Method for monitoring insulation monitoring circuit and battery management system
Embodiments of this application relate to the monitoring field, and disclose a method for monitoring an insulation monitoring circuit and a battery management system. In some embodiments of this application, the method for monitoring an insulation monitoring circuit includes: in a state in which a first switch and a second switch are closed and a third switch is open, obtaining a first electrical signal detected by a second monitoring module; and based on the first electrical signal and a voltage reference value between a positive electrode of a battery pack and a negative electrode of the battery pack, determining whether an insulation monitoring circuit is faulty; or obtaining a second electrical signal detected by a first monitoring module and a third electrical signal detected by a third monitoring module, and based on the second electrical signal and the third electrical signal, determining whether the insulation monitoring circuit is faulty.
1. A battery management system, comprising:
a control module; and
an insulation monitoring circuit;
wherein
the insulation monitoring circuit comprises a first voltage divider unit (R 1 ), a second voltage divider unit (R 2 ), a third voltage divider unit (R 3 ), a fourth voltage divider unit (R 4 ), a fifth voltage divider unit (R 5 ), a sixth voltage divider unit (R 6 ), a first monitoring circuit (R 7 , R 8 , C 1 ), a second monitoring circuit (R 9 , C 2 ), and a fourth monitoring circuit (R 10 , C 3 );
a first end of the first voltage divider unit (R 1 ) is connected to a positive electrode of a battery pack, a second end of the first voltage divider unit (R 1 ) is connected to a first end of the second voltage divider unit (R 2 ), a second end of the second voltage divider unit (R 2 ) is connected to a first end of the third voltage divider unit (R 3 ), a second end of the third voltage divider unit (R 3 ) is connected to a first end of the fourth voltage divider unit (R 4 ), and a second end of the fourth voltage divider unit (R 4 ) is connected to a negative electrode of the battery pack;
a first end of the fifth voltage divider unit (R 5 ) is also connected to the positive electrode of the battery pack, a second end of the fifth voltage divider unit (R 5 ) is connected to a first end of the sixth voltage divider unit (R 6 ), and a second end of the sixth voltage divider unit (R 6 ) is also connected to the negative electrode of the battery pack;
a first end of the first monitoring circuit is connected to a node between the second end of the first voltage divider unit (R 1 ) and the first end of the second voltage divider unit (R 2 ), and a second end of the first monitoring circuit (U 1 ) is connected to the control module;
a first end of the second monitoring circuit is connected to a node between the second end of the third voltage divider unit (R 3 ) and the first end of the fourth voltage divider unit (R 4 ), and a second end of the second monitoring circuit (U 2 ) is connected to the control module;
a first end of the fourth monitoring circuit is connected to a node between the second end of the fifth voltage divider unit (R 5 ) and the first end of the sixth voltage divider unit (R 6 ), and a second end of the fourth monitoring circuit (U 4 ) is connected to the control module;
wherein the control module is configured to:
when the first end of the first monitoring circuit is disconnected from the node between the second end of the first voltage divider unit (R 1 ) and the first end of the second voltage divider unit (R 2 ) by a switch (S 3 ),
obtain a first electrical signal (u 1 ) at the second end of the second monitoring circuit (U 2 );
calculate a first voltage value (Ubat 1 ) based on the first electrical signal (u 1 );
obtain a fourth electrical signal (u 4 ) at the second end of the fourth monitoring circuit (U 4 );
calculate a first reference voltage value (Ubat 2 ) based on the fourth electrical signal (u 4 ); and
determine, based on the first voltage value (Ubat 1 ) and the first reference voltage value (Ubat 2 ), whether the insulation monitoring circuit is faulty.
2. The battery management system according to claim 1 , wherein in determining whether the insulation monitoring circuit is faulty, the control module is configured to:
determine the insulation monitoring circuit is faulty when the first voltage value and the first reference voltage value are not equal or a difference between the first voltage value and the first reference voltage value exceeds a voltage threshold.
3. The battery management system according to claim 1 , wherein the first reference voltage value (Ubat 2 ) is calculated by the following formula:
Ubat2= u 4 /R 6 ·( R 5 +R 6 )
where u 4 is a voltage of the fourth electrical signal, R 5 and R 6 are resistances of the fifth voltage divider unit, and the sixth voltage divider unit, respectively.
4. The battery management system according to claim 1 , wherein the first voltage value (Ubat 1 ) is calculated by the following formula:
Ubat1= u 1 /R 4 ·( R 1 +R 2 +R 3 +R 4 )
where u 1 is a voltage of the first electrical signal, R 1 , R 2 , R 3 , R 4 are resistances of the first voltage divider unit, the second voltage divider unit, the third voltage divider unit, and the fourth voltage divider unit, respectively.
5. A method, performed by the control module of the battery management system according to claim 1 , for monitoring the insulation monitoring circuit of the battery management system, comprising:
when the first end of the first monitoring circuit is disconnected from the node between the second end of the first voltage divider unit (R 1 ) and the first end of the second voltage divider unit (R 2 ) by the switch (S 3 ),
obtaining a first electrical signal (u 1 ) at the second end of the second monitoring circuit (U 2 );
calculating a first voltage value (Ubat 1 ) based on the first electrical signal (u 1 );
obtaining a fourth electrical signal (u 4 ) at the second end of the fourth monitoring circuit (U 4 );
calculating a first reference voltage value (Ubat 2 ) based on the fourth electrical signal (u 4 ); and
determining, based on the first voltage value (Ubat 1 ) and the first reference voltage value (Ubat 2 ), whether the insulation monitoring circuit is faulty.
6. The method according to claim 5 , determining whether the insulation monitoring circuit is faulty comprises:
determining the insulation monitoring circuit is faulty when the first voltage value and the first reference voltage value are not equal or a difference between the first voltage value and the first reference voltage value exceeds a voltage threshold.
7. A control module of a battery management system, comprising:
a processor; and
a memory unit storing program codes for execution by the processor;
wherein the battery management system comprises the insulation monitoring circuit according to claim 1 , and the control module is connected to the first monitoring circuit (U 1 ), the second monitoring circuit (U 2 ) and the fourth monitoring circuit (U 4 ) of the insulation monitoring circuit;
wherein by executing the program codes, the processor is configured to:
when the first end of the first monitoring circuit is disconnected from the node between the second end of the first voltage divider unit (R 1 ) and the first end of the second voltage divider unit (R 2 ) by the switch (S 3 ),
obtain a first electrical signal (u 1 ) at the second end of the second monitoring circuit (U 2 );
calculate a first voltage value (Ubat 1 ) based on the first electrical signal (u 1 );
obtain a fourth electrical signal (u 4 ) at the second end of the fourth monitoring circuit (U 4 );
calculate a first reference voltage value (Ubat 2 ) based on the fourth electrical signal (u 4 ); and
determine, based on the first voltage value (Ubat 1 ) and the first reference voltage value (Ubat 2 ), whether the insulation monitoring circuit is faulty.