Grid-connected inverter device and grid-connected control method

Abstract

This application provides a grid-connected inverter and a grid-connected control method. The inverter includes an inverter circuit, a controller, and a filter circuit. The controller adjusts the switching frequencies of multiple power switches based on the output current value of the inverter, thereby adjusting the resonant frequency of the filter circuit through different resonant branches to ensure that the resonant frequency meets grid connection requirements. Using this application, when the switching frequencies of multiple power switches in the inverter circuit decrease due to power system overload, resonance is generated through different resonant branches, and the resonant frequency of the filter circuit is adjusted in a timely manner to ensure that the resonant frequency of the filter circuit meets the system stability requirements. This method offers rapid response, simple control, improved system stability and safety, and strong applicability.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a grid-connected inverter device and a grid-connected control method. Background Technology

[0002] In the field of power electronics, an inverter circuit in a power supply system converts the input voltage provided at the input terminal (e.g., the power supply terminal) into an output voltage that matches the output terminal (e.g., the load terminal), thereby supplying power to the output terminal through the input terminal. Because the switching frequency of components (e.g., switching transistors) in the inverter circuit is relatively high, the output current (or voltage) of the inverter circuit contains harmonics. A filter circuit needs to be placed between the inverter circuit and the load to remove these harmonics. To maintain system stability, the resonant frequency of the filter circuit is typically required to be lower than a certain grid-connected stable frequency (e.g., the switching frequency of a quarter of the power switching transistors). However, in some application scenarios (e.g., short-term overload), to meet the power demand of the load, the inverter circuit needs to reduce its switching frequency to maintain the operation of the power supply system. In this case, an excessively high resonant frequency of the filter circuit can lead to system instability. In the course of research and practice, the inventors of this application discovered that in the prior art, it is usually necessary to collect the output current of the inverter circuit and adjust the output voltage of the inverter circuit based on the output current of the inverter circuit to cope with load changes. This makes the control process complex and cumbersome, the control time long, and the adaptability poor. Summary of the Invention

[0003] This application provides a grid-connected inverter device and a grid-connected control method. When the switching frequency of multiple power switching transistors in the inverter circuit decreases due to power system overload, resonance is generated through different resonant branches, and the resonant frequency of the filter circuit is adjusted in a timely manner to ensure that the resonant frequency of the filter circuit meets the requirements of system stability. The device has a rapid response, a simple control method, improves system stability and safety, and has strong applicability.

[0004] Firstly, this application provides a grid-connected inverter device, which includes an inverter circuit, a controller, and a filter circuit. Here, the inverter circuit includes multiple power switching transistors connected in series or parallel, and the filter circuit includes multiple resonant branches composed of an inductor unit and multiple parallel resonant units. One end of the inverter circuit is connected to a DC input power supply, and the other end of the inverter circuit is connected to the power grid or a load through the filter circuit. The controller is connected to the inverter circuit. The controller can adjust the switching frequency of the multiple power switching transistors based on the output current value of the inverter device, thereby adjusting the resonant frequency of the filter circuit through different resonant branches to ensure that the resonant frequency meets grid connection requirements.

[0005] In this application, the controller can obtain the output current value of the inverter (through methods such as acquisition, collection, reception, detection, or storage). The output current value of the inverter can be the output current value of the inverter circuit, the output current value at the connection point between the inverter and the load (e.g., the grid connection point when the load is the power grid), or the output current value of the sampling point, which can be set according to the application scenario. Here, the controller can adjust the switching frequency of multiple power switches based on the output current value of the inverter. It can be understood that in different application scenarios (e.g., the inverter is equivalent to a voltage source in a grid-connected scenario), the controller can control the switching frequency of multiple power switches at different switching frequencies based on the output current value of the inverter to adjust the output power of the inverter to adapt to changes in the load, thereby ensuring normal power supply to the load. For example, in a scenario where the power supply system is overloaded (i.e., the load increases), the controller can reduce the switching frequency of multiple power switches. During the operation of an inverter, due to the high switching frequency of components (such as switching transistors) in the inverter circuit, the output current (or voltage) contains harmonics. A filter circuit is needed between the inverter circuit and the load to remove these harmonics. In grid-connected scenarios, to maintain system stability, the resonant frequency of the filter circuit is typically required to be lower than a certain grid-connected stable frequency (e.g., 1 / 4 of the switching frequency). Here, the filter circuit comprises multiple resonant branches consisting of an inductor unit and multiple parallel resonant units. The device can also adjust the resonant frequency of the filter circuit through different resonant branches. For example, in scenarios where the power supply system is overloaded (i.e., the load increases), the controller can reduce the switching frequency of multiple power switching transistors to adjust the resonant frequency of the filter circuit through multiple resonant units, thereby maintaining the stability of the power supply system.

[0006] In conjunction with the first aspect, in a first possible implementation, the filter circuit is used to adjust the resonant frequency of the filter circuit by resonating through the resonant branch with the lowest equivalent impedance among multiple resonant branches when the switching frequencies of the multiple power switches are different. Here, when the controller adjusts the switching frequencies of the multiple power switches, it simultaneously changes the magnitude of the equivalent impedance in the multiple resonant branches. Different resonant branches (e.g., a first resonant branch composed of a capacitor unit and an inductor unit, and a second resonant branch composed of a variable filter unit and an inductor unit) have different equivalent impedances at different switching frequencies. When the controller adjusts the switching frequencies of the multiple power switches, the current mainly flows through the resonant branch with the lowest equivalent impedance at the current switching frequency, causing the resonant branch with the lowest equivalent impedance to resonate at the resonant frequency corresponding to the current switching frequency. Furthermore, based on the different switching frequencies of the inverter circuit, the filter circuit can adjust its resonant frequency through different resonant branches.

[0007] By employing this application, when the switching frequency of multiple power switching transistors in the inverter circuit decreases due to power system overload, resonance can be achieved through the resonant branch with the lowest equivalent impedance among multiple resonant branches. This allows for timely adjustment of the resonant frequency of the filter circuit, enhancing the load-carrying capacity of the device while ensuring that the resonant frequency of the filter circuit meets the system stability requirements. The application is characterized by rapid response, simple control method, improved system stability and safety, and strong applicability.

[0008] In conjunction with the first possible implementation of the first aspect, in the second possible implementation, the multiple resonant units may include a capacitor unit and at least one variable filter unit. The inductor unit may include a first inductor unit and a second inductor unit, which may be connected in series between the inverter circuit and the load. The capacitor unit and the variable filter unit may be connected in parallel between the first inductor unit and the second inductor unit. The capacitor unit and the inductor unit may form a first resonant branch, and the variable filter unit and the inductor unit may form a second resonant branch. The controller here can also be used to adjust the switching frequency of multiple power switching transistors to a first switching frequency when the output current value of the inverter is less than the overload current value, so as to adjust the resonant frequency of the filter circuit to the first resonant frequency through the first resonant branch. Here, when the switching frequency is the first switching frequency, the equivalent impedance of the first resonant branch is less than the equivalent impedance of the second resonant branch. Here, the first resonant frequency is less than the first stable frequency, which is the grid-connected stable frequency corresponding to the first switching frequency (e.g., the first stable frequency is 1 / 4 of the first switching frequency). It is understandable that after the controller obtains the output current value of the inverter (through methods such as acquisition, sampling, receiving, detection, or storage), the controller can control the switching frequency of multiple power switches based on the output current value of the inverter. When the output current value of the inverter is less than the overload current value, it indicates that the current load condition meets the operating conditions of the inverter (e.g., the load is within the rated load range), and the controller can adjust the switching frequency of the multiple power switches to a first switching frequency. Here, the first switching frequency can be the current switching frequency of the inverter circuit, the frequency obtained by the controller through methods such as acquisition, sampling, receiving, detection, or storage, the switching frequency of the multiple power switches in the inverter circuit under rated operating conditions, or the frequency calculated by the controller based on the current output current value of the inverter. The specific frequency can be set according to the application scenario. It is understandable that the first switching frequency can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values. Here, among the multiple resonant branches, the first resonant branch, composed of capacitor units and inductor units (e.g., the first inductor unit and the second inductor unit), has the smallest equivalent impedance when the switching frequency of the multiple power switches is the first switching frequency. Current mainly flows through this first resonant branch, causing it to resonate at the resonant frequency corresponding to the first switching frequency (i.e., the first resonant frequency). In other words, when the output current of the inverter is less than the overload current, the resonant frequency of the filter circuit can be adjusted to the first resonant frequency based on the switching frequency of the multiple power switches (i.e., the first switching frequency) through the first resonant branch.Here, the first resonant frequency is less than the first stable frequency, which is the grid-connected stable frequency corresponding to the first switching frequency (e.g., the first stable frequency is 1 / 4 of the first switching frequency). In some application scenarios, to meet system stability requirements, the first resonant frequency needs to be less than a certain grid-connected stable frequency (e.g., 1 / 4 of the first switching frequency). It can be understood that the value of the first resonant frequency here can be determined based on the current resonant frequency of the filter circuit. It can be a frequency obtained by the controller through methods such as acquisition, sampling, receiving, detection, or storage; it can be the rated resonant frequency of the filter circuit; or it can be a frequency calculated by the controller based on the current output current value of the inverter. The specific setting depends on the application scenario. It can be understood that the first resonant frequency here can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values.

[0009] By using this application, when the load of the power supply system meets the current operating state of the inverter, the switching frequency of multiple power switching transistors can be adjusted to the first switching frequency, so as to adjust the resonant frequency of the filter circuit to the first resonant frequency through the first resonant branch, so as to ensure that the resonant frequency of the filter circuit meets the requirements of system stability. The control method is simple, flexible and highly applicable.

[0010] In conjunction with the second possible implementation of the first aspect, in the third possible implementation, the controller can also be used to reduce the switching frequency of multiple power switches to a second switching frequency when the output current value of the inverter is greater than or equal to the overload current value, thereby enhancing the load-carrying capacity of the inverter, and to adjust the resonant frequency of the filter circuit to a second resonant frequency through the second resonant branch. Here, the second switching frequency is less than the first switching frequency, and when the switching frequency is the second switching frequency, the equivalent impedance of the second resonant branch is less than the equivalent impedance of the first resonant branch. Here, the second resonant frequency is less than the second stable frequency and less than the first resonant frequency, and the second stable frequency is the grid-connected stable frequency corresponding to the second switching frequency (for example, the second stable frequency is 1 / 4 of the second switching frequency). It can be understood that after the controller obtains the output current value of the inverter (through, for example, acquisition, collection, reception, detection, or storage), the controller can control the switching frequency of the multiple power switches based on the output current value of the inverter. When the output current of the inverter is greater than or equal to the overload current, it indicates that the current load condition does not meet the inverter's operating conditions (e.g., the load has increased and is in an overload state). The controller can then reduce the switching frequency of multiple power switches to a second switching frequency. Here, the second switching frequency is less than the first switching frequency. The second switching frequency can be a frequency less than the current switching frequency of the inverter circuit (e.g., the second switching frequency itself), a frequency obtained by the controller through methods such as acquisition, sampling, receiving, detection, or storage, the switching frequency of the multiple power switches in the inverter circuit under overload conditions, or a frequency calculated by the controller based on the current output current of the inverter. The specific frequency can be set according to the application scenario. It can be understood that the second switching frequency can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values. Here, among the multiple resonant branches, the second resonant branch, composed of the variable filter unit and the inductor unit (e.g., the first inductor unit and the second inductor unit), has the smallest equivalent impedance when the switching frequency of the multiple power switches is the second switching frequency. Current mainly flows through this second resonant branch, causing it to resonate at the resonant frequency corresponding to the second switching frequency (i.e., the second resonant frequency). In other words, when the output current of the inverter is greater than or equal to the overload current, the resonant frequency of the filter circuit can be reduced to the second resonant frequency based on the switching frequency of the multiple power switches (i.e., the second switching frequency) through the second resonant branch. Here, the second resonant frequency is less than the second stable frequency and less than the first resonant frequency. The second stable frequency is the grid-connected stable frequency corresponding to the second switching frequency (e.g., the second stable frequency is 1 / 4 of the second switching frequency).During the grid connection process of the power supply system, in order to meet the system stability requirements, the second resonant frequency needs to be lower than a certain grid-connected stable frequency (e.g., 1 / 4 of the second switching frequency). It can be understood that the value of the second resonant frequency here can be determined based on the current resonant frequency of the filter circuit. It can be a frequency obtained by the controller through methods such as acquisition, sampling, receiving, detection, or storage; it can be the overload resonant frequency of the filter circuit; or it can be a frequency calculated by the controller based on the current output current value of the inverter. The specific setting can be determined according to the application scenario. It can be understood that the second resonant frequency here can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values.

[0011] By adopting this application, when the load of the power supply system increases and the current inverter is in an overloaded operating state, the switching frequency of multiple power switching transistors can be reduced to a second switching frequency, so as to adjust the resonant frequency of the filter circuit through the second resonant branch to a second resonant frequency, thereby ensuring that the resonant frequency of the filter circuit meets the requirements of system stability. The control method is simple, flexible and highly applicable.

