Photovoltaic inverter and control method

Abstract

According to the photovoltaic inverter and the control method, a switching tube is utilized to bypass a string switching unit, so that when the string switching unit is cut off, the string switching unit does not need to be impacted by large current and high voltage, a switching device which is small in size, low in cost and high in reliability can be selected for the string switching unit, and the reliability of the photovoltaic inverter is improved. And the switching tubes are strong in current resistance and voltage resistance, meet the requirement of photovoltaic string breaking, are also small in size, low in cost and high in reliability, and greatly reduce the production cost of the photovoltaic inverter. Besides, the string switch unit adopts a device with a dual-drive structure, so that transient power supply can be performed only when the driving switch is required to act, and power supply is stopped after the action is completed, thereby greatly reducing the power consumption of the inverter and saving energy.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic power generation, and particularly relates to a photovoltaic inverter and a control method thereof. Background Art

[0002] A photovoltaic inverter is a core device for adjusting and controlling photovoltaic modules and strings in a photovoltaic power generation system. In a photovoltaic power generation system with series-connected photovoltaic modules, there is direct current with large current and high voltage, resulting in the existing photovoltaic inverter string control switches having the problems of large volume, high cost, short service life, high power consumption, and low reliability. Especially when all existing mainstream photovoltaic inverters adopt carrier communication technology, the safety, reliability, and economy of existing photovoltaic inverters are at a relatively low level. Summary of the Invention

[0003] The present invention aims to at least solve one of the technical problems existing in the prior art. For this purpose, the present invention provides a photovoltaic inverter, which can solve the problems of high cost and energy waste of the photovoltaic inverter.

[0004] An embodiment of the present invention also provides a control method for a photovoltaic inverter.

[0005] The photovoltaic inverter according to the first aspect embodiment of the present invention includes:

[0006] A string switch unit having a first connection end, a second connection end, a third connection end, a first driving device, and a second driving device. A first set of connection contacts is formed between the first connection end and the second connection end, and a second set of connection contacts is formed between the first connection end and the third connection end. The first driving device is configured to connect the first set of connection contacts and disconnect the second set of connection contacts after being powered on, and the second driving device is configured to disconnect the first set of connection contacts and connect the second set of connection contacts after being powered on.

[0007] A switching tube having a controlled end, a first switch connection end, and a second switch connection end. The first switch connection end is connected to the first connection end, and the second switch connection end is connected to the second connection end.

[0008] A control unit is respectively connected to the first driving device, the second driving device, and the controlled end, and is configured to change the power-on states of the first driving device and the second driving device, and control the controlled end to adjust the on-off state between the first switch connection end and the second switch connection end.

[0009] The inverter unit has a first DC input terminal, a second DC input terminal, and a set of inverter AC output terminals. The first DC input terminal is connected to the second connection terminal. The second DC input terminal and the first connection terminal are jointly used to connect to the photovoltaic power generation unit. The set of inverter AC output terminals is used to output the inverted alternating current.

[0010] The photovoltaic inverter according to the embodiment of the present invention has at least the following beneficial effects:

[0011] The bypass of the string switch unit can be realized by using a switching tube, so that when the string switch unit is cut off, it does not need to withstand the impact of large current and high voltage. Therefore, the string switch unit can select switching devices with small volume, low cost and high reliability. The switching tube has strong current and voltage resistance, which meets the requirements of photovoltaic string breaking. Moreover, the switching tube also has small volume, low cost and high reliability, which greatly reduces the production cost of the photovoltaic inverter. In addition, the string switch unit adopts a device with a dual-drive structure, so that it can be powered briefly only when the switch action needs to be driven, and the power supply can be stopped after the action is completed, thereby greatly reducing the power consumption of the inverter and saving energy.

[0012] According to some embodiments of the present invention, the photovoltaic inverter further includes an AC switch unit connected to the control unit. The AC switch unit has a set of switch AC input terminals and a set of switch AC output terminals. The switch AC input terminal is connected to the set of inverter AC output terminals. The set of switch AC output terminals is used to output the inverted alternating current.

[0013] According to some embodiments of the present invention, the photovoltaic inverter further includes a string current sensor connected to the control unit. The string current sensor is used to detect the DC current input to the inverter unit.

