JPH03261307A - Control method of inverter for driving electric car and inverter drive electric car system - Google Patents

Abstract

PURPOSE:To realize reduction of size, weight and cost by connecting filter capacitors and chopper circuits in parallel with transistor inverters, having DC sides connected in series, for every plurality of AC motors in a single electric car. CONSTITUTION:A DC high voltage, e.g. 1,500V, collected from a stringing 2 through a pantograph 3 and a filter reactor 4, is applied onto transistor inverters Tr In 10-40 having DC sides connected in series, and the DC voltage returns through a wheel 7 to a rail 8. Each Tr In inverts DC voltage into VVVF three- phase AC voltages for individually driving four induction motors 11-41 in a single electric car. Filter capacitors 12-42, chopper control circuits 15-45, and series circuits of choppers 13-43 and resistors 14-44 are connected in parallel with respective Tr In 10-40. Consequently, imbalance of load for each Tr In is prevented resulting in the reduction of overall size, overall weight and cost.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to an electric motor that uses a voltage source inverter, which uses transistors as a component and converts direct current to alternating current through pulse width modulation control, as a power source for a motor for driving a vehicle. This article focuses on a method of controlling a car drive inverter and an inverter-driven electric car system.

[Conventional technology]

FIG. 5 is a circuit diagram showing a conventional example of the main circuit configuration of a DC electric vehicle running with an induction motor.

In this FIG.
After passing through a filter capacitor 5 and a GTO inverter 6, which includes a gate turn-off thyristor, it is converted into AC power of a desired voltage and frequency, and then discharged to a rail 8 via wheels 7.

A typical electric car consists of two sets of bogies each having two axles, and each axle is equipped with a separate driving electric motor. Therefore, the first truck 91 has an induction electric motor 1 for driving.
111 and 21, and the induction motor 3 is mounted on the second truck 92.
1 and 41 are installed, and these four induction motors are driven by a GTO inverter 6 of 1&lI.

In order to drive the electric vehicle at a desired speed, the GTO inverter 6 needs to output alternating current with variable voltage and variable frequency. Also, when the electric vehicle decelerates, the electric motor operates as a generator, regenerating energy to the power source. So this G
The TO inverter 6 is able to meet the above requirements by controlling pulse width modulation.

FIG. 6 is a circuit diagram showing an example of a circuit configuration for one phase of the GTO inverter used in the conventional example shown in FIG.

In this FIG. 6, two GTO thyristors 62 and 6
3 in series, each GTO thyristor 62
．． Freewheel diodes 64 and 65 are connected in antiparallel to 63. Furthermore, these GTO thyristors 62.6
An arm reactor 60 is connected in series to the series circuit of No. 3 and connected between the positive pole P and the negative pole N, and this arm reactor 60 changes the current change d when each GTO thyristor 62, 63 turns on, /dt. This arm reactor 60 includes a circulation circuit 6 for processing electromagnetic energy accumulated therein.
1 in parallel, and each GTO thyristor 62.63
Snubber circuits 66 and 67 are connected in parallel. Furthermore, 68
and 69 are gate drive circuits of the GTo thyristors 62 and 63.

51st! The GTO inverter 6 described in 1 requires a three-phase circuit with the configuration shown in FIG. , since the weight is also large,
It was difficult to store it in the limited space of an electric car.

FIG. 7 is a circuit diagram showing a general example of an inverter using transistors as constituent elements.

The transistor inverter 70 shown in FIG.
With the phase 70R, the second phase 70S, and the third phase 70T,
Direct current is converted into three-phase alternating current with variable voltage and variable frequency. Looking at the configuration of the first phase 70R, two transistors 71 and 72 are connected in series, and freewheeling diodes 73 and 74 are connected to each other. Connect in antiparallel,
Furthermore, snubber capacitors 75 and 76 are connected to each transistor 7.
1.72 is connected in parallel.

Note that 77 and 78 are base drive circuits for each transistor 71 and 72, and 5 is a filter capacitor.

The CTO inverter shown in FIG.
A comparison with the transistor inverter 70 shown in the figure shows that the circuit configuration of the latter is much simpler.

[Problem to be solved by the invention]

By the way, the catenary voltage of DC electric cars is generally nominally 1500
V is the main character. On the other hand, the pressure resistance of GTO Cyrisk is 450
0 V, therefore, the GTO inverter 6 can be used up to an input voltage of about 2000 V, so the DC current is 150 V.
It can be fully used for 0V electric cars.

