JP4596251B2 - Phase loss detection device and AC-AC direct conversion device - Google Patents

Description

  The present invention relates to a phase loss detection device that detects a phase loss of a polyphase AC, and an AC-AC direct conversion device such as a matrix converter including the phase loss detection device.

  FIG. 6 shows a configuration of a conventional inverter device and its phase loss detection circuit disclosed in Patent Document 1, and shows an input / output in a general three-phase case. In FIG. 6, the input side is R, S, T phase, and the output side is U, V, W phase.

In FIG. 6, the rectifier 301 converts a three-phase AC voltage into a DC voltage, and this DC voltage is smoothed by a capacitor 303 in the DC link unit and supplied to the inverter 302.
The DC voltage detection means 401 takes in the instantaneous value of the DC voltage, and the voltage comparison means 402 constantly compares the instantaneous value of the DC voltage with the set value. The voltage comparison means 402 detects an open phase of the input voltage based on the comparison result of the DC voltage. The operation will be described below.

FIG. 7 is a waveform diagram of the DC voltage before and after smoothing by the capacitor 303 in FIG. 6, the dotted line indicates the DC voltage e _dc0 before smoothing, and the solid line indicates the DC voltage e _dc after smoothing. As shown in FIG. 7, the lower limit value (normal lower limit voltage e _nl1 ) of the DC voltage e _dc after smoothing does not decrease to the lower limit value e _nm1 of the DC voltage e _dc0 before smoothing. Has been reduced.

On the other hand, FIG. 8 is a waveform diagram showing the DC voltage before and after smoothing when the input voltage is lost. For example, when the S phase voltage is lost, the rectifier 301 rectifies each single phase voltage of the R phase and the T phase, so that the DC voltage pulsates at twice the power supply frequency. Therefore, since the lower limit value of the DC voltage e _dc after smoothing is lower than the normal lower limit voltage e _nl1, it is possible to detect the loss of phase by this value reaches the open phase detection lower limit voltage e _s.

As another conventional technique, there is a phase loss detection technique in the power conversion device described in Patent Document 2.
In this prior art, the output line voltage of the Δ-Y transformer connected to the output side of the inverter is input to a phase loss detection circuit via a voltage measuring device, and the absolute value of the line voltage is passed through a low-pass filter. The phase loss is detected by comparing with a threshold value.

JP-A-2004-56893 ([0007] to [0010], FIGS. 1 to 3 etc.) Japanese Unexamined Patent Publication No. 2004-88661 ([0005] to [0009], FIGS. 1 to 3 and the like)

When the prior art of Patent Document 1 is applied to an AC / AC direct converter as it is to detect an open phase, smoothing means such as a rectifier and a capacitor for converting an AC input voltage into a DC voltage, DC voltage detecting means It is necessary to newly add hardware such as voltage comparison means. However, the addition of these circuit components increases the size of the device and increases costs.
Furthermore, the prior art of Patent Document 2 also has a problem that the circuit configuration becomes complicated because an absolute value calculation circuit, a low-pass filter, a comparison circuit, and the like must be provided for each line voltage. Also, since a time corresponding to the time constant of the low-pass filter is required from the actual occurrence of phase loss to the detection of phase loss, if it is necessary to immediately stop the inverter operation at the time of phase loss, the stop action is delayed. As a result, the load may be adversely affected.
Accordingly, a problem to be solved by the present invention is to provide an open phase detection device capable of detecting a phase loss reliably and quickly at a low cost without increasing the number of circuit components and complication of the configuration, and the open phase detection device. Another object is to provide an AC-AC direct conversion device.

In order to solve the above-described problem, the phase loss detection device according to claim 1 includes power supply voltage detection means for detecting each phase voltage of the multiphase AC power supply,
Calculation means for calculating the magnitude of the power supply voltage vector from each phase voltage detected by the power supply voltage detection means,
Voltage drop detection means for detecting that the magnitude of the power supply voltage vector calculated by the calculation means has decreased below a set value;
Based on the output of the voltage drop detection means, the number of times the magnitude of the power supply voltage vector becomes lower than the set value, and means for detecting the elapsed time from the first lower than the set value,
The number of times within the elapsed time is obtained and a means for detecting the open phase of the multiphase AC power supply by having reached a predetermined value.

