Subsea power transmission and distribution has been widely accepted by the offshore oil and gas industry for boosting the production and reducing the cost. To support various processing loads such as pumps and compressors, the subsea power demand is increasing rapidly from kW to tens of MWs and with a step-out distance of few kilometers to hundreds of kilometers. The reactive power burden on the system due to the charging currents limit the conventional ac power transmission to smaller step-out distances. At PEMSES, we study various subsea power system architectures and propose to use HVDC based subsea transmission architectures. We also propose a novel hybrid circuit breaker for HVDC systems to reduce the breaking time and the losses. This project also investigates various variable frequency drives (VFDs) suitable for driving the electrical submersible pumps (ESP) for subsea applications.