KR20220028387A - Method of calculating isolation resistance and battery system using the same - Google Patents

Abstract

A battery system includes: a battery pack including battery cells; a first switch having an end connected to the positive electrode of the battery pack; first and second resistors connected between a ground and the other end of the first switch; a second switch having an end connected to the negative electrode of the battery pack; third and fourth resistors connected between the ground and the other end of the second switch; a reference voltage source connected between the ground and the fourth resistor; and a battery management system. With the first and second switches on, the battery management system determines whether first and second measurement voltages are stabilized by comparing a corresponding reference value with the deviation for a first sampling period of each of the first measurement voltage, the second measurement voltage, and the battery pack voltage that is the voltage at both ends of the battery pack. The first measurement voltage is the voltage at the contact between the first resistor and the second resistor. The second measurement voltage is the voltage at the contact between the third resistor and the fourth resistor.

Description

Insulation resistance calculation method and battery system to which it is applied

The present disclosure relates to a method for calculating insulation resistance and a battery system to which the same is applied.

When measuring the insulation resistance of a battery pack, insulation resistance and circuit performance diagnosis is performed with a voltage sample value obtained after having a fixed delay time. When an error occurs due to voltage fluctuation at the sampling point, it is difficult to detect an error in insulation resistance measurement. In addition, sampling should be performed after having a fixed delay time even when the voltage is steady.

As such, there are significant problems in measuring the insulation resistance of the battery pack, due to an error due to voltage fluctuation, and time required for measuring the voltage.

An object of the present invention is to provide an insulation resistance measurement method capable of reducing insulation resistance measurement time compared to the prior art in a voltage stabilization state, and preventing insulation resistance measurement errors in voltage fluctuations, and a battery system to which the insulation resistance measurement method is applied.

Through this, it is intended to shorten the tact time for the EOL (End Of Line Test) of the battery system. EOL refers to individual testing on the battery pack factory line, and tact time refers to the production time required for each individual.

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, a first resistor and a second resistor connected between the other end of the first switch and a ground, A second switch having one end connected to the negative electrode of the battery pack, third and fourth resistors connected between the other end of the second switch and a ground, and a reference voltage source connected between the ground and 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, which is the voltage of the battery pack, and the battery pack voltage, which is the voltage across the battery pack, with a corresponding reference value. do.

An embodiment provides an insulation resistance measurement method capable of reducing insulation resistance measurement time compared to the prior art in a voltage stabilization state, and preventing insulation resistance measurement error in a voltage fluctuation situation, and a battery system to which the same is applied. Through this, it is intended to shorten the tact time for the EOL (End Of Line Test) of the battery system.

1 is a diagram illustrating a battery system according to an embodiment.
2 is a flowchart illustrating a method for calculating insulation resistance according to an exemplary embodiment.
3 and 4 are diagrams illustrating an insulation resistance calculation circuit when measuring insulation resistance.

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 first, second, 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 a component is referred to as being “connected” or “connected” to another component, it may be directly connected or connected to the other component, but it is understood that other components may exist in between. it should be On the other hand, when it is mentioned that a certain element is "directly connected" or "directly connected" to another element, it should be understood that no other element is present in the middle.

In the present application, terms such as "comprises" or "have" are intended to designate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification exist, 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 , a fuse 60 . , 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 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, 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 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 temperature of the battery 10 Receive information such as, and control the charge/discharge current of the battery 10 based on the cell voltage and battery current of the plurality of battery cells 11-15, and cell balancing for the plurality of battery cells 11-15 You can control the action.

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 determine whether the measurement voltages V1 and V2 necessary for the insulation resistance calculation are stabilized, and after the measurement voltages V1 and V2 are stabilized, the measurement voltage V1 , V2) to calculate the insulation resistance. In FIG. 1 , the insulation resistance RL1 between the positive electrode of the battery pack 10 and the 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 resistances 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 poles 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.

2 is a flowchart illustrating a method for calculating insulation resistance according to an exemplary embodiment.

2 illustrates a method of determining whether the first and second measurement voltages V1 and V2 necessary to calculate the insulation resistance are stabilized. The BMS 20 may control the first and second relays 30 and 40 in an open state during the measurement voltage stabilization determination period.

First, the BMS 20 turns on the switch SW1 and the switch SW2 (S1).

The BMS 20 samples the voltage V1 and the voltage V2 for a predetermined period (eg, 2 seconds), and determines whether the deviation of each of the two voltages V1 and V2 during the sampling period is smaller than the first reference value. It is determined (S2). The BMS 20 measures the voltage V1 and the voltage V2 during the sampling period to calculate the deviation of the voltage V1 and the deviation of the voltage V2 during the sampling period. The BMS 20 determines whether the deviation of the voltage V1 and the deviation of the voltage V2 are smaller than a first reference value (eg, 0.001V). After performing step S2, the BMS 20 may turn off the switch SW1 and the switch SW2.