[0012] In conjunction with the third possible implementation of the first aspect, in the fourth possible implementation, the controller can also be used to increase the switching frequency of the multiple power switches to a first switching frequency when the switching frequency of the multiple power switches is a second switching frequency and the output current value of the inverter is less than the reset current value, so as to adjust the resonant frequency of the filter circuit to the first resonant frequency through the first resonant branch. Here, the reset current value is less than or equal to the overload current value. It can be understood that after the controller controls the switching frequency of the multiple power switches to the second switching frequency, the controller can also obtain the output current value of the inverter (by means of, for example, acquiring, collecting, receiving, detecting, or storing), and the controller can also control the switching frequency of the multiple power switches based on the output current value of the inverter. When the switching frequency of the multiple power switches is the second switching frequency and the output current value of the inverter is less than the reset current value, it can be indicated that the current load state once again meets the operating conditions of the inverter (e.g., the load is reduced to the rated load range), and the controller can increase the switching frequency of the multiple power switches to the first switching frequency. Here, the first switching frequency after the frequency reduction can be equal to the first switching frequency before the frequency reduction, or it can be a third switching frequency within the range of the first switching frequency. It is not necessarily exactly equal to the first switching frequency before the frequency reduction. The first switching frequency that the inverter circuit reverts to can be a frequency greater than the current switching frequency of the inverter circuit (e.g., the second switching frequency). It can be a frequency obtained by the controller through methods such as acquisition, sampling, receiving, detection, or storage; it can be the switching frequency of multiple power switches in the inverter circuit under rated operating conditions; or it can be a frequency calculated by the controller based on the current output current value of the inverter device. The specific frequency can be set according to the application scenario. It can be understood that the first switching frequency that the inverter circuit reverts to can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values. Correspondingly, when the output current value of the inverter device is less than the reset current value, the resonant frequency of the filter circuit can be re-raised to the first resonant frequency through the first resonant branch based on the switching frequencies of multiple power switches (i.e., the first switching frequency). Here, the first resonant frequency that the filter circuit raises back to can be equal to the first resonant frequency before frequency reduction, or it can be a third resonant frequency within the range of the first resonant frequency. It is not necessarily exactly the same as the first resonant frequency before frequency reduction. It can be understood that the first resonant frequency raised back to by the filter circuit can be a frequency obtained by the controller through methods such as acquisition, sampling, receiving, detection, or storage. It can be the overload resonant frequency of the filter circuit, or it can be a frequency calculated by the controller based on the current output current value of the inverter. The specific frequency can be set according to the application scenario.It is understandable that the first resonant frequency that the filter circuit here raises back to can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values.

[0013] By adopting this application, when the load of the power supply system meets the current operating state of the inverter, the switching frequency of multiple power switching transistors can be increased to the first switching frequency, so as to adjust the resonant frequency of the filter circuit through the first resonant branch to the first resonant frequency, thereby ensuring that the resonant frequency of the filter circuit meets the requirements of system stability. The control method is simple, flexible, and highly applicable, and improves the power supply efficiency of the system.

[0014] In conjunction with the first aspect or any possible implementation thereof, in a fifth possible implementation, the controller includes a state determination unit and a drive control unit, the state determination unit being connected to the inverter circuit via the drive control unit. The state determination unit can output a first state signal when the output current of the inverter is less than the overload current. The state determination unit can also output a second state signal when the output current of the inverter is greater than or equal to the overload current. The drive control unit can control the switching frequency of multiple power switches to a first switching frequency based on the first state signal, or control the switching frequency of multiple power switches to a second switching frequency based on the second state signal. It is understood that when the output current of the inverter is less than the overload current, it indicates that the current load condition meets the operating conditions of the inverter (e.g., the load is within the rated load range), and the controller can output a first state signal indicating that the current inverter circuit is in a rated operating state or rated operating mode, and control the switching frequency of the multiple power switches to the first switching frequency. When the switching frequency is the first switching frequency, the first resonant branch among the multiple resonant branches of the filter circuit has the smallest equivalent impedance. Resonance can be generated through the first resonant branch, thus adjusting the resonant frequency of the filter circuit to the first resonant frequency when the inverter circuit is in its rated operating state or rated operating mode. Alternatively, the filter circuit can control the switch (or other control methods) based on the indication of the first state signal to turn on the first resonant branch and disconnect other resonant branches (e.g., the second resonant branch). Resonance can then be generated through the first resonant branch, allowing the resonant frequency of the filter circuit to be adjusted to the first resonant frequency when the inverter circuit is in its rated operating state or rated operating mode, ensuring that the resonant frequency of the filter circuit meets grid connection requirements. Simultaneously, it can be understood that when the output current value of the inverter is greater than or equal to the overload current value, it indicates that the current load state does not meet the operating conditions of the inverter (e.g., the load increases and is in an overload state). The controller can output a second state signal to indicate that the current inverter circuit is in an overload operating state or overload operating mode, controlling the switching frequency of multiple power switches to decrease to the second switching frequency. When the switching frequency is the second switching frequency, the second resonant branch has the smallest equivalent impedance among the multiple resonant branches of the filter circuit. Resonance can be generated through the second resonant branch. Therefore, when the inverter circuit is in an overload operating state or overload operating mode, the resonant frequency of the filter circuit can be adjusted to the second resonant frequency through the second resonant branch. Alternatively, the filter circuit can control the switch (or other control methods) based on the indication of the second state signal to turn on the second resonant branch and disconnect other resonant branches (such as the first resonant branch). Resonance can be generated through the second resonant branch. Therefore, when the inverter circuit is in an overload operating state or overload operating mode, the resonant frequency of the filter circuit can be adjusted to the second resonant frequency through the second resonant branch, so that the resonant frequency of the filter circuit meets the grid connection requirements again.Here, the controller can output different status signals based on the output circuit value of the inverter to indicate the current working state of the inverter circuit, so as to control the inverter circuit to use different switching frequencies, and then adjust the resonant frequency of the filter circuit through different resonant branches. While ensuring system stability, it increases the power supply efficiency of the system, reduces losses, responds quickly, and the control method is simple.

[0015] In conjunction with the fifth possible implementation of the first aspect, in the sixth possible implementation, the state judgment unit can also be used to output a first reset signal when the switching frequency of the multiple power switches is the second switching frequency and the output current value of the inverter is less than the reset current value. The drive control unit can also control the switching frequency of the multiple power switches to the first switching frequency based on the first reset signal. It can be understood that when the output current value of the inverter is less than the reset current value, it indicates that the current load state once again meets the operating conditions of the inverter (e.g., the load is reduced to the rated load range). The controller can then output the first reset signal to indicate that the current inverter circuit has returned from an overload operating state or overload operating mode to a rated operating state or rated operating mode, and control the switching frequency of the multiple power switches to increase to the first switching frequency. When the switching frequency is raised back to the first switching frequency, the first resonant branch among the multiple resonant branches of the filter circuit has the smallest equivalent impedance. Resonance can be generated again through the first resonant branch. Then, when the inverter circuit returns to its rated operating state or mode, the resonant frequency of the filter circuit is readjusted to the first resonant frequency through the first resonant branch. Alternatively, the filter circuit can re-energize the first resonant branch and disconnect other resonant branches (e.g., the second resonant branch) based on the indication control switch (or other control methods) of the first reset signal. Resonance is generated through the first resonant branch, and when the inverter circuit returns to its rated operating state or mode, the resonant frequency of the filter circuit is adjusted to the first resonant frequency through the first resonant branch, ensuring that the resonant frequency of the filter circuit meets grid connection requirements again and improving power supply efficiency. Here, the raised first switching frequency can be equal to the first switching frequency before frequency reduction, or it can be a third switching frequency within the range of the first switching frequency; it is not necessarily exactly equal to the first switching frequency before frequency reduction. Here, the first switching frequency that the inverter circuit re-upgrades to can be a frequency greater than the current switching frequency of the inverter circuit (e.g., the second switching frequency). It can be a frequency obtained by the controller through methods such as acquisition, sampling, receiving, detection, or storage; it can be the switching frequency of multiple power switches in the inverter circuit under rated operating conditions; or it can be a frequency calculated by the controller based on the current output current value of the inverter device. The specific frequency can be set according to the application scenario. It can be understood that the first switching frequency that the inverter circuit re-upgrades to can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values. Here, the controller can re-upgrade the switching frequency of multiple power switches to the first switching frequency when the load of the power supply system once again meets the current operating state of the inverter device. This ensures system stability, increases system power supply efficiency, reduces losses, provides rapid response, and simplifies the control method.

[0016] In conjunction with the sixth possible implementation of the first aspect, in the seventh possible implementation, the variable filter unit includes a variable capacitor unit and a variable inductor unit, the variable capacitor unit and the variable inductor unit are connected in series, and the capacitor unit, the variable capacitor unit and the variable inductor unit satisfy the following:

[0017] Z11 < Z21

[0018] Z12>Z22

[0019] Here, Z11 is the equivalent impedance of the capacitor unit at the first switching frequency, Z21 is the equivalent impedance of the variable filter unit at the first switching frequency, Z12 is the equivalent impedance of the capacitor unit at the second switching frequency, and Z22 is the equivalent impedance of the variable filter unit at the second switching frequency. It can be understood that at the first switching frequency, the equivalent impedance Z11 of the capacitor unit is less than the equivalent impedance Z21 of the variable filter unit. The output current of the inverter circuit mainly flows through the first resonant branch formed by the capacitor unit, the first inductor unit, and the second inductor unit. The filter circuit performs filtering through the first resonant branch (e.g., an LCL filter circuit) and resonates at the first resonant frequency. At the second switching frequency, the equivalent impedance Z12 of the capacitor unit is greater than the equivalent impedance Z22 of the variable filter unit. The output current of the inverter circuit mainly flows through the second resonant branch formed by the variable filter unit, the first inductor unit, and the second inductor unit. The filter circuit performs filtering through the second resonant branch (e.g., an LLCL filter circuit) and resonates at the second resonant frequency.

[0020] By adopting this application, the filter circuit can be based on the switching frequency of multiple power switching transistors, using different resonant branches as filter circuits to generate resonance at different resonant frequencies, ensuring that the resonant frequency of the filter circuit meets the requirements of system stability, with rapid response, simple control method, improved system stability and safety, and strong applicability.

[0021] Secondly, this application provides a power supply system, which may include a power source and an inverter. The inverter includes an inverter circuit, a controller, and a filter circuit. The inverter circuit includes multiple power switching transistors connected in series or parallel. The filter circuit includes multiple resonant branches composed of an inductor unit and multiple parallel resonant units. Here, one end of the inverter circuit is connected to a DC power source, and the other end of the inverter circuit is connected to the power grid or a load through the filter circuit. The controller is connected to the inverter circuit.

[0022] In conjunction with the second aspect, in the first possible implementation, the power supply system may also include a transformer, through which the power source can be connected to an inverter.

[0023] In conjunction with the first possible implementation of the second aspect, in the second possible implementation, the power supply system may further include a combiner box, through which the transformer can be connected to the inverter.

[0024] In conjunction with the second possible implementation of the second aspect, in the third possible implementation, the power supply system may further include a DC bus, the transformer may be connected to the DC bus via a combiner box, and the DC bus may be connected to an inverter.

[0025] In conjunction with the third possible implementation of the second aspect, in the fourth possible implementation, the power supply system may further include a grid connection device, through which the inverter can be connected to the load.

[0026] In this application, the functional modules of the power supply system are composed in a variety of flexible ways, which can adapt to different power supply environments, improve the diversity of application scenarios of the power supply system, and enhance the adaptability of the power supply system.

[0027] Thirdly, this application provides a grid-connected control method for an inverter device. This control method is applicable to grid-connected inverter devices. The inverter device includes an inverter circuit, a controller, and a filter circuit. The inverter circuit includes multiple power switching transistors connected in series or parallel. The filter circuit includes multiple resonant branches composed of an inductor unit and multiple parallel resonant units. Here, one end of the inverter circuit is connected to a DC power supply, and the other end of the inverter circuit is connected to the power grid or a load through the filter circuit. The controller is connected to the inverter circuit. The method includes: detecting the output current value of the inverter device; adjusting the switching frequency of the multiple power switching transistors based on the output current value of the inverter device, so as to adjust the resonant frequency of the filter circuit through different resonant branches, so that the resonant frequency meets the grid connection requirements.

[0028] In this application, the controller can obtain the output current value of the inverter (through methods such as acquisition, collection, reception, detection, or storage). The output current value of the inverter can be the output current value of the inverter circuit, the output current value at the connection point between the inverter and the load (e.g., the grid connection point when the load is the power grid), or the output current value of the sampling point, which can be set according to the application scenario. Here, the controller can adjust the switching frequency of multiple power switches based on the output current value of the inverter. It can be understood that in different application scenarios (e.g., the inverter is equivalent to a voltage source in a grid-connected scenario), the controller can control the switching frequency of multiple power switches at different switching frequencies based on the output current value of the inverter to adjust the output power of the inverter to adapt to changes in the load, thereby ensuring normal power supply to the load. For example, in a scenario where the power supply system is overloaded (i.e., the load increases), the controller can reduce the switching frequency of multiple power switches. During the operation of an inverter, due to the high switching frequency of components (such as switching transistors) in the inverter circuit, the output current (or voltage) contains harmonics. A filter circuit is needed between the inverter circuit and the load to remove these harmonics. When the power supply system is connected to the grid, to maintain system stability, the resonant frequency of the filter circuit is typically required to be less than a certain value (e.g., 1 / 4 of the switching frequency). Here, the filter circuit consists of multiple resonant branches composed of an inductor unit and multiple parallel resonant units. The device can also adjust the resonant frequency of the filter circuit through different resonant branches. For example, in a power supply system overload scenario (i.e., increased load), the controller can reduce the switching frequency of multiple power switching transistors to adjust the resonant frequency of the filter circuit through multiple resonant units, thereby maintaining the stability of the power supply system.

