JPH0515126B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is directed to the regenerative braking of an electric vehicle driven by a plurality of induction motors controlled by a single variable voltage variable frequency inverter. This invention relates to a regenerative braking control device for an electric vehicle when skidding occurs.

[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. That is, as shown in Fig. 1, when controlling four induction motors with one VVVF inverter, the rotational frequencies FR1, FR2, FR3, and FR4 of each motor are determined by the minimum value detection circuit 1 and the maximum value detection circuit 2. Input each of these rotation frequencies FR1 to FR4 to the minimum value,
Detects the maximum value, and when the electric vehicle is running, the discrimination circuit 4
The switch 3 is switched to the "1" side by the power running discrimination signal "1" output from the minimum value detection circuit 1, and the regeneration discrimination signal "0" is output from the discrimination circuit 4 during regeneration. ” to switch the switch 3 to the “0” side and select the maximum value detection signal.

In other words, when an electric car is running under power (hereinafter simply referred to as power running), the one with the lowest rotation speed among the electric motors is selected as the FR, which means that the driving wheels of the electric car are idling with the rail. If even one wheel remains sticky at this time, the rotational speed of the electric motor for this sticky shaft will be minimum, so the minimum rotational speed is input for control. 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 This means controlling and inputting numbers. By the way, the VVVF inverter has a ratio of output voltage V to output frequency F, V/F.
When regenerative braking is performed under control to keep constant, if the current of the induction motor is IB and the constant is K, the braking torque T is given by T = K (V / F) · IB, so the braking It can be seen that torque T is proportional to current IB. In the graph showing the change in motor current with respect to time shown in Figure 2, when the current value of the induction motor is 5 and the driving wheels begin to slide at point a in the figure during regenerative braking with IB = IB1, the current limit value changes at the same time. 5 and reduce the braking torque. Then, after sliding ends at point P in the figure and readhesion is detected, the current limit value 5 is smoothly returned to the value just before starting sliding, IB=IB1, and the torque value is restored.

The control flow for controlling the current limit value of the induction motor in this way is shown in FIG. 3. Now, when the inverter is started during coasting operation, the basic current limit value command 11 passes through the switch 13 and enters the delay element 14 provided to prevent sudden changes in the current limit value. The value command becomes 18.

If a skid occurs during regenerative braking in this state, the skid detection signal 12 will become "1", causing the switch 13 and switch 17 to change from the "0" side to "1".
Switch to the side. As a result, the current limit value command 18 is passed through the sampling hold circuit 15 to the subtracter 1.
0, and in this subtractor 10, the current limit value command 1
Since the predetermined current limit value reduction value 16 is subtracted from 8 every sampling time,
Torque T gradually decreases. Further, at this time, the value of the current limit value command 18 subtracted by the subtracter 10 is also entered into the delay element 14. Eventually, when the sliding ends and readhesion is confirmed, the switch 13 and the switch 17 return from the "1" side to the "0" side.
The reduced current limit value command 18 gradually returns to the basic current limit command 11 because of the delay element 14.

[Problems with background technology]

As described above, during regeneration, the one with the highest rotation speed among the plurality of induction motors is used as a control signal. Therefore, if the driving wheels of an electric car skid on all axes between them and the rails due to poor route conditions, the reference rotation frequency signal will not be obtained and the load will become light, causing system failure. There is a risk that it will become stable. Therefore, the current limit value command 18, that is, the method of lowering the braking torque by lowering the slip frequency, cannot be used when all axes are sliding.

[Purpose of the invention]

The purpose of the present invention is to reduce the braking torque of all wheels while maintaining the stability of the control system when skidding on all axes, making it easier for sliding wheels to re-adhere, and to prevent re-slipping even if the route conditions are locally bad. Moreover, it is an object of the present invention to provide a regenerative braking control device for an electric vehicle that can prevent repeated skidding and allow the electric vehicle to run stably even when the route conditions are bad overall.

