KR20170059741A - System and method for diagnosing dc input capacitor of inverter, and a recording medium having computer readable program for executing the method - Google Patents

System and method for diagnosing dc input capacitor of inverter, and a recording medium having computer readable program for executing the method Download PDF

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Publication number
KR20170059741A
KR20170059741A KR1020150164077A KR20150164077A KR20170059741A KR 20170059741 A KR20170059741 A KR 20170059741A KR 1020150164077 A KR1020150164077 A KR 1020150164077A KR 20150164077 A KR20150164077 A KR 20150164077A KR 20170059741 A KR20170059741 A KR 20170059741A
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South Korea
Prior art keywords
capacitance
inverter
capacitor
voltage
input
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KR1020150164077A
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Korean (ko)
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이종필
신동설
김태진
유동욱
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한국전기연구원
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Publication of KR20170059741A publication Critical patent/KR20170059741A/en

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    • G01R31/028—
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/10—Measuring sum, difference or ratio
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
    • G01R27/2605—Measuring capacitance

Abstract

An inverter direct current input terminal capacitor diagnosis system includes a power applying unit, a capacitor voltage and time measuring unit, and a capacitance calculating unit. The power applying unit applies DC power to an inverter. The capacitor voltage and time measuring unit measures a voltage across an input capacitor connected in parallel with the inverter and the time for which the voltage is measured. The capacitance calculating unit calculates the capacitance of the input capacitor by using a resistance value of an input resistance connected in series with the inverter and the input capacitor with respect to the DC power supply and the time for the voltage across the capacitor to reach a predetermined voltage value.

Description

TECHNICAL FIELD [0001] The present invention relates to an inverter direct current input terminal capacitor diagnosis system, a method thereof, and a recording medium having recorded thereon a computer readable program for executing the method. BACKGROUND OF THE INVENTION [0001]

The present invention relates to a power inverter, and more particularly, to a system and method for diagnosing a condition of a capacitor at a DC input terminal of an inverter.

Capacitors, such as electrolytic capacitors, have been used in many electronic circuits, but they are consumables having a relatively short lifetime in comparison with other components such as resistors. Particularly, when the electrolytic capacitor is broken in a power converter such as an inverter which converts a DC power source to an AC power source and controls an AC motor, it causes a catastrophic failure to peripheral components. Therefore, it is very important to replace the electrolytic capacitor before it occurs.

However, since the process of diagnosing the state of the electrolytic capacitor provided in the power conversion apparatus is very cumbersome and takes a long time, if the operation time of the power conversion apparatus exceeds a predetermined time, the electrolytic capacitor can be uniformly replaced Hole is being done.

However, since the interval for performing the overhole is set in accordance with the most unfavorable one among the electrolytic capacitors used in the product, there arises a problem that the capacitor is exchanged early to a capacitor having a good condition.

Further, since all the electrolytic capacitors used in the product are uniformly exchanged, a long time is required to perform the overhole, and there is a problem that the apparatus is required to be stopped for a long time and the cost is also increased.

In order to solve such a problem, an attempt has been made to diagnose the state of the electrolytic capacitor and to replace only electrolytic capacitors whose properties are deteriorated. However, in the conventional attempts, in order to estimate the number of capacitors used in the power inverter, the existing circuit must be changed or an additional additional circuit must be added, resulting in a complicated apparatus and an increase in cost. Further, there is a problem that it is difficult to apply to an existing power inverter which is already in use.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a system and method for easily diagnosing the state of a DC input capacitor of an inverter without changing a conventional circuit or adding an additional separate circuit .

In order to achieve the above object, an inverter direct current input terminal capacitor diagnosis system according to the present invention includes a power applying unit, a capacitor voltage and time measuring unit, and a capacitance calculating unit.

The capacitor voltage and time measuring unit measures the voltage and the voltage at both ends of the input capacitor connected in parallel to the inverter with respect to the DC power supply, and the capacitance calculating unit calculates a capacitance between the capacitor and the capacitor, The capacitance of the input capacitor is calculated using the time while reaching the preset voltage value and the resistance value of the input resistor connected in series with the inverter and the input capacitor with respect to the DC power supply.

