JPH11252706A - Power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an induced electromotive voltage which is generated during the free running of a permanent-magnet field synchronous motor from affecting the DC input side of an inverter for driving and controlling the motor, when the motor is used as a railway synchronous motor. SOLUTION: A power converter is provided with a filter capacitor 3, which is charged with a DC voltage inputted from an overhead line through a pantograph 6, an inverter 2A which supplies the DC voltage charged in the capacitor 3 to a permanent-magnet field synchronous motor 7 for driving a railway car after the DC voltage is converted into AC power, and a blocking means which prevents an induced electromotive voltage generated during the free running of the motor 7 from affecting the DC input side of the inverter 2A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter for driving a permanent magnet field synchronous motor for electric railway vehicles, and more particularly, to an overcurrent caused by an induced electromotive force generated in the permanent magnet field synchronous motor during vehicle coasting. The present invention relates to a power conversion device having a function of preventing inflow of air.

[0002]

FIG. 8 is a diagram showing a conventional power converter. In the figure, reference numeral 1 denotes a main body of a power conversion device that converts a DC voltage into three-phase AC power and supplies the power to an induction motor 8 for driving an electric vehicle. The power converter 1 includes an inverter 2 in which three sets of power semiconductor switching elements (for example, GTO) Q having a self-turn-off function are assembled in a three-phase bridge circuit, a filter capacitor 3 that supplies a DC voltage to the inverter 2, and a filter. An overvoltage suppressing circuit for suppressing overcharging of the capacitor, a resistor for discharging an overcharged charge of the filter capacitor in a part of the overvoltage suppressing circuit;
(Hereinafter, referred to as an overvoltage suppression resistor) and a main circuit breaker 8 for disconnecting a circuit at a subsequent stage. Reference numeral 6 denotes a pantograph 6 which takes in DC power from the overhead line and supplies it to the filter capacitor 3. A flywheel diode D is connected to each power semiconductor switching element Q in parallel.

Next, the operation of the conventional power converter will be described. The power converter described here is a device that converts a DC voltage taken from a pantograph 6 into a three-phase AC voltage by an inverter 2 and supplies the three-phase AC voltage to an induction motor 8 for driving. The inverter 2 includes a power semiconductor switching element (for example, GT) having a self-turn-off function.
O) A flywheel diode D is connected in parallel with the element Q and commutates the current.

The inverter 2 forms a three-phase bridge with three sets of power semiconductor switching elements. In this three-phase bridge, two parallel circuits each comprising a power semiconductor switching element Q and a flywheel diode D are connected in series between the high potential and the low potential of the DC circuit for each phase. The inverter output for each phase is supplied to the induction motor 8 from the connection point of each parallel circuit. A DC voltage is stored in the filter capacitor 3 connected to the DC input side of the inverter 2 from the overhead wire through the pantograph 6.

[0005] As shown in FIG. 9, the overvoltage suppression circuit 4 in the power conversion device 1 stores the electric charge stored in the filter capacitor 3 due to the regenerative power from the induction motor 8 or the abnormal rise in the DC voltage supplied from the overhead wire. When the abnormal rise of the DC voltage is detected by the detecting means (not shown), the main circuit breaker 8 is opened and the high potential and the low potential of the DC circuit are short-circuited by the short-circuiting means (not shown). The electric charge stored in the filter capacitor 3 by short-circuiting with the resistor 5 is discharged through the overvoltage suppression resistor 5.

At present, an induction motor, which has many advantages due to its simple structure and robustness, is used as a motor for driving electric railway vehicles. However, the power factor and efficiency are improved as compared with the induction motor. The adoption of a permanent magnet field synchronous motor having features is being studied. Since the permanent magnet field synchronous motor has a brushless structure, it is expected to contribute to maintenance saving.

[0007]

As described above, the use of a permanent magnet field synchronous motor instead of an induction motor as a driving motor for an electric railway vehicle is currently being studied. The electric motor control device for an electric railway vehicle is designed on the assumption that no induced electromotive voltage is generated from the electric motor when the electric railway vehicle coasts (free-runs).

