A Novel Method of Frequency Regulation in Microgrid

Abstract

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 micro-grid. This is due to increased penetration of non-inertial 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 (VSM). 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.

Adaptive Frequency-Based Reference Compensation Current Control Strategy of Shunt Active Power Filter for Unbalanced Nonlinear Loads

“…In this paper, the dual second-order generalized integrator phase-locked loop technique (DSOGI-PLL) is directly applied, which is based on the second-order generalized integrator (SOGI), as depicted in Figure 2, where PI is the proportional-integral controller. This method is more accurate than the traditional PLL technique for the harmonic interference condition, as proven in [13]. However, the synchronization accuracy is dependent on the power system angular frequency ω, as shown in the architecture of Figure 2.…”

Grid–Following DVI–Based Converter Operating in Weak Grids for Enhancing Frequency Stability

“…This method employs an adaptive ESS dispatch strategy in a microgrid to provide frequency support for the host grid. The work presented in [14] focuses on frequency regulation of a stand−alone microgrid by means of external energy reserve. Therein, an ESS−fed inverter is governed using a current controller equipped with a new frequency estimation technique.…”

Distributed Control Strategies for Microgrids: An Overview

“…Because of the relatively high penetration of renewable energy resources, MGs typically have a reduced value of inertia, [208]. Furthermore, renewable energy is usually strongly dependant on weather conditions, and this produces some de-gree of intermittent and uncertainty [209], placing additional stress on the operation and control of MGs [210]. Moreover, renewable energy is usually interfaced with the MG using a power converter, which electrically decouples them from the MG. As discussed in several publications, where stability issues are addressed (see [173], [209], [211], [212]), the reduction of inertia in a system can severely compromise the frequency stability.…”