Sampling circuit of inverter and inverter

Abstract

This application provides a sampling circuit and an inverter for an inverter. The inverter includes a three-phase output circuit, each phase output circuit including an AC switch connected to the power grid; the side of the AC switch closer to the inverter is connected to an inverter-side inductor and a filter capacitor, and the side closer to the power grid is connected to a grid-side inductor. The sampling circuit includes three resistor sampling units. The first terminal of the first resistor sampling unit is connected to the node between the AC switch and the grid-side inductor in the first phase output circuit, and its second terminal is connected to the node between the AC switch and the grid-side inductor in the second phase output circuit, used to sample the line voltage between the first and second phase output circuits; the second resistor sampling unit is used to sample the line voltage between the second and third phase output circuits; and the third resistor sampling unit is used to sample the line voltage between the third and first phase output circuits. This solution can avoid introducing high-frequency harmonic paths and suppress high-frequency harmonics generated by the sampling circuit.

Description

Technical Field

[0001] This application relates to the field of power conversion technology, specifically to a sampling circuit for an inverter and an inverter. Background Technology

[0002] During inverter operation, the voltage on the AC output side needs to be sampled to determine whether the operating conditions are met. In related technologies, sampling capacitors are set in the three-phase output circuits to construct a virtual neutral point, thereby sampling the voltage between each phase output circuit and the virtual neutral point to obtain the measured value of each phase output voltage.

[0003] However, since the inverter's AC output side uses an LCL filter structure, high-frequency harmonics may be introduced into the output current of the operating inverter when the inverter is in a shutdown state, thus affecting the quality of the output current. Utility Model Content

[0004] This application provides a sampling circuit and an inverter for an inverter, which can suppress high-frequency harmonics generated by the sampling circuit while sampling the AC output voltage of the inverter.

[0005] In a first aspect, this application provides a sampling circuit for an inverter, the inverter including a three-phase output circuit, each phase output circuit including an AC switch connected to the power grid; the side of the AC switch near the inverter is connected to an inverter-side inductor and a filter capacitor, and the side of the AC switch near the power grid is connected to a grid-side inductor; the sampling circuit includes three resistor sampling units, the three resistor sampling units including: a first resistor sampling unit, the first end of which is connected to the node between the AC switch and the grid-side inductor in the first phase output circuit, and the second end of which is connected to the node between the AC switch and the grid-side inductor in the second phase output circuit, for sampling the connection between the first phase output circuit and the second phase output circuit. The system comprises: a line voltage between phase output circuits; a second resistor sampling unit, the first end of which is connected to the node between the AC switch and the grid-side inductor in the second phase output circuit, and the second end of which is connected to the node between the AC switch and the grid-side inductor in the third phase output circuit, for sampling the line voltage between the second phase output circuit and the third phase output circuit; and a third resistor sampling unit, the first end of which is connected to the node between the AC switch and the grid-side inductor in the third phase output circuit, and the second end of which is connected to the node between the AC switch and the grid-side inductor in the first phase output circuit, for sampling the line voltage between the third phase output circuit and the first phase output circuit.

[0006] Optionally, the at least one resistance sampling unit includes: a first resistance sampling unit, with a first end connected to the node between the AC switch and the grid-side inductor in the first phase output circuit, and a second end connected to the node between the AC switch and the grid-side inductor in the second phase output circuit, for sampling the line voltage between the first phase output circuit and the second phase output circuit; a second resistance sampling unit, with a first end connected to the node between the AC switch and the grid-side inductor in the second phase output circuit, and a second end connected to the node between the AC switch and the grid-side inductor in the third phase output circuit, for sampling the line voltage between the second phase output circuit and the third phase output circuit; and a third resistance sampling unit, with a first end connected to the node between the AC switch and the grid-side inductor in the third phase output circuit, and a second end connected to the node between the AC switch and the grid-side inductor in the first phase output circuit, for sampling the line voltage between the third phase output circuit and the first phase output circuit.

