Ground impedance detection device, method and inverter

Abstract

A ground impedance detection device, method and inverter. The detection device comprises a signal source, a coupling impedance network, a voltage dividing network, a sampling module and a controller; the signal source is used to provide an excitation signal; the coupling impedance network is connected with the signal source and used to couple the excitation signal between the DC input end and the AC output end of the inverter; the voltage dividing network is used to divide the voltage between the DC input end and the AC output end to provide a divided voltage; the sampling module is connected with the voltage dividing network and used to sample the divided voltage to obtain a sampling voltage; the controller is connected with the signal source and the sampling module respectively and used to control the signal source to provide at least one excitation signal and obtain the ground impedance of the DC input end of the inverter according to the at least one excitation signal and the corresponding sampling voltage under the at least one excitation signal.

Description

Technical Field

[0001] This application relates to the field of photovoltaic power generation technology, and in particular to a grounding impedance detection device, method and inverter. Background Technology

[0002] In a grid-connected photovoltaic system, if the DC resistance of the output terminal of the photovoltaic module to ground is too low, it will lead to the risk of short circuit on both the DC and AC sides, causing safety hazards to the system. Therefore, grid-connected photovoltaic systems are required to perform grounding impedance testing on the DC side.

[0003] Since most inverters currently have metal casings that are grounded, the grounding impedance detection method uses the casing grounding potential point. The detection method generally involves connecting resistors with fixed resistance values ​​between the casing grounding potential point and the positive and negative terminals of the photovoltaic module through the switching of relays or semiconductor switches. At the same time, the voltage value at the casing grounding potential point is collected sequentially, and the grounding impedance value from the two ends of the photovoltaic module to ground is calculated based on the voltage value.

[0004] Since these methods all utilize the chassis grounding point, they are not suitable for inverters with non-metallic chassis and no grounding wire connection. Summary of the Invention

[0005] According to various embodiments of this application, a grounding impedance detection device, method, and inverter are provided.

[0006] This application provides a grounding impedance detection device, including a signal source, a coupling impedance network, a voltage divider network, a sampling module, and a controller;

[0007] The signal source is used to provide excitation signals;

[0008] The coupling impedance network is connected to the signal source and is used to couple the excitation signal between the DC input terminal and the AC output terminal of the inverter, wherein the AC output terminal of the inverter is connected to the power grid;

[0009] The voltage divider network is used to divide the voltage between the DC input terminal and the AC output terminal to provide a divided voltage.

[0010] The sampling module is connected to the voltage divider network and is used to sample the voltage divider voltage to obtain the sampled voltage;

[0011] The controller is connected to the signal source and the sampling module respectively, and is used to control the signal source to provide at least one excitation signal, and to obtain the grounding impedance of the DC input terminal of the inverter based on the at least one excitation signal and the sampling voltage corresponding to the at least one excitation signal.

[0012] In some embodiments, the controller is further configured to control the signal source to provide a first excitation signal and a second excitation signal respectively, the sampling module is configured to acquire a first sampling voltage under the first excitation signal and a second sampling voltage under the second excitation signal respectively, and the controller is further configured to acquire the grounding impedance of the DC input terminal of the inverter based on the difference between the first excitation signal and the second excitation signal and the difference between the first sampling voltage and the second sampling voltage.

[0013] In some embodiments, one output terminal of the signal source is connected to one of the DC input terminals, and the other output terminal is connected to one of the AC output terminals through the coupling impedance network.

[0014] In some embodiments, the signal source includes a DC voltage conversion circuit or a rectifier circuit.

[0015] In some embodiments, the signal source includes a switching circuit, which includes at least one switch, and outputs different excitation signals by controlling the on state of the at least one switch.

[0016] In some embodiments, the inverter includes a full-bridge circuit or a half-bridge circuit connected to the DC input terminal, the signal source is a part of the full-bridge circuit or the half-bridge circuit, and the excitation signal is the DC input voltage or 0 at the DC input terminal.

[0017] In some embodiments, the voltage divider network is connected between one of the DC input terminals and one of the AC output terminals of the inverter.

[0018] In some embodiments, the voltage divider network is connected in series with the coupling impedance network.

[0019] In some embodiments, the sampling module includes a first sampling unit connected to the voltage divider network for acquiring the sampling voltage.

[0020] In some embodiments, the first sampling unit includes a filtering circuit and a sampling circuit. The filtering circuit is connected to the voltage divider network and the sampling circuit respectively, and is used to filter out voltage components other than the frequency of the excitation signal in the sampled voltage.

