JP2004088861A - Power conversion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power conversion device capable of exactly detecting phase interruption. <P>SOLUTION: This power conversion device comprises an inverter for converting DC power into AC power, a PWM gate control circuit for controlling the inverter, a transformer for converting three-phase AC power supplied from the inverter, a measuring instrument for measuring the voltage of three-phase power outputted from the transformer, a voltage index calculater for calculating a voltage index value as a magnitude index of the voltage measured by the measuring instrument, and a phase interruption detection part for determining the generation of phase interruption when the voltage index value inputted from the voltage index calculating part is out of a preset value. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a power converter.
[0002]
[Prior art]
As described in Japanese Patent No. 2980698, a conventional power conversion device obtains an effective current value for three phases of an inverter, and when the amount of change in the effective current value exceeds a threshold value, the output power of the inverter is reduced. The inverter was stopped on the assumption that a phase loss occurred.
The conventional power converter configured as described above can detect an open phase of the output power of the inverter when the effective current exceeds the threshold value. Can be prevented in advance.
[0003]
[Problems to be solved by the invention]
However, in the conventional power conversion device, it is determined that there is an imbalance in the current of each phase of the three-phase AC power as an open phase. When the current is unbalanced from the beginning, the three-phase current may be unbalanced and may be erroneously determined to be missing. Therefore, the threshold value must be set in consideration of load fluctuation and unbalance, and it is extremely difficult to set the threshold value to an appropriate value. I could not do it.
Therefore, an object of the present invention is to provide a power converter capable of accurately detecting an open phase.
[0004]
[Means for Solving the Problems]
A power converter according to the present invention includes: an inverter that converts DC power into AC power; a PWM gate control circuit that controls the inverter; a transformer that converts three-phase AC power supplied from the inverter; A measuring instrument for measuring the voltage of the three-phase power output from the transformer, a voltage index calculating section for calculating a voltage index value which is an index of the magnitude of the voltage measured by the measuring instrument, and a voltage index calculating section And a phase loss detection unit that determines that phase loss has occurred when the input voltage index value is outside the set value.
In the power converter according to the present invention, an inverter for converting DC power to AC power, a PWM gate control circuit for controlling the inverter, a transformer for converting three-phase AC power supplied from the inverter, A measuring device for measuring the voltage of the three-phase power output from the transformer, a function for calculating a voltage index value from the voltage detected by the measuring device, and a function for detecting phase loss from the voltage index value A power conversion device comprising:
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
(First Embodiment)
A power converter according to a first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram of a power converter according to a first embodiment of the present invention. FIG. 2 is a configuration diagram of the transformer. FIG. 3 is a block diagram of the voltage index calculator and the phase loss detector according to the first embodiment of the present invention. FIG. 4 is a schematic view of a U-phase arm. FIG. 5 is a simulation result of the voltage index of the circuit shown in FIG. FIG. 6 is a schematic diagram of a U-phase arm. FIG. 7 is a simulation result of the voltage index of the circuit shown in FIG. FIG. 8 is a schematic diagram of a U-phase arm. FIG. 9 is a simulation result of the voltage index of the circuit shown in FIG. FIG. 10 is a schematic diagram of a U-phase arm. FIG. 11 is a simulation result of a voltage index of the circuit shown in FIG.
The power conversion device according to the first embodiment of the present invention includes a DC power supply 1, an inverter 2, a PWM pulse control unit 3, a Y-type transformer 4, a voltage measurement device 6, a voltage index calculation unit 7, a phase loss detection unit. 8. In general, the power converter is generally connected to a load 5 (such as an induction motor).
In the power converter configured as described above, the DC power supply 1 and the inverter 2 are connected. Inverter 2 is connected to PWM pulse control unit 3 and ΔY-type transformer 4. Y-type transformer 4 is connected to voltage measuring device 6. The voltage measuring device 6 is connected to the voltage index calculating section 7. The voltage index calculation unit 7 is connected to the phase loss detection unit 8. The phase loss detector 8 is connected to the PWM pulse controller 3. Note that the Y-type transformer 4 in the power converter is usually connected to a load 5 or the like.
