Development of dynamic controller of flywheels for frequency regulation of microgrids

• Main Author: Wong, Yuet Xin
• Other Authors: Gooi Hoay Beng
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2020
• Subjects: Engineering::Electrical and electronic engineering
• Online Access: https://hdl.handle.net/10356/138978
• Institution: Nanyang Technological University

With the increasing penetration of solar energy, new challenges to balance power generation and consumption are introduced in the system. The power balance affects the system frequency regulation. Flywheel energy storage system (FESS) is a promising option for frequency regulation. There are several advantages of FESS, such as it controls the voltage on the DC link well; can withstand severe duty cycles; and switch from full output to full absorption mode in mere seconds. However, there is currently a lack of such studies for solar applications. Therefore, this project aims to provide a deeper understanding of the use of FESS along with a photovoltaic (PV) system to improve the frequency regulation in microgrids. A dynamic controller was developed in Matlab/Simulink, and the performance of the system was analyzed. The project was split into three parts: design of the system, hardware-in-the-loop (HIL) simulation of the system, and testing of an actual FESS. The model was successfully designed, although an arbitrary FESS was built separately. HIL simulations of the model in OPAL-RT and dSPACE show that the controller is working and successful as crucial outputs such as the DC link voltage, AC output voltage, and system frequency were maintained well. Finally, testing of the discharge characteristics of an actual FESS for UPS applications was conducted. Results show that as the load demand increases, the flywheel speed decreases faster. This information can be used to accurately model the FESS in future works. Overall, a dynamic controller with a high potential to regulate the frequency of the system was developed. The PI controllers are tuned to reduce overshoots, fluctuations, and settling time for the system. The designed PI controllers can be further tuned based on the system requirements. With the actual charge and discharge characteristics of the FESS known, modeling of the FESS can be improved. Lastly, the model can be integrated with the microgrid and tested with actual hardware.