Signal detection circuit, insulation resistance detection device and system

Abstract

The disclosure provides a signal detection circuit, an insulation resistance detection device and system. The signal detection circuit comprises a switch module, and first, second, third and fourth resistance modules connected in sequence. One end of the first resistance module is connected to the positive bus of a battery module. The connection point of the first and second resistance modules is electrically connected to one end of the switch module, and the other end of the switch module is connected to the negative bus of the battery module. The connection point of the second and third resistance modules is connected to the grid ground. One end of the fourth resistance module is connected to the negative bus, and the two ends of the fourth resistance module are provided with a voltage signal detection end. The insulation resistance detection device can accurately obtain the voltage value of the fourth resistance module when the switch module is open and closed respectively, and then calculate the insulation resistance value of the battery system.

Description

Technical Field

[0001] This disclosure relates to the field of insulation testing technology, and in particular to a signal detection circuit, insulation resistance testing device and system. Background Technology

[0002] As the voltage level of battery systems continues to increase, the requirements for the insulation state of battery systems also become more stringent. When the insulation of a battery system fails, it can lead to various safety accidents.

[0003] To ensure the safety of operators, system equipment, and the surrounding environment, it is necessary to test the insulation resistance of the battery-side DC bus to ground in the battery system. Currently, the unbalanced bridge method is commonly used for insulation testing of battery systems.

[0004] However, in practical applications, the unbalanced bridge method is affected by interference from the inverter and the power grid after the battery modules in the battery system are connected to the inverter. This results in the inability to obtain the insulation resistance value of the battery system, or the obtained insulation resistance value is abnormal, making it impossible to accurately determine whether the insulation resistance has failed. Summary of the Invention

[0005] In order to overcome the defect in the prior art that the insulation resistance of the battery module in the battery system cannot be accurately determined after the inverter is turned on, this disclosure provides a signal detection circuit, an insulation resistance detection device and system.

[0006] This disclosure solves the above-mentioned technical problems through the following technical solution:

[0007] In a first aspect, this disclosure provides a signal detection circuit, which is disposed in a battery system, wherein the battery module in the battery system is electrically connected to an inverter, and both the battery module and the inverter are connected to the power grid ground.

[0008] The signal detection circuit includes:

[0009] A switch module, and a first resistor module, a second resistor module, a third resistor module, and a fourth resistor module that are electrically connected in sequence;

[0010] One end of the first resistor module is connected to the positive bus of the battery module;

[0011] The connection point between the first resistor module and the second resistor module is electrically connected to one end of the switch module, and the other end of the switch module is connected to the negative bus of the battery module;

[0012] The connection between the second resistor module and the third resistor module is connected to the power grid ground;

[0013] One end of the fourth resistor module is connected to the negative bus, and both ends of the fourth resistor module are provided with voltage signal detection terminals.

[0014] Optionally, the resistance values ​​of the first resistor module, the second resistor module, and the third resistor module are at the same level as the insulation impedance of the inverter.

[0015] Optionally, the signal detection circuit further includes a fifth resistor module, one end of which is connected to the positive bus and the other end of which is connected to the power grid ground.

[0016] The resistance value of the fifth resistor module is at the same level as the insulation impedance of the inverter.

[0017] Optionally, the signal detection circuit further includes a sixth resistor module, one end of which is connected to the negative busbar and the other end of which is connected to the power grid ground.

[0018] The resistance value of the sixth resistor module is at the same level as the insulation impedance of the inverter.

[0019] Optionally, the first resistor module, the second resistor module, the third resistor module, the fourth resistor module, the fifth resistor module, and the sixth resistor module each include any of the following: a resistor, several resistors connected in parallel, several resistors connected in series, or several resistors connected in a mixed parallel and series connection.

[0020] Optionally, the signal detection circuit further includes a filter capacitor connected in parallel with the fourth resistor module, and the capacitance value of the filter capacitor is greater than a fourth preset threshold.

[0021] Secondly, this disclosure provides an insulation resistance detection device, which is installed in a battery system. The battery module in the battery system is electrically connected to an inverter, and the battery module and the inverter are respectively connected to the power grid ground.