[0006]
Inverter 2 is supplied with DC power from DC power supply 1. The inverter 2 converts the DC power supplied from the DC power supply 1 into three-phase AC power and supplies the three-phase AC power to the Y-type transformer 4. The Y-type transformer 4 steps down the three-phase AC power supplied from the inverter 2 and outputs it to the load 5. The voltage measuring device 6 measures the voltage value of the three-phase AC power output from the Y-type transformer, and outputs the voltage value to the voltage index calculating unit 7. The voltage index calculation unit 7 calculates a voltage index from the voltage value input from the voltage measurement device 6 and outputs the calculated voltage index to the phase loss detection unit 8. The phase loss detecting section 8 outputs an inverter stop command to the PWM pulse control section 3 when a phase loss occurs, and sends a continuous operation command to the PWM pulse control section 3 when no phase loss occurs. Output. The PWM pulse control unit 3 controls the inverter 2 based on the output from the open phase detection unit 8.
In the power converter configured as described above, the voltage index calculator 7 includes an absolute value calculator 9 and a low-pass filter 10 (see FIG. 3). The absolute value calculation unit 9 calculates the absolute value of the three-phase AC power measured by the voltage measuring device 6 and outputs the calculated absolute value to the low-pass filter 10. The low-pass filter 10 calculates a voltage index, which is an index indicating the magnitude of the AC voltage, from the absolute value of the voltage input from the absolute value calculator 9.
[0007]
In the power converter configured as described above, the open phase detection unit 8 includes a comparator 11 and a logical sum operation unit 12 (see FIG. 3). The comparator 11 compares the magnitude of the threshold value input in advance with the magnitude of the voltage index input from the voltage index calculation unit 7, and if the magnitude of the voltage index is larger than the threshold value, performs a logical OR operation on 0. The value is output to the operation unit 12, and if the threshold value is larger than the voltage index, 1 is output to the OR operation unit 12. When the values input from the comparator 11 are all 0, the logical sum operation unit 12 determines that no phase loss has occurred, and outputs a continuous operation command to the PWM pulse control unit 3. In this case, it is determined that an open phase has occurred, and an inverter stop command is output to the PWM pulse control unit 3.
In the power converter configured as described above, as shown in FIG. 4, the U-phase arm of the inverter 2 includes a switching element 13, a switching element 14, a switching element 15, a switching element 16, a diode 17, a diode 18, a diode 19, It comprises a diode 20, a diode 21, and a diode 22. In this U-phase arm, DC power is converted to AC power by switching the switching elements 13 to 16 on and off.
[0008]
In the power converter configured as described above, when the U-phase on the output side of the inverter 2 is disconnected as shown in FIG. 4, it is considered that the voltage index as shown in FIG. 5 is shown. If the U-phase on the inverter output side is disconnected in 300 ms, the U-phase voltage on the primary side of the transformer 4 (see FIGS. 1 and 2) becomes 0 after 300 ms. Therefore, the W-phase and the U-phase on the secondary side have the same potential, and the line voltage Vwu between the secondary-side W and U becomes zero. When the line voltage Vwu between the secondary side W-U becomes zero, the phase between Vuv and Vwu is shifted by 180 degrees and becomes a single-phase AC waveform (see FIG. 5). Therefore, when the U-phase on the inverter output side is disconnected, the open phase can be detected from the voltage index of Vwu between the secondary side W-U.
In the power converter configured as described above, when the switching elements 13 and 14 provided in the U-phase arm of the inverter 2 fail at 300 ms as shown in FIG. 6, as shown in FIG. It is considered that it shows a good voltage index. When the switching element 13 and the switching element 14 fail, the line voltage Vwu between the secondary side W and U becomes substantially half as small as the other phases (Vvw, Vuv). Therefore, even when the switching elements 13 and 14 are out of order, it is possible to detect an open phase from the voltage index of the line voltage Vwu between the secondary side W-U.
[0009]
In the power converter configured as described above, when the switching element 14 fails at 300 ms as shown in FIG. 8 and a circuit is opened in this switching element to simulate, as shown in FIG. It is considered to indicate a voltage index. When the switching element 14 fails and the circuit is opened in this switching element, the line voltage Vwu (Vvw, Vuv) between the secondary side W-U becomes approximately half as small as the other phases. Therefore, in this case, a phase loss can be detected from the voltage index of the line voltage Vwu between the secondary side W-U.
