Converter and method for detecting insulation impedance

Abstract

This application discloses a converter and a method for detecting insulation impedance. The converter includes a controller, a detection resistor network, and a power conversion circuit. The power conversion circuit includes a first switch tube and a second switch tube. The first end of the first switch tube is connected to the positive pole of a DC power source, the second end of the first switch tube is connected to the first end of the second switch tube, and the second end of the second switch tube is connected to the negative pole of the DC power source, and the second end of the first switch tube is grounded via the detection resistor network. The controller obtains the insulation impedance of the converter based on the voltage between the positive and negative poles of the DC power source and the voltage to ground of the negative pole of the DC power source before and after the first switch tube or the second switch tube is turned on. By controlling the on / off state, the magnitude of the voltage between the positive and negative poles of the converter or the voltage to ground of the negative pole of the DC power source is changed, and the magnitude is combined with the impedance of the detection resistor network to obtain the insulation impedance of the converter. This converter is low cost because it only requires the addition of a detection resistor network and uses the switch tubes of the converter.

Description

[Technical Field]

[0001] This application claims priority to a Chinese patent application filed with the State Intellectual Property Office of the People's Republic of China on March 8, 2023, bearing application number 202310239127.8 and entitled "Converter and method for detecting insulation impedance," the entire contents of which are incorporated herein by reference.

[0002] The present application relates to the technical field of power electronics, and in particular to a converter and a method for detecting insulation impedance. [Background technology]

[0003] Clean energy applications, such as solar power generation and electrochemical energy storage systems, are becoming increasingly widespread. However, new energy generation systems are generally installed outdoors and are subject to weather factors such as dust, rain, snow, and fog, which can change the earth insulation impedance of the downstream converter (e.g., inverter). If this insulation impedance is too low, leakage current may occur, creating a risk of electric shock. Therefore, this insulation impedance must be detected in real time.

[0004] The conventional resistive bridge method requires the addition of a resistor and its corresponding switch circuit on the ground side, which reduces the reliability of the equipment and increases the cost. Summary of the Invention [Problem to be solved by the invention]

[0005] In view of this, the present application provides a converter and an impedance detection method that can accurately detect the insulation impedance of a converter, are highly reliable, and are low cost. [Means for solving the problem]

[0006] The present application provides a converter, including a controller, a sense resistor network, and a power conversion circuit; The power conversion circuit includes a first switch tube and a second switch tube; The first end of the first switch tube is connected to the positive pole of the DC power supply, the second end of the first switch tube is connected to the first end of the second switch tube, the second end of the second switch tube is connected to the negative pole of the DC power supply, and the second end of the first switch tube is grounded through a detection resistor network; The controller obtains the insulation impedance of the converter based on the voltage between the positive and negative poles of the DC power source and the negative pole-to-ground voltage of the DC power source before and after the first switch tube or the second switch tube is turned on.

[0007] Preferably, the sense resistor network includes a first resistor; The second end of the first switch tube is grounded via a first resistor.

[0008] Preferably, the detection resistor network further includes a second resistor and a third resistor; The two ends of the second resistor are respectively connected to the positive pole of the DC power source and the second end of the first switch tube; The two ends of the third resistor are respectively connected to the negative pole of the DC power source and the second end of the first switch tube.

[0009] Preferably, the device further includes an inductor; The second end of the first switch tube is grounded via a series connection of an inductor and a first resistor.

[0010] Preferably, the controller obtains the insulation impedance of the converter based on the voltage between the positive and negative poles of the DC power source and the negative pole-to-ground voltage of the DC power source before the first switch tube is turned on, and the negative pole-to-ground voltage of the DC power source after the first switch tube is turned on.

[0011] Preferably, the controller obtains the insulation impedance of the converter based on the voltage between the positive and negative poles of the DC power source and the negative pole-to-ground voltage of the DC power source before the second switch tube is turned on, and the negative pole-to-ground voltage of the DC power source after the second switch tube is turned on.

[0012] Preferably, the converter is an isolated DC-DC converter or an isolated DC-AC converter; The first and second switch tubes are two switch tubes of the first bridge arm of the primary full bridge of the isolated DC-DC converter or isolated DC-AC converter, and the primary full bridge of the isolated DC-DC converter includes a first bridge arm and a second bridge arm.

[0013] Preferably, the converter is a T-type three-level inverter; The T-type three-level inverter further includes an inductor; The second end of the first switch tube is connected to ground through a series connected inductor and sense resistor network.

[0014] Preferably, the converter includes a three-level Boost circuit and a neutral-point clamped inverter circuit, and the neutral-point clamped inverter circuit includes a first switch module, a second switch module, a third switch module, and a fourth switch module connected in series; The first switch tube and the second switch tube are respectively the first switch module and the second switch module in the three-level Boost circuit; Or, The first switch tube and the second switch tube are the second switch module and the third switch module of the neutral point clamped inverter circuit.

[0015] Preferably, the converter includes a three-level Boost circuit and an active neutral-point clamped inverter circuit; The first and second switch tubes are the first and second switch tubes in a three-level Boost circuit.

[0016] Preferably, the converter is a bidirectional DC-DC buck-boost converter; The bidirectional DC-DC buck-boost converter includes a first switch module, a second switch module, a third switch module, and a fourth switch module connected in series in this order; The first switch tube and the second switch tube are a first switch module and a second switch module, respectively; The common end of the first switch module and the second switch module is connected to ground via a sense resistor network.

