JPH02146901A - Power supply system for dc electric vehicle - Google Patents

Abstract

PURPOSE:To set DC output voltage to a level lower than a specific level by decreasing the chopping frequency if the DC output voltage produced through a two-quadrant step-down chopper mounted on a DC electric vehicle is higher than the specific level. CONSTITUTION:A two-quadrant chopper 23 is formed of a step-down chopper 231, a step-up chopper 232, a reactor 233 and a capacitor 234, then DC voltage is subjected to conversion and fed to various facilities in a car. Chopper output voltage detected through a voltage detector 235 comprising a resistor and a CT and the voltage to be set through an output voltage setter 237 are fed to a control circuit 236 and a chopper frequency command circuit 239. The chopper frequency command circuit 239 provides the set frequency to the control circuit 236 through a chopper frequency setting circuit 238. When the voltage detected through the detector 235 is higher than the voltage set through the output voltage setter 237, the control circuit 236 lowers the chopper frequency thus lowering the chopper output voltage. By such arrangement, facilities in the car are protected against overvoltage.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a power supply system for a DC electric car formed by a plurality of vehicles including a vehicle equipped with a two-quadrant chopper.

(Prior Art) For the purpose of simplifying and reducing the cost of the entire power supply system for electric vehicles, there is a power supply system proposed in, for example, Japanese Patent Application No. 62-225364.

The basic principle of this method will be briefly explained below.

First, a DC-DC converter such as a chopper capable of two-quadrant operation is installed in a DC electric car to step down the high voltage of the overhead contact line to a desired voltage. Next, this stepped-down DC voltage is supplied to a power converter for driving the electric motor via a lead-in line (hereinafter referred to as a "low-voltage DC power supply line") connected to each vehicle, as well as lighting and air conditioning equipment. It also supplies power to auxiliary power supplies for various equipment including.

FIG. 5 is a specific circuit diagram showing this method. The circuit breaker 2 is inserted into the vehicle 2 from the overhead contact line 1 by the pantograph 20.
1 and the high voltage DC power taken in through the input filter 22 is input to the DC-DC converter 23. This DC-DC converter 23 steps down the DC input voltage,
This step-down DC power is transmitted to the motor drive power converters 27 and 37 provided in the vehicles 2 and 3, the auxiliary power supply devices 28 and 38, and the auxiliary power supply provided in the vehicle 4 via the low voltage DC power supply lines 25 and 26. 48.

Here, the electric motor drive power conversion device 27 is the inverter 2
71 and a filter capacitor 272, the motor drive power conversion device 37 is constructed from an inverter 371 and a filter capacitor 372, respectively, and each power conversion device [2
7, 37 are induction motors (IM) 29a-29d, 39a-39d for converting DC input power into AC power and driving the vehicle.
The auxiliary power supply devices 28, 38 and 48 respectively supply power to various equipment such as lighting.

FIG. 6 is a circuit diagram showing a specific example of the DC-DC converter 23. This DC-DC converter 23 is a so-called two-quadrant chopper (reversible current chopper), and each of the two-quadrant choppers is a step-down chopper 231. Boosting chopper 232, reactor 233 and capacitor 2
It is composed of a filter consisting of 34.

As is well known, such a DC-DC converter 23 operates as a step-down chopper when the current is in the direction of arrow A1 shown in FIG. 6, and operates as a step-up chopper when the current is in the direction of arrow A. It works as. The output voltage is controlled to a voltage level applicable to general industrial equipment, for example, about 600V.

With this control, for example, in the vehicle 2, the low voltage DC power supply line 25, 26 to 60
A voltage of about 0 V is supplied. Therefore, when a VVVF inverter is employed as the inverter 271, general industrial transistors can be used as switching elements of the VVVF inverter.

FIG. 7 is a circuit diagram showing an example of such an inverter 271. In the figure, an inverter 271 includes a three-phase bridge circuit 273 made up of transistors. Furthermore, a snubber circuit 274 is provided between the input terminals of this bridge circuit 273, which acts on each transistor at once.

On the other hand, power is also supplied to the auxiliary power supply device 28 of the vehicle 2 via the low voltage DC power supply lines 25 and 26, but in this case as well, it is possible to use a device constructed from general industrial equipment as the auxiliary power supply device 28. becomes. FIG. 8 is a circuit diagram showing an example of such an auxiliary power supply device 28. In the figure, DC power is supplied to inverter air conditioners 281 to 283 and a transistor-type auxiliary power supply 284 via low-voltage DC power supply lines 25 and 26.

