CN116388541A

CN116388541A - Control method of power converter and grid-connected inverter

Info

Publication number: CN116388541A
Application number: CN202310215860.6A
Authority: CN
Inventors: 乐胜康; 李霄飞; 王朝; 刘银南
Original assignee: China Datang Group Technology And Economic Research Institute Co ltd; Huawei Digital Power Technologies Co Ltd
Current assignee: China Datang Group Technology And Economic Research Institute Co ltd; Huawei Digital Power Technologies Co Ltd
Priority date: 2023-02-24
Filing date: 2023-02-24
Publication date: 2023-07-04

Abstract

The application discloses a control method of a power converter and a grid-connected inverter, wherein the grid-connected inverter comprises a controller, a circuit board, a first power module and a second power module which are arranged on the circuit board. The first power module performs power conversion on the input direct current power. The second power module receives the direct current power from the first power module. The controller can acquire parameters of the first or second power module, and can control at least one switching tube of the first or second power module to work at a first frequency before the grid-connected inverter performs IV scanning; and when the grid-connected inverter performs IV scanning, controlling at least one switching tube of the first or second power module to work at a second frequency so that the temperature of the first or second power module during IV scanning is less than or equal to the temperature before IV scanning. The method and the device can reduce the temperature of the power module during IV scanning, enable the temperature of the power module to meet the thermal stress requirement, and improve the stability of the grid-connected inverter.

Description

Control method of power converter and grid-connected inverter

Technical Field

The application relates to the technical field of power electronics and new energy power supply, in particular to a control method of a power converter and a grid-connected inverter.

Background

In the process of carrying out IV curve scanning on the photovoltaic module, the photovoltaic module currently carrying out IV curve scanning is in an IV curve scanning mode, namely the output voltage is scanned from open circuit voltage to short circuit voltage by the connected direct current-direct current conversion circuit. In the whole IV curve scanning process, the duty ratio of the direct current-direct current conversion circuit is changed rapidly from small to large to small in a short time, so that the loss of a switching tube of the conversion circuit is increased, the heating of the switching tube is serious, and the reliability of a photovoltaic system is further affected.

Disclosure of Invention

The embodiment of the application provides a control method of a power converter and a grid-connected inverter. By adopting the control method of the power converter and the grid-connected inverter, the temperature of the power module can be reduced during IV scanning, so that the temperature of the power module can meet the thermal stress requirement, and the stability of the grid-connected inverter is improved.

In a first aspect, the present application provides a grid-tied inverter that may include a controller, a first power module, a second power module, and a circuit board. The first power module and the second power module can be arranged on the circuit board, and the output end of the first power module is connected with the second power module. The first power module may include at least one switching tube for connecting outputs of the plurality of photovoltaic modules to power convert the dc power input to the first power module. The second power module may include at least one switching tube for receiving the direct current power from the first power module. The controller may obtain parameters of the first power module or the second power module. For example, the parameter may include at least one of an input voltage, an input current, an output voltage, an output current, an input power, and an output power of the first power module or the second power module. The controller may control at least one switching tube of the first power module or the second power module to operate at a first frequency before the grid-connected inverter performs IV scanning. The controller can also control at least one switching tube of the first power module or the second power module to work at a second frequency when the grid-connected inverter performs IV scanning, so that the temperature of the first power module or the second power module during IV scanning is smaller than or equal to the temperature before IV scanning. By adopting the grid-connected inverter, the power module is subjected to variable frequency control before and during IV scanning, so that the temperature of the power module during IV scanning is reduced, the temperature of the power module can meet the thermal stress requirement, and the stability of the grid-connected inverter is improved.

As an alternative implementation, the second switching frequency is smaller than the first switching frequency. By reducing the switching frequency of the power module during IV scanning, the temperature of the power module during IV scanning can be made less than or equal to the temperature prior to IV scanning.

As an alternative implementation manner, the grid-connected inverter may further include a dc conversion circuit and an inverter circuit, the dc conversion circuit may include at least one switching tube of the first power module, the inverter circuit may include at least one switching tube of the second power module, an input of the dc conversion circuit is connected to outputs of the plurality of photovoltaic modules, and an output of the dc conversion circuit is used to connect to the inverter circuit, and the dc converted by the dc conversion circuit is converted into ac required by a power grid or a load by the inverter circuit.

As an alternative implementation, the at least one switching tube of the first power module may include a first switching tube, and the dc conversion circuit may include an inductor, a diode, and the first switching tube. The first end of the inductor is electrically connected with the anode of the diode, the second end of the inductor is electrically connected with the first end of the first capacitor and the output of the photovoltaic modules, the second end of the first capacitor is electrically connected with the output of the photovoltaic modules and the first switch tube, the cathode of the diode is electrically connected with the first end of the second capacitor and the second power module, and the second end of the second capacitor is electrically connected with the second power module. The controller may also be configured to: before the grid-connected inverter performs IV scanning, the first switching tube is controlled to work at a first frequency. And when the grid-connected inverter performs IV scanning, controlling the first switching tube to work at a second frequency, so that the temperature of the first power module during IV scanning is smaller than or equal to the temperature before IV scanning. By adopting the control mode, namely, the first power module is subjected to variable frequency control before and during IV scanning, the temperature of the first power module during IV scanning is reduced, and thus the temperature of the first power module can meet the thermal stress requirement.

As an alternative implementation, the at least one switching tube of the second power module may include a first switching tube, a second switching tube, a third switching tube and a fourth switching tube. The inverter circuit may include a first diode, a second diode, the first switching tube, the second switching tube, the third switching tube, and the fourth switching tube. The first switching tube is electrically connected between the first output end of the direct current conversion circuit and the second switching tube. The second switching tube is electrically connected between the first switching tube and the third switching tube. The fourth switching tube is electrically connected between the third switching tube and the second output end of the direct current conversion circuit, and a node between the first switching tube and the second switching tube is electrically connected with the cathode of the first diode. The anode of the first diode is electrically connected to the cathode of the second diode, and the anode of the second diode is electrically connected to the node between the third switching tube and the fourth switching tube. The controller may also be configured to: before the grid-connected inverter performs IV scanning, controlling a first switching tube, a second switching tube, a third switching tube and a fourth switching tube to work at a first frequency; and when the grid-connected inverter performs IV scanning, controlling the first switching tube, the second switching tube, the third switching tube and the fourth switching tube to work at a second frequency, so that the temperature of the second power module during IV scanning is smaller than or equal to the temperature before IV scanning. The temperature of the second power module in IV scanning is reduced by performing variable frequency control on the second power module before IV scanning and during IV scanning, so that the temperature of the second power module can meet the thermal stress requirement.

As an optional implementation manner, the controller may be further configured to obtain a mapping relationship between a frequency and a temperature of at least one switching tube of the first power module or the second power module according to a parameter of the first power module or the second power module, and control the switching frequency of the at least one switching tube of the first power module or the second power module according to the mapping relationship when the grid-connected inverter performs IV scanning, so that the temperature of the first power module or the second power module during IV scanning is less than or equal to the temperature before IV scanning, thereby enabling the temperature of the first power module or the second power module to meet a thermal stress requirement, and improving stability of the grid-connected inverter.

