KR20220043647A - ISOLATION STATE diagnosis METHOD AND BATTERY SYSTEM USING THE SAME - Google Patents

Abstract

The present invention relates to an insulation state diagnosis method to prevent misdiagnosis of insulation resistance caused by noise and a battery system using the same. According to the present invention, the battery system comprises: a battery pack including a plurality of battery cells; a first switch having one end connected to a positive electrode of the battery pack; a first resistor and second resistor connected between the other end of the first switch and the ground; a second switch having one end connected to a negative electrode of the battery pack; a third resistor and fourth resistor connected between the other end of the second switch and the ground; a reference voltage source connected between the ground and the fourth resistor; and a battery management system. In an on-state of the first switch and second switch, the battery management system compares a first measurement voltage which is a voltage at a junction between the first resistor and the second resistor, a second measurement voltage which is a voltage at a junction between the third resistor and the fourth resistor, and a reference value corresponding to deviation during a first sampling period of each battery pack voltage, which is the voltage at both ends of the battery pack, to determine whether the first measurement voltage and the second measurement voltage are stabilized.

Description

Insulation state diagnosis method and battery system applied thereto {ISOLATION STATE diagnosis METHOD AND BATTERY SYSTEM USING THE SAME}

The present disclosure relates to an insulation state diagnosis method and a battery system to which the same is applied.

The battery system includes a circuit for measuring the insulation resistance between the battery and the vehicle chassis ground in order to prevent electric shock to the driver due to the leakage current of the battery. In addition, in order to detect an erroneous measurement due to a failure of the insulation resistance measurement circuit, the battery system performs a diagnosis on the insulation resistance measurement circuit.

For the diagnosis of the insulation resistance measurement circuit, the insulation resistance measurement circuit measures the voltages of a specific contact, and it takes time to measure the voltages, and if the voltage fluctuates due to vehicle noise during the voltage measurement time, the insulation resistance measurement circuit An error may occur in the diagnosis.

For accurate insulation resistance measurement circuit diagnosis, when an error occurs multiple times in the insulation resistance measurement circuit, it is diagnosed as having an error in the insulation resistance measurement circuit. Accordingly, there is a limit in that the time required for diagnosis increases.

An object of the present invention is to provide a method for diagnosing insulation state that can prevent erroneous diagnosis of insulation resistance due to noise, and to prevent the need to measure insulation resistance multiple times to diagnose an abnormality in insulation resistance calculation circuit, and a battery system to which it is applied.

In a battery system according to an aspect of the present invention, the battery system includes a battery pack including a plurality of battery cells, a first switch having one end connected to a positive electrode of the battery pack, and a connection between the other end of the first switch and a ground a first resistor and a second resistor, a second switch having one end connected to the negative electrode of the battery pack, a third resistor and a fourth resistor connected between the other end of the second switch and a ground, the ground and the a reference voltage source coupled between the fourth resistor; and a battery management system. The battery management system may include, in an on state of the first switch and the second switch, a first measured voltage that is a voltage of a contact point between the first resistor and the second resistor, and a contact point between the third resistor and the fourth resistor. It is determined whether the first measured voltage and the second measured voltage are stabilized by comparing the deviation during the first sampling period of each of the second measured voltage that is the voltage of the battery pack and the battery pack voltage that is the voltage at both ends of the battery pack with a corresponding reference value do.

The battery management system generates a compensation insulation resistance by subtracting a predetermined adjustment resistance from the calculated insulation resistance when the error rate is out of the first threshold range and within the second threshold range, and the compensation insulation resistance is set to a predetermined threshold If the resistance is higher than the resistance, it can be judged as an insulation state.

The adjustment resistance may be set as an error of the calculated insulation resistance when the error rate is an upper boundary value of the second critical range.

The battery management system may determine the insulation state when the calculated insulation resistance is equal to or greater than a predetermined threshold resistance when the error rate is within the first threshold range.

The battery management system may stop the operation of the battery system when the error rate is out of the second threshold range.

The battery management system may stop the operation of the battery system by calculating the insulation resistance as many times as the number of exceptions allowed when the error rate is out of the first threshold range and within the second threshold range.