The auxiliary power supply 284 then connects the three-phase load 285 . Illuminator 28
It supplies power to loads such as No. 6.

Although the power supply system for the vehicle 2 in FIG. 5 has been described above, the same applies to the power supply system for the vehicle 3. That is, for vehicle 3.

DC power is supplied via the low voltage DC power supply lines 25 and 26, and as in the case of the vehicle 2, power is supplied to the vehicle drive induction motors 39a to 39d via the motor drive power conversion device 37. Further, power is also supplied to the auxiliary power supply device 38 from the same low voltage DC power supply lines 25 and 26. Furthermore, DC power is also supplied to the vehicle 4 shown as a non-electric vehicle in FIG. Driven.

Conventionally, the two-quadrant chopper (DC-DC converter 23) shown in FIG. Not done.

(Problem M to be solved by the invention) By the way, the voltage on the step-down side (non-contact line side) of the two-quadrant chopper as the DC-DC converter 23 (hereinafter referred to as "output voltage") is determined by the conductivity of the chopper. is maintained at the specified value by control. However, as mentioned above, the motor drive power converter and auxiliary power supply are connected in parallel to the output side of the two-quadrant chopper, and due to the operation of these devices, the load on the two-quadrant chopper is close to no load. It varies greatly from light load to maximum load. Furthermore, it is difficult to know this change in load in advance. At the same time, the two-quadrant chopper converts the high voltage on the contact line side (hereinafter referred to as "input voltage") to a lower voltage by controlling the conductivity, and when the load decreases, the two-quadrant chopper lowers the output voltage to the specified value. The output voltage will exceed the specified value.

For this reason, the following problems have conventionally occurred.

(1) When using a GTO thyristor or power transistor, which is generally used as a semiconductor switching element, as a switching element in a two-quadrant chopper, a minimum conduction time is determined, and this cannot be made infinitely small. When the voltage is small, the output voltage will exceed the desired value even if an attempt is made to supply the desired power required by the load.

FIG. 9 shows the glue handle 233 when the two-quadrant chopper of FIG. 6 is operating at the operating frequency f and the minimum conduction time.
FIG. 3 is a waveform diagram showing how the current IC flowing through the two-quadrant chopper and the output voltage v of the two-quadrant chopper change.

In the waveform diagram of the current IC in FIG. 9, the minimum conduction time Tosm
When it is in, it increases to the peak current value I, and the chopper is turned off. It is shown that iL decreases and reaches zero before the next turn on. As a result, an average current It flows through the reactor 203. Here, if the load current d is smaller than the average current IL, the capacitor 234 is charged until the two currents d and IL are balanced, and the terminal voltage thereof increases.

As this capacitor 234 is charged, I
+, decreases.

Also, in the waveform diagram of voltage v2 in FIG.

A case is shown in which the output voltage v2 of the two-quadrant chopper is larger than the specified value vd. Here, vl is the voltage on the input side of the two-quadrant chopper. Output voltage Vz is specified value■
If it is larger than d, the small-capacity equipment connected to the high-power side of the two-quadrant chopper (for example, the auxiliary power supply 284 in Fig. 8)
．． Load 285. (e.g., illuminator 286) may become overvoltage, causing these devices to become uncontrollable or malfunction.

(2) Furthermore, as mentioned above, the low voltage DC power supply line 25.26
In a power supply system in which a power conversion device for driving a motor, an auxiliary power supply device, etc. are connected to a power supply system, these various devices are designed to handle low voltage. Therefore, if an abnormal operation or failure occurs in the two-quadrant chopper, the low voltage DC power supply line 25.2
The high voltage of overhead contact line 1 is added to 6, and the above feeder line 25.26
A major problem was that dangerous overvoltage was applied to various equipment and equipment connected to the equipment.

For this reason, in the conventional system, the reliability of the two-quadrant chopper as the DC-DC converter 23 is increased, or a gapless arrester is connected to the low-voltage DC power supply line 25.26, so that the low-voltage DC power supply line 25.26 is exposed to overvoltage. was prevented from occurring. However, all of these preventive measures have been major obstacles to realizing a power supply system, such as increasing the price, weight, and size of the device.

