A Novel Method of Frequency Regulation in Microgrid

Owing to generation and demand mismatch, the frequency deviation and the rate of change of frequency (RoCoF) may become drastic at times in an islanded microgrid. This is due to increased penetration of noninertial renewable energy sources that brings down the system's resilience to any kind of disturbance. Therefore, efficient control algorithms are required to mimic the inertial behavior of a conventional synchronous machine to arrest/limit any sudden change. This work focuses on frequency regulation of microgrid during transient conditions by means of fast-responding external energy reserve. The characteristics of a weak grid has been studied and simulated through modeling a virtual synchronous machine. An inverter model is also developed to integrate the energy storage system (ESS) to the grid and a double second-order generalized integrator phase locked loop (DSOGI-PLL) is implemented that is capable of synchronizing the system under distorted and unbalanced situation. A new technique to estimate the frequency of the microgrid is reported. A simple proportional controller-based approach for different level of pulsed power injection (using ultracapacitors and batteries) is proposed and simulated using MATLAB. Experimental demonstration is made using batteries only but with two different current-limits. The controller is implemented using dSPACE1103.