An Improved Fuzzy Controlled Back-to-Back Electric Spring Using Hybrid Structure of ES-1 and Shunt-APF to Improve Power Quality in Microgrids

Electric spring (ES) is a new technology that can be used for fast demand-side management to balance the power between generation and consumption in smart grids. In this paper, the back-to-back structure of electric spring is controlled to operate simultaneously as electric spring and shunt active power filter (shunt-APF). That means, the series part of the back-to-back electric spring regulates the critical load voltage and applies the demand-side management and the parallel part operates as a shunt active power filter capable of power factor correction and current harmonic compensation. In the proposed structure, due to harmonic compensation and power factor improvement by the parallel inverter, the output power capacity of the electric spring is increased compared with the first and second generation of electric springs (ES-1 and ES-2), and the performance is improved in critical conditions. Additionally, to improve the robustness of the control system against uncertainties in the grid system, two fuzzy logic controllers are designed to control the voltage of the electric spring and the DC link voltage. The theoretical analysis is validated by simulation results using MATLAB/SIMULINK software.