Microprocessor-based sinusoidally sampled PWM technique for neutral-point clamped inverter

A detailed description is given of a novel sinusoidally sampled, area-computation, pulse width-modulated (PWM) technique for a neutral-point clamped PWM inverter using a high-speed microprocessor. A historical review of PWM techniques is included. This technique is compared with the uniform-sampled, area-computation technique. It is shown that in the case of motor load, the presented method can be used at a higher frequency of operation, whereas at a lower frequency of operation, a uniform-area sampling method can be used. The sinusoidally sampled PWM technique can also be used for uninterruptible power supply systems and for a three-phase four-wire system, where it has an edge over the uniform-area sampling technique. In these applications, frequency is kept constant. The output voltage change due to load variation can be compensated by changing the depth of modulation. >