Improvement of Control of Hybrid AC-DC Microgrid in Islanded Mode

Khorsandi, Amir | 2015

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 47473 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Mokhtari, Hossein
  7. Abstract:
  8. A microgrid is a collection of loads, sources, and power storage units that operates as a single controllable system and can operate in grid-connected or islanded mode. From the generating side, renewable energy resources such as photovoltaic system, fuel cell and power storage units are inherently DC. From the load side, electronic loads such as computers, data centers and most of the variable speed motor drives require a DC supply. Therefore, DC Microgrids have gained widespread attention in recent years. On the other hand, since existing distribution systems are mostly AC, a hybrid microgrid is more likely. The hybrid microgrid is composed of two AC and DC subgrids interlinked by power converter. The hybrid microgrid has different AC and DC loads and sources. The loads and sources in these two subgrids are such distributed that due to the reduction of multiple conversions through power electronics devices, the efficiency and reliability of the hybrid AC/DC microgrid can be increased.
    In this thesis, control and power management of the hybrid microgrid is investigated. To improve the control of the DC subgrid, two decentralized methods are proposed. The first proposed method is based on the conventional droop control method. In the second proposed method, a droop curve method has been used. The main advantage of the proposed methods is high accuracy without using any communication link. Simulation and experimental results verify the satisfactory performance of the proposed methods. In addition, to damp the oscillations caused by constant power loads, an active damping method is proposed.
    Moreover, in this thesis a decentralized method for control and power management of the interlinking converter has been proposed. In this method, the loading condition of the two subgrids is evaluated using measurement of the voltage and frequency on the AC side and the voltage on the DC side. Depending on the defined control strategies, active power is transferred between the two subgrids to maximize the system efficiency. The performance of the proposed method has been simulated in MATLAB/Simulink. The simulation results show the effectiveness of the proposed method
  9. Keywords:
  10. Power Management ; Distributed Generation ; Alternative Current Microgrid ; Droop Control ; Hybrid Alternative current-Direct current (AC-DC)Microgrid

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