[0029] In conjunction with the third aspect, in the first possible implementation, the switching frequencies of multiple power switches are adjusted based on the output current value of the inverter to adjust the resonant frequency of the filter circuit through different resonant branches. This includes: when the switching frequencies of the multiple power switches are different, resonance is achieved through the resonant branch with the lowest equivalent impedance among the multiple resonant branches to adjust the resonant frequency of the filter circuit. Here, when the controller adjusts the switching frequencies of the multiple power switches, it simultaneously changes the magnitude of the equivalent impedance in the multiple resonant branches. Different resonant branches (e.g., a first resonant branch composed of a capacitor unit and an inductor unit, and a second resonant branch composed of a variable filter unit and an inductor unit) have different equivalent impedances at different switching frequencies. When the controller adjusts the switching frequencies of the multiple power switches, the current mainly flows through the resonant branch with the lowest equivalent impedance at the current switching frequency, causing the resonant branch with the lowest equivalent impedance to resonate at the resonant frequency corresponding to the current switching frequency. Therefore, based on the different switching frequencies of the inverter circuit, the filter circuit can adjust its resonant frequency through different resonant branches.

[0030] By employing this application, when the switching frequency of multiple power switching transistors in the inverter circuit decreases due to power system overload, resonance can be achieved through the resonant branch with the lowest equivalent impedance among multiple resonant branches. This allows for timely adjustment of the resonant frequency of the filter circuit, enhancing the load-carrying capacity of the device while ensuring that the resonant frequency of the filter circuit meets the system stability requirements. The application is characterized by rapid response, simple control method, improved system stability and safety, and strong applicability.

[0031] In conjunction with the first possible implementation of the third aspect, in the second possible implementation, the multiple resonant units include a capacitor unit and at least one variable filter unit. The inductor unit includes a first inductor unit and a second inductor unit, which are connected in series between the inverter circuit and the load. The capacitor unit and the variable filter unit are connected in parallel between the first inductor unit and the second inductor unit. The capacitor unit and the inductor unit form a first resonant branch, and the variable filter unit and the inductor unit form a second resonant branch. After detecting the output current value of the inverter, the method further includes: when the output current value of the inverter is less than the overload current value, adjusting the switching frequency of the multiple power switches to a first switching frequency, so as to adjust the resonant frequency of the filter circuit to the first resonant frequency through the first resonant branch. Here, when the switching frequency is the first switching frequency, the equivalent impedance of the first resonant branch is less than the equivalent impedance of the second resonant branch. Here, the first resonant frequency is less than the first stable frequency, which is the grid-connected stable frequency corresponding to the first switching frequency (for example, the first stable frequency is 1 / 4 of the first switching frequency).

[0032] It is understandable that after the controller obtains the output current value of the inverter (through methods such as acquisition, sampling, receiving, detection, or storage), the controller can control the switching frequency of multiple power switches based on the output current value of the inverter. When the output current value of the inverter is less than the overload current value, it indicates that the current load condition meets the operating conditions of the inverter (e.g., the load is within the rated load range), and the controller can adjust the switching frequency of the multiple power switches to a first switching frequency. Here, the first switching frequency can be the current switching frequency of the inverter circuit, the frequency obtained by the controller through methods such as acquisition, sampling, receiving, detection, or storage, the switching frequency of the multiple power switches in the inverter circuit under rated operating conditions, or the frequency calculated by the controller based on the current output current value of the inverter. The specific frequency can be set according to the application scenario. It is understandable that the first switching frequency can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values. Here, among multiple resonant branches, the first resonant branch, composed of capacitor and inductor units (e.g., the first and second inductor units), has the smallest equivalent impedance when the switching frequency of the multiple power switches is the first switching frequency. Current mainly flows through this first resonant branch, causing it to resonate at the resonant frequency corresponding to the first switching frequency (i.e., the first resonant frequency). In other words, when the inverter's output current is less than the overload current, the resonant frequency of the filter circuit can be adjusted to the first resonant frequency based on the switching frequency of the multiple power switches (i.e., the first switching frequency). Here, the first resonant frequency is less than the first stable frequency, which is the grid-connected stable frequency corresponding to the first switching frequency (e.g., 1 / 4 of the first switching frequency). During grid connection of the power supply system, to meet system stability requirements, the first resonant frequency needs to be less than a certain grid-connected stable frequency (e.g., 1 / 4 of the first switching frequency). It is understandable that the value of the first resonant frequency here can be determined based on the current resonant frequency of the filter circuit. This could be a frequency obtained by the controller through methods such as acquisition, sampling, receiving, detection, or storage; it could be the rated resonant frequency of the filter circuit; or it could be a frequency calculated by the controller based on the current output current value of the inverter. The specific setting depends on the application scenario. It is also understandable that the first resonant frequency here can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values.

[0033] By using this application, when the load of the power supply system meets the current operating state of the inverter, the switching frequency of multiple power switching transistors can be adjusted to the first switching frequency, so as to adjust the resonant frequency of the filter circuit to the first resonant frequency through the first resonant branch, so as to ensure that the resonant frequency of the filter circuit meets the requirements of system stability. The control method is simple, flexible and highly applicable.

[0034] In conjunction with the second possible implementation of the third aspect, in the third possible implementation, after detecting the output current value of the inverter, the method further includes: when the output current value of the inverter is greater than or equal to the overload current value, reducing the switching frequency of multiple power switches to a second switching frequency to enhance the load-carrying capacity of the inverter, and adjusting the resonant frequency of the filter circuit to a second resonant frequency through the second resonant branch. Here, the second switching frequency is less than the first switching frequency, and when the switching frequency is the second switching frequency, the equivalent impedance of the second resonant branch is less than the equivalent impedance of the first resonant branch. Here, the second switching frequency is less than the first switching frequency and less than the first resonant frequency, the second resonant frequency is less than the second stable frequency, and the second stable frequency is the grid-connected stable frequency corresponding to the second switching frequency.

[0035] It is understandable that after the controller obtains the output current value of the inverter (through methods such as acquisition, sampling, receiving, detection, or storage), the controller can control the switching frequency of multiple power switches based on the output current value of the inverter. When the output current value of the inverter is greater than or equal to the overload current value, it indicates that the current load condition does not meet the operating conditions of the inverter (e.g., the load has increased and is in an overload state). The controller can then reduce the switching frequency of multiple power switches to a second switching frequency to enhance the load-carrying capacity of the inverter, and adjust the resonant frequency of the filter circuit to a second resonant frequency through the second resonant branch. Here, the second switching frequency is less than the first switching frequency, and when the switching frequency is the second switching frequency, the equivalent impedance of the second resonant branch is less than the equivalent impedance of the first resonant branch. Here, the second switching frequency can be a frequency lower than the current switching frequency of the inverter circuit (e.g., the second switching frequency). It can be a frequency obtained by the controller through methods such as acquisition, sampling, receiving, detection, or storage; it can be the switching frequency of multiple power switches in the inverter circuit under overload conditions; or it can be a frequency calculated by the controller based on the current output current value of the inverter. The specific frequency can be set according to the application scenario. It can be understood that the second switching frequency here can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values. Here, among the multiple resonant branches, the second resonant branch composed of the variable filter unit and the inductor unit (e.g., the first inductor unit and the second inductor unit) has the lowest equivalent impedance when the switching frequency of the multiple power switches is the second switching frequency. Current mainly flows through the second resonant branch composed of the variable filter unit and the inductor unit (e.g., the first inductor unit and the second inductor unit), causing the second resonant branch to resonate at the resonant frequency corresponding to the second switching frequency (i.e., the second resonant frequency). In other words, when the output current of the inverter is greater than or equal to the overload current, the resonant frequency of the filter circuit can be reduced to a second resonant frequency by using the second resonant branch based on the switching frequencies of multiple power switches (i.e., the second switching frequency). Here, the second resonant frequency is less than the second stable frequency and less than the first resonant frequency. The second stable frequency is the grid-connected stable frequency corresponding to the second switching frequency (for example, the second stable frequency is 1 / 4 of the second switching frequency). During the grid connection process of the power supply system, in order to meet the system stability requirements, the second resonant frequency needs to be less than a certain grid-connected stable frequency (for example, 1 / 4 of the second switching frequency). It can be understood that the value of the second resonant frequency here can be determined based on the current resonant frequency of the filter circuit. It can be a frequency obtained by the controller through methods such as acquisition, collection, reception, detection, or storage; it can be the overload resonant frequency of the filter circuit; or it can be a frequency calculated by the controller based on the current output current value of the inverter. The specific value can be set according to the application scenario.It is understandable that the second resonant frequency here can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values.

[0036] By adopting this application, when the load of the power supply system increases and the current inverter is in an overloaded operating state, the switching frequency of multiple power switching transistors can be reduced to a second switching frequency, so as to adjust the resonant frequency of the filter circuit through the second resonant branch to a second resonant frequency, thereby ensuring that the resonant frequency of the filter circuit meets the requirements of system stability. The control method is simple, flexible and highly applicable.

[0037] In conjunction with the third possible implementation of the third aspect, in the fourth possible implementation, after adjusting the resonant frequency of the filter circuit to the second resonant frequency via the variable filter unit, the method further includes: when the output current value of the inverter is less than the reset current value, increasing the switching frequency of the plurality of power switches to a first switching frequency, so as to adjust the resonant frequency of the filter circuit to the first resonant frequency via the first resonant branch. Here, the reset current value is less than or equal to the overload current value.

[0038] It is understandable that after the controller controls the switching frequency of multiple power switches to the second switching frequency, the controller can also obtain the output current value of the inverter (through methods such as acquisition, sampling, receiving, detection, or storage). The controller can also control the switching frequency of the multiple power switches based on the output current value of the inverter. When the switching frequency of the multiple power switches is the second switching frequency and the output current value of the inverter is less than the reset current value, it indicates that the current load state once again meets the operating conditions of the inverter (e.g., the load is reduced to the rated load range). The controller can then increase the switching frequency of the multiple power switches to the first switching frequency. Here, the increased first switching frequency can be equal to the first switching frequency before the frequency reduction, or it can be a third switching frequency within the first switching frequency range; it is not necessarily exactly equal to the first switching frequency before the frequency reduction. Here, the first switching frequency that the inverter circuit re-raises to can be a frequency greater than the current switching frequency of the inverter circuit (e.g., the second switching frequency). It can be a frequency obtained by the controller through methods such as acquisition, sampling, receiving, detection, or storage; it can be the switching frequency of multiple power switches in the inverter circuit under rated operating conditions; or it can be a frequency calculated by the controller based on the current output current value of the inverter device. The specific frequency can be set according to the application scenario. It can be understood that the first switching frequency that the inverter circuit re-raises to can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values. Correspondingly, when the output current value of the inverter device is less than the reset current value, the resonant frequency of the filter circuit can be re-raised to the first resonant frequency through the first resonant branch based on the switching frequencies of the multiple power switches (i.e., the first switching frequency). Here, the first resonant frequency that the filter circuit re-raises to can be equal to the first resonant frequency before frequency reduction, or it can be a third resonant frequency within the range of the first resonant frequency; it is not necessarily exactly equal to the first resonant frequency before frequency reduction. It is understandable that the first resonant frequency that the filter circuit re-emerges to can be a frequency obtained by the controller through methods such as acquisition, sampling, receiving, detection, or storage. It can be the overload resonant frequency of the filter circuit, or a frequency calculated by the controller based on the current output current value of the inverter. The specific frequency can be set according to the application scenario. It is also understood that the first resonant frequency that the filter circuit re-emerges to can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values.

[0039] By adopting this application, when the load of the power supply system meets the current operating state of the inverter, the switching frequency of multiple power switching transistors can be increased to the first switching frequency, so as to adjust the resonant frequency of the filter circuit through the first resonant branch to the first resonant frequency, thereby ensuring that the resonant frequency of the filter circuit meets the requirements of system stability. The control method is simple, flexible, and highly applicable, and improves the power supply efficiency of the system.

[0040] In conjunction with any possible implementation of the third aspect, in the fifth possible implementation, the controller includes a state judgment unit and a drive control unit. After detecting the output current value of the inverter, the method further includes: outputting a first state signal when the output current value of the inverter is less than the overload current value; and outputting a second state signal when the output current value of the inverter is greater than or equal to the overload current value. The switching frequency of multiple power switches is controlled to a first switching frequency based on the first state signal, or the switching frequency of multiple power switches is controlled to a second switching frequency based on the second state signal. It can be understood that when the output current value of the inverter is less than the overload current value, it indicates that the current load state meets the operating conditions of the inverter (e.g., the load is within the rated load range). Here, the controller can output a first state signal to indicate that the current inverter circuit is in a rated operating state or rated operating mode, and control the switching frequency of multiple power switches to the first switching frequency. When the switching frequency is the first switching frequency, the first resonant branch among the multiple resonant branches of the filter circuit has the smallest equivalent impedance. The filter circuit can generate resonance through the first resonant branch based on the fact that the equivalent impedance of the first resonant branch is the smallest at the first switching frequency. Then, when the inverter circuit is in the rated operating state or rated operating mode, the resonant frequency of the filter circuit can be adjusted to the first resonant frequency through the first resonant branch. Alternatively, the filter circuit can control the switch (or other control method) based on the indication of the first state signal to turn on the first resonant branch and disconnect other resonant branches (such as the second resonant branch). Resonance can be generated through the first resonant branch. Then, when the inverter circuit is in the rated operating state or rated operating mode, the resonant frequency of the filter circuit can be adjusted to the first resonant frequency through the first resonant branch, so that the resonant frequency of the filter circuit meets the grid connection requirements. It can also be understood that when the output current of the inverter is greater than or equal to the overload current, it indicates that the current load condition does not meet the operating conditions of the inverter (e.g., the load increases and it is in an overload state). The controller can output a second status signal to indicate that the current inverter circuit is in an overload operating state or overload operating mode, and control the switching frequency of multiple power switches to the second switching frequency. When the switching frequency is the second switching frequency, the equivalent impedance of the second resonant branch among the multiple resonant branches of the filter circuit is the smallest. Resonance can be generated through the second resonant branch, and then when the inverter circuit is in an overload operating state or overload operating mode, the resonant frequency of the filter circuit can be adjusted to the second resonant frequency through the second resonant branch. Alternatively, the filter circuit can also control the switch (or other control methods) based on the indication of the second status signal to turn on the second resonant branch and disconnect other resonant branches (e.g., the first resonant branch), generating resonance through the second resonant branch. Then, when the inverter circuit is in an overload operating state or overload operating mode, the resonant frequency of the filter circuit can be adjusted to the second resonant frequency through the second resonant branch, so that the resonant frequency of the filter circuit meets the grid connection requirements again.Here, the controller can output different status signals based on the output circuit value of the inverter to indicate the current working state of the inverter circuit, so as to control the inverter circuit to use different switching frequencies, and then adjust the resonant frequency of the filter circuit through different resonant branches. While ensuring system stability, it increases the power supply efficiency of the system, reduces losses, responds quickly, and the control method is simple.

