Cooperative Control of Flywheel Energy Storage System and Diesel Generator for Frequency Regulation of Microgrids Using Digital FIR Filters

In islanded microgrids (MGs), due to the low level of inertia, it is particularly important to establish a balance between the power generation and consumption at any moment. Any power imbalance in an islanded MG can increase or decrease the frequency and even cause instability. This problem has led to ever-increasing attention to energy storage systems (ESSs) to control the frequency and voltage of MGs. One of the most important ESSs in MGs is the Flywheel Energy Storage System (FESS). In this study, a cooperative control system is proposed for FESS and diesel generator emulator to control the frequency of an islanded MG. Considering a sudden load change, a new frequency distribution-based digital control system is proposed to share the required power between diesel generator and FESS. The proposed method is able to automatically assign high and low frequency terms of the mismatch power to FESS and diesel generator, respectively. To evaluate the performance of the proposed control scheme, simulation results are carried out using MATLAB/Simulink software, while a programmable load emulator is employed for dynamic load emulation. To confirm the performance of the proposed method, the simulation results are also tested with a real-time simulator.