Control of a flywheel energy storage system for rural applications using a Split-Pi DC-DC converter

This paper presents a control strategy of a flywheel system to maximize the energy available on solar panels using a Split-Pi DC-DC converter for rural applications. This new topology is mainly used in electric vehicles. The control system was designed, prototyped and tested on a flywheel system with an Axial Flux PM machine (AFPM). It showed an improvement in the solar power delivered to the electrical machine. This was seen when the solar was supplying 66% of the load, and the flywheel was supplying 33%. Speed and current limiting were also found to be effective at the different limits and this was observed at different speeds. As the solar or loads changed, the control system automatically adjusted the flywheel power flow in the electrical machine to maintain the correct bus voltage. The protection systems designed was found to be effective as the equipment was protected from damage caused by careless or incorrect operation. The new control system was a huge improvement on the old one where as soon as there was insufficient solar power; the system switched over to the flywheel alone supplying the load.