[0041] In conjunction with the fifth possible implementation of the third aspect, in the sixth possible implementation, after controlling the switching frequency of the multiple power switches to the second switching frequency based on the second state signal, the method further includes: outputting a first reset signal when the output current value of the inverter is less than the reset current value. The switching frequency of the multiple power switches is controlled to the first switching frequency based on the first reset signal. It can be understood that when the output current value of the inverter is less than the reset current value, it indicates that the current load state once again meets the operating conditions of the inverter (e.g., the load has decreased to within the rated load range). Here, the controller can output the first reset signal to indicate that the current inverter circuit has returned from an overload operating state or overload operating mode to a rated operating state or rated operating mode, controlling the switching frequency of the multiple power switches to increase to the first switching frequency. When the switching frequency is raised back to the first switching frequency, the first resonant branch among the multiple resonant branches of the filter circuit has the smallest equivalent impedance. Resonance can be generated again through the first resonant branch. Then, when the inverter circuit returns to its rated operating state or mode, the resonant frequency of the filter circuit is readjusted to the first resonant frequency through the first resonant branch. Alternatively, the filter circuit can re-energize the first resonant branch and disconnect other resonant branches (e.g., the second resonant branch) based on the indication control switch (or other control methods) of the first reset signal. Resonance is generated through the first resonant branch, and when the inverter circuit returns to its rated operating state or mode, the resonant frequency of the filter circuit is adjusted to the first resonant frequency through the first resonant branch, ensuring that the resonant frequency of the filter circuit meets grid connection requirements again and improving power supply efficiency. Here, the raised first switching frequency can be equal to the first switching frequency before frequency reduction, or it can be a third switching frequency within the range of the first switching frequency; it is not necessarily exactly equal to the first switching frequency before frequency reduction. Here, the first switching frequency that the inverter circuit re-upgrades to can be a frequency greater than the current switching frequency of the inverter circuit (e.g., the second switching frequency). It can be a frequency obtained by the controller through methods such as acquisition, sampling, receiving, detection, or storage; it can be the switching frequency of multiple power switches in the inverter circuit under rated operating conditions; or it can be a frequency calculated by the controller based on the current output current value of the inverter device. The specific frequency can be set according to the application scenario. It can be understood that the first switching frequency that the inverter circuit re-upgrades to can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values. Here, the controller can re-upgrade the switching frequency of multiple power switches to the first switching frequency when the load of the power supply system once again meets the current operating state of the inverter device. This ensures system stability, increases system power supply efficiency, reduces losses, provides rapid response, and simplifies the control method. Attached Figure Description

[0042] Figure 1 This is a schematic diagram illustrating an application scenario of the inverter device provided in the embodiments of this application;

[0043] Figure 2 This is a schematic diagram of the inverter device provided in an embodiment of this application;

[0044] Figure 3 This is another structural schematic diagram of the inverter device provided in the embodiments of this application;

[0045] Figure 4 This is another structural schematic diagram of the inverter device provided in the embodiments of this application;

[0046] Figure 5 This is another structural schematic diagram of the inverter device provided in the embodiments of this application;

[0047] Figure 6 This is a schematic diagram of the power supply system provided in an embodiment of this application;

[0048] Figure 7 This is another structural schematic diagram of the power supply system provided in the embodiments of this application;

[0049] Figure 8 This is another structural schematic diagram of the power supply system provided in the embodiments of this application;

[0050] Figure 9 This is a flowchart illustrating a grid connection control method provided in an embodiment of this application;

[0051] Figure 10 This is another schematic flowchart of the grid connection control method provided in the embodiments of this application. Detailed Implementation

[0052] The grid-connected inverter device provided in this application is applicable to power supply systems in various application fields, including power supply systems in the fields of new energy smart microgrids, power transmission and distribution, new energy (such as photovoltaic grid-connected, thermal power grid-connected, or wind power grid-connected), photovoltaic power generation, wind power generation, thermal power generation, and high-power converters (such as converting DC to high-power high-voltage AC). The specific application can be determined according to the actual application scenario, and no limitations are imposed here. The inverter device provided in this application can be adapted to different application scenarios, such as power supply scenarios for loads in photovoltaic-storage power supply environments, wind-storage power supply environments, pure energy storage power supply environments, or other application scenarios. The following explanation will use the application scenario of powering loads in a pure energy storage power supply environment as an example; further details will not be elaborated upon here.

[0053] Please see Figure 1 , Figure 1 This is a schematic diagram illustrating an application scenario of the inverter device provided in this application embodiment. In a pure energy storage power supply application scenario, such as... Figure 1 As shown, the power supply system includes an inverter 1, a power source 2 (i.e., DC voltage), and a power grid 3. Here, the two ends of the inverter 1 are connected to the power source 2 and the power grid 3, respectively. In some feasible implementations, the power source 2 can supply power to the power grid 3 through the inverter 1. In some feasible implementations, the power source 2 can also serve as an energy storage device; when power is not scarce, the power source 2 can obtain and store electrical energy provided by the power grid 3 through the inverter 1. This application only describes the application scenario of the power source 2 supplying power to the power grid 3 through the inverter 1 as an example, and will not be elaborated further below. It can be understood that the power source 2 provided in this application is also suitable for supplying power to loads in the power grid 3 or directly supplying power to loads, such as powering base station equipment in remote areas without mains power or with poor mains power, or powering batteries, or powering household appliances (such as refrigerators, air conditioners, etc.), etc., in application scenarios that supply power to various types of electrical equipment. The specific application scenario can be determined according to the actual application scenario, and no restrictions are imposed here. Furthermore, it can be understood that... Figure 1The power grid 3 in the diagram may include power transmission lines, power transfer stations, batteries, communication base stations, or household appliances and other electrical equipment or power transmission equipment. Here, the inverter 1 may include an inverter circuit 11, a controller 10, and a filter circuit 12. One end of the inverter circuit 11 can be connected to a power source, and the other end of the inverter circuit 11 can be connected to the power grid 3 via the filter circuit 12. The controller 10 can be connected to the inverter circuit 11. In some feasible embodiments, the system may become overloaded due to changes in the load of the power grid 3 during operation (e.g., an increase in the load of the power grid 3). In this application, the load can refer to the load of the power grid 3, or it can be a load directly connected to the power supply system, depending on the application scenario. Here, we only describe it as an example of the load being the load of the power grid 3, and will not elaborate further. Here, the controller 10 can obtain the output current value of the inverter 1 (through methods such as acquisition, collection, reception, detection, or storage). The output current value of inverter 1 can be the output current value of inverter circuit 11, the output current value at the connection point between inverter 1 and grid 3 (e.g., grid connection point), or the output current value of sampling point, depending on the application scenario. It can be understood that in different application scenarios (e.g., inverter 1 is equivalent to a voltage source in a grid-connected scenario), controller 10 can control the switching frequency of multiple power switches in inverter circuit 11 at different switching frequencies based on the output current value of inverter 1, thereby adjusting the output power of inverter 1 to adapt to changes at grid 3 and ensuring normal power supply to grid 3. For example, in a scenario of power system overload (i.e., increased load on grid 3), controller 10 can reduce the switching frequency of multiple power switches in inverter circuit 11. Here, inverter circuit 11 includes multiple power switches connected in series or parallel. During the operation of inverter 1, due to the high switching frequency of components (e.g., switching transistors) in inverter circuit 11, the output current (or voltage) of inverter circuit 11 contains harmonics. Therefore, a filter circuit 12 needs to be installed between inverter circuit 11 and the power grid 3 to filter out the harmonics in the output current (or voltage) of inverter circuit 11. Here, filter circuit 12 includes multiple resonant branches composed of an inductor unit and multiple parallel resonant units. During grid connection of the power supply system, to maintain system stability, the resonant frequency of filter circuit 12 is usually required to be less than a certain value (e.g., the grid connection stability frequency). Here, when inverter circuit 11 changes the switching frequency of multiple switching transistors, to ensure system stability (e.g., the resonant frequency is less than the grid connection stability frequency required for grid connection), filter circuit 12 can also adjust the resonant frequency through different resonant branches.The filter circuit 12 here can resonate through the resonant branch with the lowest equivalent impedance among multiple resonant branches when the switching frequencies of multiple power switches are different, thereby adjusting the resonant frequency of the filter circuit 12. Here, when the controller adjusts the switching frequencies of multiple power switches, it synchronously changes the magnitude of the equivalent impedance in multiple resonant branches. Here, different resonant branches (e.g., ...) Figure 1 The first resonant branch, composed of resonant unit a and inductor unit, is shown by the solid gray arrow. Figure 1 As indicated by the gray solid and dashed arrows, the second resonant branch (composed of resonant unit n and inductor unit) has different equivalent impedances at different switching frequencies. When the controller 10 adjusts the switching frequencies of multiple power switches, the current mainly flows through the resonant branch with the smallest equivalent impedance at the current switching frequency, causing the resonant branch with the smallest equivalent impedance to resonate at the resonant frequency corresponding to the current switching frequency. Therefore, based on the different switching frequencies of the inverter circuit 11, the filter circuit 12 can adjust the resonant frequency through different resonant branches. In other words, in a scenario of power system overload (i.e., increased load on grid 3), the controller 10 can reduce the switching frequencies of multiple power switches in the inverter circuit 11, and thus the multiple resonant units can adjust the resonant frequency of the filter circuit 12 to ensure that the resonant frequency of the filter circuit 12 meets grid connection requirements and maintains the stability of the power supply system.

[0054] By employing this application, when the switching frequency of multiple power switching transistors in the inverter circuit decreases due to power system overload, resonance can be achieved through the resonant branch with the lowest equivalent impedance among multiple resonant branches. This allows for timely adjustment of the resonant frequency of the filter circuit, enhancing the load-carrying capacity of the device while ensuring that the resonant frequency of the filter circuit meets the requirements of the system's grid-connected stability. The application features rapid response, simple control method, improved system stability and safety, and strong applicability.

[0055] The following will combine Figures 2 to 10 The inverter device, power supply system and their working principle provided in this application are illustrated with examples.

[0056] Please see Figure 2 , Figure 2 This is a schematic diagram of the inverter device provided in an embodiment of this application. Figure 2As shown, the inverter device includes an inverter circuit 101, a controller 100, and a filter circuit 102. Here, the multiple resonant units may include capacitor units and at least one variable filter unit (e.g., variable filter units a to n). The inductor units may include a first inductor unit L1 and a second inductor unit L2. The first inductor unit L1 and the second inductor unit L2 can be connected in series between the inverter circuit and the load. The capacitor unit and the variable filter unit (e.g., variable filter units a to n) can be connected in parallel between the first inductor unit L1 and the second inductor unit L2. The capacitor unit and the inductor unit can form a first resonant branch, and the variable filter unit (e.g., variable filter unit a) and the inductor unit can form a second resonant branch. The controller 100 can also be used to adjust the switching frequency of multiple power switches in the inverter circuit 101 to a first switching frequency when the output current value of the inverter device is less than the overload current value, so as to adjust the resonant frequency of the filter circuit 102 to the first resonant frequency through the first resonant branch. Here, when the switching frequency is the first switching frequency, the equivalent impedance of the first resonant branch is less than the equivalent impedance of the second resonant branch. Here, the first resonant frequency is less than the first stable frequency, which is the grid-connected stable frequency corresponding to the first switching frequency (e.g., the first stable frequency is 1 / 4 of the first switching frequency). It can be understood that after the controller 100 obtains the output current value of the inverter (through methods such as acquisition, sampling, receiving, detection, or storage), the controller 100 can control the switching frequency of the multiple power switches in the inverter circuit 101 based on the output current value of the inverter. When the output current value of the inverter is less than the overload current value, it indicates that the current load condition meets the operating conditions of the inverter (e.g., the load is within the rated load range), and the controller 100 can adjust the switching frequency of the multiple power switches in the inverter circuit 101 to the first switching frequency. Here, the first switching frequency can be the current switching frequency of the inverter circuit 101, the frequency obtained by the controller 100 through methods such as acquisition, collection, reception, detection, or storage, the switching frequency of multiple power switches in the inverter circuit 101 under rated operating conditions, or the frequency calculated by the controller 100 based on the current output current value of the inverter device. The specific frequency can be set according to the application scenario. It can be understood that the first switching frequency here can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values.Here, among the multiple resonant branches, the first resonant branch, composed of capacitor units and inductor units (e.g., first inductor unit L1 and second inductor unit L2), has the smallest equivalent impedance when the switching frequency of the multiple power switches is the first switching frequency. Current mainly flows through this first resonant branch, causing it to resonate at the resonant frequency corresponding to the first switching frequency (i.e., the first resonant frequency). In other words, when the output current of the inverter is less than the overload current, the resonant frequency of the filter circuit 102 can be adjusted to the first resonant frequency through the first resonant branch. Here, the first resonant frequency is less than the first stable frequency, which is the grid-connected stable frequency corresponding to the first switching frequency (e.g., the first stable frequency is 1 / 4 of the first switching frequency). During grid connection of the power supply system, to meet the system's stability requirements, the first resonant frequency needs to be less than a certain grid-connected stable frequency (e.g., 1 / 4 of the first switching frequency). It is understandable that the value of the first resonant frequency here can be determined based on the current resonant frequency of the filter circuit 102. It can be a frequency obtained by the controller 100 through methods such as acquisition, sampling, receiving, detection, or storage; it can be the rated resonant frequency of the filter circuit 102; or it can be a frequency calculated by the controller 100 based on the current output current value of the inverter. The specific setting can be determined according to the application scenario. It is also understandable that the first resonant frequency here can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values.