Further, since the conventional overvoltage suppression circuit is designed based on an induction motor which does not generate an induced electromotive voltage in a free-run state, only the electric charge accumulated in the filter capacitor is discharged through the overvoltage suppression resistor 5. Designed based on

[0009] However, in the case of the permanent magnet field synchronous motor 7 in which the rotating field is created by the rotor, which is a permanent magnet, when the inverter is stopped and the motor coasts, an induced electromotive voltage is generated. If you look at, the induced electromotive voltage of the permanent magnet field synchronous motor becomes the external power source

Therefore, when the inverter 2 is stopped when the permanent magnet field synchronous motor is used for driving the electric railway vehicle, the induced electromotive voltage Vac of the motor is parallel to the power semiconductor switching element Q constituting the inverter 2. The current is rectified by the connected and mounted flywheel diode D, and is continuously applied to the filter capacitor 3.

However, the conventional overvoltage suppression circuit is
Because it is designed based on the above-mentioned matter, if overvoltage protection of the filter capacitor against the induced electromotive voltage of the permanent magnet field synchronous motor occurs while the inverter is stopped,
Electric power supplied from the permanent magnet field synchronous motor through the inverter is consumed by the overvoltage suppression resistor, and may burn out the overvoltage suppression resistor. In order to solve such a problem, if an overvoltage suppression resistor having a larger power capacity is provided, or if heat radiating members are arranged, a problem arises in that the entire device becomes large-scale and expensive.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. In the case where a permanent magnet field synchronous motor is used as an electric synchronous motor for an electric railway, an induced electromotive force generated during a free-run state of the electric motor is provided. It is an object of the present invention to obtain a power converter that does not affect the DC input side of the inverter.

[0013]

According to a first aspect of the present invention, there is provided a power conversion device, comprising: a filter capacitor for charging a DC voltage input from a wire through a pantograph; and a DC voltage charged in the filter capacitor to AC power. Inverter that converts and outputs to a permanent magnet field synchronous motor for driving a railway vehicle, and prevents an induced electromotive voltage generated during coasting of the permanent magnet field synchronous motor from affecting the DC input side of the inverter And blocking means for performing the operation.

The blocking means in the power converter according to the second aspect of the present invention is a blocking device that cuts off a connection between an output terminal of the inverter and an input terminal of the permanent magnet field synchronous motor when the operation of the inverter is stopped.

The blocking means in the power converter according to the third aspect of the present invention is a blocking device that cuts off a connection between an input terminal of the inverter and a high potential terminal of the filter capacitor when the operation of the inverter is stopped.

According to a fourth aspect of the present invention, the shutoff device in the power converter is a power semiconductor switching element.

According to a fifth aspect of the present invention, there is provided a power conversion apparatus, wherein the blocking means generates an AC output voltage of the inverter upon detection of coasting of the permanent magnet field synchronous motor, and an induced electromotive force generated upon coasting of the permanent magnet field synchronous motor. Output to level.

According to a sixth aspect of the present invention, there is provided a power conversion device for charging a DC voltage input from an overhead wire through a pantograph, and for converting a DC voltage charged in the filter capacitor into AC power to drive an electric railway vehicle. An inverter that outputs to the permanent magnet field synchronous motor, and when the value of the charging voltage of the filter capacitor exceeds a preset overcharge determination level, both ends of the filter capacitor are short-circuited by a resistor and discharged, And an overvoltage prevention means for increasing an overcharge determination level to be equal to or higher than an induced electromotive voltage level when the operation stop of the inverter is detected.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, an embodiment of the present invention will be described with reference to FIG. In FIG. 7, FIG.
The same reference numerals indicate the same or corresponding parts. In the present embodiment, an input terminal of a permanent magnet field synchronous motor (hereinafter, referred to as a synchronous motor) 7 and an output terminal of each phase of the inverter 2A are connected to a power cutoff switch ( (Cutoff device) Connected via Cu, Cv, Cw. In addition to the normal configuration shown in FIG. 7, the inverter 2A according to the present embodiment includes a means (blocking means) for opening the power cutoff switches Cu, Cv, and Cw when the inverter operation stop is detected.

