Power conversion device

Patent metadata

Field	Value
Publication number	US-9975449-B2
Application number	US-201615518125-A
Country	US
Kind code	B2
Filing date	Jan 14, 2016
Priority date	Jan 21, 2015
Publication date	May 22, 2018
Grant date	May 22, 2018

Abstract

A power convertor including an inverter driving a motor generator, a first DC/DC converter connected to a DC bus of the inverter, a second DC/DC converter varying voltage of the DC bus, and a control device controlling the inverter, the first DC/DC converter, and the second DC/DC converter. The power converter is a power conversion device setting voltage of the DC bus in a second control state higher than a voltage of the DC bus in a first control state by controlling the second DC/DC converter according to the control device. By setting the voltage of the DC bus of the inverter to a low voltage when it is not necessary, it is possible to reduce loss in the inverter and the step-down DC/DC converter, and to downsize the inverter and the step-down DC/DC converter.

First claim

The invention claimed is:

1. A power conversion device, comprising:
an inverter for driving a motor generator,
a first electric storage device for supplying power to electric components,
a first DC/DC converter for connecting a DC bus of the inverter and the first electric storage device,
a plurality of electrically insulated second electric storage devices,
a second DC/DC converter using the plurality of electrically insulated second power storage devices as an input power source, and
a control device for controlling the motor generator, the first DC/DC converter, and the second DC/DC converter, wherein
the second DC/DC converter includes a first half bridge and a second half bridge,
the first half bridge includes a first switching element and a second switching element connected in series to each other and is connected between terminals of one of the plurality of second electric storage devices,
the second half bridge includes a third switching element and a fourth switching element connected in series to each other and is connected between terminals of other second electric storage devices,
a connection point of the third switching element and the fourth switching element of the second half bridge is connected to the first half bridge,
a connection point between the first switching element and the second switching element of the first half bridge is connected to the DC bus via a smoothing element shared by the first half bridge and the second half bridge, and wherein
the control device selectively switches among the plurality of electrically insulated second electric storage devices by controlling switching of the switching elements of each of the first half bridge and the second half bridge by controlling output of the second DC/DC converter, voltage of the DC bus in a first control state is lower than the voltage of the DC bus in a second control state.

2. The power conversion device according to claim 1 , wherein the first electric storage device is a high energy density type electric storage device and the second electric storage device is a high electric power density type electric storage device.

3. The power conversion device according to claim 1 , wherein the control device controls the second DC/DC converter so that, in a case that the first control state is a control state when the motor generator is started, the voltage of the DC bus in the first control state is made lower than the voltage of the DC bus in the second control state.

4. The power conversion device according to claim 1 , wherein the control device controls the second DC/DC converter so that, in a case that the first control state is a control state that the electrical component fed from the first DC/DC converter is in a heavy load state, the voltage of the DC bus in the first control state is made lower than the voltage of the DC bus in the second control state.

5. The power conversion device according to claim 1 , wherein the control device controls the second DC/DC converter so that the second control state is a time of deceleration energy regeneration or torque assist, the voltage of the DC bus in the second control state is made higher than the voltage of the aforesaid DC bus in the first control state.

6. The power conversion device according to claim 1 , wherein output voltage of the second DC/DC converter is changed in a pulse-like waveform.

7. The power conversion device according to claim 1 , wherein output voltage of the second DC/DC converter is changed in a stepwise waveform.

8. The power conversion device according to claim 1 , wherein output voltage of the second DC/DC converter is changed in a ramp waveform.

9. The power conversion device according to claim 8 , wherein control device controls a plurality of switching elements constituting the second DC/DC converter with the control device so that the output voltage of the second DC/DC converter is changed as a ramp waveform as an output voltage obtained by combining the switching operation of the plurality of switching elements and the switching operation of the switching element of the second DC/DC converter.

10. The power conversion device according to claim 1 , comprising a third DC/DC converter for supplying power to the second electrical component with the DC bus as an input power source.

11. The power conversion device according to claim 10 , the third DC/DC converter is a step-up DC/DC converter which is controlled by the control device in order to feed an output voltage at a lowest step-up ratio in an input voltage range and an output voltage range of the third DC/DC converter to the second electrical component.

12. The power conversion device according to claim 1 , wherein an inductor in the second DC/DC converter is substituted with a parasitic inductance component between the second DC/DC converter and the DC bus.

13. The power conversion device according to claim 1 , wherein, in the first control state, the plurality of second electric storage devices are connected in series to each other and are connected to the DC bus via the second DC/DC converter, and in the second control state, the plurality of second electric storage devices are alternately and independently connected to the DC bus via the second DC/DC converter.

14. The power conversion device according to claim 1 , wherein the plurality of aforesaid second DC/DC converters are operated so that, in the first control state, the second electric storage device having the highest charge state among the plurality of second electric storage devices is connected to the DC bus, and in the second control state, the second electric storage device having the lowest charge state among the plurality of second electric storage devices is connected to the DC bus.

Assignees

• Mitsubishi Electric Corp

Inventors

• Takeshima Yoshihiro
• Yamada Masaki

Classifications

• B60Y2200/92

  Hybrid vehicles · CPC title

• H02M7/53871

  with automatic control of output voltage or current · CPC title

• B60L7/14

  for vehicles propelled by AC motors · CPC title

• B60L7/16

  for vehicles comprising converters between the power source and the motor · CPC title

• B60L11/1803

  Operations & Transport · mapped topic