On the other hand, the breakdown voltage of a normal transistor is 1200■,
Since the maximum voltage is 1400 V, the input voltage limit for a transistor inverter is 700 V.

Therefore, in order to use a transistor inverter, which has a simple circuit, a small number of parts, and is inexpensive, in a place where the overhead line voltage is 1500 V, it is conceivable to connect a plurality of transistor inverters in series on their DC sides. That is, when one electric vehicle has four electric motors for running, the DC sides of transistor inverters 411 may be connected in series, and the electric motors and transistor inverters may be coupled one-to-one.

However, if a particular wheel of a running electric vehicle spins during forward driving or slides during forward driving, causing load fluctuations in the transistor inverter that drives the wheel, the series connection There is a risk that the share of the DC side voltage of the inverter will vary greatly and an overvoltage exceeding the rated value will be applied.

In addition, in an electric car that runs by connecting the DC sides of transistor inverters that output variable voltage and variable frequency AC using pulse width modulation control in series, and driving a separate induction motor for each inverter, the output frequency of each inverter is They are almost the same.

FIG. 8 is a graph showing the first characteristic of the pulse width modulation controlled inverter, with the horizontal axis representing the frequency and the vertical axis representing the modulation rate.

In this Figure 8, when the inverter input voltage is at the specified value, the frequency and modulation rate change according to the relationship of straight line A, so
When the frequency of the inverter is F, the modulation rate is α. Here, when the inverter input voltage falls below the specified value, the characteristic changes to the one shown by straight line B, so the modulation rate increases to α1 when the inverter frequency is maintained at F. On the contrary, if the input voltage rises above the specified value, the characteristic will be as shown by straight line C, so the modulation rate at frequency F0 will be α8
This will result in a decrease to

FIG. 9 is a graph showing the second characteristic of the pulse width modulation controlled inverter, with the horizontal axis representing the frequency and the vertical axis representing the inverter input current.

Similarly to the above-mentioned Fig. 8, this figure 9 also has a straight line characteristic when the inverter input voltage is at the specified value, and when the input voltage drops below the specified value, the characteristic is a straight line E, and when the input voltage falls below the specified value, the characteristic is straight line. When rising, it has the characteristics of straight line G. Therefore, if an attempt is made to maintain the inverter frequency For,i, the input current increases to Io when the input voltage decreases, and decreases to Io when the input voltage increases.

FIG. 10 is an explanatory diagram of the operation of a conventional circuit in which two sets of pulse width modulation control inverters are connected in series on the DC side.

In FIG. 10, the DC sides of two sets of transistor inverters 10 and 20 that output alternating current of variable voltage and variable frequency through pulse width modulation control are connected in series, and each transistor inverter 10 and 20 is connected to an induction motor 11 separately. 21 is connected. Note that 4 is a filter reactor, 12 and 2
2 is a filter capacitor.

(One electric car is normally equipped with four electric motors, but to simplify the explanation, two are shown in Figure 1O.) The loads of induction motors 11 and 21 are the same electric motors. Since it is a car, the output frequencies of both transistor inverters 10 and 20 are almost the same value, which is assumed to be F, and at this time, the input current from the DC power supply 9 is F. It is.

At this point, due to reasons such as sudden changes in the voltage of the DC power supply 9,
Assuming that the input voltage of the transistor inverter lO becomes lower than the input voltage of the inverter 20, the modulation rate of the transistor inverter lO is α from the characteristics shown in FIGS. 8 and 9 described above. →Input current to α1 is I4゜→■1
+ respectively, while the modulation rate of the transistor inverter 20 is α.

→ α mushroom, the input current decreases to I− → 14M, respectively.

However, both transistor inverter 1 connected in series
The input currents of 0 and 20 are both 1. . was flowing, so
Transistor inverter 10 has input currents 141 and I. The deficit Δ■, which is the difference between the
The filter capacitor 22 is charged with the surplus ΔIt, which is the difference between t and 1°.

As a result, while the input voltage of the transistor inverter 100 becomes lower and lower, the input voltage of the transistor inverter 20 becomes higher and higher (which makes it impossible to perform normal power conversion operation).

FIG. 11 is a layout diagram showing a conventional example of a GTO inverter-driven electric vehicle system based on the conventional example circuit shown in FIG.

