| Summary: | 碩士 === 國立中正大學 === 電機工程研究所 === 101 === In recent years, due to the soaring fossil fuel prices and environmental concerns, the development of renewable energy resources have become an important issue in many countries. Microgrid can help integrate renewable energy and other forms of distributed energy resources (DER), increases the DER penetration, and improve power quality and reliability through appropriate management. DER including distributed generation (DG) and distributed storage (DS) are sources of energy located near local loads.
Many forms of distributed energy resources are interfaced to the utility grid with power electronic converters. These devices make the microsources more flexible in their operation and control. In general, under the normal operation, a microgrid is connected to the utility grid, and each DG provides a preset power to the network through active/reactive power control (PQ control), whereas the utility grid is responsible for supplying/absorbing any power discrepancy. When the microgrid is disconnected from the utility grid, at least one unit switches to droop control from PQ control in order to regulate the voltage and frequency in the microgrid and continue to offer power to local load. At the system level, the microgrid uses a hierarchical control. The microgrid control center (MGCC) will send signals to microsource controllers (MC) and load controllers (LC) informing which control strategy to use.
This thesis adopts Matlab/Simulink to create microgrid models. Several operation conditions including grid connected mode, islanding mode and load variation are simulated. Moreover, utilizing real-time digital simulator (RTDS) to compare the accuracy and computation time between real-time and off-line simulations is performed. Finally, the performance and effectiveness of the proposed control strategies for the microgrid are verified by investigating the simulation results.
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