JPH0150282B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to an electric vehicle driven by an induction motor controlled by a variable voltage variable frequency inverter. This invention relates to an electric vehicle control method when

[Technical background of the invention]

In recent years, with the development of power electronics, induction motors controlled by variable voltage variable frequency inverters (hereinafter referred to as VVVF inverters) have been used as the main motors of electric vehicles. Conventionally,
The rotation frequency FR of this type of induction motor was controlled as follows. In other words, as shown in Fig. 1, when four induction motors are controlled by one VVVF inverter, the electric vehicle is selected from among the rotational frequencies FR ₁ , FR ₂ , FR ₃ and FR ₄ of each motor when the electric car is in power running mode. The minimum value detection signal 1 is selected during regeneration, and the maximum value detection signal 2 is selected when regeneration is performed by alternately switching the switch 3 with the power running at "1" and the regeneration discrimination signal 4 at "0". .

In other words, when an electric car is running under power (hereinafter simply referred to as power running), selecting the one with the lowest rotation speed among the electric cars' motors as the FR means that the driving wheels of the electric car are not idling between the rails. If even one shaft remains sticky when this occurs, the rotational speed of the electric motor of this sticky shaft will be the minimum, so the minimum rotational speed will be used as the control input. In addition, when the electric car is under regenerative braking (hereinafter referred to as regeneration), if the electric car's driving wheels slide between the rails, the rotation speed of the sticky shaft will be higher than the other ones, so the maximum rotation You will have to choose a number. When the VVVF inverter is operated under control that keeps the ratio V/F of the output voltage V to the output frequency F constant, if the current of the induction motor is IP and the constant is K, then the torque T is T =
Since it is given by K(V/F)·IP, it can be seen that torque T is proportional to current IP. Now the second
As shown in the figure, at the point where the induction motor is operating at the current limit value IP=IP1, the driving wheels begin to spin, and at the same time, the current limit value 5 is lowered and the torque is reduced. After idling ends at point b and readhesion is detected, the current limit value 5 is changed to the value immediately before starting idling.
The IP is smoothly returned to IP1 and the torque value is restored.

The control flow for controlling such a current limit value is shown in FIG.

Now, when the inverter is started, the basic current limit value command 11 passes through the switch 13, a delay element 14 provided to prevent a sudden change in the current limit value, and then the switch 17 to become the current limit value command 18.

If idling occurs during operation in this state and the idling detection signal 12 becomes "1", the switch 13 and switch 17 switch to "1", and the current limit value command 18
is passed through the sampling hold circuit 15, and is subtracted by a current limit value reduction value of 16 at each sampling time in the subtracter 44. Also, delay element 1
4 also receives the value of current limit value command 18, so when slipping ends and readhesion is confirmed, switch 13
Then, the switch 17 returns to "0", and the decreased current limit value command 18 gradually returns to the basic current limit value command 11 because of the delay element 14.

[Problems with background technology]

As described above, during power running, the one with the lowest rotation speed among the plurality of induction motors is used as a control signal, and during regeneration, the one with the highest rotation speed is used as a control signal.
For this reason, if the driving wheels of an electric car cause all axes to slip or skid between them and the rail due to poor route conditions, the reference rotation frequency signal will not be obtained and the load will become light. , the system may become unstable. Therefore, the current limit value command 18, that is, the method of lowering the torque by lowering the slip frequency, cannot be used when all the shafts are idling. In addition, for example, even if only one axis stops idling, the current limit value returns immediately, so there is a strong possibility that the idling will occur again if route conditions become locally bad. .

The above-mentioned case is when the vehicle is idling, but the same problem occurs when the vehicle is skidding.

[Purpose of the invention]

The purpose of the present invention is to reduce the torque of all wheels while maintaining the stability of the system, making it easier to re-stick, making it difficult to re-slip or skid even if the route conditions are locally bad.
Another object of the present invention is to provide an electric vehicle control method that makes it difficult for the electric vehicle to repeatedly spin or skid even when the overall route conditions are poor.

