Analysis and Mitigation of the Impact of Ancillary Services on Anti-Islanding Protection of Distributed Generators

The incorporation of ancillary services on distributed generators (DGs) at utility level has imposed several challenges on the existing distribution networks. To address one of such problem, this paper discusses the impact of ancillary services, mainly the voltage ride through (VRT) capability and active power curtailment control (APCC) of DGs on their anti-islanding protection scheme (AIPS). In this study, different types of load models (viz. ZIP, induction motor (IM) and composite loads) have been considered and non-detection zone (NDZ) characteristics are obtained for a modified IEEE 1547/ UL 1741 test system for analyzing the problem. Further demonstration of this issue has been carried out by conducting time domain simulations in PSCAD/EMTDC platform on modified IEEE 1547 and CIGRE low voltage benchmark test system having composite loads at each of the load buses. Finally, an appropriate mitigation framework has been proposed by incorporating a hybrid islanding detection technique to enable simultaneous implementation of VRT, APCC and AIPS in DGs. The online implementation of the proposed framework is realized in MATLAB/Simulink platform and real-time simulations are performed in OPAL-RT (OP5600) test bed on the modified IEEE 1547/ UL 1741 test system for validating its efficacy.