[0022] The insulation resistance testing device includes:

[0023] The signal detection circuit as described in the first aspect;

[0024] The control module is electrically connected to the signal detection circuit;

[0025] When the battery module is not connected to the inverter, or when the battery module is connected to the inverter but the battery module is not charging or discharging, the control module is used to control the switch module in the signal detection circuit to disconnect, and to obtain the first voltage value of the detection terminal and the second voltage value of the battery module.

[0026] The switch module is controlled to close, and the third voltage value of the detection terminal and the fourth voltage value of the battery module are obtained.

[0027] The insulation resistance of the battery system is calculated based on the first resistance value of the first resistor module, the second resistance value of the second resistor module, the third resistance value of the third resistor module, the fourth resistance value of the fourth resistor module in the signal detection circuit, and the first voltage value, the second voltage value, the third voltage value, and the fourth voltage value.

[0028] Optionally, the insulation resistance value includes the resistance value of the positive terminal to ground and the resistance value of the negative terminal to ground;

[0029] The control module calculates the insulation resistance value using the following formula:

[0030]

[0031] in,

[0032] .

[0033] Optionally, the control module is further configured to determine whether the resistance value of the positive electrode to ground and / or the resistance value of the negative electrode to ground meet the first valid condition; if they meet the condition, the battery system is determined to have experienced an insulation failure.

[0034] Optionally, when the battery module is connected to the inverter and the battery module is charging and discharging, the control module is used to obtain the third voltage value; determine whether the third voltage value meets the second valid condition; if it does, determine that the battery system has experienced an insulation failure.

[0035] Optionally, the control module is configured to acquire the fourth voltage value; calculate a first current based on the fourth voltage value, the third resistance value of the third resistor module, and the fourth resistance value of the fourth resistor module; calculate an upper voltage limit value of the fourth resistor module based on the first current and the fourth resistance value; and determine the second valid condition based on a preset lower voltage limit value and the upper voltage limit value.

[0036] Thirdly, this disclosure provides a battery management system that includes the insulation resistance detection device described in the second aspect.

[0037] Based on common knowledge in the field, the above-described embodiments can be combined in any way to obtain the preferred embodiments of this disclosure.

[0038] The positive and progressive effects of this disclosure are as follows:

[0039] The signal detection circuit can accurately obtain the voltage value of the fourth resistor module. The control module in the insulation resistance detection device, through the aforementioned signal detection circuit, can accurately obtain the voltage values ​​of the fourth resistor module when the switch module is open and closed, respectively, in two scenarios: when the battery module is not connected to the inverter, or when the battery module is connected to the inverter but not charging or discharging. Combined with the voltage values ​​of the battery module when the switch module is open and closed, the insulation resistance value of the battery system can be calculated. Attached Figure Description

[0040] Figure 1 A schematic diagram of a signal detection circuit provided in an embodiment of this disclosure;

[0041] Figure 2 This is a first schematic diagram of the signal detection circuit provided in an embodiment of the present disclosure;

[0042] Figure 3 This is a schematic diagram of the structure of the first signal detection circuit when the switch module is closed, provided in an embodiment of this disclosure;

[0043] Figure 4 This is a second schematic diagram of the signal detection circuit provided in an embodiment of the present disclosure;

[0044] Figure 5 This is a schematic diagram of the structure of the switch module provided in an embodiment of the present disclosure;

[0045] Figure 6 This is a schematic diagram of a module for an insulation resistance detection device provided in an embodiment of the present disclosure;

[0046] Figure 7 This is a schematic diagram of a battery management system provided in an embodiment of the present disclosure. Detailed Implementation

[0047] The present invention will be further illustrated by way of embodiments below, but the present invention is not limited to the scope of the embodiments described herein.

[0048] It should be noted that if the embodiments of this disclosure involve descriptions such as "first" and "second," such descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" and "second" may explicitly or implicitly include at least one of those features.

[0049] Furthermore, the technical solutions of various implementation methods can be combined with each other, but this must be based on the ability of a person skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed in this disclosure.

[0050] Example 1

[0051] Figure 1 A schematic diagram of a signal detection circuit provided in this disclosure is shown. The signal detection circuit is disposed in a battery system. The battery system includes a battery module 101 and an inverter. The battery module 101 is electrically connected to the inverter, and both the battery module 101 and the inverter are connected to the power grid ground (PE).

[0052] See Figure 1 The signal detection circuit includes:

[0053] The switch module 102 is connected in sequence to the first resistor module 103, the second resistor module 104, the third resistor module 105, and the fourth resistor module 106.

