Medium Frequency SST Based Multiport Energy Routers for Subsea – Renewable Interconnection

In order to supply reliable power to the subsea loads at high system efficiency and low emissions, there is a growing interest in employing offshore renewable resources close to the point of use. However, such a system has predominantly stayed in the conceptual stage so far. Hence, there is compelling need to develop technical methodologies for interconnecting multiple megawatt-scale systems with offshore loads. This paper proposes a Multiport Energy Router (MER) based on the Medium Frequency (MF) Solid-State Transformer (SST) that integrates renewable energy sources (RES) and Energy Storage Systems (ESS) to supply clean energy for subsea loads. The MER forms a three-port network, where HVDC Wind Turbine Generator (WTG) power system and MVDC ESS are interfaced with subsea loads. The MER is realized by series-parallel combination of Triple Active Bridge (TAB) converters. The converters are critical to enhance the power density, reliability, and efficiency of the proposed system. Moreover, the paper describes a control strategy for the proposed MER, which addresses the DC-link voltage unbalance issue for each of the cascaded TAB converters. The simulation and the Hardware-in-the-Loop (HIL) results based on Typhoon-HIL system are presented to verify the proposed converter operation and the control strategy.