JP4269197B2 - A drive device for a permanent magnet motor for an electric vehicle. - Google Patents

Description

【００１７】
【発明の効果】
この発明によれば、下記のような効果を期待することができる。
１）電動機の惰行運転中の無負荷誘起電圧によってピーク充電される部位が限定され、かつ、その電圧も安定していることから、適切な電圧定格の素子，部品を適用することで、電動機の無負荷誘起電圧による過電圧の対策が容易となる。
２）電動機の惰行運転中の無負荷誘起電圧が電源側に回生されることがないため、不必要なブレーキ力が発生しない。
３）惰行運転中に停止しているインバータを起動する場合でも、インバータ起動および電動機巻線の初期励磁に必要な電力を負荷側の高電圧を阻止した状態で供給できるため、容易に起動することができる。
【図面の簡単な説明】
【図１】この発明の実施の形態を示す構成図である。
【図２】図１の動作を説明するための状態遷移図である。
【図３】第１の従来例を示す構成図である。
【図４】界磁弱め制御の説明図である。
【図５】第２の従来例を示す構成図である。
【符号の説明】
１…電源(架線)、２…パンタグラフ、３…遮断器、４…フィルタリアクトル、５…永久磁石電動機(ＰＭ)、６…断路器、７…開閉手段、８…一方向の導通手段、９…交流電動機、１０…インバータ、１１〜１６…半導体電力変換素子、２１〜２６…フリーホイーリングダイオード、３０…フィルタコンデンサ(主コンデンサ)、３１〜３３…スナバコンデンサ、４０…制御装置。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a permanent magnet motor driving apparatus suitable for use in a case where a permanent magnet motor is provided, such as a railway vehicle or an electric vehicle, and coasting operation is sometimes performed.
[0002]
[Prior art]
In recent years, electric vehicles have been put into practical use as an approach to environmental problems such as global warming caused by carbon dioxide and air pollution. Also, in the railway vehicles, AC motor drive systems using VVVF inverters are becoming mainstream from the viewpoints of energy saving and maintenance reduction.
FIG. 3 shows a conventional example of an AC motor (induction motor) drive system.
In the figure, 1 is a power source (overhead wire), 2 is a pantograph, 3 is a circuit breaker, 4 is a filter reactor, 9 is an AC motor, 10 is a power conversion element 11-16 such as an IGBT (insulated gate bipolar transistor), and a free An inverter composed of wheeling diodes 21 to 26, 30 is a filter capacitor, and 31 to 33 are snubber capacitors.
[0003]
That is, the DC power supplied from the overhead wire 1 or the battery is converted into AC power of variable voltage variable frequency (VVVF) by the inverter 10 including the semiconductor power conversion elements 11 to 16 and the diodes 21 to 26, and the AC motor 9 is Variable speed drive. A normal induction motor is used as the AC motor 9, and the generated torque and terminal voltage of the motor are controlled by adjusting the excitation current component and torque current component based on so-called vector control.
[0004]
Electric motors applied to these drive systems need to generate large torque at low speeds, but at the same time, it is essential that they be small and light. I try to make up for the lack of torque.
Research and development of drive systems for automobiles and trains using permanent magnet synchronous motors (hereinafter also abbreviated as PM motors), which are easy to generate low-speed torque and excellent in energy efficiency due to high performance of rare earth magnets in recent years. Has become popular.
[0005]
In the case of a PM motor, since the magnetic flux generated by the permanent magnet is constant, an induced voltage proportional to the product of the magnetic flux density and the rotational speed of the motor is generated as a characteristic of the motor alone. This is called a no-load induced voltage and has a characteristic as shown by a dotted line in FIG. On the other hand, since the inverter cannot generate a voltage higher than the input DC voltage, in the region where the no-load induced voltage exceeds the maximum output voltage of the inverter, a magnetic flux that cancels the magnetic flux generated by the permanent magnet is applied to the armature. The so-called field weakening control generated by the winding is performed, and operation up to high speed is performed (see the solid line in FIG. 4).
[0006]
In automobiles and trains, driving (coasting) by inertia without acceleration or deceleration by the drive system is a major feature of the driving mode. In such a case, the drive system using the PM motor generates a no-load induced voltage as described above, and in a region where the no-load induced voltage is larger than the DC voltage of the inverter (corresponding to the voltage across the capacitor 30), The induced voltage of the PM motor is full-wave rectified via diodes 21 to 26 connected in reverse parallel to the semiconductor power conversion elements 11 to 16 to increase the DC intermediate voltage (voltage across the capacitor 30) or to the power source side 1. Electric power is regenerated, and the entire drive system performs a braking operation.
[0007]
For this reason, in motor vehicles and train drive systems using PM motors, an excitation current for field weakening control is always applied so that the terminal voltage of the PM motor becomes a constant level regardless of acceleration / deceleration / coasting, Alternatively, as shown in the system configuration of FIG. 5, a disconnector 6 is provided between the output of the inverter 10 and the terminal of the PM motor 5, and the no-load induced voltage of the PM motor 5 is the output terminal of the inverter 10 when the inverter is stopped (coasting). So that it is not directly applied.
[0008]
[Problems to be solved by the invention]
When an inverter is operated to flow an exciting current for field weakening control while a train or automobile is coasting, copper loss or inverter conversion loss caused by current flowing in the winding of the PM motor occurs. It is not preferable from the viewpoint of energy saving. In particular, it is a fatal problem in an electric vehicle in which energy efficiency is the most important issue.
In the method shown in FIG. 5 in which the disconnector 6 is opened during coasting, no power loss or unnecessary braking force is generated during coasting, but inverter operation is performed to accelerate or decelerate again from the coasting state. When restarting, it is necessary to close the disconnector 6.
[0009]
However, closing the disconnector 6 while the PM motor 5 rotates at a high speed means that an excessive no-load induced voltage of the PM motor 5 is applied to the elements 11 to 16 and 21 to 26 constituting the inverter 10 at once. Further, there is a possibility that the riding comfort is adversely affected by the destruction of the semiconductor power conversion element due to a rapid voltage rise or the shock of the traveling speed due to the rapid power regeneration of the no-load induced voltage. For this reason, once the disconnector 6 is opened, the disconnector 6 is closed until the train or automobile decelerates and the excessive no-load induced voltage of the PM motor 5 drops below the output voltage of the inverter 10. (Continuity) and the restart of inverter operation must be waited, causing a problem that it is not practical. Furthermore, the disconnector is not required in the conventional induction motor drive system as shown in FIG. 3, whereas in FIG. 5, the cost, mass and size increase due to the increase in the number of parts, and maintenance is due to the contact parts. There was also a problem in terms of reliability.
Accordingly, an object of the present invention is to facilitate measures against overvoltage due to no-load induced voltage of an electric motor and restart of an inverter without increasing the number of parts.
[0010]
[Means for Solving the Problems]
In order to solve such problems, in the present invention, a parallel connection circuit of a one-way conduction means and an opening / closing means is inserted in series between the inverter power supply and the inverter arm, and the permanent magnet type synchronous motor is driven through the inverter. A driving device for
