JPH02211003A - Main circuit system of ac electric vehicle driven by ac motor - Google Patents

Abstract

PURPOSE:To contrive to make the performance of a DC-AC converter higher by using a GTO thyristor as the switching element of a nonmultiple AC-DC converter and a transistor as the switching element of the DC-AC converter and by increasing the breakdown strength of the GTO thyristor 1.3 times or more than that of the transistor. CONSTITUTION:In a nonmultiple PWM control-type AC-DC converter 4, a high- frequency GTO thyristor is adopted as a switching element so that a ripple generated in a supply current is small. Also, an inverter using a transistor as a switching element is adopted in a DC-AC converter 6 so that a PWM control signal can be made into a high frequency. Further, even if a surge voltage such as direct lightning is generated in an electric overhead line 1, the surge voltage does not bring about the destruction of the switching elements because the breakdown strength of the GTO thyristor is increased 1.3 times or more than that of the transistor. Thus, it is possible to make the performance of a DC-AC converter 6 higher.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention provides a method for converting AC power from overhead contact lines to PW via a transformer.
Regarding an AC electric vehicle main circuit system that converts into DC power by an M-controlled AC-DC converter, and converts this DC power into AC power by a PWM-controlled DC converter to drive a vehicle drive AC motor, it is particularly suitable for power supplies. The present invention relates to an AC motor-driven AC electric vehicle main circuit system that can reduce harmonics to the side and reduce the cost of the device.

(Prior art) In a power conversion system (hereinafter referred to as "r main circuit system") that uses an AC motor to drive an AC electric car that is operated by receiving AC power from a contact line, the first-order system is used. The electric motor is driven by this method. That is, the AC power supplied from the overhead contact line is first converted to DC power by an AC-DC converter, and then this DC power is converted back to VVVF (variable voltage variable frequency) AC power by the DC-AC converter, and then induced. Drives the electric motor (IM). A voltage source inverter is generally used as the DC-AC converter.

In the case of such a main circuit system, the AC-DC converter must be able to operate in two quadrants, have a good power factor as seen from the overhead contact line, and have few harmonics flowing through the overhead contact line. It is said that

Figure 3 shows a conventionally known main circuit system.
Tram line 1, pantograph 2. Transformer 13° AC-DC converter group 14, smoothing capacitor 15. Inverter 16. It is composed of a group of electric motors 17. Here, the AC-DC converter group 14 is configured by multiple-connecting AC-DC converters 14a to 14d in parallel, and the motor group 17 is constituted by induction motors 17a to 14d.
17d.

In an actual AC electric vehicle, the conversion capacity of the main circuit system must be increased, so the converter group 14. The switching element used in the inverter 16 is a GTO thyristor. Since the switching frequency of this GTO thyristor is several hundred or more, the ripple current is also relatively large.Therefore, in order to further reduce the distortion of the current waveform on the primary side of the transformer 13 due to this ripple, the secondary winding of the transformer 13 is A plurality of lines (four in FIG. 3) are provided. Then, the DC side of each secondary winding is connected in parallel in multiple ways and connected to one inverter 16.

In the above main circuit system, the inverter 16 generally has a PW
It is an M control type, and the voltage of the DC intermediate circuit (the voltage between the terminals of the smoothing capacitor 15) is almost constant. As the AC-DC converters 14a to 14d, PWM control type converters are generally used when it is necessary to reduce harmonics of the overhead contact line 1, change the current waveform to a sine wave, and improve the power factor.

Figure 4 shows contact line voltage and alternating current during power travel and regeneration.
It is a waveform diagram showing the alternating current and overhead line current of the - converter among the DC converters 14a" and 14d. Each converter 14
Since the control signals a to 14d are of the PWM control type in which the control signal is a sine wave, the current waveform of the power supply is a sine wave with a current ripple due to PWM control superimposed. As described above, in the main circuit system that employs PWM control, the current phase can be controlled freely, so it is also possible to control the power factor to 1.0 during both traveling and regeneration, as shown in the figure.

FIG. 5 is a diagram showing a power conversion system frequently used in the general industrial field, which corresponds to the main circuit system of FIG. 3. Although the electric power supply system was single-phase in the case of the electric car shown in FIG. 3, it is a three-phase power distribution system 21 in FIG.

As this electrodynamic system 21, a 200V system or a 400V system is often used. This system includes an AC-DC converter 22, a smoothing capacitor 23. It is composed of an inverter 24 and an induction motor 25.

