Voluntary under-frequency load shedding at consumer-level

Under-Frequency Load Shedding (UFLS) can increase power system reliability by preventing total system collapse during emergency operating situations when load exceeds generation. UFLS is required by The North American Electric Reliability Council (NERC) for large consumers and has been implemented by utilities across the country. When frequency drops to a certain predefined value indicating generation shortage, feeder breakers in substations are opened to shed loads in favor of maintaining a balance between loads and generation. This conventional load shedding approach has some drawbacks including disconnecting critical loads causing consumer dissatisfaction and/or disconnecting more loads than necessary that could result in system over frequency. With increasing pressure to improve system reliability through more sophisticated approaches and Supervisory Control And Data Acquisition (SCADA) equipments, electric utilities are encouraged to apply more localized frequency sensing and load shedding schemes on the distribution system. Motivated by the above fact, this research presents a study to evaluate a consumer/household level load shedding approach. Case studies are presented that show the effectiveness of the proposed consumer level UFLS when compared with the traditional substation level UFLS. Different load shedding scenarios are considered for various test power systems using the simulation package Power System Simulation for Engineers (PSS/E). It is found that the proposed customer voluntary load shedding algorithm can restore system frequency after an under-frequency problem more effectively than the traditional approach. The load shedding at consumer level is better than that at the substation level in terms of avoiding the over frequency response problem and increasing consumer satisfaction level in smart grid.