METHOD AND APPARATUS FOR BYPASSING CASCADED H-BRIDGE (CHB) POWER CELLS AND POWER SUB CELL FOR MULTILEVEL INVERTER
First Claim
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1. A power conversion system, comprising:
- a plurality of power stages connected in series to form a multilevel inverter circuit for connection to a load, the power stages individually comprising;
a DC link capacitor coupled between first and second DC link nodes of a DC link circuit,an output coupled with at least one other power stage in the multilevel inverter circuit,a switching circuit including a plurality of switching devices to provide an output voltage signal having an amplitude of one of at least two discrete levels, anda single relay or contactor including;
a coil,a plurality of normally closed contacts operative in a first state to allow current to flow between the switching circuit and the output when the coil is deenergized, and operative in a second state to electrically isolate the switching circuit from the output when the coil is energized, anda normally open contact coupled across the output to allow normal operation of the output in a first state when the coil is deenergized, and to bypass the output in a second state when the coil is energized.
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Abstract
Multilevel power converters, power cells and methods are presented for selectively bypassing a power stage of a multilevel inverter circuit, in which a single relay or contactor includes first and second normally closed output control contacts coupled between a given power cell switching circuit and the given power cell output, along with a normally open bypass contact coupled across the power stage output, with a local or central controller energizing the coil of the relay or contactor of a given cell to bypass that cell.
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Citations
18 Claims
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1. A power conversion system, comprising:
a plurality of power stages connected in series to form a multilevel inverter circuit for connection to a load, the power stages individually comprising; a DC link capacitor coupled between first and second DC link nodes of a DC link circuit, an output coupled with at least one other power stage in the multilevel inverter circuit, a switching circuit including a plurality of switching devices to provide an output voltage signal having an amplitude of one of at least two discrete levels, and a single relay or contactor including; a coil, a plurality of normally closed contacts operative in a first state to allow current to flow between the switching circuit and the output when the coil is deenergized, and operative in a second state to electrically isolate the switching circuit from the output when the coil is energized, and a normally open contact coupled across the output to allow normal operation of the output in a first state when the coil is deenergized, and to bypass the output in a second state when the coil is energized. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A power cell for use as a power stage in a multilevel inverter circuit, the power cell comprising:
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a DC link capacitor coupled between first and second DC link nodes of a DC link circuit; an output to be coupled with at least one other power stage in the multilevel inverter circuit; a switching circuit including a plurality of switching devices to provide an output voltage signal having an amplitude of one of at least two discrete levels; and a single relay or contactor including; a coil, a plurality of normally closed contacts operative in a first state to allow current to flow between the switching circuit and the output when the coil is deenergized, and operative in a second state to electrically isolate the switching circuit from the output when the coil is energized, and a normally open contact coupled across the output to allow normal operation of the output in a first state when the coil is deenergized, and to bypass the output in a second state when the coil is energized. - View Dependent Claims (10)
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11. A method for bypassing a power stage of a multilevel inverter circuit, the method comprising:
energizing a coil of a single relay or contactor to electrically isolate a switching circuit of the power stage from an output of the power stage, and to bypass the output of the power stage. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
Specification