JPH02303302A - Power converter for ac electric vehicle and operating method thereof - Google Patents

Abstract

PURPOSE:To reduce loss considerably, when compared with PWM control, by employing a thyristor rectifier in a source side converter constituting a power converter to be mounted on an AC electric vehicle. CONSTITUTION:Power to be fed from a trolley wire 1 through a pantograph 2 is rectified through a transformer 5 and a thyristor rectifier 6, then the rectified power is fed through a filter reactor 7 and a switch 8 to a transistor inverter 10 and the alternated power is fed to an induction motor 11. Since the thyristor rectifier 6 performs switching with commercial frequency, loss is reduced when compared with a PWM inverter. Furthermore, loss in the transistor inverter 10 is very low because the elements are composed of transistors.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a power conversion device installed in an AC electric vehicle configured to drive an AC motor using AC power supplied from a power feeder, and a method of operating the same. .

[Conventional technology]

FIG. 8 is a system configuration diagram showing a conventional example of an AC electric vehicle driven by an AC motor.

In FIG. 8, high voltage alternating current power from a trolley wire 1 is taken into the electric car via a pantograph 2, applied to a transformer 5, and discharged to a rail 4 via wheels 3.

The transformer 5 steps down the high voltage AC of 20kV to 25kV to a voltage suitable for the power converter installed in the next stage, and then converts it to the AC reactor! 2, a pulse width modulation converter 1 (hereinafter abbreviated as PWM) converter 1 as a power supply side conversion means.
After converting it into a DC voltage in step 3, this DC voltage is applied to a PWM inverter 14 as a load-side conversion means via a filter capacitor 9. Since the PWM inverter 14 converts input direct current into alternating current of a desired voltage and frequency and outputs it, the induction motor III that drives the electric car can freely change its speed.

FIG. 9 is a main circuit connection diagram showing the configuration of the PWM inverter 13 shown in FIG. 8, which includes four gate turn-off thyristors (hereinafter referred to as GT
(abbreviated as O-silisk) 40°41, 42.43 are connected in a single phase bridge, and four diodes 50.51.52
．． 53 are connected in antiparallel to each GTO thyristor.

FIG. 1O is a main circuit connection diagram showing the configuration of the PWM inverter 14 shown in FIG. 8, and includes six GTO thyristors 44.45°46, 47.
48 and 49 are connected in a 3-phase bridge, and 6 diodes 5
4.55.56.57.58.59 for each GTO
It is configured by connecting it in antiparallel to a thyristor.

[Problem to be solved by the invention]

When the conventional circuit shown in FIG. 8 is used, when the electric vehicle is in power running (that is, when energy flows from the power source to induction motor 11 via trolley wire 1) and when braking (that is, when energy flows from induction motor 11 to This has the advantage that both regeneration and regeneration to the power supply via the trolley wire 1 can be performed without switching the main circuit. It also has the advantage of being able to operate with a power factor of 1 on the power source side.

However, since both the power supply side conversion means and the load side conversion means use the GTO thyristor as a main component, the peripheral circuitry for operating the GTO thyristor becomes complicated and the number of parts increases. have. Furthermore, in order to perform PWM control, the GTO thyristor must be turned on and off at a high frequency, and as a result, the loss generated in the GTO thyristor and its snubber circuit increases, and the heat generated by this loss must be dissipated. However, this method has the disadvantage that the device is large and expensive, and the efficiency of the device is also reduced.

SUMMARY OF THE INVENTION An object of the present invention is to simplify the configuration of a power conversion device for an AC electric vehicle, and to improve device efficiency and smooth operation by reducing generated losses.

[Means for Solving the Problems] In order to achieve the above object, the power conversion device of the present invention connects a power supply side conversion means constituted by pure bridge connection of thyristors to an AC power supply, and a power conversion means constituted by transistors. An AC motor for driving an electric car is connected to the load side conversion means, and a filter consisting of a reactor and a capacitor is connected to the DC intermediate circuit that connects the DC side of the power supply side conversion means and the DC side of the load side conversion means. A switching means is inserted into the DC intermediate circuit to connect the circuit and switch the voltage polarity between the power running operation and the braking operation of the electric vehicle.

