Impact of ROCOF-based Islanding Detection on the Stand-Alone Operation of a Distributed Synchronous Generator

The need to improve the continuity supply indexes has encouraged the practice of operating distributed generation in islanded mode. However, one of the main issues for this operation mode is the transition to islanded operation, which requires changing the control objectives to maintain voltage and frequency at acceptable levels. In this context, this paper aims to analyze the performance of a well-known islanding passive detection scheme to change the control objectives of distributed generation and to enable the stand-alone operation in case of loss of the main grid. The detection scheme used is based on the rate of change of frequency relay, which is considered effective, easy to implement and widely accepted by the utilities. The relay model used was already validated with a commercial relay and its settings were based on ride through requirement presented in the IEEE Std 1547. The results have shown how the performance of the islanding detection scheme can influence the successful transition to stan -alone operation. The results show that, with an adequate pickup relay setting, the ROCOF is able to successfully enable the transition to islanded operation even for extreme operating conditions.

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