The present invention was made to solve the above-mentioned problems, and the output side voltage does not increase beyond the specified value even under light load, and overvoltage occurs on the output side of the 52-quadrant chopper. It is an object of the present invention to provide a power supply system for a DC electric vehicle that promptly opens the two-quadrant chopper from the high-voltage input side.

(Means for solving il1 head) The above problem is that even in buck operation, the buck chopper is operated at a constant frequency while the boost chopper is turned off, so if this operation is performed at a light load, , The output voltage of the two-quadrant chopper cannot be maintained at the specified value due to the minimum conduction time of the semiconductor switching element of the step-down chopper, and changes in the load cannot be predicted in advance, resulting in abnormal operation or failure of the two-quadrant chopper. This is due to the fact that when this occurs, the occurrence of overvoltage in the low-voltage DC power supply line is prevented after the fact by using a gapless arrester or the like. Note that, conventionally, it has not been considered to change the chopping frequency or to open the chopper output side from the input side when the load is light.

Therefore, when the output voltage cannot be maintained at the specified value due to operation at the minimum conduction time or a conduction time close to the minimum conduction time, the inventors believe that the situation is equivalent to the situation in which the conduction rate of the output of a two-quadrant chopper is reduced. For this purpose, the output voltage of the two-quadrant chopper can be maintained at the specified value by reducing the chopping frequency, and the output voltage (low voltage side) of the two-quadrant chopper can be monitored to ensure that it does not exceed the specified overvoltage. , the semiconductor switching element for the step-up chopper is forcibly turned on, the step-down chopper circuit is opened, and the input side (
It was discovered that overvoltage in low-voltage DC power lines can be prevented by opening the line from the high-voltage side.

That is, the first invention is characterized in that when the output voltage of the two-quadrant chopper exceeds a specified value, the chopping frequency of the two-quadrant chopper is reduced to make the output voltage below the specified value; The invention detects the output side voltage by a detector provided on the output side of the two-quadrant chopper, and when the output side voltage exceeds a specified overvoltage value, the step-up semiconductor switching element constituting the two-quadrant chopper detects the output side voltage. is turned on to short-circuit the output side, and the short-circuit current flowing from the input side to the step-up semiconductor switching element is cut off by input opening means such as a fuse provided on the input side of the two-quadrant chopper.

(Function) In the first invention, when the load of the two-quadrant chopper decreases and the output voltage cannot be maintained at the specified value, the chopping frequency is lowered in accordance with the increase in the output voltage, and the chopping frequency is reduced equivalently in accordance with the load. Make it conductive. As a result, even if the load is light, the input side of devices connected to the two-quadrant chopper will not become overvoltage. At this time, since the load is small, even if a harmonic current with a reduced chopping frequency occurs, the effect on the overhead contact line is small and does not pose a problem.

In the second invention, when an overvoltage occurs in the low-voltage DC power supply line due to a short-circuit failure of the step-down chopper on the input side, the step-up chopper on the output side of the two-quadrant chopper is quickly and forcibly turned on, and the power is turned off. Short circuited. This suppresses dangerous overvoltage in the low-voltage DC power supply line, and prevents excessive current from flowing into the boost chopper by blowing out the fuse, which serves as an input opening means provided on the input side of the two-quadrant chopper. Further, when a circuit breaker is provided as the input opening means, the circuit breaker on the input side of the two-quadrant chopper is opened at the same time as the boost chopper is turned on.

This prevents excessive current from flowing into the boost chopper by cutting off short-circuit current flowing from the power supply side.

(Example) An embodiment of the present invention will be described below based on the drawings.

First, an embodiment of the first invention will be described with reference to the circuit diagram shown in FIG. Note that the DC-DC converter 23 shown in the figure is as follows:
Although it has the same configuration as the two-quadrant chopper explained in FIG. 6, in FIG.
5 is shown.

Note that since the present invention is a power feeding system using a two-quadrant chopper as the DC-DC converter 23, the following description will be given.

The DC-DC converter 23 will be described as a two-quadrant chopper 23.

The chopper output voltage detector 235 is connected to a control circuit 236, and the control circuit 236 is connected to an output voltage setting circuit 237 and a chopper frequency setting circuit 238. The control circuit 236 controls each setting circuit 237
and for step-down according to the setting signal from 238.

