when the grid-connected switch is closed, achieving hardware interlocking between the grid-connected switch and the grounding switch, ensuring safe operation of the inverter.

[0087] In order to further illustrate the hardware locking unit provided by this application, the following Figure 4 Table 3 and Table 3 illustrate four situations of hardware locking unit.

[0088] The first situation is: when the grid voltage state is abnormal (the voltage state signal is "0") and the grounding switch is in the disconnected state (the feedback signal is "0"), according to the output logic of the XOR gate "different is 1, the same is 0", the first XOR gate outputs a low-level signal "0" at this time; the two input ends of the OR gate receive the low-level voltage state signal and the low-level first XOR gate output signal respectively. According to the output logic of the OR gate "as long as one of the input ends is 1, the output of the OR gate is 1", the OR gate outputs a low-level signal "0" at this time, the diode D1 is turned on, the driving signal of the off-grid switch is pulled low, and the off-grid switch is disabled. Enable, that is, the driving signal of the off-grid switch cannot be normally input to the off-grid switch, which means that the inverter is not allowed to go off-grid; the two input ends of the second XOR gate receive the low-level feedback signal and the low-level OR gate output signal respectively. Referring to the output logic of the XOR gate, the second XOR gate outputs a low-level signal "0". At this time, the diode D2 is turned on, the driving signal of the grid-connected switch is pulled low, and the grid-connected switch group drive will be disabled. In other words, the driving signal of the grid-connected switch cannot be normally input to the grid-connected switch, which means that the inverter is not allowed to be connected to the grid, preventing the inverter from being connected to the grid when the grid voltage is abnormal, thereby ensuring the safety of the inverter.

[0089] The second situation is: when the grid voltage state is abnormal (the voltage state signal is "0") and the grounding switch is in the closed state (the feedback signal is "1"), according to the output logic of the XOR gate "different is 1, the same is 0", the first XOR gate outputs a high-level signal "1" at this time; the two input ends of the OR gate receive the low-level voltage state signal and the high-level first XOR gate output signal respectively. According to the output logic of the OR gate "as long as one input end is 1, the output of the OR gate is 1", the OR gate outputs a high-level signal "1". At this time, the diode D1 is cut off, and the off-grid switch group drive will be released and enabled. The driving signal of the off-grid switch can be input to the off-grid switch normally, indicating that the inverter is allowed to operate off-grid. The two input ends of the second XOR gate receive the high-level feedback signal and the high-level OR gate output signal respectively. Referring to the output logic of the XOR gate, the second XOR gate outputs a low-level signal "0". At this time, the diode D2 is turned on, the driving signal of the grid-connected switch is pulled low, and the grid-connected switch group drive will be disabled. That is, the driving signal of the grid-connected switch cannot be input to the grid-connected switch normally, indicating that the inverter is not allowed to be connected to the grid, preventing the inverter from being connected to the grid when the grounding switch is closed, thereby ensuring the safety of the inverter.

[0090] The third scenario is: when the grid voltage is normal (the voltage status signal is "1") and the grounding switch is in the open state (the feedback signal is "0"), the first XOR gate outputs a high-level signal "1" according to the output logic of the XOR gate: "different is 1, the same is 0"; the two input terminals of the OR gate receive the high-level voltage status signal and the high-level first XOR gate output signal respectively. According to the output logic of the OR gate: "as long as one input terminal is 1, the OR gate output is 1", the OR gate outputs a high-level signal "1". At this time, the diode D1 is cut off, the off-grid switch group drive will be released and enabled, and the off-grid switch drive signal can be normally input to the off-grid switch, indicating that the inverter is allowed to operate off the grid; the two input terminals of the second XOR gate receive the low-level feedback signal and the high-level OR gate output signal respectively. Referring to the output logic of the XOR gate, the second XOR gate outputs a high-level signal "1". At this time, the diode D2 is cut off, the grid-connected switch group drive will be released and enabled, and the grid-connected switch drive signal can be normally input to the grid-connected switch, indicating that the inverter is allowed to be connected to the grid.

