JP2011055590A - Power converter and method of detecting abnormality in power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of detecting an abnormality in a power converter, with which an abnormality in the power converter due to functional deterioration of circuit parts such as a switching element, etc. can be detected. <P>SOLUTION: The U-phase current, V-phase current, and W-phase current of a three-phase AC power outputted from an inverter circuit 13 to a three-phase induction motor 16 are measured by ammeters 17, 18, and 19, and the U-phase current waveform distortion factor, V-phase current waveform distortion factor, and W-phase current waveform distortion factor of the three-phase AC power are obtained from each output of the ammeters 17-19; then the U-phase current waveform distortion factor, V-phase current waveform distortion factor, and W-phase current waveform distortion factor are compared with predetermined reference values; and in case that any of the current waveform distortion factors has a value larger than the reference value, it is determined that there is an abnormal state and abnormality in a power converter 10 is detected. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technique for detecting an abnormality in a power converter that supplies three-phase AC power to a load such as an induction motor.

  As a power conversion device for supplying three-phase AC power to an induction motor, the one shown in FIG. 5 is conventionally known. This power conversion device converts a three-phase AC power supplied from an AC power supply via input terminals R, S, and T into a DC power and outputs the DC power output from the converter circuit 11. Smoothing capacitor 12 for smoothing, inverter circuit 13 for converting the DC power smoothed by smoothing capacitor 12 into three-phase AC power and outputting it to three-phase induction motor 16, and inverter control circuit 15 for controlling this inverter circuit 13 The inverter circuit 13 includes switching elements 14a, 14b, 14c, 14d, 14e, and 14f such as IGBTs (insulated gate bipolar transistors) that are switched by a PWM (pulse width modulation) signal from the inverter control circuit 15. Have.

  Such a power conversion device cannot normally drive a three-phase induction motor if a loss of function such as a short-circuit failure or an open failure occurs in a switching element of an inverter circuit. As a technique for detecting an abnormality, the switching elements are sequentially switched according to a plurality of predetermined combination patterns. At this time, the abnormality of the power converter is determined based on the change in the three-phase alternating current supplied from the inverter circuit to the induction motor. There is known a method of detecting (see, for example, Patent Document 1).

  According to the method disclosed in Patent Document 1, there is an advantage that it is possible to determine whether an abnormality that has occurred in the switching element of the inverter circuit is a short-circuit breakdown or an open breakdown and to identify the switching element in which the abnormality has occurred. Even when an abnormality occurs in the inverter control circuit that outputs a PWM signal to the inverter circuit, there is a possibility that it is erroneously determined as an abnormality in the inverter circuit, and there is a problem that the location where the abnormality occurs cannot be specified accurately.

  Therefore, the PWM signal output from the inverter control circuit to the inverter circuit is monitored by the monitor circuit, and the U-phase current, the V-phase current, and the W-phase current of the three-phase AC power supplied from the inverter circuit to the induction motor are respectively currents. Patent Document 2 discloses a technique for detecting an abnormality of a power converter based on a PWM signal detected by a sensor and monitored by a monitor circuit and each phase current detected by a current sensor.

JP-A-8-308244 JP 2005-218181 A

  According to the technique disclosed in Patent Document 2, it is possible to specify whether an abnormality occurrence location is an inverter main circuit or an inverter control circuit. However, in the technology disclosed in Patent Document 2, the presence of abnormality is determined by comparing the waveform of the three-phase alternating current supplied from the inverter circuit to the induction motor with the waveform of the ideal current. However, if the function of the circuit component is lost, an abnormality of the power converter can be detected, but the cause of the abnormality is due to the deterioration of the function of the circuit component, such as a decrease in the insulation characteristics of the switching element or a decrease in the capacitance of the capacitor for generating the PWM signal. In some cases, it is difficult to detect abnormality of the power converter.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide an abnormality detection method for a power conversion device that can detect an abnormality of the power conversion device due to a function deterioration of a circuit component such as a switching element. Is. Another object of the present invention is to provide a power converter that can detect an abnormality in an inverter circuit or an inverter control circuit due to a deterioration in the function of circuit components such as switching elements.