Also, since the power converter is configured like this,
When switching an electric vehicle from coasting operation to braking operation, first operate the load-side conversion means to increase the DC intermediate circuit voltage to a predetermined value, and then convert the regenerated energy from the AC motor into
It is only necessary to return the voltage to the AC power source through this DC intermediate circuit. When starting while backing up a slope, a dynamic braking resistor is installed in the DC intermediate circuit to prevent the DC intermediate circuit voltage from rising to an abnormal value when reversing. This voltage is then maintained at an appropriate level.

[Effect]

This invention is a power conversion device for an AC electric vehicle, in which a power-side converter configured with a pure bridge connection of Cyrisk, a PWM inverter configured with transistors as a load-side converter, and these two-way converters are combined. The DC intermediate circuit is equipped with a filter circuit and a changeover switch for changing voltage polarity, so that the changeover switch can be used to switch between powering operation and braking operation of the electric vehicle.
A regeneration conversion device becomes unnecessary. In addition, a power converter with this configuration can perform control to maintain the DC intermediate circuit voltage at an appropriate value even when an electric vehicle switches from coasting to braking operation or starts while backing up a slope. This allows the electric vehicle to be operated without any problems.

〔Example〕

FIG. 1 is a main circuit connection diagram showing an embodiment of the present invention.

A trolley wire 1, a pantograph 2, wheels 3, a rail 4, and a transformer 5 that supply AC power shown in FIG.
is the same as in the conventional circuit described above in FIG.

In the present invention, a thyristor rectifier 6 constituted by a pure bridge connection of thyristors serves as a power supply side conversion means, and a transistor inverter 10 constituted of transistors serves as a load side conversion means and converts direct current into alternating current by pulse width modulation control. The induction motor 11 is operated at a desired speed by being equipped with a filter circuit including a filter reactor 7 and a filter capacitor 9, and a changeover switch 8 for switching the voltage polarity of the DC intermediate circuit.

The changeover switch 8 has four contacts 8A, 8B, and 8C.

When the electric car is running, contacts 8A and 8B are turned on, contacts 8C and 8D are turned off, and the power from the AC power source is passed through the thyristor rectifier 6 → filter circuit →
It is applied to the induction motor 11 through the path of the transistor inverter IO.

Further, when the electric vehicle performs braking operation, contacts 8A and 8B are turned off, contacts 8C and 8D are turned on, and the energy regenerated by the induction motor 11 is returned to the AC power source through a path opposite to that described above.

In addition, since the thyristor rectifier 6 switches at the commercial frequency, the loss generated in this thyristor and its snubber circuit is transferred to the converter using pulse width modulation control (
can be significantly reduced.

Furthermore, since the inverter is composed of transistors, its loss is essentially small.

FIG. 2 is a circuit diagram showing the control of the power conversion device of the embodiment circuit shown in FIG.
I am employed.

Electric vehicles have three states: power running, braking, and coasting. Therefore, when the operation command input to the sequence circuit 15 is "power running", the sequence circuit 15 first gives the operation command to the inverter control circuit 17, and then turns on the contacts 8A and 8B of the changeover switch 8. , gives a forward conversion operation command to the rectifier control circuit 16 and an acceleration torque command to the inverter control circuit 17 almost simultaneously.

If the operation command is "braking", first contact OA.

After turning off contact 8B and turning on contacts 8C and 8D, a deceleration command is issued to the inverter control circuit 17 and the rectifier control circuit 16
The electric vehicle is braked by giving a reverse conversion operation command to the induction motor 11 almost simultaneously and regenerating energy from the induction motor 11 to the power source side.

If the operation command is "r coasting", the operation command from the sequence circuit 15 to the inverter control circuit 17 is turned off, and the operation of the transistor inverter IO is stopped. In this way, the current flowing through the induction motor 11 becomes zero, so if the coasting time is long and there is no need to build up torque at high speed, such as in an electric car, the amount of power saved will be large. There are some advantages.

