Coordinated Frequency Control of Flywheel Energy Storage and Diesel Generator in Amirkabir University of Technology (AUT) Microgrid

Diesel generator is considered as one of the most significant distributed generation units in microgrid which has commonly a governor system for frequency control. However, due to large time constant of its fuel injection system; its reaction in load variation is almost undesirable and sometimes causes noticeable frequency drop. In this study, a flywheel energy storage system (FESS) is introduced, studied and coordinated with a diesel generator emulator for frequency control in a real fabricated microgrid model. A new frequency control strategy is proposed for FESS based on the high-pass filtering. In this strategy, FESS compensates the high-frequency parts of the required power according to its speed, while the diesel generator provides other low-frequency parts. The simulation and experimental results demonstrate clearly the performance of the proposed strategy.

I. Introduction

In microgrids, the role of energy storage devices is quite crucial. Battery energy storage system (BESSs), supercapacitors and FESSs are well-known energy storage systems used in microgrids. Energy storage systems are usually employed to keep and satisfy the frequency control as well as power compensation. The energy capacity of FESS is typically more than supercapacitor, and unlike the BESS, FESS has infinite lifetime approximately. In addition, the FESS is faster and its power injection capacity is larger than the BESS.