JPH0524722B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a brake control device for an electric vehicle that is designed to improve the regeneration rate.

<Prior Art> Conventionally, there has been a device of this type as shown in FIG. In the figure, 1 is a contact wire, 2 is a pantograph, 3 is a filter reactor, and 4 is a filter capacitor. The filter reactor 3 and the filter capacitor 4 constitute an inverted L-shaped filter circuit. 5 is a backflow blocking diode, 6 is a chopper,
7 is the main smoothing reactor, 8 is the field winding of the motor,
Reference numeral 9 denotes an armature winding of the motor, and the field winding 8 and armature winding 9 constitute a DC winding motor. 1
0 is a brake resistance, which is inserted in series with the armature winding 9 in the high speed range in order to expand the regeneration and braking area. Reference numeral 11 is a switch, which is turned on when the speed reaches the medium speed range and the conditions for short-circuiting the brake resistor 10 are established.
The brake resistor 10 is short-circuited, and the switch 11 remains on until the brake is turned off or the regenerative brake is disabled and the main circuit is turned off just before the brake is stopped. FIG. 2 shows the relationship between speed V and motor current I _M.

In the figure, a curve a shows a characteristic when the voltage of the series body of the armature winding 9 and the brake resistor 10 is controlled to be constant in a state where the brake resistor 10 is inserted. In order to maximize the regeneration area and improve the regeneration rate, it is desirable to set this voltage as high as possible. In this case, the conductivity of the chopper 6 on the curve a becomes approximately the minimum conductivity. Similarly, curve b shows the characteristics when the voltage of armature winding 9 is controlled to be constant when brake resistor 10 is short-circuited by switch 11, and on curve b, the current conductivity of chopper 6 is Almost the minimum conduction rate. When you apply the brakes from a speed of V ₁ ,
Motor current I _M changes from point A → point B → as the speed decreases.
It is controlled by passing from point C to point D. The region from point A to point B is the region where the conductivity of the chopper 6 is controlled so that the voltage of the series body with the armature winding 9 and the brake resistor 10 is constant. The electromotive force is _EM , the resistance value of the brake resistor 10 is R,
When the motor current is I _M , the conductivity of the chopper 6 is γ, and the voltage of the filter capacitor 4 is E _C , the following equation holds true in the region from point A to point B.

From _{this formula} , armature winding 9 and _brake resistance 10
Since the voltage of the series body with is expressed as E _M -I _M · R = (1 - γ) E _C , it can be seen that if E _C is considered constant, the conduction rate γ becomes constant as a result. and,
This conductivity rate γ is controlled to be the minimum conductivity rate γmin in order to make the regeneration rate as high as possible. B
In the region from point to point C, as the speed decreases, the electromotive force E _M in the armature winding 9 also decreases, so the chopper 6 gradually increases the conduction rate so that the motor current I _M reaches the command value. I is controlled to be equal to ₀ . In the area from point B to point C, the following equation holds true.

E _M =I ₀ ·R + (1-γ) E _C The brake resistor 10 is short-circuited by the switch 11 at a point C where it intersects the characteristic curve b with the brake resistor 10 short-circuited. At this time, the conductivity γ
The flow rate is then narrowed down to the minimum flow rate γmin, and as the speed decreases, it gradually expands again. In the area from point C to point D, the following formula holds: E _M = (1 - γ) E _C On the other hand, contact line 1 is passed through filter actor 3
The regenerative current I _S regenerated in the area becomes I _S = (1-γ) _IM , so if the regenerative current I _S in each region is calculated and illustrated, it will be as shown in Figure 3, and the regenerative current I _S will be as shown in Figure 3. It changes as shown by the solid line A→B→C→C′→D. Points A, B, C, and D are A, B, and D in Figure 2, respectively.
It corresponds to each point C and D.

However, the conventional method has the following drawbacks. That is, when the brake resistor 10 is short-circuited by the switch 11 at point C, the voltage I ₀ ·R that had been dropping across the brake resistor 10 before the short-circuit is reduced.
is applied to the chopper 6 in steps. Or, to put it another way, before the short circuit,
While the chopper 6 is controlling the constant current with E _M −I ₀ R as the apparent motor electromotive force, the motor electromotive force changes stepwise to E _M at point C, and is stabilized by the constant current control system. Otherwise, overcurrent detection due to a surge in the motor current I _M and overvoltage detection due to a surge in the voltage of the filter capacitor 4 may occur. The amount of these splashes increases as the voltage fluctuation I ₀ R increases, so there is an upper limit to the value of the brake series resistor 10, and there is also a limit to the expansion of the regeneration area.

<Summary of the Invention> This invention was made to solve the above-mentioned drawbacks of the conventional brake resistor, and a semiconductor switch is connected in parallel to a brake resistor to perform a chopping operation, and the conduction rate is controlled. Accordingly, there is provided a brake control device for an electric vehicle that can smoothly short-circuit the brake resistance and expand the regeneration area.