Next, the operation of this embodiment will be described. Normally, during the inverter operation, the inverter 2 is closed through the power cut-off switches Cu, Cv, and Cw that are closed.
AC power is supplied from A to the synchronous motor 7 to drive the electric train. However, for example, when the electric railway vehicle approaches a downhill slope and shifts to the coasting operation, the inverter 2A switches to the operation stop. Then, the inverter 2A opens the power cutoff switches Cu, Cv, and Cw in accordance with the operation stop switching. As a result, application of the induced electromotive voltage generated in the synchronous motor 7 to the overvoltage suppression circuit (overvoltage prevention means) 4 through the inverter 2A in the power conversion device 1A is suppressed.

Embodiment 2 FIG. In the first embodiment, a mechanical power cutoff switch is used as an induced electromotive force cutoff switch for the power conversion device 1A. However, in the present embodiment, a self-turn-off type diode Du, Dv, Dw is used instead of the power cutoff switch. Is inserted between the input terminal of the synchronous motor 7 and the output terminal of each phase in the inverter 2A.

Hereinafter, this embodiment will be described with reference to FIG. In the drawing, the same reference numerals as those in FIG. 7 indicate the same or corresponding parts. In the present embodiment, between the input terminal of the synchronous motor 7 and the output terminal of each phase of the inverter 2B, a diode Du, whose anode is connected to the output terminal of each phase of the inverter 2B and whose cathode is connected to the input terminal of the synchronous motor 7, is provided. D
Parallel circuits formed by connecting GTO Su, Sv, and Sw, which are kept on during inverter operation, in antiparallel to v and Dw, respectively, are connected in series. In addition, the inverter 2B according to the present embodiment is different from the normal configuration shown in FIG.
Means (blocking means) for outputting a gate turn-off signal to v and Sw are provided.

Next, the operation of this embodiment will be described. Normally, GTO Su, Sv, Sw and the diode D
AC electric power is supplied from the inverter 2B to the synchronous motor 7 through u, Dv, and Dw to drive the electric railway vehicle. But,
For example, when the electric railway vehicle approaches the downhill and shifts to the coasting operation, the inverter 2B switches to the stop operation. Then, the inverter 2B outputs a gate turn-off signal to the GTO Su, Sv, Sw with the switching of the operation stop to turn off the GTO Su, Sv, Sw. As a result, the induced electromotive voltage generated in the synchronous motor 7 is interrupted by the GTO Su, Sv, and Sw, and is applied to the overvoltage suppression circuit 4 of the power converter 1A by the diodes Du, Dv, and Dw. Is quickly prevented, and the on-operation can be quickly started when the inverter operation is restarted.

Embodiment 3 FIG. In the above embodiment, each G
Diodes Du, D for TO Su, Sv, Sw
v and Dw are connected in anti-parallel, respectively.
Instead of u, Dv, and Dw, another GTO is connected in anti-parallel, and a gate turn-on signal is output to all GTOs when the inverter 2B is operating, and a gate turn-off signal is output to all GTOs when the inverter 2B is stopped. The application of the induced electromotive voltage to the power converter 1A may be blocked.

Embodiment 4 In the third embodiment, the synchronous motor 7 and the inverter 2 of the electric power conversion device are used.
Although the case where the GTO as the power semiconductor element is provided between B and B is shown, the same effects as those of the above-described embodiment can be obtained by applying a self-turn-off type power semiconductor element (for example, IGBT) other than the GTO.

Embodiment 5 In the first to fourth embodiments, when the operation of the inverters 2A and 2B is stopped, the synchronous motor 7
Is separated from the inverters 2A and 2B by a mechanical or semiconductor strong switch to prevent the influence of the induced electromotive voltage on the overvoltage suppression circuit 4.