As an alternative implementation, the temperature of the first power module may include the temperature of the interior and surface of the first power module. The temperature of the second power module may include the temperature of the interior and the surface of the second power module.

In a second aspect, the present application further provides a control method of a power converter, where the power converter may include a first power module and a second power module, an output end of the first power module is connected to the second power module, and the first power module includes at least one switching tube, and is configured to connect outputs of a plurality of photovoltaic modules, so as to perform power conversion on direct current power input to the first power module. The second power module comprises at least one switch tube and is used for receiving direct current power from the first power module; the control method comprises the following steps: parameters of the first power module or the second power module are obtained, wherein the parameters can comprise at least one of input voltage, input current, output voltage, output current, input power and output power of the first power module or the second power module. Before the power converter performs IV scanning, controlling at least one switching tube of the first power module or the second power module to work at a first frequency; when the power converter performs IV scanning, at least one switching tube of the first power module or the second power module is controlled to work at a second frequency, so that the temperature of the first power module or the second power module during IV scanning is less than or equal to the temperature before IV scanning. According to the control method, the first power module or the second power module is subjected to variable frequency control before IV scanning and during IV scanning, so that the temperature of the first power module or the second power module during IV scanning is reduced, the temperature of the first power module and the temperature of the second power module can meet the thermal stress requirement, and the stability of the grid-connected inverter is improved.

As an alternative implementation, the at least one switching tube of the first power module may include a first switching tube, and the dc conversion circuit may include an inductor, a diode, and the first switching tube. The first end of the inductor is electrically connected with the anode of the diode, the second end of the inductor is electrically connected with the first end of the first capacitor and the output of the photovoltaic modules, the second end of the first capacitor is electrically connected with the output of the photovoltaic modules and the first switch tube, the cathode of the diode is electrically connected with the first end of the second capacitor and the second power module, and the second end of the second capacitor is electrically connected with the second power module. The control method further comprises the following steps: before the grid-connected inverter performs IV scanning, the first switching tube is controlled to work at a first frequency. And when the grid-connected inverter performs IV scanning, controlling the first switching tube to work at a second frequency, so that the temperature of the first power module during IV scanning is smaller than or equal to the temperature before IV scanning. By adopting the control mode, namely, the first power module is subjected to variable frequency control before and during IV scanning, the temperature of the first power module during IV scanning is reduced, and thus the temperature of the first power module can meet the thermal stress requirement.

As an alternative implementation, the at least one switching tube of the second power module may include a first switching tube, a second switching tube, a third switching tube and a fourth switching tube. The inverter circuit may include a first diode, a second diode, the first switching tube, the second switching tube, the third switching tube, and the fourth switching tube. The first switching tube is electrically connected between the first output end of the direct current conversion circuit and the second switching tube. The second switching tube is electrically connected between the first switching tube and the third switching tube. The fourth switching tube is electrically connected between the third switching tube and the second output end of the direct current conversion circuit, and a node between the first switching tube and the second switching tube is electrically connected with the cathode of the first diode. The anode of the first diode is electrically connected to the cathode of the second diode, and the anode of the second diode is electrically connected to the node between the third switching tube and the fourth switching tube. The control method further comprises the following steps: before the grid-connected inverter performs IV scanning, controlling a first switching tube, a second switching tube, a third switching tube and a fourth switching tube to work at a first frequency; and when the grid-connected inverter performs IV scanning, controlling the first switching tube, the second switching tube, the third switching tube and the fourth switching tube to work at a second frequency, so that the temperature of the second power module during IV scanning is smaller than or equal to the temperature before IV scanning. The temperature of the second power module in IV scanning is reduced by performing variable frequency control on the second power module before IV scanning and during IV scanning, so that the temperature of the second power module can meet the thermal stress requirement.

As an alternative implementation manner, the control method further includes: the method comprises the steps of obtaining a mapping relation between the frequency and the temperature of at least one switching tube of a first power module or a second power module according to parameters of the first power module or the second power module, controlling the switching frequency of at least one switching tube of the first power module or the second power module according to the mapping relation when the grid-connected inverter performs IV scanning, and enabling the temperature of the first power module or the second power module during IV scanning to be smaller than or equal to the temperature before IV scanning, so that the temperature of the first power module or the second power module can meet the thermal stress requirement, and stability of the grid-connected inverter is improved.

According to the control method of the power converter and the grid-connected inverter, in the IV curve scanning process of the photovoltaic module, the switching frequency of the first power module or the second power module is regulated, so that the temperature of the first power module or the second power module in IV scanning is reduced, the temperature of the first power module and the temperature of the second power module can meet the thermal stress requirement, and the reliability of a photovoltaic power generation system is improved.

Drawings

Fig. 1 is an IV curve scan of a photovoltaic module in a healthy state.

Fig. 2 is a schematic diagram of a photovoltaic power generation system according to an embodiment of the present application.

Fig. 3 is another schematic diagram of the photovoltaic power generation system provided in the embodiment of the present application.

Fig. 4 is a schematic structural diagram of a grid-connected inverter according to an embodiment of the present application.

Fig. 5 is another schematic diagram of a grid-connected inverter according to an embodiment of the present disclosure.

Fig. 6 is a schematic structural diagram of an inverter circuit according to an embodiment of the present application.

Fig. 7 is a flowchart illustrating a control method of a power converter according to an embodiment of the present application.

Fig. 8 is a schematic structural diagram of a controller according to an embodiment of the present application.

Fig. 9 is another schematic structural diagram of a controller according to an embodiment of the present application.

Detailed Description

For the purposes of making the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.

It will be understood that when an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. When an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.

With the shortage of traditional energy sources and the increase of global pollution, pollution-free plot energy sources, such as wind power generation and solar power generation, which are also called photovoltaic power generation, are increasingly used at present. Photovoltaic power generation is a technology for converting light energy into electric energy by utilizing the photovoltaic effect of a semiconductor interface, and has been rapidly developed. The photovoltaic module is used as a core component in the photovoltaic power generation system and can be used for converting the light energy into electric energy, so that the healthy state of the photovoltaic module can directly influence the generated energy of the photovoltaic power generation system. When environmental factors such as temperature and illumination intensity are fixed, an output current of the photovoltaic module changes with a change in output voltage, and may be drawn as a current-voltage (IV) curve (hereinafter simply referred to as "IV curve").

The IV curve of a healthy photovoltaic module is parabolic, as shown in fig. 1, and its IV curve is parabolic. By controlling the output voltage of the photovoltaic module to scan from the open circuit voltage to the short circuit voltage, the curve relationship between the output current and the output voltage of the photovoltaic module can be drawn, and the technology is the IV curve scanning technology of the photovoltaic module. If the photovoltaic module is damaged or is blocked, the IV curve is distorted. Therefore, the health state of the photovoltaic module can be diagnosed through the IV curve, and a basis is provided for the operation and maintenance of the photovoltaic module. Therefore, in the process of supplying power to the power grid through the photovoltaic power generation system, IV curves of the respective photovoltaic modules need to be acquired. Among them, the process of acquiring an IV curve of a photovoltaic module is generally called an IV curve scanning process. In the IV curve scanning process, the duty ratio of the DC-DC converter can change rapidly from small to large to small in a short time, so that the loss of a switching tube of the converter is increased, the heating of the switching tube is serious, and the reliability of a photovoltaic power generation system is affected.