As shown in FIG. 11, the vehicle body 90 has a first bogie 91.
and a second truck 92, and each truck is equipped with two induction motors 11, 21, 31, 41 in total. Filter reactor 4 and filter capacitor 5
The GTO inverter 6 is installed under the floor of the car body 90 between the bogies 91 and 92, takes in DC power from an input terminal 100, converts it to AC power in the GTO inverter 6, and then connects the inverter output line 102 to each induction motor. It sends AC power to.

As already mentioned, the GTO inverter 6 is large and heavy, making it difficult to store it under the floor of an electric car.Furthermore, since the body of an electric car is long, the inverter output line 102 is also long. Become. - Generally, a voltage containing harmonics is applied to the wiring from the inverter to the induction motor, and a current containing harmonics flows, so a large amount of electrical noise is generated due to the long length of the inverter output line 102. It also has some drawbacks.

FIG. 12 is a layout diagram showing another conventional example of an inverter-driven electric vehicle system in which the DC sides of four transistor inverters are connected in series like the conventional circuit shown in FIG. 1O.

Similarly to FIG. 11, the car body 90 has a first truck 91 and a second truck 92, each of which is equipped with a total of four induction motors 11, 21, 31, and 41, two each. are doing. Under the floor of this vehicle body 90, between both bogies, there are four inverter boxes 81, 82, 83, 8 that house one set of transistor inverters and one filter capacitor.
4, and the corresponding induction motors are wired with inverter output lines 102.

Note that 4 is a filter reactor and 100 is an input terminal.

In the case of the conventional example shown in FIG. 12, the output voltage of each transistor inverter is 1/4 of that of the GTO inverter 6 shown in FIG.
This is four times that of inverter 6.

Therefore, the inverter output wires 102 from the inverter box to each induction motor must have a cross-sectional area commensurate with this current, which has the disadvantage that the wires are expensive and heavy. Furthermore, as in FIG. 11, since the dimensions of the inverter output line 102 are increased, there is also the disadvantage that a large amount of electrical noise is generated.

Therefore, the purpose of this invention is to eliminate the unbalance of the input voltage when the DC sides of these transistors are connected in series and to apply transistor inverters that perform pulse width modulation control to electric vehicles. This aims to shorten the wiring length between the inverter and the induction motor and reduce noise generation.

[Means to solve the problem]

In order to achieve the above object, the control method and inverter-driven electric vehicle system of the present invention performs pulse width modulation control of a voltage source inverter configured with semiconductor switching elements to convert input direct current into alternating current with variable voltage and variable frequency. , a control method for an inverter device for driving an electric vehicle that operates an AC motor for running at variable speed, comprising: a plurality of voltage source inverters each equipped with a filter capacitor on the DC side using transistors as the semiconductor switching elements; The DC sides of the voltage source inverters are connected in series, a series circuit of a chopper and a resistor is separately connected in parallel to the filter capacitor, and the AC motor is separately connected to the AC side of these voltage source inverters, so that each voltage When the DC input voltage of the voltage-type inverter becomes equal to or higher than a predetermined value, the chipper belonging to this voltage-type inverter is operated, or the chipper that is common to each voltage-type inverter is operated. When the DC input voltage of the voltage source inverter exceeds a predetermined value, the chopper belonging to the voltage source inverter is operated, and the voltage source inverter operates the chopper belonging to the voltage source inverter. In an inverter-driven electric vehicle system configured such that the DC side of the AC motor for driving the wheels is connected in series, and the AC motor coupled to the wheels is separately connected to the AC side of the voltage source inverter, the AC motor supplies AC power to the AC motor for driving the wheels. A voltage source inverter is mounted on a cart with wheels or installed near this truck, and the outgoing conductor and return conductor that supply DC power to the voltage source inverter are as follows:
The arrangement shall be such that the distance between them is the minimum.

[Effect]

This invention configures a voltage source inverter that performs pulse width modulation control using low-cost transistors that have low withstand voltage but can simplify the circuit, and develops this inverter so that it can be applied to electric vehicles with high input DC voltage. The DC sides of transistor inverters are connected in series, and an induction motor for running is separately connected to each inverter. In this case, the input voltage of each inverter becomes unbalanced due to unbalanced load due to wheel slipping or skidding, or sudden change in power supply voltage, which causes the chopper connected in parallel to the DC input side of each inverter to operate. By correcting this, or by setting the modulation factor of each inverter to a common value, the unbalance of the input voltage can be prevented from increasing. Furthermore, by placing these transistor inverters under the floor as close to the induction motor as possible, the length of the wiring between the two can be shortened, reducing weight and suppressing noise. Further, in this case, on the inverter input side, by making the conductors of the forward and return paths as close as possible, noise generated from this input side is also suppressed.

