JP4946106B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device, and more particularly, to a power conversion device that generates a drive voltage for driving a motor provided in an electric vehicle.

Conventionally, an “on-vehicle charger for an electric vehicle” (see Patent Document 1) including an inverter is known.
This “on-vehicle charger for an electric vehicle” is a charger for an electric vehicle that includes a drive device including at least a storage battery, an inverter that converts DC power of the storage battery into AC power, and an electric motor driven by the inverter. And a double-throw switch that connects the output of the inverter to the motor except when charging the storage battery, and connects the power from the charging plug cord to the inverter via an AC reactor when charging the storage battery. Further, there is provided a control circuit that performs drive control of the electric motor at times other than charging the storage battery and performs charge control of the storage battery at the time of charging.

In other words, since the inverter also has a function as a charger, the parts mounted on the electric vehicle for charging the storage battery can be minimized, and the weight and price of the electric vehicle can be reduced.
Japanese Patent Laid-Open No. 06-178407

However, in the conventional “on-vehicle charger for electric vehicles” (see Patent Document 1), the inverter is used as a part of the charging device to reduce the size, but an AC reactor, switching means, and the like are required. Therefore, an increase in the size of a system including an inverter is inevitable, and it has been difficult to realize a charging function with a small and lightweight means.
The objective of this invention is providing the power converter device which can reduce significantly the size and weight of the whole system provided with the power converter device.

In order to achieve the above object, the power conversion device according to the present invention generates and synthesizes pulses based on output voltages respectively supplied from an external power supply source and an internal DC power supply, thereby generating a driving voltage for a multiphase AC motor. In the power conversion device to be generated, at least one of the conversion units corresponding to each phase of the multiphase AC motor selects one of the potential voltages corresponding to the external power supply source and the internal DC power supply. A current smoothing means connected in parallel with the external power supply source , and by synthesizing the voltage between the terminals of the current smoothing means and the voltage supplied from the internal DC power supply. A drive voltage to be supplied to the multiphase AC motor is generated .

According to the present invention, a power converter that generates a driving voltage of a multiphase AC motor by generating and synthesizing pulses based on output voltages respectively supplied from an external power supply source and an internal DC power supply At least one of the converters corresponding to each phase of the motor is configured by switch means for selecting and outputting one of the potential voltages corresponding to the external power supply source and the internal DC power supply, and the external power supply source and A current smoothing means connected in parallel is provided, and a drive voltage to be supplied to the multiphase AC motor is generated by synthesizing the voltage between the terminals of the current smoothing means and the voltage supplied from the internal DC power supply .
For this reason, the size and weight of the entire system including the power conversion device can be significantly reduced.

The best mode for carrying out the present invention will be described below with reference to the drawings.
(First embodiment)
FIG. 1 is a circuit diagram of a motor drive system including a power converter according to the first embodiment of the present invention. As shown in FIG. 1, the power converter 10 constitutes a motor drive system that drives the motor 12 together with the voltage supply means 11, and applies the voltage supplied from the voltage supply means 11 to the motor 12. Generate voltage.

  The voltage supply means 11 includes a battery 13 and an external voltage input terminal 14, and a low potential side terminal of the battery 13 and the external voltage input terminal 14 are connected to form a common potential (that is, a GND potential). A smoothing capacitor 15 is connected between the positive electrode and the negative electrode of the battery 13, and a smoothing capacitor 16 is connected between the positive electrode and the negative electrode of the external voltage input terminal 14. The voltage supply means 11 includes three potentials, that is, a GND potential, an external voltage potential Voi, and a high potential side potential Vb of the battery 13. However, the external voltage input terminal 14 is connected to the external voltage when charging the battery 13 with the power supplied from the external voltage or supplying the battery power to the external voltage. In other cases, the external voltage input terminal 14 is connected to the external voltage. Not connected to.

The motor 12 is a three-phase AC motor, and is driven by applying an AC voltage output from the power converter 10.
The power conversion device 10 is a DC-AC conversion unit that generates a voltage to be applied to the motor 12 based on the three potential voltages output from the voltage supply unit 11. Each corresponding switch means has the same configuration. The description here is given for the U-phase switch means 17, and the description of the V-phase switch means 18 and the W-phase switch means 19 having the same configuration and operation is omitted.