In view of the above problems, the embodiments of the present application provide a control method for a power converter, which may adjust the switching frequency of a power module in a grid-connected inverter before and during IV curve scanning of a photovoltaic module, that is, by reducing the switching frequency of the power module, the loss of the power module may be reduced, the temperature of the power module during IV curve scanning may be reduced, and further the reliability of a photovoltaic power generation system may be improved. The embodiment of the application can also provide a corresponding grid-connected inverter. The following will each explain in detail by means of specific examples.

The application scene applicable to the embodiment of the application comprises: large photovoltaic power station application scenes, medium and small distributed power station application scenes, household photovoltaic power generation systems and the like. The output of the power converter may be connected to the transformer via a cable or directly to the ac grid.

Referring to fig. 2, fig. 2 is a schematic structural diagram of a photovoltaic power generation system 1000 provided in the present application.

As shown in fig. 2, the photovoltaic power generation system 1000 may include a photovoltaic module 200, a grid-tied inverter 100, and an ac power grid 300. It will be appreciated that in this embodiment, the grid-tied inverter 100 may be connected between the photovoltaic module 200 and the ac grid 300.

In a specific implementation process, an input end of the grid-connected inverter 100 may be connected to the photovoltaic module 200, and an output end of the grid-connected inverter 100 may be connected to the ac power grid 300. Alternatively, the number of the photovoltaic modules 200 connected to the input of the grid-connected inverter 100 may be plural, that is, the plurality of photovoltaic modules 200 may be connected in series and/or in parallel and then connected to the grid-connected inverter 100.

It is understood that in other embodiments of the present application, the output of grid-tie inverter 100 may also be connected to a household appliance.

In this embodiment, the photovoltaic module 200 may be used to convert light energy into electrical energy. Grid-tied inverter 100 may be used to control the output power of a connected plurality of photovoltaic modules 200. For example, the grid-connected inverter 100 may convert dc power generated by the plurality of photovoltaic modules 200 connected to the input end thereof into dc power, and invert the dc power into ac power, so as to supply power to the ac power grid 300 or various loads (such as household devices) and other electric devices.

Referring to fig. 3, fig. 3 is a schematic diagram of a grid-connected inverter 100 according to an embodiment of the present application.

As shown in fig. 3, in one photovoltaic power scenario, grid-tied inverter 100 may include a power converter 40 and a controller 30. The controller 30 is connected to the power converter 40, and the controller 30 can control the power converter 40. In this embodiment, the power converter 30 may include a direct current conversion circuit 10 and an inverter circuit 20.

The input end of the dc conversion circuit 10 is electrically connected to the photovoltaic module 200, the output end of the dc conversion circuit 10 is electrically connected to the input end of the inverter circuit 20, and the output end of the inverter circuit 20 may be electrically connected to the ac power grid 300. Alternatively, the number of the photovoltaic modules 200 connected to the input terminal of the dc conversion circuit 10 may be plural, and the plurality of photovoltaic modules 200 may be connected in series and/or in parallel to the dc conversion circuit 10.

After the grid-connected inverter 100 starts to operate, the dc conversion circuit 10 may convert the dc power generated by the photovoltaic module 200 connected to the input terminal thereof into dc power with a voltage of a preset value, and output the converted dc power to the inverter circuit 20.

It will be appreciated that the dc conversion circuit 10 in the embodiment of the present application may be, but not limited to, implemented by using a Boost circuit, and specifically may be implemented by using a Boost circuit. The inverter circuit 20 may invert the dc power output by the dc conversion circuit 10 into ac power, so as to supply power to the ac power grid 300 or ac loads (such as household devices) and other electric devices.

In the process of supplying power to the electric equipment by the grid-connected inverter 100, IV curve scanning needs to be performed on the photovoltaic module 200. The grid-connected inverter 100 may sequentially perform IV curve scanning by controlling the dc conversion circuit 10 to make the output voltage of the photovoltaic module 200 be a plurality of scan voltage values (i.e., all scan voltage values required for forming a complete IV curve), and respectively obtain a plurality of output current values of the photovoltaic module 200 when the output voltage of the photovoltaic module 200 is a plurality of scan voltage values during the IV curve scanning.

It will be appreciated that in some embodiments, the controller 30 is connected to the dc conversion circuit 10. The controller 30 may obtain the performance parameters of the dc conversion circuit 10. The controller 30 may be configured to control the dc conversion circuit 10 to supply power to the ac power grid 300 by using the photovoltaic system in which the grid-connected inverter 100 is located after the grid-connected inverter 100 starts to operate. The controller 30 may also perform IV curve scanning of the photovoltaic module 200 by controlling the dc conversion circuit 10 after receiving the IV scanning command.

In a specific implementation, the controller 30 may also be connected to an upper computer. After the upper computer issues the IV curve scan command, the controller 30 may receive the scan command. The controller 30 controls the input voltage of the dc conversion circuit 10 so that the output voltage of the photovoltaic module 200 has a plurality of scan voltage values by transmitting a control signal (e.g., a pulse width modulated wave) to at least one switching tube in the dc conversion circuit 10. For example, the controller 30 may adjust the input voltage of the dc conversion circuit 10 by controlling the on-time of at least one switching tube in the dc conversion circuit 10.

It will be appreciated that in some embodiments, the dc conversion circuit 10 may include at least one controllable switching tube for connecting the outputs of the plurality of photovoltaic modules to power convert the dc power input to the dc conversion circuit 10. In some embodiments, at least one controllable switch of the dc conversion circuit 10 may be encapsulated in a certain functional combination to form a module, i.e. the at least one controllable switch of the dc conversion circuit 10 may be encapsulated in a housing to form the first power module 101 shown in fig. 4. It will be appreciated that in some embodiments, the inverter circuit 20 may include at least one controllable switching tube for receiving dc power from the dc conversion circuit 10. At least one controllable switching tube of the inverter circuit 20 may be encapsulated again according to a certain functional combination to form a module, that is, at least one controllable switching tube of the inverter circuit 20 may be encapsulated in another housing to form the second power module 102 shown in fig. 4.

As shown in fig. 4, the first power module 101 and the second power module 102 may each be mounted on a circuit board 103 of the grid-connected inverter 100. Wherein the first power module 101 may comprise at least one switching tube and the second power module 102 may comprise at least one switching tube. An output of the first power module 101 may be connected to the second power module 102. It will be appreciated that in this embodiment, other electronic devices (such as a capacitor, an inductor, etc.) in the dc conversion circuit 10 may also be mounted on the circuit board 103, i.e. the capacitor, the inductor, etc. may be connected to at least one switching tube of the first power module 101. Other electronic devices (e.g., diodes) in the inverter circuit 10 may also be mounted to the circuit board 103.

