JP2010119214A - Inverter device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an excessive current or an excessive voltage when a coil or a wiring of a permanent-magnet synchronous motor is ground-faulted. <P>SOLUTION: An inverter device includes: a DC voltage source whose one end is grounded so as to output a DC voltage; and three sets of switching circuits each having a series connection of a switching element and a freewheel diode connected in reverse parallel between outputs of the DC voltage source. A three-phase permanent-magnet synchronous motor is connected between the three sets of series connections. A ground-fault is detected when a wiring connecting the permanent-magnet synchronous motor or a coil of the permanent-magnet synchronous motor is ground-faulted. Each switching element between a point connected to the permanent-magnet synchronous motor and the grounded one-end of the DC voltage source is made conductive while the other switching elements are disconnected. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an inverter device for driving a permanent magnet type synchronous motor, and particularly to prevent excessive current and torque during a ground fault.

  As an example, FIG. 3 shows a configuration diagram of an inverter device, and a conventional technique will be described based on this diagram.

The DC voltage source 1 is a DC voltage source, one of which is grounded. The higher voltage is on the P side, the lower voltage is on the N side, and the N side is grounded. The inverter circuit 2 receives a DC voltage from the DC voltage source 1 and outputs a three-phase AC voltage. U-phase switching circuit 21 outputs the U-phase output voltage v _U, V-phase switching circuit 22 outputs the V-phase output voltage v _V, W-phase switching circuit 23 outputs the W-phase output voltage v _W.

  The U-phase switching circuit 21, the V-phase switching circuit 22, and the W-phase switching circuit 23 each have the configuration shown in FIG. A P-side switching element 201 and a P-side freewheel diode 202 connected in antiparallel and an N-side switching element 203 and an N-side freewheel diode 204 connected in antiparallel are connected in series between DC voltage sources. Connected and connected in series becomes the output voltage of each phase.

A permanent magnet type synchronous motor 3 is connected to the three-phase output voltages v _U , v _V , and v _W of the inverter circuit 2. The current detector 4 detects a U-phase current i _U , a V-phase current i _V , and a W-phase current i _w flowing from the inverter circuit 2 to the permanent magnet type synchronous motor 3.

FIG. 5 is a configuration example of the control circuit 5. The current controller 51 inputs the three-phase currents i _U , i _V , i _W detected by the current detector 4, calculates the rotation speed and rotation angle of the permanent magnet type synchronous motor 3, and follows the control command. The voltage command is output. The PWM controller 52 receives the voltage command that is the output of the current controller 51, and sends a switching command that matches the fundamental wave component to the voltage command to the P-side switching element 201 and the N-side switching element 203 of each phase. Output. The control command is a command for torque or rotational speed of the permanent magnet type synchronous motor 3. (For example, Patent Document 1)

  Here, the detailed operation of the inverter circuit 2 will be described using the U-phase switching circuit 21, but the same operation is performed in the V-phase switching circuit 22 and the W-phase switching circuit 23. Note that the switching element is turned on in the conduction state and turned off in the cutoff state.

P-side switching element 201 is turned on, if the N-side switching element 203 is turned off, when the U-phase current i _U is positive flows U-phase current i _U via P-side switching element 201. On the other hand when the U-phase current i _U is negative flows U-phase current i _U via P side freewheeling diode 202. In either case, the U-phase voltage v _U matches the P side of the DC voltage source 1.

When the P-side switching element 201 is turned off and the N-side switching element 203 is turned on, when the U-phase current i _U is positive, the U-phase current i _U flows through the N-side freewheel diode 204, and the U-phase current i _{When U} is negative, a U-phase current i _U flows through the N-side switching element 203. In either case, the U-phase voltage v _U matches the N side of the DC voltage source 1.

When both the P-side switching element 201 and the N-side switching element 203 are off, when the U-phase current i _U is positive, the U-phase current i _U flows through the N-side freewheel diode 204 and the U-phase voltage v _U coincides with the P side of the DC voltage source 1. When the U-phase current i _U is negative, the U-phase current i _U flows through the P-side freewheel diode 202, and the U-phase voltage v _U matches the N side of the DC voltage source 1.