[0017] Preferably, the converter is a heric converter; The heric converter includes a first bridge arm, a second bridge arm, a fifth switch module, a sixth switch module and an LC filter, and the midpoint of the first bridge arm is grounded through a detection resistor network; The fifth switch module and the sixth switch module are connected in series and then connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm; The first and second ends of the LC filter are connected to the midpoint of the first bridge arm and the midpoint of the second bridge arm, respectively, and the first and second ends of the LC filter are connected to both ends of the capacitor via the first inductor and the second inductor, respectively.

[0018] Preferably, the converter is a heric converter; The heric converter includes a first bridge arm, a second bridge arm, a fifth switch module, a sixth switch module and an LC filter; The fifth switch module and the sixth switch module are connected in series and then connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm; The first and second ends of the LC filter are respectively connected to the midpoint of the first bridge arm and the midpoint of the second bridge arm, and the first and second ends of the LC filter are respectively connected to both ends of the capacitor via the first inductor and the second inductor; a first end of the LC filter is grounded via a first inductor and a first resistor connected in series; The first switch tube and the second switch tube are two switch tubes of the first bridge arm.

[0019] Preferably, the device further comprises a switch; The sense resistor network is connected to ground through a switch The controller further controls the switch to be on when detecting an isolation impedance, and controls the switch to be off in the opposite case.

[0020] Preferably, the DC power source is a solar photovoltaic array or a battery.

[0021] The present application further provides a method for detecting insulation impedance of a converter, the converter including a detection resistor network and a power conversion circuit, the power conversion circuit including a first switch tube and a second switch tube, a first end of the first switch tube is connected to a positive pole of a DC power source, a second end of the first switch tube is connected to a first end of a second switch tube, and a second end of the second switch tube is connected to a negative pole of the DC power source, and the second end of the first switch tube is grounded through the detection resistor network; The method comprises: When both the first switch tube and the second switch tube are turned off, acquiring a voltage between the positive electrode and the negative electrode of the DC power source and a voltage of the negative electrode of the DC power source to ground; controlling the first switch tube or the second switch tube to be turned on; and obtaining the insulation impedance of the converter based on the voltage between the positive and negative poles of the DC power source and the negative pole-to-ground voltage of the DC power source before and after the first switch tube or the second switch tube is turned on.

[0022] Preferably, the detection resistor network includes a first resistor, and the second end of the first switch tube is grounded via the first resistor.

[0023] Preferably, the detection resistor network further includes a second resistor and a third resistor; The two ends of the second resistor are respectively connected to the positive pole of the DC power source and the second end of the first switch tube; The two ends of the third resistor are respectively connected to the negative pole of the DC power source and the second end of the first switch tube.

[0024] Preferably, the step of obtaining the insulation impedance of the converter according to the voltage between the positive pole and the negative pole of the DC power source and the negative pole to ground voltage of the DC power source before and after the first switch tube or the second switch tube is turned on specifically includes: The method includes a step of obtaining the insulation impedance of the converter based on the voltage between the positive and negative poles of the DC power source and the negative pole-to-ground voltage of the DC power source before the first switch tube is turned on, and the voltage between the positive and negative poles of the DC power source after the first switch tube is turned on.

[0025] Preferably, the step of obtaining the insulation impedance of the converter according to the voltage between the positive pole and the negative pole of the DC power source and the negative pole to ground voltage of the DC power source before and after the first switch tube or the second switch tube is turned on specifically includes: The method includes a step of obtaining the insulation impedance of the converter based on the voltage between the positive and negative poles of the DC power source and the negative pole-to-ground voltage of the DC power source before the second switch tube is turned on, and the negative pole-to-ground voltage of the DC power source after the second switch tube is turned on. [Effects of the Invention]

