JPH0161001B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a control device for an induction motor type electric vehicle, and particularly to a control device for an induction motor type electric vehicle that facilitates starting of the electric vehicle on an uphill slope. Regarding equipment.

[Conventional technology]

Figure 1 shows a typical configuration example of an electric vehicle control device driven by an induction motor, where 1 is a pantograph, 2 is a variable voltage variable frequency power converter (e.g. inverter), and 3 is an induction motor. , 41
is a current detector. 42 is a current control device that compares the motor current I _M and its command value I _P and controls the output voltage of the inverter 2 so that I _M = I _P ;
1 is a pulse generator for detecting the rotation speed of the induction motor; 52 is a pulse number/voltage converter that generates a voltage according to the pulse frequency of the pulse generator; 5
3 is the slip frequency command _SP and the motor rotation frequency
_R and the output frequency command of inverter 2.
This is an adder that outputs _E.

If the control device is configured as shown in FIG. 1 and the slip frequency command _SP and current command I _P are set to constant values, the induction motor 3 is controlled with constant slip, constant current, and accelerated with constant torque.

At this time, the relationship among the rotation speed N of the induction motor 3, the rotation frequency _R , and the inverter output frequency _E is as shown in the first quadrant of FIG. 2.
That is, the slip frequency _S = _E - _R is controlled to be constant at the command value _SP . Note that even if the constant current control system is omitted and a V/constant control system that commands the output voltage V proportional to the frequency _E is added, the control results will be substantially the same. Generally, the control system is switched to this V/constant control system except during startup.

By the way, when starting an electric vehicle, the brakes (usually air brakes are used) that are activated when the vehicle is stopped are loosened, and then the power running notch of the master controller is turned on. Now, assuming that an electric car stops on an uphill section and starts again, the electric car will move backwards due to gravity between the time the brake is released and the time when the power running notch is engaged and forward tension is established. It is possible to do so.

When the electric vehicle moves backward in this way, the traction force decreases, and in some cases, there is a risk that the electric vehicle will continue to move backward without being able to move forward. Next, the reason will be explained.

When the electric car moves backward, the rotation direction of the induction motor 3 is reversed, but the output _R of the pulse generator 52 and the inverter output frequency _E both increase as shown in the second quadrant of FIG. In the second quadrant, the phase rotation of the excitation by the inverter and the rotation direction of the rotor of the induction motor 3 are opposite, and increase with the backward speed of the electric vehicle. In this way, the pulse generator 5
2 does not have the ability to detect the direction of rotation, so even though the electric car is moving backwards, the inverter frequency is the sum of the backward speed and the slip frequency _S.
The actual slip frequency of the motor reaches a high slip frequency region exceeding the stall torque, and the torque continues to decrease.

For this reason, firstly, as disclosed in JP-A-56-74001, for example, by adding a rotation direction detection function, it is possible to obtain a continuous ideal frequency from positive through zero to negative. It is known to provide control.

Second, for example, Mitsubishi Electric Technical Report Vol.56/No.
Reversal (backward) as disclosed in 8.1982 page 37
It is proposed to fix the inverter frequency to a minimum value by means of a sensing function.

[Problem that the invention seeks to solve]

The first method mentioned above is obviously an ideal type, but the inverter requires continuous control including frequency "zero" (DC), and it is an asynchronous mode that is different from the modulation mode synchronized with the normal command frequency. Requires mode modulator, electric car is unidirectional (forward or reverse)
Hardware, such as phase sequential switching of three phases, is required.
Complications cannot be ignored in terms of software.

Therefore, although the second method is simple, it still lacks reliability depending on the gradient.

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned conventional drawbacks and to ensure reliable starting of an electric vehicle on an uphill slope.

[Means for solving problems]

The main feature of the present invention is to suppress an increase in the output frequency of the power converter and suppress a decrease in the output voltage of the power converter when the electric vehicle backs up.

[Effect]

When a control system for suppressing an increase in the output frequency of the power converter is added to the control system shown in FIG. 1 at startup, similar to the known technology described above, the inverter output frequency changes to f ₁ → in FIG. 3. It will no longer increase as f ₂ → f ₃ . Therefore, the regression due to this frequency increase (f _r <
The torque decrease at 0) is eliminated. However, when the actual slip frequency increases due to retraction, the current increases to try to maintain the generated torque, but the current is suppressed to a constant value by the constant current control device 42 of FIG. Therefore, the torque characteristics are
The torque changes as l ₁ → l ₂ → l ₃ , and the generated torque also changes as P ₁ → P ₂ → P ₃
It tries to decrease as follows.

