JPS6129202B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a chopper protection device for electric vehicles, and in particular, a series circuit consisting of a regenerative energy absorbing resistor and a thyristor is connected in parallel with a filter capacitor, electrically separated from the power supply line, and the motor current is controlled. In an electric vehicle chopper device for controlling a motor, the filter capacitor voltage and motor current are monitored to prevent chopper commutation failures that occur due to low electromotive force of the motor at low speeds.

Figure 1 shows the main circuit during regenerative braking of a typical electric vehicle Chotsupa. In the figure, 1 is the power supply line, 2
is a current collector, 3 is a unit switch, 4 is a filter reactor, 5 is a filter capacitor, 6 is a voltage detection device for detecting the voltage of the filter capacitor 5, 7 is a resistor for overvoltage suppression, 8 is a thyristor for overvoltage suppression, 9 is a freewheel diode, 10
11 is a main smoothing reactor, 12 and 13 are the motor field and armature, and 14 is for detecting the motor current. It is a current detection device.

On the other hand, TR simply indicates another power running vehicle that serves as a regenerative load for the above-mentioned chopper device, and the current collector 1
5, comprising a unit switch 16 and an equivalent resistance 17;
This resistance value is determined by the number of power running vehicles and the main circuit mode of the power running vehicles.

In Fig. 1, during regenerative braking, if the conduction rate of the chopper 10 is γ ₁ at the motor current I _M1 , then
From the Chiyotupa car, I _M1 (1-
A current of γ ₁ ) is regenerated to the other power running vehicle TR,
It is consumed by the equivalent resistance 17.

Let the current drawn by the equivalent resistance 17 be I _R , and if I _R > I _M1 (1 - γ ₁ )...(1), the differential current I _R - I _M1 ( 1−γ ₁ ) will flow into the system. However, if the resistance value of the equivalent resistance 17 is large and I _R <I _M1 (1-γ ₁ ) ...(2), the current I _M regenerated from the chopper car
_1. (1-γ ₁ ) cannot be absorbed completely, so the voltage of the filter capacitor 5 increases.

In the conventional chopper device, in order to suppress the voltage rise of the filter capacitor 5, the motor current pattern, which is a reference value for control, is lowered by a limiter called an overhead line voltage limiter, and the motor current I _M is narrowed down to I _M1 ' ( That is, I _M1 ′<I _M
1 ), thus the current of the equivalent resistance 17 is I _R =I _M
It is controlled so that it becomes ₁ '·(1-γ ₁ '). In this case, the lack of braking force due to the reduced motor current is supplemented by the air brake.

In addition, in the state shown in Fig. 1, when another power running vehicle TR is notched off and the unit switch 16 is turned off, the regenerative load is abruptly cut off, so the filter capacitor 5
voltage increases rapidly. This rising speed is much faster than the response speed of the control system of the chopper 10 including the overhead wire voltage limiter, and therefore the rise in the voltage of the filter capacitor 5 cannot be suppressed. Therefore, when the voltage of the filter capacitor 5 reaches a specified value (usually 1.2 times the rated overhead line voltage), the overvoltage suppressing thyristor 8 is ignited, and the overvoltage suppressing resistor 7 is inserted.
The voltage accumulated in the filter capacitor 5 is suppressed by discharging the charge accumulated in the filter capacitor 5, and the main circuit is cut off.
From now on, use only the air brake to generate the necessary braking force.

In this way, with conventional chopper devices, when the regenerative load is insufficient, the motor current is reduced from the required value, and the shortage is supplemented with the air brake.
On the other hand, when the regenerative load is cut off and the voltage of the filter capacitor 5 exceeds the specified value, the overvoltage suppressing thyristor 8 is fired to suppress the voltage of the filter capacitor 5 and the main circuit is cut off. The necessary braking force is generated using only the air brake.

However, in the case of a restraining brake for driving at a constant speed on a downhill section, all the braking force is normally provided by the electric brake. This is to prevent the brake shoe and wheels from overheating when the air brake is continuously used on a slope section, and to prevent shortening of the life of the brake shoe and wheels due to significant wear.

Therefore, even in Chiyotsupa vehicles, when braking at low speed, all of the braking force must be borne by regenerative braking, but as mentioned above, the regenerative load is small,
When the regenerative current cannot be absorbed sufficiently, the motor current is narrowed down from the required value (the current value uniquely determined from the restraining speed, slope, and load conditions), and the restraining braking force is insufficient, causing the vehicle to increase. This is dangerous as it will speed up the process.

As a method to compensate for this point and guarantee the necessary electric braking force even when the regenerative load is small, a method as shown in Figure 2, in which the corresponding parts to those in Figure 1 are given the same reference numerals, has been considered. . In FIG. 2, the resistor 7 is selected to have a large capacity as a resistor for absorbing regenerative energy.

