Grid-tied Power Control and Storage Reduction in AC Microgrids with Hybrid Electric Springs

Battery storage is the traditional method of connecting renewable energy (RG) to the electric grid (BESS). In this cascaded combination of a grid-connected inverter, a battery, and RG, the power difference between RG and the grid passively controls the battery power. This increases the storage capacity of the battery while affecting the state of charge (SoC) regulation of the battery. This study proposes grid-connected power regulation and battery storage capacity reduction in AC microgrids by integrating a hybrid electric spring (HES) with the RG and the non-critical load (NCL). With such an integrated design, a battery, the NCL, and the power flow in the grid can be managed more easily. In addition, the proposed HES is capable of operating in a wider range of grid-connected power controls than the standard BESS and existing electrical sources. The operation, steady state analysis, and control architecture of HES are described. Experiments and computer simulations are performed to validate the grid current control and battery SoC control functions.