[0026] As such, the present application has the following beneficial effects: The converter provided by the present application only requires the addition of a detection resistor network to the converter, and the converter topology already includes a first switch tube and a second switch tube connected in series, with the second end of the first switch tube grounded via the detection resistor network. By controlling the on / off state of the first switch tube or the second switch tube, the magnitude of the DC voltage between the positive and negative poles of the converter or the DC negative pole to ground voltage can be changed, and the converter's insulation impedance can be obtained in combination with the impedance of the detection resistor network. The converter's insulation impedance detection structure is simple, requiring only the addition of a detection resistor network and using the switch tube of the converter's power conversion circuit itself, making it low-cost and applicable to various converter types. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a schematic diagram of a converter according to an embodiment of the present application; [Figure 2] FIG. 10 is a schematic diagram of another sensing resistor network according to an embodiment of the present application. [Figure 3] FIG. 2 is a grounding schematic diagram of a first resistor according to an embodiment of the present application. [Figure 4] FIG. 10 is a schematic diagram of another sensing resistor network according to an embodiment of the present application. [Figure 5] FIG. 3 is an equivalent circuit diagram corresponding to when both of the two switches in FIG. 2 are turned off. [Figure 6] Figure 6A is an equivalent circuit diagram corresponding to when S1 in Figure 2 is turned on and S2 in Figure 2 is turned off, and Figure 6B is an equivalent circuit diagram corresponding to when S1 in Figure 2 is turned off and S2 in Figure 2 is turned on. [Figure 7] 4 is a flowchart of a converter according to an embodiment of the present application obtaining isolation impedance; [Figure 8] FIG. 8A is a schematic diagram of an isolated DC-DC converter according to an embodiment of the present application, and FIG. 8B is a schematic diagram of another isolated DC-DC converter according to an embodiment of the present application. [Figure 9] 1 is a schematic diagram of an isolated DC / AC converter according to an embodiment of the present application; [Figure 10] 1 is a schematic diagram of a T-type three-level converter according to an embodiment of the present application; [Figure 11] FIG. 1 is a schematic diagram of a three-level Boost+NPC converter according to an embodiment of the present application. [Figure 12] FIG. 1 is a schematic diagram of another three-level Boost+NPC converter according to an embodiment of the present application. [Figure 13] FIG. 1 is a schematic diagram of a three-level Boost+ANPC converter according to an embodiment of the present application. [Figure 14] 1 is a schematic diagram of a bidirectional DC-DC buck-boost converter according to an embodiment of the present application; FIG. [Figure 15] FIG. 1 is a schematic diagram of a heric converter according to an embodiment of the present application. [Figure 16] FIG. 1 is a schematic diagram of another heric converter according to an embodiment of the present application. [Figure 17] FIG. 10 is a schematic diagram of yet another heric converter according to an embodiment of the present application. [Figure 18] 2 is a flowchart of a method for detecting the insulation impedance of a converter according to an embodiment of the present application; DETAILED DESCRIPTION OF THE INVENTION

[0028] In order to make the above objects, features and advantages of the present application more comprehensible, the following examples of the present application will be described in more detail in combination with drawings and specific embodiments.

[0029] The converters provided by the embodiments of the present application are not particularly limited in application scenario, and may be used for solar power generation, energy storage, or other power electronics fields. The embodiments of the present application also do not limit the specific type of converter, and may be, for example, an isolated converter or a non-isolated converter. If the converter is an isolated converter, it may be an isolated DC-DC converter or an isolated DC-AC converter. Here, the insulation impedance obtained by the converters provided by the embodiments of the present application is the insulation impedance to ground on the DC side of the converter.

[0030] For ease of understanding, a converter applied to a solar power generation system will be introduced below as an example.

[0031] Please refer to FIG. 1, which is a schematic diagram of a converter provided by an embodiment of the present application.

[0032] The converter provided by the embodiment of the present application includes a controller (not shown), a detection resistor network 100, and a power conversion circuit, the power conversion circuit including a first switch tube (switching element) S1 and a second switch tube S2; A first end of the first switch tube S1 is connected to the positive pole PV+ of the DC power source, a second end of the first switch tube S1 is connected to the first end of the second switch tube S2, a second end of the second switch tube S2 is connected to the negative pole PV- of the DC power source, and a second end of the first switch tube S1 is grounded via a detection resistor network 100; In this embodiment, the DC power source is a photovoltaic power generation array as an example.

[0033] The controller obtains the insulation impedance of the converter based on the impedance of the detection resistor network 100, the voltage between the positive and negative poles of the DC power supply and the voltage of the negative pole of the DC power supply to ground before and after the first switch tube or the second switch tube is turned on.

[0034] The embodiments of the present application do not specifically limit the number of resistors within the detection resistor network 100, and may be, for example, one or more, and if more than one, may be, for example, three.

[0035] The following describes, with reference to the accompanying drawings, the situations in which the detection resistor network 100 includes one resistor and three resistors.

[0036] Please refer to FIG. 2, which is a schematic diagram of a sensing resistor network provided by an embodiment of the present application.

[0037] In this embodiment, it is taken as an example that the detection resistor network includes a first resistor R0. The second end of the first switch tube S1 is grounded via a first resistor R0.

[0038] Please refer to Figure 3, which is a schematic diagram of a detection resistor network provided by an embodiment of the present application. S1 and S2 in Figure 2 can be more switch tubes connected in series. Figure 1 shows only a part of the converter circuit.

[0039] The source of S1 is connected to the drain of S2. Rm is the specific impedance of the protective earth terminal PE (housing) of the converter's positive input terminal, Rn is the specific impedance of the protective earth terminal PE (housing) of the converter's negative terminal, and R0 has a known resistance and is connected in series between PE and the source of S1.

[0040] In addition, the converter may further include a switch K. Specifically, refer to FIG. 3, which is a schematic diagram of the grounding of the sensing resistor network provided by the embodiment of the present application.

[0041] One end of the first resistor R0 is connected to the source of S1 via the switch K, and the other end of the first resistor R0 is grounded; The controller further controls the switch K to be turned on when detecting the isolation impedance, and controls the switch K to be turned off in the opposite case.

[0042] Here, the converter provided in the embodiments of the present application uses the first switch tube and the second switch tube already included in the power conversion circuit, and only adds a detection resistor network, which is low cost and simple in structure. By controlling the on / off state of the first switch tube or the second switch tube, the magnitude of the DC voltage between the positive and negative poles of the converter or the DC negative pole to ground voltage can be changed, and further, in combination with the resistance value of the first resistor, the insulation impedance of the converter can be obtained.

