JP2013093949A - Power conversion apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion apparatus in which abnormality of an AC filter circuit can be detected in simple configuration.SOLUTION: A control device 8 detects a harmonic component contained in a voltage VL detected by a voltage detection section 6 and, in the case where the detected harmonic component exceeds a preset value, detects abnormality of an AC filter circuit 4. The voltage detection section 6 is provided in a power conversion apparatus 1 for the control device 8 to control a conversion section 3. By utilizing the voltage detection section 6, abnormality of the AC filter circuit can be detected in simple configuration.

Description

  The present invention relates to a power converter, and more particularly to a technique for detecting an abnormality in an AC filter circuit included in the power converter.

  Generally, an AC filter circuit is provided on the output side of a power converter that converts DC power into AC power. This AC filter circuit is generally composed of a reactor (L) and a capacitor (C). When the power conversion device performs a switching operation, the DC power is converted into AC power. The AC filter circuit has a function of removing harmonic components contained in AC power output from the power converter.

  For example, Japanese Patent Laid-Open No. 8-331750 (Patent Document 1) discloses a power conversion device including an AC filter circuit. In this power converter, the instantaneous voltage waveform of the three-phase AC voltage output from the output transformer is detected by the transformer. The three-phase alternating current corresponding to the output waveform of the transformer is rectified by a rectifier, and the output of the rectifier is converted into a digital value by an A / D converter. When the state where the average value of the digital values is outside the predetermined level continues for a predetermined time or longer, a stop command is given to a PWM (pulse width modulation) pulse generation circuit. As a result, the PWM pulse generation circuit stops the drive of the inverter device even if the phase of the inverter device is lost.

  For example, Japanese Patent Laid-Open No. 63-245272 (Patent Document 2) discloses an inverter protection circuit. The protection circuit includes a voltage detector that detects an output voltage of the AC filter circuit, a notch filter circuit that detects a harmonic component included in the output voltage of the AC filter circuit, and a harmonic component detected by the notch filter circuit. Is converted to a DC voltage by an absolute value circuit and a smoothing circuit, and the DC voltage of this conversion circuit is compared with the set value of output voltage distortion rate abnormality protection. When the DC voltage exceeds the set value, the inverter And means for stopping.

  For example, Japanese Patent Laying-Open No. 2005-85088 (Patent Document 3) discloses a power conversion device including a DC-DC conversion device, an inverter device, an AC filter, and a control device. This control device generates a variable output voltage correction command value. The control device includes a voltage lowering unit that lowers the output voltage of the DC-DC converter at a light load.

JP-A-8-331750 JP 63-245272 A JP-A-2005-85088

  When a short-circuit between reactor windings or a capacity loss of a capacitor occurs, the AC filter circuit does not completely fail, but is in a halfway failure state. In such a case, a harmonic component may be generated in the output of the AC filter circuit. When a harmonic component is generated in the output of the AC filter circuit, there is a possibility that the reactor of the AC filter or the capacitor is overheated by the harmonic component current to the capacitor.

  In order to prevent such a problem, it is desirable that when a harmonic component is generated in the output of the AC filter circuit, the harmonic component can be detected. However, on the other hand, when the configuration for detecting an abnormality in the AC filter circuit becomes complicated, there is a concern that the cost of the power converter increases.

  An object of the present invention is to provide a power converter capable of detecting an abnormality of an AC filter circuit with a simple configuration.

  A power conversion device according to an aspect of the present invention includes a conversion unit that converts DC power into AC power and outputs AC power, an AC filter circuit connected to the output side of the conversion unit, a conversion unit, and an AC filter circuit A current detection unit that detects a current output from the conversion unit, a voltage detection unit that detects an AC voltage output from the AC filter circuit, and a current and voltage detection unit detected by the current detection unit And an abnormality detection unit that detects a harmonic component from at least one of the detected voltages and detects an abnormality of the AC filter circuit when the harmonic component exceeds a set value.

