JPH06335154A - Open-phase detecting device - Google Patents

Abstract

(57) [Summary] [Structure] The filter capacitor 4 is connected to the input terminal of the inverter device 5. The voltage across the filter capacitor 4 is detected by the voltage detector 7, and the sampling circuit 8
At a frequency of twice the AC frequency flowing through the overhead line. Then, by inputting them to the differential operation circuit 9, the absolute value operation circuit 10, and the first-order delay circuit 11, the accumulated value of the variation amount of the voltage across the both ends is obtained. This cumulative value is input to the control device 12, and when the time during which it is continuously judged as an abnormal value by comparing with a predetermined reference value is equal to or longer than the predetermined reference time, a protection operation command is issued to the inverter device 5. Is output. EFFECTS OF THE INVENTION According to the present invention, the open-phase detection can be performed reliably by monitoring the voltage across the filter capacitor and extracting the sampling cycle at a frequency cycle twice the AC frequency to determine the open-phase. it can.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an open phase detecting device for detecting open phase of three-phase AC power output by an inverter device.

[0002]

2. Description of the Related Art In a system in which DC power is converted into 3-phase AC power by an inverter device and an induction motor or the like is driven, it is an important issue to take measures against open phase of the 3-phase AC power output from the inverter device. Is. The open phase of the 3-phase AC power may be caused by a fault on the load side such as a ground fault in the induction motor, by the disconnection of the 3-phase AC power line, or by a malfunction of the semiconductor element or the like that constitutes the inverter device. To do. Therefore, in the prior art, when the instantaneous value of each three-phase AC current at the output end of the inverter device is detected and the instantaneous value total current value obtained by inputting each instantaneous value to the adding circuit is not zero, it is regarded as a phase loss. Judgment was made and protection operations such as a stop command were performed on the inverter device. However, in the case of disconnection of the three-phase AC output line, malfunction of the inverter device, etc., even if a current is forced to flow in a conducting path that does not originally flow and a phase loss occurs, each three-phase The sum of the instantaneous value currents of the AC output lines was zero, and the open phase could not be detected.

Therefore, the voltage across the filter capacitor connected to the input terminal of the inverter device is monitored to obtain the amount of variation, and the magnitude of this amount of variation and the duration are detected as a phase loss by exceeding a certain value. Things that do have been developed.

[0004]

SUMMARY OF THE INVENTION In a system in which the power of a DC overhead wire is fed by a pantograph and converted into 3-phase AC power by an inverter device, the ripple generated in a steady state is so small that it can be ignored. The fluctuation amount of the voltage is clearly different between the sound state and the open phase, and the open phase detection can be surely performed.

However, in a system in which the power of an AC overhead wire is fed by a pantograph, is once converted into DC power by a converter device, and is then converted into three-phase AC power by an inverter device, the filter capacitor is constantly charged. A ripple voltage with a frequency twice that of the power supply (AC flowing through the overhead wire) will be superimposed. For this reason, there is a problem that the fluctuation amount of the voltage across the filter capacitor becomes large even when the filter is healthy, and the phase is erroneously detected. SUMMARY OF THE INVENTION It is therefore an object of the present invention to eliminate the above problems and provide a highly reliable open phase detecting device capable of reliably detecting open phase even in an AC feeding system.

[0006]

In order to achieve the above object, in the invention according to claim 1, the voltage across the filter capacitor is monitored, and the voltage across the filter capacitor is measured at a cycle of an integral multiple of twice the frequency of the alternating current flowing through the overhead wire. The voltage fluctuation amount detection device that detects the fluctuation amount of the voltage across it, and compares the output of this voltage fluctuation amount detection device with a predetermined reference value. And a control device that outputs a protection operation command. In the invention according to claim 2, the phase current flowing at the output end of the inverter device is detected, the effective value is calculated, and the effective value is extracted at a cycle of an integral multiple of twice the frequency of the alternating current flowing through the overhead wire. Then, by comparing the output of this effective current fluctuation amount detection device with the effective current fluctuation amount detection device that detects the fluctuation amount of the effective value with a predetermined reference value, and when it is judged to be an abnormal value, protection is provided to the inverter device. And a control device that outputs an operation command.

