Measurement circuit and method for direct-current side insulation impedance to earth of converter

Abstract

A measurement circuit and method for direct-current side insulation impedance to earth of a converter. The measurement circuit for direct-current side insulation impedance to earth of a converter comprises: a controller, a bridge circuit and a direct-current side insulation impedance measurement assembly. The bridge circuit comprises an upper bridge arm power switch transistor group (1) and a lower bridge arm power switch transistor group (2). The direct-current side insulation impedance measurement assembly comprises a converter direct-current bus voltage source (3), a power inductor (4) and a matching resistor (5), a direct-current bus positive electrode (6) of the converter direct-current bus voltage source being electrically connected to the upper bridge arm power switch transistor group (1), and a direct-current bus negative electrode (7) being electrically connected to the lower bridge arm power switch transistor group (2). After being connected to the power inductor (4) in series, one end of the matching resistor (5) is connected to the middle point of the bridge arm between the upper bridge arm power switch transistor group (1) and the lower bridge arm power switch transistor group (2), and the other end of the matching resistor (5) is connected to a grounding end (8). The upper bridge arm power switch transistor group (1) and the lower bridge arm power switch transistor group (2) are further connected to the controller. The measurement circuit can reduce the cost of measuring the direct-current side insulation impedance.

Description

A DC side to ground insulation impedance detection circuit and method for a converter

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of China on October 19, 2023, with application number 202311364799.8 and application name “A DC side to ground insulation impedance detection circuit and method for a converter”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application belongs to the technical field of converters, and in particular relates to a circuit and method for detecting the insulation impedance of a DC side of a converter to ground. Background Art

[0003] Converters are commonly found in various electrical equipment. They can adjust the voltage, frequency, number of phases and other electrical quantities or characteristics of the power system. According to the different functions of the converter, it can be divided into rectifiers (AC to DC) <ac dc>), inverter (DC to AC <dc ac>), AC converter (AC frequency converter <ac ac>) and DC converter (DC chopper<DC Chopper> For non-isolated grid-connected DC / AC converters, such as photovoltaic grid-connected inverters, if the DC-side insulation impedance to ground is too low, it may cause personal injury or equipment damage. Therefore, it is necessary to test the DC-side insulation impedance to ground before grid connection.

[0004] In the prior art, the DC side impedance is usually detected by adding relays and other auxiliary circuits. However, the need to add relays and other auxiliary circuits to detect the DC side impedance in the prior art results in high costs for DC side insulation impedance detection.

[0005] Application Contents

[0006] The present application provides a DC side to ground insulation impedance detection circuit for a converter, aiming to solve the problem of high cost of existing DC side insulation impedance detection.

[0007] The embodiment of the present application is implemented as follows: the embodiment of the present application provides a DC side to ground insulation impedance detection circuit of a converter, the DC side to ground insulation impedance detection circuit of the converter is applicable to a converter with a bridge arm characteristic topology, comprising: a controller, a bridge circuit, and a DC side insulation impedance detection component;

[0008] The bridge circuit includes an upper arm power switch tube group and a lower arm power switch tube group;

[0009] The DC side insulation impedance detection component includes a converter DC bus voltage source, a power inductor and a matching resistor;

[0010] The DC bus positive electrode of the converter DC bus voltage source is electrically connected to the upper arm power switch tube group, and the DC bus negative electrode of the converter DC bus voltage source is electrically connected to the lower arm power switch tube group;

[0011] A bridge arm connection is formed between the upper bridge arm power switch tube group and the lower bridge arm power switch tube group;

[0012] One end of the matching resistor is connected in series with the power inductor and then connected to the midpoint of the bridge arm between the upper arm power switch tube group and the lower arm power switch tube group, and the other end of the matching resistor is connected to the ground end;

[0013] According to Thevenin's theorem, the DC input side of the converter is equivalent to a two-terminal network with a voltage source and a resistor in series;

[0014] One end of the two-terminal network is connected to the ground terminal, and the other end is connected to the negative pole of the DC bus of the converter;

[0015] The internal resistance of the two-terminal network is the equivalent insulation impedance of the DC side of the converter to the ground;

[0016] The upper bridge arm power switch tube group and the lower bridge arm power switch tube group are also respectively connected to the controller for communication.

[0017] Furthermore, the upper-arm power switch tube group includes at least one upper-arm power switch tube, and the lower-arm power switch tube group includes at least one lower-arm power switch tube.