The first power module 101 in this embodiment may include at least one switching tube for connecting the outputs of the plurality of photovoltaic modules 200 to perform power conversion on the dc power input to the first power module 101.

The second power module 102 in this embodiment may include at least one switching tube for receiving the dc power from the first power module 101. The second power module 102 may convert the received dc power to ac power for ac power required by the ac power grid 300 or the load.

The controller 30 in this embodiment may be connected to the first power module 101 and the second power module 102, and in particular, the controller 30 may be connected to at least one switching tube of the first power module 101 to control at least one switching tube of the first power module 101. The controller 30 may also be connected to at least one switching tube of the second power module 102 to control the at least one switching tube of the second power module 102.

It will be appreciated that in some possible implementations, the controller 30 may be mounted to other circuit boards. The controller 30 may be specifically configured to obtain a parameter of the first power module 101 or the second power module 102. The parameter may include at least one of an input voltage, an input current, an output voltage, an output current, an input power, and an output power of the first power module 101. The parameters may also include at least one of an input voltage, an input current, an output voltage, an output current, an input power, and an output power of the second power module 102.

In this embodiment, the controller 30 may control at least one switching tube of the first power module 101 or the second power module 102 to operate at the first frequency before the grid-connected inverter 100 performs IV scanning. When the grid-connected inverter 100 performs IV-scan, the controller 30 may control at least one switching tube of the first power module 101 or the second power module 102 to operate at the second frequency such that a temperature of the first power module 101 or the second power module 102 at the IV-scan is less than or equal to a temperature before the IV-scan.

In a specific implementation, the controller 30 may control the at least one switching tube of the first power module 101 to operate at the first frequency prior to the grid-tie inverter 100 performing the IV-scan. When the grid-connected inverter 100 performs IV scanning, the controller 30 may control at least one switching tube of the first power module 101 to operate at the second frequency, and by performing variable frequency control on at least one switching tube in the first power module 101, the temperature of the first power module 101 during IV scanning may be made to be less than or equal to the temperature before IV scanning. Alternatively, the second frequency may be less than the first frequency. In other words, when the grid-connected inverter 100 performs IV scanning, the controller 30 may reduce the temperature of the first power module 101 at the time of IV scanning by reducing the switching frequency of at least one switching tube in the first power module 101 such that the temperature of the first power module 101 at the time of IV scanning is less than or equal to the temperature before IV scanning. Wherein the temperature of the first power module 101 may include the temperature of the interior and the surface of the first power module 101.

In another specific implementation, the controller 30 may control the at least one switching tube of the second power module 102 to operate at the first frequency prior to the grid-tie inverter 100 performing the IV-scan. When the grid-connected inverter 100 performs IV scanning, the controller 30 may control at least one switching tube of the second power module 102 to operate at the second frequency, and by performing variable frequency control on at least one switching tube in the second power module 102, the temperature of the second power module 102 during IV scanning may be made to be less than or equal to the temperature before IV scanning. In other words, when the grid-connected inverter 100 performs IV scanning, the controller 30 may also reduce the temperature of the second power module 102 during IV scanning by reducing the switching frequency of at least one switching tube in the second power module 102, such that the temperature of the second power module 102 during IV scanning is less than or equal to the temperature before IV scanning. Wherein the temperature of the second power module 102 may include the temperature of the interior and surface of the second power module 102.

Referring to fig. 5, fig. 5 is a schematic diagram illustrating a possible structure of a dc conversion circuit 10 according to an embodiment of the present application.

As shown in fig. 5, the dc conversion circuit 10 may include an inductance L ₁ Capacitance C ₁ Capacitance C ₂ Diode D ₁ And a switch tube S ₁ 。

Switch tube S ₁ Is connected to the controller 30, switch tube S ₁ Is electrically connected to the inductor L ₁ And the diode D ₁ Anode of (C) switch tube S ₁ Is electrically connected to the capacitor C ₁ A first end of the photovoltaic module 200, a first output end of the capacitor C ₂ And the inverter circuit 20, more specifically, the switching tube S ₁ May be electrically connected to the second power module 102. Capacitor C ₁ Is electrically connected to the inductor L ₁ And a second output of the photovoltaic module 200. Diode D ₁ Can be electrically connected to the capacitor C ₂ Second end and inverse of (2)The transformer circuit 20, more specifically, diode D ₁ Can be electrically connected to the capacitor C ₂ And a second power module 102.

In some embodiments of the present application, the controller 30 may be electrically connected to the switching tube S ₁ In other embodiments of the present application, or the controller 30 may be signally connected to the switching tube S ₁ Is provided. In other words, the switching tube S ₁ Can be used as a switching tube S ₁ Is provided. The controller 30 can output a control signal to the switching tube S ₁ To control the switching tube S ₁ Is a state of (2). For example, the controller 30 may control the switching tube S ₁ Is turned on or off.

In some embodiments, a switching tube S ₁ May be an insulated gate bipolar transistor (Insulated Gate Bipolar Transistor, IGBT). In other alternative embodiments, the switching tube S ₁ And can be any one of Metal-Oxide-Semiconductor Field-Effect Transistor (MOS), thyristors, bipolar power transistors or wide bandgap semiconductor field effect transistors.

It will be appreciated that in one possible implementation, the switching tube S ₁ Can be encapsulated again according to certain function combination to form a module, namely a switch tube S ₁ Can be packaged into a housing to form a first power module 101, inductance L ₁ Capacitance C ₁ Capacitance C ₂ And diode D ₁ Mounted on the circuit board 103. In other possible implementations, the switching tube S ₁ And diode D ₁ May be packaged into a housing to form a first power module 101, inductance L ₁ Capacitance C ₁ Capacitance C ₂ Soldered to the circuit board 103.

It will be appreciated that, taking the dc conversion circuit 10 shown in the embodiment of fig. 5 as an example, the controller 30 may control the switching tube S before the grid-connected inverter 100 performs IV-scan ₁ Operating at a first frequency. The controller 30 can control the switching tube S when the grid-connected inverter 100 performs IV scanning ₁ Operate at a second positionThe frequency, while the second frequency is less than the first frequency, may be such that the temperature of the first power module 101 at the time of IV sweep is less than or equal to the temperature prior to IV sweep. In other words, the controller 30 may perform IV scan by lowering the switching tube S of the first power module 101 when the grid-connected inverter 100 performs IV scan ₁ The temperature of the first power module 101 in the IV scanning period will not rise, the temperature of the first power module 101 may meet the thermal stress requirement, and the stability of the grid-connected inverter 100 is improved.

Referring to fig. 6, fig. 6 is a schematic diagram illustrating a possible structure of an inverter circuit 20 according to an embodiment of the present application.