[Summary of the invention]

In order to achieve the above object, the present invention is configured as follows. That is, in the first invention, the skid detection means X and the current limit value control means Y are
This is a regenerative braking control device for an electric vehicle having a V/F control means Z, in which the electric vehicle is powered or regeneratively braked by driving a plurality of induction motors M by one variable voltage variable frequency inverter 51. The skid detection means X detects skidding on all axes of the driving wheels or at least on one axis, and the current limit value control means Y detects basic current limit value command 11 and skid during regenerative braking. Input the output of detection means X,
If slippage of at least one axis is detected by the slippage detection means If the current limit value is gradually decreased and the sliding of the driving wheels is ended by the skid detection means X and the skid detection signal is not output and a state of re-adhesion occurs, the current limit value command 18 immediately before this is kept constant. output, induction motor M
During regenerative braking, the V/F control means Z inputs the skid detection signal from the skid detection means X, the overhead line voltage signal, and the inverter output frequency, and at least When shaft skidding is detected, a constant inverter output voltage command 42 is output, the ratio V/F between the output voltage V and the output frequency F of the inverter 51 is controlled to be constant, and the skidding detection means X detects that all shafts are skidding. is detected, the inverter output voltage command 42 is decreased by a predetermined value every sampling time, and the output voltage V and output frequency F of the inverter 51 are
This is a regenerative braking control device for electric vehicles that variably controls the V/F ratio.

The second invention is a regenerative braking control device for an electric vehicle having a skid detection means X, a current limit value control means Y, and a V/F control means Z, wherein the electric vehicle has one variable voltage variable Power running or regenerative braking is performed by driving a plurality of induction motors M by a frequency inverter 51, and the skid detection means X detects skidding on all axes of the driving wheels or at least on one shaft, and limits The flow value control means Y inputs the basic flow limit value command 11 and the output of the skid detection means X during regenerative braking,
If at least one axis slip is detected by the slip detection subject Gradually decreases the current limit value of , and when the sliding of the driving wheels ends and the skid detection signal is no longer output, the current limit value command 18 just before is output to control the current flowing to the induction motor M. , when all the axes are detected to be skidding by the skid detection means In this case, the current limit value command 18 is gradually decreased, and the current limit value command is restored after a predetermined period of time after the skidding detection means X no longer detects skidding on one axis, so that the current limit value at that time is the value immediately before skidding. The V/F control means Z receives the skid detection signal from the skid detection means X, the overhead line voltage signal, and the inverter output frequency during regenerative braking. However, when at least one axis is skidded by the skid detection means X, the ratio V/F between the output voltage V and the output frequency F of the inverter 51 is kept constant, and the skid detection means If detected, the inverter output voltage command 42 is decreased by a predetermined value every sampling time, and the inverter output voltage command 42 is decreased by a predetermined value every sampling time.
The braking torque is controlled by decreasing the ratio V/F between the output voltage V and the output frequency F of If the voltage command value of the inverter 51 and the inverter output voltage command value 42 are compared, the V/F value is determined to be V/F.
This is a regenerative braking control device for electric vehicles that waits until a voltage command value that matches a pattern is reached.

[Embodiments of the invention]

The present invention will be explained below with reference to the drawings, but first the current limit value control means Y will be explained. In Fig. 4, the regeneration start command 20 is “1”
When the inverter starts up, switch 21
is switched from the "0" side to the "1" side, and the value of the basic current limit value command 11 passes through the switches 21 and 13, the delay element 14, and further passes through the switch 17 to become the current limit value command 18.

During regenerative braking in this state, when skidding occurs and the output of the skid detection means X, that is, the skid detection signal 12 becomes "1", the switches 13 and 17 are switched from the "0" side to "1" via the off-delay 34. Switch to the 1” side. At that time, when the output of the skid detection means X, that is, the all-axis skid detection signal 26 is "0", the output of the logic NOT circuit 27 is "1", so the output of the AND circuit 28 is "0". 1", and the switch 29 is switched from the "0" side to the "1" side. Therefore, the value of the current limit value command 18 passes through the sampling hold circuit 15 and enters the subtracter 10, and the subtracter 10 subtracts the current limit value reduction value 16 from the current limit value command 18 every sampling time. . Further, this reduced current limit value command 18 is inputted to the delay element 14 through the switch 13.