[0007] Optionally, the resistance sampling unit includes: at least two sampling resistors connected in series for dividing the line voltage; and a voltage acquisition module, the input of which is connected to the voltage divider node between the sampling resistors for acquiring the voltage signal after voltage division.

[0008] Optionally, the at least two series-connected sampling resistors include a first terminal resistor, an intermediate resistor, and a second terminal resistor connected in series; the input terminal of the voltage acquisition module is connected to both ends of the intermediate resistor to acquire the voltage signal across the intermediate resistor, wherein the resistance value of the intermediate resistor is less than the resistance values ​​of the first terminal resistor and the second terminal resistor.

[0009] Optionally, the resistance values ​​of the first terminal resistor and the second terminal resistor are in the megaohm range, and the resistance value of the intermediate resistor is in the kiloohm range.

[0010] Optionally, the sampling circuit further includes a first control unit, the input terminal of which is connected to the output terminal of the voltage acquisition module, for generating a measured value of the line voltage based on the voltage signal acquired by the voltage acquisition module.

[0011] Optionally, the resistance sampling unit includes: at least one sampling resistor; and a current sensor connected in series with the sampling resistor for detecting the current signal in the sampling resistor.

[0012] Optionally, the total resistance of the sampling resistors is in the megaohm range.

[0013] Optionally, the sampling circuit further includes a second control unit, the input terminal of which is connected to the output terminal of the current sensor, for generating a measured value of the line voltage based on the current signal detected by the current sensor.

[0014] Optionally, the resistor sampling unit includes a sampling resistor with a resistance in the megaohm range, and the inductance of the grid-side inductor is in the microhenry range.

[0015] In a second aspect, this application provides an inverter that includes a sampling circuit as described in the first aspect.

[0016] In the various embodiments provided in this application, the line voltage between every two phases of the output circuit is sampled using three resistor sampling units to obtain the measured value of the line voltage. This achieves sampling of the inverter's AC output voltage without the need for an additional virtual neutral point. This not only simplifies the circuit structure but also effectively avoids introducing high-frequency harmonic paths and suppresses high-frequency harmonics generated by the sampling circuit. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the voltage sampling principle of an inverter in related technologies;

[0019] Figure 2 This is a circuit diagram of the LCL filter structure in an inverter in related technologies;

[0020] Figure 3 This is a single-phase equivalent circuit diagram for multiple inverters operating in parallel in related technologies.

[0021] Figure 4 for Figure 3 The equivalent circuit diagram of an inverter in operation;

[0022] Figure 5 A schematic diagram of the sampling circuit structure of an inverter is provided for one embodiment of this application;

[0023] Figure 6 A schematic diagram of a sampling circuit for an inverter is provided as an embodiment of this application;

[0024] Figure 7 A schematic diagram of a sampling circuit for an inverter is provided for another embodiment of this application;

[0025] Figure 8 An equivalent circuit diagram of the operating state of an inverter is provided for one embodiment of this application. Detailed Implementation

[0026] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0027] In the description of the embodiments of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0028] Inverters are widely used in distributed generation, power regulation, and grid connection of new energy sources. During inverter operation, it is necessary to sample the voltage on the AC output side of the inverter to determine whether the current operating conditions are met. In related technologies, a virtual neutral point is typically constructed on the AC output side of the inverter using a sampling capacitor, and a sampling resistor is used to sample the voltage between each phase output circuit and the virtual neutral point. This sampling circuit is located on the side of the inverter's AC switch closest to the grid, and can complete the sampling of phase voltages even when the inverter is not powered on, thus obtaining the measured values ​​of each phase output voltage.

