JP2007025740A - Power supply abnormality detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily detect a phase interruption or phase order without preliminarily retaining information based on magnitude relation of voltage value of each of three phases in normal power supply, and enable operation even with a wrong phase order. <P>SOLUTION: This detector comprises an input voltage detection means 100, a three-phase/two-phase conversion means 101 converting input voltage on a statistic coordinate, an instantaneous angle arithmetic means 102 computing an instantaneous angle of input voltage, an instantaneous angle inclination arithmetic means 103, an average value arithmetic means 104 for inclination of instantaneous angle, an instantaneous angle sudden change detection means 105, an angle sudden change frequency detection means 106 detecting the frequency of instantaneous angle sudden change in a set period, and a phase interruption detection means 107 detecting phase interruption of AC power voltage based on outputs of the arithmetic means 104 and the detection means 106. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power supply abnormality detection device for protecting a power converter by detecting an abnormality such as an open phase of an AC power supply voltage supplied to a power converter or a change in phase order.

  As a kind of power converter, a direct converter that directly converts an AC power supply voltage into an AC voltage having an arbitrary magnitude and frequency without using a large energy buffer is known. This direct converter has features such as long life, space saving, power regeneration, and control of input current, so that input current harmonics can be suppressed.

This type of direct converter includes a matrix converter in which a power source and a load are directly connected via a bidirectional switch capable of flowing a current in both directions, and a PWM rectifier and an inverter without a capacitor in the DC intermediate section. There is a circuit that combines these.
As described above, since the direct converter does not have a large energy buffer, when an abnormality occurs in the power supply, the effect immediately appears on the output side.

Here, as an abnormality of the power supply, for example, there is an open phase in which one line on the input side of the direct converter is opened. When an open phase occurs, the voltage of that phase cannot be applied to the load, and the input current does not flow, so the output voltage and input current of the direct converter are greatly distorted. Therefore, it is necessary to stop the operation of the direct converter when phase loss occurs.
In addition, when an input current command for a direct converter is generated by a PLL (Phased Locked Loop) and an oscillator, if the phase order is changed due to a power line connection error or the like (for example, 120 degrees in the order of R phase, S phase, and T phase). When the phase sequence is switched, such as R phase, T phase, and S phase, to the normal state where the phase is shifted by 1), the input current command and the input voltage are different from each other, so the input current is abnormal. An electric current may be generated, which may destroy the switching element or the load device.

In order to solve such a problem, Patent Document 1 discloses a conventional technique for detecting a power supply abnormality such as a phase loss or a phase order change.
FIG. 6 is a block diagram showing the main part of this prior art, and the input / output shows a general three-phase case. In FIG. 6, 1 is a three-phase AC power source, 2 is an input filter comprising a reactor and a capacitor, 3 is an AC direct converter, and 4 is a load.

Although not shown, the power supply abnormality detection means 50 is composed of a power supply voltage information generation circuit, an abnormality detection signal generation circuit, and a determination circuit.
The power supply voltage information generation circuit detects information corresponding to the magnitude relationship of the voltage values of the R, S, and T phases of the three-phase AC power supply 1 to detect power supply voltage information signals R _max , R _min , S _max , S _min. , T _max , T _min are output. Here, R _max is a signal that is at a “High” level when the R phase is maximum, and is at a “Low” level in other sections, and the same applies to other signals. Since one cycle of the power supply is 360 degrees, the signals R _max , S _max , and T _max are each set to “High” level by 120 degrees, and so are R _min , S _min , and T _min .

The abnormality detection signal generation circuit holds in advance information based on the magnitude relationship between the voltage values of the R, S, and T phases when the power supply 1 is normal, and these information is stored in the abnormality detection signal R _max. ^* ~ Output as T _min ^* .
Further, in the above determination circuit, the power supply voltage information signal _R max _{through T min} and abnormality detection signal _R ^{max *} _{~T min} * and the comparing at predetermined time intervals, the power supply voltage if these signals are different The abnormal signal is output to the control signal creating means 201 in FIG.

The control signal creating unit 201 creates a control signal based on the input voltages v _r , v _s , and v _t detected by the input voltage detecting unit 100, and the PWM signal creating unit 200 creates a PWM signal from the control signal. Thus, the bidirectional switch of the AC direct converter 3 is configured to be switched.