By the way, when restarting energization to the induction motor 11 in order to shift from coasting operation to power running or braking operation, the desired torque cannot be generated until the induction motor 11 is energized, especially during braking. For transition to operation, contact 8C.

8D is turned on, the voltage of the filter capacitor 9 has a polarity that forward biases each element of the silice rectifier 6. Therefore, the silice rectifier 6 operates to regenerate the accumulated charge of the filter capacitor 9 to the AC power supply side, thereby lowering the DC input voltage of the transistor inverter 10, which may impede the normal operation of the transistor inverter 10.

FIG. 3 is a circuit diagram showing an example in which an electric vehicle equipped with the power conversion device of the example circuit shown in FIG. 1 can smoothly transition from coasting operation to braking operation.

In this FIG. 3, a transformer 5, a thyristor rectifier 6,
Filter reactor 7, changeover switch 8, filter capacitor 9, transistor inverter lO1 induction motor 1
1. The operations of the sequence circuit 15, the rectifier control circuit 16, and the inverter control circuit 17 have already been described in FIG. 2, so a description thereof will be omitted.

In the present invention, a voltage detector 21 detects the voltage of the filter capacitor 9, a comparator 22 detects that this detected voltage is higher than a set value, a setting resistor 23,
It includes an AND element 24 and a flip-flop 25.

When the sequence circuit 15 is commanded to "brake" during coasting, the sequence circuit 15 sends the reverse conversion operation command to the rectifier WAr! 1 circuit 16, but this command is blocked by the AND element 24, so the silice rectifier 6 remains stopped. On the other hand, the inverter control circuit 17
Since the deceleration torque command is given to the induction motor II
returns that energy to the DC intermediate circuit via the transistor inverter lO, so the filter capacitor 9
The voltage begins to rise.

When this voltage reaches the value determined by the setting resistor, a signal is sent from the comparator 22 to the AND element 24.
The above-mentioned inverse conversion operation command is applied from this AND element 24 to the flip-flop 25 and is sent thereto. Therefore, the rectifier control circuit 16 gives an operation signal according to this inverse conversion operation command to the SIRISK rectifier 6, and the energy returned to the DC intermediate circuit is regenerated to the AC power supply side, so that the electric vehicle during coasting operation is braked. condition, which causes the speed to decrease rapidly.

In addition, when an electric car attempts to start from a stopped state with the mechanical brakes applied in the middle of an uphill slope, the mechanical brakes are first released and then power running is started, but the device does not have an operating time limit. Because of the delay, when the mechanical brakes are released, the electric vehicle begins to back up the hill and then starts moving forward under power. This type of operation mode is called a backward start, but at the time of this backward start,
The electric motor once rotates in reverse, its speed becomes zero due to the braking action, and then rotates in the forward direction to begin power running.

FIG. 4 is a conventional operation waveform diagram showing the operation of each part when an electric car equipped with the power conversion device of the embodiment circuit shown in FIG. 1 starts backward, and (a) shows changes in motor speed. , (b) shows the change in the inverter current, and (c) shows the change in the filter capacitor voltage, respectively.

In Fig. 4, when the mechanical brake is released at time T1, the electric car moves backward (that is, the electric motor reverses) and a power running command is also output, but there is a delay in the operation, so T!
At time 13, the silice rectifier a6 starts operating, and at time 13, the filter capacitor 9 is charged and the transistor inverter IO starts operating. Here, the transistor inverter lO is given a command to operate in the forward rotation direction, so
This transistor inverter IO operates in the direction of reducing the motor speed, ie regenerative operation. As a result, the motor speed becomes zero at time 14, and thereafter the motor rotates in the normal rotation direction with a force jte.

However, during the period until this point 14 is reached, the thyristor rectifier 6 is in the power running mode, and the changeover switch 8 is
Since the motor is also in the power running position, all of the power regenerated from the induction motor 8111 via the transrisk inverter IO flows into the filter capacitor 9, greatly increasing its voltage (see Figure 4 (H)). )reference).

