An investigation of MMC based DC/DC converter for HVDC grids

The interconnection of multiple oshore renewable energy sources to form a network and maximise their availability requires a method for controlling the transportation of bulk electrical energy. For the distances considered, and as a result of the capacitive nature of HVAC cables, HVDC is the most likely technology for meeting these bulk transport requirements. This research investigates the development of an MMC based Dual Active Bridge (DAB) for interfacing two different parts of a HVDC network. Computational tools are developed in order to design and evaluate such a power electronics structure as well as to support the design process of the transformer required for scaling and matching voltages between the two parts of the network. Linear control techniques are applied to control the converter to operate at the required average capacitor voltage level and power transmission.Simulation results, supported by experimental data from a low voltage MMC prototype are presented to validate the approaches