<Embodiment of the invention> An embodiment of the invention is shown in FIG. In the figure,
1 to 10 are the same as the conventional ones. 12 is a gate turn-off thyristor GTO having a self-extinguishing function as a semiconductor switch connected in parallel with the brake resistor 10 in place of the conventional switch 11;
13 is a control circuit. Next, the operation will be explained. If the resistance value of the brake resistor 10 is the same as the conventional one, the relationship between the speed V and the motor current I _M will be the same as in FIG. 2, but the control method is partially different. That is, in the region from point A to point B, the only difference from the conventional method is that the brake resistor 10 is inserted by keeping the GTO 12 in an OFF state. from point B to C
In the region indicated by the point, the conventional motor controls the motor current I _M to be equal to the command value I ₀ by gradually increasing the conduction rate γ of the chopper 6 as the speed V decreases. In contrast, in this embodiment, the control circuit 13 performs control as follows.
That is, the GTO 12 is operated in a chopping operation while the conduction rate γ of the chopper 6 is kept at γmin, and by gradually increasing the conduction rate, the motor current I _M is controlled to be equal to the command value I ₀ . GTO12
When the brake resistor 10 and the GTO 12 are operated in a chopping operation at a constant cycle, and the conduction rate is δ, the parallel body of the brake resistor 10 and the GTO 12 can be regarded as a resistor having an apparent resistance value of (1−δ)R. Therefore, in this embodiment, the following equation holds true in the area from point B to point C.

E _M =I _M (1-δ)R+(1-γmin)E _CThe regenerative current I _S in this example is illustrated as 5th
It will look like the figure. Unlike the conventional one, the conduction rate of the chopper 6 is fixed at γmin in the region from point B to point C, so the regenerative current I _S is I _S = (1
-γmin)I ₀ , and follows the solid line B-C' in the figure. Therefore, compared to the conventional one, the triangular
Regenerative power increases by the area surrounded by BCC′. Furthermore, in this embodiment, the brake resistor 10 is short-circuited by gradually increasing the chopping conductivity δ of the GTO 12 from 0 to 1, so unlike the conventional one, the brake resistor 10 is short-circuited by gradually increasing the chopping conductivity δ of the GTO 12 from 0 to 1. No motor overcurrent or overvoltage of the filter capacitor 4 occurs. Also, when calculating the loss of the brake series resistor 10 in the area from point B to point C, in the conventional one, ∫ ^T ₀ I ₀ ²・Rdt=
In this example, ∫ ^{T 0} I ₀ ²・R (1 _{- t} /T) dt=I ₀ ²・R・T/2(joul
e) Since the loss of the brake resistor 10 is halved in the region from point B to point C, the brake resistor 10 can be made smaller and lighter.

In addition, as described above, according to this embodiment, there is no voltage fluctuation caused by a resistor short circuit as in the conventional one, so there is no upper limit to the resistance R, and regeneration can be performed within the range allowed by the size of the brake resistor 10 and the electromotive force of the motor. It is possible to expand the area. As an example, in Fig. 6, the regenerative current I _S when the resistance value R is increased is shown as a solid line E→F→B→
It is shown as C'→D. On the other hand, in the region from point C' to point D, the brake resistor 10 is completely short-circuited by keeping the GTO 12 on, so the control method is the same as the conventional one.

In Fig. 4, the semiconductor switch connected in parallel to the brake resistor 10 is explained as a GTO, but a switch using a reverse conduction or reverse blocking thyristor, a power transistor, a static induction thyristor, etc. may also be used. Obviously not.

<Effects of the Invention> As explained above, according to the present invention, a semiconductor switch is connected in parallel to a brake resistor to perform a chopping operation, and the conduction of the semiconductor switch is fixed while the conduction rate of the chopper is fixed to the minimum. Since the current of the motor is controlled to be equal to the command value by sequentially increasing the flow rate, short-circuiting of the brake resistor is performed smoothly and the amount of regenerated electric power is increased. Furthermore, there is no upper limit to the resistance value of the brake resistor, and the regeneration area can be expanded, since there is no restriction such as voltage fluctuation when the resistor is short-circuited.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing a conventional braking control device for electric vehicles, Figs. 2 and 3 are characteristic diagrams showing the speed-motor current and speed-regenerative current relationships, respectively, in the case of Fig. 1. The figure is a circuit diagram showing a braking control device for an electric vehicle according to an embodiment of the present invention, FIG. 5 is a characteristic diagram showing the relationship between speed and regenerative current in the case of FIG. 4, and FIG. FIG. 3 is a characteristic diagram showing the relationship between speed and regenerative current when the resistance value of a series resistor is increased. In the figure, 6 is a chopper, 8 and 9 are field windings and armature windings that constitute the motor, and 10
1 is a brake resistor, 12 is a semiconductor switch, and 13 is a control circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. A control device for an electric vehicle having a control circuit 13, in which the electric vehicle has a drive motor 8, 9 and a brake resistor 10 connected in series after the chopper 6, A semiconductor switch 12 is connected in parallel with the brake resistor 10 to perform regenerative braking control, and the control circuit 13 turns off the semiconductor switch 12 and disconnects the armature winding 9 of the motor in the high speed range of the electric vehicle. The current flow rate of the chopper 6 is controlled so that the voltage across the series body with the brake resistor 10 is constant, the speed of the electric car decreases, and the current of the electric motors 8 and 9 increases,
In the region where the command value is reached and the conduction rate of the chopper 6 is fixed, the conduction rate of the semiconductor switch 12 is gradually expanded to make the currents of the motors 8 and 9 equal to the command value, and the conduction rate of the semiconductor switch 12 is increased. A brake control device for an electric vehicle that controls the conduction rate of the chopper 6 so that the current of the electric motors 8 and 9 becomes equal to the command value after the current rate reaches the maximum.