In the power converter configured as described above, when the switching element 13 fails at 300 ms as shown in FIG. 10 and a circuit is opened in this switching element to simulate, as shown in FIG. It is considered to indicate a voltage index. If the switching element 13 breaks down and the circuit is opened in this switching element, the line voltage Vwu (Vvw, Vuv) between the secondary side W and U becomes approximately half as small as the other phases. Therefore, in this case, a phase loss can be detected from the voltage index of the line voltage Vwu between the secondary side W-U.
The power converter configured as described above can detect an open phase of the inverter 2 to prevent a healthy phase of the inverter, a transformer, and a load device. In addition, since the phase in which the open phase has occurred can be specified and used as information at the time of repair, the efficiency of the repair work can be improved.
[0010]
(Second embodiment)
A power converter according to a second embodiment of the present invention will be described in detail with reference to the drawings. FIG. 12 is a block diagram of a voltage index calculator and a phase loss detector according to the second embodiment of the present invention. 1 to 3 are denoted by the same reference numerals, and description thereof will be omitted.
A power converter according to a second embodiment of the present invention includes a DC power supply 1, an inverter 2, a PWM pulse controller 3, a Y-type transformer 4, a voltage measuring instrument 5, a voltage index calculator 7, a phase loss detector. 8.
In the power conversion device configured as described above, the open phase detection unit 8 includes the comparator 11, the OR operation unit 12, the maximum value operation unit 23, the comparator 24, and the AND operation unit 25. (See FIG. 12).
In the power converter configured as described above, the maximum value calculator 23 records the maximum value of the voltage index (hereinafter, the operation state index) input from the voltage index calculator 7 and outputs the same to the comparator 24. Comparator 24 compares the threshold value with the operation state index, and if it is out of the predetermined range, it is not an open phase, but an abnormality has occurred in the input power supply of inverter 2 or the operation state of inverter 2 itself is immediately after start-up or a stop command. Assuming that it is in a later transient state, the operation state is output to logical product 25. In the logical product 25, the phase loss is detected only when the operation state input from the comparator 24 is within the range of the threshold value. Therefore, the power converter of the present embodiment has higher reliability than the power converter of the first embodiment.
[0011]
(Third embodiment)
A power converter according to a third embodiment of the present invention will be described in detail with reference to the drawings. FIG. 13 is a block diagram of a voltage index calculator and a phase loss detector according to the third embodiment of the present invention. 1 to 3 and FIG. 12 are denoted by the same reference numerals, and description thereof is omitted.
A power converter according to a third embodiment of the present invention includes a DC power supply 1, an inverter 2, a PWM pulse control unit 3, a Y-type transformer 4, a voltage measurement device 5, a voltage index calculation unit 7, and an open phase detection unit. 8.
In the power converter configured as described above, only two output voltages out of the three phases of the transformer are input to the voltage index calculation unit 7, and the remaining one phase uses the three-phase equilibrium property. It is determined by the voltage calculator 26.
In the power converter configured as described above, by measuring two phases out of the three-phase output voltages of the transformer, the power value of the remaining one phase can be obtained, so that there is an advantage that the size of the device is reduced. And weight can be reduced.
(Fourth embodiment)
A power converter according to a fourth embodiment of the present invention will be described in detail with reference to the drawings. FIG. 14 is a configuration diagram of a power conversion device according to a fourth embodiment of the present invention. 1 to 3 are denoted by the same reference numerals, and description thereof will be omitted.
[0012]
A power converter according to a fourth embodiment of the present invention includes a DC power supply 1, an inverter 2, a PWM pulse controller 3, a Y-type transformer 4, a voltage measuring instrument 5, a voltage index calculator 7, a phase loss detector. 8, a power switch 27.
In the power converter configured as described above, a signal of phase loss detection detected by the phase loss detection unit 8 is transmitted not only to the PWM pulse control unit 3 but also to the power switch 27 of the inverter input. When the phase loss is detected, the inverter gate stop and the input power cutoff are performed in parallel, so that the reliability of the output power cutoff increases.