JP 2001-258151 A (paragraphs [0020] to [0042], FIGS. 1 to 5 and the like)

  In the above-described prior art, in order to detect phase loss and determine the phase order, information based on the magnitude relationship of the voltage values of the R, S, and T phases when the three-phase AC power supply 1 is normal is detected as a power supply abnormality. Since the abnormality detection signal generation circuit in the means 50 needs to be held in advance, there is a problem that the circuit configuration becomes complicated and the cost of the control device increases. Further, it is necessary to output an abnormality detection signal held in advance in synchronization with the power supply voltage at the time of activation, and to compare it with the power supply voltage information signal, and these processes are also complicated. In addition, the operation method in the case where an error in the phase order is detected is not particularly disclosed.

Accordingly, the problem to be solved by the present invention is that it is possible to detect an open phase or a phase sequence of an AC power supply voltage without preliminarily holding information based on the magnitude relationship of each phase voltage value when the power supply is normal, and a power converter An object of the present invention is to provide a power supply abnormality detection device which can be protected.
It is another object of the present invention to provide a power supply abnormality detection device that enables operation of the power converter even when the phase sequence is incorrect.

In order to solve the above-mentioned problem, the invention described in claim 1 is a power supply abnormality detection device that detects an abnormality of an AC power supply voltage supplied to a power converter.
Input voltage detection means for detecting the input voltage of the power converter;
Three-phase / two-phase conversion means for converting the input voltage detected by the detection means onto a stationary coordinate;
First calculating means for calculating the instantaneous angle of the input voltage from the output of the converting means,
An abnormality of the power supply voltage is detected based on the output of the first calculating means.

The invention described in claim 2 is the invention according to claim 1,
Second computing means for computing the slope of the instantaneous angle from the output of the first computing means;
Third computing means for computing the average value of the slope of the instantaneous angle from the output of the second computing means;
An instantaneous angle sudden change detection means for detecting a sudden change in the instantaneous angle from the output of the first calculation means;
An angle sudden change number detection means for detecting the number of occurrences of an instantaneous angle sudden change in the set period from the output of the detection means, and
And an open phase detecting means for detecting an open phase of the AC power supply voltage based on the outputs of the third calculating means and the sudden angle change number detecting means.

The invention described in claim 3 is the invention according to claim 1,
Second computing means for computing the slope of the instantaneous angle from the output of the first computing means;
Phase sequence discriminating means for discriminating the phase sequence of the AC power supply voltage based on the output of the second computing means.

The invention described in claim 4 is, in claim 3,
A third computing means for computing the average value of the slope of the instantaneous angle from the output of the second computing means;
The phase sequence discriminating unit discriminates the phase sequence of the AC power supply voltage based on the output of the third computing unit.

According to the present invention, a phase failure is detected based on the instantaneous angle gradient of the input voltage of the power converter and its sudden change, and an error in phase sequence is detected based on the instantaneous angle gradient or its average value. Can do. Therefore, unlike the prior art, information based on the magnitude relationship between the phase voltage values when the power supply is normal is held in advance, or processing such as comparing these pieces of information with the power supply voltage information at a fixed period is unnecessary. It is possible to simplify the circuit configuration, control / arithmetic operation, and reduce the cost.
Furthermore, when a phase sequence error is detected according to the present invention, the power converter can be operated without any trouble by replacing the input current command of the power converter.

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 and corresponds to the invention described in claims 1 and 2. The same components as those in FIG. 6 are denoted by the same reference numerals, and the description thereof will be omitted. Hereinafter, different portions will be mainly described.

In FIG. 1, the power supply abnormality detection device according to the present embodiment includes an input voltage detection unit 100 that detects a three-phase input voltage from a three-phase AC power supply 1, and two-phase on a stationary coordinate for the detected input voltage of each phase. A three-phase / two-phase conversion means 101 for converting into components, and an instantaneous angle calculation means 102 as a first calculation means for calculating the instantaneous angle θ of the input voltage based on the output of the three-phase / two-phase conversion means 101; The instantaneous angle inclination calculating means 103 as the second calculating means for calculating the inclination of the instantaneous angle θ, the average value calculating means 104 as the third calculating means for calculating the average value of the inclination, and the instantaneous angle θ A sudden angle change detecting means 105 for detecting a sudden change, an angle sudden change number detecting means 106 for detecting the number of occurrences of this sudden angle change, and an average phase of the instantaneous angle θ and the number of sudden changes in the instantaneous angle θ are detected. Phase loss detection means 107.
The phase loss detection signal from the phase loss detection unit 107 is input to the control signal generation unit 201 together with the three-phase input voltage from the input voltage detection unit 100, and based on the control signal generated by the generation unit 201. The PWM signal creation means 200 is configured to create a PWM signal.

