System and method for calculating insulation resistance

1. A system for calculating insulation resistance, the system comprising:

a first resistor unit configured to switchably connect a first node to a second node, wherein the first node is between a positive terminal of a battery and the first resistor unit, and wherein the second node is between the first resistor unit and a chassis;

a second resistor unit configured to switchably connect the second node to a third node, wherein the second node is between the second resistor unit and the chassis, and wherein the third node is between a negative terminal of the battery and the second resistor unit;

a third resistor unit configured to switchably connect the second node to the third node, wherein the second node is between the third resistor unit and the chassis, wherein the third node is negative terminal of the battery and the third resistor unit, and wherein the third resistor unit and the second resistor unit are in parallel between the second node and the third node; and

a control unit configured to control conduction states of the first, second and third resistor units,

wherein the control unit is further configured to calculate an insulation resistance between the positive terminal of the battery and the chassis, and an insulation resistance between the negative terminal of the battery and the chassis, relative to a voltage of a negative terminal side of the battery, based at least in part on (i) a first voltage difference between the second node and third node when the second node and the third node are connected through only the second resistor unit and (ii) a second voltage difference between the second node and third node when the second node and the third node are connected through both the second resistor unit and the third resistor unit.

2. The system of claim 1 , further comprising:

a voltage measuring unit configured to measure a voltage of the battery applied to the second resistor unit according to the conduction states of the first, second and third resistor units; and

a storage unit configured to store the measured first voltage difference and the measured second voltage difference.

3. The system of claim 2 , wherein the voltage measuring unit is configured to sequentially measure a voltage of the battery, the first voltage difference, and the second voltage difference, and

the control unit is configured to control the voltage measuring unit so as to measure the voltage of the battery at a predetermined time interval.

4. The system of claim 2 , wherein the voltage measuring unit is configured to measure the voltage of the battery regardless of the conduction states of the first, second and third resistor units, and

the control unit is configured to:

calculate an average voltage of the battery based on the measured voltage of the battery, and

calculate the insulation resistance between the positive terminal of the battery and the chassis and the insulation resistance between the negative terminal of the battery and the chassis by using the calculated average voltage.

5. The system of claim 1 , wherein the control unit is configured to calculate the insulation resistance between the positive terminal of the battery and the chassis based on:

R

n

=

R

E

·

R

F

·

(

(

V

⁢

/

⁢

V

GEF

-

1

)

V

⁢

/

⁢

V

GE

-

1

-

1

)

R

E

-

R

F

·

(

(

V

⁢

/

⁢

V

GEF

-

1

)

V

⁢

/

⁢

V

GE

-

1

-

1

)

wherein, Rn is the insulation resistance between the positive terminal of the battery and the chassis, R E is a resistance value of the second resistor unit, R F is a resistance value of the third resistor unit, V is a voltage value of the battery, V GEF is the second voltage difference, and V GE is the first voltage difference.

6. The system of claim 1 , wherein the control unit is configured to calculate the insulation resistance between the negative terminal of the battery and the chassis based on,

R

P

=

R

G

·

(

V

⁢

/

⁢

V

GE

-

1

)

·

R

f

·

(

(

V

⁢

/

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V

GEF

-

1

)

V

⁢

/

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V

GE

-

1

-

1

)

R

G

-

(

V

⁢

/

⁢

V

GE

-

1

)

·

R

f

·

(

(

V

⁢

/

⁢

V

GEF

-

1

)

V

⁢

/

⁢

V

GE

-

1

-

1

)

wherein, R P is the insulation resistance between the negative terminal of the battery and the chassis, R G is a resistance value of the first resistor unit, R F is a resistance value of the third resistor unit, V is a voltage value of the battery, V GEF is the second voltage difference, and V GE is the first voltage difference.

7. The system of claim 1 , wherein each of the first, second and third resistor units includes one or more resistors and switching units, and

the one or more resistors are embedded in a battery management system (BMS) configured to manage the battery.

8. A method of calculating insulation resistance, the method comprising:

controlling a conduction state of a first resistor unit which switchably connects a first node to a second node, wherein the first node is between a positive terminal of a battery and the first resistor unit, and wherein the second node is between the first resistor unit and a chassis of a vehicle;

controlling a conduction state of a second resistor unit which switchably connects the second node to a third node, wherein the second node is between the second resistor unit and the chassis, and wherein the third node is between a negative terminal of the battery and the second resistor unit; and

controlling a conduction state of a third resistor unit which is switchably connects the second node to the third node, wherein the second node is between the third resistor unit and the chassis, wherein the third node is negative terminal of the battery and the third resistor unit, wherein the third resistor unit and the second resistor unit are in parallel between the second node and the third node;

measuring (i) a first voltage difference between the second node and third node when the second node and the third node are connected through only the second resistor unit and (ii) a second voltage difference between the second node and third node when the second node and the third node are connected through both the second resistor unit and the third resistor unit; and

calculating an insulation resistance between the positive terminal of the battery and the chassis and an insulation resistance between the negative terminal of the battery and the chassis based at least in part on the measured first voltage difference and the measured second voltage difference.

9. The method of claim 8 , wherein

the method further includes storing the measured first voltage difference and the second measured voltage difference.

10. The method of claim 9 , further comprising:

the measuring further includes sequentially measuring, by a voltage measuring unit, a voltage of the battery, the first voltage difference, and the second voltage difference, and

the calculating further includes controlling the voltage measuring unit so as to measure the voltage of the battery at a predetermined time interval.

11. The method of claim 8 , wherein the measuring includes measuring the voltage of the battery regardless of the conduction states of the first, second and third resistor units, and

the calculating further includes calculating an average voltage of the battery based on the measured voltage of the battery, and calculating the insulation resistance between the positive terminal of the battery and the chassis and the insulation resistance between the negative terminal of the battery and the chassis by using the calculated average voltage.

12. The method of claim 8 , wherein the calculating includes calculating the insulation resistance between the positive terminal of the battery and the chassis based on,

R

n

=

R

E

·

R

F

·

(

(

V

⁢

/

⁢

V

GEF

-

1

)

V

⁢

/

⁢

V

GE

-

1

-

1

)

R

E

-

R

F

·

(

(

V

⁢

/

⁢

V

GEF

-

1

)

V

⁢

/

⁢

V

GE

-

1

-

1

)

wherein, Rn is the insulation resistance between the positive terminal of the battery and the chassis, R E is a resistance value of the second resistor unit, R F is a resistance value of the third resistor unit, V is a voltage value of the battery, V GEF is the second voltage difference, and V GE is the first voltage difference.

13. The method of claim 8 , wherein the calculating includes calculating the insulation resistance between the negative terminal of the battery and the chassis based on,

R

P

=

R

G

·

(

V

⁢

/

⁢

V

GE

-

1

)

·

R

f

·

(

(

V

⁢

/

⁢

V

GEF

-

1

)

V

⁢

/

⁢

V

GE

-

1

-

1

)

R

G

-

(

V

⁢

/

⁢

V

GE

-

1

)

·

R

f

·

(

(

V

⁢

/

⁢

V

GEF

-

1

)

V

⁢

/

⁢

V

GE

-

1

-

1

)

wherein, R P is the insulation resistance between the negative terminal of the battery and the chassis, R G is a resistance value of the first resistor unit, R F is a resistance value of the third resistor unit, V is a voltage value of the battery, V GEF is the second voltage difference, and V GE is the first voltage difference.

14. The method of claim 8 , wherein each of the first, second and third resistor units includes one or more resistors and switching units, and

the one or more resistors are embedded in a battery management system (BMS) configured to manage the battery.