The switch means 17 generates a voltage to be output to the U phase of the motor 12, and selects and connects any one of the GND potential, the external voltage potential Voi, and the high potential side potential Vb of the battery 13. To do. And the voltage required for the motor 12 is supplied by changing the ratio of the time to connect to each electric potential.
FIG. 2 is a circuit diagram of a motor drive system specifically showing the switch means of FIG. As shown in FIG. 2, each switch means 17, 18, 19 corresponding to the U, V, W phase is composed of three sets of bidirectional switches 17a-17c, 18a-18c, 19a-19c, One of the three sets of bidirectional switches is driven to turn on. Each bidirectional switch is formed by combining two active elements having a switching function, for example, transistors.

Next, the operation of the motor drive system will be described.
The power conversion device 10 has two functions. One is a function of generating a voltage required for the motor 12 using the three potential voltages of the voltage supply means 11, and the other is a battery 13 and an external voltage input terminal 14 constituting the voltage supply means 11, respectively. This is a function for setting the power supplied by the power supply to an arbitrary value.
The former function generates an AC voltage required for the motor 12 according to the operating point of the motor 12 from a three-level DC voltage by pulse width modulation (PWM).

  The latter function is the center of the present invention. When the motor 12 is driven using a power supply source capable of storing electrical energy such as the battery 13 as a power source, it is necessary to charge it. For example, in a system such as an electric vehicle (EV), it is necessary to charge the battery if the state of charge (SOC) of a battery, which is an electric energy storage unit, is reduced. Further, if battery power such as EV can be supplied to the power source of the system, the EV battery can be used as an emergency power source.

  In this power conversion device 10, when each of the switch means 17, 18, 19 corresponding to the U, V, W phases generates a voltage to be output to each phase of the motor 12, the high potential side potential Vb of the battery 13 is The ratio of the power supplied from the battery 13 and the power supplied from the external voltage input terminal 14 is adjusted by adjusting the time ratio and timing of connection to the external voltage potential Voi. When the external voltage input terminal 14 is connected to an external power source (not shown), when charging the battery 13, power from the external power source is supplied to the battery 13 via the motor 12. Further, when the power of the battery 13 is returned to the system power supply, the power of the battery 13 is supplied via the motor 12.

  FIG. 3 is a circuit diagram showing a flow of electric power in the motor drive system of FIG. As shown in FIG. 3, P1 is a flow of power supplied from the external power source to the motor 12, P2 is a flow of power supplied from the battery 13 to the motor 12, and P3 is a flow of power supplied from the motor 12 to the battery 13. A flow P4 indicates a flow of electric power supplied from the motor 12 to the external power source.

  When charging the battery 13, the bidirectional switches 17a to 17c, 18a to 18c, and 19a to 19c of the switch means 17, 18, and 19 are switched so as to realize P1 and P3. Thereby, since electric power is supplied to the battery 13 via the motor 12, a current flows through the motor 12, but a current that causes the output torque of the motor 12 to be zero, for example, a d-axis current flows. In this case, since the motor output torque is 0, the motor 12 is not driven.

When the power of the battery 13 is returned to the system power supply, the bidirectional switches 17a to 17c, 18a to 18c, and 19a to 19c of the switch means 17, 18, and 19 are switched so as to realize P2 and P4. . Also in this case, for example, control is performed so that only the d-axis current flows.
Next, a case where the motor 12 is driven only by the battery 13 after being disconnected from the external power source will be described. In this case, the motor 12 can be driven if the power of the path P2 is supplied. However, in this embodiment, the motor 12 is driven while controlling the voltage between the capacitor terminals by controlling the electric power flowing into and out of the capacitor 16 according to the driving state of the motor 12, that is, P1 and P4.

In this way, in a region where the motor rotation speed is high, the voltage between terminals of the capacitor 16 can be driven while being held at a voltage higher than the battery voltage Vb. A high voltage can be supplied.
That is, the motor 12 is driven by pulse width modulation. At this time, the current flowing through the DC bus is a pulsed current. Looking at the pulsed current for each phase, it is positive or negative. However, when the pulsed current is averaged over time, it is positive when the motor is running (in the direction from the power source to the motor 12) and negative during motor regeneration (from the motor 12). Power direction). When the motor 12 is simply driven using the battery voltage, pulse width modulation is performed by turning ON / OFF the bidirectional switches 17a, 17c, 18a, 18c, 19a, 19c connected to the battery 13 side, The bidirectional switches 17b, 18b, and 19b may be turned off.