[0054] One end of the first resistor module 103 is connected to the positive bus of the battery module 101;

[0055] The connection between the first resistor module 103 and the second resistor module 104 is electrically connected to one end of the switch module 102, and the other end of the switch module 102 is connected to the negative bus of the battery module 101.

[0056] The connection between the second resistor module 104 and the third resistor module 105 is connected to the power grid ground PE.

[0057] One end of the fourth resistor module 106 is connected to the negative bus, and both ends of the fourth resistor module 106 are provided with voltage signal detection terminals 107.

[0058] In practical applications, the connection between the second resistor module 104 and the third resistor module 105 is actually connected to the battery casing, and the battery casing is then connected to the ground wire, thus realizing that the connection between the second resistor module 104 and the third resistor module 105 is connected to the power grid ground PE.

[0059] Specifically, as an optional implementation, the first resistor module 103, the second resistor module 104, the third resistor module 105, and the fourth resistor module 106 each include any of the following: a resistor, several resistors connected in parallel, several resistors connected in series, or several resistors connected in a mixed parallel and series connection.

[0060] When each of the first resistor module 103, the second resistor module 104, the third resistor module 105, and the fourth resistor module 106 corresponds to one resistor, the signal detection circuit is as follows: Figure 2 The circuit structure shown is shown.

[0061] Since each individual resistor can only withstand a limited voltage, excessive voltage can damage the resistor and cause the entire circuit to malfunction. To ensure that the voltage across each individual resistor is not too high, the first resistor module 103, the second resistor module 104, the third resistor module 105, and the fourth resistor module 106 typically include multiple resistors.

[0062] Specifically, when the switch module 102 is disconnected, the first resistor module 103 and the second resistor module 104 are connected in series to obtain a portion of the voltage, and the three resistor modules and the fourth resistor module 106 are connected in series to obtain another portion of the voltage.

[0063] The battery system itself has a certain resistance value, which is equivalent to a positive-to-ground resistor 108 being connected in series between the positive terminal of the battery module 101 and the power grid ground PE, and a negative-to-ground resistor 109 being connected in series between the negative terminal of the battery module 101 and the power grid ground PE.

[0064] Therefore, the voltage obtained by connecting the first resistor module 103 and the second resistor module 104 in series is actually equivalent to the voltage obtained by connecting the first resistor module 103 and the second resistor module 104 in series and then connecting the positive terminal to ground resistor 108 in parallel. Similarly, the voltage obtained by connecting the third resistor module 105 and the fourth resistor module 106 in series is actually equivalent to the voltage obtained by connecting the third resistor module 105 and the fourth resistor module 106 in series and then connecting the negative terminal to ground resistor 109 in parallel.

[0065] Furthermore, after the switch module 102 is closed, as the circuit structure of the signal detection circuit changes, the voltage of the battery module 101 and the voltage distribution in the signal detection circuit will also change.

[0066] See Figure 3 After switch module 102 is closed, a portion of the voltage obtained by the third resistor module 105 and the fourth resistor module 106 connected in series and then in parallel with the second resistor module 104 is actually equivalent to the voltage obtained by the third resistor module 105 and the fourth resistor module 106 connected in series and then in parallel with the second resistor module 104, and then in parallel with the negative terminal to ground resistor 109. Then the remaining portion of the voltage is obtained by the positive terminal to ground resistor 108.

[0067] The signal detection circuit provided in this embodiment is mainly used to obtain the accurate voltage value of the fourth resistor module 106 through the detection terminal 107 when the switch module 102 is in the open and closed states, respectively.

[0068] Example 2

[0069] The voltages distributed between the positive terminal and the ground resistor 108 and the negative terminal and the ground resistor 109 are uneven; that is, when the voltage of the negative terminal and the ground resistor is particularly small, the voltage value distributed to the fourth resistor module 106 is also particularly small. Due to the limited accuracy of the detection tool, the voltage value of the fourth resistor module 106 cannot be obtained. Therefore, this embodiment improves the signal detection circuit.

[0070] For example, in Figure 2 By improving the circuit structure shown, the following can be obtained: Figure 4 The signal detection circuit shown.

[0071] See Figure 4 The improved signal detection circuit in this embodiment also includes a fifth resistor module 401, one end of which is connected to the positive bus and the other end is connected to the power grid ground PE.

