Multilevel inverters are known for their reliability in producing high power ratings with low harmonic distortions by converting DC sources to AC output power. The demand for multiphase inverter systems is also increasing as higher phase systems produce a more reliable and higher output voltage. Therefore, a five-phase multilevel inverter is introduced for this research. However, harmonics distortions still occur in the system causing much unwanted problems with the power output. The Selective Harmonic Elimination Pulse Width Modulation (SHEPWM) switching technique is used for this research to eliminate the unwanted lower order harmonics and reduce Total Harmonic Distortion (THD) to maintain decent power output. Yet, solving a non-linear equation involving the SHEPWM switching technique also becomes a hurdle for this research. Unlike three-phase multilevel inverters, five-phase multilevel inverters are less well known and have less research content. The main focus of this research is the application of metaheuristic-based optimization algorithms into the multilevel inverter, such as Particle Swarm Optimization (PSO), Sine Cosine Algorithm (SCA), Whale Optimization Algorithm (WOA) and newly improved algorithm, Improved WOA (IWOA). Thus, the objective of this research is to design SHEPWM-based IWOA algorithms for the five phase seven-level, and nine-level inverters. Then, the IWOA will be compared with other algorithms for the SHEPWM switching technique performance. Therefore, SHEPWM-based algorithms will be designed for obtaining optimized switching angles for the multilevel inverter. Next, a complete simulation of the circuit will be developed and implemented for the five-phase power system. Finally, the simulation of a five-phase seven-level, and nine-level inverter system will be run using the obtained switching angle from the algorithms. The results obtained, such as the switching angles, the output waveform, the harmonics spectrum and the THD of the system were compared among the algorithms. The capabilities of IWOA to reduce THD and eliminate selected lower order harmonics are clearly shown in the results compared to PSO, SCA, and WOA. The IWOA successfully eliminates the selected lower order harmonics, which are 3rd and 7th for a seven-level inverter, and obtained the lowest THD results, 12.90% for output voltage and 3.67% for current output. In addition, the selected lower order harmonics, which are the 3rd, 7th, and 9th harmonics successfully eliminated for the nine-level inverter and obtain the lowest possible THD results, 8.63% for output voltage and 2.45% for current output. Moreover, the results also showed that in RL load circuit simulation, IWOA could produce a good sinusoidal current output waveform. In conclusion, the proposed IWOA is expected to be advantageous in developing a practical high performance five-phase cascaded multilevel inverter.