  In order to solve the above-mentioned problem, the abnormality detection method for a power converter according to the first invention is a method for detecting an abnormality of a power converter having an inverter circuit that converts DC power into three-phase AC power and outputs the same. The U-phase current, V-phase current and W-phase current of the three-phase AC power output from the inverter circuit are measured, and the U-phase current, the V-phase current and the W-phase current are measured from the measured values. After obtaining the U-phase current waveform distortion, the V-phase current waveform distortion, and the W-phase current waveform distortion of the three-phase AC power, the U-phase current waveform distortion, the V-phase current waveform distortion, and the W-phase current are calculated. The waveform distortion rate is compared with a predetermined reference value, and an abnormality occurs when any of the U-phase current waveform distortion rate, the V-phase current waveform distortion rate, and the W-phase current waveform distortion rate is larger than the reference value. It is determined that there is an abnormality and the abnormality of the power conversion device is detected. It is intended.

  In the abnormality detection method for the power converter according to the first aspect of the invention, the U-phase current, V-phase current and W-phase current of the three-phase AC power output from the inverter circuit are calculated by using the CT (instrument current transformer). Can be measured with an ammeter. In this case, the U-phase current waveform distortion rate, the V-phase current waveform distortion rate, and the W-phase current waveform distortion rate of the three-phase AC power are obtained by fast Fourier transforming each output of the ammeter, It can be obtained by frequency analysis of the fundamental wave component and the harmonic wave component.

  A power converter according to a second aspect of the invention is an inverter circuit that converts DC power into three-phase AC power and outputs the inverter circuit, an inverter control circuit that controls the inverter circuit, and three-phase AC power output from the inverter circuit A first ammeter that measures the U-phase current of the second current meter, a second ammeter that measures the V-phase current of the three-phase AC power output from the inverter circuit, and the three-phase AC power output from the inverter circuit A power converter comprising: a third ammeter that measures a W-phase current of the current; and an abnormality detection device that detects an abnormality of the inverter circuit or the inverter control circuit, wherein the abnormality detection device is the first The U-phase current waveform distortion rate, the V-phase current waveform distortion rate, and the W-phase current waveform distortion rate of the three-phase AC power are obtained from the outputs of the current meter, the second ammeter, and the third ammeter. Predefined criteria In comparison with the above, it is determined that there is an abnormality when any one of the U-phase current waveform distortion rate, the V-phase current waveform distortion rate, and the W-phase current waveform distortion rate is larger than the reference value. Is.

  According to a second aspect of the present invention, there is provided an abnormality detection device for a power converter, wherein the outputs of the first ammeter, the second ammeter, and the third ammeter are subjected to a fast Fourier transform to obtain the three-phase AC power. The U-phase current waveform distortion rate, the V-phase current waveform distortion rate, and the W-phase current waveform distortion rate may be obtained. According to a second aspect of the present invention, there is provided a converter circuit for converting a three-phase AC power supplied from an AC power source into a DC power and outputting the DC circuit, and a smoothing capacitor for smoothing the DC power output from the converter circuit. The inverter circuit may convert DC power smoothed by the smoothing capacitor into three-phase AC power.

According to the first aspect of the present invention, any of the U-phase current waveform distortion rate, the V-phase current waveform distortion rate, and the W-phase current waveform distortion rate is generated when the functional degradation occurs in the circuit components such as the switching element and the PWM signal generating capacitor. Since the value becomes larger than the reference value, it is possible to detect an abnormality of the power conversion device due to the deterioration of the function of the circuit component.
According to the second aspect of the present invention, any of the U-phase current waveform distortion rate, the V-phase current waveform distortion rate, and the W-phase current waveform distortion rate is generated when the functional degradation occurs in the circuit components such as the switching element and the PWM signal generating capacitor. Since the value becomes larger than the reference value, it is possible to detect an abnormality of the inverter circuit or the inverter control circuit due to the deterioration of the function of the circuit component.

