Recently, medium voltage SiC devices have been developed which can be used for grid tie applications at medium voltage. Two such devices -15 kV SiC IGBT and 10 kV SiC MOSFET have opened up the possibility of looking into different converter topologies for medium voltage distribution grid interface. These can be used in medium voltage drives, active filter applications or as the active front end converter for Solid State Transformers (SST). Transformer-less Intelligent Power Substation (TIPS) is one such application for these devices. TIPS is proposed as a 3-phase SST interconnecting 13.8 kV distribution grid with 480 V utility grid. The Front End Converter (FEC) of TIPS is made up of 15 kV SiC IGBTs.This paper focuses on the advantages, design considerations and challenges associated with the operation of converters using these devices keeping TIPS as the topology of reference.
Basic power topology for a Solid State Transformer (SST) with new 15kV SiC IGBT devices is discussed. It is difficult to build high efficient, light weight, magnetically isolated solid state transformer for high voltage (13.8 kV) grid connectivity with existing Si 6.5kV rated IGBTs and diodes. Existing state of the art high voltage (6.5kV), high speed power devices (IGBT) cause considerable amount of loss (switching and conduction loss). With the advent of SiC devices these limitations are largely mitigated and this provides the motivation for new power topologies. The targeted efficiency of the proposed SST is 98%.Simulation results for a 1 MVA proposed SST topology is presented. I.
In this paper, DTC (Direct Torque Control) algorithms for Split-phase Induction Machine (SPIM) are established. SPIM has two sets of three-phase stator windings, with a shift of thirty electrical degrees between them. The significant contributions of the present work are: a) Two new methods of DTC technique for SPIM are developed. They are called as Resultant Flux Control Method and Individual Flux Control Method. b) Advantages and disadvantages of both the methods are discussed. High torque ripple is a disadvantage for three-phase DTC. It is found that torque ripple in SPIM could be significantly reduced without increasing the switching frequency.
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