This paper proposes a generalised commutation strategy suitable for matrix-based isolated AC/AC conversion stages in Solid State Transformers for use whenever there is nonnegligible leakage inductance in the isolation transformer. The standard 4-step commutation used in matrix converters can no longer be applied when transformer leakage inductance is present, as overrated switching devices or dissipative snubbers would be necessary, reducing the attractiveness of the topologies that include matrix-based isolated AC/AC stages. A case study of a single-phase AC/AC converter has been investigated in detail to demonstrate the application of the proposed commutation method to a topology that has recently been identified as the potential building block for future multi-modular AC/AC converters for grid applications. The proposed leakage-inductance-tolerant commutation strategy is based on the definition of a current decoupling phase in the commutation sequence and only needs suitable timing of the commutation steps, without high bandwidth voltage or current measurements. Matching simulations and experimental results from a 3kW laboratory scale prototype are presented to support the effectiveness of the proposed strategy.

This paper discusses the analysis, design and experimental validation of a Modular Isolated Matrix Converter (MIMC), including modulation, commutation and control. The MIMC topology is a single-stage high power density AC/AC converter which is attractive for traction applications and spacerestricted LV or MV future distribution networks. The topology under study utilises bi-directional switches based dual-activebridge cells as basic building blocks. A single-cell would have limited practical application as the output frequency is locked to the input one. On the contrary, the repetition of single cells proposed in the MIMC extending the matrix converter concept, achieves variable frequency operation while also providing a modular structure. However, the presence of Medium Frequency (MF) transformers in each cell poses additional challenges for modulation and safe-commutation that are discussed and solved in the paper. Experimental results from a proof-of-concept 6kW laboratory scale prototype validate the practical feasibility and the operation of the MIMC.

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Abstract-In recent years, power electronics has evolved dramatically due to their importance in power extracted management from renewable sources. In this paper an overview of grid interconnection systems with galvanic isolation is presented. The most common used topologies from AC/AC, AC/DC, DC/AC and AC/AC conversion are analyzed y summarized in order to provide a good understanding of the existing technologies.