Method and apparatus for controlling voltage linearity of voltage source inverters

A method of modifying a signal controlling a voltage source inverter, the method comprising the steps of:

• determining a duty cycle for a phase-leg of the signal;
• clamping the signal at a first potential when the duty cycle is between a first duty cycle limit (dmax) and a second duty cycle limit (dclip) indicating a distortion range when the duty cycle reaches a first phase angle (α1) determined as a function of the modulation index (Mi);
• clamping the signal at a second potential when the duty cycle≧the second duty cycle limit (dclip);
• clamping the signal at a third potential when the duty cycle is between a third duty cycle limit (dmin) and a fourth duty cycle limit indicating the distortion range;
• and
• clamping the signal at a fourth potential when the duty cycle≦the fourth duty cycle limit.

A voltage source inverter comprising:

• a controller configured to:
• receive a first signal having a duty cycle;
• and
• limit said duty cycle at a first duty cycle limit (dmax)when a modulation index (Mi) is greater than a minimum modulation index (Mi—min), said minimum modulation index (Mi—min) indicating a distortion range, wherein the duty cycle of the first signal is limited when it reaches a first phase angle(α1) determined as a function of the modulation index (Mi);
• and
• a switch network having a first input coupled to said controller and having a second input configured to couple to a reference potential (Vdc), said switch network configured to:
• convert said reference potential (Vdc) to a voltage based on said first signal;
• and
• transmit a second signal having said voltage.