Random hysteresis PWM inverter with robust spectrum shaping

Hysteresis current-controlled pulsewidth modulation (PWM) scheme is simple and robust in switching control, but it is subject to not constant switchin g frequency. However, since its harmonic spectrum is not randomly distribut ed like those yielded by the random PWM (RPWM) scheme, the annoying harmoni c effects still exist. A random switching control strategy is proposed here to let the harmonic spectrum of the hysteresis current-controlled PWM inve rter be randomly distributed, First, the effect of varying band on the harm onic distribution characteristic of a hysteresis current-controlled PWM sch eme is analyzed. Then a random hysteresis PWM scheme and its quantitative d esign procedure are proposed. Finally, a robust spectrum shaping technique is devised such that the desired harmonic distribution pattern can be achie ved. In the resulting frequency spectrum, the magnitudes of lower frequency harmonics are shaped and reduced. Hence the inverter output with better ha rmonic attribute is obtained. Validity of the proposed random hysteresis PW M scheme is verified by some simulated and measured results.