Ocean wave energy is one of the promising renewable energy sources which is undergoing fast development in recent years. Among various types of conversion systems for wave energy, floating offshore oscillating water column is an interesting topic. Since they are installed in oceans, reliability and maintenance are important issues. Electronic subassembly failures such as switch failures in converters are one of the typical converter failures for wave energy conversion systems.
A mathematical model for the floating oscillating water column is developed and a robust model predictive control during switch fault is designed to overcome the switch failures*. The proposed control system is capable of dealing with open switch faults in one or two switches of the same arm in any of the voltage source converters of this system, or even in both voltage source converters at the same time. Therefore, it is possible to obtain a continuous operation of a floating oscillating water column which can deliver energy to the grid even after certain types of faults in the voltage source converters, avoiding its grid disconnection and making the reparation less urgent. The simulation and experimental results have shown that the allowed peak power after the fault is around 50% of the pre-fault peak.
(*) Dionisio Ramirez, Marcos Blanco, Mohammad Ebrahim Zarei, and Mahima Gupta. "Robust control of a floating OWC WEC under open-switch fault condition in one or in both VSCs", IET Renewable Power Generation, Volume 14, no. 13, pp. 2538-2549, 2020. DOI: 10.1049/iet-rpg.2020.0203
More information: Mohammad Ebrahim Zarei, Postdoctoral researcher, Electrical system Unit, mohammad.zarei@imdea.org
 proposed control for the machine side converter of wave energy generation system. |
 proposed control for the grid side converter of wave energy generation system. |
Output power of the wave energy generation system before and after fault (pre-fault=blue line, during switch fault= red line)