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Controlled islanding strategy of Central China Power Grid based on branch potential energy

Traditionally, controlled islanding detects the impending system instability and opens appropriate tie-lines before cascading outages occurrence. In this paper, a novel controlled islanding strategy is proposed and applied in Central China Power Grid. A criterion based on the branch potential energy is defined to detect the out of step condition, which can be calculated on line for each tie-line of the interconnected system using Phasor Measurement Unit (PMU) measurement. Detection of the tie-line with the criterion being zero implies that generators at one side of tie-line lose synchronization to those at the other side and the electrical center lies in this line. Once the system instability is detected online based on the branch potential energy criterion, it is necessary to identify the tie-lines that should be opened for the system separation. The offline identification can be predetermined by time domain simulation of the interconnected grid with major disturbance, which can be deemed as offline islanding control strategy. Case studies with Central China Power Grid validate the effectiveness of the proposed islanding control strategy.