Single-phase multi-level asymmetric inverter with AC-bypass and asymmetric modulation strategy
A multi-level inverter includes a coupling to a DC power source and a coupling to an AC power source, a plurality of capacitors arranged to create a set of nodes, and a plurality of switches located between the capacitors and the AC power source. Switches are configured to create an AC bypass in which the capacitors coupled to the DC power source may be isolated from the AC power source. The AC bypass is utilized as one of the switching states in a switching sequence that provides enhanced performance including but not limited to reduced electromagnetic interference and ripple.
1. A multi-level inverter, comprising:
a DC power coupling with a DC voltage;
a plurality of DC link capacitors arranged to create a set of nodes comprising a positive node, a center node, and a negative node;
a first arrangement of switches, wherein a first side of said first arrangement of switches is coupled to said set of nodes, and a second side of said first arrangement of switches is coupled to a first AC terminal and a second arrangement of switches;
wherein a first side of said second arrangement of switches is coupled to said first AC terminal and said first arrangement of switches, and a second side of said second arrangement of switches is coupled to a second AC terminal;
wherein said first arrangement of switches and said second arrangement of switches are configured to produce five levels of voltage between said first AC terminal and said second AC terminal when operated according to a predetermined switching sequence; and
wherein said predetermined switching sequence includes a zero-output switching configuration that electrically isolates said first AC terminal and said second AC terminal from said set of nodes.
2. The multi-level inverter of claim 1 wherein said predetermined switching sequence includes a first commuting frequency in the range of 1 kHz to 100 kHz.
3. The multi-level inverter of claim 2 wherein said first commuting frequency is 20 kHz.
4. The multi-level inverter of claim 2 wherein said predetermined switching sequence includes a second commuting frequency in the range of 1 Hz to 100 Hz.
5. The multi-level inverter of claim 1 wherein said five levels of voltage approximate the full positive DC voltage, the full positive DC voltage divided by two, zero, the negative DC voltage divided by two, and the full negative DC voltage.
6. The multi-level inverter of claim 4 wherein said five levels of voltage approximate the full positive DC voltage, the full positive DC voltage divided by two, zero, the negative DC voltage divided by two, and the full negative DC voltage.
7. A five-level inverter, comprising:
a DC power coupling with a DC voltage;
an AC power coupling;
two DC link capacitors arranged to create a set of nodes;
a plurality of switches located between said set of nodes and said AC power coupling; and
a predetermined switching sequence that generates five voltage output levels;
wherein said predetermined switching sequence includes a zero-output switching configuration in which said set of nodes is electrically isolated from said AC power coupling.
8. The multi-level inverter of claim 7 wherein said predetermined switching sequence includes a first commuting frequency in the range of 1 kHz to 100 kHz.
9. The multi-level inverter of claim 8 wherein said predetermined switching sequence includes a second commuting frequency in the range of 1 Hz to 100 Hz.
10. The multi-level inverter of claim 7 wherein said five voltage output levels approximate the full positive DC voltage, the full positive DC voltage divided by two, zero, the negative DC voltage divided by two, and the full negative DC voltage.
11. The multi-level inverter of claim 9 wherein said five voltage output levels approximate the full positive DC voltage, the full positive DC voltage divided by two, zero, the negative DC voltage divided by two, and the full negative DC voltage.
12. A multi-level inverter, comprising:
a DC power coupling with a DC voltage;
a plurality of DC link capacitors arranged to create a set of nodes;
a first arrangement of switches, wherein a first side of said first arrangement of switches is coupled to said set of nodes and a second side of said first arrangement of switches is coupled to a first AC terminal and a second arrangement of switches;
wherein a first side of said second arrangement of switches is coupled to said first AC terminal and said first arrangement of switches, and a second side of said second arrangement of switches is coupled to a second AC terminal;
wherein said first arrangement of switches and said second arrangement of switches are configured to produce greater than five levels of voltage between said first AC terminal and said second AC terminal when operated according to a predetermined switching sequence; and
wherein said predetermined switching sequence includes a zero-output switching configuration that electrically isolates said first AC terminal and said second AC terminal from said set of nodes.
13. The multi-level inverter of claim 12 wherein said predetermined switching sequence includes a first commuting frequency in the range of 1 kHz to 100 kHz.
14. The multi-level inverter of claim 13 wherein said first commuting frequency is 20 kHz.
15. The multi-level inverter of claim 13 wherein said predetermined switching sequence includes a second commuting frequency in the range of 1 Hz to 100 Hz.
16. The multi-level inverter of claim 12 wherein said plurality of DC link capacitors comprises exactly three DC link capacitors.
17. The multi-level inverter of claim 12 wherein said plurality of DC link capacitors comprises exactly four DC link capacitors.
18. The multi-level inverter of claim 1 , wherein said zero-output switching configuration allows for current to flow through exactly two switches.
19. The five-level inverter of claim 7 , wherein said zero-output switching configuration allows for current to flow through exactly two switches.
20. The multi-level inverter of claim 12 , wherein said zero-output switching configuration allows for current to flow through exactly two switches.