Coordinated Frequency and Voltage Control Strategies for Islanded Microgrids with Demand Side Management Capability

  • Samrat Acharya

Student thesis: Master's Thesis

Abstract

The depletion of fossil fuels and alarming effects of greenhouse gas emission from fossil fuel power plants have been encouraging the growth of renewable power generation. The penetration of renewable energy sources (RES), particularly solar and wind, in power system generation portfolios is expected to increase in foreseeable future. However, intermittency in RES imposes challenges to their high penetration in the electrical grid. Moreover, the uneven distribution of RES, a higher efficiency of fossil fuel power plants, and huge investment in fossil fuels are hindering the high penetration of RES. Therefore, microgrids having conventional power plants as well as locally available RES with energy storage system (ESS) is today's rational option to move towards sustainable future energy. However, challenges remain with respect to issues of reliability, power quality, and power system security. These issues become more significant in islanded microgrids with high penetration of RES because of the lack of grid support. Maintaining frequency and voltage stability is the major requirement to safeguard power systems from the aforementioned challenges. This thesis presents a novel coordinated frequency control (CFC), and a voltage unbalance mitigation scheme for an islanded microgrid having a high penetration of RES. The control strategies are developed realizing the possibility of demand-side management (DSM), and insufficiency of generation side for providing frequency and voltage regulation in an islanded microgrid. The deployment of DSM, through thermostatically controlled loads (TCLs), for frequency and voltage unbalance mitigation respects the customers quality of service (QoS). The proposed CFC deploys fast responding TCLs, photovoltaic (PV) power system, battery energy storage system (BESS), and slow responding diesel generator. The performance of the CFC scheme is verified experimentally using OPAL-RT, a real-time simulator, and hardware-in-loop simulations. The proposed voltage unbalance mitigation scheme deploys the PV grid-tied inverter for reducing the negative sequence current injected by the grid and TCLs for balancing the loads among three phases of microgrids. The research findings show that coordination between generation and demand side in islanded microgrids demonstrates enhancement for frequency regulation and voltage unbalance mitigation.
Date of AwardMay 2017
Original languageAmerican English
SupervisorMohamed El Moursi (Supervisor)

Keywords

  • Demand Side Management
  • Renewable Power
  • Energy Storage Systems
  • Reliability of Renewable Energy Sources
  • Islanded Microgrids
  • Voltage Stability.

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