Also for this purpose, the capacitance calculating unit can calculate the capacitance from the relationship between the time constant of the circuit and the input resistance calculated from the measured time.

According to such a configuration, the capacitance of the DC input capacitor of the inverter can be calculated by using the function of the conventional inverter controller, so that the state of the DC input capacitor of the inverter can be easily diagnosed without changing the existing circuit or adding additional circuit .

At this time, the inverter direct current input terminal capacitor diagnosis system further includes an output current measuring unit for measuring an output current flowing to the output resistor connected to the output terminal of the inverter in a state where the load is not connected, disconnecting the DC power from the inverter And the capacitance calculating section can further calculate the capacitance of the input capacitor using the output resistance value, the output current, and the voltage across the input capacitor.

To this end, the capacitance calculating unit may further calculate the capacitance using the relationship between the energy consumed in the output resistance and the capacitance voltage value.

According to this configuration, the value of the capacitance can be easily analyzed for each operation mode, and the state of the objective capacitance can be diagnosed.

In addition, a recording medium on which a computer-readable program for executing the above-described method and an invention in which the system is implemented in the form of a method is disclosed.

According to the present invention, it is possible to calculate the capacitance of the DC input capacitor of the inverter by using the function of the conventional inverter controller, so that the state of the DC input capacitor of the inverter can be easily diagnosed without changing the existing circuit or adding additional circuit .

In addition, the value of the capacitance can be easily analyzed for each operation mode, thereby making it possible to diagnose a more objective state of the capacitance.

1 is a schematic block diagram of an inverter DC input stage capacitor diagnostic system in accordance with an embodiment of the present invention;
2 is a circuit diagram for performing capacitance estimation in the inverter DC input stage capacitor diagnosis system of FIG.
3 is a schematic flow chart for implementing a method of diagnosing an inverter DC input stage capacitor according to the present invention.
Fig. 4 is a diagram showing voltage waveforms at the time of charging the DC input terminal capacitor of Fig. 2; Fig.
5 illustrates experimental results of a capacitance estimation algorithm during charging;
6 shows experimental results of a capacitance estimation algorithm during discharging;

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a schematic block diagram of a method of diagnosing an inverter DC input capacitor according to an embodiment of the present invention.

1, an inverter DC input stage capacitor diagnosis system 100 includes a power supply unit 110, a capacitor voltage and time measurement unit 120, a capacitance calculation unit 130, a power supply separation unit 140, (150).

In FIG. 1, each component of the inverter DC input capacitor diagnosis system 100 may be implemented only by hardware, but it may be more general to be implemented by software that operates on hardware.

Also, it may be implemented as a separate system from the inverter controller, and may operate through communication with the inverter controller. However, it may be more general that the inverter controller is implemented with some modules.

The power applying unit 110 applies DC power to the inverter, and the capacitor voltage and time measuring unit 120 measures the voltage and voltage at both ends of the input capacitor connected in parallel to the inverter with respect to the DC power.

At this time, since the application of the DC power, the capacitor voltage and the time measurement are physically performed through the conventional inverter controller, no additional sensor device or circuit change is necessary for the implementation of the present invention.

FIG. 2 is a circuit diagram for performing capacitance estimation in the inverter DC input stage capacitor diagnosis system of FIG. 1; FIG.

2, power supply to and separation from the inverter 250 is performed by the switch 230. When the switch 230 is connected, the DC power supply 210 is connected to the inverter 250 connected in parallel through the input resistor 220, And the DC input capacitor 240 of the inverter.

In this case, the DC power source 210 may be a variable voltage control type. In this case, the capacitance value can be estimated for various input voltage ranges, thereby increasing the objectivity of the estimated capacitance value.