FIG. 5 is a circuit diagram showing an example of suppressing a rise in filter capacitor voltage when an electric vehicle equipped with the power conversion device of the example circuit shown in FIG. 1 starts backward.

Trolley wire l, pantograph 2, wheels 3, rails 4, transformer 5, thyristor rectifier 6 shown in FIG.
, the filter reactor 7, the changeover switch 8, the filter capacitor 9, the transistor inverter IO, and the induction motor 11 have already been described in FIG. 1, so their explanation will be omitted.

In the present invention, a series circuit of a chopper 32 as a switching element and a power absorption resistor 31 is connected in parallel to a filter capacitor 9, and the voltage of this filter capacitor 9 is detected by a voltage detector 21. This detected voltage is led to the comparator 33 and compared with the voltage set by the upper limit setter 34 and the voltage set by the lower limit setter 35, and the result is given to the base drive circuit 36 so that the voltage of the filter capacitor 9 is always maintained. The chopper 32 is turned on and off so that the voltage is between the upper limit voltage and the lower limit voltage.

FIG. 6 is a graph showing the state of the filter capacitor voltage in the embodiment circuit shown in FIG. 5, and the time T3 shown in FIG. This is the point in time when the inverter 10 starts regeneration operation.

FIG. 7 is an operation waveform diagram showing the operation of each part of the embodiment circuit shown in FIG. ) is the voltage change of filter capacitor 9, (d)
Each shows the operation of the chipper 32,
Tt, Tx, Ts 1. Each time point of Ta is the same as in the graph shown in FIG.

In FIG. 7, when the transistor inverter IO enters the regeneration mode at time T1 and the voltage of the filter capacitor 9 reaches the upper limit set value at time 71, the dust collar 32 starts operating, so that the filter This indicates that the capacitor voltage will not exceed the upper limit setting.

〔Effect of the invention〕

According to this invention, since a silice rectifier is used as a power supply side converter constituting a power conversion device mounted on an AC electric vehicle, switching operation is performed at the power frequency, and the loss is lower than that of PWM @ control. can be significantly reduced. On the other hand, since the transformer risk inverter as a load-side converter inherently has small switching loss,
PWM control allows precise control of the torque and speed of the induction motor used to drive electric vehicles. Furthermore, since powering operation and braking operation of the electric vehicle are switched by switching the voltage polarity of the DC intermediate circuit, the main circuit configuration of the power supply side converter can be simplified, and the main circuit configuration of the entire power converter, The effect of simplifying the control circuit and making the device smaller and lighter can be obtained.

Furthermore, when an electric vehicle equipped with a power converter with this configuration switches from coasting to braking, there is a risk that the input voltage of the transistor inverter will drop and braking will be inhibited due to the inverse conversion of the silice rectifier. This can be eliminated by properly controlling the movement. In addition, to avoid the possibility that the DC intermediate circuit voltage may rise abnormally when the electric car is started in reverse, a series circuit consisting of a chipper and a power absorption resistor is installed in this DC intermediate circuit to control the chipper so that the voltage is within a predetermined voltage range. Therefore, the configuration of the present invention has the effect that the AC electric vehicle can be operated smoothly without any trouble.

[Brief explanation of the drawing]

