Electric Springs With Coordinated Battery Management for Reducing Voltage and Frequency Fluctuations in Microgrids

Electric springs based on power electronics have been proposed as a demand response method for stabilizing power grid fed by substantial intermittent renewable energy sources. Associated with energy storage, they can provide both active and reactive power compensation. Due to the limited storage capacity of the battery, this project explores a new control scheme for the third version of the electric springs (ES-3) to operate under the physical constraints of the state-of-charge of the battery for microgrid stability applications. The ES-3 is based on a bi-directional grid-connected power converter with a battery bank. Unlike the traditional control of grid-connected power inverters for injecting renewable power to the power grid, the proposed control scheme puts the stability of the power grid as a high priority while maintaining its normal bi-directional power flow functions. Such a scheme has been tested in an experimental prototype and a power grid simulator. Results are presented in this paper to illustrate the use of the scheme in battery’s monitoring, charging/discharging management, and output power control.