JP2845093B2 - AC electric vehicle control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an AC electric vehicle, and more particularly to a control device having a converter and an inverter for driving and controlling an induction motor with a variable voltage and a variable frequency.

[0002]

2. Description of the Related Art FIG. 2 shows, for example, “The 27th National Symposium on Use of Cybernetics in Railways”, 199
November 1st, P.S. It is a circuit diagram which shows the structure of the control apparatus of the conventional AC electric vehicle published by 179-183. In the figure, 1 is an AC overhead wire, 2 is a pantograph which comes into contact with the AC overhead wire 1 and takes in an AC voltage, 3 is a main transformer whose primary winding is connected to the pantograph 2 and a grounding portion, and 4 is a main transformer. A converter connected to the secondary winding of the transformer 3 for converting an AC input voltage to a DC output voltage,
Is an inverter connected to the smoothing capacitor 5 and converting the DC voltage into an AC output voltage having a variable voltage variable frequency (VVVF) and supplying the AC output voltage to the three-phase induction motor. 8 is a smoothing capacitor 5
, That is, a DC output voltage of the converter 4 (input voltage of the inverter 6).
Reference numeral 9 denotes a rotation detector for detecting the rotation speed (frequency) of the induction motor 7.

[0003] Reference numeral 10 denotes an output voltage command circuit for generating an output voltage command 11 of the converter 4, and 12 compares the output voltage command 11 with a DC voltage detection value 13 from the DCVD 8 to control the output voltage of the converter 4 to be constant. A converter control circuit 15 for sending a converter control command 14 for detecting the DC voltage 13 and the frequency detection value 1 from the rotation detector 9
6 is an inverter control circuit for sending an inverter control command 17 for controlling the output voltage and frequency of the inverter 6.

Next, the operation will be described. The converter control circuit 12 feeds back the DC voltage detection value 13 from the DCVD 8 and performs constant voltage control so that the DC output voltage of the converter 4 becomes a constant output voltage command value irrespective of fluctuations in the voltage and load of the AC overhead wire 1. Inverter control circuit 1
5 starts operation when the converter output voltage, that is, the inverter input voltage reaches a constant value, sends a gate signal to the main circuit semiconductor element of the inverter 6 by a so-called PWM method, and outputs an AC output of a variable voltage variable frequency to the induction motor 7. Supply to perform smooth drive control.

Here, the control of the induction motor is based on V / f (output voltage / output frequency) constant control. In a low speed range from a low output voltage range to a maximum rated motor voltage, a modulation mode is used. The inverter input voltage is reduced, and the output voltage is increased in proportion to the increase in speed (frequency). That is, variable voltage variable frequency (VVVF) control is performed. Then, in the high speed region after the motor rated voltage is reached, the mode shifts from the modulation mode to the so-called one-pulse mode,
A constant voltage variable frequency (CVVF) control of AC output voltage effective value = DC input voltage × √6 / π is performed.

[0006]

Since the conventional control device for an AC electric vehicle is configured as described above, if the operation in the low speed range in which the input voltage is reduced and output in the modulation mode is continued for a long time, In addition, the switching loss of the main circuit semiconductor element of the inverter 6 and the increase of the loss of the snubber circuit which are determined by the modulation switching frequency cause overheating of these parts and lead to a burnout, or the operation of the apparatus is stopped by the overheat detection protection operation. There was a point. Also, when the above components and the cooling system are designed in consideration of the continuous operation in the low speed range,
The device is correspondingly larger and the weight is increased.

[0007] The present invention has been made to solve the above problems, and without increasing the size of the apparatus.
Moreover, an object of the present invention is to provide a control device for an AC electric vehicle that does not increase switching loss and the like.

[0008]

According to the present invention, there is provided a control apparatus for an AC electric vehicle according to the present invention, wherein a constant-speed operation command is input or a continuous operation time in the modulation mode is predetermined while the inverter is operating in the modulation mode. Means are provided for reducing the DC output voltage of the converter by a predetermined amount when the value is exceeded.
In this case, the DC output voltage of the converter may be reduced until the operation mode of the inverter becomes the one-pulse mode.

[0009]

When the input voltage of the inverter decreases during the modulation mode, the inverter operates in the direction of reducing the voltage drop by the modulation mode control to maintain the output voltage. Therefore, the mode shifts from the modulation mode to the one-pulse mode depending on the amount of decrease in the input voltage. By the above operation shift, the switching loss of the main circuit semiconductor element of the inverter and the loss of the snubber circuit are reduced.

[0010]

[Embodiment 1] FIG. 1 is a circuit diagram showing a configuration of an AC electric vehicle control device according to Embodiment 1 of the present invention. It is provided with a constant-speed operation command circuit 18, and when a constant-speed operation command 19 is issued, it is sent to the output voltage command circuit 10 and the inverter control circuit 15 to change control. Hereinafter, the operation of this point will be mainly described.