[0007]

The ripple voltage is constantly superposed on the filter capacitor at a frequency twice the frequency of the alternating current flowing through the overhead wire. Therefore, in the invention described in claim 1, by extracting the voltage across the filter capacitor by an integral multiple of the period of the ripple voltage, the ripple that occurs steadily is output as zero in the voltage fluctuation amount detection device. At the time of phase loss, ripples generated due to phase loss are superimposed in addition to ripples that occur steadily, so fluctuations occur, and the controller determines the phase loss and issues a protection operation command to the inverter device. Is output. Further, since the ripple voltage is constantly superposed on the filter capacitor, a ripple is generated in the phase current due to the influence of the ripple voltage. Therefore, in the invention of claim 2, the effective current is calculated from the phase current, and the effective current is extracted by an integral multiple of the period of the ripple. To be done. When the phase is lost, a ripple is generated in proportion to the frequency of the inverter device, causing a variation amount, and the control device determines that the phase is lost and outputs a protection operation command to the inverter device.

[0008]

Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of an open phase detecting device showing an embodiment of the invention described in claim 1. 2 is a main circuit configuration diagram of the AC feeding system. AC power is supplied from a pantograph 1 from an AC overhead wire (not shown) which is a power source, and this AC power is supplied to a converter device 3 via a transformer 2. In the converter device 3, AC power is converted into DC power, and this DC power is smoothed by the filter capacitor 4. Then, the smoothed DC power is converted into three-phase AC power by the inverter device 5 (shown in FIG. 1 as one composed of GTO thyristors 51 to 56) and supplied to the induction motor 6 as a load. It The voltage V ₁ across the filter capacitor 4 is input to the voltage fluctuation amount detecting device, and the fluctuation amount is obtained as follows. That is, the voltage detector (DCPT) 7 detects the voltage V _{1 at} both ends, and the sampling circuit 8 extracts the sampling voltage V ₁ (n) at regular intervals T. However, n is the number of times of sampling. And the differential operation circuit 9
Sampling voltage V per unit time by passing
Change amount of ₁ (n) (hereinafter referred to as voltage change amount) V ₂ (n)
Is obtained. Since the voltage change amount V ₂ (n) has both positive and negative values, the variation amount V ₃ (n) of the sampling voltage V ₂ (n) can be obtained by passing through the absolute value calculation circuit 10.
Further, by passing the variation amount V ₃ (n) through the first-order delay circuit 11, an estimated value (hereinafter, shown as an accumulated value) V ₄ of the sampling voltage V ₁ (n) can be obtained. Then, the control device 12 inputs this accumulated value V ₄ and outputs a protection operation command S to the gate control unit 13 when it judges that there is a phase loss. The control device 12 is provided with a cumulative value comparison circuit 12a for comparing the magnitude of the cumulative value V ₄ with a predetermined reference value C ₁ . In order to prevent erroneous detection, a duration comparison circuit 12b may be provided for comparing the duration t (W) of the output by the cumulative value comparison circuit 12a with a predetermined reference time C ₂ . When the controller 12 confirms the phase loss, the protection operation command S is output to the gate controller 13, and the gate controller 13 issues a gate command (stop command) to the inverter device 5. Output.

The filter capacitor 4 has a power frequency of 2
The doubled ripple voltage V _p is superimposed. The situation is shown in FIG. FIG. 3 is a diagram showing the capacitor voltage when the sound is normal. The ripple cycle T is the reciprocal of (2 × f _s ) when the power supply frequency is f _s . Therefore, if the sampling cycle of the sampling circuit 8 is T and the sampling voltage at the nth sampling is V ₁ (n),

[0010]

## EQU1 ## V ₁ (n + 1) -V ₁ (n) = 0, and the ripple that occurs steadily becomes zero. That is, the sampling cycle T of the sampling circuit 8 is set to 1 / (2 × f
_s ), V ₄ becomes almost zero and the protection operation command S does not flow to the gate control unit 13. On the other hand, when the three-phase AC power converted by the inverter device 5 is out of phase, the three-phase AC instantaneous power becomes unbalanced. Therefore, when the induction motor 6 side is viewed from the DC power end, the power consumption becomes unstable and ripples occur in the capacitor voltage V ₁ . The capacitor voltage V ₁ is detected by the DCPT 7, and the cumulative value V ₄ is obtained by passing through the sampling circuit 8, the differential operation circuit 9, the absolute value operation circuit 10, and the first-order delay circuit 11 as described above.