A method for diagnosing an insulation state according to another aspect of the present invention includes turning on a first switch connected to a positive pole of a battery pack including a plurality of battery cells and a second switch connected to a negative pole of the battery pack; A first measured voltage, which is a voltage of a contact point between the first and second resistors connected between the first switch and ground, and a second voltage, a voltage of a contact point between the third and fourth resistors, which are connected between the second switch and the ground, 2 Calculating the voltage across the battery pack by using the measured voltage, calculating an error rate that is a ratio between the measured battery pack voltage and the calculated battery pack voltage, the error rate is outside the first threshold range and the second Calculating insulation resistance using a first measured voltage when only the first switch is in an on state and a second measured voltage when only the second switch is in an on state within a predetermined number of allowed exceptions when within a threshold range may include.

The method for diagnosing the insulation state includes generating a compensation insulation resistance by subtracting a predetermined adjustment resistance from the insulation resistance calculated when the error rate is outside the first threshold range and within the second threshold range, and the compensation insulation resistance is set to a predetermined value. The method may further include determining an insulation state if it is greater than or equal to the critical resistance of .

The method for diagnosing the insulation state may further include determining the insulation state if the insulation resistance calculated when the error rate is within the first critical range is equal to or greater than a predetermined threshold resistance.

The method for diagnosing the insulation state may further include stopping the operation of the battery system when the error rate is out of the second threshold range.

The method for diagnosing the insulation state includes counting the number of times of calculating the insulation resistance each time when the error rate is out of the first threshold range and within the second threshold range, and when the count value reaches the allowable number of exceptions, the battery system It may further include the step of stopping the operation of.

The adjustment resistance may be set as an error of the calculated insulation resistance when the error rate is an upper boundary value of the second critical range.

Provided are a method for diagnosing an insulation state that can prevent erroneous diagnosis of insulation resistance due to noise, and the need to measure insulation resistance multiple times to diagnose whether an insulation resistance calculation circuit is abnormal, and a battery system to which the method is applied.

1 is a diagram illustrating a battery system according to an embodiment.
2 is a waveform diagram illustrating switching times of switches of an insulation resistance calculation circuit.
3 is a diagram for explaining a method of calculating a battery pack voltage.
4 is a diagram illustrating a method for diagnosing an insulation state.
5 is a diagram illustrating a connection relationship between a battery pack and an insulation resistance calculation circuit during a period T2-T3 in the waveform diagram of FIG. 2 .
6 is a diagram illustrating a connection relationship between a battery pack and an insulation resistance calculation circuit during a period T4-T5 in the waveform diagram of FIG. 2 .

Hereinafter, the embodiments disclosed in the present specification will be described in detail with reference to the accompanying drawings, but identical or similar components are given the same and similar reference numerals, and overlapping descriptions thereof will be omitted. The suffixes "module" and/or "part" for components used in the following description are given or mixed in consideration of only the ease of writing the specification, and do not have distinct meanings or roles by themselves. In addition, in describing the embodiments disclosed in the present specification, if it is determined that detailed descriptions of related known technologies may obscure the gist of the embodiments disclosed in the present specification, the detailed description thereof will be omitted. In addition, the accompanying drawings are only for easy understanding of the embodiments disclosed in the present specification, and the technical idea disclosed herein is not limited by the accompanying drawings, and all changes included in the spirit and scope of the present invention , should be understood to include equivalents or substitutes.

Terms including an ordinal number such as 1st, 2nd, etc. may be used to describe various elements, but the elements are not limited by the terms. The above terms are used only for the purpose of distinguishing one component from another.

When an element is referred to as being “connected” or “connected” to another element, it is understood that it may be directly connected or connected to the other element, but other elements may exist in between. it should be On the other hand, when it is said that a certain element is "directly connected" or "directly connected" to another element, it should be understood that the other element does not exist in the middle.

In the present application, terms such as “comprises” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

1 is a diagram illustrating a battery system according to an embodiment.

The battery system 1 includes a battery pack 10 , a battery management system (BMS) 20 , a first relay 30 , a second relay 40 , a current sensor 50 , and a fuse 60 . , a battery pack voltage sensor 70 , and an insulation resistance calculation circuit 100 .

