JPH0446502A - Controller for electric vehicle - Google Patents

Abstract

PURPOSE:To prevent idling or slip of wheel by determining electrical angular speeds, at the time of powering and braking, based on the minimum and maximum speeds of the induction motor in an electric vehicle to be driven through a plurality of inverters and then adding thus determined electrical angular speeds to a slip frequency command. CONSTITUTION:A plurality(four in the drawing) of inverters 6i generate VVVF AC power for driving an induction motor 7i. Speed of each motor 7i is then detected 9i and converted 10 into an electrical angular speed which is then fed to a selecting means 11. A current control means 2i determines a slip frequency based on a command provided from a current pattern generating means 1i and an output from a current detecting means 8i. Electrical angular speed selected by the selecting means 11 is added 3i to the slip frequency determined by the current control means 2i, and a PWM pulse is generated 5i through a V/F constant control means 4i in order to control the inverters 6i. Angular speed of a minimum speed motor 7i is selected 11 at the time of powering whereas an angular speed of a maximum speed motor 7i is selected at the time of braking. Consequently, idling or slip of wheel is prevented thus protecting the wheel or the rail against damage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a drive control device for an electric vehicle driven by an electric motor.

(Conventional technology) Electric cars use electric motors to apply rotational force (torque) to the wheels.
The axle is propelled by using rotational force as a propulsion force due to the viscous force (frictional force) between the axle and the rail. The adhesive force FAD of one axle is FAD""μW, where μ is the adhesive coefficient and W is the weight (weight) applied to the axle. When the rotational force FTH exceeds the adhesive force, the wheels are accelerated by the excess rotational cam FTH (=ΔF THF AD) to a speed higher than the vehicle body speed and idle on the rails, resulting in a significant reduction in propulsion force transmission. This phenomenon occurs during driving and is called "idling." During braking, if the braking force FBR exceeds the adhesion force, the axle is decelerated below the vehicle body speed by the extra braking cam FOR (=FnRFAD), and the axle slides over the rail, resulting in a significant reduction in braking force transmission. This is called "gliding."

Hereinafter, in the present invention, an explanation will be given regarding slipping, but since the exact same thing holds true for sliding, the explanation may be omitted. Note that the axle that is connected to the electric motor is called a driving wheel, and the axle that is not connected is called a slave axle.

As described above, slipping occurs when the rotational force exceeds the adhesive force, but the same thing occurs when the adhesive force is lower than the rotational force.

When slipping occurs, the first thing that happens is that the driving force is not transmitted smoothly, but this can lead to peeling of the treads of the other driven wheels, burnout of the bearings,
Secondary problems such as rail fatigue and wear also occur.

Here, we will show an example of conventional control and point out its problems. FIG. 2 is a control block diagram showing a general configuration of a motor drive device in an electric vehicle that drives an induction motor using a plurality of PWM inverters. As shown in the figure, each constitutes a current control loop, gives a current command, controls the torque of each electric motor, and controls the driving force of the electric vehicle. In the figure, la, lb
, lc, and ld are current command pattern generation means that generate a current pattern (actual current command) based on the current command;
2a, 2b.

2c and 2d are current control means that output a slip frequency command based on appropriate control logic using the current pattern and the detected actual motor current; 3a, 3b, 3c, and 3d;
4a and 4b are adding means for adding the slip frequency command to the motor rotation frequency to generate the inverter frequency command;

4c and 4d are V/F- based on the inverter frequency command.
V/F constant control means for constant control, 5a, 5b, 5
c.

5d is the PW based on the voltage command which is the V/F constant control output.
PWM pulse generating means for generating M pulses, 6a, 6
b, 6c, 6d are PWM control voltage type inverters, 7
a, 7b, 7c, 7d are induction motors, 8a, 8
Reference numerals b, 8c, and 8d are current detection means, and the detected currents are fed back to current control means 2a, 2b, 2c, and 2d, respectively. 9a.

9b, 9c, and 9d are speed detection means, and the detected speeds are converted to conversion means 10a, lob, 10c, and 10d, respectively.
Adding means 3a converts into electrical angular velocity and creates an inverter frequency command.

The configuration is such that it is sent to 3b, 3c, and 3d. The driving wheels connected to the induction motor are not shown.

(Issues to be Solved by the Invention jv) When controlling the drive of an electric vehicle using this motor control system, there is no problem as long as none of the driving wheels slips or slides. Here, we will explain the case where the driving wheels connected to the induction motor 7a are idling, but #! Exactly the same thing holds true even when the driving wheels connected to the I-conduction motors 7b to 7c to 7d are idling, so the explanation will be omitted. Strictly speaking, it is the driving wheels connected to the induction motor that cause the wheel to spin, but in order to simplify the expression, it is sometimes stated that the induction motor causes the wheel to spin.

If slipping occurs, it will manifest as a sudden increase in induction motor speed. In the conventional example, the frequency command for each inverter is given by adding a feedback signal obtained by converting each induction motor speed into an electrical angular velocity to the full frequency command, so a sudden increase in the speed of the induction motor 7a is directly applied to the inverter 6a. This leads to a sudden increase in the output frequency. As the inverter frequency increases, the speed of the induction motor driven by the inverter further increases. This is a typical positive feedback phenomenon, and the drive power control device 11a becomes unstable, the output frequency of the inverter 6a diverges, and the induction motor 7
A goes wild. When such a large slump occurs,
It becomes extremely difficult to perform so-called readhesion control to return this state to a healthy adhesive state, and it is often necessary to turn off the power due to notch-off or the like.