That is, the ripple voltage V _{p in} the steady state is further superimposed with the ripple component generated due to the open phase. Therefore, when the cumulative value V ₄ is input to the control device 11, the cumulative value comparing circuit 12a first compares the predetermined reference value C ₁ with the cumulative value V ₄ . The reference value C ₁ is easily determined because V ₄ is almost zero when the sound is normal, but V ₄ becomes large because a large ripple occurs during the open phase. Therefore, in the cumulative value comparison circuit 12a, the cumulative value V ₄ is the reference value C.
If the value is smaller than _1, it is determined to be normal, and if the accumulated value V ₄ is larger than the reference value C _{1, the} abnormal signal W is output. This abnormality signal W is input to the duration comparison circuit 12b, and the duration (duration) t (W) that is continuously input is counted. Then, this continuation time t (W) is compared with a predetermined reference time C ₂ . This duration comparison circuit 12b
Is provided to determine that the ripple amount comparison circuit 12a erroneously detects a phase loss with respect to a ripple that occurs other than during a phase loss, and the reference time C ₂ is set to about 1 to 3 seconds. To be Therefore, in the duration comparison circuit 12b, the duration t
If (W) is shorter than the reference time C ₂ , it is determined that the phase is not lost, and when the duration t (W) becomes longer than the reference time C ₂ , the gate control unit 13 is protected. The command S is output. The gate control unit 13 receives the protection operation command S,
A gate command (stop command) is output to the inverter device 5.

Thus, the voltage V ₁ across the filter capacitor 4 is detected by the DCPT 7, and the sampling cycle T
By making the reciprocal of twice the power supply frequency f _s , it is possible to prevent the ripple due to the power supply in the steady state from being erroneously detected as an open phase. The same effect can be obtained even if the sampling period T is an integral multiple of the period (= 1/2 × f _s ) of twice the frequency of the power supply, and the sampling period can be further extended. When incorporated,
The software load can be reduced.

FIG. 4 is a block diagram of an open phase detecting device showing an embodiment of the invention as defined in claim 2. In FIG. In this embodiment, the u-phase current I _u , the V-phase current I _v and the W-phase current I _w of the induction motor 6 are detected and the effective value calculation circuit 14 calculates the effective current I ₁ . The effective current I ₁ is calculated by the fluctuation amount detecting device and the control device in the same manner as in the first aspect of the invention to detect the open phase. More specifically, the effective current I ₁ is the sampling current I ₁ (n) in the sampling circuit 15 at constant intervals T.
Is extracted, and the current change amount I ₂ is passed through the differential operation circuit 16.
Find (n). Further, the variation amount I ₃ (n) is obtained through the absolute value calculation circuit 17, and the cumulative value I ₄ is obtained by the first-order delay circuit 18. Then, the control device 19 inputs the accumulated value I ₄ , and outputs a protection operation command S to the gate control unit 20 when it is judged that there is a phase loss. The control device 19 compares the magnitude of the cumulative value I ₄ with a predetermined reference value C ₁ and a cumulative value comparison circuit 19a and the duration t (W) of the output by the cumulative value comparison circuit 19a to a predetermined reference time C 1. ₂ and a duration comparison circuit 19b for comparing with ₂ . When the controller 19 confirms the phase loss, the protection operation command S is output to the gate controller 20 and the gate controller 13 issues a gate command (stop command) to the inverter device 5. Output.

When the ripple voltage V _p having a frequency twice that of the power supply is superimposed on the voltage of the filter capacitor 4, the effect thereof causes the effective current I ₁ to have a ripple with a frequency twice the AC power. This is shown in FIG. FIG. 5 is a diagram showing an effective current in a healthy state. In general, the u-phase current I _u , the v-phase current I _v , and the w-phase current I _w are expressed as in Equation 2.