[0057] By using this application, when the load of the power supply system meets the current operating state of the inverter device, the switching frequency of multiple power switching transistors in the inverter circuit 101 can be adjusted to the first switching frequency, so as to adjust the resonant frequency of the filter circuit 102 through the first resonant branch to the first resonant frequency, so as to ensure that the resonant frequency of the filter circuit 102 meets the requirements of system stability. The control method is simple, flexible and highly applicable.

[0058] In some feasible implementations, the controller 100 can also be used to reduce the switching frequency of multiple power switches in the inverter circuit 101 to a second switching frequency when the output current value of the inverter is greater than or equal to the overload current value, thereby enhancing the load-carrying capacity of the inverter, and to adjust the resonant frequency of the filter circuit 102 to a second resonant frequency through the second resonant branch. Here, the second switching frequency is less than the first switching frequency, and when the switching frequency is the second switching frequency, the equivalent impedance of the second resonant branch is less than the equivalent impedance of the first resonant branch. Here, the second resonant frequency is less than the second stable frequency and less than the first resonant frequency, and the second stable frequency is the grid-connected stable frequency corresponding to the second switching frequency (for example, the second stable frequency is 1 / 4 of the second switching frequency). It can be understood that after the controller 100 obtains the output current value of the inverter (by means of, for example, acquiring, collecting, receiving, detecting, or storing), the controller 100 can control the switching frequency of multiple power switches in the inverter circuit 101 based on the output current value of the inverter. When the output current of the inverter is greater than or equal to the overload current, it indicates that the current load condition does not meet the operating conditions of the inverter (e.g., the load is increased and in an overload state). The controller 100 can then reduce the switching frequency of the multiple power switches in the inverter circuit 101 to a second switching frequency. Here, the second switching frequency is less than the first switching frequency. The second switching frequency can be a frequency less than the current switching frequency of the inverter circuit 101 (e.g., the second switching frequency), a frequency obtained by the controller 100 through methods such as acquisition, sampling, receiving, detection, or storage, the switching frequency of the multiple power switches in the inverter circuit 101 in an overload operating state, or a frequency calculated by the controller 100 based on the current output current of the inverter. The specific frequency can be set according to the application scenario. It can be understood that the second switching frequency can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values. Here, among the multiple resonant branches, the second resonant branch, composed of a variable filter unit (e.g., variable filter unit a) and an inductor unit (e.g., first inductor unit L1 and second inductor unit L2), has the smallest equivalent impedance when the switching frequency of the multiple power switches is the second switching frequency. Current mainly flows through this second resonant branch, causing it to resonate at the resonant frequency corresponding to the second switching frequency (i.e., the second resonant frequency). In other words, when the output current of the inverter is greater than or equal to the overload current, the resonant frequency of the filter circuit 102 can be reduced to the second resonant frequency by the second resonant branch based on the switching frequency (i.e., the second switching frequency) of the multiple power switches in the inverter circuit 101.Here, the second resonant frequency is less than the second stable frequency and less than the first resonant frequency. The second stable frequency is the grid-connected stable frequency corresponding to the second switching frequency (for example, the second stable frequency is 1 / 4 of the second switching frequency). During the grid connection process of the power supply system, in order to meet the system stability requirements, the second resonant frequency needs to be less than a certain grid-connected stable frequency (for example, 1 / 4 of the second switching frequency). It can be understood that the value of the second resonant frequency here can be determined based on the current resonant frequency of the filter circuit 102. It can be a frequency obtained by the controller 100 through methods such as acquisition, collection, reception, detection, or storage; it can be the overload resonant frequency of the filter circuit 102; or it can be a frequency calculated by the controller 100 based on the current output current value of the inverter. The specific value can be set according to the application scenario. It can be understood that the second resonant frequency here can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values.

[0059] By employing this application, when the load of the power supply system increases, causing the current inverter device to operate under overload conditions, the switching frequency of multiple power switching transistors in the inverter circuit 101 can be reduced to a second switching frequency. The resonant frequency of the filter circuit 102 can then be adjusted based on the switching frequency of the multiple power switching transistors in the inverter circuit 101 through the second resonant branch, thereby ensuring that the resonant frequency of the filter circuit 102 meets the requirements of system stability. The control method is simple, flexible, and highly applicable.

[0060] In some feasible implementations, the controller 100 can also be used to increase the switching frequency of the multiple power switches in the inverter circuit 101 to a first switching frequency when the switching frequency of the multiple power switches in the inverter circuit 101 is a second switching frequency and the output current value of the inverter is less than the reset current value. This is done so that the resonant frequency of the filter circuit 102 is adjusted to the first resonant frequency based on the switching frequency of the multiple power switches in the inverter circuit 101 via the first resonant branch. Here, the reset current value is less than or equal to the overload current value. It can be understood that after the controller 100 controls the switching frequency of the multiple power switches in the inverter circuit 101 to the second switching frequency, the controller 100 can also obtain the output current value of the inverter (e.g., by acquiring, collecting, receiving, detecting, or storing), and the controller 100 can also control the switching frequency of the multiple power switches in the inverter circuit 101 based on the output current value of the inverter. When the switching frequency of multiple power switches in inverter circuit 101 is the second switching frequency and the output current of the inverter is less than the reset current, it indicates that the current load condition once again meets the operating conditions of the inverter (e.g., the load is reduced to the rated load range). Controller 100 can then increase the switching frequency of the multiple power switches in inverter circuit 101 to the first switching frequency. Here, the increased first switching frequency can be equal to the first switching frequency before the frequency reduction, or it can be a third switching frequency within the first switching frequency range; it is not necessarily exactly the same as the first switching frequency before the frequency reduction. The increased first switching frequency can be a frequency greater than the current switching frequency of inverter circuit 101 (e.g., the second switching frequency), a frequency obtained by controller 100 through methods such as acquisition, sampling, receiving, detection, or storage, the switching frequency of the multiple power switches in inverter circuit 101 in the rated state, or a frequency calculated by controller 100 based on the current output current of the inverter. The specific frequency can be set according to the application scenario. It is understandable that the first switching frequency that the inverter circuit 101 raises back to can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values. Correspondingly, when the output current of the inverter is less than the reset current, the resonant frequency of the filter circuit 102 can be raised back to the first resonant frequency through the first resonant branch based on the switching frequencies (i.e., the first switching frequency) of the multiple power switches in the inverter circuit 101. Here, the first resonant frequency that the filter circuit 102 raises back to can be equal to the first resonant frequency before frequency reduction, or it can be a third resonant frequency within the range of the first resonant frequency; it is not necessarily exactly equal to the first resonant frequency before frequency reduction.It is understood that the first resonant frequency that the filter circuit 102 re-raises can be a frequency obtained by the controller 100 through methods such as acquisition, sampling, receiving, detection, or storage; it can be the overload resonant frequency of the filter circuit 102; or it can be a frequency calculated by the controller 100 based on the current output current value of the inverter. The specific frequency can be set according to the application scenario. It is also understood that the first resonant frequency that the filter circuit 102 re-raises can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values.

[0061] By employing this application, when the load of the power supply system meets the current operating state of the inverter device again, the switching frequency of multiple power switches in the inverter circuit 101 can be raised to the first switching frequency. The resonant frequency of the filter circuit 102 can then be adjusted to the first resonant frequency based on the switching frequency of the multiple power switches in the inverter circuit 101 through the first resonant branch. This ensures that the resonant frequency of the filter circuit 102 meets the requirements of system stability. The control method is simple, flexible, and highly applicable, thereby improving the power supply efficiency of the system.

[0062] Please continue reading Figure 2 In some feasible implementations, when the load further increases, the controller 100 can further reduce the switching frequency of the multiple power switches in the inverter circuit 101. When the switching frequency of the multiple power switches in the inverter circuit 101 is the fourth switching frequency (here, the fourth switching frequency is less than the second switching frequency), the filter circuit 102 can (by controlling a switch, or by controlling a selector, or by other means such as different unit impedances or capacitive reactances) use a variable filter unit (e.g., a variable filter unit n) to form other resonant branches (e.g., a third resonant branch) with the first inductor unit L1 and the second inductor unit L2, generating resonance at the fourth resonant frequency (here, the fourth resonant frequency is less than the second resonant frequency). It can be understood that the fourth resonant frequency here can be a frequency obtained by the controller 100 through means such as acquisition, collection, reception, detection, or storage, it can be a certain overload resonant frequency of the filter circuit 102, or it can be a frequency calculated by the controller 100 based on the current output current value of the inverter device, and can be specifically set according to the application scenario. It is understandable that the fourth resonant frequency here can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values.

[0063] By using this application, the filter circuit 102 can be based on the switching frequency of multiple power switches in the inverter circuit 101, and different resonant branches can be used as filter circuits 102 to generate resonance at different resonant frequencies, ensuring that the resonant frequency of the filter circuit 102 meets the requirements of system stability, with rapid response, simple control method, improved system stability and safety, and strong applicability.

[0064] In some feasible implementations, the controller may include a state determination unit and a drive control unit; please refer to the following for details. Figure 3 , Figure 3 This is another structural schematic diagram of the inverter device provided in the embodiments of this application. For example... Figure 3As shown, the inverter includes an inverter circuit 201, a controller 200, and a filter circuit 202. The controller 200 includes a state judgment unit 2000 and a drive control unit 2001. The state judgment unit 2000 is connected to the inverter circuit 201 through the drive control unit 2001. The state judgment unit 2000 can output a first state signal when the output current of the inverter is less than the overload current. The state judgment unit 2000 can output a second state signal when the output current of the inverter is greater than or equal to the overload current. The drive control unit 2001 can control the switching frequency of multiple power switches in the inverter circuit 201 to a first switching frequency based on the first state signal, or control the switching frequency of multiple power switches in the inverter circuit 201 to a second switching frequency based on the second state signal. It is understandable that when the output current value of the inverter is less than the overload current value, it can be said that the current load state meets the working conditions of the inverter (for example, the load is within the rated load range). Here, the controller 200 can output a first status signal to indicate that the current inverter circuit 201 is in the rated working state or rated working mode, and control the switching frequency of multiple power switching transistors in the inverter circuit 201 to the first switching frequency. When the switching frequency is the first switching frequency, the first resonant branch among the multiple resonant branches of the filter circuit 202 has the smallest equivalent impedance. Resonance can be generated through the first resonant branch. Then, when the inverter circuit 201 is in the rated operating state or rated operating mode, the resonant frequency of the filter circuit 202 can be adjusted to the first resonant frequency through the first resonant branch. Alternatively, the filter circuit 202 can also turn on the first resonant branch and disconnect other resonant branches (such as the second resonant branch) based on the indication control switch (or other control method) of the first state signal. Resonance can be generated through the first resonant branch. Then, when the inverter circuit 201 is in the rated operating state or rated operating mode, the resonant frequency of the filter circuit 202 can be adjusted to the first resonant frequency through the first resonant branch, so that the resonant frequency of the filter circuit 202 meets the grid connection requirements. It can also be understood that when the output current value of the inverter is greater than or equal to the overload current value, it indicates that the current load state does not meet the operating conditions of the inverter (for example, the load increases and is in an overload state). The controller 200 can output a second state signal to indicate that the current inverter circuit 201 is in an overload operating state or overload operating mode, and control the switching frequency of multiple power switching transistors in the inverter circuit 201 to the second switching frequency.When the switching frequency is the second switching frequency, the second resonant branch among the multiple resonant branches of the filter circuit 202 has the smallest equivalent impedance. Resonance can be generated through the second resonant branch. Therefore, when the inverter circuit 201 is in an overload operating state or overload operating mode, the resonant frequency of the filter circuit 202 can be adjusted to the second resonant frequency through the second resonant branch. Alternatively, the filter circuit 202 can also turn on the second resonant branch and disconnect other resonant branches (such as the first resonant branch) based on the indication control switch (or other control methods) of the second state signal. Resonance can be generated through the second resonant branch. Therefore, when the inverter circuit 201 is in an overload operating state or overload operating mode, the resonant frequency of the filter circuit 202 can be adjusted to the second resonant frequency through the second resonant branch, so that the resonant frequency of the filter circuit 202 meets the grid connection requirements again. Here, the controller 200 can output different status signals based on the output circuit value of the inverter to indicate the current working state of the inverter circuit 201, so as to control the inverter circuit 201 to use different switching frequencies, and then adjust the resonant frequency of the filter circuit 202 through different resonant branches. While ensuring system stability, it increases the power supply efficiency of the system, reduces losses, responds quickly, and the control method is simple.