[0043] The first resistor is connected to the positive pole of the DC power supply via the first switch tube and to the negative pole of the DC power supply via the second switch tube. Therefore, when the on / off state of the first switch tube or the second switch tube changes, the positive half-bus common-mode voltage or the negative half-bus common-mode voltage is disturbed. That is, the range of disturbed voltages is wide, and the detection of insulation impedance can be more sensitive.

[0044] Please refer to FIG. 4, which is a schematic diagram of another sensing resistor network provided by an embodiment of the present application.

[0045] The converter provided by this embodiment will be further introduced as an example applied to the photovoltaic power generation field.

[0046] The sense resistor network further includes a second resistor R1 and a third resistor R2; It should be noted that an advantage of the multiple resistors of FIG. 4 over the single resistor of FIG. 3 is that it facilitates voltage withstand testing.

[0047] The two ends of the second resistor R1 are respectively connected to the positive pole PV+ of the DC power source and the second end of the first switch tube S1; The two ends of the third resistor R2 are respectively connected to the negative pole PV- of the DC power source and the second end of the first switch tube S1.

[0048] Similar to the switch K in FIG. 3, the corresponding sense resistor network in FIG. 4 may correspond to the switch K, i.e., one end of the first resistor R0 is connected to the source of S1 through the switch K, and the other end of the first resistor R0 is connected to the protective earth terminal PE.

[0049] FIG. 2 shows a direct grounding of the first resistor, and in another implementation, the common end of the two switch tubes is grounded via an inductor and the first resistor in the filter circuit.

[0050] The principle of detecting insulation impedance provided by the embodiments of the present application will be explained in detail below in conjunction with the drawings.

[0051] The embodiments of the present application do not specifically limit whether the voltage is disturbed by turning on the first switch tube or by turning on the second switch tube, and the voltage may be disturbed by turning on the first switch tube or the second switch tube. Hereinafter, the first switch tube being turned on will be taken as an example.

[0052] Plan 1: Please refer to FIG. 5, which is an equivalent circuit diagram corresponding to when S1 and S2 in FIG. 2 are both turned off. In Figure 2, the source of S1 is connected to the drain of S2, the drain of S1 is connected to one end of the Rm resistor, PV+, the other end of Rm is connected to the housing PE and one end of Rn, the other end of Rn is connected to PV-, one end of R0 is connected to the housing PE and the other end is connected to the source of S1, Rm is the equivalent impedance between PV+ and PE, and Rn is the equivalent impedance between PV- and PE. The voltage between PV+ and PV- is denoted by V1, and the PV-to-ground voltage is denoted by V-.

[0053] Please refer to FIG. 6A, which is the equivalent circuit diagram corresponding to when S1 of FIG. 2 is turned on and S2 is turned off.

[0054] After S1 is turned on and S2 is turned off, R0 and Rn are connected in parallel, and the voltage between PV1+ and PV- is V1 ’ and the voltage between PV- and PE is V- ’ and Before and after S1 is turned on, the voltage between PV+ and PV- is set constant, i.e., V1 = V1 ’ is.

[0055] Node current equations are created for FIGS. 5 and 6A, respectively, and the following formulas (1) and (2) are obtained. JPEG2026501414000002.jpg12170 JPEG2026501414000003.jpg13170By subtracting and transforming equation (1) using equation (2), we obtain equation (3). JPEG2026501414000004.jpg15150 Further optimization shows that the impedance of the machine with respect to the PE is Riso, By substituting JPEG2026501414000005.jpg1130 into equation (3), the following equation can be solved. JPEG2026501414000006.jpg1955

[0056] Plan 2: In this solution, the second switch tube S2 is controlled to be turned on as an example. For the equivalent diagram before both switch tubes are turned off, please continue to refer to FIG. 5, and for the diagram after S2 is turned on, please refer to FIG. 6B.

[0057] After S1 is turned off and S2 is turned on, the equivalent circuit of FIG. 2 is shown in FIG. 6B, where R0 and Rn are connected in parallel, and the impedance between PV1+ and PV- is V1', and the voltage between PV- and PE is V-'; Before and after the switch tube is turned on, the voltage between PV+ and PV- is set constant, i.e., V1=V1'. The node current equations are created for Figures 5 and 6B, respectively, and the following equations (1) and (2) are obtained. JPEG2026501414000007.jpg13170 JPEG2026501414000008.jpg13170By subtracting and transforming equation (4) using equation (5), we obtain the following equation (6). JPEG2026501414000009.jpg14170 Further optimization results in an insulation impedance of Riso, By substituting JPEG2026501414000010.jpg930 into equation (6), the following equation can be solved. JPEG2026501414000011.jpg1452

[0058] Here, for the detection circuit network shown in FIG. 4, the above method may be used to control the state of S1 or S2 and establish the corresponding formula to obtain the insulation impedance.

[0059] Here, after obtaining the insulation impedance of the converter, it is determined whether the converter has an insulation failure to the ground based on the magnitude of the insulation impedance. For example, the insulation impedance can be compared with a preset value. If the insulation impedance is smaller than the preset value, it indicates that an insulation failure has occurred, and the number of insulation abnormalities is recorded. If the number of insulation abnormalities exceeds the preset number, an alarm is issued and the converter is stopped.