However, in the present embodiment, as shown in the flowchart of FIG. The inverter determines whether or not the inverter is operating by a built-in microcomputer. If it is determined that the inverter is in operation, the maximum value that does not hinder the operation of the inverter is set to the overvoltage suppression circuit 4 as the DC overvoltage protection set value. If the electric charge charged in the filter capacitor 3 exceeds the set maximum value during the operation of the inverter, the overvoltage suppression circuit 4 short-circuits the filter capacitor 3 together with the overvoltage suppression resistor 5 to reduce the electric charge. Discharge.

However, if it is determined that the operation of the inverter is stopped, a voltage value higher than the induced electromotive voltage generated in the synchronous motor 7 is set to the overvoltage suppression circuit 4 as a DC overvoltage protection set value. As a result, the overvoltage suppression circuit 4
Even if an induced electromotive voltage is applied from the synchronous motor 7, its value is lower than the set DC overvoltage protection set value, so that the short-circuit operation of the filter capacitor 3 is not performed. Therefore, the overvoltage suppression resistor 5 is not burned under the influence of the overcurrent due to the induced electromotive force.

Embodiment 6 FIG. In the first to fifth embodiments, the inverter is stopped along with the coasting of the railway vehicle, and the induced electromotive voltage of the synchronous motor 7 generated at the time of coasting is not affected on the overvoltage suppression circuit 4.

However, in the present embodiment, the synchronous motor 7 is quickly started up to the power running operation, the induction electromotive voltage cut-off mechanism is not required, and the inverter 2C is not stopped due to the coasting of the electric railway vehicle. When coasting starts,
Inverter 2C generates induced electromotive voltage V generated in synchronous motor 7
Inverter output voltage V _IVN (V _{I VN}
= Vac). As a result, the induced electromotive voltage Vac becomes equal to the inverter output voltage V _IVN , causing no potential difference, and the three-phase AC current Iac does not flow from the synchronous motor 7 to the inverter 2C.

Embodiment 7 In the first and second embodiments, the breaking means is provided between the line between the input terminal of the synchronous motor and the output terminal of the inverter. In this embodiment, the high potential side of the inverter and the high potential side of the filter capacitor 3 are connected. A disconnecting means is provided between the connecting lines.

FIG. 5 shows a power converter 1 according to the present embodiment.
D. The power conversion device 1D includes a power cutoff switch C that maintains a closed state between the line connecting the high potential side of the inverter 2D and the high potential side of the filter capacitor 3 when the synchronous motor 7 is normally operated. Are connected in series. In addition, the inverter 2D in the present embodiment includes a means (blocking means) for opening the power cutoff switch C when the inverter operation stop is detected, in addition to the normal configuration shown in FIG.

Next, the operation of this embodiment will be described. Normally, during inverter operation, DC power is input from the filter capacitor 3 to the inverter 2D through the power cutoff switch C which is in a closed state, where it is converted into AC power and supplied to the synchronous motor 7 to operate the electric railway vehicle.

However, for example, when the electric railway vehicle approaches a downhill slope and shifts to the coasting operation, the inverter 2D switches to the stop operation. Then, the inverter 2A opens the power cutoff switch C with the switching of the operation stop. As a result, even if the induced electromotive voltage generated in the synchronous motor 7 is converted into a DC voltage by the inverter 2D, it is prevented from being applied to the overvoltage suppression circuit 4.

Embodiment 8 FIG. In the above embodiment, a mechanical shut-off mechanism is provided between the line between the input terminal of the synchronous motor and the output terminal of the inverter, but in the present embodiment, the high potential side of the inverter and the high potential side of the filter capacitor 3 are connected. A power semiconductor switching element is provided between connected lines.

FIG. 6 shows a power converter 1 according to the present embodiment.
E. This power conversion device 1E is a self-turn-off type of power that maintains an off state when the synchronous motor 7 is operating normally between a line connecting the high potential side of the inverter 2E and the high potential side of the filter capacitor 3. Semiconductor switching element (for example, GTO) S1 and diode D1
Are connected in series. The diode D1 is connected in the forward direction in the direction of the direct current flowing from the filter capacitor 3 to the inverter 2E. The power semiconductor switching element S1 is connected in parallel to the diode D1 in the reverse direction.