[0021] In some embodiments, the controller includes a filtering unit for filtering out voltage components in the sampled voltage other than the frequency of the excitation signal.

[0022] In some embodiments, the sampling module further includes a second sampling unit connected to the DC input terminal of the inverter, for acquiring the DC input voltage and providing it to the controller. The controller is used to control the signal source to provide at least two different excitation signals, and to acquire the grounding impedance of the DC input terminal of the inverter based on the at least two different excitation signals and the sampling voltage and the DC input voltage under the at least two different excitation signals.

[0023] In some embodiments, the excitation signal is a DC signal, an AC signal, or a signal resulting from the superposition of a DC signal and an AC signal.

[0024] In some embodiments, the controller is used to compare the grounding impedance with a preset threshold to determine whether the grounding impedance is abnormal.

[0025] This application also provides a grounding impedance detection method for detecting the grounding impedance of the DC input terminal of an inverter, the method comprising the following steps:

[0026] At least one excitation signal is coupled between the DC input terminal and the AC output terminal of the inverter;

[0027] The voltage divider voltage between the DC input terminal and the AC output terminal of the inverter is sampled to obtain the sampled voltage.

[0028] The grounding impedance of the inverter's DC input terminal is obtained based on the at least one excitation signal and the corresponding sampling voltage under the at least one excitation signal.

[0029] In some embodiments, the method further includes the following steps:

[0030] The first excitation signal and the second excitation signal are respectively coupled between the DC input terminal and the AC output terminal of the inverter;

[0031] The first sampled voltage under the first excitation signal and the second sampled voltage under the second excitation signal are obtained respectively, and the grounding impedance of the DC input terminal of the inverter is obtained based on the difference between the first excitation signal and the second excitation signal and the difference between the first sampled voltage and the second sampled voltage.

[0032] In some embodiments, the method further includes the following steps:

[0033] At least two different excitation signals are coupled between the DC input and AC output of the inverter;

[0034] Obtain the DC input voltage and the sampling voltage of the inverter DC input terminal corresponding to the at least two different excitation signals, and obtain the grounding impedance of the inverter DC input terminal based on the at least two different excitation signals, the sampling voltage and the DC input voltage under the at least two different excitation signals.

[0035] In some embodiments, the method further includes the following steps:

[0036] The grounding impedance is compared with a preset threshold to determine whether the grounding impedance is abnormal.

[0037] This application also provides an inverter, including the grounding impedance detection device and the DC / AC converter as described above, wherein the DC / AC converter is connected between the DC input terminal and the AC output terminal of the inverter for converting DC power into AC power.

[0038] According to the grounding impedance detection device, method and inverter provided in this application, a high-impedance loop is constructed by setting a signal source and a coupling impedance network between the DC input terminal and the AC output terminal of the inverter. At the same time, an excitation signal is introduced into the loop, and the grounding impedance of the inverter is obtained according to the excitation signal and the sampling voltage under the excitation signal. Thus, the grounding impedance of the DC input terminal of the inverter can be detected without the inverter having a grounding wire. Moreover, the detection device has a simple structure and is easy to implement.

[0039] Details of one or more embodiments of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0040] To better describe and illustrate embodiments and / or examples of the applications disclosed herein, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the embodiments and / or examples currently described, or the best mode of conduct of these applications as currently understood.

[0041] Figure 1 This is a structural block diagram of a power generation system according to some embodiments.

[0042] Figure 2 This is a schematic diagram of a grounding impedance detection device according to some embodiments.

[0043] Figure 3 for Figure 2 The DC equivalent circuit model.

[0044] Figure 4 for Figure 2 The AC equivalent circuit model.

[0045] Figure 5 This is a schematic diagram of a grounding impedance detection device according to some embodiments.

[0046] Figure 6 This is a schematic diagram of a grounding impedance detection device according to some embodiments.

[0047] Figure 7 for Figure 6 The DC equivalent circuit model.

[0048] Figure 8 This is a schematic diagram of the structure of a signal source according to some embodiments.

[0049] Figure 9 This is a schematic diagram of the structure of a signal source according to some embodiments.

[0050] Figure 10 This is a schematic diagram of the structure of a signal source according to some embodiments.

[0051] Figure 11 This is a schematic diagram of the structure of a signal source according to some embodiments.

[0052] Figure 12 This is a schematic diagram of the structure of a first sampling unit according to some embodiments.

[0053] Figure 13 This is a schematic flowchart of a grounding impedance detection method according to some embodiments.