When regenerative brake control is being performed in the regenerative brake circuit shown in FIG. The voltage of the filter capacitor 5 is suppressed by discharging the excess accumulated charge in the filter capacitor 5, and the motor current is controlled at a predetermined value by absorbing the power generated from the motor with the resistor 7, thus controlling the motor current at a predetermined value. Get electric brakes. In addition, in order to prevent unnecessary current from flowing from the power supply line 1, the unit switch 3 is turned on after igniting the thyristor 8.
is opened to separate the brake main circuit from the power supply line 1. The state of the main circuit at this time is as shown in FIG.

In the state of the main circuit as shown in Figure 2,
The following equation holds between the voltage E _c of the filter capacitor 5, the motor voltage E _M , the motor current I _M , and the conduction rate γ of the chopper 10. Note that the main circuit internal resistance is ignored, and R represents the resistance value of the resistor 7.

E _M =(1-γ)E _c (1) E _c =(1-γ) I _M ·R (2) Furthermore, the motor voltage E _M is expressed by the following equation.

E _M = KVφ (I _M ) ...(3) Here, K is a constant, V is the speed of the vehicle, and φ (I _M )
represents the magnetic flux of the field.

From equations (1), (2), and (3), E _M = KVφ (I _M ) = (1-γ) ² I _M・R ...(4), so becomes.

Now, considering the case where the motor current I _M is controlled to a certain constant value, on the right side of equation (5), I _M , φ
Since (I _M ), K, and R are constant, the right side becomes smaller as the speed V decreases. Accordingly, the conductivity γ of the chopper 10 also increases accordingly. Therefore, as is clear from equation (2), the voltage E _c of the filter capacitor 5 also decreases.

As this condition progresses, the tipper will fail in commutation as will be explained next. Therefore, in the past, the gate pulse was stopped when the voltage of the filter capacitor reached the lowest value that allowed the maximum current to be commutated.

FIG. 3 shows the chopper 10 in the circuit of FIG.
The chopper circuit 10 is shown in detail in order to explain the commutation ability of the main thyristor 18.
19 is an auxiliary thyristor for commutation, 20 is a capacitor for commutation, and 21 is a reactor for commutation. Here, the thyristors 18 and 19 are reverse conducting thyristors having diode characteristics in the opposite direction.

In order to simplify the explanation, waveforms of various parts during commutation are shown as shown in FIG. 4, ignoring losses in the commutation circuit. When the main thyristor 18 is fired at time _t1 , an on-current I _M flows as shown in FIG. 4A. In order to commutate this current and turn it off, when the auxiliary thyristor 19 is ignited at time _t2 , the charges accumulated in the commutating capacitor 20 with the polarity shown in the figure are transferred to the commutating capacitor 20 - auxiliary thyristor 16 - commutation reactor 21 - The closed loop consisting of the main thyristor 18 resonates, and a commutation current I _T having a peak value I _P as shown in FIG. 4B flows.

Here, the current flowing through the main thyristor 18 is
As shown in Figure A, since the commutation current is superimposed on the on-current I _M , it also flows in the negative direction, and thus the main thyristor 18 is reverse biased for the time ΔT from time t ₃ to time t ₄ as shown by the diagonal line. will be done.
If this reverse bias time ΔT is shorter than a time specific to the element used in the main thyristor 18 (usually referred to as a turn-off time), the main thyristor 18 will not be turned off completely and commutation will fail.

This reverse bias time will vary depending on the magnitude of the on-current I _M and the magnitude of the voltage of the commutating capacitor 20. In other words, once the constants of the commutation circuit of the chopper 10 are determined, the lower limit of the voltage of the commutation capacitor 20 required to commutate a certain on-current I _M is uniquely determined, and the lower limit of the voltage of the commutation capacitor 20 is determined. The relationship E _cMc =C _O I _M (6) holds between E _cMc and on-state current I _M . Here, C _O is a value determined by the constants of the commutation circuit.

By the way, since the voltage of the commutating capacitor 20 is charged to the same potential as the capacitor 5 when the main thyristor 18 is turned off, the voltage of the commutating capacitor 20 becomes equal to the voltage E _c of the filter capacitor 5. That is, E _c = E _cMc = C _p · I _M ... (7) Therefore, as mentioned above, as the speed of the vehicle decreases, the voltage E _c of the filter capacitor 5 decreases, and finally, as expressed by equation (7). When the current I M is lower than the value C _p ·I _M , it is no longer possible to commutate the motor current I _M and the chopper 10 fails to commutate.

In consideration of the above points, the present invention monitors only the filter capacitor voltage and stops the gate pulse in order to prevent commutation failure at low speeds in the conventional example. To provide a chopper protection device for an electric vehicle which can perform chopper operation in as wide a range as possible by monitoring both currents and stopping gate pulses.

An example of the present invention will be described in detail below with reference to FIG. 5, in which parts corresponding to those in FIG. 2 are denoted by the same reference numerals. 2
1 is a unit switch for opening the main circuit, 22
is a pattern generation circuit which receives the motor current value I _M which is the output of the current detection device 14 as an input and generates an output E _MINP expressed as E _MINP = C _p I _M + E _p (8). Here, C _p is a constant shown in equation (7), and E _p is a bias value for giving a margin to the detected value.

