Abstract-Using the vector space decomposition (VSD) approach, the currents in a multiphase machine with distributed winding can be decoupled into the flux and torque producing α-β components, and the loss-producing x-y and zero-sequence components. While the control of α-β currents is crucial for flux and torque regulation, control of x-y currents is important for machine/converter asymmetry and dead-time effect compensation. In this paper, an attempt is made to provide a physically meaningful insight into current control of a six-phase machine, by showing that the fictitious x-y currents can be physically interpreted as the circulating currents between the two three-phase windings. Using this interpretation, the characteristics of x-y currents due to the machine/converter asymmetry can be analysed. The use of different types of x-y current controllers for asymmetry compensation and suppression of dead time induced harmonics is then discussed. Experimental results are provided throughout the paper, to underpin the theoretical considerations, using tests on a prototype asymmetrical six-phase induction machine.
Abstract This paper discusses the operation of a multiphase system, aimed at both variable-speed drive and generating (e.g. wind energy) applications, using back-to-back converter structure with dual three-phase machine-side converters. In the studied topology, an asymmetrical six-phase induction machine is controlled using two three-phase two-level voltage source converters (VSCs) connected in series to form a cascaded dclink. The suggested configuration is analysed and a method for dc-link midpoint voltage balancing is developed. Voltage balancing is based on the use of additional degrees of freedom that exist in multiphase machines and represents an entirely new utilisation of these degrees. Validity of the topology and its control is verified by simulation and experimental results on a laboratory-scale prototype, thus proving that it is possible to achieve satisfactory dc-link voltage control under various operating scenarios.
In this paper, a comparative analysis has been presented on various topologies of isolated and non-isolated DC-DC converters. Here, the major focus remains on transformer-less (TL) DC-DC converters, based on the conventional basic boost converter. In addition, to attain high voltage gain, a classification of non-isolated converters based on extendable and non-extendable design has been presented. For comparative and theoretical analysis, the parameters chosen are the number of components utilized by each converter topology, high voltage gain offered, voltage stresses on each component involved and the efficiency of the high gain topologies. For the converters under discussion, operation under ideal and non-ideal conditions has also been highlighted. Based on this study, authors present a guide for the reader to identify various high voltage gain topologies for photovoltaic (PV) systems.
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