[0029] Because the inverter's AC output side employs an LCL filter structure, which includes an inverter-side inductor, a filter capacitor, and a grid-side inductor, the inverter-side inductor and filter capacitor are located on the side of the AC switch closest to the inverter and connected to one end of the AC switch. The grid-side inductor is located on the side of the AC switch closest to the grid and connected to the other end of the AC switch. In scenarios where multiple inverters are used in parallel, when some inverters are in a shutdown state, their sampling capacitors and corresponding grid-side inductors form a series branch connected to the AC output side of the operating inverters. This may affect the resonant frequency of the operating inverter's LCL filter structure. When this resonant frequency approaches the operating inverter's switching frequency, because the inverter arm voltage contains high-amplitude switching frequency components, high-frequency harmonic components are likely to appear in the inverter output current, thereby reducing the quality of the inverter's output power.

[0030] by Figure 1Taking the inverter shown as an example, in the three-phase output circuit of this inverter, each phase output circuit is equipped with a sampling capacitor C. The three sampling capacitors C are connected in a star configuration to form a virtual neutral point N'. Each sampling capacitor C, in conjunction with the sampling resistor R of each phase output circuit, can be used to sample the voltage between each phase output circuit and the virtual neutral point N' to obtain the measured value of the output voltage of each phase of the inverter. However, as... Figure 2 As shown, since the AC output side of the inverter adopts an LCL filter structure consisting of inverter-side inductor L1, filter capacitor C1, and grid-side inductor L2, in a scenario where N inverters are used in parallel, such as N=4, its single-phase equivalent circuit is as follows. Figure 3 As shown. In Figure 3 In the circuit shown, when only one inverter is running and the others are shut down, the sampling capacitor C in the shut-down inverter forms a series branch with the grid-side inductor L2 and is connected to the grid. The equivalent circuit is as follows: Figure 4 As shown, this series branch is highly susceptible to resonance with other inverters operating in the power grid, potentially introducing high-frequency harmonic components into the inverter's output current. This not only degrades the quality of the inverter's output power but may also adversely affect the stability of the entire inverter system.

[0031] Therefore, how to suppress high-frequency harmonics generated by the sampling circuit while achieving effective sampling of the inverter's AC output voltage has become a key technical problem that urgently needs to be solved.

[0032] Please see Figure 5This application provides a sampling circuit 110 for an inverter. The inverter includes a three-phase output circuit 120, each phase output circuit including an AC switch 121 connected to the power grid. The side of the AC switch 121 closest to the inverter is connected to an inverter-side inductor L1 and a filter capacitor C1, while the side of the AC switch 121 closest to the power grid is connected to a grid-side inductor L2. The sampling circuit 110 includes three resistor sampling units 111. Each resistor sampling unit 111 includes: a first resistor sampling unit, whose first end is connected to the node between the AC switch 121 and the grid-side inductor L2 in the first phase output circuit, and whose second end is connected to the node between the AC switch 121 and the grid-side inductor L2 in the second phase output circuit, for sampling the line voltage between the first and second phase output circuits; and a second resistor sampling unit, whose first end is connected to the node between the AC switch 121 and the grid-side inductor L2 in the second phase output circuit, and whose second end is connected to the node between the AC switch 121 and the grid-side inductor L2 in the third phase output circuit, for sampling the line voltage between the second and third phase output circuits. The third resistor sampling unit has its first end connected to the node between AC switch 121 and grid-side inductor L2 in the third phase output circuit, and its second end connected to the node between AC switch 121 and grid-side inductor L2 in the first phase output circuit. It is used to sample the line voltage between the third phase output circuit and the first phase output circuit.

[0033] In this embodiment, the three-phase output circuit 120 consists of three sets of output circuits: phase A, phase B, and phase C. Each phase output circuit is equipped with an AC switch 121 connected to the power grid. The AC switch 121 can be a relay, contactor, or other controllable conducting device, used to control the electrical connection or disconnection between the inverter and the power grid. The side of the AC switch 121 closest to the inverter (i.e., the inverter side) is connected to the inverter-side inductor L1 and the filter capacitor C1, while the side closest to the power grid (i.e., the grid side) is connected to the grid-side inductor L2. The inverter-side inductor L1, the filter capacitor C1, and the grid-side inductor L2 together form an LCL filter structure, which can be used to suppress high-frequency harmonics in the inverter output current and improve the quality of the inverter output power.