[0091] The fourth situation is: when the grid voltage is normal (the voltage status signal is "1") and the grounding switch is in the closed state (the feedback signal is "1"), according to the output logic of the XOR gate "different is 1, the same is 0", the first XOR gate outputs a low-level signal "0" at this time; the two input ends of the OR gate receive the high-level voltage status signal and the low-level output signal of the first XOR gate respectively. According to the output logic of the OR gate "as long as one of the input ends is 1, the output of the OR gate is 1", the OR gate outputs a high-level signal "1". At this time, the diode D1 is cut off, and the off-grid switch group drive will be released and enabled. The driving signal of the off-grid switch can be input to the off-grid switch normally, indicating that the inverter is allowed to operate off-grid. The two input ends of the second XOR gate receive the high-level feedback signal and the high-level OR gate output signal respectively. Referring to the output logic of the XOR gate, the second XOR gate outputs a low-level signal "0". At this time, the diode D2 is turned on, the driving signal of the grid-connected switch is pulled low, and the grid-connected switch group drive will be disabled. That is, the driving signal of the grid-connected switch cannot be input to the grid-connected switch normally, indicating that the inverter is not allowed to be connected to the grid, preventing the inverter from being connected to the grid when the grounding switch is closed, thereby ensuring the safety of the inverter.

[0092] Acceptable, when the grounding switch is in the closed state, regardless of whether the grid voltage is normal, the OR gate outputs a high-level signal. At this time, the diode D1 is cut off, the off-grid switch group drive will be released and enabled, the off-grid switch drive signal can be normally input to the off-grid switch, and the system supports off-grid operation.

[0093] According to the above description, the on-grid and off-grid switching device provided by the present application can realize the logical interlocking of the grounding switch in both on-grid and off-grid modes in the simplest, easiest and lowest-cost way through the hardware locking unit when switching between the on-grid and off-grid working modes of the inverter, thereby ensuring system safety.

[0094] As an optional implementation method, the processor receives a voltage status signal and a feedback signal, and runs a computer program on the processor. When the processor executes the computer program, the grounding switch is disconnected in the grid-connected mode and the grounding switch is closed in the off-grid mode. When the inverter passes the safety authentication of the hardware locking unit and the processor's action interlock, it is determined that the inverter is operating normally.

[0095] Specifically, while this application utilizes hardware logic gate circuits to interlock the grounding switch with the grid-connected and off-grid switches, it also employs software to interlock the grounding switch with the grid-connected and off-grid switches. A processor in the grid-connected and off-grid switching device is responsible for receiving voltage status signals and feedback signals. A computer program running on the processor enables it to execute preset control logic. In grid-connected mode, the processor opens the grounding switch to prevent an unnecessary connection between the inverter's neutral line and the protective ground wire. In off-grid mode, the processor closes the grounding switch to simulate a grid connection and ensure normal power supply to the load.

[0096] This application ensures that the action of the grounding switch in grid-connected and off-grid modes meets safety requirements through dual safety certification of the hardware locking unit and the processor software interlock. The hardware locking unit realizes the control and protection of the relay through the logic gate circuit, while the processor performs software-level control and protection by running the computer program. The hardware and software work together. The processor will sample the grid voltage to determine whether the grid is in a normal state, and the feedback signal of the N-line grounding switch is synchronously input to the processor IO pin. When the hardware locking unit is running, the firmware in the microprocessor will monitor the operating status of the hardware locking unit, assuming the second line of defense for this function, forming an action interlock to prevent the grid-connected switch and the grounding switch from being closed at the same time at inappropriate times, thereby avoiding possible failures or safety risks. This dual protection mechanism improves the reliability and safety of the inverter operation.