  ADVANTAGE OF THE INVENTION According to this invention, the power converter device which can detect abnormality of an alternating current filter circuit with a simple structure is realizable.

It is a schematic block diagram of the power converter device which concerns on embodiment of this invention. 2 is a functional block diagram illustrating a configuration of a control device according to Embodiment 1. FIG. FIG. 5 is a functional block diagram illustrating a configuration of a control device according to a second embodiment. FIG. 10 is a diagram showing a modification of the configuration of the control device according to the second embodiment. FIG. 6 is a functional block diagram illustrating a configuration of a control device according to a third embodiment. FIG. 6 is a functional block diagram illustrating a configuration of a control device according to a fourth embodiment. FIG. 10 is a diagram showing a first modification of the configuration of the control device according to the fourth embodiment. It is the figure which showed the 2nd modification of the structure of the control apparatus which concerns on Embodiment 4. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is a schematic configuration diagram of a power conversion device according to an embodiment of the present invention. Referring to FIG. 1, power conversion device 1 converts DC power into AC power and supplies the AC power to load 2. The power conversion device 1 includes a conversion unit 3, an AC filter circuit 4, current detection units 5 and 7, a voltage detection unit 6, and a control device 8. The AC filter circuit 4 includes a reactor 9 and a capacitor 10.

  The converter 3 converts DC power into AC power. The conversion unit 3 is realized by a known inverter circuit including a semiconductor switching element (not shown). The AC power output from the converter 3 may be a three-phase AC or a single-phase AC. The semiconductor switching element is turned on and off by a signal from the control device 8. As a control method of the semiconductor switching element, for example, a well-known PWM (pulse width modulation) method can be used.

  The AC filter circuit 4 is an LC filter circuit constituted by a reactor 9 and a capacitor 10. The AC filter circuit 4 has a function of removing harmonic components contained in the AC power output from the conversion unit 3.

  The current detection unit 5 detects the current IA output from the conversion unit 3 and outputs a signal indicating the detected current IA to the control device 8. The voltage detector 6 detects the voltage VL output from the AC filter circuit 4 and outputs a signal indicating the detected voltage VL to the control device 8. The current detection unit 7 detects the current IL output from the AC filter circuit 4 (supplied to the load 2), and outputs a signal indicating the detected current IL to the control device 8.

The control device 8 is a signal for controlling the converter 3 based on the current IA detected by the current detector 5, the voltage VL detected by the voltage detector 6, and the current IL detected by the current detector 7. And sends the signal to the conversion unit 3. This signal is a signal for turning on and off the semiconductor switching element included in the conversion unit 3. For example, control device 8 detects voltage VL and currents IA and IL, and turns on and off the semiconductor switching element by feedback control for bringing voltage VL closer to the voltage command value. To generate the voltage command value,
The control device 8 detects an abnormality in the AC filter circuit 4. That is, in the embodiment of the present invention, the abnormality detection unit is realized by the control device 8.

  When the abnormality of the AC filter circuit 4 is detected, the control device 8 outputs a signal for notifying that the abnormality of the AC filter circuit 4 has been detected. This signal is used as a signal for lighting a lamp for notifying the abnormality of the AC filter circuit 4, for example. However, the specific method of using the signal for notifying the abnormality of the AC filter circuit 4 is not particularly limited. Furthermore, when the control device 8 detects an abnormality in the AC filter circuit 4, the control device 8 may not only output a signal for notifying the abnormality but also stop the operation of the conversion unit 3.

  Next, a specific configuration of the control device 8 for detecting an abnormality in the AC filter circuit 4 will be described with reference to the drawings. Note that the configuration described below may be realized by hardware, or may be realized by software that operates the hardware (for example, a program that operates a microcomputer).

[Embodiment 1]
In the first embodiment, the control device 8 detects an abnormality in the AC filter circuit 4 based on the voltage VL detected by the voltage detection unit 6. Specifically, the control device 8 detects a harmonic component of the voltage VL detected by the voltage detection unit 6, and if the detected harmonic component is equal to or higher than a set value, the control device 8 detects an abnormality in the AC filter circuit 4. To detect.