[0034] The resistor sampling unit 111 is a signal sampling unit with resistive characteristics, which can be used to sample voltage or current signals. The resistor sampling unit 111 can consist of one or more resistive elements, which can be connected in series or parallel. Alternatively, one or more resistive elements can be further combined with signal conditioning circuits (such as current sensors, operational amplifiers, etc.) to form a composite sampling structure. The resistor sampling unit 111 is located between two-phase output circuits. By sampling the voltage or current between the two-phase output circuits in real time, the measured values ​​of the output voltage of each phase can be obtained. Based on the measured line voltage values, the current operating status of the inverter can be determined, such as output power performance and whether the output voltage meets grid connection conditions, thereby facilitating real-time monitoring and dynamic adjustment of the inverter output status.

[0035] The sampling circuit 110 may include three resistor sampling units 111, each corresponding to the line voltage sampling between any two phases in the three-phase output circuit. Specifically, the first resistor sampling unit has its first end connected to the node between the AC switch 121 and the grid-side inductor L2 in the first phase output circuit, and its second end connected to the node between the AC switch 121 and the grid-side inductor L2 in the second phase output circuit, forming a line voltage sampling path between the first and second phase output circuits. The second resistor sampling unit has its first end connected to the node between the AC switch 121 and the grid-side inductor L2 in the second phase output circuit, and its second end connected to the node between the AC switch 121 and the grid-side inductor L2 in the third phase output circuit, forming a line voltage sampling path between the second and third phase output circuits. The third resistor sampling unit has its first end connected to the node between the AC switch 121 and the grid-side inductor L2 in the third phase output circuit, and its second end connected to the node between the AC switch 121 and the grid-side inductor L2 in the first phase output circuit, forming a line voltage sampling path between the third and first phase output circuits. Three resistor sampling units are used to collect voltage signals between different phase lines, forming a closed-loop line voltage measurement structure to achieve comprehensive monitoring of the inverter's three-phase AC output voltage. Since each resistor sampling unit uses resistive devices and its connection point is located at the node between AC switch 121 and grid-side inductor L2, it avoids introducing high-frequency harmonic coupling paths and can more accurately reflect the voltage variation characteristics from the inverter output to the grid, thus helping to improve the power quality of the inverter output.

[0036] Therefore, the sampling circuit 110 of this embodiment samples the line voltage between every two phases of the output circuit through three resistor sampling units 111 to obtain the measured value of the line voltage. Since the resistor sampling unit 111 has resistive characteristics and does not have energy storage capacity, it can effectively avoid high-frequency harmonic paths that may be introduced in related sampling schemes. Compared with the voltage sampling method based on constructing a virtual neutral point based on sampling capacitors, the sampling circuit 110 of this embodiment does not need to introduce an additional virtual neutral point to achieve accurate sampling of the inverter's AC output voltage. This not only simplifies the circuit structure but also effectively suppresses high-frequency harmonic interference generated by the sampling path, thereby improving the quality of the inverter's output power and thus improving the stability of the inverter system.

[0037] In some embodiments, the resistance sampling unit 111 includes: at least two sampling resistors connected in series for dividing the line voltage; and a voltage acquisition module, the input of which is connected to the voltage divider node between adjacent sampling resistors for acquiring the voltage signal after voltage division.

[0038] In this embodiment, the resistor sampling unit 111 can adopt a voltage divider sampling structure, connecting multiple sampling resistors in series to perform voltage division processing on the line voltage to be acquired, thereby achieving amplitude attenuation of the high-voltage signal. In this series voltage divider structure, the connection nodes between adjacent sampling resistors constitute voltage divider nodes. The input terminal of the voltage acquisition module is connected to the voltage divider nodes to acquire a voltage signal proportional to the line voltage for subsequent circuit monitoring and processing. The voltage acquisition module can, for example, adopt a differential acquisition structure, with its two input terminals connected to the two voltage divider nodes between the sampling resistors, or one input terminal connected to the voltage divider node between the sampling resistors and the other input terminal connected to the corresponding reference node. This resistor sampling unit 111 can achieve accurate sampling of the AC output line voltage without significantly affecting the electrical characteristics of the original circuit, and has the advantages of simple structure, fast response speed, and high linearity. By reasonably selecting the resistance value of the sampling resistor, the output signal of the resistor sampling unit 111 can meet the requirements of the subsequent circuit, thereby improving the reliability of the sampling circuit 110.