[0060] The specific flow of how the converter according to the embodiment of the present application obtains the insulation impedance will be described in detail below, as shown in Figure 7. S1: Start. S2: Switch K (including switch K in FIG. 2) is turned on and delayed for time T1, and S1 and S2 are turned off. S3: Turn on S1 or S2, turn off the other switch and delay for time T3, detect the voltage between PV+ and PV-, the voltage between PV- and PE, and calculate the insulation impedance for the system. S4: Determine whether the insulation impedance exceeds a preset value. S5: If S4 is not true, the following startup flow is executed. S6: If S4 is true, record the number of insulation abnormalities. S7: Determine whether the number of insulation abnormalities exceeds a preset number. S8: If S7 is satisfied, it is determined that the insulation is abnormal, and the system is stopped and a fault alarm is issued.

[0061] Below, we will introduce several specific converter combinations to obtain the insulation impedance.

[0062] Please refer to FIG. 8A, which is a schematic diagram of an isolated DC-DC converter provided by an embodiment of the present application.

[0063] In this embodiment, an LLC resonant isolated DC-DC converter is taken as an example, and the application scenario is not specifically limited. For example, the input is the high voltage side, HVBUS+ is the high voltage side positive pole, HVBUS- is the high voltage side negative pole, the output is the low voltage side, LVBAT+ is the low voltage side positive pole, LVBAT- is the low voltage side negative pole, and the DC power supply connected to the high voltage side may be a battery.

[0064] The primary high-voltage full bridge includes two bridge arms connected in parallel, the left bridge arm including switch tubes S1 and S3 connected in series, and the right bridge arm including switch tubes S2 and S4 connected in series. A first end of the primary side of transformer T is connected to the midpoint of the left bridge arm (i.e., the common end of S1 and S3) via inductor L2, and a second end of the primary side of transformer T is connected to the midpoint of the right bridge arm (i.e., the common end of S2 and S4) via capacitor C.

[0065] The first resistor R0 is directly connected between the midpoint of the left bridge arm of the primary high-voltage full bridge (i.e., the common end of S1 and S3) and the protective earth terminal PE. By adjusting the on / off (conduction / cutoff) of the upper switch tube S1 and the lower switch tube S3, R0 can be flexibly incorporated into Rm or Rn, and the earth insulation impedance of the converter DC side can be obtained.

[0066] In FIG. 8A, the first resistor is connected between the common end of the two switch tubes and ground, but the first resistor may also be connected between the inductor and ground, which will be described in detail below in conjunction with the accompanying drawings.

[0067] Please refer to FIG. 8B, which is a schematic diagram of another isolated DC-DC converter provided by an embodiment of the present application.

[0068] The first resistor R0 is connected between the inductor L2 of the primary-side LLC resonant network and the protective earth terminal PE. By adjusting the on / off of the upper switch tube S1 and the lower switch tube S3 (similarly by adjusting S2 and S4), R0 can be flexibly incorporated into Rm or Rn, and the insulation impedance can be obtained using the insulation impedance obtaining method introduced above.

[0069] Please refer to FIG. 9, which is a schematic diagram of an isolated DC / AC converter provided by an embodiment of the present application.

[0070] The inverter shown in FIG. 9 is a micro-inverter, with a primary side being a full-bridge converter and a secondary side being an AC / AC converter. The primary-side full-bridge converter includes two bridge arms connected in parallel, the left bridge arm including switch tubes S1 and S3 connected in series, and the right bridge arm including switch tubes S2 and S4 connected in series.

[0071] The embodiments of the present application do not specifically limit the number of circuits on the primary side of the microinverter, and may include one circuit or multiple circuits. For example, if there are multiple circuits, each circuit may be connected to a corresponding photovoltaic power generation array. In Figure 9, an example is shown in which the primary side includes a full-bridge converter with multiple circuits, corresponding to multiple transformers, and the secondary output terminals may be connected in parallel.

[0072] The first resistor R0 is directly connected between the midpoint of the left bridge arm of the primary full bridge (the common end of S1 and S3) and the protective earth terminal PE. By adjusting the on / off state of the upper switch tube S1 or the lower switch tube S3, R0 can be flexibly incorporated into Rm or Rn. Furthermore, the insulation impedance can be obtained using the insulation impedance obtaining method introduced above.

[0073] Please refer to FIG. 10, which is a schematic diagram of a T-type three-level converter provided by an embodiment of the present application.

[0074] In this embodiment, the converter is an inverter as an example.

[0075] 10, only one phase of the T-type three-level inverter is shown. The output terminal of the T-type three-level converter is connected to an LC filter circuit, which includes an inductor L and a capacitor C.

[0076] The first resistor R0 is connected between the inductor L and ground in the filter circuit of the T-type three-level inverter. The horizontal switch tube of the T-type three-level inverter includes T2 and T3, and the vertical switch tube includes T1 and T4. T1 and T4 are respectively S1 and S2 in Figure 2. By turning on T1 or T4, the corresponding formula can be derived to obtain the insulation impedance.

[0077] Please refer to FIG. 11, which is a schematic diagram of a three-level Boost+NPC converter provided by an embodiment of the present application.

[0078] The converter in this embodiment may be introduced by taking an inverter as an example.

