Islanding Detection Method for Inverter-based Distributed Generation Systems using a Signal Cross-correlation Scheme

Abstract

This paper describes the development of a new islanding detection method for inverter-based distributed generation systems, which uses a signal cross-correlation scheme between the injected reactive current and the power frequency deviation. The proposed method injects 1% of the reactive current to the rated current which brings about a negligible degradation of the power quality. It discriminates the islanding state, when the calculated cross-correlation index is larger than 0.5. The operational feasibility was verified through computer simulations with PSCAD/EMTDC software and experimental research with a hardware prototype. The proposed method can detect the islanding state without degrading the power quality at the point of common connection. Further study is required to overcome the cancellation of the injected reactive current from multiple distributed generation units interconnected with the utility grid.

A Hybrid Anti-islanding Method for Inverter-Based Distributed Generation

“…The inverter is controlled in the PQ control mode. The modeling detail is presented in [3]. The characteristics of load, system and DG are specified in table 1.…”

“…These methods have no effect on grid's power quality. Various passive methods including 1-Voltage and frequency protection [3], 2-voltage and current harmonics detection [4], 3-Voltage phase jump detection [5], 4-Comparing the rate of change of frequency [6], 5-Voltage unbalance [7], 6-Output power change rate [4], 7-Rate of change of frequency over power [8] have been studied. The main problem of these methods is that they have Non-Detection Zones (NDZs).…”

Comparative study of active anti‐islanding schemes compatible with MICs in the prospect of high penetration levels and weak grid conditions

“…On the other hand, the active anti-islanding schemes that are based on the harmonic injection technique have fast response to the island detection, low impact on inverter output power, and reduced NDZ, forming so an attractive solution for anti-islanding protection in Pdc-MICs [2,32]. Those schemes can be implemented as impedance measuring techniques at a specific frequency, as [2,8,32] suggest, or alternatively can be used to indirectly estimate the grid response as in [36][37]. As a drawback though, those schemes compromise to some extent the power quality of inverter output power, because of the harmonic current component injection, raising compatibility issues with the power quality standards of Section 2.…”

On the Injection of Sub/Inter-Harmonic Current Components for Active Anti-Islanding Purposes

“…In [4] a 75 Hz current component has been used to measure the impedance at the fundamental frequency. In [9] a triangular 20 Hz current component is periodically injected and grid condition at PCC is estimated by using a cross-correlation method. In [3] a modified version of the cross-correlation anti-islanding method in [6] is used, utilizing a 25 Hz current component, in order to compare against 2nd-order harmonic component injection.…”