While the inverter is stopped, open the opening and closing means,
The excitation current is controlled so that the terminal voltage of the motor becomes a predetermined value while the switching means is opened at the start of the inverter operation, and the switching means is closed when the terminal voltage of the motor reaches a predetermined value. In such a state, the torque current of the motor is controlled and the motor is accelerated / decelerated,
When stopping the inverter during operation, the torque current is reduced to zero while controlling the excitation current so that the terminal voltage of the electric motor becomes a predetermined value, then the switching means is opened, and then the excitation current Is reduced to stop the operation of the inverter.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing an embodiment of the present invention.
As can be seen from FIG. 3, the switching means 7 such as a switch and the one-way conduction means 8 such as a diode are connected in series between the main capacitor 30 and the inverter 10 as shown in FIG. The feature is that a parallel circuit is inserted. The conducting means 8 conducts in the direction in which power is supplied from the power source 1 side to the inverter 10 when the drive system performs an acceleration operation.
Reference numeral 40 denotes a control device that performs on / off control of the inverter 10 and the opening / closing means 7 according to a predetermined algorithm (for example, for vector control of an AC motor). Note that description of detection of various amounts including voltage and current necessary for control, supply of a gate signal to the IGBT, and the like is omitted.
[0012]
When the inverter operation is stopped, the control device 40 opens the opening / closing means 7 so that the capacitors 31 to 33 for each phase of the inverter arm are connected to the PM via the freewheeling diodes 21 to 26 at that time. The so-called peak charge is performed up to the no-load induced voltage generated by the motor 5, but this voltage is a finite voltage determined by the various characteristics and rotational speed of the PM motor, and is relatively stable that is full-wave rectified by the diodes 21 to 26. Since it is a voltage, it can fully cope with by selecting appropriately the voltage rating of the semiconductor elements 11-16 and the capacitors 31-33.
[0013]
Further, since the no-load induced voltage is interrupted from the power source 1 side by the unidirectional conduction means 8 of the electric power, generation of useless braking force generated by regenerating the no-load induced voltage during coasting operation to the power source side The loss of energy accompanying it can be prevented. Further, since the voltage on the power supply side from the conduction means 8 in one direction of power does not rise above the normal power supply voltage, the filter capacitor 30 requiring a large capacity can be applied with a normal voltage rating. In addition, there is no possibility that the overvoltage causes an electrical product outside the drive system. Further, the voltage of the snubber capacitors 31, 32 and 33 attached to each arm of the inverter rises by so-called peak charging, so it is necessary to take a high rated voltage. It is relatively easy.
[0014]
When the inverter operation is resumed while the PM motor 5 is rotating, the inverter operation is resumed with the opening / closing means 7 being opened by the control device 40, the active power (torque current) component remains zero, and the reactive power (excitation current). Only the components are controlled so that the terminal voltage of the PM motor becomes a predetermined value. As a result, the magnetic flux of the PM motor 5 is weakened and the induced voltage is lowered, and the charges charged in the capacitors 31 to 33 are consumed by the switching loss of the inverter operation during this period and the copper loss of the winding of the PM motor 5. Will drop. If the loss at this time exceeds the excess of the charging voltage of the capacitors 31 to 33 with respect to the power supply voltage, the power is supplied from the power supply side 1 through the one-way conduction means 8. Thereafter, by closing the opening / closing means 7, a normal driving operation can be started regardless of the driving (power running) / regenerative (braking) operation.
In the case of regenerative (braking) operation, load current is regenerated from the PM motor 5 to the power source 1 via the inverter 10, but the torque current component is set to zero while the opening / closing means 7 is open as described above. By controlling, the voltage rise due to the regenerative operation does not occur even when the opening / closing means 7 is closed.
[0015]
The above operation is shown in a state transition diagram as shown in FIG. 1 is always applied, and the switch 3 is always closed. V _PM and V _INV represent the induced voltage of the PM motor and the output voltage of the inverter, respectively.
(1) Mode 1: Initial state (2) Mode 2: The control device 40 opens the opening / closing means 7. As a result, the voltage of the capacitor 30 matches the overhead wire voltage 1 regardless of the operating state of the PM motor 5 and the presence or absence of the no-load induced voltage.
{Circle around (3)} Mode 3: Prior to the inverter operation, the control device 40 operates the inverter 10 with the opening / closing means 7 open, and controls the excitation current so that the terminal voltage of the PM motor 5 becomes a predetermined level. At this time, if the induced voltage of the PM motor 5 is equal to or lower than the output voltage of the inverter 10, the power loss accompanying the flow of the excitation current is supplied from the power source 1 side through the unidirectional conduction means 8 of the power. Further, when the induced voltage of the PM motor 5 exceeds the output voltage of the inverter 10, the power loss due to the excitation current flowing is the energy charged in the capacitors 31 to 33 provided in each arm of the inverter 10 or the power The voltage is supplied from the power supply side through the one-way conduction means 8 and the voltages of the capacitors 31 to 33 and the induced voltage of the PM motor 5 are controlled to predetermined voltages.
[0016]
(4) Mode 4: The control device 40 confirms that the induced voltage of the PM motor 5 has reached a predetermined level, and closes (connects) the opening / closing means 7.
{Circle around (5)} Mode 5: The control device 40 starts control of the current corresponding to the torque of the PM motor 5 so as to obtain a predetermined acceleration torque or deceleration torque.
{Circle around (6)} Mode 6: When the acceleration or deceleration operation is completed, the control device 40 decreases the current for torque while controlling the excitation current of the inverter 10 so that the terminal voltage of the PM motor 5 is maintained at a predetermined level. .
{Circle around (7)} Mode 7: When the torque component current becomes zero, the controller 40 opens the switching means 7 and decreases the excitation current. When the excitation current becomes zero, the operation of the inverter 10 is terminated.
Table 1 shows the above.
[Table 1]