[0079] In the three-level floating BOOST+NPC inverter topology, R0 is directly connected between the midpoint of the upper switch tube T1 and the lower switch tube T2 (i.e., the source of the T1 switch tube) and the protective earth terminal PE, where T1 and T2 are designated as S1 and S2 in Figure 2. By controlling the on / off of the upper switch tube T1 or the lower switch tube T2, R0 can be flexibly incorporated into Rm or Rn, and the isolation impedance can be obtained using the isolation impedance obtaining method introduced above.

[0080] In addition, in the converter provided by the embodiment of the present application, a first resistor R0 may be connected between the inductor L and the protective earth terminal PE, as shown in FIG. 12. Refer to FIG. 12, which is a schematic diagram of another three-level Boost+NPC converter provided by the embodiment of the present application.

[0081] The on / off of S1, S2, S3, and S4 are controlled individually, and the insulation impedance is obtained using the insulation impedance acquisition method introduced above.

[0082] Please refer to FIG. 13, which is a schematic diagram of a three-level Boost+ANPC converter provided by an embodiment of the present application.

[0083] The differences between Figure 13 and Figure 11 are as follows: the clamping elements in Figure 11 are diodes, i.e., D1 and S2, while the clamping elements in Figure 13 are controllable switch tubes, i.e., S5 and S6. For the converter in Figure 13, the installation method of its first resistor can be referred to Figures 11 and 12 and will not be repeated here.

[0084] Please refer to FIG. 14, which is a schematic diagram of a bidirectional DC-DC buck-boost converter provided by an embodiment of the present application.

[0085] The bidirectional DC-DC buck-boost converter provided in this embodiment includes a first switch module S1, a second switch module S2, a third switch module S3, and a fourth switch module S4 connected in series. In this embodiment, each switch module includes one switch tube as an example.

[0086] The first switch tube and the second switch tube in FIG. 1 are the first switch module and the second switch module in FIG. 14, respectively; As shown in FIG. 14, the common terminal of the first switch module S1 and the second switch module S2 is grounded via a first resistor R0.

[0087] In the bidirectional DC-DC buck-boost converter provided by this embodiment, the first resistor R0 is connected between the midpoint of the two switch tubes S1 and S2 (the source of the S1 switch tube) and PE, i.e., between point S12 and PE. By individually controlling the on / off of S1 and S2, the ground impedance circuit of the system is reconfigured to calculate the ground insulation impedance value of the system. The first resistor R0 may be connected between the midpoint of the two switch tubes S3 and S4 and PE, i.e., between point S34 and PE, or between the midpoint of the two switch tubes S5 and S6 and PE, i.e., between point S56 and PE, or between the midpoint of the two switch tubes S7 and S8 and PE, i.e., between point S78 and PE.

[0088] Below we introduce some implementations where the converter is a heric converter.

[0089] Please refer to FIG. 15, which is a schematic diagram of a heric converter provided by an embodiment of the present application.

[0090] In FIG. 15, a first resistor R0 is connected between the common end of S1 and S3 and ground.

[0091] Please refer to FIG. 16, which is a schematic diagram of another heric converter provided by an embodiment of the present application.

[0092] In FIG. 16, a first resistor R0 is connected between the inductor L and ground.

[0093] In the cases of FIGS. 15 and 16, the insulation impedance can be obtained by turning on S1 and turning off the other switches, and by turning on S3 and turning off the other switches.

[0094] Please refer to FIG. 17, which is a schematic diagram of yet another heric converter provided by an embodiment of the present application.

[0095] Assume that the insulation impedance to earth of the PV positive electrode is Rm, the insulation impedance to earth of the PV negative electrode is Rn, and R1, R2, and R3 are external resistors.

[0096] R1, R2, and R3 are connected to the rear of the bus. One end of R1 is connected to BUS+ and the other end is connected to point N, one end of R2 is connected to BUS- and the other end is connected to point N, one end of R3 is connected to PE and the other end is connected to point N, and the source of switch S1 is connected to point N and the drain of S3.

[0097] According to the converter provided by the embodiments of the present application, the DC side impedance to ground can be easily obtained, and the converter may be of multiple types, and the type of converter is not specifically limited, for example, it may be a microinverter, a string inverter, a DC-DC converter, an energy storage converter, or a centralized inverter, etc.

[0098] Based on the converter provided by the above embodiments, the embodiments of the present application further provide a method for detecting the insulation impedance of a converter, which will be described in detail below in conjunction with the accompanying drawings.

[0099] Please refer to FIG. 18, which is a flowchart of a method for detecting the insulation impedance of a converter provided by an embodiment of the present application.

[0100] According to the method for detecting the insulation impedance of a converter provided in this embodiment, the converter includes a detection resistor network and a power conversion circuit, the power conversion circuit includes a first switch tube and a second switch tube, a first end of the first switch tube is connected to the positive electrode of the DC power source, a second end of the first switch tube is connected to the first end of the second switch tube, and a second end of the second switch tube is connected to the negative electrode of the DC power source, and the second end of the first switch tube is grounded through the detection resistor network; The method comprises: Step S201: when the first switch tube and the second switch tube are both turned off, acquire the voltage between the positive electrode and the negative electrode of the DC power supply and the negative electrode to ground voltage of the DC power supply; Step S202: controlling the first switch tube or the second switch tube to be turned on; and step S203 of obtaining the insulation impedance of the converter based on the voltage between the positive and negative poles of the DC power source or the negative pole-to-ground voltage of the DC power source before or after the first switch tube or the second switch tube is turned on.