When both the P-side switching element 201 and the N-side switching element 203 are on, the DC voltage source 1 is short-circuited, and an excessive current flows through the P-side switching element 201 and the N-side switching element 203, causing element destruction. Therefore, the PWM controller 52 is prohibited from issuing such a switching command.
Patent Publication 2001-69785

  If one phase of the coil of the permanent magnet type synchronous motor 3 or one phase of the wiring between the inverter circuit 2 and the permanent magnet type synchronous motor 3 is grounded, an excessive current / torque is generated.

  As an example of the ground fault, the case where the W-phase wiring is grounded will be described in detail with reference to FIG. When a ground fault occurs, the current controller 51 becomes uncontrollable and the PWM controller 52 stops outputting the switching command. Therefore, the P-side switching of the U-phase switching circuit 21, the V-phase switching circuit 22, and the W-phase switching circuit 23 is performed. The element 201 and the N-side switching element 203 are all turned off.

  Since the N side of the DC voltage source 1 is grounded, a circuit is formed via the grounded W-phase wiring and the N-side freewheel diode 204 of the U-phase switching circuit 21 and the V-phase switching circuit 22. Become.

Figure 7 shows the grounding of the W phase wiring when the difference between the U phase voltage v _U and the W phase voltage v _W or the difference between the V phase voltage v _V and the W phase voltage v _W does not exceed the voltage of the DC voltage source 1 This is an equivalent circuit. The permanent magnet type synchronous motor 3 tries to flow an alternating current because an alternating current induced voltage is generated by the permanent magnet. However, the U-phase current i _U and the V-phase current i _V flow only in one direction by the free wheel diode 204. For this reason, since the flowing current increases in one direction, an excessive current may occur compared to the assumed current. When an excessive current is generated, an excessive torque is generated at the same time.

The difference between the U-phase voltage v _U and the W-phase voltage v _W or the difference between the V-phase voltage v _V and the W-phase voltage v _W is caused by the AC induced voltage generated by the permanent magnet of the permanent magnet type synchronous motor 3. In the case of exceeding, the U-phase current i _U or the V-phase current i _V flows to the DC voltage source 1 via the P-side freewheel diode 202 of each phase, but depending on the permanent magnet of the permanent magnet type synchronous motor 3 Since the AC induced voltage is designed to be equal to or less than the voltage of the DC voltage source 1, even if a current flows to the DC voltage source 1, the AC induced voltage is small.

  When excessive current and torque are generated, various problems are assumed. As an example, when a current more than expected in normal operation flows, the coil of the permanent magnet type synchronous motor 3 or the wiring between the permanent magnet type synchronous motor 3 and the inverter circuit 2 may be overheated, causing a fire. . Moreover, since an excessive current flows through the N-side freewheel diode 204, the N-side freewheel diode 204 may be damaged. Further, since the current generated at this time works to suppress the action of the permanent magnet built in the permanent magnet type synchronous motor 3, there is a risk of demagnetizing the permanent magnet of the permanent magnet type synchronous motor 3. When the permanent magnet of the permanent magnet type synchronous motor 3 is demagnetized, it is necessary to disassemble and repair the permanent magnet type synchronous motor 3 in order to replace the permanent magnet, or to replace the permanent magnet type synchronous motor 3 itself with a new one. It is extremely inefficient.

  In addition, when excessive torque is generated, the permanent magnet type synchronous motor 3 may be mechanically damaged or a mechanical device connected to the permanent magnet type synchronous motor 3 may be damaged.

  According to the first aspect of the present invention, a DC voltage source that outputs a DC voltage with one end grounded, and a plurality of switching elements and free wheel diodes connected in reverse parallel between the outputs of the DC voltage source are connected in series. There are three sets, and in the inverter device in which a three-phase permanent magnet type synchronous motor is connected between the three sets of series connection, wiring for connecting the permanent magnet type synchronous motor or a coil of the permanent magnet type synchronous motor When a ground fault occurs, the ground fault is detected, and all the switching elements between the place where the permanent magnet type synchronous motor is connected and one end of the DC voltage source that is grounded are in a conductive state. An inverter device characterized in that all elements are cut off.

