Detection of the Islanding Condition of Distributed Generation Systems via Variable Impedance and Frequency Deviation using Continuous Wavelet Transform
Anti-islanding protection, microgrid, frequency estimation, impedance estimation, continuous wavelet transform, discrete Fourier transform.
However, with the restructuring of the electricity system, this topology has been changing with the use of generators throughout the distribution system (distributed generation), which provides several benefits because it is located near the centers of consumption. Thus, the insertion of distributed generators, especially from renewable sources, becomes more common each year. However, this new configuration of the system brings new challenges concerning control, operation, and protection. One of the main problems of distributed generation in protection systems is the formation of small holes, which can result in safety risks for people and the electric power system. Among the various techniques of protection of islanding, passive and active techniques will be used in this work from the measurements of voltage and current signals to detect problems in the system. In this work it is proposed the frequency and impedance estimation from voltage and current signals using the continuous wavelet transform. The frequency and impedance estimation is evaluated through simulation and experimental studies. The estimation by the continuous wavelet transform is compared with the frequency and impedance estimation by the discrete Fourier transform. The results showed that the frequency estimation by the continuous wavelet transform had better performance than the Fourier transform estimation. However, the studies to impedance estimation by the wavelet transform had different performance when compared to the Fourier transform.