[0072] Among them, the resistance value of the fifth resistor module 401 is at the same level as the insulation impedance of the inverter.

[0073] That is, a smaller resistor module can be connected in parallel with the positive terminal to ground resistor 108 to reduce the voltage it receives. Alternatively, a smaller resistor module can be connected in parallel with both the positive terminal to ground resistor 108 and the negative terminal to ground resistor 109 to ensure that the voltage received by the positive terminal to ground resistor 108 and the negative terminal to ground resistor 109 is uniform.

[0074] As another optional implementation, in addition to the fifth resistor module 401 mentioned above, the signal detection circuit also includes a sixth resistor module 402, one end of which is connected to the negative bus and the other end is connected to the power grid ground PE.

[0075] Among them, the resistance value of the sixth resistor module 402 is at the same level as the insulation impedance of the inverter.

[0076] Typically, the insulation impedance of an inverter is in the megohm range, so the resistance values ​​of the fifth resistor module 401 and the sixth resistor module 402 should also be in the megohm range.

[0077] For example, if the insulation impedance of the inverter is 5 megohms, then the resistance values ​​of the fifth resistor module 401 and the sixth resistor module 402 should be greater than or equal to 1 megohm, but less than 10 megohms.

[0078] Similarly, in order to ensure that the voltage received by each individual resistor is not too large, as an optional implementation, the fifth resistor module 401 and the sixth resistor module 402 both include any of the following: a resistor, several resistors in parallel, several resistors in series, or several resistors connected in a mixed parallel and series connection.

[0079] Example 3

[0080] When the battery module 101 is connected to the inverter, it becomes impossible to obtain an accurate voltage value from the fourth resistor module 106. Therefore, this embodiment further improves the signal detection circuit.

[0081] In the first scenario, the inverter may interfere with the voltage collected by the detection terminal 107 through the DC positive and negative terminals and the power grid ground, causing the voltage value of the fourth resistor module 106 to fluctuate.

[0082] As an optional implementation, the signal detection circuit also includes a filter capacitor connected in parallel with the fourth resistor module 106. The filter capacitor is mainly used to filter the AC component in the voltage signal, so that the voltage signal collected by the detection terminal 107 remains stable.

[0083] That is, a large capacitor is connected in parallel to the fourth resistor module 106 for filtering to ensure the voltage stability of the fourth resistor module 106.

[0084] For example, a filter capacitor with a capacitance of 10uF (microfarad) is connected in parallel with the fourth resistor module 106 to keep the voltage signal collected by the detection terminal 107 stable, so that the detected voltage value of the fourth resistor module 106 is stable.

[0085] The second scenario is that the insulation impedance of the inverter is generally in the megohm range. If the first resistor module 103, the second resistor module 104, and the third resistor module 105 all use the tens or hundreds of megohm range, the battery module 101 will not have sufficient driving capability. Consequently, when the switch module 102 is open and closed, the voltage change of the fourth resistor module 106 will be too small. Due to the limited accuracy of the testing tool, the change in the voltage of the fourth resistor module 106 cannot be obtained.

[0086] As an optional implementation, the difference between the first resistance value of the first resistor module 103 and the insulation impedance of the inverter is less than a first preset threshold; and / or, the difference between the second resistance value of the second resistor module 104 and the insulation impedance of the inverter is less than a second preset threshold; and / or, the difference between the third resistance value of the third resistor module 105 and the insulation impedance of the inverter is less than a third preset threshold.

[0087] That is, in order to ensure that the driving capability of the battery module 101 is sufficient, the resistance values ​​of the first resistor module 103, the second resistor module 104 and / or the third resistor module 105 are at the same level as the insulation impedance of the inverter.

[0088] For example, when the insulation impedance of the inverter is in the megohm range, the resistance values ​​of the first resistor module 103, the second resistor module 104, and the third resistor module 105 should all be in the megohm range.

[0089] For example, if the insulation impedance of the inverter is 5 megohms, then the resistance values ​​of the first resistor module 103, the second resistor module 104, and the third resistor module 105 should be greater than or equal to 1 megohm, but less than 10 megohms.