  FIG. 2 is a functional block diagram illustrating a configuration of the control device according to the first embodiment. Referring to FIG. 2, control device 8 includes a high-pass filter (HPF) 11, an effective value calculation unit 12, a comparison circuit 13, and a confirmation time limit circuit 14.

  The high pass filter 11 extracts a harmonic component from the voltage VL. The cut-off frequency of the high-pass filter 11 is set to, for example, twice the output frequency of the power converter 1, that is, the frequency of the voltage VL. Therefore, a component having a frequency larger than twice the output frequency of power converter 1 (usually a component having an odd multiple of the output frequency of power converter 1) is extracted from voltage VL.

  The effective value calculation unit 12 receives the output of the high pass filter 11 and calculates the effective value of the harmonic component. For example, the effective value is calculated by the square root of the sum of squares.

  The comparison circuit 13 compares the effective value calculated by the effective value calculation unit 12 with a set value. This set value may be given to the control device 8 from the outside, or the control device 8 may hold it in advance. When the effective value is larger than the set value, the comparison circuit 13 outputs a signal. That the effective value is larger than the set value means that the harmonic component of the voltage VL is larger than the set value.

  The confirmation time limit circuit 14 is realized by a counter, for example, and counts the time for the comparison circuit 13 to output a signal. When the time for which the comparison circuit 13 outputs a signal exceeds a predetermined time, the confirmation time limit circuit 14 outputs a signal indicating that an abnormality of the AC filter circuit 4 has been detected. If the time for which the comparison circuit 13 outputs a signal reaches a predetermined time, there is a high possibility that the AC filter circuit 4 is abnormal. The confirmation time limit circuit 14 can correctly detect an abnormality in the AC filter circuit 4.

  As described above, according to the first embodiment, the control device 8 detects the harmonic component included in the voltage VL detected by the voltage detection unit 6, and the detected harmonic component exceeds the set value. An abnormality in the AC filter circuit 4 is detected. The voltage detection unit 6 is provided in the power conversion device 1 so that the control device 8 controls the conversion unit 3. By using this voltage detector 6, it is possible to detect an abnormality of the AC filter circuit with a simple configuration.

[Embodiment 2]
In the second embodiment, the control device 8 detects an abnormality of the AC filter circuit 4 based on the current IA detected by the current detection unit 5. Specifically, the control device 8 detects a harmonic component of the current IA detected by the current detection unit 5, and if the detected harmonic component is equal to or greater than a set value, the abnormality of the AC filter circuit 4 is detected. Is detected.

  FIG. 3 is a functional block diagram illustrating the configuration of the control device according to the second embodiment. Referring to FIG. 3, the control device 8 includes a high pass filter (HPF) 21, an effective value calculation unit 22, a comparison circuit 23, and a confirmation time limit circuit 24.

  As can be seen by comparing FIG. 2 and FIG. 3, the configuration of the control device according to the second embodiment is the same as the configuration of the control device according to the first embodiment. In the second embodiment, the high-pass filter 21 extracts a harmonic component from the current IA. The cut-off frequency of the high-pass filter 21 is set to, for example, twice the output frequency of the power converter 1, that is, the frequency of the voltage VL.

  The functions of the effective value calculation unit 22, the comparison circuit 23, and the confirmation time limit circuit 24 are the same as the functions of the effective value calculation unit 12, the comparison circuit 13, and the confirmation time limit circuit 14, respectively. The effective value calculator 22 calculates the effective value of the harmonic component of the current IA. The comparison circuit 23 compares the effective value calculated by the effective value calculation unit 22 with a set value. This set value may be given to the control device 8 from the outside, or the control device 8 may hold it in advance. When the effective value is larger than the set value, the comparison circuit 23 outputs a signal. That the effective value is larger than the set value means that the harmonic component of the current IA is larger than the set value.