[0014] According to some embodiments of the present invention, the photovoltaic inverter further includes a string voltage sensor connected to the control unit. The string voltage sensor is used to detect the DC voltage input to the inverter unit.

[0015] According to some embodiments of the present invention, the photovoltaic inverter further includes an input filtering unit. The input filtering unit is used to filter the direct current input to the inverter unit.

[0016] According to some embodiments of the present invention, the photovoltaic inverter further includes an output filtering unit. The output filtering unit is used to filter the alternating current output by the inverter unit.

[0017] According to some embodiments of the present invention, the photovoltaic inverter further includes an emergency stop device, and the second DC input terminal is connected to the photovoltaic power generation unit through the emergency stop device; the emergency stop device is connected to the control unit and is used to feedback the on / off state to the control unit.

[0018] According to some embodiments of the present invention, the string switch unit adopts a pulse-triggered control switch, and the first control coil in the pulse-triggered control switch serves as the first driving device, and the second control coil in the pulse-triggered control switch serves as the second driving device.

[0019] According to some embodiments of the present invention, the switching tube adopts IGBT.

[0020] According to some embodiments of the present invention, the photovoltaic inverter further includes a wireless communication module connected to the control unit.

[0021] According to some embodiments of the present invention, the photovoltaic inverter further includes a positioning module connected to the control unit.

[0022] According to some embodiments of the present invention, the photovoltaic inverter further includes a power storage unit, and the control unit is used to obtain a power supply from the power storage unit and / or the combined AC output terminals of the inverter unit and / or the first DC input terminal and the second DC input terminal of the inverter unit.

[0023] The photovoltaic inverter control method according to the second aspect embodiment of the present invention is applied to the photovoltaic inverter as described above; the photovoltaic inverter control method includes:

[0024] In response to the string turn-off instruction, control the first switch connection end and the second switch connection end of the switching tube to conduct.

[0025] After the conduction of the first switch connection end and the second switch connection end is completed, turn on the control power of the second driving device so that the first set of connection contacts is disconnected and the second set of connection contacts is connected.

[0026] Disconnect the control power of the second driving device.

[0027] Control the first switch connection end and the second switch connection end to disconnect.

[0028] The photovoltaic inverter control method according to the embodiment of the present invention has at least the following beneficial effects:

[0029] The bypass of the series string switch unit can be realized by using a switching tube, so that when the series string switch unit is cut off, it does not need to withstand the impact of large current and high voltage. As a result, the series string switch unit can select switching devices with small volume, low cost and high reliability. The switching tube has strong current and voltage resistance capabilities, meeting the requirements of photovoltaic string disconnection. Moreover, the switching tube also has a small volume, low cost and high reliability, greatly reducing the production cost of the photovoltaic inverter. In addition, the series string switch unit adopts a device with a dual-drive structure, so that it can be powered briefly only when the switch action needs to be driven, and the power supply can be stopped after the action is completed, thus greatly reducing the power consumption of the inverter and saving energy.

[0030] According to some embodiments of the present invention, the photovoltaic inverter further includes an AC switch unit, the AC switch unit has a switch AC input terminal group and a switch AC output terminal group, the switch AC input terminal is connected to the inverter AC output terminal group, and the switch AC output terminal group is used for outputting the inverted alternating current;

[0031] The photovoltaic inverter control method further includes:

[0032] When the AC power grid is powered off, a grid disconnection strategy is executed;

[0033] The grid disconnection strategy includes the following steps:

[0034] After the AC switch unit is disconnected, control the first switch connection end and the second switch connection end of the switching tube to conduct;

[0035] After the conduction of the first switch connection end and the second switch connection end is completed, connect the control power of the second driving device to make the first group of connection contacts disconnect and the second group of connection contacts connect;

[0036] Disconnect the control power of the second driving device;

[0037] Control the first switch connection end and the second switch connection end to disconnect.

[0038] According to some embodiments of the present invention, the photovoltaic inverter further includes an AC switch unit, the AC switch unit has a switch AC input terminal group and a switch AC output terminal group, the switch AC input terminal is connected to the inverter AC output terminal group, and the switch AC output terminal group is used for outputting the inverted alternating current;

[0039] The photovoltaic inverter control method further includes:

[0040] When the AC power grid resumes operation, a grid connection strategy is executed;

[0041] The grid connection strategy includes the following steps:

[0042] Control the first switch connection end and the second switch connection end of the switching tube to conduct;

[0043] After the first switch connection end and the second switch connection end are conducted, turn on the control power of the first driving device so that the first set of connection contacts are connected and the second set of connection contacts are disconnected;

[0044] After the first set of connection contacts are connected, control the first switch connection end and the second switch connection end of the switching tube to disconnect;

[0045] Control the AC switch unit to close.