As a result of the determination of step S2, if at least one of the deviation of the voltage V1 and the deviation of the voltage V2 is equal to or greater than the first reference value, the step S1 is performed again.

As a result of the determination in step S2, if the deviation of the voltage V1 and the deviation of the voltage V2 are smaller than the first reference value, the BMS 20 performs the sampled battery pack for a predetermined sampling period (eg, 2 seconds) ( 10), it is determined whether the deviation of the voltage across both ends (hereinafter, the battery pack voltage) is smaller than a second reference value (S3). The BMS 20 measures the battery pack voltage during the sampling period to calculate a deviation of the battery pack voltage during the sampling period, and the BMS 20 has the battery pack voltage deviation smaller than a second reference value (eg, 1V). can judge whether The sampling period in step S2 and the sampling period in step S3 may be the same.

If it is determined in step S3 that the deviation of the battery pack voltage is equal to or greater than the second reference value, step S1 is performed again.

As a result of the determination in step S3, if the deviation of the battery pack voltage is less than the second reference value, the BMS 20 turns on the switch SW1 (S4).

The BMS 20 samples the voltage V1 for a predetermined period (eg, 2 seconds) and determines whether the deviation of the voltage V1 during the sampling period is smaller than a first reference value (S5). The BMS 20 measures the voltage V1 during the sampling period to calculate a deviation of the voltage V1 during the sampling period. The BMS 20 determines whether the deviation of the voltage V1 is smaller than the first reference value. After performing step S4, the BMS 20 may turn off the switch SW1.

If it is determined in step S5 that the deviation of the voltage V1 is equal to or greater than the first reference value, step S1 is performed again.

As a result of the determination in step S5, if the deviation of the voltage V1 is smaller than the first reference value, the BMS 20 determines that the deviation of the battery pack voltage sampled for a predetermined sampling period (eg, 2 seconds) is greater than the second reference value. It is determined whether it is small (S6). The BMS 20 measures the battery pack voltage during the sampling period to calculate a deviation of the battery pack voltage during the sampling period. The BMS 20 determines whether the deviation of the battery pack voltage is smaller than a second reference value (eg, 1V). The sampling period in step S5 and the sampling period in step S6 may be the same.

If it is determined in step S6 that the deviation of the battery pack voltage is equal to or greater than the second reference value, step S1 is performed again.

As a result of the determination in step S6, if the deviation of the battery pack voltage is less than the second reference value, the BMS 20 turns on the switch SW2 (S7).

The BMS 20 samples the voltage V2 for a predetermined period (eg, 2 seconds), and determines whether the deviation of the voltage V2 during the sampling period is smaller than a first reference value (S8). The BMS 20 measures the voltage V2 during the sampling period to calculate a deviation of the voltage V2 during the sampling period. The BMS 20 determines whether the deviation of the voltage V2 is smaller than the first reference value. After performing step S8, the BMS 20 may turn off the switch SW2.

As a result of the determination in step S8, if the deviation of the voltage V2 is equal to or greater than the first reference value, step S1 is performed again.

As a result of the determination in step S8, if the deviation of the voltage V2 is smaller than the first reference value, the BMS 20 determines that the deviation of the battery pack voltage sampled for a predetermined sampling period (eg, 2 seconds) is greater than the second reference value. It is determined whether it is small (S9). The BMS 20 measures the battery pack voltage during the sampling period to calculate a deviation of the battery pack voltage during the sampling period. The BMS 20 determines whether the deviation of the battery pack voltage is smaller than a second reference value (eg, 1V). The sampling period in step S8 and the sampling period in step S9 may be the same.

If it is determined in step S9 that the deviation of the battery pack voltage is equal to or greater than the second reference value, step S1 is performed again.

As a result of the determination in step S9, if the deviation of the battery pack voltage is smaller than the second reference value, the BMS 20 determines that the voltages V1 and V2 are stabilized, and calculates the insulation resistance (S10).

Hereinafter, a method for the BMS 20 to calculate the insulation resistance will be described.

3 and 4 are diagrams illustrating an insulation resistance calculation circuit when measuring insulation resistance.

First, the BMS 20 turns on the switch SW1 to obtain the measurement voltage V1, and turns off the switch SW2. Then, as shown in FIG. 3 , the battery pack 10 and the insulation resistance calculation circuit 100 are connected.

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, so 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.

If the battery pack voltage (VPT) is summarized by arranging this, Equation 1 is given below.