The battery pack 10 includes a plurality of battery cells 11-15 connected in series. In FIG. 1 , the battery pack 10 is illustrated as including five battery cells 11 - 15 , but this is an example and the invention is not limited thereto.

The current sensor 50 detects a current (hereinafter, referred to as battery current) flowing through the battery pack 10 , and the current sensor 50 may transmit a signal indicating the sensed current to the BMS 20 .

The fuse 60 is connected between the positive electrode of the battery pack 10 and the output terminal P+, and may be blown when its temperature reaches a threshold due to an excessive current.

The battery pack voltage sensor 70 measures the battery pack voltage VP between the positive electrode and the negative electrode of the battery pack 10 . For example, the BMS 20 may request voltage measurement from the battery pack voltage sensor 70 , and the battery pack voltage sensor 70 may measure the battery pack voltage in response to the request and transmit it to the BMS 20 . .

The BMS 20 is connected to the plurality of battery cells 11-15 to measure the cell voltage and the battery pack 10 voltage of the plurality of battery cells 11-15, and the battery current and the battery pack 10 voltage. Receive information such as temperature, control the charge/discharge current of the battery pack 10 based on the cell voltage, battery current, etc. of the plurality of battery cells 11-15, and control the charge/discharge current of the plurality of battery cells 11-15 The cell balancing operation can be controlled.

The BMS 20 controls the opening and closing of the first relay 30 and the second relay 40 for charging/discharging control of the battery pack 10 . The BMS 20 may generate and supply control signals VG1 and VG2 for controlling the opening and closing of the first relay 30 and the second relay 40 .

The BMS 20 controls the insulation resistance calculation circuit 100 to calculate the insulation resistance using the measured voltages V1 and V2 required for the insulation resistance calculation. In FIG. 1 , the insulation resistance RL1 between the positive electrode of the battery pack 10 and the chassis ground and the insulation resistance RL2 between the negative electrode and the ground of the battery pack 10 are connected. This is an example for describing the insulation resistors RL1 and RL2, and the invention is not limited thereto.

The first relay 30 is connected between the positive electrode of the battery pack 10 and the output terminal (P+), and the second relay 40 is connected between the negative electrode of the battery pack 10 and the output terminal (P-) . The battery system 1 may further include a precharge resistor and a precharge relay connected in parallel to at least one of the first relay 30 and the second relay 40 . The battery system 1 may include only one of the first relay 30 and the second relay 40 .

The insulation resistance calculation circuit 100 is connected between the positive and negative electrodes of the battery pack 10 and to the ground.

The insulation resistance calculation circuit 100 includes two switches SW1 and SW2 , four resistors R1-R4 , and a reference voltage source VR.

A switch SW1, a resistor R1, and a resistor R2 are connected between the positive pole of the battery pack 10 and the ground, and a switch SW2, a resistor R3, a resistor R4, and a reference voltage source ( VR) is connected between the negative pole of the battery pack 10 and the ground.

One end of the switch SW1 is connected to the positive electrode of the battery pack 10 , the other end of the switch SW1 is connected to one end of the resistor R1 , and the other end of the resistor R1 is one end of the resistor R2 . is connected to, and the other end of the resistor R2 is connected to the ground.

One end of the switch SW2 is connected to the negative electrode of the battery pack 10 , the other end of the switch SW2 is connected to one end of the resistor R4 , and the other end of the resistor R4 is one end of the resistor R3 . is connected to, and the other end of the resistor R3 is connected to the reference voltage source VR.

The switch SW1 switches according to the switching signal SC1 supplied from the BMS 20 , and the switch SW2 switches according to the switching signal SC2 supplied from the BMS 20 . The BMS 20 turns on or off each of the switch SW1 and the switch SW2 by generating each of the switching signal SC1 and the switching signal SC2 at an on level or an off level.

The BMS 20 according to an embodiment calculates the error rate of the insulation resistance calculation circuit 100, and when the error rate is smaller than the first threshold range (normal condition), the insulation resistance measurement is performed and insulation based on the measured insulation resistance Diagnose whether there is breakdown, and if the error rate is above the first critical range and less than the second critical range (the first abnormal condition), the insulation resistance is compensated and the insulation breakdown is diagnosed based on the compensated insulation resistance, and the diagnosis result is insulation breakdown state, or when the first abnormal condition occurs as many times as the number of allowed exception handling occurs, or the error rate is equal to or greater than the second threshold range, the battery system 1 is stopped. The BMS 20 may transmit it to the electronic control circuit of the vehicle through CAN communication along with the shutdown of the battery system 1 . Then, the vehicle may not even start driving.

