A unified SVPWM realization for minimizing circulating currents of dual three phase machines

Abstract

Space-vector PWM (SVPWM) gained attention, as a voltage synthesis technique for asymmetrical dual three phase machines (ADTMs); due to its ability to minimize the harmonic content of the output and minimize the switching losses through proper selection of the switching vectors. It has been studied extensively for ADTMs mainly for induction machines with isolated neutrals (2N), such that the inverter is assumed to be the only source capable of inducing harmonics within the stator currents. Thus, by setting the xy subspace voltages to zero, the harmonic content is minimized. However, for dual three phase-permanent magnet synchronous machines (DT-PMSM), the presence of non-sinusoidal rotor flux invokes significant harmonics, mandating non-zero references for the xy plane to ensure proper compensation. This paper invokes the employment of non-zero harmonic references within the SVPWM calculation for the 2N connection, as well as laying out the fundamentals for the single neutral (1N) connection, which is more reliable from fault-tolerance point of view. Also, a simple digital realization is presented, suitable for the 12-, 24-sector SVPWM methods, both continuous and discontinuous modulations. The theoretical findings are corroborated with a 4.4 kW DT-PMSM, demonstrating significant improvement in the total harmonic distortion (THD) of the stator currents.