When the skid is completed and re-adhesion is confirmed, the skid detection signal 12 becomes "0", so the logic NOT circuit 2
Even if the output of 7 is “1”, the AND circuit 2
The output of switch 8 is “0” and the switch 29 is “1”
Switch from the side to the “0” side. When the switch 29 is switched to the "0" side, the zero command 33 is switched to the "0" side.
9 to the subtractor 10, current limit value command 1
8 is a decreased value and remains constant. Also, at the point when the skid detection signal 12 becomes "0", the output of the off-delay circuit 34 returns to "0" after a delay time 35, and the switches 13 and 17 return from the "1" side to the "0" side. . Therefore, the decreased current limit value command 18 will gradually return to the value of the basic current limit value command 11 because of the delay element 14.

Next, the V/F value control means Z will be explained with reference to FIG.

In other words, under normal conditions, the inverter output frequency is 36
The inverter output voltage calculation circuit 38 calculates the voltage command value from the
Since the outputs of the logic AND logic NOT circuit 48 are both "0", the output of the OR circuit 49 is "0", and the switch 39 and the switch 41 are on the "0" side), and the output is input to the rate of change limiter 40. Ru. This rate of change limiter 40 suppresses sudden voltage changes with respect to the voltage command value, and then passes through a switch 41 to become an inverter output voltage command 42.

When V/F control is performed in such a state, skidding occurs, and if the shafts actually skid, the all-axes skid detection signal 26 becomes "1" and the switch 3
0, the switch 39 and the switch 41 are switched from the "0" side to the "1" side through the OR circuit 49. As a result, the inverter output voltage command 42 is sampled and held by the sampling hold circuit 43 and input to the subtracter 44 . A subtracter 44 subtracts a value obtained by multiplying a voltage value reduction coefficient 45 by an inverter output frequency 36 every sampling time by a multiplier 46 from the inverter output voltage command 42. In this case, while the all-axis skid detection signal 26 is "1", the output of the AND circuit 28 in FIG. 4 becomes "0" and the switch 29 returns to the "0" side, so the current limit value command is 18 is kept constant.

If even one axis re-sticks from the state of sliding on all axes, it becomes the same as normal sliding and the sliding detection signal 1 in Figure 4 is generated.
2 becomes "1" and the output of the AND circuit 28 becomes "1", so the switches 13 and 17 become "0".
Current limit value command 1 because it switches from side to “1” side
8 decreases again due to the same effect as described above, but the inverter output voltage command 42 shown in FIG. Since they do not match, the output of the comparator 47 is "0", the output of the logic NOT circuit 48 is "1", and the switches 39 and 41 remain on the "1" side.
Further, the switch 30 returns from the "1" side to the "0" side when the all-axis slippage detection signal 26 becomes "0". Therefore, the sampling hold circuit 43
Since the inverter output voltage command 42 subtracted by the subtracter 44 is held until that time, the inverter output voltage is outputted as a constant value. Then, when the vehicle speed decreases in this state, the inverter output frequency 36 decreases, so the value of the inverter output voltage calculation circuit 38 also decreases. When the value matches the inverter output voltage command 42, the output of the comparator 47 becomes "1" and the output of the logic NOT circuit 48 becomes "0", so the switch 3
9 and switch 41 return from the "1" side to the "0" side. Therefore, the inverter output voltage command 42 shifts to the voltage command value calculated by the calculation circuit 38.

This series of operations is carried out in a cycle from when the inverter regeneration start command 20 shown in FIG. 4 becomes "1" and the inverter starts, until it becomes "0" and stops when all axes are sliding.

Figure 6 shows the current limit value when all axes are sliding as mentioned above.
The state of change in IB5 and change in inverter output voltage V value 6 is shown.

After the inverter is started, when one shaft begins to slide at time _t1 in Fig. 6, the current limit value IB5 begins to gradually decrease in order to reduce the braking torque of the induction motor. As the skidding expands, other wheels will start skidding one after another, potentially causing all axles to skid.

