Abstract
Distributed power generation systems (DPGSs) based on inverters require reliable islanding detection algorithms (passive or active) in order to determine the electrical grid status and operate the grid-connected inverter properly. These methods are based on the analysis of the DPGS voltage, current, and power in time or frequency domain. This paper proposes a time-frequency detection algorithm based on monitoring the DPGS output power considering the influence of the pulsewidth modulation, the output LCL filter, and the employed current controller. Wavelet analysis is applied to obtain time localization of the islanding condition. Simulation and experimental results show the performance of the proposed detection algorithm in comparison with existing methods.
Highlights
A main issue associated to renewable energy sources connected to electrical grids through an active front-end is the proper operation of such grid interfaces in order to improve the power supply reliability and quality independently from the electrical characteristics of the renewable energy source and the grid conditions at the point of common coupling (PCC) [1]-[3]
This paper extends the analysis given in [37] and proposes a wavelet-based detection method which can detect the islanding condition from local measurements of PCC voltage and current signals, as in case of passive methods, but evaluates the highfrequency components injected by the PV inverter, which depend on the characteristics of the employed pulse width modulator, LCL filter and current controller, to reveal the islanding condition, as done by active methods
Due to the characteristics of the developed setup, a low pass filter has been applied in order to smooth cp5 values and, as a consequence, T L has been changed to 770.Q Three islanding tests have been carried out in order to evaluate the performance of the proposed controller under diverse operation conditions: distorted grid voltage, frequency variations and undervoltages
Summary
A main issue associated to renewable energy sources connected to electrical grids through an active front-end is the proper operation of such grid interfaces in order to improve the power supply reliability and quality independently from the electrical characteristics of the renewable energy source and the grid conditions at the point of common coupling (PCC) [1]-[3]. This paper extends the analysis given in [37] and proposes a wavelet-based detection method which can detect the islanding condition from local measurements of PCC voltage and current signals, as in case of passive methods, but evaluates the highfrequency components injected by the PV inverter, which depend on the characteristics of the employed pulse width modulator, LCL filter and current controller, to reveal the islanding condition, as done by active methods As it will be shown, the spectrum of the PV inverter output power will suffer a small variation, after the islanding operation mode, over a continuous and relatively wide frequency band.
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