[0101] The embodiment of the present application does not specifically limit the order of S201 and S202.

[0102] The method for detecting the insulation impedance of a converter provided by this application only requires adding a detection resistor network to the converter, which includes a first switch tube and a second switch tube connected in series, with the second end of the first switch tube grounded via the detection resistor network. By controlling the on / off state of the first switch tube or the second switch tube, the magnitude of the DC voltage between the positive and negative poles of the converter and the DC negative pole voltage to ground can be changed, and the insulation impedance of the converter can be obtained in combination with the impedance of the detection resistor network. This converter insulation impedance detection method has a simple structure, low cost, and is applicable to various converter types.

[0103] The sense resistor network may include a single resistor or multiple resistors, each of which will be discussed below.

[0104] First aspect: The detection resistor network includes a first resistor, and the second end of the first switch tube is grounded through the first resistor. Second aspect: the sense resistor network includes, in addition to the first resistor, a second resistor and a third resistor; The two ends of the second resistor are respectively connected to the positive pole of the DC power source and the second end of the first switch tube; The two ends of the third resistor are respectively connected to the negative pole of the DC power source and the second end of the first switch tube.

[0105] The first switch tube may be controlled to be turned on, or the second switch tube may be controlled to be turned on. The following describes the respective implementation modes.

[0106] First solution: The step of obtaining the insulation impedance of the converter based on the voltage between the positive and negative poles of the DC power source and the voltage of the negative pole to ground of the DC power source before and after the first switch tube or the second switch tube is turned on specifically includes the step of obtaining the insulation impedance of the converter based on the voltage between the positive and negative poles of the DC power source and the voltage of the negative pole to ground of the DC power source before the first switch tube is turned on, and the voltage between the positive and negative poles of the DC power source after the first switch tube is turned on.

[0107] Second option: The step of obtaining the insulation impedance of the converter based on the voltage between the positive and negative poles of the DC power source and the negative pole-to-ground voltage of the DC power source before and after the first switch tube or the second switch tube is turned on specifically includes the step of obtaining the insulation impedance of the converter based on the voltage between the positive and negative poles of the DC power source and the negative pole-to-ground voltage of the DC power source before the second switch tube is turned on, and the negative pole-to-ground voltage of the DC power source after the second switch tube is turned on.

[0108] Here, each embodiment in this specification will be described in a progressive manner, and each embodiment will mainly describe the differences from other embodiments, and reference will be made to the similar or similar parts between the embodiments. For the systems or devices disclosed in the embodiments, the descriptions will be brief, and reference will be made to the method descriptions for the relevant parts.

[0109] The above description of the disclosed embodiments enables those skilled in the art to make or use the present application. Many modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Thus, the present application is not limited to the embodiments herein but is accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A converter, a controller, a sense resistor network, and a power conversion circuit; the power conversion circuit includes a first switch tube and a second switch tube; A first end of the first switch tube is connected to the positive electrode of a DC power supply, a second end of the first switch tube is connected to the first end of the second switch tube, a second end of the second switch tube is connected to the negative electrode of the DC power supply, and the second end of the first switch tube is grounded via the detection resistor network; The controller obtains an insulation impedance of the converter based on a voltage between the positive electrode and the negative electrode of the DC power supply and a voltage to ground of the negative electrode of the DC power supply before and after the first switch tube or the second switch tube is turned on. A converter characterized by:

2. the sense resistor network includes a first resistor; a second end of the first switch tube is grounded via the first resistor; 2. The converter according to claim 1 .

3. the sense resistor network further includes a second resistor and a third resistor; The second resistor has two ends connected to the positive electrode of the DC power source and the second end of the first switch tube, respectively; Both ends of the third resistor are respectively connected to the negative electrode of the DC power source and the second end of the first switch tube; 3. The converter according to claim 2.

4. further comprising an inductor; a second end of the first switch tube is grounded via the inductor and the first resistor connected in series; 4. The converter according to claim 2 or 3.

5. The controller obtains an insulation impedance of the converter based on a voltage between the positive and negative poles of the DC power source and a voltage to ground of the negative pole of the DC power source before the first switch tube is turned on, and a voltage to ground of the negative pole of the DC power source after the first switch tube is turned on.

5. The converter according to claim 1, wherein the first and second electrodes are electrically connected to each other.

6. The controller obtains an insulation impedance of the converter based on a voltage between the positive and negative poles of the DC power source and a voltage to ground of the negative pole of the DC power source before the second switch tube is turned on, and a voltage to ground of the negative pole of the DC power source after the second switch tube is turned on.

5. The converter according to claim 1, wherein the first and second electrodes are electrically connected to each other.

7. The converter is an isolated DC-DC converter or an isolated DC-AC converter, The first switch tube and the second switch tube are two switch tubes of the isolated DC-DC converter or a first bridge arm of a primary full bridge of the isolated DC-DC converter, and the primary full bridge of the isolated DC-DC converter includes a first bridge arm and a second bridge arm; 7. The converter according to claim 1, wherein the first and second electrodes are electrically connected to each other.

8. The converter is a T-type three-level inverter, The T-type three-level inverter further includes an inductor; a second end of the first switch tube is connected to ground via a series-connected inductor and the sense resistor network; 7. The converter according to claim 1, wherein the first and second electrodes are electrically connected to each other.