[0097] As an optional implementation, such as Figure 6 As shown, the figure shows the system architecture diagram of the collaborative operation interlock of software and hardware. The hardware locking unit outputs the corresponding locking signal of the grid-connected switch or the off-grid switch according to the received feedback signal and the grid voltage status signal, and the logic gate circuit provided in the embodiment of the present application outputs the locking signal of the grid-connected switch or the off-grid switch (the locking signal can be a relay enable signal or a disable enable signal). The processor can execute the software locking monitoring program. Through the software locking monitoring program, the status of the grid-connected switch, the off-grid switch and the grounding switch can be checked, and the following relay interlock is realized through software control: the grounding switch is disconnected when the grid-connected switch is closed, and the grounding switch is closed when the grid-connected mode of the inverter is switched to the off-grid mode. In addition, the processor can also verify the relay locking signal output of the hardware locking unit and the relay status (including the grid-connected switch, the off-grid switch and the grounding switch) through the software locking monitoring program to determine whether the hardware locking unit is working properly. When the inverter passes the safety certification of the dual action interlock of the hardware locking unit and the processor, it can be determined that the inverter is working properly.

[0098] Based on the above description, the on-grid and off-grid switching device provided by this application utilizes a simple, reliable, and low-cost hardware interlock circuit and software monitoring system to achieve hardware logic interlocking of the N-line grounding switch in both on-grid and off-grid modes. Combined with software synchronization monitoring, this system ensures safe operation in both modes. The on-grid and off-grid switching device provided by this application, through dual software and hardware protection, ensures that the grounding switch and the grid-connected switch will not be in the on state at the same time, thus ensuring inverter safety.

[0099] Based on the same concept as the on-grid and off-grid switching device of the inverter, the present application also provides an on-grid and off-grid switching method of the inverter, such as Figure 7 As shown, the method is applied to an on-grid and off-grid switching device of an inverter, and the method includes controlling the inverter to switch from a on-grid mode to an off-grid mode, including the following steps:

[0100] Step 601: Control the grid-connected switch to be disconnected, and control the grounding switch to be closed, and output a grid-connection prohibition enable signal and a grid-off permission enable signal through a hardware locking unit.

[0101] Step 602: When an off-grid enabling signal is obtained, the off-grid switch is controlled to close.

[0102] Specifically, according to the grid-connected and off-grid switching method provided in this application, when controlling the inverter to switch from grid-connected mode to off-grid mode, the grid-connected switch is first controlled to be disconnected. After determining that the grid-connected switch is disconnected, the grounding switch is controlled to be closed. After the grounding switch is closed, the hardware locking unit outputs a grid-connected prohibition enable signal to prevent the grid-connected switch from being mistakenly closed at this time, and sends an off-grid enable signal. After obtaining the off-grid enable signal, the off-grid switch is controlled to be closed. The above switching method can ensure that the grid-connected switch and the grounding switch are not in the closed state at the same time during the switching process, and can ensure that when switching to off-grid mode, the closed grounding switch can simulate a real power grid, thereby providing a safe operating environment for electrical appliances and ensuring safety.

[0103] As an optional implementation, such as Figure 8 As shown, the method includes controlling the inverter to switch from an off-grid mode to a grid-connected mode, including the following steps:

[0104] Step 701: Acquire a voltage status signal. When the grid voltage is normal, control the grounding switch to be disconnected, and acquire a feedback signal after the grounding switch is disconnected.

[0105] Step 702: Based on the voltage state signal and the feedback signal, a grid connection enabling signal is outputted via a hardware locking unit.

[0106] Step 703: When the grid connection enabling signal is obtained, the grid connection switch is controlled to close.

[0107] Specifically, according to the grid-connected and off-grid switching method provided by the present application, when the grid voltage returns to normal, the inverter is controlled to switch from the grid-connected mode to the off-grid mode. After the hardware locking unit receives a high-level voltage status signal, it controls the grounding switch to be disconnected, even if the neutral line of the inverter is disconnected from the protective ground line. After the grounding switch is disconnected, the feedback unit monitors the state change of the grounding switch and outputs a low-level feedback signal, indicating that the grounding switch has been disconnected. The feedback signal is used to confirm the actual state of the grounding switch. After receiving the high-level voltage status signal and the low-level feedback signal, the hardware locking unit outputs a high-level grid-connected enable signal to allow the grid-connected switch to be closed, so that the inverter can operate in grid connection.