As shown in fig. 6, the inverter circuit 20 may include at least one controllable switching tube, and in particular, the inverter circuit 20 may include an a-phase switching module 212. The a-phase switching module 212 may comprise at least one controllable switching tube, in particular the a-phase switching module 212 may comprise a switching tube S ₁₁ Switch tube S ₁₂ Switch tube S ₁₃ Switch tube S ₁₄ Diode D ₁₁ And diode D ₁₂ 。

Diode D ₁₁ Anode electrically connected diode D ₁₂ Is provided. Diode D ₁₁ Anode and diode D of (c) ₁₂ The node between the cathodes of (a) is electrically connected with the capacitor C ₃ A second terminal of (C) and a capacitor C ₄ Is provided for the node N between the first ends of the pair. Switch tube S ₁₁ Is connected to the controller 30, switch tube S ₁₁ Is electrically connected to the DC output terminal V _bus+ Switch tube S ₁₁ Is electrically connected to diode D ₁₁ Is provided. Switch tube S ₁₁ Can be used as a switching tube S ₁₁ The controller 30 outputs a signal to the switching tube S ₁₁ To control the switching tube S ₁₁ Is a state of (2). Switch tube S ₁₂ Is connected to the controller 30, switch tube S ₁₂ Is electrically connected with the switch tube S ₁₁ Third terminal of (D) and diode D ₁₁ Cathode of switch tube S ₁₂ Is electrically connected to the switch tube S ₁₃ Is provided. Switch tube S ₁₂ Is the first end of (1)Can be used as a switching tube S ₁₂ The controller 30 outputs a signal to the switching tube S ₁₂ To control the switching tube S ₁₂ Is a state of (2). Switch tube S ₁₃ Is connected to the controller 30, switch tube S ₁₃ Is electrically connected to the switch tube S ₁₂ Third terminal of (C), switch tube S ₁₃ Is electrically connected to diode D ₁₂ Is a positive electrode of (a). Switch tube S ₁₃ Can be used as a switching tube S ₁₃ The controller 30 can output a signal to the switching tube S ₁₃ To control the switching tube S ₁₃ Is a state of (2). Switch tube S ₁₄ Is connected to the controller 30, a switching tube S ₁₄ Is electrically connected to the switch tube S ₁₃ And diode D ₁₂ Anode of (C) switch tube S ₁₄ Is electrically connected to the DC output terminal V _bus- . Switch tube S ₁₄ Can be used as a switching tube S ₁₄ The controller 30 can output a signal to the switching tube S ₁₄ To control the switching tube S ₁₄ Is a state of (2). In the present embodiment, the switching tube S ₁₂ Third terminal of (2) and switching tube S ₁₃ A node between the second terminals of (a) can output a first phase voltage U _u 。

In other embodiments, the inverter circuit 20 may further include a B-phase switching module 214, and the B-phase switching module 214 may include a switching tube S ₂₁ Switch tube S ₂₂ Switch tube S ₂₃ Switch tube S ₂₄ Diode D ₁₃ And diode D ₁₄ 。

Diode D ₁₃ Anode electrically connected diode D ₁₄ Is provided. Diode D ₁₃ Anode and diode D of (c) ₁₄ Is electrically connected to node N. Switch tube S ₂₁ Is connected to the controller 30, switch tube S ₂₁ Is electrically connected to the DC output terminal V _bus+ Switch tube S ₂₁ Is electrically connected to diode D ₁₃ Is provided. Switch tube S ₂₁ Can be used as a switching tube S ₂₁ The controller 30 outputs a signal to the switching tube S ₂₁ To control the switching tube S ₂₁ Is a state of (2). Switch tube S ₂₂ Is connected to the controller 30, switch tube S ₂₂ Is electrically connected with the switch tube S ₂₁ Third terminal of (D) and diode D ₁₃ Cathode of switch tube S ₂₂ Is electrically connected to the switch tube S ₂₃ Is provided. Switch tube S ₂₂ Can be used as a switching tube S ₂₂ The controller 30 outputs a signal to the switching tube S ₂₂ To control the switching tube S ₂₂ Is a state of (2). Switch tube S ₂₃ Is connected to the controller 30, switch tube S ₂₃ Is electrically connected to the switch tube S ₂₂ Third terminal of (C), switch tube S ₂₃ Is electrically connected to diode D ₁₄ Is a positive electrode of (a). Switch tube S ₂₃ Can be used as a switching tube S ₂₃ The controller 30 can output a signal to the switching tube S ₂₃ To control the switching tube S ₂₃ Is a state of (2). Switch tube S ₂₄ Is connected to the controller 30, a switching tube S ₂₄ Is electrically connected to the switch tube S ₂₃ And diode D ₁₄ Anode of (C) switch tube S ₂₄ Is electrically connected to the DC output terminal V _bus- . Switch tube S ₂₄ Can be used as a switching tube S ₂₄ The controller 30 can output a signal to the switching tube S ₂₄ To control the switching tube S ₂₄ Is a state of (2). In the present embodiment, the switching tube S ₂₂ Third terminal of (2) and switching tube S ₂₃ The node between the second ends of (2) can output a second phase voltage U _V 。

In other embodiments, the inverter circuit 20 may further include a C-phase switching module 216, and the C-phase switching module 216 may include a switching tube S ₃₁ Switch tube S ₃₂ Switch tube S ₃₃ Switch tube S ₃₄ Diode D ₁₅ And diode D ₁₆ 。

Diode D ₁₅ Anode electrically connected diode D ₁₆ Is provided. Diode D ₁₅ Anode and diode D of (c) ₁₆ Is a cathode of (a)The nodes between are electrically connected to node N. Switch tube S ₃₁ Is connected to the controller 30, switch tube S ₃₁ Is electrically connected to the DC output terminal V _bus+ Switch tube S ₃₁ Is electrically connected to diode D ₁₅ Is provided. Switch tube S ₃₁ Can be used as a switching tube S ₃₁ The controller 30 outputs a signal to the switching tube S ₃₁ To control the switching tube S ₃₁ Is a state of (2). Switch tube S ₃₂ Is connected to the controller 30, switch tube S ₃₂ Is electrically connected with the switch tube S ₃₁ Third terminal of (D) and diode D ₁₅ Cathode of switch tube S ₃₂ Is electrically connected to the switch tube S ₃₃ Is provided. Switch tube S ₃₂ Can be used as a switching tube S ₃₂ The controller 30 outputs a signal to the switching tube S ₃₂ To control the switching tube S ₃₂ Is a state of (2). Switch tube S ₃₃ Is connected to the controller 30, switch tube S ₃₃ Is electrically connected to the switch tube S ₃₂ Third terminal of (C), switch tube S ₃₃ Is electrically connected to diode D ₁₆ Is a positive electrode of (a). Switch tube S ₃₃ Can be used as a switching tube S ₃₃ The controller 30 can output a signal to the switching tube S ₃₃ To control the switching tube S ₃₃ Is a state of (2). Switch tube S ₃₄ Is connected to the controller 30, a switching tube S ₃₄ Is electrically connected to the switch tube S ₃₃ And diode D ₁₆ Anode of (C) switch tube S ₃₄ Is electrically connected to the DC output terminal V _bus- . Switch tube S ₃₄ Can be used as a switching tube S ₃₄ The controller 30 can output a signal to the switching tube S ₃₄ To control the switching tube S ₃₄ Is a state of (2). In the present embodiment, the switching tube S ₃₂ Third terminal of (2) and switching tube S ₃₃ A node between the second terminals of (a) can output a third phase voltage U _W 。

It will be appreciated that in one possible implementation, the switching tube S ₁₁ Switch tube S ₁₂ Switch tube S ₁₃ Switch tube S ₁₄ Can be encapsulated again according to certain function combination to form a module, namely a switch tube S ₁₁ Switch tube S ₁₂ Switch tube S ₁₃ Switch tube S ₁₄ May be packaged into a housing to form the second power module 102. In other possible implementations, the switching tube S ₁₁ -S ₁₄ Switch tube S ₂₁ -S ₂₄ And a switch tube S ₃₁ -S ₃₄ May be packaged into a housing to form the second power module 102.

