DEVELOPMENT OF AN IMPROVED FORCED ISLAND AND LOAD SHEDDING SCHEME TO PREVENT SYSTEM COLLAPSE

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Department of Engineering

ABSTRACT
This research work presents a scheme that identifies line outage and generator outage using contigency analysis and effectively splits the network into a set of predefined islands, with a load shedding strategy to minimise the adverse effect of each outage and to ensure system security. In this research work, Newton Raphson power flow was used for the power flow analysis of the network. Also, Active Power Loading Perfomance Index was used during the contigency analysis to rank the transmission line and generator outage based on the severity of each outage. For each outage causing a line overload and voltage violation, the network splits into predefined islands and power flow analysis is performed on the new island to check the stability of the network. For each island found to be unstable, a power mismatch, and under voltage load shedding scheme is used to ensure the system stability. The developed algorithm was implemented on the IEEE 6 and 14 test bus network. From the IEEE 6 bus network, ten outages resulted in the split of the network into two islands. Also, the developed load shedding scheme was applied on each island that was found to be unstable after power flow analysis. The average voltage profile improvement of the island network over the base case was found to be 13.02% after load shed of 42.3 MW. Also, from the IEEE 14 bus network, the contigency analysis considered twenty four outage, with twenty one outage causing a split of the network into two islands. Load shedding scheme was also applied on each newly formed island found to be unstable. The average voltage profile improvement of the islands over the base case was 2.89% after load shed of 80.92 MW. The validation of this research work was performed by simulation, and comparing with the work of Soman et al,.(2015a), using load shed speed and voltage profile as performance metrics. The developed method obtained an average load shed speed improvement of 63.3% and an average voltage profile improvement of 1.01%. Also, from the results obtained, it is quite evident that the developed scheme has a better performance than Soman et al,.(2015a).