KR101144314B1 - Multi-level inverter switch fault detection apparatus and method - Google Patents

Abstract

The present invention relates to an apparatus and method for diagnosing a failure of an inverter, and more particularly, to an apparatus and a method for diagnosing a failure of a multi-stage switch of a multi-level inverter capable of determining a failure of a multi-stage switch constituting the inverter. As described above, the present invention is a device for diagnosing a failure of a multi-stage switch provided in an inverter of a multilevel that outputs three-phase AC power to drive a motor. Distance code between the feature vector and the fault feature vector by code-booking the feature vector (reference feature vector) at the time of fault for each switch in advance, and converting the fault diagnosis current waveform output from the inverter into a fault feature vector in real time. An apparatus and method for diagnosing a multi-stage switch failure of a multilevel inverter including a control unit for determining a switch corresponding to a codebooked feature vector having a minimum value as a failure switch are provided.

Inverter, PWM, Switch, Fault Diagnosis, Multilevel, Motor

Description

Multi-stage inverter fault diagnosis apparatus and method {MULTI-LEVEL INVERTER SWITCH FAULT DETECTION APPARATUS AND METHOD}

The present invention relates to an apparatus and method for diagnosing a failure of an inverter, and more particularly, to an apparatus and a method for diagnosing a failure of a multi-stage switch of a multi-level inverter capable of determining a failure of a multi-stage switch constituting the inverter.

In general, the inverter converts a DC voltage into an AC voltage, and is equipped with a fault protection function, so that a fault indication is immediately displayed when an abnormality is found in the inverter at the moment of supplying an operation command to the inverter after applying power.

Insulated Gate Bipolar Transistors (IGBTs) are used for inverters. These IGBTs are power semiconductors, which are widely used in the voltage range of 300V or higher, and are especially used for high-efficiency, high-speed power systems.

However, such an inverter has a problem in that it is not possible to determine which switch is faulty and the prognosis of the entire system is not possible.

Accordingly, in most industrial applications, AC drive systems exhibit a sensitive response to failures occurring in the system, and when one of several failures occurs, there is a problem in that an unplanned system shutdown is required.

Disruption of such a system causes a lot of economic loss and inefficiency of the work, which causes a problem of lowering reliability for profit generation.

The present invention has been made in view of the above problems, and an object thereof is to provide a multistage switch failure diagnosis apparatus and method for predicting a failure of a multistage switch constituting an inverter.

Another object of the present invention is to determine whether a particular switch is faulted among the inverter's multi-stage switches by outputting a database of feature vectors of voltage / current waveforms detected in three phases in the short-circuit state of each switch of the inverter. An apparatus and method for diagnosing multi-stage switch failure of a multilevel inverter are provided.

Another object of the present invention is to provide a multi-stage inverter fault diagnosis apparatus and method for determining a fault switch among the multi-stage switches of the inverter to provide judgment information during prognostic check of the entire system.

The objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

Multi-stage switch fault diagnosis apparatus of a multi-level inverter according to an aspect of the present invention for achieving the above object, to diagnose the failure of the multi-stage switch provided in the multi-level inverter for driving the motor by outputting three-phase AC power In the apparatus, a failure diagnosis output from the inverter in real time after codebooking a feature vector (reference feature vector) at the time of a fault for each switch from an AC current waveform outputted by sequentially shorting the switches constituting the multistage switch. And a controller for converting a current waveform into a fault feature vector and determining a switch corresponding to a codebooked feature vector having a minimum distance error between the feature vector and the fault feature vector as a fault switch.

Preferably, each switch is extracted by a feature vector extraction algorithm and a feature vector extraction algorithm for extracting a feature vector from a current waveform at the time of failure of each switch so as to determine whether a specific switch has failed according to a state of a multi-stage switch of the inverter. It further includes a memory in which the feature vector for each short state of the codebook is stored.

)를 코드북화한다.Preferably, the control unit converts the output AC current waveform by DQ, and then calculates an average value of the horizontal axis and the vertical axis using Equation 1 below, and calculates the average value of the calculated horizontal axis and the vertical axis into Equation 2 below. Feature vector obtained by applying

) Codebook.