When sliding on all axes begins at time t ₁ , the current limit value IB
5 is kept constant at a decreased value from time t ₁ to t ₂ , and at the same time, the inverter output voltage V, which had hitherto followed a constant V/F pattern, begins to gradually decrease. When all axes sliding ends at time t ₃ and a normal sliding state is established, the inverter output voltage V maintains a constant value that decreased from time t ₂ to t ₃ . Eventually, the vehicle speed decreases and when the inverter output voltage V matches the inverter output voltage V value 6 determined by the constant V/F pattern at time _t5 , the constant V/F pattern is again used.

In this way, while all axes are sliding during regeneration (between times t ₂ and t ₃ ), all induction motors are in an unstable state, so the inverter output voltage is controlled by keeping the current limit value IB5 constant, and at time t ₃ After all axes have finished sliding, the braking torque is reduced by keeping the inverter output voltage constant and controlling the current limit value IB5 so that the slip frequency does not become extremely low.
It becomes possible to maintain the stability of the system when sliding on all axes.

Figure 7 shows a simple equivalent circuit diagram when an induction motor is operated by a VVVF inverter, where 50 is a filter capacitor, 51 is a VVVF converter section,
52, 53, and 54 are respectively an induction motor field component, an induction motor equivalent inductance, and an induction motor secondary resistance component, X is a slippage detection means, Y is a current limit value control means, and Z is a V/F control means.

In such a configuration, torque is determined by the current flowing through the induction motor field component 52 and the induction motor 2.
Since it is determined by the product of the current flowing through the next-side resistance 54, in order to reduce the braking torque, it is necessary to lower either or both of the above-mentioned current limit value and the inverter output voltage.

During normal sliding, by keeping the V/F value constant, the induction motor field component 52 is kept constant,
By reducing the slip S of the value R/S of the induction motor secondary side resistance 54 and increasing the R/S value, the flowing current is reduced and the braking torque is reduced, and in the case of all axes sliding, V/ By performing braking to lower the F value and reducing the current flowing through the induction motor field component 52, the braking torque can be lowered. In this case, the actual slip S of the sliding wheel
If it approaches 0, there is a risk that the inverter frequency F will become unstable, so the rate of change limit of the inverter frequency F may be selected at an appropriate value in consideration of the current limit value reduction rate, etc.

In addition, the braking torque decreases due to a decrease in the inverter output voltage V value 6, and if readhesion is confirmed even on one axis, the inverter output voltage V value remains constant and the inverter frequency F gradually decreases, so the V/F Although the value continues to follow a constant V/F pattern,
The current limit value IB5 continues to decrease while sliding even on one axis. Then, when readhesion of all axes is confirmed, the current limit value IB5 gradually returns to the value just before the start of skiing.

Thus, according to the embodiment of the present invention, VVVF
In a regenerative braking control system for an electric vehicle driven by multiple induction motors controlled by an inverter, if skidding on even one axis is detected during regeneration, the current limit value is decreased, and when all axes are skidding, the current limit value is reduced. By keeping the current limit value at a constant value, and reducing the inverter output voltage and lowering the V/F value, the braking torque is reduced, so the sliding wheels can be re-adhered while maintaining the stability of the system. It becomes easier to do. In addition, if even one axis re-adheres, the current limit value will be lowered as in the case of normal sliding, but
At this time, since the inverter output voltage V is maintained at a constant value while decreasing, the stability of the control system can be ensured. Furthermore, when the end of skiing is detected, the current limit value at that time is held for a certain period of time and then gradually returned to the basic current limit value, making it difficult to ski again even if the route is locally bad.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to reduce the braking torque of all wheels while maintaining the stability of the control system, making it easier for skidding wheels to re-stick, and to prevent re-slipping even if the route conditions are locally bad. To provide a regenerative braking control device for an electric vehicle, which is capable of making the electric vehicle run stably by making it difficult to repeatedly skid even when route conditions are bad overall.

