Study on improvement of micro-grid´s power quality based on APF and FESS

As the distributed energy is environmental and renewable, micro-grid (MG) has attracted widespread concern since it is raised, and it is becoming the future direction of the power system. In order to connect MG to the grid and make it available to loads, the power quality must meet the requirements set. In that case, energy storage and filtering is two main ways to achieve the goal effectively. This paper presents a proposal that a flywheel energy storage system (FESS) and an active power filter (APF) act together to improve the power quality of MG. Compared with other means of energy storage, flywheel is eco-friendly, with characteristics of long maintenance cycle, high energy density, fast response speed, and unlimited times of charge and discharge. APF performs better and is more flexible than passive filtering in the application as well. This paper analyzes the flywheel´s charge and discharge processes and APF´s harmonic detection and compensation principles theoretically, and makes a study of the energy conversion circuits and the control methods of FESS. At last, simulation model of MG system is built based on FESS and APF using Matlab/Simulink. The power quality of load is detected and analyzed both in normal operation and emergency, and the simulation results prove the feasibility of the proposal.