(Equation 1)

(Equation 2)

는 수평축 평균값,

는 수직축 평균값을 의미하며, i=각 스위치의 개수, j=샘플링수를 의미한다.here,

Is the mean value of the horizontal axis,

Denotes the average value of the vertical axis, i = the number of switches, j = the number of sampling.

Preferably, the control unit is a multi-stage inverter fault diagnosis apparatus, characterized in that for calculating the distance error between the feature vector and the fault feature vector using the following equation (3).

(Equation 3)

여기서 P_i,j는 고장 특징 벡터, 즉 점검하려는 고장가능성이 존재하는 시스템의 특정벡터를 의미하고, d_i,j는 특징 벡터를 의미한다. 또한, M은 스위치의 갯수를 나타낸다.

Here, P _{i, j} means a fault feature vector, that is, a specific vector of a system in which there is a possibility of failure to be checked, and d _{i, j} means a feature vector. In addition, M represents the number of switches.

는 고장 특징 벡터를 의미하고,

는 특징 벡터를 의미한다.here,

Means the fault feature vector,

Means a feature vector.

Preferably, the feature vector codebook has a size of the number of switches * the number of samplings.

According to another aspect of the present invention, a multi-stage switch fault diagnosis method of a multi-level inverter is a method for diagnosing a failure of a multi-stage switch provided in a multi-level inverter for outputting three-phase AC power to drive a motor. Sequentially code-singing the feature vectors (reference feature vectors) at the time of failure for each switch from the AC current waveform output by short-circuiting the switches constituting the circuit; And converting the fault diagnosis current waveform output in real time from the inverter into a fault feature vector, and determining a switch corresponding to a codebooked feature vector having a minimum distance error between the feature vector and the fault feature vector as a fault switch. It includes.

)를 코드북화한다.Preferably, the process of the database is the DQ conversion of the AC current waveform, the average value of the horizontal axis and the vertical axis is calculated using Equation 4 below, and the average value of the calculated horizontal axis and the vertical axis is expressed by Equation 5 below. The feature vector obtained by applying to

) Codebook.

(Equation 4)

(5)

는 수평축 평균값,

는 수직축 평균값을 의미하며, i=각 스위치의 개수, j=샘플링수를 의미한다.here,

Is the mean value of the horizontal axis,

Denotes the average value of the vertical axis, i = the number of switches, j = the number of sampling.

Preferably, the distance error is calculated using Equation 6 below.

(6)

여기서 P_i,j는 고장 특징 벡터, 즉 점검하려는 고장가능성이 존재하는 시스템의 특정벡터를 의미하고, d_i,j는 특징 벡터를 의미한다. 또한, M은 스위치의 갯수를 나타낸다.

Here, P _{i, j} means a fault feature vector, that is, a specific vector of a system in which there is a possibility of failure to be checked, and d _{i, j} means a feature vector. In addition, M represents the number of switches.

는 고장 특징 벡터를 의미하고,

는 특징 벡터를 의미한다.here,

Means the fault feature vector,

Means a feature vector.

Preferably, the feature vector codebook has a size of the number of switches * the number of samplings.

The present invention has the effect of diagnosing the failure of each of the multi-stage switch composed of a multi-stage by the above-mentioned problem solving means.

In addition, even if the abnormality of each switch occurs with a slight time difference, it is possible to distinguish the specific failure of the switch, it is possible to provide the decision information when checking the prognosis of the entire system.

In the following description, specific details of the multi-stage switch fault diagnosis apparatus and method of the present invention are shown to provide a more comprehensive understanding of the present invention, and the present invention may be readily made without these specific details and also by variations thereof. It will be apparent to one of ordinary skill in the art that the present invention can be practiced in a timely manner.

Inverter according to the present invention is a configuration that requires a multi-switch power conversion device consisting of multiple switches, configured to convert the voltage / current of direct current to alternating current by performing the sampling of pulse square wave having a height consisting of multiple rather than one layer do.

In the present invention, the failure of a specific switch among the multistage switches constituting the inverter is measured in the form of voltage or current.

