Cascaded H-bridge multilevel inverter (CHBMI) is able to generate a staircase alternating current (AC) output voltage waveform with lower switching losses compared to two-level high switching frequency pulse-width modulation (PWM) inverter. However, the large number of active power semiconductor switches required in a conventional CHBMI may give rise to reliability issues. In addition, the switching angles applied in a conventional CHBMI are usually calculated using a set of non-linear transcendental equations, which is difficult to be solved and implemented in real-time. This thesis proposes a 15-level CHBMI with reduced active power semiconductor switches and real-time switchingangle calculation technique for wide modulation index operation. While the conventional CHBMI requires 28 switches to produce a 15-level output voltage waveform, the proposed CHBMI which employs a set of binary asymmetric H-bridges (HB) requires only 12 switches to produce the same output voltage waveform. A geometry based switching-angle calculation technique, which can be implemented in real-time, has been applied to the proposed CHBMI. The technique is able to calculate the switching angles for modulation index ranging from 0 to 1 and the lowest total harmonic distortion (THD) obtained is 5.32% at modulation index of 0.81. The performance of the proposed CHBMI has been evaluated via MATLAB/SIMULINK-SimCoupler-PSIM simulation and verified via 15-level CHBMI prototype. Both simulation and experimental results are in good agreement. Furthermore, experimental evaluation of the CHBMI prototype also shows that the system has a good real-time response to changing input modulation index.