The operation of this embodiment will be described below.
First, the three-phase input voltage detection values v _r , v _s , and v _t output from the input voltage detection means 100 are converted into two-phase components on a stationary coordinate by the three-phase / two-phase conversion means 101 according to the following formula 1. _Are converted into voltages v _α and v _β .

  Next, the instantaneous angle θ of the input voltage is calculated according to Equation 2 by the instantaneous angle calculation means 102.

The instantaneous angle inclination calculation means 103 differentiates the instantaneous angle θ to obtain the inclination θ ′. The average value calculation means 104 is composed of a low-pass filter and a moving average calculation means, and can easily calculate the average value θ ′ _ave of the gradient θ ′.

Here, FIG. 2 is an example of a waveform when an open phase occurs in the R phase. Considering that the three-phase voltage detection value cannot detect the zero phase, that is, the total sum of the three-phase voltages is zero, v _r = 0 and v _s = −v _t after the occurrence of the open phase. v _α = 0, and v _β pulsates at the power supply frequency.
That is, from Equation 2, repeating the 90 and 270 degrees for each power half cycle depending on the polarity of the instantaneous angle θ is v _beta as shown in the middle of FIG. 2, changes 180 degrees.

Figure 3 shows the behavior of the power supply voltage vector v _i when the open-phase occurs in the R phase.
Since v _α = 0 and v _β pulsates at the power supply frequency, it can be seen from this vector diagram that the instantaneous angle θ repeats 90 degrees and 270 degrees in the power supply half cycle. Even when an open phase occurs in another phase, the instantaneous angle θ changes by 180 degrees every half cycle of the power source.
The sudden angle change detecting means 105 in FIG. 1 detects this change in the instantaneous angle θ, and the sudden angle change number detecting means 106 starts from the change (rise and fall) of the instantaneous angle θ in the middle stage of FIG. As shown, the number of sudden angle changes is detected over a set period.

Based on the output of the average value calculation means 104, the phase loss detection means 107 in FIG. 1 detects an abnormality in the inclination θ ′ when the average value θ ′ _ave of the inclination falls below a preset reference level, that is, the instantaneous angle θ Since a sudden change in the instantaneous angle θ occurs every half cycle of the power supply, if the angle sudden change more than the set number occurs during the set period based on the output of the angle sudden change number detection means 106, it will be lost. It is determined that a phase has occurred, and an open phase detection signal is output.
For example, when the average value θ ′ _ave of the inclination is below the reference level, an abnormality in the inclination θ ′ is detected, and if the number of sudden angle changes occurs two or more times in one power supply cycle, it is determined that a phase loss has occurred. The reference level, the setting period, and the set number of times may be set according to the situation.
The phase loss detection signal output from the phase loss detection unit 107 in this manner is sent to the control signal generation unit 201, and the operation of the AC direct converter 3 is stopped via the PWM signal generation unit 200.

  Next, FIG. 4 is a block diagram showing a second embodiment of the present invention, which corresponds to the invention described in claims 3 and 4. The same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. Hereinafter, different portions will be mainly described.

In FIG. 4, the phase order discriminating means 110 discriminates the polarity of the average value θ ′ _ave of the gradient of the instantaneous angle θ and detects a phase order error. Details are described below.
When the power supply voltage is normal, each phase voltage is expressed by Equation 3. However, V _r , V _s , and V _t are the amplitudes of the phase voltages.

When v _α and v _β are calculated by substituting Equation 3 into Equation 1, v _β is delayed by 90 degrees with respect to v _α as shown in FIG. At the same time, the instantaneous angle θ increases from 0 degrees. That is, the gradient θ ′ of the instantaneous angle θ is positive, and the average value θ ′ _{ave of the} gradient is also positive.
However, for example, when the S phase and the T phase are connected in reverse, the equation of the power supply voltage is expressed by Equation 4.

