A motor-generator and supercapacitor based system for microgrid frequency stabilization

This research introduces an energy storage system to deliver microgrid frequency response - the coupling of a doubly-fed induction generator and a squirrel cage induction machine as a motor/generator set to deliver an immediate inertial response to the change of frequency, as well as an inverter and supercapacitors to deliver short term energy response. This paper outlines the simulation, design and hardware testing results of this system. A control system is created to monitor the grid frequency and activate an inverter to either charge or discharge a bank of capacitors depending on the measured conditions. For example, when the frequency is measured below 60 Hz, the system injects power into the microgrid to arrest the frequency deviation; above 60 Hz the energy storage system absorbs power. For a microgrid with a high penetration of distributed renewable generation such as small scale solar and wind systems, stabilizing inertia, which is typically provided by large-scale synchronous generators, will be minimal. This system adds rotating inertia and short-term energy storage to stabilize the microgrid frequency. A description of the major components as well as their simulation and hardware testing results is described herein.