Robust control of a floating OWC WEC under open-switch fault condition in one or in both VSCs

Abstract

The operation and maintenance activity of off-shore wind turbines (WTs) increases the cost of the generated energy. Although significant efforts have been made to improve the reliability of the mechanical subassemblies, electrical and electronic subassemblies fail more frequently, causing undesirable downtimes and loss of revenues. Since off-shore WTs and wave energy converters (WECs) share the electrical and electronic subassemblies, the reliability of WECs is expected to be affected by the same causes. This study presents a robust model predictive control for a WEC consisting of an oscillating water column (OWC) installed in a point absorber. The control system is capable of dealing with open switch faults in one or two insulated-gate bipolar transistors of the same arm in any of the voltage source converters (VSCs), or even in both VSCs at the same time. The system allows the OWC WEC to generate energy, although under certain restrictions, thereby reducing the urgency of repair and loss of revenues. The performance of the proposed approach is tested for several cases of open switch faults, experimentally in the laboratory using an OWC WEC emulator.