A Carrier-comparison-based Implementation Strategy of A 24-sector-based SVPWM Technique of Asymmetrical Six-phase Machine in Overmodulation Region

Abstract

An asymmetrical six-phase machine (ASPM) with two isolated neutral points is analyzed in two orthogonal planes-one of these planes is associated with electromagnetic energy transfer. The energy-transferring plane of ASPM has two regions-linear and overmodulation (OVM). Unlike the linear region, the average voltage injected in the non-energy transferring plane of the OVM region is non-zero. The efficacy of carrier-based implementation of an equivalent space-vector PWM (SVPWM) technique to reduce the computational burden is well-known in three-phase inverter literature. Although carrier-based implementations of popular SVPWM techniques of ASPM are researched for the linear region, such carrier-based implementation doesn’t exist for the OVM region. Moreover, a direct extension of the carrier-based strategy in the linear region to the OVM region isn’t possible because it requires the calculation of non-zero voltages in the non-energy transferring plane. This paper presents a carrier-based implementation of one of the SVPWM techniques in the OVM region, resulting in minimum RMS harmonic voltage. The proposed technique is a natural extension of an important known PWM technique applied in the linear region. The proposed algorithm generalizes the duty signals in terms of maximum, middle, and minimum of three intermediate signals. These duty signals are then compared with two carrier signals to generate the required gating pulses. The proposed algorithm is validated through simulation and experiment on a hardware prototype at a maximum power of 4.5 kW.