It will be appreciated that, taking the inverter circuit 20 shown in the embodiment of fig. 6 as an example, the controller 30 may control the switching tube S before the grid-connected inverter 100 performs IV-scan ₁₁ -S ₁₄ Operating at a first frequency. The controller 30 can control the switching tube S when the grid-connected inverter 100 performs IV scanning ₁₁ -S ₁₄ Operating at the second frequency may result in the second power module 102 having a temperature at the time of IV scan that is less than or equal to the temperature prior to IV scan. In other words, the controller 30 may perform the IV scan by lowering the switching tube S of the second power module 102 when the grid-connected inverter 100 performs the IV scan ₁₁ -S ₁₄ The temperature of the second power module 102 in the IV scanning period will not rise, the temperature of the second power module 102 may meet the thermal stress requirement, and the stability of the grid-connected inverter 100 is improved. According to the control method of the power converter, before and during IV curve scanning of the photovoltaic module, the switching frequency of the power module in the direct current conversion circuit 10 is adjusted, so that the temperature of the power module during IV scanning is smaller than or equal to the temperature before the scanning, in other words, the temperature of the power module during IV scanning can not be increased, and further the reliability of a photovoltaic power generation system is improved.

Referring to fig. 7, fig. 7 is a flowchart of a control method of a power converter according to an embodiment of the present application, where the control method may be executed by the controller 30. The control method may be used to control the power converter 40, which performs dc and ac conversion between the photovoltaic module and the ac power grid, by modulating the signal. The dc conversion circuit 10 of the power converter 40 may include at least one switching tube. The modulation signal may control the on and off of at least one switching tube in the dc conversion circuit. The control method of the power converter may include the steps of:

step S71: an IV scan instruction is received.

When the photovoltaic module 200 needs to perform IV curve scanning, the upper computer may issue an IV scanning instruction to the controller 30, and the controller 30 may receive the IV scanning instruction.

Step S72: parameters of the first power module and the second power module are obtained.

As illustrated in the above-described scenarios shown in fig. 3 to 6, the controller 30 may obtain the performance parameters of the dc conversion circuit 10 or the inverter circuit 20 when the controller 30 receives the IV-scan command issued by the host computer. As a specific implementation, the controller 30 may obtain a performance parameter of the first power module 101 or the second power module 102.

For example, the controller 30 may acquire at least one of an input voltage, an input current, an output voltage, an output current, an input power, and an output power of the dc conversion circuit 10 or the inverter circuit 20. As a specific implementation, the controller 30 may obtain at least one of an input voltage, an input current, an output voltage, an output current, an input power, and an output power of the first power module 101 or the second power module 102.

The input voltage of the dc conversion circuit 10 is the output voltage of the photovoltaic module 200, the input current of the dc conversion circuit 10 is the output current of the photovoltaic module 200, and the output voltage of the dc conversion circuit 10 is the input voltage of the inverter circuit 20.

In some possible implementations, the periphery of the switching tube or the surface of the switching tube may be provided with one or more temperature sensors that sense the package temperature of the switching tube and feed the sensed package temperature of the switching tube back to the controller 30 in real time.

Step S73: the switching frequency of at least one switching tube of the first power module or the second power module in the IV curve scanning process is calculated.

In this embodiment, the controller 30 may control at least one switching tube of the first power module 101 or the second power module 102 to operate at the first frequency before the power converter 40 performs IV scanning. The controller 30 may calculate the switching frequency of at least one switching tube of the first power module 101 or the second power module 102 during IV curve scanning. Thus, the controller 30 may control at least one switching tube of the first power module 101 or the second power module 102 to operate at the second frequency while the power converter 40 performs IV scanning. This may allow the temperature of the first power module 101 or the second power module 102 at the time of IV scanning to be less than or equal to the temperature before IV scanning.

As some alternative implementations, the controller 30 may determine the switching tube S of the first power module 101 according to the parameter of the first power module 101 ₁ Switching frequency during IV curve scan. The controller 30 may calculate the switching tube S according to the parameters of the first power module 101 ₁ The temperature of the first power module 101 operating at different switching frequencies.

The controller 30 may determine the switching tube S of the second power module 102 according to the parameters of the second power module 102 _11- S ₁₄ Switching frequency during IV curve scan. The controller 30 may calculate the switching tube S according to the parameters of the second power module 102 ₁₁ -S ₁₄ The temperature of the second power module 102 operating at a different switching frequency.

It can be appreciated that in this embodiment, the controller 30 may adjust the switching frequency of at least one switching tube of the first power module 101 or the second power module 102 before and during IV curve scanning, so that the temperature of the first power module 101 or the second power module 102 during IV curve scanning is not increased, and the IV scanning can obtain a complete curve for fault diagnosis of the photovoltaic module, which can avoid the problem that the IV scanning fails due to the fact that the IV scanning cannot obtain the curve in extreme scenarios, and improve the reliability of the photovoltaic power generation system.

In this embodiment, the controller 30 may obtain the switching tube S according to the dc conversion circuit 10 ₁ A mapping relationship between the switching frequency and the temperature. It can be appreciated that when the switching tube S of the dc conversion circuit 10 ₁ The smaller the switching frequency of the first power module 101, the lower the temperature.

For example, when the switching tube S of the first power module 101 ₁ The temperature of the first power module 101 is 140 degrees celsius when the switching frequency of (a) is 18 kHz. When the switching tube S of the first power module 101 ₁ The temperature of the first power module 101 is 120 degrees celsius when the switching frequency of (a) is 16 kHz. When the switching tube S of the first power module 101 ₁ The temperature of the first power module 101 is 100 degrees celsius when the switching frequency of (a) is 14 kHz.

Step S74: and controlling the switching frequency of the first power module or the second power module during the IV scanning, and performing the IV scanning.

The controller 30 may select a switching frequency of the power module at which the temperature of the power module satisfies the thermal stress requirement as a frequency of the switching tube during IV sweep, and switch the switching frequency of the switching tube of the first power module or the second power module. At this point, the controller 30 may begin IV scanning the photovoltaic module 200.

As will be described below in conjunction with fig. 5, the controller 30 may control the switching tube S before the grid-tied inverter 100 performs IV-scan ₁ Operating at a first frequency. The controller 30 can control the switching tube S when the grid-connected inverter 100 performs IV scanning ₁ Operating at the second frequency, which is less than the first frequency, may result in the first power module 101 having a temperature at the time of IV sweep that is less than or equal to the temperature prior to IV sweep. In other words, the controller 30 may perform IV scan by lowering the switching tube S of the first power module 101 when the grid-connected inverter 100 performs IV scan ₁ The temperature of the first power module 101 in the IV scanning period will not rise, the temperature of the first power module 101 may meet the thermal stress requirement, and the stability of the grid-connected inverter 100 is improved.