[Summary of the invention]

In the present invention, the driving wheels of an electric vehicle driven by an induction motor using a variable voltage variable frequency inverter are mounted on a rail surface.
In the case of slipping during power running or skidding during regeneration, the current limit value of the induction motor begins to be gradually lowered at the same time as the slipping or skidding is detected, and if all axes continue to slip or skid, these From the time when is detected, the current limit value is kept constant, and at the time when this current limit value is kept constant, the ratio of the output voltage V and output frequency F of the inverter is V/F.
When readhesion is detected in even one axis, the V/F value is gradually returned to the value just before starting all axes slipping or all axes sliding. Continue to lower the current limit value that was kept constant during the period of all axes idling or all axes sliding, keep the above current limit value constant for a certain period from the time it is detected that the idling or sliding has completely ended, and then, This is an electric vehicle control method in which control is performed to gradually return to a value obtained by multiplying the value immediately before the start of slipping or skidding by a value of 1 or less, with one cycle being performed from when the inverter is started until it is stopped.

[Embodiments of the invention]

The present invention will be described below with reference to the drawings, but first, current limit value control will be described. Fourth
In the figure, when the start command 20 becomes "1" and the inverter starts, the start time current limit value magnification 22 that was set to the "0" side of the switch 21 changes to the "0" side of the switch 21.
is switched to the "1" side, and the magnification of 1 is maintained through the switch 23 and the sampling hold circuit 24. The value of the basic current limit value command 11 is determined by the multiplier 2
5, through a switch 13, a delay element 14, and further through a switch 17 to become a current limit value command 18.

If idling occurs during driving in this state and the idling detection signal 12 becomes "1", the switch 13 and switch 17 are switched to "1", and when the all-axes idling detection signal 26 becomes "0", The output of the logic NOT circuit 27 becomes "1", the output of the AND circuit 28 becomes "1", and the switch 29 is switched to "1", so the value of the current limit value command 18 is passed through the sampling and hold circuit 15. , the current limit value reduction value of 16 is subtracted every sampling time. At the same time that the slip detection signal 12 becomes "1", the single shot circuit 30 outputs a waveform of one pulse, and the switch 23 switches to "1" for one sample time, and then returns to "0". . As a result, the multiplier 31 multiplies the multiplier value of 1, which has been held in the closed loop of switch 21 - switch 23 - sampling hold circuit 24 - switch 21 since the inverter was started, by the steady current limit value reduction rate 32, and the above value is newly added. It will be held by a closed loop.

When the idling ends and re-adhesion is confirmed,
The all-axis slip detection signal 26 and the slip detection signal 12 both become "0", and the logic NOT circuit 27 becomes "1", but the output of the AND circuit 28 becomes "0", and the switch 29 shifts to "0". Switch. By switching the switch 29 to "0", the zero command 33 is given to the subtracter 44 via the switch 29, and the current limit value command 18 becomes constant.The slip detection signal 12 becomes "0".
Then, the output of the off-delay circuit 34 returns to "0" after the delay time 35, and the switches 13 and 17 return to the "0" side. 25, the current limit value will gradually return to the value obtained by multiplying the value of the basic current limit value command 11 by the multiplication factor after idling.

In this state, if the motor idles again, the steady current limit value is further set to a value multiplied by the steady current limit value reduction rate of 32, and the steady current limit value decreases each time the motor idles.

Next, a V/F value control method will be explained with reference to FIG.

In other words, under normal conditions, the inverter output frequency is 36
The voltage command value calculated by the inverter output voltage calculation circuit 38 from ) Rapid voltage changes are suppressed by the change rate limiter 40,
Inverter output voltage command 42 via switch 41
becomes.