  According to a second aspect of the present invention, in the inverter device of the first aspect, the ground fault is detected when the sum of three-phase currents is not zero.

  According to the present invention, it is possible to prevent an excessive current or torque from being generated even when a ground fault occurs.

  There are three sets of a DC voltage source that outputs a DC voltage with one end grounded, and a plurality of series-connected switching elements and free wheel diodes connected between the outputs of the DC voltage source. In the inverter device in which a three-phase permanent magnet type synchronous motor is connected between the series connection, the ground fault occurs when the wiring connecting the permanent magnet type synchronous motor or the coil of the permanent magnet type synchronous motor is grounded. The switching elements between the location where the permanent magnet type synchronous motor is connected and one end of the DC voltage source grounded are all in a conducting state, and all other switching elements are in a shut-off state. A featured inverter device.

  The invention of claim 1 and claim 2 will be described with reference to FIG. 1, but the same parts as those of the prior art will be omitted.

The adder 53 outputs the sum of the U-phase current i _U and V-phase current i _V and W-phase current i _W. The ground fault determiner 54 outputs an abnormal signal when the output of the adder 53 is not zero.

Since during normal operation that does not contrast U-phase current i _U, V-phase current i _V, the current sum of the W-phase current i _W becomes zero, the ground fault occurs current sum of the three phases is zero, the configuration If a ground fault occurs, an abnormal signal can be output.

  The switch 55 outputs the output of the PWM controller 52 as it is when the adder 53 does not output an abnormal signal, and the U-phase switching circuit 21 and the V-phase switching when the adder 53 outputs an abnormal signal. Signals that turn off all P-side switching elements 201 and turn on all N-side switching elements 203 of the circuit 22 and the W-phase switching circuit 23 are output.

  FIG. 2 is an equivalent circuit corresponding to FIG. 7 of the conventional example when the present invention is implemented. Even if the W-phase wiring is grounded as shown in the example, all phases of current can flow in both directions, so there is no risk of current increase in one direction, and excessive current and torque are generated. Can be prevented.

  Since the DC electric railway uses the voltage between the overhead line and the track, one end of the DC voltage of the inverter is grounded, and if a ground fault occurs when driving the permanent magnet synchronous motor, excessive current and torque are generated. However, since it is solved by the present invention, it is extremely effective.

It is a control circuit block diagram of one Example of this invention. It is an equivalent circuit at the time of a ground fault of one Example of this invention. It is a structural example of an inverter apparatus. It is an example for one phase of the switching circuit of an inverter circuit. It is an example of the control circuit block diagram of a prior art. It is an example of a ground fault. It is an equivalent circuit of an example at the time of a ground fault in a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DC voltage source 2 Inverter circuit 21 U phase switching circuit 22 V phase switching circuit 23 W phase switching circuit 201 P side switching element 202 P side freewheel diode 203 N side switching element 204 P side freewheel diode 3 Permanent magnet type synchronous motor 4 Current detector 5 Control circuit 51 Current controller 52 PWM controller 53 Adder 54 Ground fault determiner 55 Switch

Claims (2)

  There are three sets of a DC voltage source that outputs a DC voltage with one end grounded, and a plurality of series-connected switching elements and free wheel diodes connected between the outputs of the DC voltage source. In an inverter device in which a three-phase permanent magnet type synchronous motor is connected during serial connection, a ground fault occurs when a wiring connecting the permanent magnet type synchronous motor or a coil of the permanent magnet type synchronous motor is grounded. The switching elements between the location where the permanent magnet type synchronous motor is connected and one end of the DC voltage source grounded are all in a conducting state, and all other switching elements are in a shut-off state. A featured inverter device.   2. The inverter device according to claim 1, wherein the detection of the ground fault is performed when the sum of three-phase currents is not zero.

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