As will be described further below in conjunction with fig. 6, the controller 30 may control the switches prior to IV-scanning by the grid-tie inverter 100Tube S ₁₁ -S ₁₄ Operating at a first frequency. The controller 30 can control the switching tube S when the grid-connected inverter 100 performs IV scanning ₁₁ -S ₁₄ Operating at the second frequency may result in the second power module 102 having a temperature at the time of IV scan that is less than or equal to the temperature prior to IV scan. In other words, the controller 30 may perform the IV scan by lowering the switching tube S of the second power module 102 when the grid-connected inverter 100 performs the IV scan ₁₁ -S ₁₄ The temperature of the second power module 102 in the IV scanning period will not rise, the temperature of the second power module 102 may meet the thermal stress requirement, and the stability of the grid-connected inverter 100 is improved.

According to the control method of the power converter, the temperature of the first power module or the second power module during IV scanning can be reduced by adopting a mode of reducing the switching frequency of at least one switching tube in the first power module or the second power module, so that the temperature of the first power module or the second power module during IV scanning is smaller than or equal to the temperature before IV scanning, and the reliability of a photovoltaic power generation system is further improved.

The controller 30 can control the input voltage of the dc conversion circuit 10 to change from the open circuit voltage to the short circuit voltage according to a preset rule according to the IV scan command, so as to realize IV curve scan.

Referring to fig. 8, fig. 8 is a schematic structural diagram of a controller 30 according to an embodiment of the present application. The controller 30 may be configured to perform some or all of the steps of the control method of the power converter described in fig. 7, particularly please refer to the related description in fig. 7.

The controller 30 may include an acquisition unit 310, a calculation unit 320, and a control unit 330, and may specifically be as follows:

the acquisition unit 310 may acquire parameters of the first power module 101 or the second power module 102 before the power converter performs the current-voltage IV curve scan. The parameter may include at least one of an input voltage, an input current, an output voltage, an output current, an input power, and an output power of the first power module 101 or the second power module 102.

The control unit 330 may control the power converter to perform IV scanning, and control the switching frequency of at least one switching tube of the first power module 101 or the second power module 102, so that when the power converter performs IV scanning, the temperature of the first power module 101 or the second power module 102 will not increase, i.e. the temperature of the first power module 101 or the temperature of the second power module 102 may meet the thermal stress requirement.

For example, the control unit 330 in the embodiment of the present application may control at least one switching tube of the first power module 101 or the second power module 102 to operate at the first frequency before the power converter 40 performs IV scanning; at least one switching tube of the first power module 101 or the second power module 102 is controlled to operate at the second frequency when the power converter 40 performs IV scanning, so that the temperature of the first power module 101 or the second power module 102 at the time of IV scanning is less than or equal to the temperature before IV scanning. Alternatively, the second frequency may be less than the first frequency.

The calculating unit 320 in the embodiment of the present application may calculate the mapping relationship between the frequency and the temperature of at least one switching tube of the first power module 101 or the second power module 102 according to the parameter of the first power module 101 or the second power module 102. The control unit 330 may control the frequency of at least one switching tube of the first power module 101 or the second power module 102 according to the mapping relationship when the power converter 40 performs IV scanning, so that the temperature of the first power module 101 or the second power module 102 during IV scanning is less than or equal to the temperature before IV scanning.

Fig. 9 is a schematic diagram of another structure of the controller 30 according to the embodiment of the present application.

In one embodiment, the controller 30 includes a memory 301 and at least one processor 302. It will be appreciated by those skilled in the art that the configuration of the controller 30 shown in fig. 9 is not limiting of the embodiments of the present application, and that the controller 30 may also include additional hardware or software, more or less than that shown, or a different arrangement of components.

In some embodiments, the controller 30 comprises a terminal capable of automatically performing numerical calculations and/or information processing according to predetermined or stored instructions, the hardware of which includes, but is not limited to, microprocessors, application specific integrated circuits, programmable gate arrays, digital processors, embedded devices, and the like. In some embodiments, memory 301 is used to store program codes and various data. The Memory 301 may include Read-Only Memory (ROM), random-access Memory (Random Access Memory, RAM), programmable Read-Only Memory (Programmable Read-Only Memory, PROM), erasable programmable Read-Only Memory (EPROM), one-time programmable Read-Only Memory (OTPROM), electrically erasable programmable Read-Only Memory (EEPROM), compact disc Read-Only Memory (Compact Disc Read-Only Memory, CD-ROM) or other optical disk Memory, magnetic disk Memory, tape Memory, or any other medium capable of being used to carry or store data.

In some embodiments, the at least one processor 302 may comprise an integrated circuit, for example, an integrated circuit that may comprise a single package, or may comprise a plurality of integrated circuits packaged with the same or different functionality, including a microprocessor, a digital processing chip, a combination of a graphics processor and various control chips, and the like. The at least one processor 302 is a Control Unit of the controller, and executes various functions of the controller 30 and processes data by running or executing programs or modules stored in the memory 301, and calling data stored in the memory 301. The integrated units implemented in the form of software functional modules described above may be stored in a computer readable storage medium. The software functional modules described above are stored in a storage medium and include instructions for causing a computer device (which may be a personal computer, a terminal, or a network device, etc.) or processor (processor) to perform portions of the methods described in various embodiments of the present application. The memory 301 has stored therein program code, and the at least one processor 302 can invoke the program code stored in the memory 301 to perform related functions. In one embodiment of the present application, the memory 301 stores a plurality of instructions that are executed by the at least one processor 302 to implement the method of controlling a power converter described above. Specifically, the specific implementation method of the above instruction by the at least one processor 302 may refer to the description of the relevant steps in the corresponding embodiment of fig. 7, which is not repeated herein.

It will be appreciated that the specific implementation of the controller 30 may be referred to the above embodiments, and will not be described herein.

The embodiment of the application also provides a storage medium. Wherein the storage medium has stored therein computer instructions which, when executed on a computing device, cause the computing device to perform the method of controlling a power converter provided by the foregoing embodiments.

It will be appreciated by persons skilled in the art that the above embodiments are provided for illustration only and not as limitations of the present application, and that suitable modifications and variations of the above embodiments are within the scope of the application as claimed.

Claims

1. A grid-connected inverter comprises a controller, a first power module, a second power module and a circuit board, and is characterized in that,

the first power module and the second power module are both arranged on the circuit board, and the output end of the first power module is connected with the second power module;

the first power module comprises at least one switching tube and is used for connecting the outputs of the photovoltaic modules so as to perform power conversion on the direct current power input into the first power module;

The second power module comprises at least one switch tube and is used for receiving direct current power from the first power module;

the controller is used for:

acquiring parameters of the first power module or the second power module, wherein the parameters comprise; at least one of an input voltage, an input current, an output voltage, an output current, an input power, and an output power of the first power module or the second power module;

before the grid-connected inverter performs IV scanning, controlling at least one switching tube of the first power module or the second power module to work at a first frequency;

and when the grid-connected inverter performs IV scanning, controlling at least one switching tube of the first power module or the second power module to work at a second frequency, so that the temperature of the first power module or the second power module during IV scanning is less than or equal to the temperature before IV scanning.