In a system connected to a 200V or 400V power distribution system, transistor type ones are generally used as the AC-DC converter 22 for power and the variable speed inverter 24 of the induction motor 25, as shown in the figure. ing. This is because: ■ The capacity of the induction motor 25 is several hundred kilowatts or less; ■ Even considering the surge voltage from the distribution system 21, the switching element breakdown voltage of the AC-DC converter @ 22 is 120 KW or less.
0 V is sufficient; ■ Due to the influence of harmonics on the power distribution system 21, the switching frequency of each element of the AC-DC converter 22 must be IKHz or higher; ■ Transistor-type switching elements This is due to reasons such as low price. In the case of the transistor type, the current waveform on the power distribution system 21 side has a high power factor and less waveform distortion, as in the case of FIG.

By the way, in the above-mentioned industrial power conversion system, there is no need to consider direct lightning strikes in the distribution system 21 for the AC-DC converter 22, and relatively small surge abnormalities such as switching surges are considered as abnormal voltages occurring in the system. Therefore, even if the power conversion system is connected to a 440 V power distribution system, the element withstand voltage of the AC-DC converter 22 on the power supply side is about 1200 V.
It is considered that the ratio (device breakdown voltage)/(effective value of AC voltage) should be about 2.7.

On the other hand, the withstand voltage of switching elements of AC electric vehicles is considered as follows.

The train I/IA1 shown in Figure 3 has a distance of several kilometers or tens of kilometers.
Since they are often installed in suburban areas, direct lightning surges must also be considered. in this case,
(Lightning surge voltage)/(AC voltage effective value) is approximately 3.6, so the element withstand voltage must also be adjusted to match this value. That is, the element withstand voltage of the power supply side AC-DC converter 14 is 3.6/2.7 of the motor side conversion WI (inverter) 16.
It needs to be 1.3 times (3 times) higher. Therefore,
GTO thyristors are used as the switching elements of the AC-DC converters 14a to 14d in FIG. 3.

(Problems to be Solved by the Invention) (1) In an AC electric vehicle, a signal current is passed through the track circuit of the rail 8 to perform various train controls. In Shinkansen trains and the like, this signal frequency ranges from around the commercial frequency to about 4 KHz. As for the switching frequency, the PWM carrier frequency must be at least 1/2 of the allowable harmonic frequency on the power supply side.

For this reason, when using a PWM control type AC-DC converter 14 on the power supply side, the equivalent interference current due to high frequency current is kept below the allowable value, and the harmonic current due to the carrier frequency of PWM control is However, current high-capacity GTO thyristors have a permissible switching frequency of 5
Therefore, in order to reduce the equivalent interference current and harmonic current, a plurality of AC-DC converters 14a to 14d are installed to increase the equivalent carrier frequency as seen from the power supply side.
P of the control device of each converter 14a to 14d by multiple-connecting
It is necessary to provide a phase difference to the WM carrier signal. For this reason, the conventional main circuit system had the disadvantage of increased weight.

(2) Also, in the DC-AC converter on the induction motor side, there is no need to consider surges from the AC power supply side because they are absorbed by the smoothing capacitor 15. Therefore, the working voltage and element withstand voltage are the same as those of the DC-AC converter. Determined by operating voltage.

For example, in the case of the inverter 24 shown in FIG. 5, which is made up of industrial transistors, the DC intermediate circuit voltage is 60
When the voltage is 0V to 700V and the effective value of the AC voltage is 440V, it is sufficient that the transistor has a breakdown voltage of 1200V. In this case, (device breakdown voltage) to AC voltage effective value) is 2.7.

However, as mentioned above, the transistor type converter
Lower cost than O-thyristor type converter.

Despite being small and lightweight, there is a limit to the voltage that can be used (converted to AC voltage) (up to 1/2.7 times the element withstand voltage even when surge voltage is taken into account), and the surge voltage is used by the converter. It cannot be used as a converter on the power supply side, which applies up to 3.6 times the voltage. Therefore, conventionally, as shown in FIG. cannot use the GTO thyristor, which is expensive.
The manufacturing cost of the main circuit system as a whole is high.

(3) In this way, in the case of AC motor-driven AC electric vehicle main circuit systems, in order to put them into practical use, it is important to reduce the cost as well as the size of the equipment. In order to reduce harmonics of the power supply current, a major challenge for devices is to increase the allowable switching frequency as much as possible.

The present invention was proposed in order to solve the above problems, and it is possible to reduce the cost and weight of the device, reduce harmonics of the power supply current, and improve the performance of the converter on the motor side. The purpose of the present invention is to provide an AC motor-driven AC electric vehicle main circuit system that can achieve the following.

