Direct interconnection technique applied to marine renewable generators, specifically airborne wind energy

This thesis explores application of the Direct Interconnection Technique (DIT) to Marine Renewable Energy (MRE) devices specifically Airborne Wind Energy (AWE). Interconnecting offshore generators and delivering generated power to the grid are critical challenges in dealing with offshore generation. In offshore renewable energy (wind) generation, (unlike conventional steam or gas plants which are dispatchable), the prime mover is non-dispatchable and generated power changes with wind conditions. By current design power converters are integrated with each offshore generator and after these power converters interconnected through the transmission system to grid onshore. Because of long distances from the shore, the repair and maintenance for offshore plant including power converters is very expensive and system reliability is most important as mobilising in response to faults offshore takes considerable time with considerable associated cost and missed opportunity / missed generation costs. These are motivating factors in developing AWE systems and in development of integration solutions for off shore farms. A comprehensive research work to design, develop and examine the use of DIT for offshore non-reversing pumping mode AWE systems has been performed, shown to be effective and improve the ruggedness of the offshore installation by relocating power converters to shore. A laboratory hardware setup has been developed to emulate a small AWE farm. The hardware setup is used to develop and examine a holistic DIT approach for AWE farms. For the first time, a series of experimental tests of a DIT algorithm for AWE systems has been carried out. The test results prove the theoretical expectations and the technical feasibility of the direct interconnection technique for non-reversing pumping mode AWE devices. Also, computer simulation models have been developed to research with more flexibility. The performance of the directly interconnected AWE systems under normal and fault conditions has been studied. The outcomes can be used in the design of a universal protection system. The quality of the power generated by the directly interconnected AWEs has been evaluated. Proper controllers have been developed to control the load balance and reactive power exchange of the directly interconnected AWE generators. By the implementation of the proposed active and reactive power controllers a notable improvement in power quality has been achieved.