The boost choppers 231 and 232 are turned on and off to control each conductivity so as to maintain the output voltage of the two-quadrant chopper 23 at a specified value.

The configuration up to this point is similar to the circuit used in the conventional system, but the circuit shown in FIG. 1 to which the present invention is applied is further provided with a chopper frequency command circuit 239.

This chopper frequency command circuit 239 includes an output voltage setting circuit 237. It is connected to the chopper output voltage detector 235 and the chopper frequency setting circuit 238, and the setting circuit 23
7 and the detector 235, and outputs a chopper frequency command to the setting circuit 238.

That is, the chopper frequency command circuit 239 monitors the output voltage of the two-quadrant chopper 23, and when the output voltage exceeds the specified voltage vd, it outputs a reduced chopper frequency command signal to the chopper frequency setting circuit 238, and the chopper The frequency setting circuit 238 outputs an output frequency signal according to the command signal to the control circuit 236.

Next, the operation of the chopper frequency command circuit 239 will be explained with reference to the characteristic diagram shown in FIG. Here, when the chopper output voltage is around the specified value Vd, the chopper frequency is f, and when the load decreases and the chopper output voltage exceeds vd and reaches Vz, the chopper frequency is lowered from f to fi. When the load further decreases and the voltage rises to v2, the chopper frequency is further lowered to f2.

By performing such an operation, a high overhead line voltage of about 1500V is reduced to 400V by the second quadrant tip collar 23.
The voltage can be stepped down to the DC voltage corresponding to the distribution network, and the output voltage of the two-quadrant chopper 23 will not become an overvoltage. Therefore, the VVVF inverter, CV
Inverter such as CF inverter (271 in Figure 5)
, 371) and auxiliary power supply equipment (see 28, 38.48)
There is no need to design pressures that exceed the specified values (reference), and it is possible to make these devices and bases smaller and lighter, and it is possible to reduce the cost of IT construction.

Next, an embodiment of the second invention will be described with reference to a circuit diagram of the third yA.

Among the circuit components shown in the figure, the same elements as those in FIGS. 1 and 5 are given the same reference numerals. In this embodiment, the overvoltage detector 241 that detects the overvoltage of the output side voltage of the two-quadrant chopper 23 is connected to the capacitor 234.
are provided at both ends. The two output terminals of this detector 241 are connected to the step-down chopper 231. Boosting chopper 23
Gate circuits 242 and 24 that turn on and off 2, respectively.
3, and these gate circuits 242, 24
3 is connected to a control circuit 236'.

In normal operation, each gate circuit 242, 243 is driven by the control circuit 236', the gate circuit 242 operates the step-down chopper 231 when the step-down chopper is operating, and the gate circuit 243 operates the step-up chopper 232 when the step-up chopper is operating. make it work. In addition, when the overvoltage detector 241 detects that the output side voltage of the two-quadrant chopper 23 exceeds a specified value, the boost chopper 232 is forcibly turned on by one detection signal from the overvoltage detector 241. and the step-down chopper 231 is forcibly turned off by the other detection signal.

In addition, the input filter 22. An input opening means (fuse 244 in FIG. 3) consisting of a fuse, a circuit breaker, etc. is provided between the step-down choppers 231. This fuse 244 operates when the step-up chopper 232 is forcibly turned on in the event of a short-circuit failure of the step-down chopper 231.
In order to prevent excessive discharge current of the capacitor of the input filter 22 from flowing through the boost chopper 232,
It is fused to effectively cut off the discharge current.

FIG. 4 shows the step-down chopper 2 in the circuit shown in FIG.
The voltage of capacitor 234 when 31 is short-circuited,
Detection signal of overvoltage detector 241, output signal of gate circuit 243, current of boost chopper 232 and fuse 24
FIG. 4 is an operation waveform diagram showing how the current changes in No. 4;

First, when the step-down chopper 231 has a short-circuit failure at time T0, the high voltage on the input side of the two-quadrant chopper 23 is applied to the output side (low voltage side) via the step-down chopper 231 that has the short-circuit failure. Then, the terminal voltage of the output side capacitor 234 increases from the normal value Vd. When this low voltage side voltage reaches the specified overvoltage value Vdp (time T), the detector 241 detects the overvoltage and sends the detection signal to the gate circuit 24.
Output to 3. The gate circuit 243 is a boost chopper 2
32 and turns on the boost chopper 232 (time T2), after this.

