Adaptive under-voltage load shedding scheme for large interconnected smart grids based on wide area synchrophasor measurements

The existing local protection schemes for undervoltage protection in power systems are not engineered to protect the system against wide area disturbances. Therefore, system integrity protection schemes (SIPS) designed to preserve the integrity of the system are required. This study proposes a new response-based SIPS for adaptive undervoltage load shedding (UVLS) in large interconnected systems based on the IEEE C37.118.1-2011 synchrophasor measurements from widely dispersed phasor measurement units (PMUs) synchronised to the reference time of the global positioning system. The control signals to shed the feeder loads are based on high-speed IEC 61850 Generic Object Oriented Substation Event messages. The proposed adaptive UVLS-SIPS algorithm calculates in real-time the total amount of load to shed corresponding to the severity of the disturbance using the least squares algorithm. The amount of load to shed and its distribution across the interconnected system is based on a formulated reactive power mismatch and adaptive weighted summation real-time voltage stability assessment index, respectively. The proposed UVLS-SIPS algorithm was deployed onto a programmable logic controller (PLC), and was tested under various dynamic conditions using the New England 39-bus test system. Real-time simulations were conducted with an industrial-grade 'proof-of-concept' testbed.