Apparatus for detecting fault of power relay of inverter

Patent metadata

Field	Value
Publication number	US-10594129-B2
Application number	US-201715660224-A
Country	US
Kind code	B2
Filing date	Jul 26, 2017
Priority date	Mar 6, 2017
Publication date	Mar 17, 2020
Grant date	Mar 17, 2020

Abstract

An apparatus for detecting a fault in a power relay of an inverter is disclosed. The apparatus for detecting a fault in a power relay includes: a voltage sensor configured to measure a voltage of a DC link; a current sensor configured to measure an output current applied to an inverter stage; a storage unit configured to store resistance of an initial charge resistor, a time constant of a capacitor, and a reference voltage measured when voltage drop of the DC link does not occur; and a controller configured to determine, when the voltage drop of the DC link occurs, the presence or absence of a fault in the power relay based on a difference between the reference voltage and a voltage measured after lapse of a period corresponding to the time constant.

First claim

What is claimed is:

1. An apparatus for detecting a fault in a power relay of an inverter, the apparatus comprising:
a voltage sensor configured to measure a voltage of a DC link;
a current sensor configured to measure an output current to an inverter stage;
a storage unit configured to store a resistance of an initial charge resistor, a time constant of a capacitor, and a reference voltage measured when no voltage drop occurs at the DC link; and
a controller configured to determine, when the voltage drop occurs at the DC link, whether there is the fault in the power relay based on a difference between the reference voltage and a voltage measured after a period of time corresponding to the time constant has elapsed,
wherein the controller compares the difference between the voltages with a voltage drop determined by the output current and the resistance, thereby determining whether there is the fault in the power relay.

2. The apparatus of claim 1 , wherein the controller, when the voltage drop occurs, compares a rate of the voltage drop per unit time with a rate calculated based on the measured output current, thereby determining whether the voltage drop lasts.

3. The apparatus of claim 2 , wherein the controller determines whether there is the fault in the power relay when the voltage drop lasts for a time period corresponding to the time constant.

4. The apparatus of claim 2 , wherein the comparison between the rate of the voltage drop per unit time and the calculated rate based on the measured output current is represented by the following equation:

(

V

n
+
1

-

V
n

)

/

t
p

i
out

/

i
std

>

i
dc

×
R

τ

wherein n and n+1 are symbols for distinguishing voltage measurement times, i out denotes an output current, i std denotes a rated current, t p denotes a time interval between the voltage measurement times, i dc denotes a current passing through the initial charge resistor, R denotes the initial charge resistor, and τ denotes the time constant.

5. The apparatus of claim 4 , wherein the controller determines that the voltage drop lasts if a left-hand side of the equation is larger than a right-hand side of the equation.

6. The apparatus of claim 5 , wherein the controller determines that there is the fault in the power relay when the voltage drop lasts for a time period corresponding to the time constant.

7. The apparatus of claim 1 , wherein the power relay is connected to the resistor in parallel, and the power relay is disposed between a converter stage and the DC link having the capacitor.

8. The apparatus of claim 1 , wherein the voltage sensor is configured to measure the voltage of the DC link periodically.

9. The apparatus of claim 1 , wherein the comparison between the voltages with the voltage drop determined by the output current and the resistance is represented by the following equation:

(

V
i

-

V
f

)

i
out

/

i
std

>

i
dc

×
R

wherein V i denotes a reference voltage, V f denotes a voltage measured after a time period corresponding to the time constant has elapsed, i out denotes an output current, i std denotes a rated current, i dc denotes a current passing through the initial charge resistor, and R denotes the initial charge resistor.

10. The apparatus of claim 9 , wherein the controller determines that there is the fault in the power relay if a left-hand side of the equation is larger than a right-hand side of the equation.

11. The apparatus of claim 9 , wherein the controller determines that there is no fault in the power relay if a left-hand side of the equation is equal to or smaller than a right-hand side of the equation.

Assignees

• Lsis Co Ltd

Inventors

• Son Ju-Beom

Classifications

• H02H3/044

  Checking correct functioning of protective arrangements, e.g. by simulating a fault (for differential current circuit breakers H02H3/335) · CPC title

• H02M5/40

  with intermediate conversion into DC · CPC title

• H02H7/10

  for converters; for rectifiers {(forming part of the control circuit of the converter, see the relevant group in H02M)} · CPC title

• G01R31/3278 Primary

  of relays, solenoids or reed switches (measuring contact resistance G01R27/205; high voltage magnetic switches G01R31/3271, G01R31/333; testing electric windings G01R31/72; monitoring of fail safe circuits H01H47/002) · CPC title

• H02M1/32

  Means for protecting converters other than automatic disconnection · CPC title