Multi-level inverter

A method for operating an inverter comprising an input configured to be coupled to a DC source, an output, a plurality of DC busses, a mid-point bus coupled to the input and to the plurality of DC busses, an LC filter coupled to the output, a common node coupled to the LC filter, a plurality of switches coupled to the plurality of DC busses and the common node, and a bidirectional switch coupled between the mid-point bus and the common node, the method comprising:

• receiving, at the input, input DC power from a DC source;
• operating the plurality of switches and the bidirectional switch in a first mode of operation to generate a voltage at the common node at a first positive DC voltage level by modulating at least one switch of the plurality switches and operating the bidirectional switch in a static state;
• operating the plurality of switches and the bidirectional switch in a second mode of operation to generate the voltage at the common node at a second positive DC voltage level by modulating at least one switch of the plurality of switches and operating the bidirectional switch in a static state;
• operating the plurality of switches and the bidirectional switch in a third mode of operation to generate the voltage at the common node at a first negative DC voltage level by modulating at least one switch of the plurality of switches and operating the bidirectional switch in a static state;
• operating the plurality of switches and the bidirectional switch in a fourth mode of operation to generate the voltage at the common node at a second negative DC voltage level by modulating at least one switch of the plurality of switches and operating the bidirectional switch in a static state;
• and
• generating, with the LC filter, an output AC voltage waveform at the output derived from the voltage at the common node during the first, second, third, and fourth modes of operation.

An inverter comprising:

• an input configured to be coupled to a DC source and to receive input DC power from the DC source;
• an output configured to be coupled to a load and to provide output AC power to the load;
• a plurality of DC busses coupled to the input and configured to receive the input DC power from the DC source;
• a mid-point bus coupled to the input and to the plurality of DC busses;
• an LC filter coupled to the output;
• a common node coupled to the LC filter;
• a plurality of switches coupled to the plurality of DC busses and the common node;
• and
• means for statically coupling the mid-point bus to the common node and modulating at least one switch of the plurality of switches to switch a voltage at the common node to a first positive DC voltage level during a first mode of operation, a second positive DC voltage level during a second mode of operation, a first negative DC voltage level during a third mode of operation, and a second negative DC voltage level during a fourth mode of operation, and for providing an output AC voltage waveform to the output derived from the different voltage levels.