It is a figure which shows schematic structure of the power converter device which concerns on one Embodiment of this invention. It is a figure which shows schematic structure of the abnormality detection apparatus shown in FIG. It is a figure which shows an example of the current waveform of the three-phase alternating current power output from an inverter circuit, when the function deterioration has not arisen in the circuit component of an inverter control circuit. It is a figure which shows an example of the current waveform of the three-phase alternating current power output from an inverter circuit, when the function degradation has arisen in the circuit component of the inverter control circuit. It is a figure which shows an example of a power converter device.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
1 to 4 are diagrams for explaining an embodiment of the present invention. A power converter 10 shown in FIG. 1 includes a converter circuit 11, a smoothing capacitor 12, an inverter circuit 13, and a variable voltage variable frequency inverter control circuit 15. , A first ammeter 17, a second ammeter 18, a third ammeter 19 and an abnormality detection device 20.

The converter circuit 11 converts three-phase AC power supplied from an AC power source via input terminals R, S, and T into DC power and outputs the DC power. The DC power output from the converter circuit 11 is smoothed. It is smoothed by the capacitor 12.
The inverter circuit 13 converts the DC power smoothed by the smoothing capacitor 12 into three-phase AC power and outputs it to the three-phase induction motor 16 as a load. The inverter circuit 13 receives PWM (pulse width modulation) from the inverter control circuit 15. It has switching elements 14a, 14b, 14c, 14d, 14e, and 14f such as IGBTs (insulated gate bipolar transistors) that perform switching operations according to signals. Among these switching elements 14 a to 14 f, the collectors of the switching elements 14 a, 14 c and 14 e are connected to the positive bus 131 of the inverter circuit 13. The emitters of the switching elements 14a, 14c, and 14e are connected to the collectors of the switching elements 14b, 14d, and 14f, and the emitters of the switching elements 14b, 14d, and 14f are connected to the negative electrode bus 132 of the inverter circuit 13.

  The inverter circuit 13 also has output terminals U, V, and W that output three-phase AC power. Among these output terminals U, V, and W, the output terminal U is connected to a connection point between the emitter of the switching element 14a and the collector of the switching element 14b, and the output terminal V is connected to the emitter of the switching element 14c and the collector of the switching element 14d. Connected to the connection point. The output terminal W is connected to a connection point between the emitter of the switching element 14e and the collector of the switching element 14f.

The inverter control circuit 15 controls the inverter circuit 13 to adjust the voltage and frequency of the three-phase AC power output from the inverter circuit 13, and although not shown, a PWM signal for generating a PWM signal It has an electronic circuit for generation.
The first ammeter 17, the second ammeter 18, and the third ammeter 19 are U-phase current, V-phase current, and W-phase current of the three-phase AC power output from the inverter circuit 13 to the three-phase induction motor 16. These ammeters 17 to 19 are each connected to each phase via a CT (instrument current transformer).

The abnormality detection device 20 detects an abnormality of the inverter circuit 13 and the inverter control circuit 15 based on each phase current of the three-phase AC power measured by the ammeters 17 to 19, and the abnormality detection device 20 For example, as shown in FIG. 2, it is configured to include FFT circuits 21, 22, 23, distortion calculation circuits 24, 25, 26 and a comparison determination circuit 27.
The FFT circuit 21 performs fast Fourier transform on the output of the ammeter 17, and converts the U-phase current of the three-phase AC power output from the inverter circuit 13 to the three-phase induction motor 16 into a fundamental wave component Iu ₀ and harmonic components of each order. The frequency analysis is performed on Iu (n), and the fundamental component Iu ₀ and the harmonic component Iu (n) of the U-phase current obtained by the FFT circuit 21 are supplied to the distortion calculation circuit 24. It has become.