[0054] Reference numerals: 100, Inverter; 110, Grounding impedance detection device; 111, Coupling impedance network; 112, Voltage divider network; 113, Sampling module; 113a, First sampling unit; 113b, Second sampling unit; 113c, Third sampling unit; 114, Controller; 115, Low-pass filter; 116, Sampling circuit; 120, DC / AC converter; V c Signal source; V pv DC input voltage; R1, first resistor; R2, second resistor; R3, third resistor; R4, fourth resistor; R x Fifth resistor; R E1 1. Grounding impedance of the negative terminal of the DC input; R E2 1. Grounding impedance of the positive terminal of DC input; PE, grounding point; 200, DC source; 300, power grid. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of this invention.

[0056] When a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be an intervening component. When a component is considered to be "connected in series" or "connected in parallel" to another component, it can be directly connected in series or in parallel to the other component or there may be an intervening component.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0058] The grounding impedance detection device, method, and inverter provided in this application can be applied to power generation systems.

[0059] Figure 1 A structural block diagram of a power generation system provided in this application is shown, such as... Figure 1 As shown, the power generation system includes an inverter 100 and a DC source 200 connected to the DC input terminal of the inverter 100. The inverter 100 is used to convert the DC power provided by the DC source 200 into AC power, and further provide the AC power to the power grid 300.

[0060] In some embodiments, the DC source 200 may be a photovoltaic module.

[0061] In some embodiments, the DC source 200 may be a photovoltaic string or array formed by connecting multiple photovoltaic modules in series and parallel, or it may be a battery or other types of renewable energy.

[0062] Inverter 100 can be an isolated or non-isolated inverter, and can be a single-stage or multi-stage conversion inverter.

[0063] In some embodiments, the chassis of inverter 100 is not grounded.

[0064] The power grid 300 can be a single-phase power grid, a three-phase power grid, or a split-phase power grid.

[0065] The far end of the power grid 300 is grounded through a neutral wire. This grounding point can be the positive end or the negative end of the power grid 300. If it is a split-phase power grid, it can also be at the midpoint of the power grid 300. The location of this grounding point does not affect the detection of the grounding impedance in the embodiments of this application.

[0066] like Figure 1 As shown, the inverter 100 includes a DC / AC converter 120 and a grounding impedance detection device 110. The grounding impedance detection device 110 includes a signal source V. c The system includes a coupling impedance network 111, a voltage divider network 112, a sampling module 113, and a controller 114.

[0067] Signal source V c It is connected between the DC input terminal and the AC output terminal of the inverter 100 to provide an excitation signal;

[0068] Coupled impedance network 111 and signal source V c A connection is provided to couple the excitation signal between the DC input terminal and the AC output terminal of the inverter 100, wherein the AC output terminal of the inverter 100 is connected to the power grid 300.

[0069] Voltage divider network 112 is used to divide the voltage between the DC input terminal and the AC output terminal to provide a voltage divider voltage;

[0070] The sampling module 113 is connected to the voltage divider network 112 and is used to obtain the sampling voltage of the voltage divider network 112.

[0071] Controller 114 is connected to signal source V respectively c Connected to sampling module 113, controller 114 is used to control signal source V. c Provide at least one excitation signal, and obtain the grounding impedance of the DC input terminal of the inverter 100 based on the at least one excitation signal and the corresponding sampling voltage under the at least one excitation signal.

[0072] In this embodiment, a signal source V is provided between the DC input terminal and the AC output terminal of the inverter 100. c A high-impedance loop is constructed using the coupling impedance network 111. An excitation signal is introduced into this high-impedance loop, and the grounding impedance of the DC input terminal of the inverter 100 is obtained based on the excitation signal and the sampled voltage under the excitation signal.

[0073] It should be noted that the grounding impedance of the DC input terminal of inverter 100 is the same as the grounding impedance of DC source 200 to ground.

[0074] Signal source V c It can draw power from a DC source 200 or from other power sources in the power generation system. Its input can be either DC or AC.

[0075] In some embodiments, signal source V c The first output terminal is connected to the negative DC input terminal of DC / AC converter 120 (i.e., the negative DC input terminal of inverter 100), and the signal source V c The second output terminal is connected to one of the AC output terminals of the DC / AC converter 120.

[0076] In some embodiments, signal source V cThe first output terminal is connected to the positive DC input terminal of the DC / AC converter 120 (i.e., the positive DC input terminal of the inverter 100). Under the control of the controller 114, the signal source V... c The second output terminal generates at least one controlled excitation signal relative to the first output terminal.

[0077] In some embodiments, the grounding impedance detection device 110 can be used in an inverter 100 with a non-metallic housing and no grounding wire to detect the grounding impedance of the DC source 200 when the inverter 100 is not connected to a grounding wire.