On the other hand, the present invention will be described in the following operation and operation on the premise that the switch is a multi-stage switch circuit with 72 switches constituting the inverter, pulse width modulation (PWM) is 30 degrees intervals. In addition, the following describes a process of using the output current waveform of the inverter to determine the failure of a particular switch of the multi-stage switch of the inverter. However, the output voltage waveform of the inverter may be used. In addition, the extraction of the feature vector below uses the DQ transform as information for fault recognition through pattern classification, and the obtained feature vector has uniqueness and consistency according to the fault. The method proposed in the present invention simplifies the characteristics of the algorithm for feature vector extraction by removing the relevant part of the frequency of the Fourier Descriptor and removing the Invariance characteristic for the rotation transformation.

Hereinafter, a preferred embodiment according to the present invention will be described in detail with reference to the accompanying drawings, it will be described focusing on the parts necessary to understand the operation and action according to the present invention.

1 is a configuration diagram of a multi-stage switch fault diagnosis apparatus of a multilevel inverter according to an exemplary embodiment of the present invention, and FIG. 2 is an internal configuration diagram of an inverter in FIG. 1.

Referring to FIG. 1, a multi-stage switch failure diagnosis system 100 of a multi-level inverter according to the present invention includes an input power source 11, a rectifier 13, an inverter (INV) 20, a motor 15, And a load 17 is configured.

The rectifier 13 rectifies the DC power supplied from the input power 11 to output the rectified DC power. Since the rectifier 13 is a generally known technique, a detailed description thereof will be omitted.

The inverter (INV) 20 pulse-modulates the DC power rectified by the switching operation of the multi-stage switch (Pulse Width Modulation (PWM)) and applies the three-phase AC power to the motor 15 to the control unit 33. Is authorized. Here, the switch structure of the inverter is composed of a multi-stage switch for the A phase, B phase, and C phase as shown in FIG.

The motor 15 operates by the AC power supplied from the inverter INV 20 to operate the load 17.

The storage unit 31 stores a feature vector extraction algorithm for extracting feature vectors from current waveforms at the time of failure of each switch so as to determine whether a particular switch has failed according to the state of the multi-stage switch of the inverter (INV) 20. do. In the storage unit 31, the feature vector for each short state of each switch is codebooked and stored by a feature vector extraction algorithm.

The control unit 33 codebooks the feature vectors at the time of failure of each switch through the feature vector extraction algorithm and stores them in the storage unit 31. This feature vector codebook serves as a reference for determining a faulty switch among the multi-stage switches, which will be described later. Then, the control unit 33 calculates the Euclidean distance vector of each point from the center value of the waveform of the three-phase current output from the inverter (INV) 20 by using the DQ transformation, and the minimum between the obtained feature vectors The switch corresponding to the codebook feature vector having the lowest value among the distance errors obtained by using the square method is determined as the fault switch. A method of determining such a failing switch will be described in detail below.

The display unit 35 displays the state of the system and the intervener (INV) 20 under the control of the control unit 33, and displays information on the faulty switch among the multi-stage switches of the inverter (INV) 20. In this case, the display unit 35 may use an LCD. In this case, the display unit 35 may include an LCD controller, a memory capable of storing screen data (not shown), and an LCD display element (not shown). have. Herein, when the display unit 35 is implemented by using a touch screen method, the display unit 35 may be an input unit.

A process of feature vector codebooking by a feature vector extraction algorithm of a multi-stage switch fault diagnosis apparatus of a multilevel inverter having such a technical configuration will be described.

3 is an exemplary diagram illustrating an output current waveform of an inverter in FIG. 1, and FIG. 4 is a waveform diagram of the output current waveform of FIG. 3 obtained by DQ conversion.

Referring to FIG. 3, the inverter (INV) 20 inverts and outputs a DC current according to a short circuit state of a specific switch among multi-stage switches to AC current.

Subsequently, when the output current waveform of FIG. 3 is DQ-converted, values of the horizontal axis and the vertical axis may be displayed by a flat pager as shown in FIG. 4. At this time, as shown in FIG. 4, the DQ-converted current waveform has a waveform that is distorted out of a circular shape. This is the waveform generated when a particular switch fails. Here, the DQ transform is obtained by the following Equation 7 for reference.