The FFT circuit 22 performs fast Fourier transform on the output of the ammeter 18, and converts the V-phase current of the three-phase AC power output from the inverter circuit 13 to the three-phase induction motor 16 into the fundamental wave component Iv ₀ and the harmonic components of the respective orders. The frequency analysis is performed on Iv (n), and the fundamental wave component Iv ₀ and the harmonic wave component Iv (n) of the V-phase current obtained by the FFT circuit 22 are supplied to the distortion calculation circuit 25. It has become.

FFT circuit 23 and the fast Fourier transform output of the ammeter 19, the three-phase AC power of W-phase current output from the inverter circuit 13 to a three-phase induction motor 16 and the fundamental wave component Iw ₀ harmonic components of each order Iw (n) is subjected to frequency analysis, and the fundamental wave component Iw ₀ and the harmonic component Iw (n) of the W-phase current obtained by the FFT circuit 23 are supplied to the distortion calculation circuit 26. It has become.

  The distortion calculation circuit 24 calculates the U-phase current waveform distortion ratio Du of the three-phase AC power output from the inverter circuit 13 to the three-phase induction motor 16 from the following equation (1). The U-phase current waveform distortion rate Du calculated in 24 is supplied to the comparison determination circuit 27.

   The distortion calculation circuit 25 calculates the V-phase current waveform distortion ratio Dv of the three-phase AC power output from the inverter circuit 13 to the three-phase induction motor 16 from the following equation (2). The V-phase current waveform distortion rate Dv calculated in 25 is supplied to the comparison determination circuit 27.

  The distortion calculation circuit 26 calculates the W-phase current waveform distortion ratio Dw of the three-phase AC power output from the inverter circuit 13 to the three-phase induction motor 16 from the following equation (3). The W-phase current waveform distortion rate Dw calculated at 26 is supplied to the comparison determination circuit 27.

  The comparison / determination circuit 27 determines the presence / absence of an abnormality by comparing the waveform distortion ratios Du, Dv, Dw calculated by the distortion calculation circuits 24-26 with predetermined reference values. Compares the waveform distortion rates Du, Dv, Dw calculated by the distortion calculation circuits 24-26 with a predetermined reference value, and when any of the waveform distortion rates Du, Dv, Dw is larger than the reference value. It is configured to determine that there is an abnormality.

FIG. 3 shows an example of the current waveform of the three-phase AC power output from the inverter circuit 13 when the circuit component of the inverter control circuit 15 is not deteriorated due to deterioration or the like. FIG. 4 shows an example of the current waveform of the three-phase AC power output from the inverter circuit 13 when the function deterioration due to the above occurs.
As shown in FIG. 3, when there is no functional degradation in the circuit components of the inverter control circuit 15, the current waveform of the three-phase AC power becomes a sine waveform without distortion, and the U-phase current waveform distortion rate Du at this time is the reference. It can be seen that the value is smaller than the value (in this case, 10.0%). On the other hand, when the function deterioration occurs in the circuit components of the inverter control circuit 15, as shown in FIG. 4, the current waveform of the three-phase AC power becomes a distorted waveform, and the U-phase current waveform distortion rate at this time It can be seen that Du is larger than the reference value.

  Therefore, as in the embodiment of the present invention described above, the U-phase current, the V-phase current, and the W-phase current of the three-phase AC power output from the inverter circuit 13 to the three-phase induction motor 16 are measured and measured. After obtaining the U-phase current waveform distortion rate Du, V-phase current waveform distortion rate Dv and W-phase current waveform distortion rate Dw of the three-phase AC power from the phase current, the U-phase current waveform distortion rate Du and the V-phase current waveform distortion rate By comparing the Dv and the W-phase current waveform distortion rate Dw with a predetermined reference value, when a functional deterioration occurs in circuit components such as switching elements, the U-phase current waveform distortion rate Du and the V-phase current waveform distortion rate Dv Since either of the W-phase current waveform distortion rate Dw is larger than the reference value, it is possible to detect an abnormality of the power conversion device 10 due to the deterioration of the function of the circuit component.