[0078] Figure 2 A schematic diagram of the structure of a grounding impedance detection device according to an embodiment of this application is shown, as follows: Figure 2 As shown, R E1 and R E2 These are the grounding impedances of the positive DC output terminal (i.e., the positive DC input terminal of inverter 100) and the negative DC output terminal (i.e., the negative DC input terminal of inverter 100), respectively. Signal source V c The coupling impedance network 111, used to provide the excitation signal, includes a first resistor R1 and a signal source V. c The output terminal is connected in series between one of the DC input terminals and one of the AC output terminals of the DC / AC converter 120, wherein the first resistor R1 is used to limit the impedance value between the DC side and the AC side of the inverter 100 when it is operating normally.

[0079] Specifically, signal source V c The first output terminal is connected to the negative DC input terminal of the DC / AC converter 120, the second output terminal is connected to the first terminal of the first resistor R1, and the second terminal of the first resistor R1 is connected to the first terminal of the AC output terminal of the DC / AC converter 120.

[0080] In some embodiments, signal source V c The first output terminal is connected to the positive DC input terminal of the DC / AC converter 120, the second output terminal is connected to the first terminal of the first resistor R1, and the second terminal of the first resistor R1 is connected to the second terminal of the AC output terminal of the DC / AC converter 120.

[0081] In some embodiments, the voltage divider network 112 includes a second resistor R2 and a third resistor R3, which are connected in series between the negative DC input terminal and the first terminal of the AC output terminal of the DC / AC converter 120.

[0082] In another embodiment, the second resistor R2 and the third resistor R3 are connected in series between the positive terminal of the DC input and the second terminal of the AC output of the DC / AC converter 120.

[0083] The sampling module 113 includes a first sampling unit 113a, wherein the first sampling unit 113a is used to sample the voltage across the second resistor R2, obtain the sampled voltage, and provide it to the controller 114;

[0084] Controller 114 controls signal source V c The first excitation signal and the second excitation signal are provided respectively. The first sampling unit 113a obtains the first sampling voltage under the first excitation signal and the second sampling voltage under the second excitation signal respectively. The controller 114 obtains the grounding impedance of the DC input terminal of the inverter 100 according to the difference between the first excitation signal and the second excitation signal and the difference between the first sampling voltage and the second sampling voltage.

[0085] In some embodiments, the resistance value of the first resistor R1 is typically from several MΩ to tens of MΩ.

[0086] In some embodiments, the resistance value of the third resistor R3 is typically of the same level as that of the first resistor R1, ranging from several MΩ to tens of MΩ, while the resistance value of the second resistor R2 used for voltage sampling is typically much smaller than that of the third resistor R3.

[0087] Specifically, signal source V c The controller 114 can output at least one excitation signal relative to the negative terminal of the DC input of the DC / AC converter 120. The corresponding sampling module 113 samples and obtains at least one sampling voltage. The controller 114 obtains the grounding impedance R based on the at least one excitation signal and the sampling voltage under the at least one excitation signal. E1 and R E2 The resistance value or the parallel resistance value of the two, that is, the grounding impedance of the DC input terminal of inverter 100.

[0088] In some embodiments, the controller 114 obtains the grounding impedance R based on at least two different excitation signals and the sampled voltages under different disturbances. E1 and grounding impedance R E2 The parallel resistance value.

[0089] The grounding impedance of the DC input terminal of inverter 100 includes the grounding impedance of the positive DC input terminal and the grounding impedance of the negative DC input terminal, or the parallel value of the grounding impedance of the positive DC input terminal and the grounding impedance of the negative DC input terminal.

[0090] like Figure 2 As shown, the positive and negative DC output terminals of the DC source 200 connected to the DC side of the inverter 100 are respectively connected through the grounding impedance R. E1 and R E2The DC / AC converter 120 is connected to ground, and its AC side is also connected to ground via a neutral wire. Therefore, by connecting the first resistor R1 and the signal source V in series between the DC input and AC output terminals of the DC / AC converter 120... c This forms a closed loop. If only the DC component of this closed loop is considered, then regardless of the grounding configuration of the power grid connected to the AC side of the inverter 100, the AC side of the inverter 100 can be considered equivalent to direct grounding. Considering only the DC component in the system, the aforementioned grounding impedance detection device 110 can be simplified as follows: Figure 3 The DC equivalent circuit model shown is given, where V iso For signal source V c The output excitation signal, excitation signal V iso It is a DC voltage, V pv The DC output voltage of DC source 200, which is also the DC input voltage of the DC input terminal of inverter 100, is a stable value during the detection process. Figure 3 The voltage V1 across the second resistor R2 and the third resistor R3 shown in the figure can be expressed as:

[0091]

[0092] The first sampling unit 113a samples the voltage divider voltage across the second resistor R2 to obtain the sampled voltage V. sam The following relationship must be satisfied:

[0093]

[0094] The steps for grounding impedance detection in this embodiment are as follows:

[0095] S1. First, the controller 114 controls the signal source V. c Output excitation signal V iso1 .