9. The converter includes a three-level Boost circuit and a neutral-point clamped inverter circuit, and the neutral-point clamped inverter circuit includes a first switch module, a second switch module, a third switch module, and a fourth switch module connected in series; the first switch tube and the second switch tube are respectively a first switch module and a second switch module in the three-level Boost circuit; Or, The first switch tube and the second switch tube are the second switch module and the third switch module of the neutral point clamped inverter circuit.

7. The converter according to claim 1, wherein the first and second electrodes are electrically connected to each other.

10. The converter includes a three-level Boost circuit and an active neutral point clamped inverter circuit, the first switch tube and the second switch tube are the first switch tube and the second switch tube in the three-level Boost circuit; 7. The converter according to claim 1, wherein the first and second electrodes are electrically connected to each other.

11. The converter is a bidirectional DC-DC buck-boost converter, The bidirectional DC-DC buck-boost converter includes a first switch module, a second switch module, a third switch module, and a fourth switch module connected in series in this order; the first switch tube and the second switch tube are the first switch module and the second switch module, respectively; a common end of the first switch module and the second switch module is grounded via the detection resistor network; 7. The converter according to claim 1, wherein the first and second electrodes are electrically connected to each other.

12. the converter is a heric converter; the heric converter includes a first bridge arm, a second bridge arm, a fifth switch module, a sixth switch module, and an LC filter, and a midpoint of the first bridge arm is grounded via the sense resistor network; the fifth switch module and the sixth switch module are connected in series and then connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm; a first end and a second end of the LC filter are connected to a midpoint of the first bridge arm and a midpoint of the second bridge arm, respectively, and the first end and the second end of the LC filter are connected to both ends of a capacitor via a first inductor and a second inductor, respectively; 7. The converter according to claim 1, wherein the first and second electrodes are electrically connected to each other.

13. the converter is a heric converter; the heric converter includes a first bridge arm, a second bridge arm, a fifth switch module, a sixth switch module, and an LC filter; the fifth switch module and the sixth switch module are connected in series and then connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm; a first end and a second end of the LC filter are respectively connected to a midpoint of the first bridge arm and a midpoint of the second bridge arm, and the first end and the second end of the LC filter are respectively connected to both ends of a capacitor via a first inductor and a second inductor; a first end of the LC filter is grounded via the first inductor and the first resistor connected in series; The first switch tube and the second switch tube are two switch tubes of the first bridge arm.

7. The converter according to claim 1, wherein the first and second electrodes are electrically connected to each other.

14. further comprising a switch; the sense resistor network is coupled to ground through the switch; The controller further controls the switch to be on when detecting the insulation impedance, and controls the switch to be off when detecting the insulation impedance. A converter according to any one of claims 1 to 13.

15. the DC power source is a solar photovoltaic array or a battery; A converter according to any one of claims 1 to 14.

16. A method for detecting insulation impedance of a converter, comprising: The converter includes a detection resistor network and a power conversion circuit, and the power conversion circuit includes a first switch tube and a second switch tube, a first end of the first switch tube is connected to a positive electrode of a DC power source, a second end of the first switch tube is connected to a first end of the second switch tube, and a second end of the second switch tube is connected to a negative electrode of the DC power source, and the second end of the first switch tube is grounded via the detection resistor network; The method comprises: When both the first switch tube and the second switch tube are turned off, acquiring a voltage between the positive electrode and the negative electrode of the DC power source and a voltage of the negative electrode of the DC power source to ground; controlling the first switch tube or the second switch tube to be turned on; Obtaining an insulation impedance of the converter based on a voltage between the positive electrode and the negative electrode of the DC power source and a voltage to ground of the negative electrode of the DC power source before and after the first switch tube or the second switch tube is turned on; A method comprising:

17. the detection resistor network includes a first resistor, and a second end of the first switch tube is grounded via the first resistor; 17. The method of claim 16.

18. the sense resistor network further includes a second resistor and a third resistor; The second resistor has two ends connected to the positive electrode of the DC power source and the second end of the first switch tube, respectively; Both ends of the third resistor are respectively connected to the negative electrode of the DC power source and the second end of the first switch tube; 17. The method of claim 16.

19. The step of obtaining the insulation impedance of the converter according to the voltage between the positive pole and the negative pole of the DC power source and the negative pole to ground voltage of the DC power source before and after the first switch tube or the second switch tube is turned on is specifically: Obtaining an insulation impedance of the converter based on a voltage between the positive and negative poles of the DC power source and a voltage to ground of the negative pole of the DC power source before the first switch tube is turned on, and a voltage between the positive and negative poles of the DC power source after the first switch tube is turned on.

19. The method according to claim 17 or 18, comprising:

20. The step of obtaining the insulation impedance of the converter according to the voltage between the positive pole and the negative pole of the DC power source and the negative pole to ground voltage of the DC power source before and after the first switch tube or the second switch tube is turned on is specifically: obtaining an insulation impedance of the converter based on a voltage between the positive and negative poles of the DC power source and a negative pole-to-ground voltage of the DC power source before the second switch tube is turned on, and a negative pole-to-ground voltage of the DC power source after the second switch tube is turned on; 19. The method according to claim 17 or 18, comprising:

Images