[0039] In some embodiments, at least two series-connected sampling resistors include a first terminal resistor, an intermediate resistor, and a second terminal resistor connected in series. The input terminal of the voltage acquisition module is connected to both ends of the intermediate resistor to acquire the voltage signal across the intermediate resistor, wherein the resistance value of the intermediate resistor is smaller than the resistance values ​​of the first terminal resistor and the second terminal resistor. The resistance values ​​of the first terminal resistor and the second terminal resistor are in the megaohm range, and the resistance value of the intermediate resistor is in the kiloohm range.

[0040] In this embodiment, the resistance sampling unit 111 adopts a series structure with graded resistance values, including a first-terminal resistor, an intermediate resistor, and a second-terminal resistor connected in series, forming a complete voltage divider path. The first-terminal resistor, intermediate resistor, and second-terminal resistor can be a single resistor or a combination of multiple resistors. The voltage acquisition module adopts a differential acquisition structure, with its two input terminals connected to both ends of the intermediate resistor to acquire the voltage drop across the intermediate resistor, thereby obtaining a voltage signal proportional to the measured line voltage.

[0041] To reduce power loss of the sampling resistor while ensuring sampling accuracy, in this embodiment, the resistance value of the intermediate resistor is set to be smaller than that of the first and second terminal resistors. For example, the resistance value of the intermediate resistor can be set to the kiloohm level, while the resistance values ​​of the first and second terminal resistors can be set to the megaohm level, forming a voltage divider structure where the resistance values ​​at both terminals are much larger than that of the intermediate resistor. This resistance configuration allows the first and second terminal resistors to bear the main voltage drop task, achieving effective isolation and protection of high-voltage signals. The intermediate resistor, located in the middle of the voltage divider path, exhibits relatively stable voltage changes across its terminals, enabling it to more accurately reflect the changing trend of the measured line voltage. Connecting the input terminal of the voltage acquisition module to both ends of this intermediate resistor improves the accuracy of signal sampling and its anti-interference capability, thereby contributing to improved reliability of the sampling circuit 110.

[0042] For details, please refer to Figure 6In this embodiment, the three resistor sampling units 111 of the sampling circuit 110 correspond to the line voltage sampling between any two phases (phase A and phase B, phase B and phase C, phase C and phase A) in the three-phase output circuit. The resistor sampling unit 111 adopts a series structure with graded resistance values, including a first-terminal resistor R1, an intermediate resistor, and a second-terminal resistor R2 connected in series. The intermediate resistor includes a third resistor R3 and a fourth resistor R4 connected in series. The voltage acquisition module 1111 adopts a differential acquisition structure, with its two input terminals connected to the two ends of the intermediate resistor (i.e., the third resistor R3 and the fourth resistor R4), used to acquire the voltage drop across the third resistor R3 and the fourth resistor R4 to obtain a differential voltage signal proportional to the measured line voltage. To reduce the power loss of the sampling resistors while ensuring sampling accuracy, the resistance values ​​of the third resistor R3 and the fourth resistor R4 are both set to the kiloohm level, while the resistance values ​​of the first-terminal resistor R1 and the second-terminal resistor R2 are both set to the megaohm level. This resistor configuration allows the first-terminal resistor R1 and the second-terminal resistor R2 to handle the main voltage drop, effectively isolating and protecting high-voltage signals. The third-terminal resistor R3 and the fourth-terminal resistor R4, located in the middle of the voltage divider path, have relatively stable potentials, enabling them to more accurately reflect the dynamic changes in the measured line voltage. Connecting the two input terminals of the voltage acquisition module 1111 to the two ends of the third-terminal resistor R3 and the fourth-terminal resistor R4 improves the accuracy of signal sampling and its anti-interference capability, thereby enhancing the reliability of the sampling circuit 110.