According to a second aspect of the present invention, there is provided an AC-AC direct conversion device including the open phase detection device according to the first aspect.

The AC-AC direct conversion device according to claim 3 is the AC-AC direct conversion device according to claim 2 , wherein the direct converter is operated using the phase loss detection signal output from the phase loss detection device. those having a means for stopping.

According to the present invention, in order to detect an open phase by calculation based on the magnitude of the power supply voltage vector, the circuit configuration is compared with the method of identifying the phase in which the open phase has occurred by individually comparing each phase voltage with a threshold value. This can be simplified, and the phase loss detection device can be realized at low cost.
For this reason, for example, when applied to an AC-AC direct conversion device, it is possible to quickly detect and protect open phases by simply adding or improving software of an existing control device without adding a rectifier or smoothing means. Operation becomes possible.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a first embodiment of the present invention, which corresponds to the embodiment of the phase loss detection device described in claim 1. In this embodiment, the phase loss detection device according to the present invention is applied to an AC-AC direct conversion device.

  In FIG. 1, 1 is a three-phase AC power source, 4 is an input filter comprising a reactor 41 and a capacitor 42, 3 is an AC-AC direct converter such as a matrix converter, and 2 is a load such as an AC motor. In the present specification, the whole including the power source 1, the input filter 4, the direct converter 3, and each means described below is referred to as an AC-AC direct conversion device.

Next, in the control device for the direct converter 3, reference numeral 200 denotes power supply voltage detection means, and 201 denotes the power supply voltages v _R , v _S , and v _T of the three-phase each phase based on Equation 1 based on the two-phase amount v _α. , V _β , and a magnitude calculation means for calculating the magnitude V _i of the power supply voltage vector from the two-phase quantities v _α , v _β by Equation 2.

Here, the behavior of the power supply voltage vector when the AC input voltage is lost is described.
For example, when an open phase occurs in the R phase, the R phase power supply voltage detection value is v _R = 0. Considering that the zero-phase component cannot be detected, that is, the sum of the three-phase voltage detection values is zero, v _S = −v _T. When these conditions are substituted into Equation 1, the two-phase amounts v _α and v _β of the power supply voltage are expressed by Equation 3.

  Substituting Equation 3 into Equation 2 yields Equation 4.

Now, assuming that the power supply voltage of each phase is a sine wave, the S-phase voltage v _S is expressed by Equation 5.

Substituting Equation 5 into Equation 4, the magnitude V _i of the power supply voltage vector, it can be seen that pulsates at twice the power supply frequency as illustrated in FIG.
The first embodiment pays attention to the above points, and the voltage drop detection means 202 in FIG. 1 is “H (High)” when the magnitude V _i of the power supply voltage vector falls below a predetermined set value. A level signal is output, and if it is above the set value, an "L (Low)" level signal is output. When phase failure occurs, the magnitude V _i of the power supply voltage vector so pulsates at twice the power supply frequency as described above, the level of the output signal of the voltage drop detection means 202 repeats the "H" and "L", The switching cycle of the level from “L” to “H” or “H” to “L” is half the power cycle. For this reason, the period _T1v of the voltage drop flag in FIG. 2 is 10 [ms] when the power supply frequency is 50 [Hz], and is approximately 8.3 [ms] when 60 [Hz].

  The voltage drop frequency detection means 203 provided on the output side of the voltage drop detection means 202 of FIG. "L") is calculated. In addition, the time measuring unit 204 measures the elapsed time after the level of the output signal of the voltage drop detecting unit 202 becomes “H” and the voltage drop is first detected within a certain set time.

FIG. 3 shows a simulation waveform when an open phase occurs in the present embodiment.
As shown in the drawing, when an open phase occurs in the R phase and the R phase voltage v _R disappears, a decrease in the magnitude of the power supply voltage vector is regularly detected as described above. For this reason, for example, when the power supply frequency is 50 [Hz], the number of times of voltage drop is 4 or 5 times (ie, by the voltage drop number detection means 203 within two cycles (40 [ms]) measured by the time measuring means 204 (that is, If the period of the voltage drop flag is 10 [ms] or less), the phase loss detection means 205 in FIG. 1 determines that there is a phase loss and outputs a phase loss detection signal (phase loss detection flag). In the example of FIG. 3, the phase loss is detected when the number of voltage drops is detected five times.