[0065] In some feasible implementations, the state judgment unit 2000 can also be used to output a first reset signal when the switching frequency of multiple power switches in the inverter circuit 201 is a second switching frequency and the output current value of the inverter is less than the reset current value. The drive control unit 2001 can also control the switching frequency of multiple power switches in the inverter circuit 201 to the first switching frequency based on the first reset signal. It can be understood that when the output current value of the inverter is less than the reset current value, it indicates that the current load state once again meets the operating conditions of the inverter (e.g., the load has decreased to within the rated load range). The controller 200 can then output the first reset signal to indicate that the current inverter circuit 201 has returned to the rated operating state or rated operating mode from an overload operating state or overload operating mode, and control the switching frequency of multiple power switches in the inverter circuit 201 to increase to the first switching frequency. When the switching frequency is raised back to the first switching frequency, the first resonant branch among the multiple resonant branches of the filter circuit 202 has the smallest equivalent impedance. Resonance can be generated again through the first resonant branch. Therefore, when the inverter circuit 201 returns to its rated operating state or mode, the resonant frequency of the filter circuit 202 is readjusted to the first resonant frequency through the first resonant branch. Alternatively, the filter circuit 202 can re-energize the first resonant branch and disconnect other resonant branches (e.g., the second resonant branch) based on the indication control switch (or other control method) of the first reset signal. Resonance is generated through the first resonant branch, and when the inverter circuit 201 returns to its rated operating state or mode, the resonant frequency of the filter circuit 202 is adjusted to the first resonant frequency through the first resonant branch. This ensures that the resonant frequency of the filter circuit 202 meets the grid connection requirements again and improves power supply efficiency. Here, the raised first switching frequency can be equal to the first switching frequency before the frequency reduction, or it can be a third switching frequency within the range of the first switching frequency; it is not necessarily exactly the same as the first switching frequency before the frequency reduction. Here, the first switching frequency that the inverter circuit 201 reverts to can be a frequency greater than the current switching frequency of the inverter circuit 201 (e.g., the second switching frequency). It can be a frequency obtained by the controller 200 through methods such as acquisition, sampling, receiving, detection, or storage; it can be the switching frequency of multiple power switches in the inverter circuit 201 under rated operating conditions; or it can be a frequency calculated by the controller 200 based on the current output current value of the inverter device. The specific frequency can be set according to the application scenario. It can be understood that the first switching frequency that the inverter circuit 201 reverts to can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values.Here, when the load of the power supply system meets the current operating state of the inverter, the controller 200 can raise the switching frequency of multiple power switching transistors in the inverter circuit 201 back to the first switching frequency. This ensures system stability, increases system power supply efficiency, reduces losses, provides rapid response, and simplifies the control method.

[0066] In some feasible implementations, the variable filter unit may include a variable capacitor unit and a variable inductor unit. See also... Figure 4 , Figure 4 This is another structural schematic diagram of the inverter device provided in the embodiments of this application. For example... Figure 4 As shown, the inverter device includes an inverter circuit 301, a controller 300, and a filter circuit 302. The controller 300 includes a state judgment unit 3000 and a drive control unit 3001. The filter circuit 302 includes a first inductor unit L1, a second inductor unit L2, and multiple resonant units. The multiple resonant units include a capacitor unit Cx and a variable filter unit a. The variable filter unit a includes a variable capacitor unit Ca and a variable inductor unit La. Here, the first inductor unit L1, the second inductor unit L2, the capacitor unit Cx, the variable capacitor unit Ca, and the variable inductor unit La can be a capacitor or inductor unit composed of a single inductor or capacitor, or it can be a capacitor or inductor unit composed of multiple capacitors or multiple inductors integrated together. Here, the variable capacitor unit Ca and the variable inductor unit La are connected in series, and the capacitor unit Cx, the variable capacitor unit Ca, and the variable inductor unit La satisfy the following formula:

[0067] Z11<Z21 (1)

[0068] Z12>Z22 (2)

[0069] Here, Z11 is the equivalent impedance of the capacitor unit at the first switching frequency, Z21 is the equivalent impedance of the variable filter unit at the first switching frequency, Z12 is the equivalent impedance of the capacitor unit at the second switching frequency, and Z22 is the equivalent impedance of the variable filter unit at the second switching frequency.

[0070] In some feasible implementations, the variable filter unit a, composed of the variable capacitor unit Ca and the variable inductor unit La connected in series, resonates at the second switching frequency. When the switching frequency of the multiple power switches in the inverter circuit 301 is the second switching frequency, the equivalent impedance of the variable filter unit a is the lowest. The capacitor unit Cx, the variable capacitor unit Ca, and the variable inductor unit La satisfy the following formula:

[0071] 1 / j2πf1C0<j2πf1L+1 / j2πf1C (3)

[0072] 1 / j2πf2C0>j2πf2L+1 / j2πf2C (4)

[0073] Where f1 is the first switching frequency, f2 is the second switching frequency, C0 is the equivalent capacitance of the capacitor unit, L is the equivalent inductance of the variable inductor unit, C is the equivalent capacitance of the variable capacitor unit, 1 / j2πf1C0 is the equivalent impedance of the capacitor unit at the first switching frequency, j2πf1L+1 / j2πf1C is the equivalent impedance of the variable filter unit at the first switching frequency, 1 / j2πf2C0 is the equivalent impedance of the capacitor unit at the second switching frequency, and j2πf2L+1 / j2πf2C is the equivalent impedance of the variable filter unit at the second switching frequency.

[0074] It is understandable that when the switching frequency is the first switching frequency, the equivalent impedance Z11 of the capacitor unit is less than the equivalent impedance Z21 of the variable filter unit. The output current of the inverter circuit 301 mainly flows through the first resonant branch formed by the capacitor unit, the first inductor unit L1, and the second inductor unit L2. The filter circuit performs filtering through the first resonant branch (e.g., an LCL filter circuit) and resonates at the first resonant frequency. When the switching frequency is the second switching frequency, the equivalent impedance Z12 of the capacitor unit is greater than the equivalent impedance Z22 of the variable filter unit. The output current of the inverter circuit 301 mainly flows through the second resonant branch formed by the variable filter unit, the first inductor unit L1, and the second inductor unit L2. The filter circuit performs filtering through the second resonant branch (e.g., an LLLC filter circuit) and resonates at the second resonant frequency.

[0075] By using this application, the filter circuit 302 can be based on the switching frequency of multiple power switching transistors in the inverter circuit 301, and different resonant branches can be used as filter circuits 302 to generate resonance at different resonant frequencies, ensuring that the resonant frequency of the filter circuit 302 meets the requirements of system stability, with rapid response, simple control method, improved system stability and safety, and strong applicability.

[0076] In some feasible implementations, the multiple resonant modules in the filter circuit may include capacitor units and multiple variable filter units, each of which may include a variable capacitor unit and a variable inductor unit. See also... Figure 5 , Figure 5 This is another structural schematic diagram of the inverter device provided in the embodiments of this application. For example... Figure 5As shown, the inverter device includes an inverter circuit 401, a controller 400, and a filter circuit 402. The controller 400 includes a state judgment unit 4000 and a drive control unit 4001. The filter circuit 402 includes a first inductor unit L1, a second inductor unit L2, a capacitor unit Cx, and multiple variable filter units. For example, variable filter unit a includes a variable capacitor unit Ca and a variable inductor unit La, and variable filter unit n includes a variable capacitor unit Cn and a variable inductor unit Ln. Here, the first inductor unit L1, the second inductor unit L2, the capacitor unit Cx, the variable capacitor unit Ca, the variable inductor unit La, the variable capacitor unit Cn, and the variable inductor unit Ln can be a capacitor or inductor unit composed of a single inductor or capacitor, or it can be a capacitor or inductor unit composed of multiple capacitors or multiple inductors integrated together.

[0077] In some feasible implementations, when the load further increases, the controller 400 can further reduce the switching frequency of the multiple power switches in the inverter circuit 401. When the switching frequency of the multiple power switches in the inverter circuit 401 is the fourth switching frequency (here, the fourth switching frequency is less than the second switching frequency), the multiple resonant units in the filter circuit 402 can (through controlling a switch, or through controlling a selector, or through other means such as different unit impedances or capacitive reactances) utilize a variable filter unit (e.g., a variable filter unit n) to form other resonant branches (e.g., a third resonant branch) with the first inductor unit L1 and the second inductor unit L2, generating resonance at the fourth resonant frequency (here, the fourth resonant frequency is less than the second resonant frequency). It can be understood that the fourth resonant frequency here can be a frequency obtained by the controller 400 through means such as acquisition, collection, reception, detection, or storage, it can be a certain overload resonant frequency of the filter circuit 402, or it can be a frequency calculated by the controller 400 based on the current output current value of the inverter device, and can be specifically set according to the application scenario. It is understandable that the fourth resonant frequency here can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values.

[0078] In some feasible implementations, the resonant frequencies of the variable capacitor unit Cn and the variable inductor unit Ln in the variable filter unit n can be the fourth switching frequency. That is, the equivalent impedance of the variable capacitor unit Cn and the variable inductor unit Ln is minimized when the switching frequency is the fourth switching frequency. In other words, when the switching frequency is the fourth switching frequency, the equivalent impedance of the capacitor unit and the equivalent impedance of the variable filter unit a are greater than the equivalent impedance of the variable filter unit n. The output current of the inverter circuit 401 mainly flows through the variable filter unit n. The variable filter unit n, together with the first inductor unit and the second inductor unit, forms another resonant branch (e.g., a third resonant branch), which resonates at the fourth resonant frequency.

[0079] Please see Figure 6 , Figure 6 This is a schematic diagram of the power supply system provided in an embodiment of this application. For example... Figure 6 As shown, the power supply system may include a transformer 503, through which the power source can be connected to an inverter. The transformer 503 converts the voltage output from the power source into a voltage matching that of the inverter, and outputs the transformed electrical energy to the inverter. The inverter then converts the DC power output into AC power and transmits it to the load, enabling the system to supply power to the grid or AC-powered equipment on the grid side, thus improving the system's adaptability. Figure 6 The connection method and working principle of the power supply, inverter (including controller 500 (including status judgment unit 5000 and drive control unit 5001), inverter circuit 501, and filter circuit 502) and load are the same as those described above. Figure 5 The connection method and working principle of the power supply, inverter (including controller 400 (including status judgment unit 4000 and drive control unit 4001), inverter circuit 401, and filter circuit 402) and load are the same, and will not be repeated here.

[0080] By employing this application, when the switching frequency of multiple power switching transistors in the inverter circuit decreases due to power supply system overload, resonance can be achieved through the resonant branch with the lowest equivalent impedance among multiple resonant branches. This allows for timely adjustment of the resonant frequency of the filter circuit, ensuring that the resonant frequency of the filter circuit meets the system stability requirements. The application is characterized by rapid response, simple control method, improved system stability and safety, and strong applicability.

[0081] In some feasible implementations, the power supply system may also include a DC bus, and the transformer 503 can be connected to the power grid via the DC bus and the inverter. Here, the DC bus may include a bus capacitor or multiple bus capacitors connected in series, which can be used for energy storage. The DC bus may include a bus capacitor, and the inverter can convert the electrical energy output from the power supply and stored at both ends of the bus capacitor, and output the corresponding current and voltage to maintain the operation of the power grid.

[0082] Please see also Figure 7 , Figure 7 This is another structural schematic diagram of the power supply system provided in an embodiment of this application. Figure 7 The power supply system shown may also include a combiner box 604, through which the transformer in the power supply system can be connected to the inverter. It can be understood that the transformer in the power supply system can be connected to the combiner box 604 and then directly connected to the inverter via the combiner box 604, or it can be connected to the DC bus via the combiner box 604 and then connected to the inverter via the DC bus. The specific configuration can be determined according to the actual application scenario and is not limited here. Figure 7The connection method and working principle of the power supply, inverter (including controller 600 (including status judgment unit 6000 and drive control unit 6001), inverter circuit 601, filter circuit 602), transformer 603 and load are the same as those described above. Figure 6 The connection method and working principle of the power supply, inverter (including controller 500 (including status judgment unit 5000 and drive control unit 5001), inverter circuit 501, filter circuit 502), transformer 503 and load are the same, and will not be described again here.

[0083] See Figure 8 , Figure 8 This is another structural schematic diagram of the power supply system provided in an embodiment of this application. For example... Figure 8 As shown, the load of the power supply system may also include a grid connection device 705. The inverter can supply power to power-consuming equipment or power transmission equipment such as transmission lines, power transfer stations, batteries, communication base stations, or household appliances in the power grid through the grid connection device 705. Figure 8 The connection methods and working principles of the power supply, inverter (including controller 700 (including status judgment unit 7000 and drive control unit 7001), inverter circuit 701, filter circuit 702), transformer 703, combiner box 704, and load are the same as those described above. Figure 7 The connection method and working principle of the power supply, inverter (including controller 600 (including status judgment unit 6000 and drive control unit 6001), inverter circuit 601, filter circuit 602), transformer 603, combiner box 604 and load are the same, and will not be described again here.

[0084] In this application, the functional modules of the power supply system are arranged in a variety of flexible ways to adapt to different power supply environments, thereby increasing the diversity of application scenarios and enhancing the adaptability of the power supply system. Meanwhile, in the aforementioned... Figures 1 to 8 In any of the power supply systems shown, or in other inverters connected to the power grid, or in the controller of other inverters connected to the power grid, the power supply system (or inverter, or inverter controller) can generate resonance through different resonant branches when the switching frequency of multiple power switches in the inverter circuit decreases due to power supply system overload. This allows for timely adjustment of the resonant frequency of the filter circuit to ensure that the resonant frequency of the filter circuit meets the system stability requirements. For ease of description, the following will use... Figure 2 The structure of the power supply system shown is used as an example to illustrate the grid connection control method provided in the embodiments of this application.

[0085] Please see Figure 9 , Figure 9This is a flowchart illustrating the grid-connected control method provided in this application. The grid-connected control method provided in this application is applicable to inverter devices and also to the aforementioned... Figures 1 to 8 Any grid-connected inverter or power supply system shown. For example... Figure 9 As shown, the grid connection control method provided in this application includes the following steps:

[0086] S801: Detects the output current value of the inverter.