Fig. 1 is a main circuit connection diagram showing the embodiment of the present invention, Fig. 2 is a circuit diagram showing the control of the power conversion device of the embodiment circuit shown in Fig. 1, and Fig. 3 is the circuit diagram shown in Fig. 1. A circuit diagram showing an example in which an electric vehicle equipped with the power conversion device of the example circuit can smoothly transition from coasting operation to braking operation, FIG. 4 is a circuit diagram showing an example in which an electric vehicle equipped with the power conversion device of the example circuit shown in FIG. A conventional operation waveform diagram showing the operation of each part when an electric car starts backwards. Fig. 5 shows the filter capacitor voltage when an electric car equipped with the 11 converter of the embodiment circuit shown in Fig. 1 starts backwards. Circuit diagram showing an example of suppressing the increase in
The figure is a graph showing the state of the filter capacitor voltage in the example circuit shown in Figure 5, Figure 7 is an operation waveform diagram showing the operation of each part of the example circuit shown in Figure 5, and Figure 8 is an AC A circuit diagram showing a conventional example of an AC electric car driven by an electric motor, Figure 9 is a main circuit connection diagram showing the configuration of the PWM2 inverter shown in Figure 8, and Figure 1O is a circuit diagram showing the PWM2 inverter configuration shown in Figure 8.
FIG. 2 is a main circuit connection diagram showing the configuration of a WM inverter. l...trolley wire, 2...pantograph, 3...
Wheel 4...Rail, 5...Transformer, 6...Thyristor rectifier as a power supply side converter, 7...Filter reactor 8...Selector switch, 8A, 8B, 8C, 8
D...Contact, 9...Filter capacitor, 10...
・Transistor inverter as load side converter, 11
...Induction motor, 12...AC reactor, 13.
... PWM converter as a power supply side converter, 14...
・PWM inverter as load side conversion means, 15...
・Sequence circuit, 16... Rectifier control circuit, 17.
...Inverter control circuit, 21...Voltage detector, 22
...Comparator, 23...Setting resistor, 24...
AND element, 25...Flip-flop, 31...
Power absorption resistor, 32...Chopper, 33...Comparator, 34...Upper limit setter, 35...Lower limit setter, 36...Base drive unit, -/Tomi 11 yen] 4th port 7F 4F Clear 2Tor Figure 5 Figure 6 ■Work No. 70

Claims (1)

[Claims] 1) A power supply side conversion means constituted by a pure bridge connection of thyristors is connected to an AC power source, an AC motor for driving an electric vehicle is connected to a load side conversion means constituted of a transistor, and these power sources A filter circuit including a reactor and a capacitor is connected to a DC intermediate circuit that connects the DC side of the side conversion means and the DC side of the load side conversion means, and a filter circuit consisting of a reactor and a capacitor is connected to the DC side of the side conversion means and the DC side of the load side conversion means. A power conversion device for an AC electric vehicle, characterized in that a switching means for switching voltage polarity is inserted into the DC intermediate circuit. 2) Connect the power-side conversion means configured by pure bridge connection of thyristors to an AC power source, connect the AC motor for driving an electric vehicle to the load-side conversion means configured with transistors, and connect the DC side of these power-side conversion means A switching means that connects a filter circuit including a reactor and a capacitor to a DC intermediate circuit connecting the DC side and the DC side of the load-side conversion means, and switches the voltage polarity between powering operation and braking operation of the electric vehicle. When switching the electric vehicle equipped with a power conversion device configured to insert into the DC intermediate circuit from coasting operation to braking operation,
When the load-side conversion means is operated to raise the voltage of the capacitor to a predetermined voltage using the regenerated energy from the AC motor, the switching means is switched to braking operation, and then the AC voltage is increased through the power supply-side conversion means. A method of operating a power conversion device for an AC electric vehicle, which is characterized by regenerating energy to a power source. 3) Connect the power supply side conversion means configured by pure bridge connection of thyristors to an AC power source, connect the AC motor for driving an electric car to the load side conversion means configured with transistors, and connect the DC side of these power supply side conversion means A switching means that connects a filter circuit including a reactor and a capacitor to a DC intermediate circuit connecting the DC side and the DC side of the load-side conversion means, and switches the voltage polarity between powering operation and braking operation of the electric vehicle. When the electric vehicle equipped with a power conversion device configured to insert a power converter into the DC intermediate circuit starts moving backward on an inclined track, the switching means is in the power running position, and the switching means and the power absorption resistor are connected in series. A method for operating a power converter for an AC electric vehicle, characterized in that a circuit is connected in parallel to the capacitor, and the switching means is turned on and off so that the capacitor voltage is maintained within a predetermined voltage range.