[0043] In some embodiments, the sampling circuit 110 further includes a first control unit, the input terminal of which is connected to the output terminal of the voltage acquisition module 1111, for generating a measured value of the line voltage based on the voltage signal acquired by the voltage acquisition module 1111.

[0044] In this embodiment, the first control unit is connected to the voltage acquisition module 1111 and can be used to perform signal processing and calculation on the acquired differential voltage signal to generate a measured value corresponding to the measured line voltage. Specifically, the first control unit can perform analog-to-digital conversion on the analog differential voltage signal output by the voltage acquisition module 1111, and perform linear or nonlinear calculations on the converted digital signal to obtain the measured value of the corresponding line voltage. Based on the measured value of the line voltage, the first control unit can further determine the current operating status of the inverter, such as whether the output voltage meets the grid connection conditions and whether the output power quality meets the standard requirements, thereby realizing real-time monitoring and dynamic adjustment of the inverter output status.

[0045] by Figure 6For example, in this embodiment, the sampling circuit 110 includes a first control unit 112. The input terminal of the first control unit 112 is connected to the output terminal of the voltage acquisition module 1111. It can perform analog-to-digital conversion on the analog differential voltage signal output by the voltage acquisition module 1111, and perform linear or nonlinear calculations on the converted digital signal to obtain the measured value of the corresponding line voltage. Based on the measured value of the line voltage, the first control unit 112 can further determine the current operating status of the inverter, such as whether the output voltage meets the grid connection conditions and whether the output power quality meets the standard requirements, thereby realizing real-time monitoring and dynamic adjustment of the inverter output status.

[0046] In some embodiments, the resistance sampling unit 111 includes: at least one sampling resistor; and a current sensor connected in series with the sampling resistor for detecting the current signal in the sampling resistor. The total resistance of the sampling resistor is in the megaohm range.

[0047] In this embodiment, the resistance sampling unit 111 adopts a sampling structure that combines a sampling resistor and a current sensor. The current sensor has good electrical isolation characteristics, which can electrically isolate the sampling circuit 110 from the output circuit 120, thereby improving the anti-interference capability and operational reliability of the sampling circuit 110. Specifically, the current sensor is connected in series with the sampling resistor to detect the current flowing through the sampling resistor in real time and obtain a current signal characterizing the line voltage change characteristics between the two-phase output circuits.

[0048] The sampling resistor can be a single resistor or a resistor network composed of multiple resistors connected in series or parallel. In this embodiment, the total resistance of the sampling resistor is set to be in the megaohm range. Since the total resistance of the sampling resistor is in the megaohm range, the current flowing through the sampling resistor can be effectively limited, allowing only small currents to pass through, thereby reducing the power loss of the sampling resistor and improving the energy efficiency ratio and operational stability of the sampling circuit 110. A current sensor is connected in series with the sampling resistor to detect the small current signal flowing through the sampling resistor. Based on this small current signal, the corresponding line voltage measurement value can be obtained through further processing and calculation by subsequent circuits. This resistor sampling unit 111 has the characteristics of simple structure, low power consumption and good electrical isolation, and can accurately sample the AC output line voltage of each phase through current acquisition without significantly affecting the electrical characteristics of the original circuit.