(Means for Solving the Problems) The inventors believe that the cause of the performance deterioration of the inverter is that a GTO thyristor type inverter is used as the power converter on the motor side, and that the increase in size and price of the device One of the reasons is that the converters on the power supply side are multiplexed.Furthermore, since the transistor element has a three-layer structure, the economical breakdown voltage is about 1200V, and if the breakdown voltage is raised higher than this, the element Although the price will increase dramatically, we focused on the fact that since the GTO thyristor has a four-layer structure, it is easy to increase the breakdown voltage to around 4500V.

In order to solve these inconveniences, ① GTO thyristors are used as the switching elements of the power supply side converter as before, but transistors are used as the switching elements of the motor side converter to configure the main circuit system. ■Also. Obtained the knowledge that by increasing the switching frequency of the power supply side converter, the PWM carrier frequency can be made at least 172 times higher than the allowable harmonic frequency of the power supply side, and by increasing the carrier frequency, the power supply side converter can be made non-multiplexed. Ta.

That is, the present invention takes AC power into an electric car via an overhead contact line, converts this AC power into DC power by a PWM controlled AC-DC converter via a transformer, and converts this DC power into a DC intermediate circuit. In an AC motor-driven AC electric vehicle main circuit system in which the AC power is converted into AC power by a PWM control type DC-AC converter and the AC motor is driven by this AC power, the switching element of the AC-DC converter is replaced with a GTO thyristor. In addition, the switching element of the DC-AC converter is a transistor, the withstand voltage of the GTO thyristor is 1.3 times or more the withstand voltage of the transistor, and the AC-DC converter is non-multiplexed. do.

(Function) After passing through a transformer, the AC power taken into the electric car via the overhead contact line is converted into DC power by a non-multiplexed PWM controlled AC-DC converter, and then converted into DC power. After being converted into AC power by a converter, it is supplied to the AC motor for driving the train.

The above AC-DC converter employs a high frequency GTO thyristor as a switching element.

Even if it is not multiplexed, the ripple generated in the power supply current will be as small as in the case where a conventional multiplex PWM type AC-DC converter is employed. Further, since the DC-AC converter employs an inverter using a transistor as a switching element, the PWM control signal can be of high frequency. here.

When one electric motor is provided for each DC-AC converter (inverter), the load on the inverter is reduced.

Further, even if a surge voltage such as a direct lightning strike occurs on the overhead contact line, the withstand voltage of the GTO thyristor is set to be 1.3 times or more the withstand voltage of the transistor, so this will not lead to destruction of the switching element.

(Embodiment) FIG. 1 shows an embodiment of the present invention. In the figure, AC power taken into an electric car from an overhead contact line 1 via a pantograph 2 is stepped down by a transformer 3. The secondary winding of this transformer 3 is connected to a single-phase AC-DC converter 4.

The switching element constituting this AC-DC converter 4 is a GTO thyristor with high withstand voltage, and is shown as a reverse conduction type in the figure. In addition, the GTO thyristor used in the AC-DC converter 4 should have a withstand voltage 1.3 times or more that of the transistors constituting the DC-AC converters 68 to 6d, which will be described later, in consideration of the surge voltage from the overhead contact line 1. used.

A DC-AC converter group 6 is connected to the DC side of the AC-DC converter 4 via a smoothing capacitor 5 . This DC-AC converter group 6 includes DC-AC converters 6a to 6d.
It is configured by connecting them in parallel.

Transistors are used as switching elements of the DC-AC converters 68-6d, and one induction motor (IM) 7a-7 is provided on the load side of each DC-AC converter 6a-6d.
7d is connected.

Note that the AC-DC converter 4. DC-AC converter 68-6
d is the same as the conventional <PWM control type.

The operation of the above embodiment will be explained below.

First, when going to Ka, from tram line 1 to pantograph 2
An AC sinusoidal voltage is applied to the primary winding of the transformer 3 through the transformer 3, causing a sinusoidal current to flow, and an AC voltage is induced in the secondary winding of the transformer 3. The AC-DC converter 4 converts this AC power (
AC voltage) is PWM controlled, converted to DC power, and output. At this time, a pull occurs in the sine wave current on the AC power supply side.

Since the switching frequency of each GTO thyristor of the AC-DC converter 4 is 2 KHz or more, the ripple is slight and does not affect the signal flowing through the track circuit of the rail 8 such as a Shinkansen train.