[0015]

[Equation 2] Here, I _p1 , I _p2 , and I _p3 are ripples that are constantly generated. In addition, the effective current I ₁ is expressed as in Equation 3.

[0016]

[Equation 3] If the sampling cycle T of the sampling circuit 15 is made equal to twice the frequency cycle of the AC power supply,

[0017]

## EQU4 ## I ₁ (n + 1) -I ₁ (n) = 0, and the ripple generated in the steady state becomes zero. Therefore, when normal, I ₄ becomes almost zero and the protection operation command S does not flow to the gate control unit 20. On the other hand, when the phase is lost, the effective current I ₁ becomes unstable as follows. Taking the case where the u-phase is now missing as an example, it becomes as shown in Formula 5.

[0018]

[Equation 5] Since the inverter device 5 conformally accelerates from zero frequency, the effective current I ₁ has a ripple component proportional to the frequency of the inverter device 5 in the sampling period T. Therefore, it is possible to prevent the ripple due to the power source at the time of soundness from being detected as an open phase. Also in this embodiment, the same effect can be obtained even if the sampling cycle T is set to an integral multiple of the cycle of the frequency twice that of the power source.

[0019]

As described above, according to the first aspect of the present invention, the voltage across the filter capacitor is monitored and extracted at a cycle of an integral multiple of twice the power supply frequency to detect a missing phase. By making a determination, the open phase detection can be reliably performed. According to the second aspect of the invention, by detecting the three-phase current of the induction motor and extracting it at a cycle of an integral multiple of twice the power supply frequency to determine the open phase, it is possible to detect the open phase surely. Can be done. Therefore, it is possible to provide the open-phase detection device that does not perform erroneous detection regardless of the filter capacitor capacity and the running condition.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an open-phase detection device according to a first aspect of the invention.

FIG. 2 is a main circuit diagram of an AC feeding system.

FIG. 3 is a diagram showing a voltage across a filter capacitor.

FIG. 4 is a configuration diagram of an open phase detecting device according to a second aspect of the invention.

FIG. 5 is a diagram showing a phase current.

[Explanation of symbols]

 1 ... DC power supply 3 ... Converter device 4 ... Filter capacitor 5 ... Inverter device 6 ... Induction motor 7 ... DCPT 8, 15 ... Sampling circuit 9, 16 ... Differential calculation circuit 10, 17 ... Absolute value calculation circuit 11, 18 ... Primary delay circuit 12, 19a ... Cumulative value comparison circuit 12, 19b ... Duration comparison circuit 13, 20 ... Gate control unit 14 ... Effective value calculation circuit

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location H02M 7/48 M 9181-5H

Claims (2)

[Claims] 1. A first conversion device for converting AC power supplied from a power source into DC power, a filter capacitor connected to an output terminal of the first conversion device for smoothing the DC power, A second converter that converts smoothed DC power into three-phase AC power, and a load that is connected to an output end of the second converter, the voltage across the filter capacitor being monitored. Then, a voltage fluctuation amount detection device that detects the fluctuation amount of the both-end voltage by extracting the both-end voltage at a cycle of an integral multiple of twice the frequency of the power supply, and an output of the voltage fluctuation amount detection device as a predetermined reference. And a controller for outputting a protection operation command to the second converter when it is determined to be an abnormal value. 2. A first converter for converting AC power supplied from a power source into DC power, a filter capacitor connected to an output terminal of the first converter for smoothing the DC power, A second converter that converts smoothed DC power into three-phase AC power, and a load that is connected to an output end of the second converter, wherein the output of the second converter is provided. An effective current fluctuation amount detection device for detecting a fluctuation amount of the effective value by detecting a phase current flowing through an end, calculating an effective value, extracting the effective value at a cycle of an integral multiple of twice the frequency of the power source. And a control device that compares the output of the effective current fluctuation amount detection device with a predetermined reference value and outputs a protection operation command to the second conversion device when it is determined to be an abnormal value. Characteristic open phase detection device.