The inverter 2E according to the present embodiment is provided with a means for outputting a gate-off signal to the power semiconductor switching element S1 when the inverter operation stop is detected, in addition to the normal configuration shown in FIG. Next, the operation of the present embodiment will be described. Since the power semiconductor switching device S1 is in the ON state during the inverter operation, the regenerative power of the synchronous motor 7 is rectified by the flywheel diode of the inverter 2E and then sent to the pantograph 6 through the power semiconductor switching device S1. From there it is returned to the overhead line. During power running operation, DC power is input from the filter capacitor 3 to the inverter 2E through the diode D1, where it is converted into AC power and supplied to the synchronous motor 7.

However, for example, when the railway vehicle approaches a downhill slope and shifts to the coasting operation, the inverter 2E switches to the stop operation. Then, the inverter 2E switches the power semiconductor switching element S1 with the operation stop switching.
And output a gate turn signal to turn off. As a result, even if the induced electromotive voltage generated in the synchronous motor 7 is converted into a DC voltage by the flywheel diode of the inverter 2E, it is prevented from being applied to the overvoltage suppression circuit 4.

Embodiment 9 Although the seventh embodiment has described the case where the power semiconductor switching element GTO is provided between the inverter 2E and the filter capacitor 3, the self-turn-off type power semiconductor element, for example, an IGBT may be applied. Often, the same effects as those of the above embodiment can be obtained. Furthermore, instead of diodes connected in parallel, power semiconductor elements (GTO, MOSFE)
(T, IGBT) has the same effect.

Embodiment 10 FIG. In all of the above embodiments, even if the power supply voltage supplied from the overhead wire through the pantograph 6 is an AC voltage, and the AC / DC power converter is provided between the AC voltage source and the power converter, the power converter is If the input is DC power, it is needless to say that each of the above embodiments can be applied to this power converter, and the same effects as those of the embodiments can be obtained.

Embodiment 11 FIG. In each of the above embodiments, it is obvious that the inverter can be used not only for the two-level inverter shown in FIGS. 8 and 9 but also for the three-level neutral point clamp type inverter shown in FIG. . In the case of such an inverter circuit, 2 connected in series
A series circuit of an overvoltage suppression circuit 4 and an overvoltage suppression resistor 5 is connected in parallel to one filter capacitor. Therefore, the operation of the overvoltage suppression operation is not different from the operation of each of the above embodiments.

[0042]

According to the first aspect of the present invention, a filter capacitor for charging a DC voltage input through a pantograph from an overhead wire, and a DC voltage charged in the filter capacitor is converted to AC power to drive an electric vehicle. An inverter that outputs to the permanent magnet field synchronous motor, and blocking means that prevents an induced electromotive voltage generated when the permanent magnet field synchronous motor coasts from affecting the DC input side of the inverter. Therefore, there is an effect that the drive control of the permanent magnet field synchronous motor can be performed by the conventional power converter that drives and controls the induction motor.

According to the second aspect of the present invention, the blocking means is a breaking device for breaking the connection between the output terminal of the inverter and the input terminal of the permanent magnet field synchronous motor when the operation of the inverter is stopped. There is an effect that the voltage can be prevented from affecting the DC input side of the inverter.

According to the third aspect of the present invention, the blocking means is a breaking device for breaking the connection between the input terminal of the inverter and the high potential terminal of the filter capacitor when the operation of the inverter is stopped. Since there is no need to provide a shut-off device, the device can be downsized.

According to the fourth aspect of the present invention, since the shutoff device is a power semiconductor switching element, there is an effect that the shutoff operation for applying the induced electromotive voltage can be accelerated.

According to the fifth aspect of the present invention, the blocking means sets the induced voltage level at which the AC output voltage of the inverter is generated during coasting of the permanent magnet field synchronous motor when the coasting of the permanent magnet field synchronous motor is detected. Since the output is performed in this manner, there is no need to stop the operation of the inverter when the coasting is detected, so that there is an effect that the operation of the permanent magnet field synchronous motor can be quickly restarted.

