JPH07106068B2 - Power converter open-phase detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a power conversion device for exchanging electric power with an AC power supply, and particularly to a phase loss detection of a power conversion device for detecting a phase loss of a power supply as a protection means. Regarding the device.

[Conventional technology]

In a power conversion device that exchanges power with an AC power supply, it is necessary to constantly grasp the state of the power supply voltage, for example, the voltage, frequency, and phase, and perform control accordingly, so that appropriate detection can be performed even during a power failure or phase loss. And protective action is required. In particular, the occurrence of a power failure or a missing phase in the state of regenerating electric power to an AC power supply is extremely difficult for the operation of the device. Then, during regeneration of the device, some voltage appears in the power supply voltage despite the occurrence of a power failure or open phase, which makes it difficult to perform appropriate detection.

FIG. 3 shows a conventional example of the main configuration of an AC motor drive device having an open phase detection circuit. 1 is a three-phase AC power supply, 2 is an AC reactor, 3 is a converter unit, 4 is a DC smoothing unit,
Reference numeral 5 is an inverter unit, 6 is an AC motor, 7 is a phase detection circuit, 8 is a base amplifier, and 9 is an open phase detection circuit. Here, the converter unit 3 has a three-phase bridge connection configuration by the anti-parallel circuits 3a, 3b, 3c, 3d, 3e, 3f of transistors and diodes, and can perform forward conversion and inverse conversion operations. Each transistor of the anti-parallel circuit of the section 3 is driven. The phase detection circuit 7 is a simple example including a rectifier circuit including a photocoupler and a diode, a resistor 73, and phase detection units 74a to 74f.
The phase loss detection circuit 9 provides the output signal 9A to the base amplifier 8 to stop the operation of the base amplifier 8.

Here, the operation of the main circuit is well known and will not be described.

In the phase detection circuit 7, the diode 71 of the photo coupler
a, 71b, 71c, 71d, 71e, 71f are connected in series with diodes 72a, 72b, 72c, 72d, 72e, 72f having reverse blocking voltage, and they form a three-phase bridge rectifier circuit with a resistance in the rectifier circuit. 73 is connected and configured as a load resistor.

With this configuration, the phase voltages of the phases individually connected to the diodes 71a to 71f of the photocoupler are the highest or the lowest.
The current flows only in the 120 ° period and the phase detectors 74a, 74b, 74c, 7
Transistors 71a ', 71 of photocouplers in 4d, 74e, 74f
b ', 71c', 71d ', 71e', 71f 'are made conductive. Then, in the phase detectors 74a to 74f, waveforms are shaped by the operation of the transistors 71a 'to 71f' of the photocoupler, for example, by the resistor 741a and the inverter gate 741b, and the phase detection signal is obtained.
Generates 7A, 7B, 7C, 7D, 7E, 7F. Here, the phase detection signal 7
A to 7F correspond to signals having a phase angle of 180 ° and a conduction width of 120 ° for the transistors in the anti-parallel circuit of the converter unit 3, and these signals are passed through the base amplifier 8 to drive signals 8A, 8B,
Signals are sent as 7C, 8D, 8E, 8F. Next, the 4th
The open phase detection circuit will be described with reference to FIGS.

FIGS. 4 and 5 are shown for explaining the open phase detection circuit of FIG. 3, and the open phase detection circuit 9 includes a power supply voltage detecting transformer 91 and phase voltage detecting sections 92, 92 ', 92 ". And diode 9
3, 93 ', 93 ", a reference setter 94, and a comparator 95. Also, in Fig. 5, (a) shows three line voltages of the three-phase AC power supply 1, and (b) ), (C),
(D) is a rectifier circuit 921a in each phase voltage detector 92, for example.
Output voltage, comparator 921c output voltage, capacitor
The voltage of 921h is shown, and (e) shows the output signal of the comparator 95. In the figure, the solid line display, the dotted line display, and the alternate long and short dash line display show the waveforms for the respective phase voltage detection units 92, 92 ', 92 ".