Although the power conversion devices of the first to fourth embodiments based on the present invention use three-level inverters, the same effects can be obtained with two-level inverters, so the invention is not limited to three-level inverters.
In the power converters of the first to fourth embodiments according to the present invention, since the comparator 11 only needs to be able to compare the sizes, the output is the same as the power converter according to the first to fourth embodiments according to the present invention. The contents described in the device are not limited.
In the power conversion devices according to the first to fourth embodiments of the present invention, the voltage index calculation unit 7 calculates the voltage index by the absolute value calculation unit 9 and the low-pass filter 10, but the voltage index changes. Since a voltage index of the same quality can be calculated by a method using a voltage square value, a method using a half-period moving average instead of a low-pass filter, the absolute value calculation unit 9 and the low-pass filter 10 are not limited.
[0013]
【The invention's effect】
According to the present invention, it is possible to provide a power converter capable of accurately detecting an open phase.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a power conversion device according to a first embodiment of the present invention.
FIG. 2 is a configuration diagram of a transformer.
FIG. 3 is a block diagram of a voltage index calculator and an open phase detector according to the first embodiment of the present invention.
FIG. 4 is a schematic view of a U-phase arm.
5 is a simulation result of a voltage index of the circuit shown in FIG. 4;
FIG. 6 is a schematic view of a U-phase arm.
FIG. 7 is a simulation result of a voltage index of the circuit shown in FIG. 6;
FIG. 8 is a schematic view of a U-phase arm.
9 is a simulation result of a voltage index of the circuit shown in FIG. 8;
FIG. 10 is a schematic view of a U-phase arm.
FIG. 11 is a simulation result of a voltage index of the circuit shown in FIG. 10;
FIG. 12 is a block diagram of a voltage index calculator and an open phase detector according to a second embodiment of the present invention.
FIG. 13 is a block diagram of a voltage index calculation unit and an open phase detection unit according to a third embodiment of the present invention.
FIG. 14 is a configuration diagram of a power conversion device according to a fourth embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... DC power supply 2 ... Inverter 3 ... PWM pulse control part 4 ... Y type transformer 5 ... Load 6 ... Voltage measuring instrument 7 ... Voltage index calculation part 8 ... · Open phase detection unit 9 ··· Absolute value calculation unit 10 ··· Low pass filter 11 ··· Comparator 12 ··· OR operation unit 13 ··· Switching element 14 ··· Switching element 15 ··· Switching Element 16 Switching element 17 Diode 18 Diode 19 Diode 20 Diode 21 Diode 22 Diode 23 Maximum value calculator 24 Comparison Unit 25: AND operation unit 26: Phase voltage operation unit 27: Power switch

Claims (5)

An inverter that converts DC power to AC power,
A PWM gate control circuit for controlling the inverter device;
A transformer for converting three-phase AC power supplied from the inverter,
A measuring device for measuring the voltage of the three-phase power output from the transformer,
A voltage index calculating section for calculating a voltage index value from the voltage measured by the measuring instrument; and an open phase for determining that an open phase has occurred when the voltage index value input from the voltage index calculating section is outside a set value. A detection unit;
A power conversion device comprising: An inverter that converts DC power to AC power,
A PWM gate control circuit for controlling the inverter device;
A transformer that converts the three-phase AC power supplied from the inverter and a measuring device that measures the voltage of the three-phase power output from the transformer,
A function of calculating a voltage index value from the voltage detected by the measuring device,
A function of detecting an open phase from this voltage index value,
A power conversion device comprising: The power converter according to claim 1,
Having means for determining an operation state from the voltage index value,
This operating state is that the open phase detection unit does not perform the open phase detection except during the normal operation,
Characteristic power converter. The power converter according to claim 1,
The measuring device measures only the two-phase output voltage of the three-phase AC power converted by the transformer,
Characteristic power converter. The power converter according to claim 1,
When the open phase is detected by the open phase detection unit, the drive of the inverter is stopped, and the input DC power of the inverter is cut off.
Characteristic power converter.

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