[0046] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, wherein:

[0048] Figure 1 is the circuit diagram of the photovoltaic inverter according to the embodiment of the present invention;

[0049] Figure 2 is the system diagram of the photovoltaic inverter according to the embodiment of the present invention;

[0050] Figure 3 is the flowchart of the control method of the photovoltaic inverter according to the embodiment of the present invention.

[0051] Reference Signs:

[0052] String switch unit 100, string current sensor 110, string voltage sensor 120,

[0053] Switching tube 200,

[0054] Control unit 300,

[0055] Inverter unit 400,

[0056] AC switch unit 500,

[0057] Input filter unit 610, output filter unit 620,

[0058] Emergency stop device 700,

[0059] Wireless communication module 800,

[0060] Positioning module 900. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0061] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are only used to explain the present invention and should not be construed as limiting the present invention.

[0062] In the description of the present invention, if the first, second, etc. are described, it is only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features.

[0063] In the description of the present invention, it should be understood that for the orientation description, such as up, down, etc., the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention.

[0064] In the description of the present invention, it should be noted that unless otherwise clearly defined, words such as setting, installing, connecting, etc. should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above words in the present invention in combination with the specific content of the technical solution.

[0065] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the following described embodiments are some embodiments of the present invention, not all embodiments.

[0066] See Figure 1 , Figure 1 is the circuit diagram of the photovoltaic inverter according to the embodiment of the present invention. The photovoltaic inverter includes: a string switch unit 100, a switching tube 200, a control unit 300, and an inverter unit 400;

[0067] The string switch unit 100 has a first connection end, a second connection end, a third connection end, a first driving device, and a second driving device. A first set of connection contacts is formed between the first connection end and the second connection end, and a second set of connection contacts is formed between the first connection end and the third connection end. The first driving device is configured to connect the first set of connection contacts and disconnect the second set of connection contacts after being powered on, and the second driving device is configured to disconnect the first set of connection contacts and connect the second set of connection contacts after being powered on;

[0068] The switching tube 200 has a controlled end, a first switch connection end, and a second switch connection end; the first switch connection end is connected to the first connection end; the second switch connection end is connected to the second connection end;

[0069] The control unit 300 is respectively connected to the first driving device, the second driving device and the controlled end, and is used to change the energized state of the first driving device and the second driving device, and control the controlled end to adjust the on-off state between the first switch connection end and the second switch connection end;

[0070] The inverter unit 400 has a first DC input end, a second DC input end, and a set of inverter AC output ends. The first DC input end is connected to the second connection end, the second DC input end and the first connection end are jointly used to connect the photovoltaic power generation unit, and the set of inverter AC output ends is used to output the inverted alternating current.

[0071] The switching tube 200 has good voltage and current impact resistance capabilities. When it is necessary to cut off the circuit of the photovoltaic string, first control the switching tube 200 to bypass the first set of connection contacts of the string switching unit 100, and then disconnect the first set of connection contacts of the string switching unit 100 and close the second set of connection contacts. At this time, the voltage and current impacts that the string switching unit 100 needs to face will be much smaller, thus providing a basis for selecting a low-cost string switching unit 100. After the string switching unit 100 completes the adjustment of the connection contacts, the power supply of the string switching unit 100 can be disconnected, and then control the switching tube 200 to disconnect, that is, complete the circuit cutting of the entire photovoltaic string.