That is, in the open-phase detection circuit 9, the primary winding of the power supply voltage detecting transformer 91 is delta-connected and the line voltages V _RS , V _ST , and V _TR are obtained in the secondary winding. Furthermore, each phase voltage detector 92
The full-wave rectification is performed by the rectifier circuit 921a to obtain the output voltage V _{RF, which} is compared with the reference setter 921b by the comparator 921c, and the output voltage V _CP and the square wave are output.
However, level V ₉₂₁ is the setting level of the reference setter 921b. Therefore, as shown in the figure, the square wave of the output voltage V _CP has a substantially constant duty.

Further, the resistors 921d and 921e, the diodes 921f and 921g, and the capacitor 921h in each phase voltage detection unit 92 form an integrating circuit. Therefore, such an integrating amplifier is used when the line voltage value becomes smaller than the value related to the reference voltage. Increase the integral output to
In the opposite case, yes, the capacitor 92h is discharged and the integrated output decreases. Here, it is assumed that the integration resistance is selected so that the integrated output is sufficiently reduced during the period when the line voltage is higher than the reference voltage in the normal power supply state and the integrated output is decreasing. By doing so, the voltage V _C of the capacitor 921h becomes a substantially constant triangular wave as illustrated, and its peak value also becomes substantially constant.

Next, a phase break occurs due to the melting of the power supply fuse in the power converter, the one-line opening due to the contact failure of the switch, etc.
An example of a case in which the R-phase phase is lost will be described assuming that the time when the phase loss occurs is T ₀ .

In FIG. 5, after the time point T _O, the line voltages V _RS and V _TR decrease sharply, so the comparator 921c outputs the voltage V _CP.
Also has a great change in its detail, and changes in the direction of increasing the above-mentioned integrated output as illustrated. The diodes 93, 93 ', 93 "provide the comparator 95 with the maximum capacitor voltage of the phase voltage detection units 92, 92', 93", and accordingly, the reference setter 94 and the comparator 95 cause When the input value generated by the diodes 93, 93 ', 93 "exceeds the level V ₉₄ by the reference setter 94, 95 outputs the output signal 9A for open phase detection.

[Problems to be solved by the invention]

As shown in FIG. 4 and FIG. 5, the conventional method for detecting an open phase of a power converter is to perform the open phase detection function by individually detecting and monitoring the voltage value of the phase of the power supply. Further, although it has an advantage that the electric motor can be driven according to the ability of the protection function of the entire apparatus, it has the following drawbacks.

That is, when the device shown in FIG. 3 is regenerating power to the power source, or when another state connected to the same power source is regenerating power, when the power source fails, the impedance of the power source is used as a load for regeneration. The device inside will generate the voltage. Moreover, this voltage becomes a single-phase square wave voltage at a frequency determined by the circuit constant of the device and the power source impedance.

In such a situation, since the power supply voltage is a square wave but has a sufficient voltage, the circuit that should detect the power failure does not operate, and the crest value of the square wave is shown in FIG.
If the level is higher than the reference setter 921b, the open-phase detection circuit 9 does not operate, and the device continues to be in the self-excited state and falls into an extremely dangerous state. In addition, depending on how the standard setter 921b is established, it will not operate due to the open phase that occurs when the pressure in the power supply is higher than the rating, or conversely, if the voltage drops significantly below the rating, the unbalanced voltage If it is in the state, there is a problem that the phase is lost even though the voltage state is not required to stop the power failure.

This is due to the fact that the three line voltages are individually separated and detected by uniquely comparing the voltage with respect to the fixed reference setter.

For example, if the operating limit is 150 volts in a control circuit that shares 200 and 220 volts, even if the line is open from 110% of the power supply voltage of 220 volts, there will be two The line voltage drops only to 121 volts, which is half the power supply voltage. Moreover, this voltage may exceed 150 V depending on the location of the open phase and the equipment connected to the circuit.In such a case, even if the converter is operating in single phase. Regardless, the open phase detection is not performed.

Further, in the example of FIG. 4, three circuits having exactly the same configuration are provided, and further, these must be adjusted in exactly the same manner, so that the number of parts is large and the adjustment is troublesome. If the power supply voltage detection transistor 91, the rectifier circuit 921a, and the like are used in common with those for phase detection, for example, the circuit system for phase control may be restricted.

