Battery-based flywheel energy storage system for microgrid control

Flywheel Energy Storage System for Microgrids Based on DC Link Battery Charge/Discharge Control

This technology features an energy storage system consisting of a flywheel assembly, a wound-rotor induction machine, a generator-side converter, and a grid-side converter, where a DC/DC converter and a battery are connected to the capacitor between the two converters to control capacitor voltage charging and discharging.

Microgrids using solar and wind power as primary sources require separate compensation control to meet power quality standards due to the stochastic fluctuations in power generation. These output fluctuations have posed significant challenges to the efficient operation of microgrids.

This technology allows for independent control of the generator-side and grid-side converters, as the battery-side converter controller uses proportional-integral control on the error between the capacitor voltage and the reference voltage to maintain the DC link voltage via the battery. It can be applied to wind-integrated microgrids and standalone small-scale power grids to smooth output fluctuations and maintain stable frequency and voltage even during grid disconnection.

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Key Features:

• A flywheel assembly that generates power through rotational motion, along with a wound-rotor induction machine featuring connected rotor and stator windings
• A generator-side converter connected to the rotor windings that controls stator power to mitigate wind power fluctuations generated by the flywheel assembly
• A grid-side converter connected to the microgrid that controls the power required by the grid and regulates power frequency when the grid is disconnected
• A DC/DC converter connected to the capacitor between the two converters that performs proportional-integral control on the error between the measured voltage and the DC voltage reference to manage capacitor voltage charging and discharging via the battery

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This invention was developed with support from the Ministry of Trade, Industry and Energy for the development of flexible interconnection and dynamic optimal operation technology for multi-microgrids in a HILS environment.

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