[0018] Furthermore, the upper bridge arm power switch tube is a transistor or a MOS tube, and the lower bridge arm power switch tube is a transistor or a MOS tube.

[0019] Furthermore, the topologies with bridge arm characteristics include: single-phase H4 full-bridge topology, H5 topology, H6 topology, Heric topology, three-phase NPC topology, "I"-shaped three-level topology and "T"-shaped three-level topology.

[0020] Furthermore, when the DC side to ground insulation impedance detection circuit of the converter is used in a three-level or multi-level topology, the power inductor and the matching resistor can be connected in series and then connected to any point in the middle of the bridge arm between the upper arm power switch tube group and the lower arm power switch tube group.

[0021] Furthermore, the power inductor is connected after the bridge arm topology.

[0022] The present application also provides a method for detecting the insulation impedance of the DC side of a converter to the ground. The method is applied to the DC side insulation impedance detection circuit of the converter described in the above embodiment. The method includes the following steps:

[0023] Obtaining a control signal, wherein the control signal is used to control the on and off of the upper bridge arm power switch tube group and the lower bridge arm power switch tube group;

[0024] Acquire a first voltage value between the ground terminal and the negative pole of the DC bus and a second voltage value between the ground terminal and the negative pole of the DC bus according to the control signal;

[0025] The equivalent insulation resistance of the DC side of the converter to ground is calculated according to the first voltage value, the second voltage value and a preset calculation strategy.

[0026] Furthermore, the control signal includes a first control signal and a second control signal, and obtaining a first voltage value between the ground terminal and the negative pole of the DC bus and a second voltage value between the ground terminal and the negative pole of the DC bus according to the control signal includes:

[0027] Acquire a first voltage value between the ground terminal and the negative pole of the DC bus according to the first control signal;

[0028] A second voltage value between the ground terminal and the negative pole of the DC bus is acquired according to the second control signal.

[0029] Furthermore, the first control signal is used to control the upper arm power switch tube group to turn on, and at the same time control the lower arm power switch tube group to turn off, and sample the voltage between the ground terminal and the negative pole of the DC bus.

[0030] Furthermore, the second control signal is used to control the lower arm power switch tube group to turn on, and at the same time control the upper arm power switch tube group to turn off, and sample the voltage between the ground terminal and the negative pole of the DC bus.

[0031] The beneficial effect achieved by the present application is that the upper bridge arm power switch tube group and the lower bridge arm power switch tube group in the circuit topology are used as relays in a conventional insulation impedance detection circuit. The switching function originally performed by the relay can now achieve the same effect by alternating the switching of the power switch tube group. When the power switch tube of the upper bridge arm is turned on and the power switch tube of the lower bridge arm is turned off, a voltage value can be measured at this time. When the power switch tube of the upper bridge arm is turned off and the power switch tube of the lower bridge arm is turned on, another voltage value can be measured at this time. Then, based on these two voltage values, the equivalent insulation impedance of the DC side of the converter to the ground can be calculated. The present application utilizes the existing power switch tube to realize the detection of the insulation impedance of the DC side of the converter to the ground without adding high-cost components. It can not only simplify the circuit structure, but also reduce the cost of the original use of relays and their auxiliary circuits, making the cost lower. At the same time, it also optimizes the circuit structure and realizes the efficient use of devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0033] 1 is a circuit diagram of a DC side to ground insulation impedance detection circuit of a converter provided in an embodiment of the present application;

[0034] FIG2 is a flow chart of a method for detecting the insulation impedance of the DC side of a converter to ground provided in an embodiment of the present application.

[0035] Among them, 1. Upper arm power switch tube group; 2. Lower arm power switch tube group; 3. Converter DC bus voltage source; 4. Power inductor; 5. Matching resistor; 6. DC bus positive pole; 7. DC bus negative pole; 8. Ground terminal; 9. Equivalent insulation resistance; 10. Two-terminal network voltage source; 11. DC bus negative pole to ground voltage. Modes for Carrying Out the Invention

[0036] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0037] The present application uses the upper bridge arm power switch tube group and the lower bridge arm power switch tube group in the circuit topology as relays in a conventional insulation impedance detection circuit. The switching function was originally performed by relays, but now the same effect can be achieved by alternating switching of the power switch tube group. When the power switch tube of the upper bridge arm is turned on and the power switch tube of the lower bridge arm is turned off, a voltage value can be measured at this time. When the power switch tube of the upper bridge arm is turned off and the power switch tube of the lower bridge arm is turned on, another voltage value can be measured at this time. Then, based on these two voltage values, the equivalent insulation impedance of the DC side of the converter to the ground can be calculated. The present application utilizes existing power switch tubes to realize the detection of the insulation impedance of the DC side of the converter to the ground without adding high-cost components. It can not only simplify the circuit structure, but also reduce the cost of the original use of relays and their auxiliary circuits, making the cost lower. At the same time, it also optimizes the circuit structure and realizes efficient utilization of devices.