[0096] S2. Signal source V c Output excitation signal V iso1 After stabilization, the first sampling unit 113a samples the voltage divider across the second resistor R2 and obtains the sampling voltage V. sam1 .

[0097] S3. Controller 114 controls signal source V c Output excitation signal V iso2 .

[0098] S4. Signal source V c Output excitation signal V iso2 After stabilization, the first sampling unit 113a samples the voltage divider across the second resistor R2 to obtain the sampling voltage V. sam2 .

[0099] S5. Based on the excitation signal V iso1 V iso2 and sampling voltage V sam1 V sam2 Obtain the grounding impedance R E1 and R E2 The parallel resistance value.

[0100] Among them, the grounding impedance R in step S5 E1 and R E2 The method for obtaining the resistance value is as follows:

[0101] According to signal source V c The two excitation signals provided and the two sampled voltages obtained can be used to derive two equations based on equation (1):

[0102]

[0103] The grounding impedance R can be obtained from the above equation. E1 and R E2 The parallel resistance value.

[0104] Grounding impedance R E1 and R E2 The parallel resistance is:

[0105]

[0106] In some embodiments, the controller 114 can control the signal source V c Output two or more different excitation signals, and sample the voltage divider voltage across the second resistor R2 to obtain the sampled voltage V. sami And based on any two different excitation signals and the sampled voltage V obtained under different excitation signals. sami By obtaining a grounding impedance, the average value of multiple obtained grounding impedances can be calculated to further improve the accuracy of the detected grounding impedance.

[0107] In some embodiments, the sampling module 113 further includes a second sampling unit 113b, connected to the DC input terminal of the inverter 100, for acquiring the DC input voltage and providing it to the controller 114, which controls the signal source V. c Provide at least two different excitation signals, and obtain the grounding impedance of the DC input terminal of inverter 100 based on the at least two different excitation signals and the sampled voltage and DC input voltage under the at least two different excitation signals.

[0108] In some embodiments, when the DC input voltage is unstable, the DC input voltage can be sampled under the corresponding excitation signal, and the grounding impedance R of the DC input terminal of the inverter 100 can be obtained based on at least two different excitation signals and the sampled voltage and DC input voltage under at least two different excitation signals. E1 and R E2 The parallel value.

[0109] Grounding impedance R E1 and R E2 The formula for obtaining the parallel value is as follows:

[0110]

[0111] Furthermore, the magnitude of the grounding impedance can be used to determine whether a grounding fault has occurred in the DC source 200.

[0112] Furthermore, controller 114 will ground impedance R E2 and grounding impedance R E1 The parallel value is compared with a preset threshold to determine whether it is abnormal or whether a DC input terminal grounding fault has occurred. For example, when the parallel value is less than the preset threshold, it is determined that a DC input terminal grounding fault has occurred in the inverter.

[0113] In some embodiments, the controller 114 may respectively set the grounding impedance R E2 Grounding impedance R E1 The grounding impedance R is determined by comparing it with the corresponding preset threshold. E2 and grounding impedance R E1 To determine if there is an abnormality, check if a grounding fault has occurred at the DC input terminal of the inverter.

[0114] In some embodiments, signal source V c The output excitation signal is an AC voltage V containing a fixed frequency. isoac Furthermore, since the aforementioned fixed frequency differs from the power grid frequency, and only the AC voltage at the fixed frequency is considered, the aforementioned grounding impedance detection device 110 can be simplified as follows: Figure 4 The grounding impedance Z can be calculated using the same calculation method from the AC equivalent circuit model shown. E1 and Z E2 The parallel value is determined, and the resistance value is used to determine whether the DC source 200 has a grounding impedance abnormality fault. Among them, the grounding impedance Z E1 and Z E2 The parallel value can be obtained using the following formula.

[0115]

[0116]

[0117] In the formula, V isoac and V sam These are all AC voltage amplitudes corresponding to the excitation signal frequency.

[0118] Furthermore, by controlling the signal source V c Provide different excitation signals V isoac The grounding impedance Z can be obtained. E1 and Z E2 .

