Control method for flywheel array energy storage system in energy harvesting from electric railway

Flywheel energy storage system (FESS) with a single flywheel unit could not achieve the required power level of commercial electric railway. By connecting the standard flywheel modules in parallel, a flywheel array energy storage system (FAESS) is built up for energy harvesting from the electric railway´s regenerative brake. A two-level direct power control method for FAESS which consists of power allocation criterion and energy harvesting control scheme is proposed in this paper. The first level is an equal incremental rate principle based power allocation criterion, which is responsible for generating power control command for each flywheel module in the FAESS. The second level is the energy harvesting control scheme, which is in charge of controlling the AC/DC converter of a flywheel module to harvest energy from locomotive braking and make it available during subsequent acceleration cycles of locomotive. The effectiveness of the power allocation criterion is verified through detailed example analysis and simulation that refer to the practical parameters of a 100kW FAESS prototype.