[0090] Additionally, see Figure 5 As an optional implementation, the switching module 102 includes a MOSFET 500; the connection between the first resistor module 103 and the second resistor module 104 is electrically connected to the drain of the MOSFET 500, the gate of the MOSFET 500 is electrically connected to the control module, and the source is connected to the negative bus. Using the MOSFET 500 as the switching module not only has advantages such as high response speed, high transconductance, low noise, high analog accuracy, and strong current drive capability, but it can also be directly controlled by the control module, reducing the cost required for control.

[0091] Furthermore, a capacitor 501 and a seventh resistor module 502 are connected in parallel between the gate and the source, respectively. The capacitor 501 slows down the turn-on speed of the MOSFET 500, thereby extending its lifespan. The seventh resistor module 502 provides a bias voltage through a field-effect transistor and also acts as a discharge resistor to protect the gate and source of the MOSFET 500.

[0092] Example 4

[0093] Figure 6 An insulation resistance detection device provided in this disclosure is shown. The insulation resistance detection device is disposed in a battery system, which includes a battery module 101 and an inverter. The battery module 101 is electrically connected to the inverter, and the battery module 101 and the inverter are respectively connected to the power grid ground.

[0094] See Figure 6 The insulation resistance testing device includes:

[0095] Signal detection circuit 601 as described in any of the above embodiments;

[0096] The control module 602 is electrically connected to the signal detection circuit 601.

[0097] When the inverter is not connected to the battery module 101, or when the inverter is connected to the battery module 101 but the battery module 101 is not charging or discharging, the control module 602 controls the switch module 102 in the signal detection circuit 601 to open and obtain the first voltage value of the detection terminal 107 and the second voltage value of the battery module 101; controls the switch module 102 to close and obtains the third voltage value of the detection terminal 107 and the fourth voltage value of the battery module 101; calculates the insulation resistance value of the battery system based on the first resistance value of the first resistor module 103, the second resistance value of the second resistor module 104, the third resistance value of the third resistor module 105, the fourth resistance value of the fourth resistor module 106 in the signal detection circuit 601, and the first voltage value, the second voltage value, the third voltage value, and the fourth voltage value.

[0098] The insulation resistance value includes the resistance value between the positive terminal and the ground and the resistance value between the negative terminal and the ground.

[0099] The calculation formula corresponding to the insulation resistance value obtained by the control module 602 is as follows:

[0100]

[0101] in,

[0102] .

[0103] Specifically:

[0104]

[0105]

[0106]

[0107] Solving the above formulas simultaneously, the resistance of the positive electrode to ground can be calculated.

[0108] and negative electrode resistance to ground .

[0109] As an optional implementation, the control module 602 is also used to determine whether the resistance value of the positive electrode to ground and / or the resistance value of the negative electrode to ground meet the first valid condition; if they do not meet the condition, it is determined that the battery system has suffered an insulation failure.

[0110] The first valid condition can be understood as the allowable range of the positive electrode-to-ground resistance and / or the allowable range of the negative electrode-to-ground resistance, which are set according to actual needs. Within the allowable range, the insulation of the battery system can be considered effective; however, if it exceeds the above allowable range, the insulation of the battery system should be considered ineffective.

[0111] The first effective condition when the inverter is not connected to the battery module 101 and the first effective condition when the inverter is connected to the battery module 101 but the battery module 101 is not charging or discharging can be different.

[0112] Example 5

[0113] Because the calculated insulation resistance value of the battery system is abnormal due to interference from the inverter and the power grid when the battery module 101 is connected to the inverter and charging / discharging, this embodiment improves the above-mentioned insulation resistance detection device.

[0114] At this point, by reasonably setting the effective insulation conditions of the battery system, i.e., the allowable range of the voltage value of the fourth resistor module, it is possible to determine whether the insulation of the battery system has failed. If the voltage value of the fourth resistor module obtained by the control module 602 through the detection terminal is not within the set allowable range, it can be considered that the battery system has experienced insulation failure.

[0115] As an optional implementation, when the battery module 101 is connected to the inverter and the battery module 101 is charging and discharging, the control module 602 is used to obtain a third voltage value; determine whether the third voltage value meets the second valid condition; if it does not meet the condition, it is determined that the battery system has suffered an insulation failure.

[0116] The control module 602 is also used to obtain a fourth voltage value; calculate a first current based on the fourth voltage value, the third resistance value of the third resistor module 105 and the fourth resistance value of the fourth resistor module 106; calculate the upper limit voltage value of the fourth resistor module 106 based on the first current and the fourth resistance value; and determine a second valid condition based on the preset lower voltage limit value and the upper voltage limit value.