Furthermore, as another conventional method, a method focusing on harmonics of the power supply frequency, that is, a three-phase full-wave rectified waveform of the power supply voltage is applied to a band pulse filter to extract a frequency component having a power supply frequency of two times, and depending on its size, In the case of detecting an open phase, the adjustment of the band pass filter becomes troublesome, and the open phase is detected even when a power imbalance that does not reach the open phase occurs. Met.
As mentioned above, when the power supply becomes a square wave at the time of a power failure, the full-wave rectified waveform contains almost no harmonics,
Phase loss detection was not performed.

[Means for solving problems and actions]

The present invention has been made to solve the above-mentioned problems, and pay attention to the fact that the duty of the output signal of the phase detection circuit changes when the phase is lost, and the phase is detected by monitoring this detail. It provides an exceptional device.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

[Embodiment] FIG. 1 shows the essential structure of an embodiment of the present invention shown in FIG. 4, and 9'is an output signal 9A 'to the base amplifier 8 shown in FIG. It is a phase loss detection circuit to give. In the figure, the same reference numerals as those in FIG. 3 indicate parts having the same functions. Here, the open-phase detection circuit 9'includes the duty detection units 96, 9
6 ', diodes 97, 97', a reference setter 94 ', and a comparator 95', which is an example of a detail detecting section composed of an OR gate, a resistor, a diode, and a capacitor, respectively. .

That is, the phase loss detection circuit 9 ′ outputs the phase detection signals 7A and 7D to the duty detection unit 96 and the phase detection signals 7B and 7E to the duty detection unit 96 ′ among the outputs of the phase detection circuit 7 shown in FIG. The two outputs of the phase detection circuit are provided as the inputs of the OR gates of the duty detection units 96 and 96 ', respectively. The operation of the open phase detecting circuit 9'as described above will be described below with reference to FIG.

FIG. 2 shows the waveforms of the respective parts in FIG.
The power supply voltage waveform in the same state as in FIG.
(C), (d), (e) a phase output signals 7A, shows 7D, 7B, 7E of the signal waveform _{W 7A, W 7D, W 7B} , the _{W 7E, (f), (} g) is Diti detector The output voltages V _OR and V _OR ′ of the OR gates of ₉₆ and ₉₆ ′ are shown, and (h) and (i) show the voltages V ₉₆ and V ₉₆ ′ by the integrating capacitors of the duty detectors ₉₆ and ₉₆ ′, respectively (j ) Indicates the output signal of the comparator 95 '.

In FIG. 1 and FIG. 2, as shown before time T ₁ , the phase detection circuit 7 shown in FIG.
Since the 0 ° rectangular wave signal is generated, the phase detection signals 7A, 7D and the phase detection signals 7B, 7E relating to the same phase have a phase difference of 180 °. It goes without saying that there is a phase difference of 120 ° between the phase detection signals 7A, 7B and 7C and between the phase detection signals 7D, 7E and 7F.

Therefore, as shown in FIGS. 2 (f) and 2 (g), the OR gates of the duty detectors 96 and 96 'can be used to detect the same phase 2
By taking the logical sum of the individual phase detection signals, it is possible to obtain always a square wave with a frequency double of the power supply frequency (2: 1).

Further, when this OR gate output is added to an integrating circuit composed of resistors 961b and 961c and a capacitor 961f, a triangular wave having a substantially constant peak value as illustrated is obtained. At this time, it is important to select the values of the resistors 961b and 961c so that a rectangular waveform with a duty factor of (2: 1) is sufficiently discharged in each cycle.

Next, at the time point T ₁ , if a phase loss occurs in the R phase,
Since the line voltage that has established voltage after T ₁ is only the ST phase, the phase detection signals 7B and 7F are exactly the same as the phase detection signals 7C and 7E, and there is a width of 180 ° and a phase difference of 180 °. It becomes the signal of the seed.

Therefore, as a result of the logical sum of the OR gates of the duty detection unit 96 'which receives the phase detection signals 7B and 7E, that is, the waveform of the output voltage V _OR ' is in the state of "1" for almost the entire period. Therefore, the voltage V ₉₆ ′ gradually rises without being discharged, and this integration capacitor voltage becomes the reference setting device 94 ′.
When the level V ₉₄ ′ is reached by the comparator, the comparator 95 ′ detects the open phase and sends the output signal 9 A ′.

