Microcontroller-based Walsh function PWM modulation with harmonic injection technique

An improved pulse width modulation (PWM) method for three-phase inverters using the Walsh function harmonic elimination method with harmonic injection technique is presented, together with a noniterative algorithm that produces a set of linear equations that relates switching angles with the output phase voltage fundamental. The approach used gives a set of solutions with a near-linear trajectory which can be approximated by straight-line curve fitting. Thus, on-line control of fundamental amplitude and frequency is possible with a microcontroller-based implementation. The novel use of harmonic injection technique maximizes the output line voltage fundamental. The theoretical predictions are confirmed by computer simulation and DSC-based hardware implementation.