[0117] Specifically, when the fourth voltage value of the fourth resistor module 106 exceeds the upper voltage limit, the battery system is considered to have experienced a positive electrode insulation failure. When the fourth voltage value of the fourth resistor module 106 is lower than the preset lower voltage limit, the battery system is considered to have experienced a negative electrode insulation failure.

[0118] The preset lower voltage limit is usually 0V. However, considering actual conditions and measurement errors, the insulation resistance is generally not 0V. It can be further reduced based on the preset lower voltage limit and the calculated upper voltage limit.

[0119] For example, if the calculated upper voltage limit is 1.19V, the second effective condition can be set from 100mV (millivolts) to 1.1V.

[0120] Example 6

[0121] Figure 7This disclosure illustrates a battery management system (BMS) provided in a battery system. The battery management system includes the insulation resistance detection device 701 described in the above embodiments.

[0122] The control module 602 in the battery management system can open and close the switch module 102 in the control signal detection circuit 601, and obtain the voltage value of the fourth resistor module 106 when the switch module 102 is open and closed through the detection terminal 107, thereby determining whether the insulation of the battery system has failed.

[0123] In practical applications, the battery management system performs an insulation test before opening the positive and negative relays. Specifically, the control module 602 detects whether the positive and negative relays are open. If they are not open, it indicates that the battery module 101 is not connected to the inverter, and the insulation resistance of the battery system can be accurately calculated. If the calculated insulation resistance does not meet the first valid condition, a warning is issued, and the contactor (which connects the battery system to other devices) is not opened to prevent the battery module 101 from charging or discharging. If the insulation resistance meets the first valid condition, the control module 602 opens the positive and negative relays, connecting the battery module 101 to the inverter. After the battery module 101 is connected to the inverter, the insulation status of the battery system is continuously monitored.

[0124] The control module 602 is also used to detect whether there is charging or discharging current in the circuit where the battery module 101 is located. If there is no current, it means that the battery module 101 is not charging or discharging at this time. Similarly, the insulation resistance of the battery system can be accurately calculated to determine whether the insulation of the battery system has failed. If there is current, it means that the battery module 101 is charging or discharging at this time. The insulation of the battery system can be determined by the third voltage value of the fourth resistor module obtained when the control switch module 102 in the signal detection circuit is closed.

[0125] This disclosure provides a solution for detecting the insulation resistance of a battery system under various conditions through the above embodiments. It can comprehensively detect whether the insulation resistance of the battery system has failed, is highly targeted, and will not result in false judgments.

[0126] While specific embodiments of this disclosure have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of this disclosure is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of this disclosure, but all such changes and modifications fall within the scope of protection of this disclosure.

Claims

1. A signal detection circuit, characterized by, The signal detection circuit is arranged in a battery system, a battery module in the battery system is electrically connected with an inverter, and the battery module and the inverter are both connected to a grid ground; The signal detection circuit comprises: a switch module, and a first resistance module, a second resistance module, a third resistance module and a fourth resistance module connected in sequence; one end of the first resistance module is connected to a positive bus of the battery module; the connection point of the first resistance module and the second resistance module is electrically connected with one end of the switch module, and the other end of the switch module is connected to a negative bus of the battery module; the connection point of the second resistance module and the third resistance module is connected to the grid ground; one end of the fourth resistance module is connected to the negative bus, and both ends of the fourth resistance module are provided with a detection end of a voltage signal; the resistance values of the first resistance module, the second resistance module and the third resistance module belong to the same level as the insulation impedance of the inverter; the signal detection circuit further comprises a fifth resistance module, one end of the fifth resistance module is connected to the positive bus, and the other end of the fifth resistance module is connected to the grid ground; wherein the resistance value of the fifth resistance module belongs to the same level as the insulation impedance of the inverter; the signal detection circuit further comprises a sixth resistance module, one end of the sixth resistance module is connected to the negative bus, and the other end of the sixth resistance module is connected to the grid ground; wherein the resistance value of the sixth resistance module belongs to the same level as the insulation impedance of the inverter; the first resistance module, the second resistance module, the third resistance module, the fourth resistance module, the fifth resistance module and the sixth resistance module all comprise any one of the following conditions: one resistance, a plurality of parallel resistances, a plurality of series resistances, or a plurality of resistances connected in parallel and series; the signal detection circuit is arranged in an insulation resistance detection device; the insulation resistance detection device is arranged in a battery system, a battery module in the battery system is electrically connected with an inverter, and the battery module and the inverter are both connected to a grid ground; the insulation resistance detection device further comprises a control module, and the control module is electrically connected with the signal detection circuit; when the battery module is not connected to the inverter, or when the battery module is connected to the inverter but the battery module does not perform charging and discharging, the control module is configured to control the switch module in the signal detection circuit to be open, acquire a first voltage value of a detection end and a second voltage value of the battery module; control the switch module to be closed, acquire a third voltage value of the detection end and a fourth voltage value of the battery module; calculate an insulation resistance value of the battery system according to a first resistance value of the first resistance module, a second resistance value of the second resistance module, a third resistance value of the third resistance module, a fourth resistance value of the fourth resistance module, and the first voltage value, the second voltage value, the third voltage value and the fourth voltage value; the insulation resistance value comprises a positive electrode-to-ground resistance value and a negative electrode-to-ground resistance value; the control module calculates the insulation resistance value according to the following formula: wherein, is the first voltage value, is the second voltage value, is the third voltage value, is the fourth voltage value, is the positive electrode to ground resistance value, is the negative electrode to ground resistance value, is the first resistance value, is the second resistance value, is the third resistance value, is the fourth resistance value, is the parallel symbol.