According to the sixth aspect of the present invention, a filter capacitor for charging a DC voltage input through a pantograph from an overhead wire, and a DC voltage charged in the filter capacitor is converted into AC power to be used for driving a railway vehicle. An inverter that outputs to the magnet field synchronous motor and, when the value of the charging voltage of the filter capacitor exceeds a preset overcharge determination level, short-circuits both ends of the filter capacitor with a resistor to discharge; Since the overvoltage preventing means for increasing the overcharge determination level to the level of the induced electromotive voltage at the time of detecting the stoppage of the inverter is provided, the effect of the induced electromotive voltage on the overvoltage preventing means can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating that a power cutoff switch is provided between a synchronous motor and an inverter according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating that a power semiconductor element is provided between a synchronous motor and an inverter according to a second embodiment of the present invention.

FIG. 3 is a diagram illustrating switching of a DC overvoltage protection set value according to a fourth embodiment of the present invention.

FIG. 4 is a diagram for explaining that an inverter is coasted by maintaining Vinv = Vac without stopping an inverter according to Embodiment 5 of the present invention.

FIG. 5 is a diagram illustrating that a power cutoff switch is provided between an inverter and a filter capacitor according to a sixth embodiment of the present invention.

FIG. 6 is a diagram illustrating that a power semiconductor element is provided between an inverter and a filter capacitor according to a seventh embodiment of the present invention.

FIG. 7 is a diagram showing a circuit configuration of a three-level inverter (neutral point clamp type inverter) applicable in each of the above embodiments.

FIG. 8 is a diagram showing a conventional power converter.

FIG. 9 is a diagram illustrating that an induced electromotive voltage of the synchronous motor is diode-rectified and applied to a filter capacitor, and power is consumed by an overvoltage suppression resistor due to overvoltage protection.

[Explanation of symbols]

1A to 1E power conversion device, 2A to 2E inverter,
3 Filter capacitor, 4 Overvoltage suppression circuit, 5 Overvoltage suppression resistor, 6 Pantograph, 7 Permanent magnet field synchronous motor, C, C _{U to} C _W power cutoff, D1, D _{U to} D _W
Diodes, S1, S _U -S _W power semiconductor switching elements (GTO).

Claims (6)

[Claims] 1. A filter capacitor for charging a DC voltage input through a pantograph from an overhead wire, and a DC voltage charged in the filter capacitor is converted into AC power and output to a permanent magnet field synchronous motor for driving an electric vehicle. And an inverter for preventing an induced electromotive voltage generated during coasting of the permanent magnet field synchronous motor from affecting the DC input side of the inverter. 2. The electric power according to claim 1, wherein the blocking means is a breaking device for breaking a connection between an output terminal of the inverter and an input terminal of the permanent magnet field synchronous motor when the operation of the inverter is stopped. Conversion device. 3. The power converter according to claim 1, wherein the blocking means is a breaking device that cuts off a connection between an input terminal of the inverter and a high potential terminal of the filter capacitor when the operation of the inverter is stopped. 4. The power converter according to claim 2, wherein the shut-off device is a power semiconductor switching element. 5. The blocking means outputs the AC output voltage of the inverter when the coasting of the permanent magnet field synchronous motor is detected as an induced electromotive voltage level generated when the permanent magnet field synchronous motor coasts. The power conversion device according to claim 1. 6. A filter capacitor for charging a DC voltage input through a pantograph from an overhead wire, and a DC voltage charged in the filter capacitor is converted into AC power and output to a permanent magnet field synchronous motor for driving an electric vehicle. When the value of the charging voltage of the inverter and the filter capacitor exceeds a preset overcharge determination level, both ends of the filter capacitor are short-circuited by a resistor to discharge, and when the operation stop of the inverter is detected, An electric power converter, comprising: an overvoltage prevention unit that increases a charge determination level to a level equal to or higher than an induced electromotive voltage level.