When idle shafts occur and all axes idle, the all axes idle detection signal 26 becomes "1" and the switch 3
9 and switch 41 are switched to "1". As a result, the inverter output voltage command 42 is subtracted by the value obtained by multiplying the voltage value reduction coefficient 45 by the inverter output frequency 36 by the multiplier 46 every sampling time through the sampling hold circuit 43. While the all-axis idle detection signal 26 is “1”, the AND circuit 2 in FIG.
The output of 8 becomes "0", and the switch 29 becomes "0"
Therefore, the current limit value command 18 is kept constant.

If even one axis re-sticks from a state where all axes are idling, it will be the same as normal idling and the output of the AND circuit 28 will be "1", so the switches 13 and 17 will be "1".
, the current limit value command 18 decreases again, but the inverter output voltage command 42 returns to "0" as the all-axis idling detection signal 26 returns to "0", and the switch 3
9 and the switch 41 return to the "0" side, the decreased inverter output voltage command 42 gradually returns to the output value of the inverter output voltage calculation circuit 38 while being limited by the change rate limiter 40.

This series of operations is carried out in a period from when the inverter start command 27 becomes "1" to start the inverter to when it becomes "0" and stops, when all the shafts are idling.

The above explanation is for the case where all axes of the electric vehicle are idling during power running, but the same can be said for the case where all axes are sliding during regenerative braking.

Figure 6 shows the current limit value when all shafts are idling as mentioned above.
It shows the change in IP5 and the change in V/F value 6.

After the inverter is started, when one shaft begins to idle at time t ₁ in Figure 7, the torque of the induction motor decreases, so the current limit value IP5 begins to gradually decrease. The number of wheels increases, and other wheels start spinning one after another, potentially causing all axles to spin.

When all axes start idling at time t ₂ , the current limit value IP
5 is kept constant, and at the same time, the V/F value 6, which has been kept constant until now, starts to gradually decrease at a certain rate.

Since all induction motors are in an unstable state while all axes are idling (between times t _{2 and} t ₃ ), the torque is How to reduce the current limiting value
By controlling either IP5 or V/F value 6, stability can be maintained as much as possible.

Fig. 7 shows a simple equivalent circuit diagram when an induction motor is operated by a VVVF inverter, in which 50 is a filter capacitor, 51 is a VVF converter, 52,
53 and 54 are the induction motor field component, induction motor equivalent inductance, and induction motor secondary side resistance, respectively.

In such a configuration, the torque is determined by the product of the current flowing through the induction motor field component 52 and the current flowing through the induction motor secondary side resistance component 54.
In order to reduce the torque, it is necessary to lower one or both of the above two factors.

During normal idling, by keeping the V/F value 6 constant, the induction motor field component 52 is kept constant, and the slip S of the value R/S of the induction motor secondary side resistance 54 is reduced to reduce the R/S. By increasing the S value, the flowing current is made smaller and the torque is reduced, but in the case of all shafts idling, control is added to lower the V/F value 6, so the current flowing to the induction motor field component 52 is also reduced. becomes smaller and the torque decreases. In this case, if the actual slip S of the idling wheels approaches 0, there is a risk that the system will become unstable, so it is necessary to select an appropriate value for the rate of change limit of the inverter frequency F in consideration of the current limit value reduction rate, etc. be.

The V/F value 6 decreases and the torque decreases,
If readhesion is confirmed in even one axis, the V/F value 6 will gradually return to its original value, but the current limit value IP5 will continue to decrease while even one axis is idle. Then, when readhesion of all the chains is confirmed, the current limit value IP5 gradually returns to the value just before the start of idling.

Although the above explanation is about all-axis slippage, the same can be said about all-axis sliding.

According to the embodiment of the present invention described above, a state in which an electric vehicle driven by an induction motor using a VVVF inverter is idling during power running or skidding during regeneration is detected;
If all axes start idling, the current limit value that was attenuated during idling is kept at a constant value and the V/F value is lowered, so the torque of all S wheels is reduced while maintaining system stability. It can make re-adhesion easier. In addition, if even one axis re-sticks, the control will shift to lowering only the current limit value, just like during normal idling or skidding, but when the end of idling is detected, the current limit value at that time will be maintained for a certain period of time. , even if the route is locally bad, it can be made difficult to re-slip or skid again.