[0017]
【The invention's effect】
According to the present invention, the following effects can be expected.
1) The peak charged part is limited by the no-load induced voltage during coasting operation of the motor, and the voltage is also stable. By applying elements and parts with appropriate voltage ratings, This makes it easy to take measures against overvoltage caused by no-load induced voltage.
2) Since no-load induced voltage during coasting operation of the motor is not regenerated to the power source side, unnecessary braking force is not generated.
3) Even when starting an inverter that is stopped during coasting operation, the power necessary for starting the inverter and initial excitation of the motor winding can be supplied in a state where the high voltage on the load side is blocked, so it can be started easily Can do.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an embodiment of the present invention.
FIG. 2 is a state transition diagram for explaining the operation of FIG. 1;
FIG. 3 is a block diagram showing a first conventional example.
FIG. 4 is an explanatory diagram of field weakening control.
FIG. 5 is a block diagram showing a second conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Power supply (overhead wire), 2 ... Pantograph, 3 ... Circuit breaker, 4 ... Filter reactor, 5 ... Permanent magnet motor (PM), 6 ... Disconnector, 7 ... Opening / closing means, 8 ... One-way conduction means, 9 ... AC motor, 10 ... inverter, 11-16 ... semiconductor power conversion element, 21-26 ... freewheeling diode, 30 ... filter capacitor (main capacitor), 31-33 ... snubber capacitor, 40 ... control device.

Claims (1)

A drive device for driving a permanent magnet synchronous motor through an inverter by inserting a parallel connection circuit of a one-way conduction means and an opening / closing means in series between a power source of the inverter and an inverter arm,
While the inverter is stopped, open the opening and closing means,
The excitation current is controlled so that the terminal voltage of the motor becomes a predetermined value while the switching means is opened at the start of the inverter operation, and the switching means is closed when the terminal voltage of the motor reaches a predetermined value. In such a state, the torque current of the electric motor is controlled to accelerate and decelerate the electric motor,
When stopping the inverter during operation, the torque current is reduced to zero while controlling the excitation current so that the terminal voltage of the electric motor becomes a predetermined value, then the switching means is opened, and then the excitation current The drive device for a permanent magnet motor for an electric vehicle is characterized in that the operation of the inverter is stopped by reducing the motor.

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