Focusing on this point, the present invention not only suppresses an increase in the output frequency but also suppresses a decrease in the output voltage due to the current control system. As a result, the torque characteristics can maintain the characteristic l ₁ even when the electric vehicle is moving backwards, and by increasing the output voltage according to the backward speed, the generated torque can be further increased, resulting in more reliable starting. becomes possible.

〔Example〕

FIG. 4 shows an embodiment of the present invention. The same parts as in FIG. 1 are represented by the same symbols. The difference from FIG. 1 is that a reversing detector 61 for the electric car is provided, and its output is input into a minimum value selector 62 and a maximum value selector 63, and when the electric car is reversing, the inverter (power converter) output frequency is is fixed at the lowest value _EO , and the inverter output voltage is maintained at a predetermined value _VEO .

Figure 5 shows the characteristics of the frequency command _E. In the region of positive rotation speed, normal control with a constant slip frequency, and in the region of negative rotation speed, the frequency is the lowest value.
Fixed to _EO . In this figure, the region where _R <0 means that the induction motor 3 is rotating in the opposite direction.

FIG. 6 is an explanatory diagram of the operation of the above embodiment. 6th
The torque characteristics in the figure indicate the minimum value of the inverter output frequency.
This is when the electric vehicle is fixed at _EO and the inverter output voltage is maintained at a predetermined value. When the electric vehicle moves backward, the torque increases as the operating point P _{1 shifts from P 1} to P ₂ →P ₃ when the electric vehicle does not move backward.

According to this embodiment, even when the electric vehicle is moving backward, there is no shortage of starting torque, so it can start smoothly even on an uphill slope.

In the embodiment, the part of the pulse/voltage converter 52 and the adder that adds the output _R and the slip frequency pattern _SP to generate the inverter output frequency pattern is shown to be of an analog calculation type, but this part is a microprocessor. Digital calculation means such as a processor may also be used.

FIG. 7 shows an example of the configuration of a reversing detector, in which 511 is a disk with unevenness around the periphery attached to the shaft end of the induction motor 3, and 611 and 612 are used to detect unevenness on the circumference of the disk. The sensing element 613 is a phase discriminator that discriminates the phases of the output voltages A and B of the sensing elements 611 and 612.

The sensing elements 611 and 612 are placed in advance with their phases shifted by 90 degrees with respect to the irregularities of the disc 511. In this way, the sensing elements 611, 612
For example, the waveforms of the output voltages P ₁ and P ₂ of the disk will have a phase relationship as shown in Figure 8A when the disk is rotating clockwise, and as shown in Figure 8B when it is rotating counterclockwise. Become. That is, P ₁ and P ₂ depending on the direction of rotation.
The phase relationship is reversed. The rotation direction of the induction motor 3 can be controlled by using the phase discriminator 613 to discriminate the phase lead/lag relationship between P ₁ and P ₂ .

〔Effect of the invention〕

As explained above, according to the present invention, when an electric vehicle develops on an uphill slope, the torque of the induction motor does not decrease even if it retreats once, making it possible to start smoothly. .

[Brief explanation of drawings]

Fig. 1 is an example of the conventional example, Fig. 2 is an explanatory diagram of the operation of the conventional example, Fig. 3 is an explanatory diagram of the principle of the present invention, Fig. 4 is an embodiment of the present invention, Figs. 5 and 6. 7 is a partial detailed view of an embodiment of the present invention, and FIG. 8 is an explanatory view of the operation. 2... Power converter (inverter), 3... Induction motor, 42... Current control device, 52... Pulse/voltage converter, 53... Adder/subtractor, 61... Backward detector, 62... Minimum value Selector, 63...Maximum value selector.

Claims (1)

[Scope of Claims] 1. An induction motor for driving an electric vehicle, a variable voltage variable frequency power converter for feeding power to this motor, and means for giving an output frequency command to the converter in relation to the speed of the electric vehicle. , means for giving an output voltage command to the converter in relation to the frequency or motor current, the means for suppressing an increase in the output frequency of the converter when the electric vehicle backs up, and the output of the converter. A control device for an induction motor type electric vehicle, comprising means for suppressing voltage drop. 2. The control device for an induction motor type electric vehicle according to claim 1, wherein the frequency increase suppressing means is means for fixing the frequency increase to a minimum output frequency preset in the converter.