Particle swarm optimisation-based modified SHE method for cascaded H-bridge multilevel inverters

Low-frequency switching strategies are considered as an effective way of achieving efficient performance in multilevel inverters. Selective harmonic elimination (SHE) is a modulation technique of this category which gives a superior outcome suppressing low-order detrimental harmonics. Limited number of decision variables offered by SHE in the corresponding non-linear equations hinders obtaining high-quality waveforms. Current research is targeted on two distinct objectives for cascaded H-bridge inverters. First objective is to obtain a high-quality output signal. The second one is accomplishing a realistic solution with compromised voltage quality where a broad operating range becomes mathematically challenging. These aims are achievable by deploying additional degree of freedom in the equation set. In other words, the introduction of floating voltage levels contributes to effectively doubling the number of variables. The enhancement of output waveforms is presented through several illustrations and comparisons. Subsequent laboratory implementation validates the proposal and confirms its feasibility.