〔Example〕

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

In this FIG. 1, DC power taken into the electric car from the overhead wire 2 via the pantograph 3 is transmitted to the filter reactor 4 and four sets of transistor inverters 10, 20, 30, whose flow sides are connected in series. The water is discharged to the rail 8 via the wheel 7 and the rail 8.

4 sets of transistor inverters 10.20.30.40
The configuration of is as already described in FIG. 7, and induction motors 11, 21, 31, and 41 for driving electric cars are separately connected to each, and these transistor inverters are as follows.
Each converts input DC power into AC power with a desired voltage and frequency using pulse width modulation control, and operates the induction motor at variable speed. In addition, on the DC input side of each transistor inverter 10.20°30, 40,
Filter capacitors 12°22, 32.42 are connected separately.

Transistor inverters with low withstand voltages are connected in series so that they can be applied to high-voltage circuits for electric cars, but when load fluctuations occur due to wheel slipping or skidding, the four sets of inverters are connected to the overhead line voltage. The voltage will not be shared equally, and there is a risk that an overvoltage exceeding the rated value will be applied.

Therefore, in the present invention, a current shunting circuit consisting of a switch 13, 23, 33, 43 made of a semiconductor switch element and a resistor 14, 24, 34, 44 separately connected in series with these is provided. , connected in parallel to each filter capacitor.

Now, while the four induction motors IL 21.31.41 are running with their loads appropriately shared, for example, the induction motor 11.
When the wheels connected to the motor idle, the load on the induction motor 11 becomes light, so the output current of the transistor inverter 10 decreases, and the input current also decreases.

However, since the other three inverters 20, 30, and 40 are operating with the same load as before, the input current corresponding to the load is flowing normally. As a result, a surplus is generated in the input current of the transistor inverter 10, which flows into the filter capacitor 12 and increases its voltage.

Therefore, when the chopper control circuit 15 detects the voltage rise of the filter capacitor 12, it sends an operation command to the chopper 13, and controls the excess current or the filter capacitor 12.
By flowing the charge through the resistor 14 and consuming it, voltage rise is suppressed.

It goes without saying that the chopper control circuit 15 controls the conduction rate of the chopper 14 in accordance with the degree of increase in voltage, and adjusts the current flowing through the resistor 14.

FIG. 2 is a slightly more detailed circuit diagram of the circuit according to the embodiment of the present invention shown in FIG. 1, and is illustrated in the case of two sets of transistor inverters.

In FIG. 2, the filter reactor 4, transistor inverters 10 and 20, induction motors 11 and 21, filter capacitors 12 and 22, choppers 13 and 23, resistors 14 and 24, and chopper control circuits 15 and 25 are as shown in FIG. The names, uses, and functions are the same as those described in , so a description of these will be omitted. Further, in FIG. 1, it is assumed that the DC power supplied by the overhead wire is replaced by the DC power supply 9.

The operation command circuit 50 provides the inverter control circuits 18 and 28 with operation command signals such as the rotational direction, torque, starting/stopping, acceleration/deceleration, and speed of the electric motor, and each inverter control circuit 1
8 and 28 control each transistor inverter 10 and 20 so that the current detection value input from the current detectors 16 and 26 and the speed detection value input from the speed detectors 17 and 27 match the aforementioned operation command signal. do.

If there is a difference in the input voltages of the transistor inverters 10 and 20 due to a change in the voltage 2 of the DC power supply 9, as already mentioned in the operation diagram of FIG. In the inverter, this difference in input voltage increases, so this is suppressed by operating choppers 13 and 23 provided on the input side of each transistor inverter. 14.24 will result in power loss. Therefore, in the case of electric vehicles, focusing on the fact that the frequencies output by each inverter are almost the same, by giving a common modulation rate signal to each inverter, it is possible to eliminate the unbalanced input voltage without using the chopper 13 or 23. This is an attempt to prevent the spread.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention.

Like FIG. 2 described above, this FIG. 3 is also described in the case of two sets of transistor inverters. In addition, the filter reactor 4, DC power supply 9, transistor inverters 10 and 20, induction motors 11 and 21, filter capacitors 12 and 22, choppers 13 and 23, resistors 14 and 24, and chopper control circuit 15 shown in FIG. 25, the names, uses, and functions of the current detectors 16 and 26, the speed detectors 17 and 27, and the operation command circuit 50 are already described in FIG.
Descriptions of these will be omitted.