[0072] The photovoltaic inverter according to the embodiment of the present invention can bypass the string switching unit 100 by using the switching tube 200, so that when the string switching unit 100 is cut off, it does not need to withstand large current and high voltage impacts. Therefore, the string switching unit 100 can select switching devices with small volume, low cost and high reliability. The current and voltage resistance capabilities of the switching tube 200 are strong enough to meet the requirements of photovoltaic string breaking, and the switching tube 200 also has a small volume, low cost and high reliability. On the premise of selecting a lower-cost string switching unit 100, the production cost of the photovoltaic inverter can be greatly reduced. In addition, the string switching unit 100 adopts a device with a dual-drive structure, so that it can be powered only briefly when the switch action needs to be driven, and the power supply can be stopped after the action is completed, thus greatly reducing the power consumption of the inverter and saving energy. In addition, most of the photovoltaic inverters already in use on the market are set with a knob switch structure, which can only be turned off manually and needs to withstand large current and high voltage impacts, which will also result in a relatively high cost of the entire knob switch structure. The photovoltaic inverter in this embodiment can achieve automatic control, and because it does not need to face large current and high voltage impacts, the overall cost is greatly reduced, the size is also reduced, and the overall service life is greatly improved.

[0073] Reference Figure 1, in some embodiments, the PV inverter further includes an AC switch unit 500 connected to the control unit 300. The AC switch unit 500 has a switched AC input terminal group and a switched AC output terminal group. The switched AC input is connected to the inverted AC output terminal group, and the switched AC output terminal group is used to output the inverted alternating current. The AC switch unit 500 can cut off the AC loop of the PV inverter, which can improve the safety and convenience of use.

[0074] Reference Figure 2 , in some embodiments, the PV inverter further includes a string current sensor 110 connected to the control unit 300. The string current sensor 110 is used to detect the DC current input to the inverter unit. The string current sensor 110 can be used to detect the current of the photovoltaic power generation unit. When the photovoltaic power generation unit is a single photovoltaic string, the current detected by the string current sensor 110 is the string current of the photovoltaic string. When the photovoltaic string loop is disconnected, the string current sensor 110 cannot detect the current, so it can be determined that the current photovoltaic string has been disconnected.

[0075] Reference Figure 2 , in some embodiments, the PV inverter further includes a string voltage sensor 120 connected to the control unit 300. The string voltage sensor 120 is used to detect the DC voltage input to the inverter unit. The string voltage sensor 120 can be used to detect the voltage of the photovoltaic power generation unit. When the photovoltaic power generation unit is a single photovoltaic string, the voltage detected by the string voltage sensor 120 is the string voltage of the photovoltaic string. When the photovoltaic string loop is disconnected, since each photovoltaic module in the photovoltaic string is not disconnected, the string voltage sensor 120 can still detect the string voltage of the string. When the photovoltaic module is disconnected, the string voltage sensor 120 can no longer detect the voltage.

[0076] Reference Figure 1 , in some embodiments, the PV inverter further includes an input filter unit 610. The input filter unit 610 is used to filter the direct current input to the inverter unit 400. The input filter unit 610 can filter the DC side and improve the quality of power conversion.

[0077] Reference Figure 1 , in some embodiments, the PV inverter further includes an output filter unit 620. The output filter unit 620 is used to filter the alternating current output by the inverter unit 400. The output filter unit 620 can filter the AC side and improve the quality of power output.

[0078] Reference Figure 1, in some embodiments, the photovoltaic inverter further includes an emergency stop device 700. The second DC input terminal is connected to the photovoltaic power generation unit through the emergency stop device 700; the emergency stop device 700 is connected to the control unit 300 and is used to feedback the on / off state to the control unit 300. The emergency stop device 700 can achieve the emergency cut-off of the photovoltaic string, which is suitable for directly performing emergency protection locally and quickly in case of emergency. The emergency stop device 700 can use an emergency stop switch or other switch components with manual cut-off function. At the same time, the emergency stop device 700 can feedback the on / off state signal to the emergency stop device 700, so that when the emergency stop device 700 is disconnected, the control unit 300 can send a component disconnection instruction to each photovoltaic component in the photovoltaic string, so that each photovoltaic component in the photovoltaic string can be completely disconnected, avoiding the existence of high voltage in the photovoltaic string and solving some safety problems caused by high voltage.

[0079] Reference Figure 1 , in some embodiments, the string switch unit 100 adopts a pulse-triggered control switch. The first control coil in the pulse-triggered control switch is used as the first driving device, and the second control coil in the pulse-triggered control switch is used as the second driving device. By selecting a pulse-triggered control switch with two control coils, the pulse-triggered control switch only switches to different connection contacts when different coils are energized, and can be well applied to the photovoltaic inverter in the embodiments of the present invention.