  In this embodiment, in a region where the motor rotation speed is high, the bidirectional switches 17b, 18b, 19b are also turned on / off so that a part of the power supplied from the battery 13 to the motor 12 is returned to the capacitor 16. By doing in this way, the voltage between the terminals of the capacitor 16 can be made higher than the battery voltage. In this way, a higher voltage than the battery voltage is supplied to the motor 12 by the combination of the high voltage and the battery voltage. The external voltage may be direct current or alternating current.

  As described above, in this embodiment, when the battery 13 is charged or when battery power is returned to the system, the power is moved while the motor torque is set to zero. When the motor 12 is driven, the voltage applied to the motor 12 is controlled by the battery voltage by controlling the voltage between terminals of the capacitor 16 connected in parallel to the external voltage input terminal 14 which is a terminal for connecting an external power source. It becomes possible to generate from a different DC voltage. Therefore, compared with the case where voltage is directly supplied from the battery 13, the motor output can be increased or the loss can be reduced.

  This eliminates the need for a reactor and a changeover switch for switching between a motor and an AC power source, which are required in the conventional example, so that the size and weight of the entire system including the power conversion device can be greatly reduced. . In addition, when driving a motor, not only power is supplied directly from the battery, but also the power charged in the capacitor can be used. For example, a high voltage is supplied to the motor when the motor rotation speed is high. Thus, the motor output can be increased or the loss can be reduced.

(Second Embodiment)
FIG. 4 is a circuit diagram of a motor drive system according to the second embodiment of the present invention. As shown in FIG. 4, this motor drive system includes a rectifier 21 between the external voltage input terminal 14 and the power converter 20, and accordingly, the power converter 20 is connected to the switch means 17, 18, 19. In place of the bidirectional switches 17c, 18c, and 19c connected to the GND potential, bidirectional switches 22, 23, and 24 formed by combinations of transistors and diodes as active elements are provided. Other configurations and operations are the same as those of the motor drive system (see FIG. 2) of the first embodiment.
The rectifying means 21 is composed of a half-wave rectifier circuit. By providing the rectifying means 21, the configuration of the power conversion device 20 is simpler than that of the power conversion device 10 of the first embodiment (see FIG. 2). Can be

(Third embodiment)
FIG. 5 is a circuit diagram of a motor drive system according to the third embodiment of the present invention. As shown in FIG. 5, this motor drive system is provided with a rectifying means 25 constituted by a full-wave rectifier circuit instead of the rectifying means 21 constituted by a half-wave rectifier circuit. Other configurations and operations are the same as those of the motor drive system (see FIG. 4) of the second embodiment.
By providing the rectifying means 25 configured by a full-wave rectifier circuit, the time for charging the battery 13 can be shortened as compared with the power converter 20 (see FIG. 4) of the second embodiment.

(Fourth embodiment)
FIG. 6 is a circuit diagram of a motor drive system according to the fourth embodiment of the present invention. As shown in FIG. 6, this motor drive system is limited to the application under the condition that the voltage input from the external voltage input terminal 14 is smaller than the battery voltage. Under such conditions, the power converter 26 replaces the bidirectional switches 17b, 18b, 19b of the switch means 17, 18, 19 connected to the external voltage input terminal 14 with transistors and diodes as active elements. Bi-directional switches 27, 28, 29 formed by combination are provided. Other configurations and operations are the same as those of the motor drive system (see FIG. 5) of the third embodiment.
Thereby, the structure of the power converter device 26 can be simplified compared with the power converter device (refer FIG. 5) of 3rd Embodiment.