[0038] Example 1

[0039] As shown in FIG1 , an embodiment of the present application provides a DC side to ground insulation impedance detection circuit for a converter. The DC side to ground insulation impedance detection circuit of the converter is applicable to a converter having a bridge arm characteristic topology. For example, it can be used to detect whether the DC input terminal of a photovoltaic inverter is short-circuited to the ground or the insulation impedance to the ground is too low. The DC side to ground insulation impedance detection circuit of the converter can prevent the DC input terminal of the inverter from being short-circuited to the ground or the impedance is too low before the photovoltaic inverter is grid-connected and when the inverter casing is not grounded, thereby preventing grid insulation failure from causing damage to the human body. In addition to being applicable to photovoltaic solar panel grid-connected systems, the insulation impedance detection circuit of the converter of the present application can also be applied to other DC / AC and AC / DC systems with bridge arm characteristic topologies.

[0040] The DC side to ground insulation impedance detection circuit of the converter includes: a controller (not shown in FIG1 ), a bridge circuit and a DC side insulation impedance detection component; the bridge circuit includes an upper bridge arm power switch tube group 1 and a lower bridge arm power switch tube group 2; the DC side insulation impedance detection component includes a converter DC bus voltage source 3, a power inductor 4 and a matching resistor 5; the DC bus positive electrode 6 of the converter DC bus voltage source 3 is electrically connected to the upper bridge arm power switch tube group 1, and the DC bus negative electrode 7 of the converter DC bus voltage source 3 is electrically connected to the lower bridge arm power switch tube group 2; the upper bridge arm power switch tube group 1 and the lower bridge arm power switch tube group 2 are electrically connected. A bridge arm connection is formed between the upper-arm power switch tube group 1 and the lower-arm power switch tube group 2. One end of the matching resistor 5 is connected in series with the power inductor 4 and then connected to the midpoint of the bridge arm between the upper-arm power switch tube group 1 and the lower-arm power switch tube group 2. The other end of the matching resistor 5 is connected to the ground terminal 8. According to the Thevenin theorem, the DC input side of the converter is equivalent to a two-terminal network consisting of a voltage source and a resistor in series. One end of the two-terminal network is connected to the ground terminal 8, and the other end is connected to the negative terminal 7 of the converter DC bus. The internal resistance of the two-terminal network is the equivalent insulation resistance 9 of the converter DC side to ground. The upper-arm power switch tube group 1 and the lower-arm power switch tube group 2 are also respectively connected to the controller for communication. The communication connection can be a network connection, an electrical connection, etc. The ground terminal 8 is connected to the ground or the chassis. The bridge circuit can be a half-bridge circuit, a full-bridge circuit, etc. The DC side input of the converter DC bus voltage source 3 includes the DC bus positive terminal 6 and the DC bus negative terminal 7. The voltage source within the two-terminal network can be referred to as a two-terminal network voltage source 10, and specifically can be a Thevenin equivalent two-terminal network voltage source. In the embodiment of the present application, the upper-arm power switch tube group 1 includes at least one upper-arm power switch tube, and the lower-arm power switch tube group 2 includes at least one lower-arm power switch tube. The upper-arm power switch tube is a transistor or a MOS tube, and the lower-arm power switch tube is a transistor or a MOS tube. Of course, the upper-arm power switch tube and the lower-arm power switch tube can also be other switch tubes with the same function.

[0041] In the embodiments of this application, topologies with bridge arm characteristics include, but are not limited to, single-phase H4 full-bridge topology, H5 topology, H6 topology, Heric topology, three-phase NPC topology, "I"-shaped three-level topology, and "T"-shaped three-level topology. This application can also be used in various DC / AC converter products, including photovoltaic inverters.