Where ia is a-phase current, ib is b-phase current, ic is c-phase three-phase current, and ids is the current projected on d-axis by currents ia, ib and ic when DQ conversion, iqs Is the current projected on the q-axis in the currents ia, ib, and ic when the DQ conversion is performed, and ios is the image current when the DQ conversion is performed.

The controller 33 calculates and obtains the horizontal axis average value and the vertical axis average value of the values of the horizontal axis and the vertical axis of FIG. 4 through Equation 8 below.

는 수평축 평균값,

는 수직축 평균값을 의미하며, i=1, ㆍㆍㆍ,72이며, j=1,ㆍㆍㆍ,2000이다. here,

Is the mean value of the horizontal axis,

Denotes an average value of the vertical axis, i = 1, ..., 72, and j = 1, ..., 2000.

)를 생성한다.Subsequently, the controller 33 substitutes the horizontal and vertical axis mean values obtained through Equation 8 into Equation 9 to obtain a feature vector (

)

The controller 33 codes the feature vectors obtained through Equation 9 into a database and stores them in the storage unit 31. The feature vector codebook has a size of 72 * 2000.

As a result, the control unit 33 makes a database of feature vector codebooks of failure feature patterns of the switches for the multi-stage switches forming the inverter.

Thereafter, the controller 33 performs a DQ conversion on the fault diagnosis current waveform (that is, the current waveform output through the inverter) input in real time through the inverter (INV) 20, and then the equations (8) and (9). It is converted into fault feature vector.

와 특징 벡터 코드북의 유클리디안 거리(거리차이)를 하기 수학식 10을 이용하여 연산한다.As an example, assuming that the first switch of the inverter (INV) 20 is faulty, the control unit 33 may determine the fault feature vector.

And the Euclidean distance (distance difference) of the feature vector codebook are calculated using Equation 10 below.

That is, the center value of the DQ transform is obtained, the Euclidean distance vector of each point is obtained from the center value, and the error using the least square method between the obtained feature vectors is obtained.

여기서 P_i,j는 고장 특징 벡터, 즉 점검하려는 고장가능성이 존재하는 시스템의 특정벡터를 의미하고, d_i,j는 특징 벡터를 의미한다. 또한, M은 스위치의 갯수를 나타낸다.

Here, P _{i, j} means a fault feature vector, that is, a specific vector of a system in which there is a possibility of failure to be checked, and d _{i, j} means a feature vector. In addition, M represents the number of switches.

By using Equation 10, the controller 33 determines that the switch corresponding to the feature vector having the minimum distance error and the failure pattern databased in the feature vector codebook is a failure.

)을 내는 i번째의 특징 벡터에 대응하는 i번째 스위치를 고장으로 판단한다.That is, the smallest value among the measured distance errors (

It is determined that the i-th switch corresponding to the i-th feature vector yielding 1) is a failure.

Thereafter, the controller 33 determines that the i-th switch having the smallest distance difference has failed. The determination result is displayed on the screen through the display unit 35.

7 is a flowchart illustrating a multi-stage switch fault diagnosis method of a multilevel inverter according to an exemplary embodiment of the present invention.

delete

Referring to FIG. 7, the control unit 33 performs a DQ conversion on an AC current waveform output when the multi-stage switches of the inverter (INV) 20 are sequentially shorted, respectively, and the horizontal axis with respect to the horizontal axis and the vertical axis at the center point of the converted DQ. The average value and the vertical axis average value are calculated (S701). This is obtained by the above equation (8).

)를 생성한다(S703). 이는 상기 수학식 9를 통해 얻어진다.Subsequently, the controller 33 obtains a distance vector of each point from the center point of the DQ using the obtained horizontal and vertical mean values, and obtains a feature vector (

) Is generated (S703). This is obtained through equation (9).

)를 코드북화하여 데이터베이스화한다(S705).The control unit 33 generates the generated feature vector (

) Is codebooked into a database (S705).

Thereafter, the controller 33 converts the fault diagnosis current waveform output in real time from the inverter INV 20 into a fault feature vector (S707). The fault feature vector is obtained by applying the equations (8) and (9).

