Selective Harmonic Elimination PWM For a Cascaded Multi-level Inverter

This paper deals with the selective harmonic elimination pulse width modulation (SHE-PWM) technique. This technique is used for the elimination of selected dominant low order harmonics in the multi-level inverter output voltage. The presence of these harmonics is the essential drawback of such kind of inverters; especially when it is used for the control of different AC drivers. The SHE-PWM is based on the minimization of a constrained nonlinear objective function whose variables are the switching angles used for multi-level inverter control. The solution of this optimization problem can be achieved using different metaheuristic optimization algorithms. An approach of SHE-PWM based on Particle Swarm Optimization (PSO) algorithm is proposed in this paper. Different patterns of optimal switching angles shown in a previous work, which are based on groebner bases and symmetric polynomials theory (GBSP), are improved in this paper using PSO. The improved earlier patterns are compared with the proposed approach. The obtained experimental and simulation results are aimed to verify the efficiency and the capability of the proposed approach in improving the Total Harmonic Distortion (THD) while eliminating the desired low frequency harmonics.