2 is a waveform diagram illustrating switching times of switches of an insulation resistance calculation circuit.

2 shows the waveforms of the two switching signals SC1 and SC2, and when the switching signals SC1 and SC2 are at the on level LON, the switches SW1 and SW2 are turned on, and the switching signals SC1 and SC2 are turned on. ) is the off level LOFF, the switches SW1 and SW2 are turned off.

At time point T1, both switches (SW1, SW2) are turned on, at time point T2, switch (SW2) is turned off, at time point T3, switch (SW1) is turned off, at time point T4, switch (SW2) is turned on and the switch SW2 is turned off at time T5.

During the period T1-T2, the BMS 20 calculates the error rate of the insulation resistance calculation circuit 100. Specifically, just before time point T2, the BMS 20 calculates the voltage between the positive electrode and the negative electrode of the battery pack 10 (hereinafter, battery pack voltage) using the insulation resistance calculation circuit 100, The battery pack voltage sensor 70 directly measures the battery pack voltage.

3 is a diagram for explaining a method of calculating a battery pack voltage.

As shown in FIG. 3 , when the BMS 20 measures the battery pack voltage using the insulation resistance calculation circuit 100 , the two switches SW1 and SW2 are in an on state.

The BMS 20 calculates the battery pack voltage VP by using the two measured voltages V1 and V2. For example, the BMS 20 calculates a voltage VP1 between the positive electrode of the battery pack 10 and the chassis ground using the measured voltage V1, and uses the measured voltage V2 to The voltage VP2 between the negative electrodes of the battery pack 10 is calculated, and the battery pack voltage VP is calculated by adding the two voltages.

Specifically, since the current IP is V1/R2, the voltage VP1 is R1*IP+V1. Since the current IN is (VR-V2)/R3, the voltage VP2 is R4*IN-V2. By adding the two voltages VP1 and VP2, the battery pack voltage VP of V1-V2+RI*IP+R4*IN is calculated.

The BMS 20 calculates an error rate (K=VP/VPS) by dividing the calculated battery pack voltage VP by the battery pack voltage VPS measured by the battery pack voltage sensor 70 .

4 is a diagram illustrating a method for diagnosing an insulation state.

First, the BMS 20 calculates the error rate K by the above-mentioned method (S1).

The BMS 20 determines whether the error rate K is within a first threshold range K1 (S2).

As a result of the determination in step S2, when the error rate K is within the first critical range K1, the BMS 20 calculates the insulation resistance (S3).

The method of calculating the insulation resistance of the BMS 20 is as follows.

After a time point T2 , the switch SW1 is in an on state, the switch SW2 is in an off state, and the BMS 20 may acquire the measured voltage V1 during the on period T2-T3 of the switch SW1 .

5 is a diagram illustrating a connection relationship between a battery pack and an insulation resistance calculation circuit during a period T2-T3 in the waveform diagram of FIG. 2 .

The current flowing through the switch SW1 and the two resistors R1 and R2 in the on state is set to 'I1', the current flowing through the insulation resistor (RL1) is set to 'I2', and the Set the flowing current to the current 'I3'. Then, the sum of the voltage VR1 across the resistor R1, the measured voltage V1, and the voltage VRL2 across the resistor RL2 is equal to the battery pack voltage VPT (VPT=VR1+V1+VRL2) .

The voltage VR1 across the resistor R1 is the product of the current I1 and the resistor R1, and the current I1 is the measured voltage V1 divided by the resistor R2. Therefore, the voltage VR1 is (V1/R2)*R1. A current I3 flows through the insulation resistor RL2, and the current I3 is the sum of the currents I1 and I2, so the voltage VRL2 is [V1/R2+{(V1/R2)*R1+V1}/RL1]*RL2.

When the battery pack voltage (VPT) is summarized, Equation 1 is given below.