[0042] In an embodiment of the present application, when the DC side to ground insulation impedance detection circuit of the converter is used in a three-level or multi-level topology, the power inductor 4 and the matching resistor 5 are connected in series and can be connected to any point in the middle of the bridge arm between the upper arm power switch tube group 1 and the lower arm power switch tube group 2.

[0043] In the embodiment of the present application, the power inductor 4 is connected after the bridge arm topology. Specifically, the power inductor 4 cannot be omitted. The power inductor 4 in the detection circuit must be after the bridge arm topology. Since the potential change at the midpoint of the bridge arm is large, it will generate large ripple and common-mode current. Placing it after the bridge arm topology and grounding it can reduce the impact of common-mode current.

[0044] In an embodiment of the present application, in FIG1 , the dotted-line box is a two-terminal network equivalently calculated using the Thevenin equivalence theorem. The two-terminal network includes a two-terminal network voltage source 10 and an equivalent insulation impedance 9 in series. One end of the ground terminal 8 is connected to the DC-side equivalent insulation impedance 9, and the other end is connected to the matching resistor 5. The equivalent insulation impedance 9 on the DC bus side is connected in series with the two-terminal network voltage source 10 and then connected to the lower-arm power switch tube group 2 and the DC bus negative pole 7. Specifically, one end of the equivalent insulation impedance 9 is connected to the two-terminal network voltage source 10, and the other end is electrically connected to the ground terminal 8 (the ground terminal 8 is connected to the earth / the housing). The ground terminal 8 is connected to the midpoint of the upper-arm power switch tube group 1 and the lower-arm power switch tube group 2 via a series circuit consisting of a matching resistor 5 and a power inductor 4.

[0045] In an embodiment of the present application, the upper-arm power switch group 1 and the lower-arm power switch group 2 in the circuit topology are used as relays in a conventional insulation impedance detection circuit. While the switching function originally performed by relays can now be achieved by alternating the power switch groups, the same effect can be achieved. When the upper-arm power switch is on and the lower-arm power switch is off, a voltage value (equal to a DC bus negative pole to ground voltage 11) between the DC input terminal (DC bus positive pole 6) and ground can be measured. When the upper-arm power switch is off and the lower-arm power switch is on, another voltage value (equal to a DC bus negative pole to ground voltage 11) between the DC input terminal (DC bus negative pole 7) and ground can be measured. These two voltage values ​​can then be used to determine the converter's DC-side equivalent insulation impedance to ground. This application utilizes existing power switching tubes to realize the detection of the DC side insulation impedance of the converter without adding high-cost components. It not only simplifies the circuit structure, but also reduces the cost of using relays and their auxiliary circuits, making the cost lower. At the same time, it also optimizes the circuit structure and realizes efficient utilization of devices.

[0046] Example 2

[0047] As shown in FIG2 , an embodiment of the present application provides a flow chart of a method for detecting the DC side insulation impedance of a converter. The method is applied to the DC side insulation impedance detection circuit of the converter in the above embodiment. The method comprises the following steps:

[0048] Step 101: Acquire a control signal.

[0049] The control signal may be a drive signal used to control the on / off switching of the upper-arm power switch group and the lower-arm power switch group. The control signal may be stored in a local memory or cloud storage. The control signal includes a first control signal and a second control signal. The first control signal is used to control the on / off switching of the upper-arm power switch group and the off / off switching of the lower-arm power switch group. The second control signal is used to control the on / off switching of the lower-arm power switch group and the off / off switching of the upper-arm power switch group.

[0050] Specifically, the controller retrieves the control signal so as to control the upper arm power switch tube group and the lower arm power switch tube group according to the control signal.

[0051] Step 102 : Acquire a first voltage value between the ground terminal and the negative electrode of the DC bus and a second voltage value between the ground terminal and the negative electrode of the DC bus according to the control signal.

[0052] In the embodiment of the present application, step 102 may include: obtaining a first voltage value between the ground terminal and the negative pole of the DC bus according to a first control signal; and obtaining a second voltage value between the ground terminal and the negative pole of the DC bus according to a second control signal.

[0053] Specifically, after receiving the control signal, the controller can determine the specific content of the control signal. If the control signal is a first control signal, it indicates that the upper-arm power switch group needs to be turned on and the lower-arm power switch group needs to be turned off. When the upper-arm power switch group is turned on and the lower-arm power switch group is turned off, a first voltage value between the ground terminal and the negative pole of the DC bus can be measured. The first voltage value can be detected in real time by a voltage measuring device.