[0080] Reference Figure 1 , in some embodiments, the switching transistor 200 adopts an IGBT. The gate of the IGBT is connected to the control unit 300, and the source and drain are respectively connected to the first connection end and the second connection end. When the control unit 300 outputs a control voltage to the gate of the IGBT, the IGBT conducts, making the source and drain connected, realizing the bypass of the first set of connection contacts. At this time, the control unit 300 can switch the energized state of the control coil, so that the first set of connection contacts is disconnected and the second set of connection contacts is connected.

[0081] Reference Figure 2 , in some embodiments, the photovoltaic inverter further includes a wireless communication module 800 connected to the control unit 300. The photovoltaic inverter needs to perform data interaction with the photovoltaic component side to obtain the operation data of each photovoltaic component in the photovoltaic string. Using the wireless communication module 800 can reduce the complexity of wiring to a certain extent compared with the wired communication module, and reduce the construction labor cost. Moreover, after the photovoltaic string is cut off at the photovoltaic inverter end, carrier communication (a traditional solution that does not require additional wiring) cannot be used, while selecting the wireless communication module 800 can avoid this problem.

[0082] Reference Figure 2, in some embodiments, the photovoltaic inverter further includes a positioning module 900 connected to the control unit 300. The positioning module 900 can achieve real-time positioning of the photovoltaic inverter. On the one hand, it can facilitate subsequent real-time monitoring of the operation of the photovoltaic inverter. On the other hand, it can also meet the requirements of asset management based on the positioning module 900. In some embodiments, the positioning module 900 can adopt a Beidou positioning module 900, a GPS positioning module 900, or other single-core positioning modules 900, as well as a fusion positioning module 900.

[0083] In some embodiments, the photovoltaic inverter further includes a power storage unit. The control unit 300 is configured to obtain a power supply from the power storage unit and / or the AC output terminal group of the inverter unit 400 and / or the first DC input terminal and the second DC input terminal of the inverter unit 400. Redundant power supply using the power storage unit, the AC side, and the DC side can, to a great extent, ensure the stability of the operation of the control unit 300. Even when the DC side and the AC side are powered off simultaneously, it still has the ability to work and complete the disconnection of the photovoltaic string, thereby reducing property losses in extreme cases. It can be understood that in some embodiments, direct current can be taken from the connection end between the string switch unit 100 and the photovoltaic string, so that there is still a direct current source when the string switch unit 100 is disconnected; similarly, alternating current can be taken from the output filter unit 620 side, so that there is still an alternating current source after the AC switch unit 500 is disconnected.

[0084] See Figure 3 as shown Figure 3 The flowchart of the photovoltaic inverter control method provided by an embodiment of the present invention. The photovoltaic inverter control method includes but is not limited to the following steps:

[0085] In response to the string shutdown instruction, control the first switch connection end and the second switch connection end of the switch tube 200 to conduct;

[0086] After the conduction of the first switch connection end and the second switch connection end is completed, turn on the control power of the second driving device so that the first set of connection contacts is disconnected and the second set of connection contacts is connected;

[0087] Disconnect the control power of the second driving device;

[0088] Control the first switch connection end and the second switch connection end to disconnect.

[0089] The switching transistor 200 has good capabilities of withstanding voltage and current surges. When it is necessary to cut off the circuit of the photovoltaic string, first control the switching transistor 200 to bypass the first set of connection contacts of the string switching unit 100, and then disconnect the first set of connection contacts of the string switching unit 100 and close the second set of connection contacts. At this time, the voltage and current surges that the string switching unit 100 needs to face will be much smaller, thus laying a foundation for selecting a low-cost string switching unit 100. After the string switching unit 100 completes the adjustment of the connection contacts, the power supply of the string switching unit 100 can be disconnected, and then control the switching transistor 200 to disconnect, that is, complete the circuit cutting of the entire photovoltaic string.

