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US 5,321,599 AGranted
Control apparatus for suppressing a third harmonic neutral point voltage in a three level inverter
AssigneeHitachi, Ltd.
InventorsTokunosuke Tanamachi, Kiyoshi Nakata, Kiyoshi Nakamura
Life of this patent
Estimating the term…
Abstract
The present invention relates to a control apparatus of a three-level inverter and intends to provide a control apparatus of simplified construction which can suppress a fluctuation in neutral point voltage effectively. Only a third harmonic component which is particularly large in the fluctuation in neutral point voltage is suppressed, a third harmonic component for suppression has a ratio of amplitude to that of a fundamental wave and a phase which are set to be constant regardless of the inverter frequency, and this third harmonic component is applied to a command of the fundamental wave.
Claims9
A control apparatus of power converter comprising:
- a plurality of capacitors connected in series to divide DC voltage;
- a power converter fed with direct current from said capacitors and operative to convert the direct current into AC phase voltages each having three or more levels of potential;
- and
- modulating wave generator means for generating a command of a fundamental wave of alternating current delivered out of said power converter;
- wherein said modulating wave generator means has means for applying to said fundamental wave a third harmonic component thereof, and said third harmonic component is derived using values which do not change with the frequency of said fundamental wave.
2 more elements
A control apparatus of power converter comprising:
- a plurality of capacitors connected in series to divide DC voltage;
- a power converter fed with direct current from said capacitors and operative to convert the direct current into AC phase voltages each having three or more levels of potential;
- and
- modulating wave generator means for generating a command of a fundamental wave of alternating current delivered out of said power converter;
- wherein said modulating wave generator means has means for applying to said fundamental wave a third harmonic component thereof in a predetermined frequency region of said fundamental wave, and said third harmonic component has a ratio of amplitude to that of said fundamental wave and a phase which are constant.
2 more elements
A control apparatus of power converter comprising:
- a plurality of capacitors connected in series to divide DC voltage;
- a power converter fed with direct current from said capacitors and operative to convert the direct current into AC phase voltages each having three or more levels of potential;
- and
- modulating wave generator means for generating a command of a fundamental wave of alternating current delivered out of said power converter;
- wherein said modulating wave generator means has means for applying to said fundamental wave a third harmonic component thereof, and said third harmonic component has a constant ratio of amplitude to that of said fundamental wave and a phase relative to said fundamental wave which changes with the frequency thereof.
2 more elements
A control apparatus of power converter comprising:
- a plurality of capacitors connected in series to divide DC voltage;
- a power converter fed with direct current from said capacitors and operative to convert the direct current into AC phase voltages each having three or more levels of potential;
- and
- modulating wave generator means for generating a command of a fundamental wave of alternating current delivered out of said power converter;
- wherein said modulating wave generator means has means for applying to said fundamental wave a third harmonic component thereof, and said third harmonic component has a ratio of amplitude to that of said fundamental wave which changes with the frequency thereof and a constant phase relative to said fundamental wave.
2 more elements
A control apparatus of power converter comprising:
- a plurality of capacitors connected in series to divide DC voltage;
- power converter fed with direct current from said capacitors and operative to convert the direct current into AC phase voltages each having three or more levels of potential;
- and
- modulating wave generator means for generating a command of a fundamental wave of alternating current delivered out of said power converter;
- wherein said modulating wave generator means is means for applying, in a first frequency region of said fundamental wave, a third harmonic component thereof having a ratio of amplitude to that of said fundamental wave and a phase which change with the frequency of said fundamental wave and applying, in a second frequency region of said fundamental wave, a third harmonic component thereof having a ratio of amplitude to that of said fundamental wave and a phase which are constant.
2 more elements
A control apparatus of power converter comprising:
- a plurality of capacitors connected in series to divide DC voltage;
- a power converter fed with direct current from said capacitors and operative to convert the direct current into AC phase voltages each having three or more levels of potential;
- modulating wave generator means for generating a command of a fundamental wave of alternating current delivered out of said power converter;
- and
- modulating means having a modulating region which expresses a half period of an output phase voltage of said fundamental wave by delivering positive and negative pulses to said power converter alternately;
- wherein said modulating wave generator means is means for applying, in a region other than said modulating region, a third harmonic component of said fundamental wave having a ratio of amplitude to that of said fundamental wave and a phase which are constant.
3 more elements
A control apparatus of power converter comprising:
- a plurality of capacitors connected in series to divide DC voltage;
- a power converter fed with direct current from said capacitors and operative to convert the direct current into AC phase voltages each having three or more levels of potential;
- modulating wave generator means for generating a command of a fundamental wave of alternating current delivered out of said power converter;
- and
- modulating means having a modulating region which expresses a half period of an output phase voltage of said fundamental wave by delivering positive and negative pulses to said power converter alternately;
- wherein said modulating wave generator means is means for applying, in a region inclusive of said modulating region, a third harmonic component having a ratio of amplitude to that of said fundamental wave and a phase which are constant.
3 more elements
A control apparatus of power converter comprising:
- a plurality of capacitors connected in series to divide DC voltage;
- a power converter fed with direct current from said capacitors and operative to convert the direct current into AC phase voltages each having three or more levels of potential;
- and
- modulating wave generator means for generating a command of a fundamental wave of alternating current delivered out of said power converter;
- wherein said modulating wave generator means is means for preparing, from said fundamental wave, a unit sine wave having a frequency which is three times the frequency of said fundamental wave and applying, to said fundamental wave, a third harmonic component having a ratio of amplitude to that of said fundamental wave and a phase which change with the frequency of said fundamental wave.
2 more elements
A control apparatus of power converter comprising:
- a plurality of capacitors connected in series to divide DC voltage;
- a power converter fed with direct current from said capacitors and operative to convert the direct current into AC phase voltages each having three or more levels of potential;
- and
- modulating wave generator means for generating a command of a fundamental wave of alternating current delivered out of said power converter;
- wherein said modulating wave generator means is means for preparing, from said fundamental wave, a unit sine wave having a frequency which is three times the frequency of said fundamental wave and applying, to said fundamental wave, a third harmonic component having a ratio of amplitude to that of said fundamental wave and a phase which change with the power-factor angle.
2 more elements
Dependencies are inferred from the claim text.