[0119] In some embodiments, signal source V c The output excitation signal is a signal consisting of a superposition of a DC signal and a fixed-frequency AC signal. The grounding impedance of the DC input terminal of the inverter 100 can be obtained by referring to the principles of the above embodiments, which will not be repeated here.

[0120] In some embodiments, such as Figure 5 As shown, the voltage divider network 112 is connected to the signal source V. c The output terminal is connected in series with the coupling impedance network 111.

[0121] In some embodiments, such as Figure 6 As shown, the voltage divider network 112 includes a fourth resistor R4, and the coupling impedance network 111 includes a first resistor R1. The fourth resistor R4 is connected in series with the coupling impedance network 111, and a voltage divider voltage is provided across the fourth resistor R4. Signal source V c The second output terminal is connected to the first terminal of the first resistor R1 through the fourth resistor R4, and the second terminal of the first resistor R1 is connected to the second terminal of the AC output terminal.

[0122] In some embodiments, signal source V c The second output terminal is connected to the first terminal of the fourth resistor R4 through the first resistor R1, and the second terminal of the fourth resistor R4 is connected to the second terminal of the AC output terminal.

[0123] The first sampling unit 113a in the sampling module 113 is used to sample the voltage across the fourth resistor R4, obtain the sampled voltage, and provide it to the controller 114. The second sampling unit 113b is used to sample the voltage at the DC input terminal of the inverter 100, obtain the DC input voltage, and provide it to the controller 114.

[0124] Furthermore, the resistance of the fourth resistor R4 is much smaller than the resistance of the first resistor R1.

[0125] Specifically, the DC equivalent circuit model of the grounding impedance detection device is as follows: Figure 7 As shown. The steps for grounding impedance detection in this embodiment are the same as those in the above embodiments. Using the same derivation method, the following equation can be obtained:

[0126]

[0127] Similarly, the grounding impedance R can be obtained from the above equation. E1 and R E2 The parallel value is used to determine whether the DC source 200 has a grounding impedance abnormality fault.

[0128] The structure and connection method of the voltage divider network 112 are not limited to the specific embodiments described above, and can be other types of circuit structures, as long as they can be combined with the signal source V. c Simply perform a grounding impedance test.

[0129] Figure 8 A signal source V, as shown in an embodiment of this application, is illustrated. c A schematic diagram of the circuit structure. (For example...) Figure 8 As shown, signal source V c The input terminal is connected, for example, to the DC input terminal of inverter 100, and the signal source V c This is a switching circuit, including the switching transistor S1 and the fifth resistor R. x Switch S1 and fifth resistor R x The switching transistor S1 and the fifth resistor R are connected in series at the DC input terminal of inverter 100. x The connection point is connected to the first end of the first resistor R1. By controlling the conduction and disconnection of the switch transistor S1, the signal source V is controlled. c The output excitation signal is in 0 and V pv Switching between these states. Specifically, when switch S1 is on, the output excitation signal is 0V; when switch S1 is off, due to the fifth resistor R... x Much smaller than the first resistor R1, the output excitation signal is V. pv The circuit has a simple structure and low cost.

[0130] To increase the difference between different excitation signals Figure 9 A signal source V, as shown in an embodiment of this application, is illustrated. c A schematic diagram of the circuit structure. (For example...) Figure 9 As shown, signal source V c For a boost converter, the signal source V c The input terminal is connected, for example, to the DC input terminal of inverter 100, according to the DC input voltage V. pv Generate an excitation signal, and the controller 114 controls the signal source V. c The duty cycle of the switching transistor enables the output of various different excitation signals, and the range of the output excitation signals can be flexibly adjusted.

[0131] In some embodiments, signal source V c It includes a boost converter and the switching circuit connected in series.

[0132] In some embodiments, signal source V c It can be used for other forms of DC-DC voltage conversion circuits, such as flyback topologies.

[0133] In some embodiments, signal source V c It can be a rectifier circuit, in which case its input terminal receives AC power, such as power drawn from the power grid.

[0134] In some embodiments, signal source V c It can be part of a DC / AC converter 120. For example... Figure 10 and Figure 11 As shown, the DC / AC converter 120 includes an inverter unit 121, a transformer 122, and a frequency converter 123. The inverter unit 121 is used for inversion, the transformer 122 is connected to the inverter unit 121 and is used for voltage boosting and electrical isolation, and the frequency converter 123 is connected to the transformer 122 and is used for AC-AC conversion.