[0090] The photovoltaic inverter control method according to the embodiment of the present invention utilizes that the switching transistor 200 can bypass the string switching unit 100, so that when the string switching unit 100 is cut off, it does not need to withstand the impact of large current and high voltage. As a result, the string switching unit 100 can select switching devices with small volume, low cost, and high reliability. And the switching transistor 200 has strong capabilities of withstanding current and voltage, meeting the requirements of photovoltaic string disconnection. Moreover, the switching transistor 200 also has small volume, low cost, and high reliability. On the premise of selecting a lower-cost string switching unit 100, the production cost of the photovoltaic inverter can be greatly reduced. In addition, the string switching unit 100 adopts a device with a dual-drive structure, so that it can be powered only briefly when the switch action needs to be driven, and stop power supply after the action is completed, thus greatly reducing the power consumption of the inverter and saving energy. In addition, most of the photovoltaic inverters already in use on the market are equipped with a knob-type switch structure, which can only be turned off manually and needs to withstand the impact of large current and high voltage, which will also result in a relatively high cost of the entire knob-type switch structure. While the photovoltaic inverter in this embodiment can achieve automatic control, and because it does not need to face the impact of large current and high voltage, the overall cost is greatly reduced, the size is also reduced, and the overall service life is greatly improved.

[0091] In some embodiments, the photovoltaic inverter further includes an AC switch unit 500. The AC switch unit 500 has a switch AC input terminal group and a switch AC output terminal group. The switch AC input terminal is connected to the inverter AC output terminal group, and the switch AC output terminal group is used to output the inverted alternating current.

[0092] The photovoltaic inverter control method further includes:

[0093] When the AC power grid is powered off, execute a grid disconnection strategy;

[0094] The grid disconnection strategy includes the following steps:

[0095] Wait for the AC switch unit 500 to disconnect, and control the first switch connection end and the second switch connection end of the switch tube 200 to conduct;

[0096] Wait for the conduction of the first switch connection end and the second switch connection end to be completed, and turn on the control power of the second driving device so that the first set of connection contacts is disconnected and the second set of connection contacts is connected;

[0097] Turn off the control power of the second driving device;

[0098] Control the first switch connection end and the second switch connection end to disconnect.

[0099] When the AC power grid is powered off, the PV power generation system needs to be disconnected from the grid. In this embodiment, a strategy of first cutting off the AC side and then cutting off the DC side is adopted. When the AC side power grid is powered off, first control the AC switch unit 500 to disconnect, that is, the cutting off of the AC side is completed; then control the switch tube 200 to bypass the first set of connection contacts, and control the first set of connection contacts and the second set of connection contacts of the string switch unit 100 to complete the switching of the on-off state. After that, control the switch tube 200 to disconnect to complete the shutdown of the DC side. It should be noted that for the string switch unit 100, only short-time power supply is required during the state switching, so that the power consumption of the string switch unit 100 during operation can be greatly reduced. In addition, it should be noted that if there is a component breaking ability in the PV modules in the PV string connected to the PV inverter, after the string switch unit 100 disconnects the circuit, the control unit 300 will send a disconnection instruction to each PV module to separate each PV module from the PV string to avoid the problem of still having a high voltage after the string switch unit 100 is disconnected. At the same time, after the PV module is disconnected or bypassed, the voltage of the PV string will change. The string voltage sensor 120 can detect this change to determine whether the PV module side is completely disconnected.

[0100] In some embodiments, the PV inverter further includes an AC switch unit 500. The AC switch unit 500 has a switch AC input terminal group and a switch AC output terminal group. The switch AC input terminal is connected to the inverter AC output terminal group, and the switch AC output terminal group is used to output the inverted AC power;

[0101] The PV inverter control method further includes:

[0102] When the AC power grid resumes operation, execute the grid connection strategy;

[0103] The grid connection strategy includes the following steps:

[0104] Control the first switch connection end and the second switch connection end of the switch tube 200 to conduct;

[0105] After the first switch connection terminal and the second switch connection terminal are turned on, the control power of the first driving device is turned on so that the first set of connection contacts are turned on and the second set of connection contacts are turned off;

[0106] After the first set of connection contacts are turned on, the first switch connection terminal and the second switch connection terminal of the control switch tube 200 are turned off;

[0107] Control the AC switch unit 500 to close.