2. The signal detection circuit of claim 1, wherein, The signal detection circuit further comprises a filter capacitor connected in parallel with the fourth resistance module, and the filter capacitor is configured to stabilize the voltage signal.

3. An insulation resistance detecting device characterized by comprising: The insulation resistance detection device is arranged in a battery system, and a battery module and an inverter in the battery system are electrically connected, and the battery module and the inverter are respectively connected to a grid ground; The insulation resistance detection device comprises: The signal detection circuit according to claim 1 or 2; A control module is electrically connected to the signal detection circuit; When the battery module is not connected to the inverter, or when the battery module is connected to the inverter but the battery module is not charging and discharging, the control module is configured to control the switch module in the signal detection circuit to be open, obtain a first voltage value of a detection terminal, and obtain a second voltage value of the battery module; The control module controls the switch module to be closed, obtains a third voltage value of the detection terminal, and obtains a fourth voltage value of the battery module; According to the first resistance value of the first resistance module, the second resistance value of the second resistance module, the third resistance value of the third resistance module, the fourth resistance value of the fourth resistance module, and the first voltage value, the second voltage value, the third voltage value, and the fourth voltage value, the insulation resistance value of the battery system is calculated.

4. The insulation resistance detection device according to claim 3, characterized by The insulation resistance value comprises a positive electrode-to-ground resistance value and a negative electrode-to-ground resistance value; The control module calculates the insulation resistance value according to the following formula: wherein, is the first voltage value, is the second voltage value, is the third voltage value, is the fourth voltage value, is the positive electrode to ground resistance value, is the negative electrode to ground resistance value, is the first resistance value, is the second resistance value, is the third resistance value, is the fourth resistance value, is the parallel symbol.

5. The insulation resistance detection device according to claim 4, characterized by The control module is further configured to determine whether the positive electrode-to-ground resistance value and / or the negative electrode-to-ground resistance value satisfies a first effective condition; the first effective condition is an allowable range of the positive electrode-to-ground resistance value and / or an allowable range of the negative electrode-to-ground resistance value; If not, it is determined that the battery system has insulation failure; and / or, When the battery module is connected to the inverter and the battery module is charging and discharging, the control module is configured to obtain the third voltage value; It is determined whether the third voltage value satisfies a second effective condition; the second effective condition is determined based on a preset lower voltage limit value and an upper voltage limit value; If not, it is determined that the battery system has insulation failure.

6. The insulation resistance detection device according to claim 5, characterized by The control module is further configured to obtain the fourth voltage value; According to the fourth voltage value, the third resistance value of the third resistance module, and the fourth resistance value of the fourth resistance module, a first current is calculated; According to the first current and the fourth resistance value, an upper voltage limit value of the fourth resistance module is calculated; The second effective condition is determined according to a preset lower voltage limit value and the upper voltage limit value.

7. A battery management system, characterized by, The insulation resistance detection device according to any one of claims 3-6.

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