[Equation 1]

Next, the BMS 20 turns off the switch SW1 at a time point T3 to obtain the measurement voltage V2, turns on the switch SW2 at a time point T4, and turns on the switch SW2 at a time point T5 off The BMS 20 may acquire the measured voltage V1 during the ON period T4-T5 of the switch SW2 .

FIG. 6 is a diagram illustrating a connection relationship between a battery pack and an insulation resistance calculation circuit during periods T4-T5 in the waveform diagram of FIG. 2 .

The current flowing through the on-state switch SW2 and the two resistors R3 and R4 is set to I4, the current flowing through the insulation resistor RL2 is set to I5, and the current flowing through the insulation resistor RL1 is set to I3 set to

Then, the sum of the voltage VR4 across the resistor R4, the measured voltage V2 of the ground reference, and the voltage VRL1 across the resistor RL1 is equal to the battery pack voltage VPB (VPB=VR4-V2) + VRL1). At this time, the ground reference measurement voltage is a voltage obtained by subtracting the measurement voltage V2 from the ground, and the polarity of the measurement voltage V2 is changed to a negative voltage based on the current direction of the current I1.

The voltage VR4 across the resistor R4 is the product of the current I4 and the resistor R4, and the current I4 is the voltage VR-V3 obtained by subtracting the measured voltage V2 from the reference voltage VR. Since it is a value divided by the resistance R3, the voltage VR4 is (VR-V2)/R3*R4. A current I6 flows through the insulation resistance RL1 and a current I6 is the sum of the currents I4 and I5, so the voltage VRL1 is {(VR-V2)/R3}+[(VR-V2)/R3+{(VR-V2) /R3*R4-V2}/RL2]*RL1.

The battery pack voltage (VPB) is summarized as shown in Equation 2 below.

[Equation 2]

In Equation 1, (V1/R2)*R1+V1 to 'A', V1/R2 to 'B', (VR-V2)/R3*R4-V2 to 'C', (VR-V2 )/R3 by substituting 'D' for arrangement, Equations 1 and 2 are the same as Equations 3 and 4 below.

[Equation 3]

[Equation 4]

In Equations 3 and 4, values of RL1 and RL2 can be obtained based on Equations 3 and 4, since all values except for RL1 and RL2 are known values. To summarize this, Equations 5 and 6 are shown.

[Equation 5]

[Equation 6]

The BMS 20 determines whether a smaller value among the insulation resistances RL1 and RL2 measured during the period T2-T5 is equal to or greater than the threshold resistance VTH (S4).

As a result of the determination in step S4, if the smaller value among the insulation resistances RL1 and RL2 is equal to or greater than the threshold resistance VTH, the BMS 20 determines that the insulation resistances RL1 and RL2 are in a normal state, that is, in an insulation state (S5). ). Since the BMS 20 can determine whether there is an abnormality by calculating the insulation resistance at every predetermined period, it can be repeated from step S1 again after the predetermined period has elapsed.

As a result of the determination in step S4, if the smaller value among the insulation resistances RL1 and RL2 is less than the threshold resistance VTH, the BMS 20 determines that insulation breakdown has occurred and stops the power supply of the battery system 1 (S6). ). For example, the BMS 20 opens the first and second relays 30 and 40 . In addition, the BMS 20 may notify the electronic control circuit of the vehicle through CAN communication.

In step S2, if the error rate K is out of the first threshold range, the BMS 20 determines whether the error rate K is within a second threshold range (> a range wider than the first threshold range, K2) (S7) .

As a result of the determination in step S7 , when the error rate K is equal to or greater than the second threshold range K2 , the BMS 20 stops the power supply of the battery system 1 ( S8 ). For example, the BMS 20 opens the first and second relays 30 and 40 . In addition, the BMS 20 may notify the electronic control circuit of the vehicle through CAN communication.

As a result of the determination in step S7, when the error rate K is within the second threshold range K2, the BMS 20 increases the count value n by one (S9). The BMS 20 determines whether the count value n has reached the number of exception handling times N_TH (S10). As a result of the determination in step S10 , if the count value n is equal to the number of exception processing times N_TH, the BMS 20 stops the power supply of the battery system 1 ( S16 ). For example, the BMS 20 opens the first and second relays 30 and 40 . In addition, the BMS 20 may notify the electronic control circuit of the vehicle through CAN communication.

