Abstract
The existing passive methods for islanding detection are mainly based on the detection of voltage and frequency deviation after islanding, using protections such as voltage vector shift (VVS) and rate of change of frequency (ROCOF). Although there are reported issues with these passive methods such as inherent non-detection zones and nuisance trips, utilities prefer the passive methods due to the low cost and simplicity of deployment. In this paper, one composite passive islanding detection method is presented. It tracks the voltage phase angle, the system frequency, and ROCOF every power cycle. If three phase voltage vectors shift in the same direction and the rotated angle values are balanced, the calculation of the accumulated phase angle drift (PAD) will be initiated. This calculation continues until the ROCOF measurement is below the ROCOF setting threshold. If the accumulated phase angle drift reaches the set angle threshold, the condition for islanding is claimed. The performance of this composite method is verified under different scenarios based on Matlab Simscape multidomain physical systems and practical waveforms recorded from sites. Although there are still non-detection zones, this composite PAD solution has better sensitivity than existing VVS and ROCOF methods and is stable under external system faults.
Highlights
During recent years, distributed generation (DG) has spread rapidly
A passive islanding detection using an accumulated phase angle drift has been proposed [6] where the phase angle drift calculation is based on the estimation of the main grid frequency, but the related field tests demonstrated that this method cannot ensure stability under system frequency fluctuation [7]
To simplify the the following subsections introduce the principles of rate of change of frequency (ROCOF) and voltage vector shift (VVS) relays based on synchronous analysis, the following subsections introduce the principles of ROCOF and VVS relays based on machines
Summary
During recent years, distributed generation (DG) has spread rapidly. There are more and more. A passive islanding detection using an accumulated phase angle drift has been proposed [6] where the phase angle drift calculation is based on the estimation of the main grid frequency, but the related field tests demonstrated that this method cannot ensure stability under system frequency fluctuation [7]. This paper presents a composite passive islanding detection method which includes both VVS relay and ROCOF relay operating principles. DGs and the inverter controller provides the islanding detection function Both ROCOF relay and VVS relay are applicable to inverter-interfaced DGs. The proposed solution is an improvement based on the existing ROCOF relay and VVS relay. This proposed islanding detection solution is introduced in the presence of synchronous generator type DG, but it is applicable for inverter-interfaced DGs. One similar passive islanding detection solution is presented in Reference [19].
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