Power Conversion Device

• US 20140340005A1
• Filed: 10/22/2012
• Published: 11/20/2014
• Est. Priority Date: 11/01/2011
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Nagata, Koichiro, Iwaji, Yoshitaka, Sakai, Toshifumi, Shimada, Motomi
• Granted Patent: US 9,350,284 B2
• Time in Patent Office: Days
• US Class Current: 318/151
• CPC Class Codes: H02P 21/05 specially adapted for damping motor oscillations, e.g. for reducing hunting
• CPC Class Codes: H02P 21/22 Current control, e.g. using a current control loop
• CPC Class Codes: H02P 23/04 specially adapted for damping motor oscillations, e.g. for reducing hunting
• CPC Class Codes: H02P 27/06 using dc to ac converters or inverters H02P27/05 takes precedence
• CPC Class Codes: H02P 9/102 for limiting effects of transients

Abstract

In a system for driving an electric motor by an engine generator, there is a possibility that the effects of harmonics and DC voltage fluctuations of a power converter cause shaft oscillation to increase due to a phenomenon in which current pulsations caused by voltage disturbances at a d-axis and a q-axis are strengthened each other and thus oscillation and d-axis current are increased under the effect of interference between the d-axis and the q-axis. In an engine generator system, a power converter (105) controls a generator (104) by regulating the d-axis voltage Vd* by an amount of ΔVd* using d-axis voltage adjusting means (117) so that the phase of an oscillating component included in the d-axis current in the rotor magnetic flux direction of the generator (104) advances by 90 degrees or more with respect to the phase of an oscillating component of the identical frequency included in the rotating electric angular frequency of the generator (104), and further by regulating the q-axis voltage Vq* by an amount of ΔVq* using q-axis voltage adjusting means (118) so that the phase of an oscillating component included in the q-axis current advances by 90 degrees or more with respect to the phase of an oscillating component of the identical frequency included in the rotating electric angular frequency of the generator (104).

Claims

1. A power conversion device for an engine generator system,

the engine generator system comprising:

a generator;

an engine for driving the generator;

a PWM signal controller for performing pulse width modulation on a three-phase voltage command signal via a carrier signal, the three-phase voltage command signal being in accordance with current flowing through the generator;

a power conversion device driven by a pulse width modulated gate signal;

an electric motor; and

a power converter for driving the electric motor,

wherein the power conversion device regulates a voltage command on a d-axis in the magnetic flux direction of a rotor in the generator so that the phase of an oscillating component included in current of the d-axis in the generator advances 90 degrees or more with respect to the phase of an oscillating component of identical frequency included in a rotating electric angular frequency of the generator, and further regulates a voltage command on a q-axis perpendicular to the d-axis so that the phase of an oscillating component included in current of the q-axis advances 90 degrees or more with respect to the phase of an oscillating component of the identical frequency included in the rotating electric angular frequency of the generator.

3. The power conversion device according to claim 1 or claim 2,

wherein, in a case where the points of intersection of a mean value of a waveform representing an oscillating component in the rotating electric angular frequency and the waveform of the oscillating component are specified as zero points, and the points of intersection of a mean value of a waveform representing oscillating components of an oscillation frequency in current of the q-axis as well as current of the d-axis and the waveform of the oscillating components are specified as zero points, the power conversion device regulates a voltage command so that zero points acquired from a waveform of oscillating components in current of the q-axis and current of the d-axis advance by 90 degrees or more with respect to zero points acquired from a waveform of an oscillating component in the rotating electric angular frequency.

4. The power conversion device according to claim 3,

wherein means for regulating the voltage command comprises any one of:

proportion;

proportion and first-order lag;

proportion and differentiation;

proportion, first-order lag and inexact differentiation;

proportion and inexact differentiation; and

proportion, differentiation and inexact differentiation.

5. The power conversion device according to claim 1 or claim 2,

wherein, specifying a distance between the peak values of a waveform of an oscillating component in the rotating electric angular frequency as 180 degrees and a distance between the peak values of a waveform of oscillating components in current of the q-axis and current of the d-axis as 180 degrees, the power conversion device regulates a voltage command so that a maximum peak value of oscillating components in current of the q-axis and current of the d-axis advances by 90 degrees or more with respect to a maximum peak value acquired from a waveform of an oscillating component in the rotating electric angular frequency.

