Sinusoidal Input Current and Average Speed Control of a Single-Phase Supplied Three-Phase Inverter Drive Without Electrolytic Capacitor

Single-phase supplied variable speed drives are mostly realized as two-stage systems comprising a single-phase PFC rectifier and a three-phase inverter stage. The intrinsic power pulsation of single-phase converters with twice the grid frequency is typically buffered by a bulky electrolytic DC-link capacitor, which is a major drawback concerning converter volume, costs and especially lifetime. Therefore, this paper presents a novel and simple implementation of a Machine-integrated Power Pulsation Buffer (MPPB) concept, which utilizes the inertia of the rotating mass as an energy storage to cover a part or the full input power pulsation. This allows to either reduce or even eliminate the electrolytic capacitor resulting in a smaller and cheaper converter system with increased lifetime. The proposed MPPB control concept is fully implemented in software, which means that only simple couplings are added to the control structure. Since the hardware remains unaffected, this concept can also be easily applied to already existing drive systems. In addition to the derivation of the control scheme, the proper operation of the MPPB is verified for steady-state and transient operation by circuit simulations.