[Brief explanation of the drawing]

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 V/F control for explaining an embodiment of the regenerative braking control device for an electric vehicle according to the present invention. The circuit diagram, FIG. 6 is a diagram showing the relationship between time and current limit value or time and V value in the same embodiment, and FIG. 7 is a diagram for explaining the device of the present invention.
FIG. 2 is a simplified equivalent circuit diagram of a VVVF inverter and an induction motor. 1...Minimum value detection signal, 2...Maximum value detection signal, 3...Switch, 4...Power running, regeneration discrimination signal, 5...Current limit value IB, 6...Inverter output voltage V, 11...Basic Current limit value command, 12...Sliding detection signal, 13, 17, 21, 23, 29, 39,
41, 55...Switch, 14...Delay element, 1
5, 43...sampling hold circuit, 16...
...Current limit value reduction value, 18...Current limit value command, 20...
Regeneration start command, 46... Multiplier, 26... All-axis slippage detection signal, 27, 48... Logic negation circuit, 28
...Logic product circuit, 22, 33, 56...Zero command, 34...Off delay, 35...Delay time,
36... Inverter output frequency, 37... Overhead line voltage, 38... 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...
...Resistance on the secondary side of the induction motor.

Claims (1)

[Claims] 1. A skid detection means X, a current limit value control means Y,
This is a regenerative braking control device for an electric vehicle having a V/F control means Z, in which the electric vehicle is powered or regeneratively braked by driving a plurality of induction motors M by one variable voltage variable frequency inverter 51. The skid detection means X detects skidding on all axes of the driving wheels or at least on one axis, and the current limit value control means Y detects basic current limit value command 11 and skid during regenerative braking. Input the output of detection means X,
If slippage of at least one axis is detected by the slippage detection means If the current limit value is gradually decreased and the sliding of the driving wheels is ended by the skid detection means X and the skid detection signal is not output and a state of re-adhesion occurs, the current limit value command 18 immediately before this is kept constant. output, induction motor M
During regenerative braking, the V/F control means Z inputs the skid detection signal from the skid detection means X, the overhead line voltage signal, and the inverter output frequency, and at least When shaft skidding is detected, a constant inverter output voltage command 42 is output, the ratio V/F between the output voltage V and the output frequency F of the inverter 51 is controlled to be constant, and the skidding detection means X detects that all shafts are skidding. is detected, the inverter output voltage command 42 is decreased by a predetermined value every sampling time, and the output voltage V and output frequency F of the inverter 51 are
A regenerative braking control device for electric vehicles that variably controls the V/F ratio. 2. Skid detection means X, current limit value control means Y,
This is a regenerative braking control device for an electric vehicle having a V/F control means Z, in which the electric vehicle is powered or regeneratively braked by driving a plurality of induction motors M by one variable voltage variable frequency inverter 51. The skid detection means X detects skidding on all axes of the driving wheels or at least on one axis, and the current limit value control means Y detects basic current limit value command 11 and skid detection during regenerative braking. Input the output of means X,
If at least one axis slip is detected by the slip detection means Gradually decreases the current limit value of , and when the sliding of the driving wheels ends and the skid detection signal is no longer output, the current limit value command 18 just before is output to control the current flowing to the induction motor M. , when all the axes are detected to be skidding by the skidding detection means gradually decreases the current limit value command 18, returns the current limit value command after a predetermined period of time after the skid detection means X no longer detects any skid on one axis, and the current limit value at that time becomes the value immediately before the skid. The inverter 51 is controlled until the current limit value is reached, and the V/F control means Z inputs the skid detection signal from the skid detection means X, the overhead wire voltage signal, and the inverter output frequency during regenerative braking. , when at least one shaft slip is detected by the slip detection means X, the ratio V/F between the output voltage V and the output frequency F of the inverter 51 is kept constant, and the slip detection means If so, the inverter output voltage command 42 is decreased by a predetermined value every sampling time, and the inverter output voltage command 42 is decreased by a predetermined value every sampling time.
The braking torque is controlled by decreasing the ratio V/F between the output voltage V and the output frequency F of If the voltage command value of the inverter 51 and the inverter output voltage command value 42 are compared, the V/F value is determined to be V/F.
A regenerative braking control device for electric vehicles that waits until the voltage command value matches the pattern.