[0054] When the control signal is the second control signal, it indicates that the lower-arm power switch group needs to be turned on and the upper-arm power switch group needs to be turned off. When the lower-arm power switch group is turned on and the upper-arm power switch group is turned off, a second voltage value between the ground terminal and the negative pole of the DC bus can be measured. Of course, the second voltage value can also be detected in real time using a voltage measuring device.

[0055] Step 103: Calculate the equivalent insulation resistance of the DC side of the converter to ground according to the first voltage value, the second voltage value, and a preset calculation strategy.

[0056] The preset calculation strategy may include a first calculation strategy and a second calculation strategy, wherein the first calculation strategy may be a first equation obtained according to the first voltage value, expressed as:

[0057] Viso1=Vx*R0 / (Riso+R0)+Vbus*Riso / (Riso+R0)

[0058] The second calculation strategy may be a second equation obtained according to the second voltage value, which may be expressed as:

[0059] Viso2=Vx*R0 / (Riso+R0)

[0060] Vx is the equivalent two-terminal network internal voltage source voltage, Vbus, Viso1 are the measured first voltage values ​​of the DC bus negative terminal BUS- to ground, and Viso2 is the second voltage value of the DC bus negative terminal BUS- to ground. R0 is the value of the matching resistor, and Riso is the equivalent total impedance of the impedances of the DC bus negative terminal BUS- to ground, which is also the equivalent insulation resistance of the DC side of the converter to ground.

[0061] Specifically, after obtaining the first voltage value and the second voltage value, the equivalent insulation resistance of the DC side of the converter to ground can be calculated according to the first equation and the second equation, which is expressed as:

[0062] Riso=R0 / [(Vbus / (Viso1-Viso2))-1]

[0063] In an embodiment of the present application, a control signal is obtained, and the control signal is used to control the on / off of the upper bridge arm power switch tube group and the lower bridge arm power switch tube group; a first voltage value of the ground terminal to the negative pole of the DC bus and a second voltage value of the ground terminal to the negative pole of the DC bus are obtained according to the control signal; and the equivalent insulation impedance of the DC side to the ground of the converter is calculated according to the first voltage value, the second voltage value and a preset calculation strategy. By controlling the on / off of the upper bridge arm power switch tube group and the lower bridge arm power switch tube group, the voltage value of the DC bus input terminal to the ground is measured to calculate the equivalent insulation impedance of the DC side to the ground of the converter. The present application utilizes existing power switch tubes to realize the detection of the insulation impedance of the DC side to the ground of the converter without adding high-cost components. It can not only simplify the circuit structure, but also reduce the cost of the original use of relays and their auxiliary circuits, which is lower in cost. At the same time, it also optimizes the circuit structure and realizes efficient use of devices.

[0064] In an embodiment of the present application, the upper arm power switch tube group and the lower arm power switch tube group in the circuit topology are used as relays in a conventional insulation impedance detection circuit. The switching function was originally performed by relays, but now the same effect can be achieved by alternating the switching of the power switch tube groups. When the power switch tube of the upper arm is turned on and the power switch tube of the lower arm is turned off, a voltage value can be measured at this time. When the power switch tube of the upper arm is turned off and the power switch tube of the lower arm is turned on, another voltage value can be measured at this time. Then, based on these two voltage values, the equivalent insulation impedance of the DC side of the converter to the ground can be calculated. The present application utilizes existing power switch tubes to realize the detection of the insulation impedance of the DC side of the converter to the ground without adding high-cost components. It can not only simplify the circuit structure, but also reduce the cost of the original use of relays and their auxiliary circuits, making the cost lower. At the same time, it also optimizes the circuit structure and realizes efficient use of devices.

[0065] It is understandable that those skilled in the art can, under the guidance of the above embodiments, combine various implementation methods in the above embodiments to obtain technical solutions of multiple implementation methods.