[Equation 1]

Next, the BMS 20 turns on the switch SW2 to obtain the measured voltage V2, and turns off the switch SW1. Then, as shown in FIG. 4 , the battery pack 10 and the insulation resistance calculation circuit 100 are connected.

The current flowing through the switch SW2 and the two resistors R3 and R4 in the on state 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). In this case, 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. Current I6 flows through insulation resistance RL1 and current I6 is the sum of currents I4 and I5, so 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 is replaced with 'D', and 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 because all values except for RL1 and RL2 are known values. To summarize, Equations 5 and 6 are shown.

[Equation 5]

[Equation 6]

In the conventional measurement of voltages required for insulation resistance calculation, a switching operation is performed after a certain time elapses. It is not known whether the voltage has stabilized even after a certain period of time has elapsed.

The battery system according to an embodiment determines whether the measured voltage is stabilized, and calculates the insulation resistance after it is stabilized. Therefore, there is no need to wait for a certain amount of time to elapse, and the time required for calculating the insulation resistance can be reduced. In addition, since the exemplary embodiment determines whether stabilization is achieved, an accurate insulation resistance can be calculated.

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
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 and a battery management system for determining whether the first measured voltage and the second measured voltage are stabilized by comparing a voltage and a deviation during a first sampling period of each of the battery pack voltages that are both ends of the battery pack with a corresponding reference value which, battery system. The method of claim 1,
The battery management system,
When the deviation of the first measured voltage and the deviation of the second measured voltage during the first sampling period is less than a first reference value, and the deviation of the battery pack voltage is less than the second reference value,
and determining whether a deviation of the first measured voltage during a second sampling period is less than the first reference value and the battery pack voltage is less than the second reference value in a state where only the first switch is on. 3. The method of claim 2,
The battery management system,
When the deviation of the first measured voltage during the second sampling period is less than the first reference value and the deviation of the battery pack voltage is less than the second reference value,
and determining whether a deviation of the second measured voltage during a third sampling period is less than the first reference value and the battery pack voltage is less than the second reference value in a state in which only the second switch is on. 4. The method of claim 3,
The battery management system,
When the deviation of the second measured voltage during the third sampling period is less than the first reference value and the deviation of the battery pack voltage is less than the second reference value, the first measured voltage and the second measured voltage are used to calculate the insulation resistance of the battery system, the battery system. The method of claim 1,
The battery management system,
After the first measurement voltage and the second measurement voltage are stabilized, only the first switch is turned on to measure the first measurement voltage, and only the second switch is turned on to measure the second measurement voltage, Calculating the insulation resistance of the battery system by using the first measured voltage and the second measured voltage, the battery system. 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 determining whether a deviation of the first measured voltage and a deviation of the second measured voltage are smaller than a first reference value by sampling a second measured voltage, which is , during a first sampling period;
determining whether a deviation of a battery pack voltage that is a voltage across the battery pack during the first sampling period is smaller than a second reference value;
determining whether a deviation of the first measured voltage during a second sampling period of the ON period of the first switch is smaller than the first reference value;
determining whether the battery pack voltage is less than the second reference value during the second sampling period;
determining whether a deviation of the second measured voltage is smaller than the first reference value during a third sampling period of the ON period of the second switch only; and
determining whether the battery pack voltage is less than the second reference value during the third sampling period;
How to calculate the insulation resistance of a battery system. 7. The method of claim 6,
When the deviation of the first measured voltage and the deviation of the second measured voltage during the first sampling period is less than a first reference value, the voltage across the battery pack during the first sampling period is the second difference in the battery pack voltage A method of calculating the insulation resistance of a battery system, judging whether it is less than a reference value. 7. The method of claim 6,
The method of calculating insulation resistance of a battery system, further comprising turning on only the first switch when the deviation of the battery pack voltage during the first sampling period is less than a second reference value. 7. The method of claim 6,
When the deviation of the first measured voltage during the second sampling period is less than the first reference value, it is determined whether the battery pack voltage is less than the second reference value during the second sampling period. . 7. The method of claim 6,
The method of calculating the insulation resistance of a battery system, further comprising: turning on only the second switch when the voltage across the battery pack during the second sampling period has a deviation of the battery pack voltage smaller than a second reference value. 7. The method of claim 6,
When the deviation of the second measured voltage during the third sampling period is less than the first reference value, determining whether the battery pack voltage is less than the second reference value during the third sampling period is calculated. . 7. The method of claim 6,
When the battery pack voltage is less than the second reference value during the third sampling period,
measuring the first measurement voltage by turning on only the first switch;
measuring the second measurement voltage by turning on only the second switch; and
Using the first measured voltage and the second measured voltage, the method further comprising the step of calculating the insulation resistance of the battery system, the method for calculating the insulation resistance of the battery system.

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