| Summary: | 碩士 === 國立臺灣大學 === 電機工程學研究所 === 96 === The frequency estimation is an important issue for power signal system. The dynamic relationship between the load and the generation can be detected by measuring the power system frequency. Because more and more distributed power source units are used in generation, it is more important for us to detect the frequency signals when distributed power source units are connected with synchronous utility system. In order to minimize the damage caused by the operation of synchronizing connection, we must have the exact frequency signals. Furthermore, we must pay attention to the harmonic pollution in frequency signals because the ruin of harmonic pollution is heard usually. We hope to get the correct parameters fast from the frequency signals analysis, and to use the filtering methods for the harmonics and noise from signal, for the operation of synchronizing connection of distributed power source units.
Firstly we will introduce the common distributed pwer source units and probe into the advantage and disadvantage of islanding detection that is closely related to distributed power source units and the reason why the detection will fail. After islanding operation, we have to estimate the frequency on both sides of utility system and island system for the reconnection of both systems. So we will present the Extended Discrete Fourier Transform which is based on Discrete Fourier Transform (DFT) and combines FIR (Finite Impulse Response) filter then the algorithm not only can keep advantage of fast computation of frequency detection and eliminate the DC offset but also can enhance the resistance of the computation error caused by Discrete Fourier Transform. The algorithm can improve the accuracy for islanding detection and have a good performance for filtering harmonics and noise. Finally, we can reduce the damage when distributed resources units and utility operate in parallel synchronization.
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