In the present invention, in response to various command signals from the operation command circuit 50, the inverter control circuit 51 provides control signals to the transistor inverters 10 and 20.
At this time, the modulation rate signals given to both inverters 10 and 20 are assumed to have the same value. That is, a modulation rate signal at an operating point corresponding to the average value of the speeds of the two induction motors 11 and 21 detected by the speed detectors 17 and 27 is provided.

As a result, the amount of unbalance in the input voltages of both transistor inverters 10 and 20 remains at a value corresponding to the amount of load unbalance in each inverter, and does not increase further. Therefore, the input voltage due to normal load unbalance The imbalance of
It is not necessary to operate the chopper 13.23, however, in case of large load fluctuations due to wheels spinning or skidding, operating the chopper 13.23 prevents the inverter input voltage from rising abnormally. .

FIG. 4 is a layout diagram showing an embodiment of an inverter-driven electric vehicle system in which the circuit according to the embodiment of the present invention shown in FIG. 1 is mounted on an electric vehicle.

As described in FIGS. 11 and 12 above, the conductor that connects the voltage source transistor inverter that performs pulse width modulation control and the induction motor has a large cross-sectional area, so it is expensive and expensive.
Since the weight increases and noise is generated, it is necessary to shorten the length as much as possible.

Therefore, in the present invention, the transistor inverters 10 and 20 that supply AC power to the induction motors 11 and 21 mounted on the first truck 91 are housed in the first inverter box 93, and the transistor inverters 10 and 20 are placed as close to the first truck 91 as possible. (If possible, install it on this first truck) and connect it to the inverter output line 1.
02 dimensions should be shortened as much as possible. This first inverter box 93
In addition to transistor inverters 10 and 2'0, a first
Filter capacitors 12 and 22 and dust cap 1 shown in the figure
3 and 23 as well as the circuits that control them. The resistors 14 and 24 may be housed in the same box or placed separately.

In addition, induction motors 31 and 41 mounted on the second truck 92
A second inverter box 94 containing transistor inverters 30 and 40, filter capacitors 32 and 42, dustpans 33 and 43, and a control circuit thereof for supplying alternating current power to the second truck 92 is installed near the second truck 92, The length of the inverter output line 102 is shortened. Resistor 3444 may be housed in 94 or placed separately.

Furthermore, a filter reactor 4 is installed at an appropriate position, and DC power input from an input terminal 100 is connected to the filter reactor 4 and the first inverter box 9 via an inverter input line 101.
3 and the second inverter box 94, one line and the other of the inverter input lines 101 at this time are wired as close as possible to suppress the generation of electrical noise.