Furthermore, after a certain period of time has elapsed since re-adhesion was detected,
By gradually returning the current limit value to the value below the value before the start of slipping or skidding, the steady torque is lowered, so even if the route conditions are generally poor, slipping or skidding can be avoided. can be made difficult to repeat.

〔Effect of the invention〕

According to the present invention, it is possible to reduce the torque of all wheels while maintaining the stability of the system, making it easier to re-stick, making it difficult to re-slip or skid even if the route conditions are locally bad.
Furthermore, it is possible to provide an electric vehicle control method that makes it difficult for the electric vehicle to repeatedly spin or skid even if the overall route conditions are poor, and thus allows the electric vehicle to run stably.

[Brief explanation of drawings]

FIG. 1 shows a control circuit for detecting the operating state of an induction motor for driving an electric vehicle, which is a control target of the present invention, and FIGS. 2 and 3 are time charts for explaining an example of a conventional electric vehicle control method. 4 and 5 are a current limit value command control circuit diagram and a V/F control circuit diagram for explaining an embodiment of the electric vehicle control method according to the present invention. , FIG. 6 is a diagram showing the relationship between time and current limit value or time and V/F value in the same example,
FIG. 7 is a simplified equivalent circuit diagram of a VVVF inverter and an induction motor for explaining the method of the present invention. 1...Minimum value detection signal, 2...Maximum value detection signal, 3
...Switch, 4...Power running, regeneration discrimination signal, 5...Current limit value IP, 6...V/F value, 11...Basic current limit value command,
12...Idle rotation detection, 13, 17, 21, 23, 3
9,41...Switch, 14...Delay element, 15,2
4, 43...Sampling hold circuit, 16...Current limit value reduction value, 18...Current limit value command, 20...Start command, 22...Current limit value magnification at startup time, 25, 31, 46
... Multiplier, 26 ... All-axis idle detection signal, 27 ... Logical NOT circuit, 28 ... AND circuit, 30 ... Single shot circuit, 32 ... Steady current limit value multiplier, 33 ... Zero command, 34 ... Off-delay, 35 ... delay time, 3
6... Inverter output frequency, 37... Overhead line voltage, 3
8... Inverter output voltage calculation circuit, 40... Rate of change limiter, 42... Inverter output voltage command, 44
...Subtractor, 45...Voltage value reduction coefficient, 50...Filter capacitor, 51...VVVF converter section, 52...
Induction motor field component, 53...Induction motor equivalent inductance, 54...Induction motor secondary side resistance.

Claims (1)

[Claims] 1. In an electric vehicle in which multiple induction motors are driven by one variable voltage variable frequency inverter, and the driving wheels can run on rails using this driving force, the driving wheels idle or regenerate while powering on the rail surface. The current limit value of the induction motor starts to be gradually lowered as soon as it detects that the motor has skidded. If all axes are idling or all axes are skidding, the current limit value must be kept constant from the moment this is detected. keep it to
At the point when this current limit value is kept constant, the ratio V/F of the output voltage V and output frequency F of the inverter is decreased to reduce the torque, and if re-adhesion is detected even on one axis, from there the above V/F The value of is gradually returned to the value immediately before starting all axes idling or all axes sliding, and the current limit value, which had been kept constant during the above all axes idling or all axes sliding period, continues to be lowered, and the The inverter controls the current limit value to be kept constant for a certain period of time from the time when it is detected that skiing has completely ended, and then gradually return to the value obtained by multiplying the value immediately before slipping or skiing by a value of 1 or less. An electric vehicle control method characterized in that one cycle is performed from when the electric vehicle starts until it stops.