As a result of the determination in step S10, if the count value n is smaller than the number of exception processing times N_TH, the insulation resistances RL1 and RL2 are calculated in the same manner as in step S3 (S11).

Next, the BMS 20 compensates the insulation resistances RL1 and RL2 by subtracting the adjustment resistance RM from the calculated insulation resistances RL1 and RL2 ( S12 ). Hereinafter, the compensated insulation resistances RL1 and RL2 are referred to as compensated insulation resistances CRL1 and CRL2.

The BMS 20 determines whether a smaller value among the compensation insulation resistances CRL1 and CRL2 is equal to or greater than the threshold resistance VTH ( S13 ).

As a result of the determination in step S13, if the smaller value among the compensation insulation resistances CRL1 and CRL2 is equal to or greater than the threshold resistance VTH, the BMS 20 determines that the insulation resistances RL1 and RL2 are in a normal state, that is, in an insulation state ( S14). Since the BMS 20 can determine whether there is an abnormality by calculating the insulation resistance at every predetermined period, it can be repeated from step S1 again after the predetermined period has elapsed.

As a result of the determination in step S13 , if the smaller value among the compensation insulation resistances CRL1 and CRL2 is less than the threshold resistance VTH, the BMS 20 determines that insulation breakdown has occurred, and stops the power supply of the battery system 1 . (S15). For example, the BMS 20 opens the first and second relays 30 and 40 . In addition, the BMS 20 may notify the electronic control circuit of the vehicle through CAN communication.

If the error rate increases due to noise of the battery pack voltage or an abnormality in the insulation resistance calculation circuit, determine whether the insulation resistance value calculated through the insulation resistance calculation circuit is caused by an abnormality in the battery pack voltage or insulation resistance calculation circuit it's difficult. If the calculated insulation resistance when the error rate is increased is not trusted as in the prior art, the battery system cannot be used even in the case of an increase in the error rate due to noise of the battery pack voltage. For reference, an increase in the error rate means that the value decreases or increases with respect to 1, and the difference between the error rate and 1 (eg, absolute value |error rate-1|) increases.

In addition, since it takes a considerable amount of time to calculate the insulation resistance, it takes an extremely long time to repeatedly calculate the insulation resistance to determine that there is an actual abnormality in the insulation resistance calculation circuit.

That is, in order to prevent the battery system from being unusable due to the noise of the battery pack voltage, or from taking time to repeatedly calculate the insulation resistance, in one embodiment, the error rate is out of the first threshold range but the second threshold range , the insulation state is diagnosed by subtracting the adjustment resistance from the calculated insulation resistance. Therefore, the higher the adjustment resistance is set, the more strictly the insulation condition diagnosis is performed.

That is, even if the error rate is within the second threshold range, there may be an error in the insulation resistance calculated by the insulation resistance calculation circuit 100 when it is out of the first threshold range. Although there is an error in the insulation resistance, if it is trusted as it is, a serious problem of electric shock to the driver of the vehicle may occur. Accordingly, when the error rate is between the first critical range and the second critical range, the compensated insulation resistance obtained by subtracting the adjustment resistance RM from the calculated insulation resistance is compared with the threshold resistance. In this way, it is possible to strengthen the criteria for diagnosing the insulation state, that is, insulation breakdown.

The adjustment resistance may be set based on the calculated error of the insulation resistance when the error rate K is the upper boundary value of the second critical range K2. For example, when the second critical range K2 is 0.94 or more and 1.06 and the error rate K is 1.06, it is assumed that an error of 300 kohm may occur in the calculation of the insulation resistance. Then, the adjustment resistor can be set to 300 kohm. In this case, when the insulation state diagnosis is strictly performed, the adjustment resistor RM may be set to a value obtained by adding a predetermined margin to 300 kohm.

The electronic control circuit of the vehicle may receive a signal informing of this from the BMS 20 when the error rate is out of the second threshold range, the insulation resistance calculation is performed as many times as an exception is allowed, or the insulation is broken. Then, the electronic control circuit may alert the user by notifying the user through an interface such as a display of the vehicle.

