Low harmonic diode clamped converter/inverter

A method of operating a low harmonic converter/inverter comprising:

• selectively connecting a sinusoidal input voltage to different ones of a plurality of nodes during different portions of an input voltage cycle, wherein a plurality of series-connected electrical energy storage devices are coupled between the nodes;
• and
• selectively connecting an output to different ones of the plurality of nodes during different portions of an output voltage cycle to produce a stepped sinusoidal output voltage,
• wherein selected nodes are connected to the input voltage during the portions of the input voltage cycle by a first network of switching devices receiving the input voltage and coupled to the nodes, and selected nodes are connected to the output during the portions of the output voltage cycle by a second network of switching devices coupled to the output and the nodes, and
• wherein the first and second networks of switching devices each comprise:
• a set of series-connected switching devices between end nodes within the plurality of nodes and
• one or more switching devices connected between a node within the plurality of nodes and a junction between two of the series-connected switching devices.

A method of controlling a converter/inverter comprising:

• selecting switching angles within input and output voltage cycles for switching signals controlling switching devices within first and second networks of switching devices,
• the first network of switching devices selectively connecting a sinusoidal input voltage to different ones of a plurality of nodes during different portions of the input voltage cycle, wherein a plurality of series-connected electrical energy storage devices are coupled between the nodes, and
• the second network of switching devices selectively connecting an output to different ones of the plurality of nodes during different portions of an output voltage cycle to produce a stepped sinusoidal output voltages,
• wherein the first and second networks of switching devices each comprise:
• a set of series-connected switching devices between end nodes within the plurality of nodes and
• one or more switching devices connected between a node within the plurality of nodes and a junction between two of the series-connected switching devices.

A system for controlling a converter/inverter including a plurality of series-connected electrical energy storage devices coupled between a plurality of nodes, a first network of switching devices selectively connecting a sinusoidal input voltage to different ones of the plurality of nodes during different portions of an input voltage cycle, a second network of switching devices selectively connecting an output to different ones of the plurality of nodes during different portions of an output voltage cycle to produce a stepped sinusoidal output voltage, the system comprising:

• a controller that, when operable, receives a desired speed of a load driven at least in part by the output voltage and selects, from a plurality of alternative sets of switching angles based upon the desired speed, switching angles within the input and output voltage cycles at which switching devices within the first and second networks are switched to produce the output voltage,
• wherein the first and second networks of switching devices each comprise:
• a set of series-connected switching devices between end nodes within the plurality of nodes and
• one or more switching devices connected between a node within the plurality of nodes and a junction between two of the series-connected switching devices.