Abstract
In this paper, a modified Q-f droop curve method for inverter-based distributed generator is proposed. The proposed method has merits such as detecting islanding with zero non-detection zone, negligible effects on power quality and simple implementation. A new parameter is embedded in the reactive power reference to accelerate the frequency deviation at the point of common coupling, until the islanding is detected. Therefore, a passive under/over frequency relay will be simply sufficient to detect islanding within the permissible limit. The proposed method is modelled with computer-aided design SIMULINK/MATLAB environment. The proposed method is analysed for operation with unity and non-unity power factors. The performance is validated for various loading quality factors with a negligible change in detection time. In addition, it is confirmed that the proposed system is stable under unbalanced loading and switching conditions. The proper operation of proposed islanding detection method under multi distributed generators connection is validated. The results of the hardware experimentations are presented to confirm the proposed method analysis and simulations.
Highlights
One of the serious concerns of electrical network utilities is an unintentional islanding in grid as it can cause a hazard for utility line-workers and damaging distributed generator (DG) during the DG reconnection [1]
In [4], the islanding detection signal has been combined with a voltage unbalance of Point of Common Coupling (PCC) voltage to help the local method for islanding detection.The main advantage of communication-based methods is that, zero non-detection zone (NDZ) is achievable
In [9]. a passive islanding detection method was introduced, which is based on phasor measurement unit (PMU)
Summary
One of the serious concerns of electrical network utilities is an unintentional islanding in grid as it can cause a hazard for utility line-workers and damaging distributed generator (DG) during the DG reconnection [1]. In [18], a method based on active frequency drift was proposed, which has been modified by the positive feedback, to improve the islanding detection performance It does not show the effectiveness of the method for different loading quality factors. An average absolute frequency deviation value was proposed during an islanding condition The advantage of this method is its ability to detect islanding, when active and reactive powers mismatch are zero. In [28], a hybrid method including voltage unbalance/Total Harmonic Distortion and bilateral reactive power variation was introduced It has a fast detection time; its performance under multi DGs connection has not been considered.
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