[0087] S802: Based on the output current value of the inverter, the switching frequency of multiple power switching transistors is adjusted to adjust the resonant frequency of the filter circuit through different resonant branches, so that the resonant frequency meets the grid connection requirements.

[0088] In this application, the controller can obtain the output current value of the inverter (through methods such as acquisition, collection, reception, detection, or storage). The output current value of the inverter can be the output current value of the inverter circuit, the output current value at the connection point between the inverter and the load (e.g., the grid connection point when the load is the power grid), or the output current value of a sampling point, which can be set according to the application scenario. Here, the controller can adjust the switching frequency of multiple power switches based on the output current value of the inverter. It can be understood that in different application scenarios (e.g., the inverter is equivalent to a voltage source in a grid-connected scenario), the controller can control the switching frequency of multiple power switches at different switching frequencies based on the output current value of the inverter to adjust the output power of the inverter to adapt to changes in the load, thereby ensuring normal power supply to the load. For example, in a scenario where the power supply system is overloaded (i.e., the load increases), the controller can reduce the switching frequency of multiple power switches. During the operation of an inverter, due to the high switching frequency of components (such as switching transistors) in the inverter circuit, the output current (or voltage) contains harmonics. A filter circuit is needed between the inverter circuit and the load to remove these harmonics. When the power supply system is connected to the grid, to maintain system stability, the resonant frequency of the filter circuit is typically required to be less than a certain value (e.g., 1 / 4 of the switching frequency). Here, the filter circuit consists of multiple resonant branches composed of an inductor unit and multiple parallel resonant units. The device can also adjust the resonant frequency of the filter circuit through different resonant branches. For example, in a power supply system overload scenario (i.e., increased load), the controller can reduce the switching frequency of multiple power switching transistors. Based on the reduced switching frequency of the power switching transistors, the multiple resonant units adjust the resonant frequency of the filter circuit to maintain the stability of the power supply system.

[0089] In some feasible implementations, step S802, which adjusts the switching frequencies of multiple power switches based on the output current value of the inverter to adjust the resonant frequency of the filter circuit through different resonant branches, may include: when the switching frequencies of the multiple power switches are different, resonating through the resonant branch with the lowest equivalent impedance among the multiple resonant branches to adjust the resonant frequency of the filter circuit. Here, when the controller adjusts the switching frequencies of the multiple power switches, it simultaneously changes the magnitude of the equivalent impedance in the multiple resonant branches. Here, different resonant branches (e.g., a first resonant branch composed of a capacitor unit and an inductor unit, and a second resonant branch composed of a variable filter unit and an inductor unit) have different equivalent impedances at different switching frequencies. When the controller adjusts the switching frequencies of the multiple power switches, the current will mainly flow through the resonant branch with the lowest equivalent impedance at the current switching frequency, so that the resonant branch with the lowest equivalent impedance resonates with other components in the filter circuit at the resonant frequency corresponding to the current switching frequency. Therefore, based on the different switching frequencies of the inverter circuit 11, the filter circuit 12 can adjust the resonant frequency through different resonant branches.

[0090] By employing this application, when the switching frequency of multiple power switches in the inverter circuit decreases due to power system overload, resonance can be achieved through the resonant branch with the lowest equivalent impedance among multiple resonant branches. This allows for timely adjustment of the resonant frequency of the filter circuit, enhancing the load-carrying capacity of the device while ensuring that the resonant frequency of the filter circuit meets the system stability requirements. The application is characterized by rapid response, simple control method, improved system stability and safety, and strong applicability.

[0091] In some feasible implementations, the multiple resonant units include a capacitor unit and at least one variable filter unit. The inductor unit includes a first inductor unit and a second inductor unit, which are connected in series between the inverter circuit and the load. The capacitor unit and the variable filter unit are connected in parallel between the first inductor unit and the second inductor unit. The capacitor unit and the inductor unit form a first resonant branch, and the variable filter unit and the inductor unit form a second resonant branch. Please refer to [further details omitted]. Figure 10 , Figure 10 This is another flowchart illustrating the grid connection control method provided in this application. For example... Figure 10 As shown, the above control method may include the following steps:

[0092] S901: Detects the output current value of the inverter.

[0093] S902: Determine whether the output current value of the inverter is greater than or equal to the overload current value. If the determination result of step S902 is no, then proceed to step S903; if the determination result of step S902 is yes, then proceed to step S904.

[0094] S903: Adjust the switching frequency of multiple power switching transistors to the first switching frequency, and adjust the resonant frequency of the filter circuit through the first resonant branch to the first resonant frequency.

[0095] In some feasible implementations, after the controller obtains the output current value of the inverter (through methods such as acquisition, sampling, receiving, detection, or storage), the controller can control the switching frequency of multiple power switches based on the output current value of the inverter. When the output current value of the inverter is less than the overload current value, it indicates that the current load condition meets the operating conditions of the inverter (e.g., the load is within the rated load range), and the controller can adjust the switching frequency of the multiple power switches to a first switching frequency. Here, the first switching frequency can be the current switching frequency of the inverter circuit, the frequency obtained by the controller through methods such as acquisition, sampling, receiving, detection, or storage, the switching frequency of the multiple power switches in the inverter circuit under rated operating conditions, or the frequency calculated by the controller based on the current output current value of the inverter. The specific frequency can be set according to the application scenario. It can be understood that the first switching frequency here can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values. Here, among multiple resonant branches, the first resonant branch, composed of capacitor and inductor units (e.g., the first and second inductor units), has the smallest equivalent impedance when the switching frequency of the multiple power switches is the first switching frequency. Current mainly flows through this first resonant branch, causing it to resonate at the resonant frequency corresponding to the first switching frequency (i.e., the first resonant frequency). In other words, when the inverter's output current is less than the overload current, the resonant frequency of the filter circuit can be adjusted to the first resonant frequency based on the switching frequency of the multiple power switches (i.e., the first switching frequency). Here, the first resonant frequency is less than the first stable frequency, which is the grid-connected stable frequency corresponding to the first switching frequency (e.g., 1 / 4 of the first switching frequency). During grid connection of the power supply system, to meet system stability requirements, the first resonant frequency needs to be less than a certain grid-connected stable frequency (e.g., 1 / 4 of the first switching frequency). It is understandable that the value of the first resonant frequency here can be determined based on the current resonant frequency of the filter circuit. This could be a frequency obtained by the controller through methods such as acquisition, sampling, receiving, detection, or storage; it could be the rated resonant frequency of the filter circuit; or it could be a frequency calculated by the controller based on the current output current value of the inverter. The specific setting depends on the application scenario. It is also understandable that the first resonant frequency here can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values.

[0096] By using this application, when the load of the power supply system meets the current operating state of the inverter, the switching frequency of multiple power switching transistors can be adjusted to the first switching frequency, so as to adjust the resonant frequency of the filter circuit to the first resonant frequency through the first resonant branch, so as to ensure that the resonant frequency of the filter circuit meets the requirements of system stability. The control method is simple, flexible and highly applicable.

[0097] S904: Reduce the switching frequency of multiple power switching transistors to a second switching frequency to enhance the load-carrying capacity of the inverter, and adjust the resonant frequency of the filter circuit to a second resonant frequency through the second resonant branch.

[0098] In some feasible implementations, after the controller obtains the output current value of the inverter (through methods such as acquisition, sampling, receiving, detection, or storage), the controller can control the switching frequency of multiple power switches based on the output current value of the inverter. When the output current value of the inverter is greater than or equal to the overload current value, it indicates that the current load condition does not meet the operating conditions of the inverter (e.g., the load has increased and is in an overload state). The controller can then reduce the switching frequency of the multiple power switches to a second switching frequency to enhance the load-carrying capacity of the inverter, and adjust the resonant frequency of the filter circuit to a second resonant frequency through the second resonant branch. Here, the second switching frequency is less than the first switching frequency, and when the switching frequency is the second switching frequency, the equivalent impedance of the second resonant branch is less than the equivalent impedance of the first resonant branch. Here, the second switching frequency can be a frequency lower than the current switching frequency of the inverter circuit (e.g., the second switching frequency). It can be a frequency obtained by the controller through methods such as acquisition, sampling, receiving, detection, or storage; it can be the switching frequency of multiple power switches in the inverter circuit under overload conditions; or it can be a frequency calculated by the controller based on the current output current value of the inverter. The specific frequency can be set according to the application scenario. It can be understood that the second switching frequency here can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values. Here, among the multiple resonant branches, the second resonant branch composed of the variable filter unit and the inductor unit (e.g., the first inductor unit and the second inductor unit) has the lowest equivalent impedance when the switching frequency of the multiple power switches is the second switching frequency. Current mainly flows through the second resonant branch composed of the variable filter unit and the inductor unit (e.g., the first inductor unit and the second inductor unit), causing the second resonant branch to resonate at the resonant frequency corresponding to the second switching frequency (i.e., the second resonant frequency). In other words, when the output current of the inverter is greater than or equal to the overload current, the resonant frequency of the filter circuit can be reduced to a second resonant frequency by using the second resonant branch based on the switching frequencies of multiple power switches (i.e., the second switching frequency). Here, the second resonant frequency is less than the second stable frequency and less than the first resonant frequency. The second stable frequency is the grid-connected stable frequency corresponding to the second switching frequency (for example, the second stable frequency is 1 / 4 of the second switching frequency). During the grid connection process of the power supply system, in order to meet the system stability requirements, the second resonant frequency needs to be less than a certain grid-connected stable frequency (for example, 1 / 4 of the second switching frequency). It can be understood that the value of the second resonant frequency here can be determined based on the current resonant frequency of the filter circuit. It can be a frequency obtained by the controller through methods such as acquisition, collection, reception, detection, or storage; it can be the overload resonant frequency of the filter circuit; or it can be a frequency calculated by the controller based on the current output current value of the inverter. The specific value can be set according to the application scenario.It is understandable that the second resonant frequency here can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values.

[0099] By adopting this application, when the load of the power supply system increases and the current inverter is in an overloaded operating state, the switching frequency of multiple power switching transistors can be reduced to a second switching frequency, so as to adjust the resonant frequency of the filter circuit through the second resonant branch to a second resonant frequency, thereby ensuring that the resonant frequency of the filter circuit meets the requirements of system stability. The control method is simple, flexible and highly applicable.

[0100] In some feasible implementations, after adjusting the resonant frequency of the filter circuit to the second resonant frequency via the capacitor unit in step S904, the method further includes: when the output current value of the inverter is less than the reset current value, increasing the switching frequency of the plurality of power switches to a first switching frequency, so as to adjust the resonant frequency of the filter circuit to the first resonant frequency via the first resonant branch. Here, the reset current value is less than or equal to the overload current value.

[0101] It is understandable that after the controller controls the switching frequency of multiple power switches to the second switching frequency, the controller can also obtain the output current value of the inverter (through methods such as acquisition, sampling, receiving, detection, or storage). The controller can also control the switching frequency of the multiple power switches based on the output current value of the inverter. When the switching frequency of the multiple power switches is the second switching frequency and the output current value of the inverter is less than the reset current value, it indicates that the current load state once again meets the operating conditions of the inverter (e.g., the load is reduced to the rated load range). The controller can then increase the switching frequency of the multiple power switches to the first switching frequency. Here, the increased first switching frequency can be equal to the first switching frequency before the frequency reduction, or it can be a third switching frequency within the first switching frequency range; it is not necessarily exactly equal to the first switching frequency before the frequency reduction. Here, the first switching frequency that the inverter circuit re-raises to can be a frequency greater than the current switching frequency of the inverter circuit (e.g., the second switching frequency). It can be a frequency obtained by the controller through methods such as acquisition, sampling, receiving, detection, or storage; it can be the switching frequency of multiple power switches in the inverter circuit under rated operating conditions; or it can be a frequency calculated by the controller based on the current output current value of the inverter device. The specific frequency can be set according to the application scenario. It can be understood that the first switching frequency that the inverter circuit re-raises to can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values. Correspondingly, when the output current value of the inverter device is less than the reset current value, the resonant frequency of the filter circuit can be re-raised to the first resonant frequency through the first resonant branch based on the switching frequencies of the multiple power switches (i.e., the first switching frequency). Here, the first resonant frequency that the filter circuit re-raises to can be equal to the first resonant frequency before frequency reduction, or it can be a third resonant frequency within the range of the first resonant frequency; it is not necessarily exactly equal to the first resonant frequency before frequency reduction. It is understandable that the first resonant frequency that the filter circuit re-emerges to can be a frequency obtained by the controller through methods such as acquisition, sampling, receiving, detection, or storage. It can be the overload resonant frequency of the filter circuit, or a frequency calculated by the controller based on the current output current value of the inverter. The specific frequency can be set according to the application scenario. It is also understood that the first resonant frequency that the filter circuit re-emerges to can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values.

[0102] By adopting this application, when the load of the power supply system meets the current operating state of the inverter, the switching frequency of multiple power switching transistors can be increased to the first switching frequency, so as to adjust the resonant frequency of the filter circuit through the first resonant branch to the first resonant frequency, thereby ensuring that the resonant frequency of the filter circuit meets the requirements of system stability. The control method is simple, flexible, and highly applicable, and improves the power supply efficiency of the system.