[0108] In this embodiment, when the grid voltage is normal, the grounding switch is controlled to open, and its status is confirmed through a feedback signal. Combining the normal voltage status signal with the feedback signal indicating the grounding switch is open, the hardware locking unit outputs an enable signal, thereby safely closing the grid-connecting switch and connecting the inverter to the grid. This method ensures that the inverter is connected to the grid only when the grid voltage is normal and the grounding switch is open, effectively improving safety and reliability.

[0109] As an optional implementation, such as Figure 9 As shown, the method further includes the following steps:

[0110] Step 801: Execute a computer program to implement an action interlock of opening the grounding switch in the grid-connected mode and closing the grounding switch in the off-grid mode.

[0111] Step 802: After the inverter passes the safety authentication of the hardware locking unit and the action interlock of the processor, it is determined that the inverter is operating normally.

[0112] Specifically, the computer program running on the processor monitors voltage status signals and feedback signals to determine the inverter's operating mode and execute the corresponding control logic. In grid-connected mode, the program ensures that the grounding switch is open to prevent an unnecessary connection between the inverter's neutral line and the protective ground wire. In off-grid mode, the program ensures that the grounding switch is closed to simulate a grid connection and ensure proper power supply to the load. After the inverter passes dual safety authentication by the hardware lock unit and the processor, it is deemed to be operating normally. This indicates that both the inverter's hardware and software are correctly executing safety logic, ensuring that the grounding switch operates in compliance with safety requirements in both grid-connected and off-grid modes. The hardware lock unit and the processor work together, and this dual security mechanism improves the reliability and safety of the inverter's operation.

[0113] Based on the same concept, the present application also provides an inverter, which includes an inverter circuit and an on-grid and off-grid switching device of the inverter.

[0114] The inverter includes an inverter circuit and an on-grid and off-grid switching device provided in an embodiment of the present application. The inverter circuit is responsible for converting direct current into alternating current, while the on-grid and off-grid switching device is used to configure the inverter to safely switch between on-grid and off-grid modes. According to the inverter provided in this application, the dual interlocking protection of software and hardware realizes that when the inverter is in the grid-connected state, the grid-connected switch and the off-grid switch are controlled to be closed and the grounding switch is controlled to be disconnected; when the inverter is in the off-grid state, the grid-connected switch is controlled to be disconnected and the off-grid switch and the grounding switch are controlled to be closed, thereby ensuring the safe operation of the inverter.

[0115] As an optional implementation, the inverter is used in a three-phase system. Figure 10 As shown, the off-grid switch 12 is an off-grid relay, the grid-connected switch 11 is a grid-connected relay, and the grounding switch 13 is a grounding relay. The grid-connected switch 11 is arranged between the AC-side grid-connected port of the inverter and the grid, the off-grid switch 12 is arranged between the AC-side off-grid port of the inverter and the load, and the grounding switch 13 is arranged between the neutral line and the ground line of the inverter.

[0116] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0117] The above embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A grid-connected and off-grid switching device for an inverter, characterized in that: include: A grid-connected switch, provided between the AC-side grid-connected port of the inverter and the power grid; An off-grid switch is provided between the off-grid port on the AC side of the inverter and the load; A grounding switch configured to control the connection between the neutral line and the protective ground line of the inverter; The control module is configured to: when the inverter is in a grid-connected state, control the grid-connected switch and the off-grid switch to be closed, and control the grounding switch to be open; when the inverter is in an off-grid state, control the grid-connected switch to be open, and control the off-grid switch and the grounding switch to be closed.

2. The on-grid and off-grid switching device of the inverter according to claim 1, characterized in that: The control module includes a processor, and the processor is used to control the grid-connected switch, the off-grid switch, and the grounding switch according to the following method steps: Detecting whether the grid voltage state is normal, and when the grid voltage state is normal, detecting whether the grounding switch is disconnected, and if the grounding switch is disconnected, controlling the grid-connected switch to close, so that the inverter operates in a grid-connected state; When the grid voltage state is abnormal, detect whether the grid-connected switch is disconnected. When the grid-connected switch is disconnected, detect whether the grounding switch is closed. If the grounding switch is closed, control the off-grid switch to be closed, so that the inverter operates in an off-grid state.