The control unit 33 calculates the distance error (difference) between the fault feature vector and the feature vector of the feature vector codebook as many as the number of database feature vectors (S709). At this time, the calculation formula for the distance error uses the above equation (10).

Thus, the controller 33 obtains a feature vector having the smallest distance error (S711), and determines that the specific switch corresponding to the acquired feature vector is a failure (S713).

After that, the control unit 33 indicates that the specific switch determined as the failure is notified (S715).

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by the equivalents of the claims.

1 is a block diagram of a multi-stage switch failure diagnosis apparatus of a multilevel inverter according to an embodiment of the present invention.

2 is an internal configuration diagram of an inverter in FIG. 1.

3 is an exemplary diagram showing an output current waveform of the inverter in FIG.

4 is a waveform diagram showing DQ conversion of the output current waveform of FIG. 3; FIG.

delete

delete

7 is a flowchart illustrating a multi-stage switch fault diagnosis method of a multilevel inverter according to an exemplary embodiment of the present invention.

Claims (9)

A device for diagnosing a failure of a multi-stage switch provided in a multilevel inverter that outputs three-phase AC power to drive a motor, Code-book the feature vector (reference feature vector) at the time of failure of each switch from the AC current waveform outputted by sequentially shorting the switches constituting the multi-stage switch, and then fail the fault diagnosis current waveform output from the inverter in real time. A control unit converting the feature vector into a feature vector and determining a switch corresponding to a codebooked feature vector having a minimum distance error between the feature vector and the fault feature vector as a fault switch; And Short-circuit state of each switch by feature vector extraction algorithm and feature vector extraction algorithm extracting feature vectors from current waveforms at each switch failure to determine whether a particular switch has failed according to the state of the multi-stage switch of the inverter Multi-stage inverter failure diagnosis apparatus, characterized in that it comprises a memory that is stored in the code feature of the star feature vector. delete The method of claim 1, wherein the control unit, After converting the output AC current waveform by DQ, the average value of the horizontal and vertical axes is calculated using Equation 1 below, and the average value of the calculated horizontal and vertical axes is applied to Equation 2 below. (

Multi-stage switch fault diagnosis apparatus, characterized in that the codebook. (Equation 1)

(Equation 2)

here,

Is the mean value of the horizontal axis,

Means the average value of vertical axis, i = number of switches, j = number of samples. The method of claim 3, wherein the control unit, And a distance error between the feature vector and the fault feature vector is calculated using Equation 3 below. (Equation 3)

Where P _{i, j} means a fault feature vector, i.e. a specific vector of the system in which there is a fault possibility to be checked, d _{i, j} means a feature vector, and M indicates the number of switches. delete In the method for diagnosing the failure of a multi-stage switch provided in a multilevel inverter for outputting three-phase AC power to drive a motor, A step of codebooking a feature vector (reference feature vector) at the time of failure for each switch from an AC current waveform outputted by sequentially shorting the switches constituting the multi-stage switch and making a database; And Converting a fault diagnosis current waveform output from the inverter in real time into a fault feature vector, and determining a switch corresponding to a codebooked feature vector having a minimum distance error between the feature vector and the fault feature vector as a fault switch. Multi-stage switch failure diagnosis method for a multi-level inverter comprising a. The method of claim 6, wherein the database process is performed. After the DQ conversion of the AC current waveform, the average value of the horizontal axis and the vertical axis is calculated using Equation 4 below, and the feature vector obtained by applying the average value of the calculated horizontal axis and the vertical axis to Equation 5 below (

Multi-stage switch fault diagnosis method for a multilevel inverter, characterized in that the codebook. (Equation 4)

(5)

here,

Is the mean value of the horizontal axis,

Means the average value of vertical axis, i = number of switches, j = number of samples. The method of claim 6, wherein the distance error, Multi-stage switch fault diagnosis method of the multi-level inverter, characterized in that the calculation using the following equation (6). (6)

Where P _{i, j} means a fault feature vector, i.e. a specific vector of the system in which there is a fault possibility to be checked, d _{i, j} means a feature vector, and M indicates the number of switches. delete

Images