When the phase loss detection signal is output in this way, the PWM signal generating means 100 in FIG. 1 shuts off all the AC-AC direct converters 3 and stops its operation. The control signal creation means 101 creates and outputs a voltage command or the like for the PWM signal creation means 100, and the operation may be stopped by inputting an open phase detection signal to the control signal creation means 101.
If the number of voltage drops does not reach the set value within the set time in the time measuring means 204, it is determined that there is no phase loss and the normal operation is continued.
In the embodiment of FIG. 1, the power supply voltage is detected from the primary side of the input filter 4, but may be detected from the secondary side of the input filter 4.

Next, FIG. 4 is a block diagram showing a second embodiment of the present invention.
The description will focus on the differences from the first embodiment. In this embodiment, the average value calculation means 206 calculates the time average value V _iav of the magnitude V _i of the power supply voltage vector. This calculation can be realized by using, for example, a low-pass filter or obtaining a moving average. Since the magnitude V _i of the power supply voltage vectors by phase loss pulsates its time average value V _iav lowered, open phase detection means 205 for detecting the open phase with that the time average value V _iav are slower than the preset value . Subsequent operations are the same as those in the first embodiment.

FIG. 5 is a waveform diagram showing the calculation result of the magnitude V _i of the power supply voltage vector and the average value V _iav thereof. In this embodiment, it is determined that the phase is _missing when the average value V _iav is lower than the set value. Then, a phase loss detection signal (phase loss detection flag) is generated.
In this embodiment as well, the power supply voltage may be detected from the secondary side of the input filter 4.

As described above, according to the phase loss detection device according to each embodiment, phase loss can be detected by a simple calculation based on the magnitude of the power supply voltage vector, and the AC-AC direct conversion device is protected. Therefore, it is possible to reliably detect the phase loss not only for the multi-phase AC power supply but also for all.
In addition, since it is not a method of detecting an open phase based on the DC link voltage of the power converter, it can be applied to an AC-AC direct conversion device without adding hardware such as a rectifier and smoothing means, and its control By simply adding software to the device, the direct converter can be protected quickly in the event of a phase failure.

1 is a block diagram showing a first embodiment of the present invention. It is a wave form diagram which shows the operation | movement at the time of a phase loss in 1st Embodiment. It is a figure which shows the simulation waveform at the time of a phase loss in 1st Embodiment. It is a block diagram which shows 2nd Embodiment of this invention. It is a wave form diagram which shows the operation | movement at the time of a phase loss in 2nd Embodiment. It is a block diagram of a prior art. FIG. 7 is a waveform diagram of a DC voltage before and after smoothing in FIG. 6. FIG. 7 is a waveform diagram of a DC voltage at the time of phase loss in FIG. 6.

Explanation of symbols

1: Three-phase AC power supply 2: Load 3: AC-AC direct converter 4: Input filter 41: Reactor 42: Capacitor 100: PWM signal generating means 101: Control signal generating means 200: Power supply voltage detecting means 201: Power supply voltage vector Magnitude calculation means 202: Voltage drop detection means 203: Voltage drop count detection means 204: Time measurement means 205: Phase loss detection means 206: Average value calculation means

Claims (3)

Power supply voltage detection means for detecting each phase voltage of the multiphase AC power supply;
Calculation means for calculating the magnitude of the power supply voltage vector from each phase voltage detected by the power supply voltage detection means,
Voltage drop detection means for detecting that the magnitude of the power supply voltage vector calculated by the calculation means has decreased below a set value;
Based on the output of the voltage drop detection means, the number of times the magnitude of the power supply voltage vector becomes lower than the set value, and means for detecting the elapsed time from the first lower than the set value,
Means for detecting an open phase of the multiphase AC power supply when the number of times has reached a predetermined value within the elapsed time ;
Open-phase detecting apparatus characterized by comprising a. An AC-AC direct conversion device comprising the phase loss detection device according to claim 1 . In the AC-AC direct conversion device according to claim 2 ,
An AC-AC direct conversion device comprising means for stopping the operation of the direct converter using the phase loss detection signal output from the phase loss detection device.

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