The capacitance calculating section 130 calculates the capacitance of the input capacitor using the time during which the voltage across the capacitor reaches a predetermined voltage value and the resistance value of the input resistor in series with the inverter and the input capacitor with respect to the DC power source . To this end, the capacitance calculating section 130 can calculate the capacitance from the relationship between the time constant of the circuit calculated from the measured time and the input resistance.

The capacitance thus calculated is compared with a capacitance of a predetermined steady state so that the state of the capacitor can be diagnosed.

The power disconnecting unit 140 disconnects the DC power from the inverter, and the output current measuring unit 150 measures the output current flowing to the output resistance connected to the output terminal of the inverter in a state in which the load is not connected.

In this case, the power separating unit 140 is separated from the power applying unit 110. However, in actual implementation, the functions of the power applying unit 110 and the power separating unit 140 may be implemented in one module .

Again, the capacitance calculating unit 130 further calculates the capacitance of the input capacitor using the output resistance value, the output current, and the voltage across the input capacitor, and for this, the capacitance between the energy consumed in the output resistance and the capacitance voltage value The capacitance can be calculated.

According to this configuration, since the value of the DC input terminal capacitance can be calculated differently each time the capacitor is charged and discharged, it is possible to more easily analyze the capacitance value by mode, thereby further reducing the state of the objective capacitance Diagnosis can be made.

FIG. 3 is a schematic flow chart for executing a method of diagnosing an inverter DC input terminal capacitor according to the present invention.

First, DC power is applied to the inverter (S110). Accordingly, the SW (switch) is in an off state at the initial stage of charging, but is charged to the capacitor through the input resistor R in while being turned on at t 0 .

Next, the time during which the voltage and the voltage across the input capacitor connected in parallel with the inverter for the DC power supply are measured is measured (S120).

4 is a diagram showing a voltage waveform at the time of charging the DC input terminal capacitor of FIG. FIG. 4 shows the relationship of charging voltage with time during charging.

Then, the capacitance of the input capacitor is calculated using the time during which the voltage across the capacitor reaches a preset voltage value and the resistance value of the input resistor connected in series with the inverter and the input capacitor with respect to the DC power (S130).

According to the RC time constant relation, V 1 is the 63.2% voltage value of V dc . According to Equation ( 1 ), the capacitance value can be estimated by calculating the time (t 1 -t 0 ) to 63.2% of the input voltage (zero voltage) to a different point in time. Also, since the input power supply is a variable voltage control type, the capacitance value can be estimated for various input voltage ranges.

Figure pat00001

When there is an initial voltage, the capacitance is estimated by calculating the offset time according to Equation (2).

Figure pat00002

5 is a diagram showing an experimental result of a capacitance estimation algorithm for charging. 5 shows the result of calculating the capacitance value by measuring the charging time from the initial zero voltage up to 100 V to 63.2 V (C = 5000 uF, measurement C value = 4998 uF).

Then, the DC power source is disconnected from the inverter (S140). In Figure 4, the time t 2 V dc voltage is to turn off the switch (off) when kept at V 2. Subsequently, in a state in which the load is not connected, the output current flowing to the output resistance connected to the output terminal of the inverter is measured (S150).

Finally, the capacitance of the input capacitor is calculated using the output resistance value, the output current, and the voltage across the input capacitor (S160). Also, the capacitance is estimated by Equation (3) using the energy consumed in the inductor.

In the case of discharging, the capacitance value is calculated on the assumption that the energy stored in the capacitor is equal to the energy consumed in the output terminal. At this time, when the capacitor is charged and the switch SW is off, the output stage DC current i OUT is controlled to a constant value.

Figure pat00003

Where r e is the output stage resistance loss component.

FIG. 6 is a graph showing an experiment result of a capacitance estimation algorithm during discharging. In Fig. 6, the following drawing shows the DClink voltage for discharging, and the upper drawing is a figure of estimating the capacitance value (5000 uF) through the proposed algorithm after 0.2 seconds.

In the case of industrial power converters, inductors and capacitors are among the major passive components. Especially, the abnormality of the DC short capacitor is one of the main failure sources of the power conversion system. Accordingly, the present invention proposes a method for estimating the value of a DC short-circuit capacitor in an industrial power conversion apparatus through a proposed algorithm for charging / discharging without an additional diagnostic device.

