A decoupled energy control strategy for the Series Bridge Converter (SBC) for HVDC applications

The Series Bridge Converter (SBC) is a new modular multilevel topology for HVDC, featuring a highly compact footprint that makes it attractive for offshore and city infeed applications. Size reduction is achieved with a lower number of cells with smaller cell capacitors compared to other state of art topologies, thus reducing the total energy storage. As a drawback, the SBC has a more challenging control. In particular, care must be taken to guarantee consistent and predictable dynamic response of the energy controllers. This paper proposes a simple energy control scheme for the SBC, based on a coordinate transformation, that guarantees independent control of the energy stored in each arm, and simplifies the design and implementation of the energy loops. The effectiveness of the controllers has been validated with a Matlab/Plecs switching simulation model.