JPS6130482B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high power factor operation system for an AC electric vehicle that uses a thyristor conversion device to control a shunt-wound or compound-wound electric motor.

When operating an electric car that uses a DC motor with an AC power supply, for example, a thyristor converter is used to convert AC to DC, and at the same time performs phase control to vary the DC voltage and control the voltage applied to the motor. A method is used. In addition, in order to economically extend the operating speed to a high speed range, so-called weak field control is generally used to weaken the field. This characteristic is illustrated in Figure 1. In the low speed range, the armature applied voltage is controlled by phase control of the thyristor converter, and during this period, the field current is kept constant, so-called constant torque control, and the armature applied voltage is If the voltage is constant and the field current is controlled to be constant, for example, the armature current is constant in the high speed range from a predetermined value, this area becomes constant output control.

On the other hand, the power factor of the vehicle is determined mostly by the power factor of the thyristor converter for the armature current, since the power required for the field is very small compared to that of the armature.
In order to improve the power factor of the vehicle, it is sufficient to improve the power factor of the armature current thyristor conversion device. However, the power factor of a thyristor conversion device that performs phase control improves as the firing phase angle decreases, and the best value is theoretically 0.9 in a single-phase circuit and 0.955 in a three-phase circuit with full conduction. is well known. For this reason, in terms of vehicle control, the phase control range is set low and the weak field range is set wide, thereby reducing the amount of time the vehicle runs at a low power factor.

However, in the past, it was not possible to advance the armature current thyristor converter to full conduction even during weak field control, and the minimum firing phase angle was usually set at about 30 to 40 degrees. The reason for this is that in order to shift from the phase control range to weak field control, the output voltage of the thyristor converter is detected and switched to the voltage control system, so the accuracy and stability of the voltage control system are affected. This is because the input voltage fluctuation of the thyristor converter device that is used must be taken into account.

As a result, the power factor of the vehicle has to be low, and if you want to improve the power factor, you have no choice but to rely on external elements such as phase advance capacitors, which tends to make the power factor large and expensive. Ta.

In view of the above-mentioned points, it is an object of the present invention to provide a high power factor operation method for an AC electric vehicle that has these conventional drawbacks and can obtain a high power factor without requiring any external elements. It is.

The present invention will be explained below based on the drawings of the embodiments.
FIG. 2 is a control block diagram showing one embodiment of the system of the present invention. In the figure, when a predetermined command is input from the armature current command device 1 to the amplifier 2, the armature current thyristor conversion device 3 supplies current to the armature 4 of the motor, and detects the armature current. The signal is detected by the amplifier 5 and fed back negatively to the amplifier 2, so that so-called closed loop control is performed. On the other hand, the field current is inputted from the field current command device 6 to the amplifier 7, the current is supplied to the field winding 9 of the motor through the field current thyristor converter 8, and the field current is detected by the current detector 10. It is detected and fed back negatively to the amplifier 7 to perform closed loop control.

Here, in a range where the rotation speed of the motor is low, the induced voltage of the motor is also low, so the output of the amplifier 2 passes through the polarity reversing circuit 12 and becomes high, and the field current indicator 6
The amplifier 2 and the amplifier 7 operate independently of each other by the priority circuit 11, and control the armature current and the field current, respectively. However, when the rotational speed of the motor increases, the commanded armature current is supplied from the armature current command device 1, so the output voltage of the armature current thyristor conversion device 3 is also controlled to be high, and finally full conduction is achieved. At this point, the power factor of the armature current thyristor converter 3 is theoretically 0.955, which is the maximum. This speed is the speed _S1 point shown in FIG. Here, if the current command continues to be issued by the current command device 1, the armature voltage must be increased above the induced voltage of the motor, but the armature current thyristor conversion device 3 is already fully conductive. Since it is out of control, the deviation output of the amplifier 2 is about to suddenly increase, and the polarity reversal circuit 12 makes it smaller than the field current command value of the field current command device 6, and the priority circuit 1
1 to control the amplifier 7. When the input to the amplifier 7 becomes smaller, the input is applied to reduce the field current, so the induced voltage of the motor decreases, and the field is weakened until the commanded armature current is reached. These relationships are illustrated in Figure 3, where the output of the amplifier 2 decreases when the firing angle α of the armature current thyristor conversion device 3 reaches a value corresponding to 0°, and the input to the amplifier 7 decreases. , weak field control is performed. If this range is shown in FIG. 1, it is a range where the speed is _S1 or higher, the armature voltage is constant in a fully conductive state, and the field current is reduced as much as possible to reach the commanded armature voltage flow.

In this way, weak field control is automatically performed after the armature current thyristor converter 3 becomes fully conductive and reaches the maximum power factor, so that the high power factor of the vehicle can be achieved without the need for external means such as a phase advancing capacitor. Driving becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of characteristics of a motor for an AC electric vehicle, FIG. 2 is a block diagram showing an embodiment of the method of the present invention, and FIG. 3 is a firing angle α of the thyristor conversion device 3 with respect to the output of the amplifier 2. FIG. 1... Armature current command device, 2, 7... Amplifier, 3...
Thyristor conversion device for armature current, 4... Armature of motor, 5, 10... Current detector, 6... Field current command device, 8... Thyristor conversion device for field current, 9...
Field winding of electric motor, 11...Priority circuit, 12...Polarity reversal circuit.

Claims (1)

[Claims] 1. In the control of an AC electric vehicle that uses a thyristor conversion device to control a shunt-wound or compound-wound motor, a first thyristor conversion device controls the armature current of the motor, and a second thyristor conversion device controls the field current. a thyristor conversion device, the first thyristor conversion device is controlled by a first amplifier that amplifies the deviation between the armature current command value and the armature current, and the second thyristor conversion device is controlled by the first thyristor conversion device. The control circuit is controlled by a second amplifier that amplifies the deviation between the output of the amplifier and the field current command value through the signal priority circuit and the field current, and the first converter becomes fully conductive. , the output of the first amplifier is given priority and is input to the second amplifier, and the output of the first amplifier is used to reduce the field current. A high power factor operation method for an AC electric vehicle configured so that the power factor of the converter (1) is maximized.