Since the voltage across the boosting chopper 232 becomes approximately zero, the terminal voltage of the capacitor 234 decreases.

At this time, the filter capacitor of the input filter 22 is
Step-down chopper 231. Since it is short-circuited via the boosting chopper 232, the short-circuit current of the filter capacitor flows through the fuse 244.

This short circuit current causes the fuse 244 to open at time T.
is fused, and the short circuit current is cut off. In the waveform showing the voltage of the capacitor 234 in FIG. 4, the dotted curve shows the voltage change when the step-up chopper 232 is not turned on when the step-down chopper 231 is short-circuited.

Note that in the embodiments of each of the inventions described above, the RCGTO is used as the switching element constituting the two-quadrant chopper 23, but other types of elements such as transistors may be used as long as they are semiconductor switching elements.

(Effects of the Invention) As described above, according to the first invention, when the output side voltage of the chopper increases above a specified value especially when the two-quadrant chopper is under a light load, the chopping frequency is reduced. The output voltage of the two-quadrant chopper never becomes an overvoltage. As a result, the input voltage of various devices connected to the output side of the chopper will not become overvoltage, and there is no risk of situations such as loss of control or failure of these devices, and various devices are designed to withstand the specified voltage. Insulation is easy, and it is possible to achieve reductions in size, weight, and cost.

According to the second invention, an overvoltage on the output side of the two-quadrant chopper is detected, and when the overvoltage occurs, the step-up chopper is turned on to short-circuit the output side and open the input side. This also has the advantage that there is no risk of overvoltage having an adverse effect on various devices on the output side of the chopper. Further, when a short-circuit failure occurs in the step-down chopper, the short-circuit current of the step-up chopper can be limited by a fuse or the like, so that overcurrent protection of the chopper can be performed reliably and economically.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a two-quadrant chopper and its control system for explaining an embodiment of the first invention. Fig. 2 is a characteristic diagram showing the relationship between the chopper output voltage and chopper frequency in the circuit diagram of Fig. 1, and Fig. 3 shows a two-quadrant chopper and its control system for explaining an embodiment of the second invention. FIG. 4 is a waveform diagram for explaining the operation of each part in the circuit diagram of FIG. 3, FIG. 5 is a configuration diagram showing a power supply system for a DC electric vehicle, and FIG. 6 explains a conventional technology. 7 is a circuit diagram showing an example of a power conversion device for driving a motor used in FIG. 5, and FIG. 8 is a configuration showing an example of an auxiliary power supply device used in FIG. 5. FIG. 9 is an explanatory diagram of the operation of the two-quadrant chopper shown in FIG. 6. 235...Chopper output voltage detector 236, 236'...Control circuit 237...Output voltage setting circuit 238...Chopper frequency setting circuit 239...Chopper frequency command circuit 241...Overvoltage detector 242 ,243...
Gate circuit 244...fuse

Claims (2)

[Claims] (1) A two-quadrant chopper mounted on a DC electric car is operated at a constant chopping frequency to convert the contact line voltage from DC to DC to step down the voltage, change the conductivity of the output pulse of the two-quadrant chopper, and In a DC electric vehicle power supply system that supplies DC power while controlling the output voltage of a two-quadrant chopper to maintain it at a specified value, when the output voltage of the two-quadrant chopper exceeds the specified value, the chopping frequency is reduced. A power supply method for a DC electric vehicle, characterized in that the output voltage is lowered to the specified value or less by (2) A two-quadrant chopper mounted on a DC electric car is operated at a constant chopping frequency to convert the contact line voltage from DC to DC and step down, and the conductivity of the output pulse of the two-quadrant chopper is changed, In a power supply system for a DC electric vehicle that supplies DC power while controlling the output voltage of a two-quadrant chopper to maintain it at a specified value, the output side voltage is detected by a detector provided on the output side of the two-quadrant chopper; When the output side voltage exceeds a specified overvoltage value, the step-up semiconductor switching element constituting the two-quadrant chopper is turned on to short-circuit the output side, and the input opening means provided on the input side of the two-quadrant chopper A power supply system for a DC electric vehicle, characterized in that a short circuit current flowing from an input side to the step-up semiconductor switching element is cut off.