Sara Ashfaq
University of New South Wales, Sydney

University of New South Wales, Sydney

URL: https://www.researchgate.net/profile/Sara_Ashfaq3

Due to the the increased load demand, renewable distribution generations (DGs) are being integrated with current electricity grids globally. The increased penetration level and the uncertain power output of weather-based DGs lead to system instability, reverse power flow, power fluctuation and poor frequency regulation. Currently, to synchronize the inverter based low inertia DGs to AC microgrids, modified frequency and voltage droop control methods are being implemented. But these methods have drawbacks of instability, harmonic distortion and reactive power sharing. To overcome these drawbacks, a novel approach of regionalization has been proposed for the islanded microgrid. In this method, the radial distribution network of islanded microgrids (MGs) has been regionalized into two types of regions namely Conventional Generation Dominant Regions (CGRs) and Renewable Generation Dominant Regions (RGRs). RGRs will operate on constant frequency control methodology and CGRs will operate using the conventional control techniques. Both type of the regions are connected with AC/DC/AC converters and can share power bi-directionally. Both regions can work fully independent with their own control methodology while satisfying their load demands. In case of more wind or solar energy, extra amount of power can be shared from RGR to CGR. In case of lower output of renewable energy, power can be transferred from CGR to RGR while considering the load profile and excess amount of energy. Unplanned stochastic power-sharing strategy between the regions has been introduced for secure and reliable islanded operation. In unplanned power sharing, power exchange will be optimized while considering the availability of renewable generation, charging and discharging of BESS and load profile of MG. In large power systems, power exchange can optimize the overall power dispatch of MG with more number of regions, DGs and BESS. Maximum and minimum power exchange limits have also been calculated with the consideration of branch capacity and power transfer capability of back-to-back converters. To validate the results, experimentations have been carried out in MATLAB coding and simulation environment by converting the IEEE 15, 33 and 69-bus test systems into regionalized islanded microgrids. In regionalized microgrid, conventional generation dominant regions will operate on the conventional control methodologies as per the fully developed and standards of IEEE, IEC and other. The control methodology proposed for Renewable Generation Dominant Region is very novel and adaptive to the dynamic load and renewable energy changes. The major advantage of this scheme is that dynamic balance between power demand and power generation is always sustained. The system steady-state voltages can be maintained almost at rated value. The system operates at constant 50 Hz. One future challenge of this approach is the development of different levels of control in the proposed regionalized microgrid, especially for the renewable generation dominant region consisting of large and complex distribution systems. Nevertheless such research will be considered and treated in future. This approach has lots of benefits over currently developed droop control methods. As, in conventional droop based methods there is requirement of setting points from secondary or tertiary control centres, they are incapable of handling of microgrid operation without communication link. But this approach offers constant frequency and steady state voltage for renewable energy based region all the time and islanded regionalized microgrid can operate in the steady state with the temporary loss of communication link and in decentralized mode. The cost-benefit analysis of the proposed approach has showed reduction in the operation and maintenance cost of regionalized microgrid as compared to non-regionalized microgrid. Currently, the hardware implementation of this approach is being set up at laboratory level. In future, a small scale regionalized microgrid will be developed at a remote location to validate the results and it will demonstrate the more secure and reliable power from renewable generation at minimized cost. The future goal of regionalized microgrid approach is to investigate the different research challenges for its successful real time implementation.

About the Author: Sara Ashfaq currently works as a PhD researcher at the Department of Electrical Engineering and Telecommunications, University of New South Wales, Sydney, Australia. Her research interests are Smart Grids, Renewable Energy Planning, Regionalized Microgrids and Optimization & Control of Modern Power Systems,. . Her most recent publication is "Regionalization of Islanded Microgrids considering the Planning and Operation Stages".