[0049] For details, please refer to Figure 7In this embodiment, the three resistor sampling units 111 of the sampling circuit 110 correspond to the line voltage sampling between any two phases (phase A and phase B, phase B and phase C, phase C and phase A) in the three-phase output circuit. The resistor sampling unit 111 adopts a sampling structure that combines a sampling resistor with a current sensor 1112. The current sensor 1112 has good electrical isolation characteristics, which can achieve effective electrical isolation between the sampling circuit 110 and the output circuit 120, improving the anti-interference capability and operational reliability of the sampling circuit 110. The sampling resistor is a resistor network composed of multiple resistors (first resistor R11, second resistor R12, third resistor R13, and fourth resistor R14) connected in series. The sum of the resistance values ​​of the first resistor R11, second resistor R12, third resistor R13, and fourth resistor R14 is in the megaohm range, which can effectively limit the current flowing through the resistor network, allowing only a small current to pass through, thereby reducing the overall power consumption of the sampling resistor. The current sensor 1112 is connected in series with a resistor network, enabling real-time detection of the current flowing through the sampling resistor and acquiring a small current signal characterizing the line voltage variation between the two-phase output circuits. Based on the detected small current signal, further processing and calculation by subsequent circuits yield the measured value of the line voltage between the corresponding two-phase output circuits. This resistor sampling unit 111 achieves accurate sampling of the AC output line voltage of each phase through current acquisition, featuring simple structure, low power consumption, and good electrical isolation, thereby improving the reliability of the sampling circuit 110.

[0050] In some embodiments, the sampling circuit 110 further includes a second control unit, the input of which is connected to the output of the current sensor 1112, for generating a measured value of the line voltage based on the current signal detected by the current sensor.

[0051] In this embodiment, the second control unit is connected to the current sensor 1112 and can be used to process and calculate the small current signal collected by the current sensor 1112 to generate a measured value corresponding to the measured line voltage. The second control unit and the first control unit can be the same or different controllers. In a specific example, both the first control unit and the second control unit can be the inverter controller. Specifically, the second control unit can perform analog-to-digital conversion on the analog current signal output by the current sensor 1112, and perform corresponding calculations on the converted digital signal based on a preset correspondence between line voltage and current, thereby obtaining the measured value of the corresponding line voltage. Based on the measured value of the line voltage, the second control unit can further determine the current operating status of the inverter, such as whether the output voltage meets the grid connection conditions and whether the output power quality meets the standard requirements, thereby realizing real-time monitoring and dynamic adjustment of the inverter output status.

[0052] by Figure 7For example, in this embodiment, the sampling circuit 110 includes a second control unit 113. The input terminal of the second control unit 113 is connected to the output terminal of the current sensor 1112. It can perform analog-to-digital conversion on the analog current signal output by the current sensor 1112, and perform corresponding calculations on the converted digital signal based on a preset correspondence between line voltage and current, thereby obtaining the measured value of the corresponding line voltage. Based on the measured value of the line voltage, the second control unit 113 can further determine the current operating state of the inverter, thereby realizing real-time monitoring and dynamic adjustment of the inverter output state.

[0053] The sampling circuit 110 of the inverter provided in this application embodiment uses a megaohm-level sampling resistor instead of the sampling capacitor used in related technologies. Since the grid-side inductor L2 in the inverter is typically configured in the microhenry level, such as 10uH, while the sampling resistor in this application embodiment is preferably set to the megaohm level, such as 10MΩ, when the inverter operating frequency is below 20kHz, the impedance formed by the sampling resistor and the grid-side inductor L2 is predominantly resistive, thus having a smaller impact on the original LCL filter structure of the inverter. Furthermore, the sampling resistor has good damping characteristics for high-frequency components, effectively suppressing high-frequency harmonic currents, including switching frequency harmonics, which helps improve the power quality of the inverter output. In application scenarios where multiple inverters operate in parallel, such as N=4, when only one inverter is in operation and the others are in shutdown state, the equivalent circuit is described in [reference needed]. Figure 8 As shown. The circuit 110 can effectively avoid introducing high-frequency harmonic paths and suppress high-frequency harmonics generated by the sampling circuit, thereby helping to improve the quality of the inverter's output power.

[0054] This application also provides an inverter that includes a sampling circuit 110 as described in any of the above embodiments.

[0055] The specific functions and effects of each module in the inverter can be explained by referring to the aforementioned embodiments, and will not be repeated here.

[0056] It is understood that the term "connection" in the embodiments of this application can be interpreted as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc. can transmit electrical signals or data to each other.