2. The grid-tie inverter of claim 1,

the second frequency is less than the first frequency.

3. The grid-tie inverter according to claim 1 or 2, wherein,

the grid-connected inverter further comprises a direct current conversion circuit and an inverter circuit, wherein the direct current conversion circuit comprises at least one switching tube of the first power module, the inverter circuit comprises at least one switching tube of the second power module, the input of the direct current conversion circuit is used for being connected with the output of the photovoltaic modules, the output of the direct current conversion circuit is used for being connected with the inverter circuit, and direct current converted by the direct current conversion circuit is converted into alternating current required by a power grid or a load through the inverter circuit.

4. The grid-tie inverter according to claim 3,

the at least one switching tube of the first power module comprises a first switching tube, the direct current conversion circuit comprises an inductor, a diode and the first switching tube, the first switching tube is electrically connected with a first end of the inductor and an anode of the diode, a second end of the inductor is electrically connected with a first end of a first capacitor and outputs of the photovoltaic modules, a second end of the first capacitor is electrically connected with the outputs of the photovoltaic modules and the first switching tube, a cathode of the diode is electrically connected with a first end of a second capacitor and the second power module, and a second end of the second capacitor is electrically connected with the second power module;

the controller is further configured to:

before the grid-connected inverter performs IV scanning, controlling the first switching tube to work at the first frequency;

and when the grid-connected inverter performs IV scanning, controlling the first switching tube to work at the second frequency, so that the temperature of the first power module during IV scanning is smaller than or equal to the temperature before IV scanning.

5. The grid-tie inverter according to claim 3,

The inverter circuit comprises a first diode, a second diode, a first switching tube, a second switching tube, a third switching tube and a fourth switching tube, wherein the first switching tube is electrically connected between a first output end of the direct-current conversion circuit and the second switching tube, the second switching tube is electrically connected between the first switching tube and the third switching tube, the fourth switching tube is electrically connected between the third switching tube and a second output end of the direct-current conversion circuit, a node between the first switching tube and the second switching tube is electrically connected to a cathode of the first diode, an anode of the first diode is electrically connected to a cathode of the second diode, and an anode of the second diode is electrically connected to a node between the third switching tube and the fourth switching tube;

the controller is further configured to:

before the grid-connected inverter performs IV scanning, controlling the first switching tube, the second switching tube, the third switching tube and the fourth switching tube to work at the first frequency;

When the grid-connected inverter performs IV scanning, the first switching tube, the second switching tube, the third switching tube and the fourth switching tube are controlled to work at the second frequency, so that the temperature of the second power module during IV scanning is smaller than or equal to the temperature before IV scanning.

6. The grid-tie inverter of claim 1,

the controller is further configured to:

acquiring a mapping relation between the frequency and the temperature of at least one switching tube of the first power module or the second power module according to the parameters of the first power module or the second power module;

and when the grid-connected inverter performs IV scanning, controlling the frequency of at least one switching tube of the first power module or the second power module according to the mapping relation, so that the temperature of the first power module or the second power module during IV scanning is smaller than or equal to the temperature before IV scanning.

7. The grid-tie inverter according to any one of claims 1-6,

the temperature of the first power module includes the temperature of the interior and surface of the first power module;

the temperature of the second power module includes the temperature of the interior and surface of the second power module.

8. The control method of the power converter is characterized in that the power converter comprises a first power module and a second power module, wherein the output end of the first power module is connected with the second power module, the first power module comprises at least one switch tube used for being connected with the output of a plurality of photovoltaic modules so as to perform power conversion on direct current power input into the first power module, and the second power module comprises at least one switch tube used for receiving direct current power from the first power module; the control method comprises the following steps:

acquiring parameters of the first power module or the second power module, wherein the parameters comprise at least one of input voltage, input current, output voltage, output current, input power and output power of the first power module or the second power module;

before the power converter performs IV scanning, controlling at least one switching tube of the first power module or the second power module to work at a first frequency;

and when the power converter performs IV scanning, controlling at least one switching tube of the first power module or the second power module to work at a second frequency, so that the temperature of the first power module or the second power module during IV scanning is less than or equal to the temperature before IV scanning.

9. The method for controlling a power converter according to claim 8, wherein,

the second frequency is less than the first frequency.

10. The method for controlling a power converter according to claim 8 or 9, wherein,

the power converter comprises a direct current conversion circuit, at least one switching tube of the first power module comprises a first switching tube, the direct current conversion circuit comprises an inductor, a diode and the first switching tube, the first switching tube is electrically connected with a first end of the inductor and an anode of the diode, a second end of the inductor is electrically connected with a first end of a first capacitor and outputs of the photovoltaic modules, a second end of the first capacitor is electrically connected with the outputs of the photovoltaic modules and the first switching tube, a cathode of the diode is electrically connected with a first end of a second capacitor and the second power module, and a second end of the second capacitor is electrically connected with the second power module;

the control method further includes:

controlling the first switching tube to operate at the first frequency before the power converter performs IV scanning;

and when the power converter performs IV scanning, controlling the first switching tube to work at the second frequency so that the temperature of the first power module during IV scanning is less than or equal to the temperature before IV scanning.

11. The method for controlling a power converter according to claim 8 or 9, wherein,

the power converter further comprises an inverter circuit, at least one switching tube of the second power module comprises a first switching tube, a second switching tube, a third switching tube and a fourth switching tube, the inverter circuit comprises a first diode, a second diode, the first switching tube, the second switching tube, the third switching tube and the fourth switching tube, the first switching tube is electrically connected between a first output end of the direct current conversion circuit and the second switching tube, the second switching tube is electrically connected between the first switching tube and the third switching tube, the fourth switching tube is electrically connected between the third switching tube and a second output end of the direct current conversion circuit, a node between the first switching tube and the second switching tube is electrically connected to a cathode of the first diode, an anode of the first diode is electrically connected to a cathode of the second diode, and an anode of the second diode is electrically connected to a node between the third switching tube and the fourth switching tube;

the control method further includes:

Before the power converter performs IV scanning, controlling the first switching tube, the second switching tube, the third switching tube and the fourth switching tube to work at the first frequency;

and when the power converter performs IV scanning, controlling the first switching tube, the second switching tube, the third switching tube and the fourth switching tube to work at the second frequency, so that the temperature of the second power module during IV scanning is smaller than or equal to the temperature before IV scanning.

12. The control method of a power converter according to claim 8, characterized in that the control method further comprises:

and when the power converter performs IV scanning, controlling the frequency of at least one switching tube of the first power module or the second power module according to the mapping relation, so that the temperature of the first power module or the second power module during IV scanning is less than or equal to the temperature before IV scanning.

13. A control method of a power converter according to any one of claims 8-12,