  In the above-described embodiment of the present invention, the U-phase current, the V-phase current, and the W-phase current of the three-phase AC power output from the inverter circuit 13 to the three-phase induction motor 16 are obtained by the ammeters 17, 18, and 19. Measure and output each of the ammeters 17 to 19 by fast Fourier transform to obtain the U-phase current waveform distortion rate Du, V-phase current waveform distortion rate Dv, and W-phase current waveform distortion rate Dw of the three-phase AC power. However, a fundamental wave component and a harmonic component of each phase current are extracted from each output of the ammeters 17 to 19 by a band pass filter, and the U-phase current waveform distortion factor Du and the V-phase current waveform distortion factor of the three-phase AC power are obtained. Dv and W phase current waveform distortion rate Dw may be obtained.

  DESCRIPTION OF SYMBOLS 10 ... Power converter, 11 ... Converter circuit, 12 ... Smoothing capacitor, 13 ... Inverter circuit, 14a, 14b, 14c, 14d, 14e, 14f ... Switching element, 15 ... Inverter control circuit, 16 ... Three-phase induction motor, 17 , 18, 19 ... ammeter, 20 ... abnormality detection circuit, 21, 22, 23 ... FFT circuit, 24, 25, 26 ... distortion rate calculation circuit, 27 ... comparison judgment circuit.

Claims (6)

  A method for detecting an abnormality in a power converter having an inverter circuit that converts DC power into three-phase AC power and outputs the U-phase current, V-phase current of the three-phase AC power output from the inverter circuit, and The W-phase current is measured, and the U-phase current waveform distortion, the V-phase current waveform distortion, and the W-phase current waveform of the three-phase AC power are determined from the measured values of the U-phase current, the V-phase current, and the W-phase current. After obtaining the distortion rate, the U phase current waveform distortion rate, the V phase current waveform distortion rate, and the W phase current waveform distortion rate are compared with a predetermined reference value, and the U phase current waveform distortion rate, the V An abnormality of the power converter is detected by determining that there is an abnormality when any one of a phase current waveform distortion factor and the W-phase current waveform distortion factor is larger than the reference value. Anomaly detection method.   The abnormality detection method for a power converter according to claim 1, wherein the U-phase current, the V-phase current, and the W-phase current of the three-phase AC power output from the inverter circuit are measured by three ammeters.   3. The U-phase current waveform distortion rate, the V-phase current waveform distortion rate, and the W-phase current waveform distortion rate of the three-phase AC power are obtained by performing a fast Fourier transform on each output of the ammeter. An abnormality detection method for a power converter.   An inverter circuit that converts DC power into three-phase AC power and outputs it, an inverter control circuit that controls the inverter circuit, and a first current that measures the U-phase current of the three-phase AC power output from the inverter circuit A second current meter that measures the V-phase current of the three-phase AC power output from the inverter circuit, and a third current that measures the W-phase current of the three-phase AC power output from the inverter circuit A power converter comprising: a meter; and an abnormality detection device that detects an abnormality of the inverter circuit or the inverter control circuit, wherein the abnormality detection device includes the first ammeter and the second ammeter. And the U-phase current waveform distortion rate, the V-phase current waveform distortion rate and the W-phase current waveform distortion rate of the three-phase AC power from the respective outputs of the third ammeter and compared with predetermined reference values, U phase current waveform distortion The power conversion apparatus characterized by any of the V-phase current waveform distortion factor and the W-phase current waveform distortion factor is determined that there is abnormality when the reference value is greater than value.   The abnormality detection device performs fast Fourier transform on outputs of the first ammeter, the second ammeter, and the third ammeter to perform U-phase current waveform distortion rate of the three-phase AC power, V-phase The power converter according to claim 4, wherein a current waveform distortion factor and a W-phase current waveform distortion factor are obtained.   6. The power converter according to claim 4 or 5, wherein a converter circuit that converts three-phase AC power supplied from an AC power source into DC power and outputs, and a smoothing capacitor that smoothes the DC power output from the converter circuit. Further, the inverter circuit converts the DC power smoothed by the smoothing capacitor into three-phase AC power.

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