Modular input-parallel-output-series DC/DC converter control with fault detection and redundancy

Large offshore wind farms will require an extensive sub-sea power network to provide internal interconnection. Present solutions are based around conventional medium-voltage AC architectures. This paper proposes an alternative DC collection network based around modular DC/DC converters with input-parallel-output-series (IPOS) connection. Small-signal analysis of the converter is presented, to assist in control scheme development for the converter input and output stages. A Lyapunov controller is embedded within the conventional output voltage sharing control loop. A master-slave control scheme is proposed to ensure power sharing under a range of operating conditions, and provides fault-tolerant operation since the status of 'master' can be reallocated in the event that the present 'master' module fails