[0135] Specifically, the inverter unit 121 is a full-bridge circuit, including series-connected switches Q1H and Q1L, and series-connected switches Q2H and Q2L. Switches Q1H and Q1L constitute the signal source Vc. The midpoint of the connection between switches Q1H and Q1L provides the excitation signal, which is a DC input voltage or 0.

[0136] In some embodiments, switching transistors Q2H and Q2L constitute the signal source Vc, and the midpoint of the connection between switching transistors Q2H and Q2L provides the excitation signal, which is a DC input voltage or 0.

[0137] In some embodiments, the inverter unit 121 is a half-bridge circuit, in which case the half-bridge circuit is the signal source Vc.

[0138] In some embodiments, such as Figure 12 As shown, the first sampling unit 113a includes a filtering circuit 115 and a sampling circuit 116. The filtering circuit 115 is connected to the voltage divider network 112 and the sampling circuit 116 respectively. The filtering circuit 115 is used to filter out voltage components other than the frequency of the excitation signal in the sampled voltage.

[0139] In some embodiments, the first sampling unit 113a is an ADC sampling unit, and the controller 114 receives the sampled voltage in digital form. Accordingly, the controller 114 includes a filtering unit for filtering out voltage components other than the frequency of the excitation signal in the sampled voltage.

[0140] Furthermore, such as Figure 13As shown, this application also provides a grounding impedance detection method for detecting the grounding impedance of the DC input terminal of inverter 100. The method includes the following steps:

[0141] Step S210: Couple at least one excitation signal between the DC input terminal and the AC output terminal of the inverter 100;

[0142] Step S220: Sample the voltage divider between the DC input terminal and the AC output terminal of the inverter 100 to obtain the sampled voltage;

[0143] Step S230: Obtain the grounding impedance of the DC input terminal of the inverter 100 based on at least one excitation signal and the corresponding sampling voltage under at least one excitation signal.

[0144] In some embodiments, the method further includes the following steps:

[0145] The first excitation signal and the second excitation signal are respectively coupled between the DC input terminal and the AC output terminal of the inverter 100;

[0146] The first sampling voltage under the first excitation signal and the second sampling voltage under the second excitation signal are obtained respectively, and the grounding impedance of the DC input terminal of the inverter 100 is obtained according to the difference between the first excitation signal and the second excitation signal and the difference between the first sampling voltage and the second sampling voltage.

[0147] In some embodiments, the method further includes the following steps:

[0148] At least two different excitation signals are coupled between the DC input and AC output of the inverter 100;

[0149] Obtain the DC input voltage and sampling voltage of the inverter 100 DC input terminal corresponding to at least two different excitation signals, and obtain the grounding impedance of the inverter 100 DC input terminal based on at least two different excitation signals and the sampling voltage and DC input voltage under at least two different excitation signals.

[0150] In some embodiments, the method further includes the following steps:

[0151] The grounding impedance is compared with a preset threshold to determine whether the grounding impedance is abnormal.

[0152] This application also provides an inverter 100, including the aforementioned grounding impedance detection device 110 and DC / AC converter 120.

[0153] This application sets a signal source V between the DC input terminal and the AC output terminal of the inverter 100. cA high-impedance loop is constructed using a coupling impedance network 111. An excitation signal is introduced into this loop, and the grounding impedance of the inverter 100 is obtained based on the excitation signal and the sampling voltage under the excitation signal. Thus, the grounding impedance of the DC input terminal of the inverter 100 is detected without a grounding wire.

[0154] The grounding impedance detection device 110, the grounding impedance detection method, and the inverter 100 of this application correspond to each other. The technical features and beneficial effects described in the embodiments of the grounding impedance detection device 110 are also applicable to the embodiments of the grounding impedance detection method and the inverter 100.

[0155] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0156] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A grounding impedance detection device, characterized in that, The device includes a signal source, a coupling impedance network, a voltage divider network, a sampling module, and a controller; The signal source is used to provide excitation signals; The coupling impedance network is connected to the signal source and is used to couple the excitation signal between the DC input terminal and the AC output terminal of the inverter, wherein the AC output terminal of the inverter is connected to the power grid; The voltage divider network is used to divide the voltage between the DC input terminal and the AC output terminal to provide a divided voltage. The sampling module is connected to the voltage divider network and is used to sample the voltage divider voltage to obtain the sampled voltage; The controller is connected to the signal source and the sampling module respectively, and is used to control the signal source to provide at least one excitation signal, and to obtain the grounding impedance of the DC input terminal of the inverter based on the at least one excitation signal and the sampling voltage corresponding to the at least one excitation signal; One output terminal of the signal source is connected to one of the DC input terminals, and the other output terminal is connected to one of the AC output terminals through the coupling impedance network.