As described above, the power conversion device according to the present invention generates a drive voltage for a multiphase AC motor by generating and synthesizing pulses based on output voltages respectively supplied from an external power supply source and an internal DC power supply. In the power conversion device, at least one of the conversion units corresponding to each phase of the multiphase AC motor selects and outputs one of the potential voltages corresponding to the external power supply source and the internal DC power supply. Current smoothing means connected in parallel with the external power supply source , and by combining the voltage between the terminals of the current smoothing means and the voltage supplied from the internal DC power source. A drive voltage to be supplied to the phase AC motor is generated . The power supplied from the external power supply source is alternating current.

As a result, AC and DC are input to one power converter, and power can be freely taken out from a plurality of external power supply sources by switching of a switch means such as a semiconductor switch. In addition to having a function of charging a battery or the like as well as being able to supply power, when driving a motor, the voltage between terminals of a capacitor connected in parallel to the external power supply means is variably controlled. Ru can be variably controlling the DC bus voltage in accordance with the motor rotational speed without additional external circuitry. Moreover, since power can be supplied to a power supply means that can store power from a power supply source that outputs AC voltage only by the power conversion device, that is, it can be charged, mechanical connection switching other than the power conversion device is possible. No switches or reactors are required. Further, even when all external power supply sources are direct current, power can be supplied to the power supply means that can store power only by the power conversion device, that is, can be charged.

  In addition, when charging the external DC power source from the external power supply source, only the d-axis current is allowed to flow through the multiphase AC motor. As a result, the electric power can be moved, that is, charged, to an electric power supply means capable of storing electric power from an external electric power supply source while keeping the output torque of the motor at zero. For example, when the present invention is implemented in a power conversion device for a traveling motor of a vehicle such as an EV, motor torque is not output during battery charging.

Thus, according to the present invention, a power converter that generates a driving voltage for a multiphase AC motor by generating and synthesizing pulses based on output voltages respectively supplied from an external power supply source and an internal DC power supply. , At least one of the converters corresponding to each phase of the multiphase AC motor is constituted by switch means for selecting and outputting one of the potential voltages corresponding to the external power supply source and the internal DC power supply, a current smoothing means connected in parallel with the power source, that generates a drive voltage to be supplied to the multiphase AC motor by combining the voltage supplied from the terminal voltage and the internal DC power supply of the current smoothing means Therefore, the size and weight of the entire system including the power conversion device can be significantly reduced.

It is a circuit diagram of a motor drive system provided with a power converter concerning a 1st embodiment of this invention. FIG. 2 is a circuit diagram of a motor drive system specifically showing the switch means of FIG. 1. It is a circuit diagram which shows the flow of the electric power in the motor drive system of FIG. It is a circuit diagram of the motor drive system which concerns on 2nd Embodiment of this invention. It is a circuit diagram of the motor drive system which concerns on 3rd Embodiment of this invention. It is a circuit diagram of the motor drive system which concerns on 4th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 20, 26 Power converter 11 Voltage supply means 12 Motor 13 Battery 14 External voltage input terminal 15, 16 Capacitors 17, 18, 19 Switch means 17a-17c, 18a-18c, 19a-19c, 22, 23, 24, 27, 28, 29 Bidirectional switch 21, 25 Rectification means P1, P2, P3, P4 Flow of power

Claims (5)

A power conversion device that generates a driving voltage for a multiphase AC motor by generating and synthesizing pulses based on output voltages respectively supplied from an external power supply source and an internal DC power source,
At least one of the converters corresponding to each phase of the multiphase AC motor is configured by switch means for selecting and outputting one of the potential voltages corresponding to the external power supply source and the internal DC power supply,
Current smoothing means connected in parallel with the external power supply source ;
A power converter for generating a drive voltage to be supplied to the multiphase AC motor by synthesizing a voltage between terminals of the current smoothing means and a voltage supplied from the internal DC power supply .   The power converter according to claim 1, wherein the power supplied from the external power supply source is alternating current.   3. The power conversion according to claim 1, wherein the switch unit disposed between the external power supply source and the common negative electrode bus of the internal DC power source and the multiphase AC motor is a bidirectional switch. apparatus.   The said external power supply source is connected via the rectifier, The power converter device as described in any one of Claims 1-3 characterized by the above-mentioned.   5. The power conversion device according to claim 1, wherein, when charging the external DC power source from the external power supply source, only the d-axis current is allowed to flow through the multiphase AC motor.

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