An Algebraic Algorithm for Microcomputer-Based (Direct) Inverter Pulsewidth Modulation

A new method of direct inverter pulsewidth modulation (PWM) is described. In this technique the pulsewidths are determined by equating the incremental areas of the reference signal with the output pulse areas. This PWM method is compared to conventional methods, such as the natural PWM and the regular PWM, which are based on geometrical constructions. Harmonic analysis shows that the direct PWM method has less harmonic distortion that the other methods. Moreover, this technique is particularly suitable for microprocessor-based implementation since the pulsewidths are computable in real time from simple analytic expressions. It is shown that the output pulsewidths are directly proportional to the reference amplitude and inversely proportional to frequency. Therefore, constant volts/hertz operations and other modes of operation can be implemented very simply with a minimal storage requirement.