  The confirmation time limit circuit 24 is realized by a counter, for example, and counts the time for which the comparison circuit 23 outputs a signal. When the time for which the comparison circuit 23 outputs a signal exceeds a predetermined time, the confirmation time limit circuit 24 outputs a signal indicating that an abnormality of the AC filter circuit 4 has been detected.

(Modification of Embodiment 2)
FIG. 4 is a diagram illustrating a modification of the configuration of the control device according to the second embodiment. Referring to FIGS. 3 and 4, in this modification, control device 8 includes a bandpass filter (BPF) 21 </ b> A instead of highpass filter 21. The remaining elements in the configuration shown in FIG. 4 are the same as the corresponding elements shown in FIG.

  By appropriately determining the passband of the bandpass filter 21A, a harmonic component having a specific frequency can be extracted from the current IA. The passband is not particularly limited, and is set such that, for example, the third harmonic, the fifth harmonic, or the seventh harmonic (these are examples) are extracted from the bandpass filter 21A.

  According to the second embodiment and its modification, it is possible to detect an abnormality of the AC filter circuit with a simple configuration as in the first embodiment.

  Furthermore, according to the second embodiment and the modification thereof, the harmonic component of the current (a harmonic component included in the current from the conversion unit) that is a factor that causes the reactor or the capacitor of the AC filter circuit 4 to be overheated directly. It can be detected. Therefore, the detection accuracy can be increased in detecting an abnormality of the AC filter circuit.

[Embodiment 3]
FIG. 5 is a functional block diagram showing the configuration of the control device according to the third embodiment. Referring to FIG. 5, control device 8 according to Embodiment 3 includes abnormality detection units 8 </ b> A and 8 </ b> B and an OR circuit 25.

  The configuration of the abnormality detection unit 8A is the same as the configuration of the control device (see FIG. 2) according to the first embodiment. The configuration of the abnormality detection unit 8B is the same as the configuration of the control device (see FIG. 3) according to the second embodiment. Therefore, detailed description regarding the configuration of abnormality detection units 8A and 8B will not be repeated hereinafter. The OR circuit 25 outputs a signal indicating abnormality detection when at least one of the confirmation timing circuits 14 and 24 outputs a signal. The configuration of the abnormality detection unit 8B can be replaced with the configuration shown in FIG.

  According to the third embodiment, an abnormality of the AC filter circuit can be detected with a simple configuration as in the first and second embodiments. Furthermore, according to the third embodiment, an abnormality of AC filter circuit 4 is detected when at least one of the harmonic component of voltage VL and the harmonic component of current IA exceeds a set value. Thereby, the probability that abnormality of the AC filter circuit 4 can be detected can be increased.

  Furthermore, according to the third embodiment, as in the second embodiment, the detection accuracy can be increased in the detection of an abnormality in the AC filter circuit.

[Embodiment 4]
In the fourth embodiment, the control device 8 detects an abnormality of the AC filter circuit 4 based on both the current IA detected by the current detection unit 5 and the current IL detected by the current detection unit 7. Specifically, the control device 8 generates a difference between the instantaneous value of the current IA and the instantaneous value of the current IL. This difference is called “deviation current”. The deviation current corresponds to the current flowing through the capacitor 10 of the AC filter circuit 4. When the value of the deviation current is greater than or equal to the set value, the control device 8 detects an abnormality in the AC filter circuit 4.

  FIG. 6 is a functional block diagram illustrating a configuration of a control device according to the fourth embodiment. With reference to FIG. 6, the control device 8 includes a subtraction unit 30, an effective value calculation unit 32, a comparison circuit 33, and a confirmation time limit circuit 34.

  The subtracting unit 30 subtracts the value of the current IL from the value of the current IA. The output of the subtracting unit 30 corresponds to the value of the deviation current. The effective value calculator 32 calculates an effective value of the deviation current. As in the first to third embodiments, the effective value is calculated by, for example, the square root of the sum of squares.

  The comparison circuit 33 compares the effective value calculated by the effective value calculation unit 32 with a set value. This set value may be given to the control device 8 from the outside, or the control device 8 may hold it in advance. When the effective value is larger than the set value, the comparison circuit 33 outputs a signal.

