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

摘要

Large offshore wind farms require extensive sub-sea cables within the collection network. Present solutions are based around medium-voltage AC collection networks. Recent studies have highlighted the potential benefits of DC collection networks. However, achieving DC/DC conversion at the required voltage and power levels presents a significant challenge for wind-turbine power electronics. This study proposes an alternative DC collection network based around a modular DC/DC converter with input-parallel output-series connection. This modular topology can overcome the limitations imposed by semiconductor voltage ratings and provides fault-tolerant operation. Small-signal analysis of the converter is presented to be used to facilitate controller design for the converter input and output stages. A new master–slave control scheme and distributed voltage sharing controllers are proposed that ensure power sharing under all operating conditions, including during failure of a master module. This control scheme achieves fault-tolerant operation by allowing the status of master module to be reallocated to any healthy module. The proposed control scheme is validated using simulation and experimentation, considering active power sharing between modules with parameter mismatch.