Current harmonic compensation in symmetrical multiphase machines by resonant controllers in synchronous reference frames—Part 2: Computational load

Abstract

It has been previously suggested to use multiple reference frame (MRF) structures, based on proportional-integral controllers in synchronous reference frames (SRFs), to suppress current harmonics caused by nonlinearities in multiphase drives. However, the rotational transformations are computationally demanding. In Part 1, the three-phase strategy based on resonant controllers (RCs) implemented in an SRF has been extended to any phase number. Nevertheless, while the computational burden of MRF and multiple RC (MRC) schemes has been assessed for three-phase systems in previous papers, it is yet to be studied for other numbers of phases. Part 2 analyzes the computational load of the MRC and MRF strategies as a function of the phase number and of the highest harmonic order to be compensated. It is proved that the former provides a resource saving with respect to the latter that decreases with the phase number and increases with the highest harmonic order under consideration. It is also concluded that the MRC strategy is particularly preferable in machines with even phase number (e.g., a multiple of six).