Trapezoidal PWM Scheme for Cascaded Multilevel Inverter

This paper proposes a new PWM switching strategy for the cascaded multilevel inverter (CMI). This scheme employs multiple trapezoidal modulation waveforms with a single triangular carrier. The main advantage of this technique is the ability to generate PWM waveform generation in real time using very simple algorithm. Furthermore it also results in higher fundamental component magnitude. Although it is known that trapezoidal modulation suffers from the presence of low-order harmonics, it can be minimized by appropriately selecting the slope angle of the trapezoidal, alpha. This paper carried out the simulation on a five level CMI to justify the merits of the proposed scheme. A low cost FPGA based single phase five-level CMI test-rig is also constructed to verify the simulation results.