On re-examining symmetry of two-level selective harmonic elimination PWM: Novel formulations, solutions and performance evaluation

• New formulations for selective harmonic elimination pulse-width modulation (SHE-PWM) based on half-wave symmetries are proposed.
• By relaxing the symmetry restrictions in two-level SHE-PWM waveforms, the number of solutions that are acquired is significantly extended.
• A detailed evaluation of the harmonic performance of the solutions is presented.
• Solutions based on HW symmetries can improve the operation of SHE-PWM operated two-level converters.

This paper analyzes the half-wave symmetrical two-level SHE-PWM, proposes two formulations of the SHE-PWM waveform with multiple solutions and evaluates the solutions for different cases of eliminated harmonics. Previous work on SHE-PWM focused on algorithms for calculating the solutions and only considered the quarter-wave symmetry in the formulation. In this paper two different formulations to the problem are considered and solutions for a number of eliminated harmonics are presented. The different formulations increase the solution space of the problem and the number of acquired solutions. A comparison of the solutions in terms of harmonic performance is also presented. When compared with the quarter-wave symmetrical solutions, certain half-wave symmetrical solutions exhibit better performance and additional benefits can be acquired for two-level converters operated under SHE-PWM techniques. The HW symmetrical solutions are experimentally verified on a laboratory setup in order to confirm the validity of the solutions sets.