On the other hand, the DC voltage from the AC-DC converter 4 is smoothed by the capacitor 5 and input to the DC-AC converters 68 to 6d, and each of these converters 68 to 6d is connected to the induction motor 7a.
~7d is driven. Here, DC-AC converters 68 to 6d
are PWM-controlled in the same way as the conventional DC-AC converter 16 shown in FIG. It is possible to perform high-speed switching compared to a conventional DC-AC converter.

Thereby, the frequency of the PWM carrier can be made higher than in the past, and the performance of the DC-AC converters 68 to 6d can be improved.

During regeneration, the three-phase AC power regenerated from the induction motors 7a-7d is converted into DC power by the AC-DC converters 6a-6d, which are the DC-AC converters, and these DC powers are converted into DC power. The DC-AC converter 4, which is an AC-DC converter, performs a reverse conversion operation to convert into single-phase AC. Since PWM control is performed even during this inverse conversion operation, the ripples generated in the sine wave current on the power supply side are slight, and it is possible to keep the harmonics of the overhead contact line current within a permissible value.

Fig. 2 is a waveform diagram showing the overhead line voltage and the alternating current (same as the overhead line current) of the AC-DC converter 4 during power running and regeneration, and the harmonic current of the overhead line current is reduced. The situation is shown.

Although one induction motor 7 is shown here as the load for each of the DC-AC converters 68-6d, the induction motor can be used as long as it is within the current capacity of the transistors of the DC-AC converters 6a-6d. Multiple units may be connected.

Further, in the above embodiment, one AC-DC converter 4 is provided as an AC-DC converter, and this drives the DC-AC converters 6a to 6d. The corresponding number of AC-DC converters (four in the case of Figure 1) are connected in parallel to the common secondary winding of the transformer 3, and each smoothing capacitor is connected to each AC-DC converter. The induction motors 7a to 7d may be driven by connecting to the DC-AC converters 68 to 6d via the DC/AC converters 68 to 6d.

Further, in the above embodiment, the AC-DC converter 4 is of a reverse conduction type, but it may be of an irreversible conduction type, and a polarity changeover switch may be provided in the DC intermediate circuit.

(Effects of the Invention) In the present invention, a high frequency GTO thyristor is used as a switching element of a PWM controlled AC-DC converter on the overhead contact line side.
A transistor is used as the switching element of the PWM control DC converter on the motor side, and the breakdown voltage of the GTO thyristor is set to be 1.3 times or more the breakdown voltage of the transistor.

1) It is possible to use a transistor-type DC-AC converter that is lower in price than the GTO thyristor type, which reduces the cost of the entire main circuit system. 2) It is possible to use a transistor-type DC-AC converter that is lower in price than the GTO thyristor type, reducing the cost of the entire main circuit system. 2) Compared to the GTO thyristor as a DC-AC converter on the motor side 3) AC-DC conversion on the contact line side Similar to the conventional main circuit system in which both the DC-AC converter on the power line and the motor side are of the GTO thyristor type, this system has the advantage that harmful harmonics are not generated on the overhead contact line.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing one embodiment of the present invention, and Fig. 2 is a circuit diagram showing an embodiment of the present invention.
The overhead line voltage and overhead line current (AC-
Figure 3 is a circuit diagram showing a conventional example, and Figure 4 shows the overhead line voltage and current in the circuit of Figure 3 and the AC current of each AC-DC converter. The waveform diagram shown in Figure 5 is 313! 1 is a circuit diagram showing a general industrial power conversion system compatible with the main circuit of FIG. DESCRIPTION OF SYMBOLS 1... Tramway line, 2... Pantograph, 3... Transformer, 4... AC-DC converter, 5... Smoothing capacitor, 6... DC-AC converter group, 6a~ 6a...DC-AC converter, 78-7d...Induction motor

Claims (1)

[Scope of Claims] AC power is taken into an electric car via an overhead contact line, this AC power is converted to DC power by a PWM controlled AC-DC converter via a transformer, and this DC power is transferred to a DC intermediate circuit. In an AC motor drive AC electric vehicle main circuit system in which the AC power is converted into AC power by a PWM controlled DC-AC converter and the AC motor is driven by the AC motor, the switching element of the AC-DC converter is replaced with a GTO thyristor. In addition, the switching element of the DC-AC converter is a transistor, the withstand voltage of the GTO thyristor is 1.3 times or more the withstand voltage of the transistor, and the AC-DC converter is non-multiplexed. An AC electric vehicle main circuit system driven by an AC motor.