Like the phase loss detection circuit 9 ', the present invention detects that the output signal of the phase detection circuit has a width of 120 ° when the power supply is normal, but changes to approximately 180 ° when the phase is lost, and operates it. It will be. Further, it acts to detect specifically that the device is performing single-phase operation corresponding to the open phase state due to the open phase of the power source.

Therefore, the conventional example shown in FIG.
Compared to a method in which the fixed voltage and each line voltage are individually compared to determine and the mutual relationship of the three-phase power supply voltage and the operating status of the device are ignored, the entire power supply is monitored and Detects a phase loss based on the result of monitoring the operating condition of the device, and therefore can perform remarkably appropriate detection. Therefore, even if the power supply voltage remains due to a device regenerating the power supply or a single-phase square wave occurs, an output signal of the phase detection circuit with a width close to 180 ° can be obtained. Will be able to work.

Further, in the open-phase detection, it is not necessary to provide it for all the three phases as shown in the embodiment. In other words, the phase detection circuit output for two phases has a width of 180 ° when there is a phase loss. Therefore, if two of the three phases are monitored, then at least one of the two phases with a width of 180 ° is always monitored. It will be. In this way, it is obvious that the number of circuits can be reduced as compared with the conventional example shown in FIG.

Furthermore, the output of the phase detection circuit, which is controllable vertically, is obtained as an input signal, and since that signal is usually a logic signal, a logic gate can be used directly. Therefore, the transformer, the rectifier circuit, and the level comparison part as shown in FIG. 4 can be eliminated, and a simple device in which the number of circuit components is greatly reduced can be realized.

In this embodiment, the change in the output signal of the phase detection circuit from the width of 120 ° to the width of 180 ° is detected, but the width and the amount of change are variously changed depending on the control method of the phase detection circuit. Will be used. The gist of the present invention is, of course, that the phase loss detection can be performed by capturing the change in the width of the output signal of the phase detection circuit according to the control method.

〔The invention's effect〕

As described above, according to the present invention, the open-phase detection can be surely performed, and the power conversion apparatus that can perform the accurate open-phase detection even when the device which has been difficult in the related art is performing the regenerative operation to the power supply. The phase loss detecting device can be realized, and the practical use is remarkable because it contributes to downsizing of the control circuit and improvement of reliability by reducing the number of circuit components.

[Brief description of drawings]

FIG. 1 and FIG. 2 are circuit diagrams showing a main part configuration of one embodiment according to the present invention and waveform diagrams of respective parts thereof, and FIG. 3 is a circuit diagram showing a conventional example of an AC motor drive device having a phase loss detection circuit, FIG. 4 and FIG. 5 are a circuit diagram and waveform diagrams of respective parts shown for explaining the open phase detection circuit of FIG. 1 ... Three-phase AC power supply, 7 ... Phase detection circuit, 8 ... Base amplifier of converter unit 3, 96, 96 '... Detail detection unit of open phase detection circuit 9', 7A, 7B, 7D, 7E ... … Phase detection signal.

Claims (1)

[Claims] 1. A first pulse having a width of 120 ° centering on the phase angle of the maximum value of the phase voltage for each phase and detecting the phase voltage of the three-phase AC power supply, and the phase angle of the minimum value of the phase voltage. In a power conversion device that includes a power supply voltage phase detection circuit that outputs a second pulse having a width of 120 ° as a phase detection signal with the center as the center, and exchanges power with an AC power supply by the output signal of the power supply voltage phase detection circuit. A converter section input is connected to the power supply voltage phase detection circuit, and the first pulse and the first phase of the first phase and the second phase of the phase detection signals for three phases output from the power supply voltage phase detection circuit A phase loss detection circuit having two pulses as input is provided, and the phase loss detection circuit outputs a signal obtained by integrating a logical sum of the first pulse and the second pulse of the first phase. The detail detector, the first pulse of the second phase and the front Second outputting the integrated signal a logical sum of the second pulse
And a comparator that outputs an open phase detection signal when the high level side of the outputs of the respective duty detection sections reaches a set level.