[0066] The above disclosure is only a preferred embodiment of the present application, and certainly cannot be used to limit the scope of rights of the present application. Therefore, equivalent changes made according to the claims of the present application are still within the scope covered by the present application.< / ac> < / dc> < / ac>

Claims

1. A DC side to ground insulation impedance detection circuit of a converter, characterized in that: The DC side to ground insulation impedance detection circuit of the converter is suitable for a converter with a bridge arm characteristic topology, comprising: a controller, a bridge circuit and a DC side insulation impedance detection component; The bridge circuit includes an upper bridge arm power switch tube group and a lower bridge arm power switch tube group; The DC side insulation impedance detection component includes a converter DC bus voltage source, a power inductor and a matching resistor; The DC bus positive electrode of the converter DC bus voltage source is electrically connected to the upper bridge arm power switch tube group, and the DC bus negative electrode of the converter DC bus voltage source is electrically connected to the lower bridge arm power switch tube group; A bridge arm connection is formed between the upper bridge arm power switch tube group and the lower bridge arm power switch tube group; One end of the matching resistor is connected in series with the power inductor and then connected to the midpoint of the bridge arm between the upper bridge arm power switch tube group and the lower bridge arm power switch tube group, and the other end of the matching resistor is connected to the ground end; According to Thevenin's theorem, the DC input side of the converter is equivalent to a two-terminal network with a voltage source and a resistor in series; One end of the two-terminal network is connected to the ground terminal, and the other end is connected to the negative pole of the DC bus of the converter; The internal resistance of the two-terminal network is the equivalent insulation impedance of the DC side of the converter to the ground; The upper bridge arm power switch tube group and the lower bridge arm power switch tube group are also respectively connected to the controller for communication.

2. The DC side to ground insulation impedance detection circuit of the converter according to claim 1, characterized in that: The upper bridge arm power switch tube group includes at least one upper bridge arm power switch tube, and the lower bridge arm power switch tube group includes at least one lower bridge arm power switch tube.

3. The DC side to ground insulation impedance detection circuit of the converter according to claim 2, characterized in that: The upper bridge arm power switch tube is a transistor or a MOS tube, and the lower bridge arm power switch tube is a transistor or a MOS tube.

4. The DC side to ground insulation impedance detection circuit of the converter according to claim 1, characterized in that: The topologies with bridge arm characteristics include: single-phase H4 full-bridge topology, H5 topology, H6 topology, Heric topology, three-phase NPC topology, "I"-shaped three-level topology and "T"-shaped three-level topology.

5. The DC side to ground insulation impedance detection circuit of the converter according to claim 1, characterized in that: When the DC side to ground insulation impedance detection circuit of the converter is used in a three-level or multi-level topology, the power inductor and the matching resistor can be connected in series and then connected to any point in the middle of the bridge arm between the upper bridge arm power switch tube group and the lower bridge arm power switch tube group.

6. The DC side to ground insulation impedance detection circuit of the converter according to claim 1, characterized in that: The power inductor is connected after the bridge arm topology.

7. A method for detecting the insulation impedance of a DC side of a converter to ground, wherein the method is applied to a DC side insulation impedance detection circuit of a converter according to any one of claims 1 to 6, and is characterized in that: The method comprises the steps of: Obtaining a control signal, wherein the control signal is used to control the on and off of the upper bridge arm power switch tube group and the lower bridge arm power switch tube group; Acquire a first voltage value between the ground terminal and the negative pole of the DC bus and a second voltage value between the ground terminal and the negative pole of the DC bus according to the control signal; The DC side equivalent insulation impedance of the converter to ground is calculated according to the first voltage value, the second voltage value and a preset calculation strategy.

8. The method for detecting the insulation impedance of the DC side of the converter to the ground according to claim 7, characterized in that: The control signal includes a first control signal and a second control signal, and obtaining a first voltage value between the ground terminal and the negative pole of the DC bus and a second voltage value between the ground terminal and the negative pole of the DC bus according to the control signal includes: Acquire a first voltage value between the ground terminal and the negative pole of the DC bus according to the first control signal; A second voltage value between the ground terminal and the negative pole of the DC bus is acquired according to the second control signal.

9. The method for detecting the insulation impedance of the DC side of the converter to the ground according to claim 8, characterized in that: The first control signal is used to control the upper bridge arm power switch tube group to turn on, and control the lower bridge arm power switch tube group to turn off, and to sample the voltage between the ground terminal and the negative pole of the DC bus.

10. The method for detecting the insulation impedance of the DC side of the converter to the ground according to claim 9, characterized in that: The second control signal is used to control the lower bridge arm power switch tube group to turn on, and at the same time control the upper bridge arm power switch tube group to turn off, and sample the voltage between the ground terminal and the negative pole of the DC bus.

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