Adaptive Active Frequency Drift Islanding Detection for PV Inverters
DOI:
https://doi.org/10.35682/jje.v1i2.719Abstract
The penetration level of renewable energy resources (RESs), such as photovoltaic (PV) plant and Wind plant (WP), in the power system is increasing exponentially, such plants connected with grid via inverter. This increasing rises from the attention about the undetected islanding operation. The islanding can be defined, according to IEEE std.1547, as a situation in which part of the power system becomes isolated from the rest of the system.
Islanding detection methods (IDMs) are divided into passive and active IDM. Among active IDMs, active frequency drift (AFD) is the most IDM applied in the literatures. AFD bases on injecting a distortion waveform to the original waveform of inverter reference current, this to drift the inverter frequency during islanding event to be out of the nominal range. Due to the distortion waveform high harmonics will be injected to the system. Recently, to decrease this harmonic an improved active frequency drift (IAFD) was presented in the literature. IAFD uses a constant step change in in 2nd and 4th quarters of the inverter reference current. IAFD has lower total harmonic distortion (THD) injected to the system compared with conventional AFD.
Since the non-detection zone (NDZ) has been considered as a performance measure for any IDM. The IAFD method did not introduce any improvement in NDZ over the AFD method. Thus, in this paper an adaptive step change is proposed to improve the performance of IAFD method, where a positive feedback of voltage frequency is used in this work to vary the distortion factor of IAFD. The adaption manner of step change enhances in increasing of injected perturbations during islanding event only. Which, it will reduce the NDZ during islanding event and decrease the injected THD in steady state operation. The proposed method has been theoretically analyzed and modeled using MATLAB/Simulink environment. As a result, the proposed method improves the performance of IAFD regard to the non-detection zone (NDZ).
