Hybrid asymmetric cascaded three-phase inverter with low-order harmonics elimination control scheme

A hybrid asymmetric cascaded (HAC) three-phase inverter with low-order harmonics elimination control scheme was proposed. Asymmetric level, phase shifting and selective harmonic elimination pulse width modulation (SHEPWM) technology were used synthetically for low-order harmonics elimination. The HAC inverter was cascaded by diode neutral point clamped three-phase three-level module and single phase H bridge module. The control scheme between the inverter modules was asymmetric level and phase shift, meanwhile each inverter module was modulated by SHEPWM technology. The harmonics of output voltage, the power distribution between each module, regeneration problem and the realization of closed loop control were discussed. Compared with the traditional high power inverter scheme, the proposed scheme is characterized as concise topology without synthesis transformers, low switching frequency for all switches, small low-order harmonics component and THD, and small capability isolated transformers. The theoretical analysis was validated by the experiment results of a prototype.