[0057] It is understood that the specific examples in this document are only intended to help those skilled in the art better understand the embodiments of this application, and are not intended to limit the scope of this utility model.

[0058] It is understood that in the various embodiments of this application, the sequence number of each process does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0059] It is understood that the various embodiments described in this application can be implemented individually or in combination, and the embodiments of this application are not limited in this respect.

[0060] Unless otherwise stated, all technical and scientific terms used in the embodiments of this application have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The term "and / or" as used in this application includes any and all combinations of one or more of the associated listed items. The singular forms "a," "the," and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0061] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0062] The above description is merely a specific embodiment of this application, but the protection scope of this utility model 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 this application should be included within the protection scope of this application. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. A sampling circuit for an inverter, characterized in that, The inverter includes a three-phase output circuit, each phase of which includes an AC switch connected to the grid. The side of the AC switch closest to the inverter is connected to an inverter-side inductor and a filter capacitor, while the side of the AC switch closest to the grid is connected to a grid-side inductor. The sampling circuit includes three resistance sampling units, and the three resistance sampling units include: The first resistor sampling unit has its first end connected to the node between the AC switch and the grid-side inductor in the first phase output circuit, and its second end connected to the node between the AC switch and the grid-side inductor in the second phase output circuit, for sampling the line voltage between the first phase output circuit and the second phase output circuit. The second resistor sampling unit has its first end connected to the node between the AC switch and the grid-side inductor in the second phase output circuit, and its second end connected to the node between the AC switch and the grid-side inductor in the third phase output circuit, for sampling the line voltage between the second phase output circuit and the third phase output circuit; The third resistor sampling unit has its first end connected to the node between the AC switch and the grid-side inductor in the third phase output circuit, and its second end connected to the node between the AC switch and the grid-side inductor in the first phase output circuit, for sampling the line voltage between the third phase output circuit and the first phase output circuit.

2. The sampling circuit according to claim 1, characterized in that, The resistance sampling unit includes: At least two sampling resistors connected in series are used to divide the line voltage; A voltage acquisition module, the input terminal of which is connected to the voltage divider node between the sampling resistors, is used to acquire the voltage signal after voltage division.

3. The sampling circuit according to claim 2, characterized in that, The at least two series-connected sampling resistors include a first terminal resistor, an intermediate resistor, and a second terminal resistor connected in series in sequence. The input terminal of the voltage acquisition module is connected to both ends of the intermediate resistor to acquire the voltage signal across the intermediate resistor, wherein the resistance value of the intermediate resistor is less than the resistance values ​​of the first terminal resistor and the second terminal resistor.

4. The sampling circuit according to claim 3, characterized in that, The resistance values ​​of the first and second terminal resistors are in the megaohm range, and the resistance value of the intermediate resistor is in the kiloohm range.

5. The sampling circuit according to any one of claims 2 to 4, characterized in that, The sampling circuit further includes a first control unit, the input terminal of which is connected to the output terminal of the voltage acquisition module, for generating the measured value of the line voltage based on the voltage signal acquired by the voltage acquisition module.

6. The sampling circuit according to claim 1, characterized in that, The resistance sampling unit includes: At least one sampling resistor; A current sensor, connected in series with the sampling resistor, is used to detect the current signal in the sampling resistor.

7. The sampling circuit according to claim 6, characterized in that, The total resistance of the sampling resistors is in the megaohm range.

8. The sampling circuit according to claim 6 or 7, characterized in that, The sampling circuit further includes a second control unit, the input terminal of which is connected to the output terminal of the current sensor, for generating a measured value of the line voltage based on the current signal detected by the current sensor.

9. The sampling circuit according to claim 1, characterized in that, The resistor sampling unit includes a sampling resistor with a resistance value in the megaohm range, and the inductance of the grid-side inductor is in the microhenry range.

10. An inverter, characterized in that, The inverter includes a sampling circuit as described in any one of claims 1 to 9.

Images