As described above, according to an embodiment, even in the case of an increase in the error rate due to noise, the insulation state may be diagnosed by calculating the insulation resistance by the number of allowed exceptions.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those of ordinary skill in the field to which the present invention belongs are also entitled to the rights of the present invention. belong to the scope

1: battery system
10: battery pack
20: Battery Management System (BMS)
30: first relay
40: second relay
50: current sensor
60: fuse
70: battery pack voltage sensor
100: insulation resistance calculation circuit

Claims (12)

a battery pack including a plurality of battery cells;
a first switch having one end connected to the positive electrode of the battery pack;
a first resistor and a second resistor connected between the other end of the first switch and the ground;
a second switch having one end connected to the negative electrode of the battery pack;
a third resistor and a fourth resistor connected between the other end of the second switch and a ground;
a reference voltage source connected between the ground and the fourth resistor; and
In an ON state of the first switch and the second switch, a first measurement voltage that is a voltage of a contact point between the first resistor and a second resistor, and a second measurement voltage that is a voltage of a contact point between the third resistor and the fourth resistor When a battery pack voltage that is a voltage across the battery pack is calculated using voltage, and an error rate that is a ratio between the measured battery pack voltage and the calculated battery pack voltage is outside the first threshold range and is within the second threshold range, A battery management system for calculating insulation resistance using a first measured voltage when only the first switch is in an on state and a second measured voltage when only the second switch is in an on state within the allowable number of exceptions of battery system. According to claim 1,
The battery management system,
When the error rate is outside the first critical range and within the second critical range, a compensation insulation resistance is generated by subtracting a predetermined adjustment resistance from the calculated insulation resistance, and when the compensation insulation resistance is equal to or greater than a predetermined threshold resistance, the insulation state Judging by the battery system. 3. The method of claim 2,
The adjustment resistor is
When the error rate is an upper boundary value of the second threshold range, it is set as an error of the calculated insulation resistance. According to claim 1,
The battery management system,
If the calculated insulation resistance is greater than or equal to a predetermined threshold resistance when the error rate is within the first critical range, the battery system is determined to be an insulation state. According to claim 1,
The battery management system,
When the error rate is out of the second threshold range, stopping the operation of the battery system. According to claim 1,
The battery management system,
When the error rate is out of the first threshold range and within the second threshold range, when the insulation resistance calculation is performed as many times as the number of exceptions allowed, the operation of the battery system is stopped. turning on a first switch connected to a positive electrode of a battery pack including a plurality of battery cells and a second switch connected to a negative electrode of the battery pack;
A first measurement voltage that is a voltage of a contact point between the first and second resistors connected between the first switch and ground, and a voltage of a contact point between the third and fourth resistors connected between the second switch and ground calculating a voltage across the battery pack using a second measured voltage;
calculating an error rate that is a ratio between the measured battery pack voltage and the calculated battery pack voltage; and
When the error rate is out of the first threshold range and within the second threshold range, the first measured voltage when only the first switch is in the on state and the second measured voltage when only the second switch is in the on state within a predetermined number of allowable exceptions A method for diagnosing an insulation state, comprising the step of calculating insulation resistance using the measured voltage. 8. The method of claim 7,
generating a compensation insulation resistance by subtracting a predetermined adjustment resistance from the calculated insulation resistance when the error rate is out of the first threshold range and within the second threshold range; and
The method for diagnosing an insulation state further comprising determining an insulation state when the compensation insulation resistance is equal to or greater than a predetermined threshold resistance. 9. The method of claim 8,
The adjustment resistor is
When the error rate is an upper boundary value of the second critical range, it is set as an error of the calculated insulation resistance. 8. The method of claim 7,
The method for diagnosing an insulation state further comprising determining an insulation state when the calculated insulation resistance is greater than or equal to a predetermined threshold resistance when the error rate is within the first critical range. 8. The method of claim 7,
When the error rate is out of the second threshold range, further comprising the step of stopping the operation of the battery system, the insulation state diagnosis method. 8. The method of claim 7,
counting the number of times the insulation resistance is calculated each time when the error rate is out of the first threshold range and within the second threshold range; and
When the count value reaches the allowable number of exceptions, the method further comprising stopping the operation of the battery system.

Images