[0108] When the AC power grid resumes operation, the photovoltaic power generation system needs to be re-connected to the grid. In this embodiment, a strategy of first closing the DC side and then accessing the AC side is adopted. After the AC power grid resumes operation, first, the switch tube 200 is controlled to bypass the first set of connection contacts. After the bypass is completed, the control is then performed to complete the switching of the on-off states of the first set of connection contacts and the second set of connection contacts of the string switch unit 100. And after the first set of connection contacts are turned on, the AC switch unit 500 is then controlled to close, thus completing the entire grid connection process. It should be noted that for the string switch unit 100, only short-term power supply is required during the state switching, so that the power consumption of the string switch unit 100 during operation can be greatly reduced. In addition, it should be noted that if there is a component breaking capacity in the photovoltaic modules connected to the photovoltaic inverter, before the string switch unit 100 closes the loop, the control unit 300 will first send a closing instruction to each photovoltaic module to connect each photovoltaic module to the photovoltaic string, and then complete the closing of the string switch unit 100, and then control the AC switch unit 500 to close. At the same time, after the photovoltaic module is re-connected to the photovoltaic string from the disconnected or bypassed state, the voltage of the photovoltaic string will change. The string voltage sensor 120 can detect this change to determine whether the access on the photovoltaic module side is completed.

[0109] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A photovoltaic inverter, characterized in that, Comprising: A string switch unit having a first connection end, a second connection end, a third connection end, a first driving device, and a second driving device. A first set of connection contacts is formed between the first connection end and the second connection end, and a second set of connection contacts is formed between the first connection end and the third connection end. The first driving device is configured to connect the first set of connection contacts and disconnect the second set of connection contacts when powered on, and the second driving device is configured to disconnect the first set of connection contacts and connect the second set of connection contacts when powered on. A switching tube having a controlled end, a first switch connection end, and a second switch connection end. The first switch connection end is connected to the first connection end, and the second switch connection end is connected to the second connection end. A control unit is respectively connected to the first driving device, the second driving device, and the controlled end, and is configured to change the power-on states of the first driving device and the second driving device, and control the controlled end to adjust the on-off state between the first switch connection end and the second switch connection end. An inversion unit having a first DC input end, a second DC input end, and a set of inverted AC output ends. The first DC input end is connected to the second connection end, and the second DC input end and the first connection end are jointly used to connect a photovoltaic power generation unit, and the set of inverted AC output ends is configured to output the inverted alternating current.

2. The photovoltaic inverter according to claim 1, wherein The photovoltaic inverter further includes an AC switch unit connected to the control unit. The AC switch unit has a set of switch AC input ends and a set of switch AC output ends. The switch AC input end is connected to the set of inverted AC output ends, and the set of switch AC output ends is configured to output the inverted alternating current.

3. The photovoltaic inverter according to claim 1, wherein The photovoltaic inverter further includes a string current sensor connected to the control unit, and the string current sensor is configured to detect the DC current input to the inversion unit.

4. The PV inverter according to claim 1, wherein The photovoltaic inverter further includes a string voltage sensor connected to the control unit, and the string voltage sensor is configured to detect the DC voltage input to the inversion unit.

5. The photovoltaic inverter according to claim 1, characterized in that, The photovoltaic inverter further includes an emergency stop device. The second DC input end is connected to the photovoltaic power generation unit through the emergency stop device. The emergency stop device is connected to the control unit and is configured to feedback the on-off state to the control unit.

6. The photovoltaic inverter according to claim 1, characterized in that, The string switch unit adopts a pulse-triggered control switch. The first control coil in the pulse-triggered control switch serves as the first driving device, and the second control coil in the pulse-triggered control switch serves as the second driving device.

7. The photovoltaic inverter according to claim 1, characterized in that, The photovoltaic inverter further includes a wireless communication module connected to the control unit.

8. The photovoltaic inverter according to claim 1, wherein, The photovoltaic inverter further includes a positioning module connected to the control unit.

9. The PV inverter according to claim 1, characterized in that, The photovoltaic inverter further includes a power storage unit, and the control unit is configured to obtain a power supply from the power storage unit and / or the set of inverted AC output ends of the inversion unit and / or the first DC input end and the second DC input end of the inversion unit.

10. A photovoltaic inverter control method, characterized in that, Applied to the photovoltaic inverter according to any one of claims 1 to 9. The photovoltaic inverter control method includes: In response to the string cut-off instruction, control the first switch connection end and the second switch connection end of the switching tube to conduct; After the conduction of the first switch connection end and the second switch connection end is completed, connect the control power of the second driving device so that the first set of connection contacts is disconnected and the second set of connection contacts is connected; Disconnect the control power of the second driving device; Control the first switch connection end and the second switch connection end to disconnect.

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