Further, 23 compares the output from the pattern circuit 22 and the voltage E _c of the filter capacitor 5 which is the output from the voltage detection device 6, and outputs an output when E _c ≦E _MINP (9). A comparison circuit 24 receives the output from the comparison circuit 23 and turns off the solenoid valve 26 of the unit switch 21. 25 receives the output from the comparison circuit 23 and stops the gate pulse of the chopper 10. It is a circuit.

As shown in FIG. 6, the pattern generation circuit 22 has a characteristic that is
Bias the margin E _p with respect to _M , and gain C _p
Outputs an output E _MINP that changes linearly by multiplying by . If the maximum current to be controlled here is I _MO and E _MINP in FIG. 6 at that time is E _MINPO , then in the conventional example, the filter capacitor voltage at which the gate pulse stops is E _MINPO regardless of I _M.
Since the present invention changes the voltage of E _MINP according to I _M as shown in FIG. 6, the chopper can be effectively operated down to a lower filter capacitor voltage.

In _the configuration shown in FIG _. 5 _, when the motor current I _M is controlled to I _MI as _shown in FIG. Become.

When the speed of the electric car decreases and the voltage E _c of the filter capacitor 5 becomes less than E _MINPl as shown in FIG. 7B, the comparator circuit 22 changes as shown in FIG. 7C.
operates and sends out an on output, and as shown in FIG. 7D, the solenoid valve 26 is turned off, and at the same time, although not shown, the gate pulse of the chopper 10 is stopped.
Thus, commutation failure is prevented. When the chopper 10 stops, the motor current I _M and the voltage E _C of the filter capacitor 5 are attenuated, and the main contact of the unit switch 21 is turned off as shown in FIG.
The motor circuit is completely disconnected.

As described above, according to the present invention, in an electric vehicle chopper device that connects a series circuit of a regenerative energy absorbing resistor and a thyristor in parallel with a filter capacitor, and controls the motor current by electrically separating it from the power supply line, Since the outputs of the conventional filter capacitor voltage detection device and motor current detection device are used without adding any special equipment, in the conventional example, the filter capacitor voltage that stops the gate pulse at any motor current is On the other hand, the filter capacitor voltage that stops the gate pulse decreases according to the motor current, making it possible to effectively perform chopper operation down to a lower voltage. It is possible to prevent commutation failure.

Note that the present invention can be similarly applied to a system in which the brake main circuit is separated from the power supply line 11 by providing a diode 27 to prevent reverse flow during braking, as shown in FIG.

[Brief explanation of the drawing]

Fig. 1 is a connection diagram showing a typical chopper regeneration main circuit, Fig. 2 is a connection diagram showing a main circuit to which the present invention can be applied, Fig. 3 is a connection diagram showing the detailed configuration of Fig. 2, and Fig. 4 is a connection diagram showing the main circuit to which the present invention can be applied. Figures A to C are signal waveform diagrams for explaining the principle of the present invention, Figure 5 is a systematic connection diagram showing an example of the electric vehicle chopper protection device according to the present invention, and Figures 6 and 7 A to E are FIG. 5 is a characteristic diagram and signal waveform diagram for explaining the operation, and FIG. 8 is a connection diagram showing another main circuit to which the present invention can be applied. 1...Power supply line, 3...Unit switch, 5...Filter capacitor, 6...Voltage detection device, 7...
Resistor, 8...Thyristor, 10...Chiyotsupa,
12... Field, 13... Armature, 14... Current detection device, 21... Unit switch, 22... Pattern circuit, 23... Comparison circuit, 24... Solenoid valve off circuit, 25... Gate pulse Stop circuit, 26...
Solenoid valve for unit switch.

Claims (1)

[Scope of Claims] 1. A regenerative energy absorption circuit comprising a filter capacitor charged by the generated current of the main motor, and a series circuit of a resistor and a semiconductor element connected in parallel with the filter capacitor; In an electric vehicle chopper control device that includes a separation means for electrically separating a capacitor and a power supply line, and separates the regenerative energy absorption circuit from the power supply line to chipper control the main motor current, the voltage of the filter capacitor is a voltage detection device that detects the traction motor current, a current detection device that detects the traction motor current, and a pattern generation circuit that generates a pattern voltage according to the output from the current detection device. Compares the output of the pattern generation circuit with the output of the voltage detection device, detects that the output of the voltage detection device is below the pattern voltage, stops the chopper, and turns off the main circuit. An electric car chip protection device that is characterized by: 2. The electric vehicle chopper protection device according to claim 1, wherein the separation means is a strip inserted between the filter capacitor and the power supply line. 3. The electric vehicle chopper protection device according to claim 1, wherein the separation means comprises a diode having an anode connected to the filter capacitor and a cathode connected to the power supply line.