[0103] In some feasible implementations, after detecting the output current value of the inverter in step S801 or S901, the method further includes: outputting a first state signal when the output current value of the inverter is less than the overload current value; and outputting a second state signal when the output current value of the inverter is greater than or equal to the overload current value. The switching frequency of multiple power switches is controlled to a first switching frequency based on the first state signal, or the switching frequency of multiple power switches is controlled to a second switching frequency based on the second state signal. It can be understood that when the output current value of the inverter is less than the overload current value, it indicates that the current load condition meets the operating conditions of the inverter (e.g., the load is within the rated load range). Here, the controller can output a first state signal to indicate that the current inverter circuit is in a rated operating state or rated operating mode, and control the switching frequency of multiple power switches to the first switching frequency. When the switching frequency is the first switching frequency, the first resonant branch among the multiple resonant branches of the filter circuit has the smallest equivalent impedance. The filter circuit can generate resonance through the first resonant branch based on the fact that the equivalent impedance of the first resonant branch is the smallest at the first switching frequency. Then, when the inverter circuit is in the rated operating state or rated operating mode, the resonant frequency of the filter circuit can be adjusted to the first resonant frequency through the first resonant branch. Alternatively, the filter circuit can control the switch (or other control method) based on the indication of the first state signal to turn on the first resonant branch and disconnect other resonant branches (such as the second resonant branch). Resonance can be generated through the first resonant branch. Then, when the inverter circuit is in the rated operating state or rated operating mode, the resonant frequency of the filter circuit can be adjusted to the first resonant frequency through the first resonant branch, so that the resonant frequency of the filter circuit meets the grid connection requirements. It can also be understood that when the output current of the inverter is greater than or equal to the overload current, it indicates that the current load condition does not meet the operating conditions of the inverter (e.g., the load increases and it is in an overload state). The controller can output a second status signal to indicate that the current inverter circuit is in an overload operating state or overload operating mode, and control the switching frequency of multiple power switches to the second switching frequency. When the switching frequency is the second switching frequency, the equivalent impedance of the second resonant branch among the multiple resonant branches of the filter circuit is the smallest. Resonance can be generated through the second resonant branch, and then when the inverter circuit is in an overload operating state or overload operating mode, the resonant frequency of the filter circuit can be adjusted to the second resonant frequency through the second resonant branch. Alternatively, the filter circuit can also control the switch (or other control methods) based on the indication of the second status signal to turn on the second resonant branch and disconnect other resonant branches (e.g., the first resonant branch), generating resonance through the second resonant branch. Then, when the inverter circuit is in an overload operating state or overload operating mode, the resonant frequency of the filter circuit can be adjusted to the second resonant frequency through the second resonant branch, so that the resonant frequency of the filter circuit meets the grid connection requirements again.Here, the controller can output different status signals based on the output circuit value of the inverter to indicate the current working state of the inverter circuit, so as to control the inverter circuit to use different switching frequencies, and then adjust the resonant frequency of the filter circuit through different resonant branches. While ensuring system stability, it increases the power supply efficiency of the system, reduces losses, responds quickly, and the control method is simple.

[0104] In some feasible implementations, after controlling the switching frequency of multiple power switches to a second switching frequency based on a second state signal, the method further includes: outputting a first reset signal when the output current value of the inverter is less than a reset current value. The switching frequency of the multiple power switches is then controlled to the first switching frequency based on the first reset signal. It is understood that when the output current value of the inverter is less than the reset current value, it indicates that the current load state once again meets the operating conditions of the inverter (e.g., the load has decreased to within the rated load range). Here, the controller can output the first reset signal to indicate that the current inverter circuit has returned from an overload operating state or overload operating mode to a rated operating state or rated operating mode, controlling the switching frequency of the multiple power switches to increase to the first switching frequency. When the switching frequency is raised back to the first switching frequency, the first resonant branch among the multiple resonant branches of the filter circuit has the smallest equivalent impedance. Resonance can be generated again through the first resonant branch. Then, when the inverter circuit returns to its rated operating state or mode, the resonant frequency of the filter circuit is readjusted to the first resonant frequency through the first resonant branch. Alternatively, the filter circuit can re-energize the first resonant branch and disconnect other resonant branches (e.g., the second resonant branch) based on the indication control switch (or other control methods) of the first reset signal. Resonance is generated through the first resonant branch, and when the inverter circuit returns to its rated operating state or mode, the resonant frequency of the filter circuit is adjusted to the first resonant frequency through the first resonant branch, ensuring that the resonant frequency of the filter circuit meets grid connection requirements again and improving power supply efficiency. Here, the raised first switching frequency can be equal to the first switching frequency before frequency reduction, or it can be a third switching frequency within the range of the first switching frequency; it is not necessarily exactly equal to the first switching frequency before frequency reduction. Here, the first switching frequency that the inverter circuit re-upgrades to can be a frequency greater than the current switching frequency of the inverter circuit (e.g., the second switching frequency). It can be a frequency obtained by the controller through methods such as acquisition, sampling, receiving, detection, or storage; it can be the switching frequency of multiple power switches in the inverter circuit under rated operating conditions; or it can be a frequency calculated by the controller based on the current output current value of the inverter device. The specific frequency can be set according to the application scenario. It can be understood that the first switching frequency that the inverter circuit re-upgrades to can be a single frequency value, multiple frequency values, a frequency range composed of multiple frequency values, or multiple frequency ranges composed of multiple frequency values. Here, the controller can re-upgrade the switching frequency of multiple power switches to the first switching frequency when the load of the power supply system once again meets the current operating state of the inverter device. This ensures system stability, increases system power supply efficiency, reduces losses, provides rapid response, and simplifies the control method.

[0105] In this application, when the switching frequency of multiple power switching transistors decreases due to power supply system overload, resonance is generated through different resonant branches, and the resonant frequency of the filter circuit is adjusted in a timely manner to ensure that the resonant frequency of the filter circuit meets the requirements of system stability. The response is rapid, the control method is simple, the system stability and safety are improved, and the applicability is strong.

[0106] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A grid-connected inverter device, characterized in that, The inverter device includes an inverter circuit, a controller, and a filter circuit; The inverter circuit includes multiple power switching transistors connected in series or in parallel, the filter circuit includes multiple resonant branches composed of an inductor unit and multiple parallel resonant units, one end of the inverter circuit is used to connect to a DC power supply, and the other end of the inverter circuit is connected to the power grid or a load through the filter circuit. The controller is used to adjust the switching frequency of the plurality of power switching transistors based on the output current value of the inverter device, and simultaneously change the magnitude of the equivalent impedance in the plurality of resonant branches when adjusting the switching frequency of the plurality of power switching transistors, so as to achieve resonance through the resonant branch with the lowest equivalent impedance among the plurality of resonant branches, so as to adjust the resonant frequency of the filter circuit and make the resonant frequency meet the grid connection requirements.

2. The inverter device according to claim 1, characterized in that, The plurality of resonant units include a capacitor unit and at least one variable filter unit. The inductor unit includes a first inductor unit and a second inductor unit. The first inductor unit and the second inductor unit are connected in series between the inverter circuit and the load. The capacitor unit and the variable filter unit are connected in parallel between the first inductor unit and the second inductor unit. The capacitor unit and the inductor unit form a first resonant branch, and the variable filter unit and the inductor unit form a second resonant branch. The controller is further configured to adjust the switching frequency of the plurality of power switching transistors to a first switching frequency when the output current value of the inverter is less than the overload current value, so as to adjust the resonant frequency of the filter circuit to a first resonant frequency through the first resonant branch. When the switching frequency is the first switching frequency, the equivalent impedance of the first resonant branch is less than the equivalent impedance of the second resonant branch, the first resonant frequency is less than the first stable frequency, and the first stable frequency is the grid-connected stable frequency corresponding to the first switching frequency.

3. The inverter device according to claim 2, characterized in that, The controller is further configured to, when the output current value of the inverter is greater than or equal to the overload current value, reduce the switching frequency of the plurality of power switching transistors to a second switching frequency to enhance the load-carrying capacity of the inverter, and adjust the resonant frequency of the filter circuit to a second resonant frequency through the second resonant branch, wherein the second switching frequency is less than the first switching frequency, and when the switching frequency is the second switching frequency, the equivalent impedance of the second resonant branch is less than the equivalent impedance of the first resonant branch, the second resonant frequency is less than the second stable frequency and less than the first resonant frequency, and the second stable frequency is the grid-connected stable frequency corresponding to the second switching frequency.

4. The inverter device according to claim 3, characterized in that, The controller is further configured to, when the switching frequency of the plurality of power switching transistors is the second switching frequency and the output current value of the inverter is less than the reset current value, increase the switching frequency of the plurality of power switching transistors to the first switching frequency, so as to adjust the resonant frequency of the filter circuit to the first resonant frequency through the first resonant branch, wherein the reset current value is less than or equal to the overload current value.

5. The inverter device according to claim 3 or 4, characterized in that, The controller includes a status judgment unit and a drive control unit, and the status judgment unit is connected to the inverter circuit through the drive control unit. The state determination unit is used to output a first state signal when the output current value of the inverter is less than the overload current value; The state determination unit is used to output a second state signal when the output current value of the inverter is greater than or equal to the overload current value; The drive control unit is used to control the switching frequency of the plurality of power switches to the first switching frequency based on the first status signal, or Based on the second state signal, the switching frequency of the plurality of power switches is controlled to be the second switching frequency.

6. The inverter device according to claim 5, characterized in that, The state determination unit is also used to output a first reset signal when the switching frequency of the plurality of power switching transistors is the second switching frequency and the output current value of the inverter is less than the reset current value; The drive control unit is also configured to control the switching frequency of the plurality of power switching transistors to the first switching frequency based on the first reset signal.

7. The inverter device according to claim 6, characterized in that, One of the variable filter units includes a variable capacitor unit and a variable inductor unit, wherein the variable capacitor unit and the variable inductor unit are connected in series, and the capacitor unit, the variable capacitor unit, and the variable inductor unit satisfy the following: Wherein, Z11 is the equivalent impedance of the capacitor unit when the switching frequency is the first switching frequency, Z21 is the equivalent impedance of the variable filter unit when the switching frequency is the first switching frequency, Z12 is the equivalent impedance of the capacitor unit when the switching frequency is the second switching frequency, and Z22 is the equivalent impedance of the variable filter unit when the switching frequency is the second switching frequency.

8. A grid-connected control method for an inverter, characterized in that, The control method is applicable to grid-connected inverter devices. The inverter device includes an inverter circuit, a controller, and a filter circuit. The inverter circuit includes multiple power switching transistors connected in series or parallel. The filter circuit includes multiple resonant branches composed of an inductor unit and multiple parallel resonant units. One end of the inverter circuit is connected to a DC power supply, and the other end of the inverter circuit is connected to the power grid or a load through the filter circuit. The controller is connected to the inverter circuit. The method includes: Detect the output current value of the inverter; The switching frequency of the multiple power switches is adjusted based on the output current value of the inverter. While adjusting the switching frequency of the multiple power switches, the equivalent impedance in the multiple resonant branches is changed simultaneously so that resonance is achieved through the resonant branch with the lowest equivalent impedance among the multiple resonant branches. This adjusts the resonant frequency of the filter circuit so that the resonant frequency meets the grid connection requirements.

9. The control method according to claim 8, characterized in that, The plurality of resonant units include a capacitor unit and at least one variable filter unit. The inductor unit includes a first inductor unit and a second inductor unit. The first inductor unit and the second inductor unit are connected in series between the inverter circuit and the load. The capacitor unit and the variable filter unit are connected in parallel between the first inductor unit and the second inductor unit. The capacitor unit and the inductor unit form a first resonant branch, and the variable filter unit and the inductor unit form a second resonant branch. After detecting the output current value of the inverter device, the method further includes: When the output current of the inverter is less than the overload current, the switching frequency of the plurality of power switching transistors is adjusted to a first switching frequency, so as to adjust the resonant frequency of the filter circuit to a first resonant frequency through the first resonant branch. When the switching frequency is the first switching frequency, the equivalent impedance of the first resonant branch is less than the equivalent impedance of the second resonant branch, the first resonant frequency is less than the first stable frequency, and the first stable frequency is the grid-connected stable frequency corresponding to the first switching frequency.

10. The control method according to claim 9, characterized in that, After detecting the output current value of the inverter, the method further includes: When the output current of the inverter is greater than or equal to the overload current, the switching frequency of the plurality of power switches is reduced to a second switching frequency to enhance the load-carrying capacity of the inverter. The resonant frequency of the filter circuit is adjusted to a second resonant frequency through the second resonant branch. The second switching frequency is less than the first switching frequency. When the switching frequency is the second switching frequency, the equivalent impedance of the second resonant branch is less than the equivalent impedance of the first resonant branch. The second resonant frequency is less than the second stable frequency and less than the first resonant frequency. The second stable frequency is the grid-connected stable frequency corresponding to the second switching frequency.

11. The control method according to claim 10, characterized in that, After adjusting the resonant frequency of the filter circuit to the second resonant frequency via the variable filter unit, the method further includes: When the output current value of the inverter is less than the reset current value, the switching frequency of the plurality of power switching transistors is increased to the first switching frequency, so as to adjust the resonant frequency of the filter circuit to the first resonant frequency through the first resonant branch, wherein the reset current value is less than or equal to the overload current value.

12. The control method according to claim 10 or 11, characterized in that, The controller includes a status judgment unit and a drive control unit. After detecting the output current value of the inverter, the method further includes: When the output current value of the inverter is less than the overload current value, a first state signal is output; When the output current value of the inverter is greater than or equal to the overload current value, a second state signal is output; Based on the first state signal, the switching frequency of the plurality of power switches is controlled to be the first switching frequency. Alternatively, the switching frequency of the plurality of power switches can be controlled to the second switching frequency based on the second state signal.

13. The control method according to claim 12, characterized in that, After controlling the switching frequency of the plurality of power switches to the second switching frequency based on the second state signal, the method further includes: When the output current value of the inverter is less than the reset current value, a first reset signal is output; Based on the first reset signal, the switching frequency of the plurality of power switching transistors is controlled to be the first switching frequency.

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