Substituting Equation 4 into Equation 1, v _β advances 90 degrees with respect to v _α . As a result, the instantaneous angle θ decreases from 360 degrees, that is, the inclination θ ′ becomes negative, and the average value θ ′ _{ave of the} inclination also becomes negative.

FIG. 5 is a waveform diagram of each part when the S phase and the T phase are connected in reverse.
4 outputs a “Low” level signal as a phase sequence determination signal when the phase sequence is normal and the polarity of the average value θ ′ _ave of the instantaneous angle θ is positive, for example. When the phase order is incorrect and the polarity of the average value θ ′ _ave is negative, a “High” level signal is output.

  The control signal generating unit 201 performs normal operation when the phase sequence determination signal is “Low” level, and returns the phase sequence to a normal state when the phase sequence is “High” level, The AC direct converter 3 can be operated by switching the S-phase and T-phase input current commands created by the PLL and the three-phase oscillator. Needless to say, a sequence that stops the operation when the phase sequence is incorrect may be adopted.

In this second embodiment, the phase order discriminating means 110 discriminates the phase order based on the average value θ ′ _ave of the gradient of the instantaneous angle θ, but the polarity of the gradient θ ′ of the instantaneous angle and the average value θ ′ _ave Therefore, the phase order may be determined based on the gradient θ ′ of the instantaneous angle.
Although the input voltage is detected on the power supply side of the input filter 2 in the first and second embodiments, it may be directly detected on the converter side.

  Moreover, the power supply abnormality detection device according to the present invention is not limited to the AC direct converter 3 as in each embodiment, but also to various power converters that convert AC power, including an inverter device having a rectifier and an inverter unit. Can be applied.

It is a block diagram which shows 1st Embodiment of this invention. It is a wave form diagram which shows the effect | action at the time of the R phase open phase in 1st Embodiment. It is a power supply voltage vector figure at the time of the R phase missing in 1st Embodiment. It is a block diagram which shows 2nd Embodiment of this invention. It is a wave form diagram of each part in case a phase order is wrong in 2nd Embodiment. It is a block diagram which shows a prior art.

Explanation of symbols

1: Three-phase AC power source 2: Input filter 3: AC direct converter 4: Load 100: Input voltage detection means 101: Three-phase / two-phase conversion means 102: Instantaneous angle calculation means 103: Instantaneous angle inclination calculation means 104: Average Value calculating means 105: sudden angle change detecting means 106: sudden angle change number detecting means 107: phase loss detecting means 110: phase order determining means 200: PWM signal creating means 201: control signal creating means

Claims (4)

In the power supply abnormality detection device that detects an abnormality in the AC power supply voltage supplied to the power converter,
Input voltage detection means for detecting the input voltage of the power converter;
Three-phase / two-phase conversion means for converting the input voltage detected by the detection means onto a stationary coordinate;
First computing means for computing the instantaneous angle of the input voltage from the output of the converting means;
With
A power supply abnormality detection device that detects an abnormality of a power supply voltage based on an output of a first calculation means. In the power failure detection device according to claim 1,
Second computing means for computing the slope of the instantaneous angle from the output of the first computing means;
Third computing means for computing the average value of the slope of the instantaneous angle from the output of the second computing means;
An instantaneous angle sudden change detection means for detecting a sudden change in the instantaneous angle from the output of the first calculation means;
An angle sudden change number detection means for detecting the number of occurrences of an instantaneous angle sudden change in the set period from the output of the detection means, and
An open phase detection means for detecting an open phase of the AC power supply voltage based on the outputs of the third calculation means and the sudden angle change number detection means;
A power supply abnormality detection device comprising: In the power failure detection device according to claim 1,
Second computing means for computing the slope of the instantaneous angle from the output of the first computing means;
Phase sequence determination means for determining the phase sequence of the AC power supply voltage based on the output of the second calculation means;
A power supply abnormality detection device comprising: In the power failure detection device according to claim 3,
A third computing means for computing the average value of the slope of the instantaneous angle from the output of the second computing means;
The phase abnormality determining unit determines the phase sequence of the AC power supply voltage based on the output of the third calculating unit.

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