Trapezoidal PWM

Multilevel voltage source inverter (VSI) structured has been recognized to be very popular especially in high power application. It offers several advantages compared to the conventional two-level inverter, namely reduced switching losses and better harmonic performance. This work proposed a new switching strategy for a particular multilevel inverter, known as Cascaded Multilevel Inverter (CMI). The proposed scheme is based on classical unipolar PWM switching technique. Unlike other techniques proposed by other researchers, this method uses multiple trapezoidal modulation waveforms with a single triangular carrier. Trapezoid employment offers several advantages compared to Sinusoidal PWM (SPWM), namely easy real- time waveform generation and provides high fundamental magnitude output. However its harmonics performance is poor compared to SPWM.