2. The grounding impedance detection device according to claim 1, characterized in that, The controller is further configured to control the signal source to provide a first excitation signal and a second excitation signal respectively. The sampling module is configured to acquire a first sampling voltage under the first excitation signal and a second sampling voltage under the second excitation signal respectively. The controller is further configured to acquire the grounding impedance of the DC input terminal of the inverter based on the difference between the first excitation signal and the second excitation signal and the difference between the first sampling voltage and the second sampling voltage.

3. The grounding impedance detection device according to claim 1, characterized in that, The signal source includes a DC voltage conversion circuit or a rectifier circuit.

4. The grounding impedance detection device according to claim 1, characterized in that, The signal source includes a switching circuit, which includes at least one switch, and outputs different excitation signals by controlling the on state of the at least one switch.

5. The grounding impedance detection device according to claim 1, characterized in that, The inverter includes a full-bridge circuit or a half-bridge circuit connected to the DC input terminal, the signal source is a part of the full-bridge circuit or the half-bridge circuit, and the excitation signal is the DC input voltage or 0 at the DC input terminal.

6. The grounding impedance detection device according to claim 1, characterized in that, The voltage divider network is connected between one of the DC input terminals and one of the AC output terminals of the inverter.

7. The grounding impedance detection device according to claim 1, characterized in that, The voltage divider network is connected in series with the coupling impedance network.

8. The grounding impedance detection device according to claim 1, characterized in that, The sampling module includes a first sampling unit, which is connected to the voltage divider network and is used to acquire the sampling voltage.

9. The grounding impedance detection device according to claim 8, characterized in that, The first sampling unit includes a filtering circuit and a sampling circuit. The filtering circuit is connected to the voltage divider network and the sampling circuit respectively, and is used to filter out voltage components other than the frequency of the excitation signal in the sampling voltage.

10. The grounding impedance detection device according to claim 8, characterized in that, The controller includes a filtering unit for filtering out voltage components in the sampled voltage other than the frequency of the excitation signal.

11. The grounding impedance detection device according to claim 8, characterized in that, The sampling module further includes a second sampling unit connected to the DC input terminal of the inverter, used to acquire the DC input voltage and provide it to the controller. The controller is used to control the signal source to provide at least two different excitation signals, and to acquire the grounding impedance of the DC input terminal of the inverter based on the at least two different excitation signals and the sampling voltage and the DC input voltage under the at least two different excitation signals.

12. The grounding impedance detection device according to claim 1, characterized in that, The excitation signal is a DC signal, an AC signal, or a signal resulting from the superposition of a DC signal and an AC signal.

13. The grounding impedance detection device according to claim 1, characterized in that, The controller is used to compare the grounding impedance with a preset threshold to determine whether the grounding impedance is abnormal.

14. A grounding impedance detection method, applied to the grounding impedance detection device as described in any one of claims 1 to 13, for detecting the grounding impedance of the DC input terminal of an inverter, characterized in that, The method includes the following steps: At least one excitation signal is coupled between the DC input terminal and the AC output terminal of the inverter; The voltage divider voltage between the DC input terminal and the AC output terminal of the inverter is sampled to obtain the sampled voltage. The grounding impedance of the inverter's DC input terminal is obtained based on the at least one excitation signal and the corresponding sampling voltage under the at least one excitation signal.

15. The method according to claim 14, characterized in that, The method further includes the following steps: The first excitation signal and the second excitation signal are respectively coupled between the DC input terminal and the AC output terminal of the inverter; The first sampled voltage under the first excitation signal and the second sampled voltage under the second excitation signal are obtained respectively, and the grounding impedance of the DC input terminal of the inverter is obtained based on the difference between the first excitation signal and the second excitation signal and the difference between the first sampled voltage and the second sampled voltage.

16. The method according to claim 14, characterized in that, The method further includes the following steps: At least two different excitation signals are coupled between the DC input and AC output of the inverter; Obtain the DC input voltage and the sampling voltage of the inverter DC input terminal corresponding to the at least two different excitation signals, and obtain the grounding impedance of the inverter DC input terminal based on the at least two different excitation signals, the sampling voltage and the DC input voltage under the at least two different excitation signals.

17. The method according to claim 16, characterized in that, The method further includes the following steps: The grounding impedance is compared with a preset threshold to determine whether the grounding impedance is abnormal.

18. An inverter, characterized in that, Includes a grounding impedance detection device and a DC / AC converter as described in any one of claims 1 to 13, wherein the DC / AC converter is connected between the DC input terminal and the AC output terminal of the inverter for converting DC power into AC power.

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