  The confirmation time limit circuit 34 is realized by a counter, for example, and counts the time during which the comparison circuit 33 outputs a signal. When the time for which the comparison circuit 33 outputs a signal exceeds a predetermined time, the confirmation time limit circuit 34 outputs a signal indicating that an abnormality of the AC filter circuit 4 has been detected.

(Modification of Embodiment 4)
FIG. 7 is a diagram illustrating a first modification of the configuration of the control device according to the fourth embodiment. 6 and 7, in this modification, a low-pass filter (LPF) 31 is added to the configuration shown in FIG. The low pass filter 31 is provided between the subtraction unit 30 and the effective value calculation unit 32.

  The low-pass filter 31 is provided to remove the influence of the negative overcurrent IL from the deviation current calculated by the subtracting unit 30. The cutoff frequency of the low-pass filter 31 is set to the frequency of the negative overcurrent IL, for example.

  FIG. 8 is a diagram illustrating a second modification of the configuration of the control device according to the fourth embodiment. 7 and 8, in this modification, in addition to the current IA detected by the current detection unit 5 and the current IL detected by the current detection unit 7, the subtraction unit 30 shown in FIG. The value of the current IC is input. The current IC is a calculated value of the current flowing through the capacitor 10. The subtraction unit 30 subtracts the value of the current IL and the value of the current IC from the value of the current IA, and outputs the subtraction result (IA-IL-IC).

  According to the fourth embodiment and its modification, it is possible to detect an abnormality of the AC filter circuit with a simple configuration as in the first embodiment.

  Moreover, the load 2 shown in FIG. 1 may be a rectifier load. According to the fourth embodiment and the modification thereof, it is possible to remove the influence of the harmonic component of the current IL (negative overcurrent) from the current IA by calculating the deviation current. Thus, according to the fourth embodiment and its modification, it is possible to detect an abnormality of the AC filter circuit more accurately than in the second embodiment.

  The configuration shown in FIG. 6, 7 or 8 can be applied to the abnormality detection unit 8B shown in FIG.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  DESCRIPTION OF SYMBOLS 1 Power converter device, 2 Loads, 3 Conversion part, 4 AC filter circuit, 5, 7 Current detection part, 6 Voltage detection part, 8 Control apparatus, 8A, 8B Abnormality detection part, 9 Reactor, 10 Capacitor, 11, 21 High pass Filter, 12, 22, 32 RMS value calculation unit, 13, 23, 33 comparison circuit, 14, 24, 34 confirmation time limit circuit, 21A band pass filter, 25 OR circuit, 30 subtraction unit, 31 low pass filter.

Claims (4)

A converter that converts DC power into AC power and outputs the AC power;
An AC filter circuit connected to the output side of the converter;
A first current detection unit provided between the conversion unit and the AC filter circuit to detect a current output from the conversion unit;
A voltage detection unit for detecting an AC voltage output from the AC filter circuit;
A harmonic component is detected from at least one of the current detected by the first current detection unit and the voltage detected by the voltage detection unit, and an abnormality of the AC filter circuit is detected when the harmonic component exceeds a set value. A power conversion device comprising an abnormality detection unit for detection.   The abnormality detection unit detects the harmonic component included in the voltage detected by the voltage detection unit, and detects an abnormality of the AC filter circuit when the harmonic component exceeds a set value. The power converter device described in 1.   The abnormality detection unit detects the harmonic component included in the current detected by the first current detection unit, and detects an abnormality of the AC filter circuit when the harmonic component exceeds a set value. The power converter according to claim 1 or 2. The power conversion device further includes a second current detection unit that is provided on an output side of the AC filter circuit and detects a current flowing from the AC filter circuit to a load,
The abnormality detection unit calculates a deviation current by subtracting an instantaneous value of the current detected by the second current detection unit from an instantaneous value of the current detected by the first current detection unit; The power converter according to claim 1, wherein an abnormality of the AC filter circuit is detected when a harmonic component of the AC exceeds a set value.

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