The present invention eliminates the above-mentioned problems in the prior art,
It is an object of the present invention to provide a drive control device for an electric vehicle that is less likely to cause sudden fluctuations in the inverter frequency supplied to an induction motor connected to driving wheels that are idling or sliding.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the objects stated in the following, the present invention is a drive control system for an electric vehicle that controls the drive power source of the electric vehicle with the following configuration.

In a control device for an electric vehicle that controls at least two or more variable voltage/variable frequency inverters that drive induction motors, there is a means for detecting the speed of each induction motor, and a means for detecting the speed of each of the speed signals detected by the speed detecting means during power running. means for selecting a minimum value and a maximum value during braking, means for converting the output of the selection means into an electrical angular velocity, and calculating the inverter frequency by adding the electrical angular velocity output from the conversion means and the slip frequency command. The invention is characterized in that it includes means for calculating the inverter, and provides the output of the inverter calculation means as a frequency command for each of the inverters.

(Function) With the electric vehicle control device configured in this way, even if slipping or skidding occurs, it is possible to prevent sudden fluctuations in the frequency command of the inverter that supplies power to the electric motor connected to the driving wheels. , it is possible to eliminate the drawbacks of the prior art pointed out in the section (Problems to be Solved by the Invention).

(Example) The present invention will be described in detail below with reference to FIG. In this figure, the same components as in FIG. 2 are given the same symbols and their explanations will be omitted.

In Fig. 1, 11 is a selection means which selects the minimum value among the electrical angular velocities of the four induction motors during power travel and the maximum value among the electrical angular velocities of the four induction motors during braking. Adding means 3a, 3b, 3 as a feedback signal
I am trying to input it to c and 3d.

Here, let us consider the case where the vehicle is running normally, that is, when the vehicle is running without any of the driving wheels idling or skidding. Induction motor 7a, 7
Let the rotational speeds of the axles connected to b, 7c, and 7d be Vat Vb, Vc, and Vd, respectively. In this case, the variation in each rotational speed is due to individual differences in axle diameter and wear when manufactured with the same specifications. It's quite small. Therefore, the following relationship holds true.

Va 4 Vb "5 Vc 4 Vd Therefore, if the output of the selection means 11 of the present invention is V', it becomes V' 4 Va Misaki Vb press Vc press Vd, and the feedback signal input to the adding means 3a, 3b, 3c, 3d is approximately the same amount in both the present invention and the conventional example. Therefore, during normal running, the control of the present invention provides almost the same control as the conventional control.

Next, consider a case where the driving wheels connected to the induction motor 7a idle. In this case, the rotational speed Va of the induction motor increases rapidly. In the conventional example shown in FIG. 2, the speed of the induction motor 7a converted into an electrical angular velocity is directly fed back to the adding means 3a, so the frequency command of the inverter 6a increases rapidly and the number of idles increases. On the other hand, according to the control of the present invention, in this case, the feedback signal selects the minimum value among the electrical angular velocities of the four induction motors, so it becomes V' ``5 Vb ``5 Vc ''5 Vd, and the feedback signal due to idling is There is almost no change in the inverter frequency, and a sudden increase in the inverter frequency can be prevented.

Also, consider a case where the driving wheels connected to the induction motor 7a slip. In this case, the rotational speed Va of the induction motor suddenly decreases. In the conventional example shown in FIG. 2, the frequency command of the inverter 6a suddenly decreases and the slippage increases due to the above-mentioned reasons. According to the control of the present invention, in this case, the feedback signal selects the maximum value among the electrical angular velocities of the four induction motors, so V''= Vb'= Vc L:Vd, and the change in the feedback signal due to idling also occurs. There is almost no change in the inverter frequency, and a sudden decrease in the inverter frequency can be prevented.In this way, if a sudden change in the inverter frequency during slipping or skidding can be avoided, readhesion control based on some control theory, which is not included in the present invention, can be performed. This provides sufficient time for the adhesive to take effect, and an improvement in re-adhesion properties can be expected.

It is also expected that natural readhesion will occur due to changes in track conditions.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a control device for an electric vehicle in which the inverter frequency does not suddenly change when the vehicle is idling or skidding.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention, and FIG. 2 is an overall configuration diagram showing a conventional example. la, lb, lc, ld... current pattern generating means,
2a, 2b, 2c, 2d"' current control means, 3a, 3b
, 3c, 3d - addition means, 4a, 4b, 4c, 4d - V/F constant control means, 5
a, 5b, 5c, 5d=-PWM pulse generating means,
6a, 6b, 6e, 6d...P WM control voltage type inverter 7a, 7b, 7c, 7d-induction motor, 8a, 8
b, 8c, 8d - current detection means, 9a, 9b, 9c, 9
d-speed detection means, 10a, 10b, 10c, 10d-
means of conversion. 11...Selection means. Agent Patent Attorney Noriyuki Chika

Claims (1)

[Scope of Claims] A control device for an electric vehicle that controls at least two or more variable voltage/variable frequency inverters that drive induction motors, comprising means for detecting the speed of each induction motor, and each speed detected by the speed detection means. Means for selecting the minimum value of the speed signal during power running and the maximum value during braking, means for converting the output of the selection means into an electrical angular velocity, and adding the electrical angular velocity output from the converting means and the slip frequency command. 1. A control device for an electric vehicle, comprising means for calculating an inverter frequency by calculating an inverter frequency, and providing an output of the inverter calculating means as a frequency command for each of the inverters.