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The emergence of wide-bandgap devices, e.g. silicon carbide (SiC), has the potential to enable very high-density power converter design with high-switching frequency operation capability. A comprehensive design tool with a holistic design approach is critical to maximise the overall system power density, e.g by identifying the optimal switching frequency. This paper presents a system level design tool that optimises the power density (volume or mass) of a 3-phase, 2-level DC-AC converter. The design tool optimises the selection of the devices, heatsink and passive components (including the design of the line, EMI and DC-link filters) to maximise the power density. The structure of the optimisation algorithm has been organised to reduce the number of potential design combinations by over 99%, and thus produces fast simulation times. The design tool predicts that when SiC devices are used instead of Si ones, the power density is increased by 159.4%. A 5 kW, 600 V DC-link, 3-phase, 2level DC-AC converter was experimentally evaluated in order to confirm the accuracy of the design tool.

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An investigation is described into the optimization of multi-phase, high power, bi-directional DC-DC interleaved converters suitable for Electric Vehicle (EV) applications. Two dual-interleaved topologies were considered initially for the optimization, the main difference being the magnetic devices: either discrete inductors (DI) or an Interphase Transformer (IPT). The comparison used a comprehensive multi-objective design optimization procedure for an 80 kW case study. High performance inductors comprising a split-core structure and dual-foil windings to reduce losses, and a 180 C core, enabled the DI to be competitive with IPT in terms of power density and efficiency. The optimized designs are validated experimentally with an 80 kW bi-directional SiC DC-DC converter, achieving a power density of 31.4 kW/L and specific power of 15.7 kW/kg. The study is then extended to 100-kW three and four-phase interleaved topologies.

Model predictive control (MPC) schemes have become popular in the field of power electronics due to their intuitive formulation, flexibility, and ease of implementation. Typically, these schemes have been implemented with the prediction horizon limited to one time-step, and extension of the prediction horizon over multiple time-steps remains an ongoing area of research. In this paper, a variant of the MPC strategy is proposed wherein the slope of the output trajectories is used to emulate long prediction horizons. Each of the outputs, e.g. current, voltage, torque, or flux, is regulated within a set of symmetrical bounds. When switching is necessitated due to collision with a bound, the switching state that yields the set of output trajectories with the minimum slope, relative to the reference trajectory, is applied to the converter. The key benefit of this approach is its ability to achieve low switching frequencies with a minimal level of computational burden. The feasibility of the scheme, which can be adapted easily to different case studies, is demonstrated through simulations of both a Medium-Voltage (MV) induction machine drive and a grid-connected converter. Experimental results, which are presented for a 1.68 kVA prototype grid-connected Neutral-Point-Clamped (NPC) converter, further demonstrate the practical viability of the proposed strategy. Index Terms-Current control, model predictive control, neutral point clamped converter, slope control.

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