6. The power conversion device according to claim 5,

wherein means for regulating the voltage command comprises any one of:

proportion;

proportion and first-order lag;

proportion and differentiation;

proportion, first-order lag and inexact differentiation;

proportion and inexact differentiation; and

proportion, differentiation and inexact differentiation.

2. A power conversion device for an electric motor driving system,

the electric motor driving system comprising:

an electric motor;

a PWM signal controller for performing pulse width modulation on a three-phase voltage command signal via a carrier signal, the three-phase voltage command signal being in accordance with current flowing through the electric motor; and

a power conversion device driven by a pulse width modulated gate signal,

wherein the power conversion device regulates a voltage command on a d-axis in the magnetic flux direction of a rotor in the electric motor so that the phase of an oscillating component included in current of the d-axis in the electric motor advances 90 degrees or more with respect to the phase of an oscillating component of identical frequency included in a rotating electric angular frequency of the electric motor, and further regulates a voltage command on a q-axis perpendicular to the d-axis so that the phase of an oscillating component included in current of the q-axis advances 90 degrees or more with respect to the phase of an oscillating component of the identical frequency included in the rotating electric angular frequency of the electric motor.

7. A power conversion device for an engine generator system,

the engine generator system comprising:

a generator;

an engine for driving the generator;

a PWM signal controller for performing pulse width modulation on a three-phase voltage command signal via a carrier signal, the three-phase voltage command signal being in accordance with current flowing through the generator;

a power conversion device driven by a pulse width modulated gate signal;

an electric motor; and

a power converter for driving the electric motor,

wherein the power conversion device regulates an AC voltage command so that the phase of an oscillating component included in AC current of the generator advances 90 degrees or more with respect to an oscillating component of identical frequency included in a rotating electric angular frequency of the generator.

9. The power conversion device according to claim 7 or claim 8,

wherein, in a case where the points of intersection of a mean value of a waveform representing an oscillating component in the rotating electric angular frequency and the waveform of the oscillating component are specified as zero points, and the points of intersection of a mean value of a waveform representing an oscillating component of an oscillation frequency in the AC current and the waveform of the oscillating component are specified as zero points, the power conversion device regulates a voltage command so that zero points acquired from a waveform of an oscillating component in the AC current advance by 90 degrees or more with respect to zero points acquired from a waveform of an oscillating component in the rotating electric angular frequency.

10. The power conversion device according to claim 9,

wherein means for regulating the voltage command comprises any one of:

proportion;

proportion and first-order lag;

proportion and differentiation;

proportion, first-order lag and inexact differentiation;

proportion and inexact differentiation; and

proportion, differentiation and inexact differentiation.

11. The power conversion device according to claim 7 or claim 8,

wherein, specifying a distance between the peak values of a waveform of an oscillating component in the rotating electric angular frequency as 180 degrees and a distance between the peak values of a waveform of an oscillating component in the AC current as 180 degrees, the power conversion device regulates a voltage command so that a maximum peak value of an oscillating component in the AC current advances by 90 degrees or more with respect to a maximum peak value acquired from a waveform of an oscillating component in the rotating electric angular frequency.

12. The power conversion device according to claim 11,

wherein means for regulating the voltage command comprises any one of:

proportion;

proportion and first-order lag;

proportion and differentiation;

proportion, first-order lag and inexact differentiation;

proportion and inexact differentiation; and

proportion, differentiation and inexact differentiation.

8. A power conversion device for an electric motor driving system,

the electric motor driving system comprising:

an electric motor;

a PWM signal controller for performing pulse width modulation on a three-phase voltage command signal via a carrier signal, the three-phase voltage command signal being in accordance with current flowing through the electric motor; and

a power conversion device driven by a pulse width modulated gate signal,

wherein the power conversion device regulates an AC voltage command so that the phase of an oscillating component included in AC current of the electric motor advances 90 degrees or more with respect to an oscillating component of identical frequency included in a rotating electric angular frequency of the electric motor.