According to the present invention, a method of measuring capacitance according to the type and state of a capacitor through an algorithm that can estimate capacitances during charging and discharging has been proposed. Therefore, the capacitance can be easily estimated without additional sensors or components .

Also, since the capacitance value can be estimated for two cases when the capacitor is charged and discharged, there is an advantage that it can be analyzed according to the operation mode. The circuit configuration consists of input power supply, input resistor, switch, inverter, output inductor and output resistance component.

Although the present invention has been described in terms of some preferred embodiments, the scope of the present invention should not be limited thereby but should be modified and improved in accordance with the above-described embodiments.

100: Inverter DC input stage capacitor diagnosis system
110: Power supply unit
120: Capacitor voltage and time measuring unit
130: Capacitance calculation unit
140:
210: DC power source
220: Input resistance
230: switch
240: DC input stage capacitor
250: Inverter
260: Output inductor
270: Output resistance

Claims (9)

A power applying unit for applying DC power to the inverter;
A capacitor voltage and time measuring unit measuring a voltage across the input capacitor connected in parallel with the inverter for the DC power source and a time during which the voltage is measured; And
Calculating a capacitance that calculates the capacitance of the input capacitor using a time during which the voltage across the capacitor reaches a predetermined voltage value and a resistance value of the input resistor connected in series with the inverter and the input capacitor with respect to the DC power supply, Wherein the DC input capacitor diagnosis system comprises: The method according to claim 1,
A power separator for separating the DC power from the inverter; And
And an output current measuring unit for measuring an output current flowing to an output resistance connected to an output terminal of the inverter in a state in which the load is not connected,
The capacitance calculation unit calculates,
Wherein the capacitance of the input capacitor is further calculated using the output resistance, the output current, and the voltage across the input capacitor. 3. The method of claim 2,
Wherein the capacitance calculating unit calculates the capacitance from the relationship between the time constant of the circuit calculated from the measured time and the input resistance. 3. The method of claim 2,
Wherein the capacitance calculator further calculates the capacitance using a relationship between the energy consumed in the output resistor and the capacitance voltage value. A power applying step of applying DC power to the inverter; And
Measuring a capacitor voltage and a time to measure a voltage across the input capacitor connected in parallel with the inverter to the DC power source and a time during which the voltage is measured; And
Calculating a capacitance that calculates the capacitance of the input capacitor using a time during which the voltage across the capacitor reaches a predetermined voltage value and a resistance value of the input resistor connected in series with the inverter and the input capacitor with respect to the DC power supply, Wherein the step of determining the DC input stage capacitor comprises the steps of: 6. The method of claim 5,
A power separation step of separating the DC power from the inverter; And
Further comprising an output current measurement step of measuring an output current flowing to an output resistance connected to an output terminal of the inverter in a state in which the load is not connected,
Wherein the capacitance calculating step includes:
Wherein the capacitance of the input capacitor is further calculated using the output resistance value, the output current, and the voltage across the input capacitor. The method according to claim 6,
Wherein the capacitance calculating step calculates the capacitance from the relationship between the time constant of the circuit calculated from the measured time and the input resistance. 8. The method of claim 7,
Wherein the capacitance calculating step calculates the capacitance using a relation between the energy consumed in the output resistor and the capacitance voltage value. 9. A recording medium on which a computer-readable program for executing the method according to any one of claims 4 to 8 is recorded.

KR1020150164077A 2015-11-23 2015-11-23 System and method for diagnosing dc input capacitor of inverter, and a recording medium having computer readable program for executing the method KR20170059741A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11262417B2 (en) 2018-06-29 2022-03-01 Lg Energy Solution, Ltd. Apparatus and method for testing circuit board included in battery management system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11262417B2 (en) 2018-06-29 2022-03-01 Lg Energy Solution, Ltd. Apparatus and method for testing circuit board included in battery management system

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