〔Effect of the invention〕

According to this invention, in a DC electric vehicle that uses an induction motor as a motor for driving a vehicle shaft, a transistor is used as a switching element of a voltage source inverter that supplies AC power of variable voltage and variable frequency to the induction motor under pulse width modulation control. By using this voltage source inverter, the number of components can be reduced, the circuit can be simplified, and the circuit can be made smaller and cheaper. However, the withstand voltage of the inverter is lower than the overhead line voltage of a DC electric train, so this transistor inverter is used. The DC side is connected in series, and the induction motor and inverter are connected in a one-to-one correspondence to compensate for the lack of withstand voltage.In addition, overvoltage of the inverter DC input voltage due to load fluctuations is connected to the inverter DC side. By suppressing the dust with a dust brim, it is possible to make the inverter for driving a DC electric vehicle smaller, lighter, and cheaper. Furthermore, in electric vehicles, by focusing on the fact that the output frequency of each inverter is almost the same, and by giving a common modulation rate signal to each inverter, it is possible to prevent the unbalance of the inverter input voltage from expanding due to slight voltage fluctuations or load fluctuations. As long as the input voltage does not become excessive, there is no need to operate the above-mentioned dust filter, which has the advantage of not causing power loss. In addition, when installing these multiple transistor inverters under the floor, the wiring between the transistor inverters and the induction motor driven by them should be arranged to be as short as possible, and the wiring on the input side of the transistor inverters should be arranged so that the outbound and return routes are the same. By getting as close as possible,
It is possible to suppress noise generation and reduce wiring weight and cost.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing the first embodiment of the present invention;
The figure is a slightly more detailed circuit diagram of the embodiment circuit of the present invention shown in Figure 1, Figure 3 is a circuit diagram of the second embodiment of the invention, and Figure 4 is the same as Figure 1. Layout 1 showing an embodiment of an inverter-driven electric car system when the circuit according to the present invention is mounted on an electric car, and Fig. 5 are circuits showing a conventional example of the main circuit configuration of a DC electric car running with an induction motor. Figure 6 is a circuit diagram showing an example of the circuit configuration for one phase of the GTO inverter used in the conventional example shown in Figure 5, and Figure 7 shows a general example of an inverter that uses transistors as components. Figure 8 is a graph showing the first characteristic of the pulse width modulation control inverter, Figure 9 is a graph showing the second characteristic of the pulse width modulation control inverter, and Figure 10 is the graph showing the pulse width modulation control inverter. An explanatory diagram of the operation of a conventional circuit in which the DC sides of inverters are connected in series, Figure 11 is a layout diagram showing a conventional example of an inverter-driven electric vehicle system based on the conventional circuit shown in Figure 5, and Figure 12 is Figure 10. FIG. 2 is a layout diagram showing another conventional example of an inverter-driven electric vehicle system in which the DC sides of four transistor inverters are connected in series like the conventional example circuit shown in FIG. 2... Overhead line, 3... Pantograph, 4... Filter reactor, 5, 12.22.32.42... Filter capacitor, 6... GTO inverter, 7...
・Wheel, 8...Rail, 9...DC power supply, 10.2
0.30.40.70...transistor inverter,
11.21.3L U...Induction motor, 13.23.
33.43... Chiritsuba, 14.24.34.44.
・・Resistance, 15.25.35.45 ・・Chiritsuba control circuit, 16° 26 ・・Current detector, IT, 27・・
・Speed detector, 18.28° 51... Inverter control circuit, 50... Operation command circuit, 60... Arm reactor, 61... Circulation circuit, 62.63... GTO
Thyristor, 64.65.73.74... Freewheel diode, 66, 67... Snubber [F, 68.
69... Gate drive circuit, 71.72... Transistor, 75.76... Snubber capacitor, 77, 7
8...Base in circuit, 81°82.83.84...
- Inverter box, 90... Vehicle body, 91... First truck, 92... Second truck, 93... First inverter box,
94...Second inverter box, 100...Input terminal,
101...Inverter input line, 102...Inverter output line. 4 filter soactor vine map one! 8 Figure 1A10 Figure

Claims (1)

[Scope of Claims] 1) Electric vehicle drive that converts input direct current into alternating current with variable voltage and variable frequency by pulse width modulation control of a voltage source inverter composed of semiconductor switching elements, and operates an alternating current motor for running at variable speed. In a control method for an inverter device for use in a motor vehicle, a plurality of voltage source inverters each having a filter capacitor on the DC side are configured using transistors as the semiconductor switching elements, and the DC sides of these voltage source inverters are connected in series, and a chopper and a chopper are connected in series. a series circuit with a resistor is separately connected in parallel to the filter capacitor, and the AC motor is separately connected to the AC side of these voltage source inverters;
An electric vehicle characterized in that each voltage source inverter is controlled by pulse width modulation separately, and when the DC input voltage of the voltage source inverter exceeds a predetermined value, the chopper belonging to the voltage source inverter is operated. A method of controlling a drive inverter device. 2) In a control method for an inverter device for driving an electric vehicle, which controls a voltage source inverter by pulse width modulation to convert input DC into AC with variable voltage and variable frequency, and operates an AC motor for driving at variable speed, a filter is installed on the DC side. The DC sides of a plurality of voltage source inverters each having a capacitor are connected in series, a series circuit of a chopper and a resistor is separately connected in parallel to the filter capacitor, and the AC motor is connected separately to the AC side of these voltage source inverters. A common modulation rate signal is given to each of the voltage source inverters to perform pulse width modulation control, and when the DC input voltage of the voltage source inverter exceeds a predetermined value, the voltage source inverters belonging to the voltage source inverter are connected to A method for controlling an inverter device for driving an electric vehicle, the method comprising operating a chopper. 3) In an inverter-driven electric vehicle system configured such that the DC sides of a plurality of voltage source inverters are connected in series and the AC motor coupled to the wheels is separately connected to the AC side of the voltage source inverter, the AC motor for driving the wheels The voltage-type inverter that supplies AC power to the voltage-type inverter is mounted on a truck equipped with wheels or installed near the truck, and the outgoing conductor and return conductor that supply DC power to the voltage-type inverter are An inverter-driven electric vehicle system characterized by being arranged with minimum intervals.