When the constant speed operation command 19 is input, the output voltage command circuit 10 changes the output voltage command 11 sent to the converter control circuit 12. For example, the modulation rate = 0.
8, when the constant speed operation command 19 is input when the inverter 6 is operating at a speed of about 80% of the speed at the rated voltage of the motor when the AC output voltage of the inverter 6 is operating. Voltage command circuit 10 has an output voltage command value 11
Is reduced by a factor of 0.8. Accordingly, converter control circuit 12 performs constant voltage control so that DC voltage detection value 13 from DCVD 8 matches this reduced output voltage command value 11.

The inverter control circuit 15 changes the modulation factor from 0.8 to 1.0, that is, shifts from the modulation mode up to that time to the one-pulse mode with the decrease of the inverter input voltage, and sets the maximum to the input voltage. The inverter control command 17 is changed to output an AC voltage. In the above case, although the inverter input voltage decreases, the modulation rate of the inverter 6 increases and compensates for the decrease, and the AC output voltage equivalent to the conventional one is supplied to the induction motor 7, and the driving characteristics of the electric vehicle are reduced. Has no effect.

In the first embodiment, as described above, when the constant speed operation command 19 is input, the inverter 6 changes from the modulation mode to the one-pulse mode, and the switching frequency of the inverter 6 is greatly reduced. The switching loss of the circuit semiconductor element and the generation loss of the snubber circuit are greatly reduced. Therefore, even if the constant-speed operation command 19 is continuously issued for a long time, the semiconductor element and the like can be stably operated without overheating.

It should be noted that the constant speed operation command 1
When 9 is released and a command to accelerate further is input,
The output voltage command 11 is increased again to the original value, and the converter control circuit 12 returns to the original constant voltage control for maintaining the converter output voltage at the value before reduction.

Embodiment 2 FIG. In the present invention, the DC output voltage of the converter is reduced when the constant speed operation command 19 is input. In the first embodiment, however, the DC output voltage is reduced by changing the modulation factor of the inverter to 1.0, that is, 1.0. Although the reduction is performed until the one-pulse mode is set, the DC output voltage may be reduced within the range of the modulation mode operation, and the inverter output voltage may be controlled to be constant in this state. In the snubber circuit and the like of the inverter, even if the input voltage is reduced, the generated loss is considerably reduced, and the effect of suppressing overheating can be expected.

Embodiment 3 FIG. In the first embodiment, the operation of reducing the DC output voltage of the converter 4 is performed when the constant speed operation command 19 is input. However, the continuous operation time during the modulation mode operation is detected, and the operation is performed. The DC output voltage may be reduced when the duration exceeds a certain value. This may occur, for example, when traveling on a long distance section of an uphill slope.

[0017]

As described above, according to the present invention, the means for reducing the DC output voltage of the converter is provided when the operation in the modulation mode of the inverter continues for a certain period of time or more. Without increasing the size of the components of the inverter, overheating is suppressed and reliability is improved. Also, the hand in the above, to reduce the DC output voltage of the converter to such an extent that the modulation mode shifts to the one-pulse mode
By providing a step, it is possible to further reduce the occurrence loss of the components.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating a configuration of a control device for an AC electric vehicle according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a conventional control device for an AC electric vehicle.

[Explanation of symbols]

 Reference Signs List 1 AC overhead line 4 Converter 6 Inverter 7 Induction motor 11 Output voltage command 12 Converter control circuit 13 DC voltage detection value 14 Converter control command 15 Inverter control circuit 16 Frequency detection value 17 Inverter control command

Claims (2)

(57) [Claims] [Claim 1 further comprising an inverter for supplying to the converter and a DC voltage from the converter for converting an AC input voltage into a predetermined DC output voltage into a predetermined AC output voltage motor, the inverter, the low output A control device for an AC electric vehicle that performs variable voltage variable frequency control in a modulation mode from a voltage range to a maximum output voltage in a one-pulse mode and performs constant voltage variable frequency control in a one-pulse mode at the maximum output voltage. Means for reducing the DC output voltage of the converter by a predetermined amount when a constant speed operation command is input or the continuous operation time in the modulation mode exceeds a predetermined value during operation in the modulation mode. A control device for an AC electric vehicle, characterized in that: 2. A converter for converting an AC input voltage to a predetermined DC output voltage, and an inverter for converting the DC voltage from the converter to a predetermined AC output voltage and supplying the same to a motor, wherein the inverter has a low output. A control device for an AC electric vehicle that performs variable voltage variable frequency control in a modulation mode from a voltage range to a maximum output voltage in a one-pulse mode and performs constant voltage variable frequency control in a one-pulse mode at the maximum output voltage. During the operation in the modulation mode, when a constant speed operation command is input or the continuous operation time in the modulation mode exceeds a predetermined value, the DC output voltage of the converter is changed to the operation mode of the inverter. A control device for an AC electric vehicle, comprising: means for reducing the current to a one-pulse mode.