3. The on-grid and off-grid switching device of the inverter according to claim 1 or 2, characterized in that: The control module further includes: a grid voltage sampling unit configured to sample the grid voltage and, based on the sampled grid voltage, output a voltage status signal indicating whether the grid voltage status is abnormal; a feedback unit configured to monitor the on / off state of the grounding switch and output a feedback signal representing the on / off state of the grounding switch; The hardware locking unit is configured to receive the voltage status signal and the feedback signal and implement the following action interlocking: when the grid voltage status is abnormal or the grounding switch is closed, output a grid connection prohibition enable signal to the grid connection switch; when the grid voltage status is normal and the grounding switch is open, output a grid connection permission enable signal; The hardware locking unit is further configured to output an off-grid prohibition enable signal to the off-grid switch when the grid voltage state is abnormal and the grounding switch is disconnected.

4. The on-grid and off-grid switching device of the inverter according to claim 3, characterized in that: The hardware locking unit includes a logic gate circuit; The grid voltage sampling unit is configured to generate a low-level voltage state signal when the grid voltage state is abnormal, and to generate a high-level voltage state signal when the grid voltage state is normal; The feedback unit is configured to generate a high-level feedback signal when the grounding switch is closed, and to generate a low-level feedback signal when the grounding switch is open; The logic gate circuit is configured to output a high-level grid connection enable signal when the received voltage state signal is at a high level and the feedback signal is at a low level; otherwise, output a low-level grid connection disable signal.

5. The on-grid and off-grid switching device of the inverter according to claim 4, characterized in that: The logic gate circuit comprises: a first XOR gate, wherein input terminals of the first XOR gate receive the voltage state signal and the feedback signal respectively; an OR gate, wherein one input terminal of the OR gate is connected to the output terminal of the first XOR gate, and the other input terminal of the OR gate receives the voltage state signal; a second XOR gate, wherein one input terminal of the second XOR gate is connected to the output terminal of the OR gate, and the other input terminal of the second XOR gate receives the feedback signal; The output end of the OR gate serves as the enable signal output port of the off-grid switch, and the output end of the second XOR gate serves as the enable signal output port of the grid-connected switch.

6. The on-grid and off-grid switching device of the inverter according to claim 5, characterized in that: The hardware locking unit also includes a first diode and a second diode, the cathode of the first diode is connected to the output end of the OR gate, the anode of the first diode is connected to the control end of the off-grid switch, the cathode of the second diode is connected to the output end of the second XOR gate, and the anode of the second diode is connected to the control end of the grid-connected switch.

7. The on-grid and off-grid switching device of the inverter according to claim 3, characterized in that: The hardware locking unit is further configured to: when the grounding switch is in a closed state, output an off-grid enabling signal to the off-grid switch.

8. A method for switching an inverter on and off the grid, characterized in that: Applying the on-grid and off-grid switching device according to any one of claims 1 to 7, the method comprises: Detecting whether the grid voltage state is normal, and when the grid voltage state is normal, detecting whether the grounding switch is disconnected, and if the grounding switch is disconnected, controlling the grid-connected switch to close, so that the inverter operates in a grid-connected state; When the grid voltage state is abnormal, detect whether the grid-connected switch is disconnected. When the grid-connected switch is disconnected, detect whether the grounding switch is closed. If the grounding switch is closed, control the off-grid switch to be closed, so that the inverter operates in an off-grid state.

9. An inverter, characterized in that: The inverter includes an inverter circuit and the on-grid and off-grid switching device according to any one of claims 1 to 7.

10. The inverter according to claim 9, characterized in that: The inverter is used in a three-phase system, the off-grid switch is an off-grid relay, the grid-connected switch is a grid-connected relay, and the grounding switch is a grounding relay. The grid-connected switch is arranged between the AC side grid-connected port of the inverter and the power grid, the off-grid switch is arranged between the AC side off-grid port of the inverter and the load, and the grounding switch is arranged between the neutral line and the ground line of the inverter.

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