Assessing the Risk of Blackout in a Low Inertia Power System and a Possible Countermeasure

Abstract

The chance of blackout in a low inertia grid and its mitigation via Battery Energy Storage System (BESS) are investigated in this work. There has been a rapid uptake of renewable generation such as wind power in many countries. In recent times, wind power plants widely utilize variable speed wind machines. Mostly, these machines are not accounted for frequency control. Due to a small number of committed synchronous machines at times, a wind prolific power system is likely to have insufficient inertia and governor responsive reserve. In this situation, a large contingency may result in unsatisfactory frequency response. In extreme cases, the frequency may not be even rescued and the system could encounter a blackout. To overcome this challenge, deployment of BESS can be a potential solution. However, frequency response in presence of BESS may vary depending on the load shedding schemes and the associated time delays of the relays. To explore this issue, this paper scrutinizes the risk of blackout following a network separation in a low inertia grid under substantial wind penetration. Then, a frequency receptive BESS is employed to minimize the blackout risk. Also, two load shedding approaches - conventional Under Frequency Load Shedding (UFLS) and Rate of Change of Frequency (ROCOF) driven load shedding with various time delay settings are considered. Simulation results reveal that a combination of BESS and ROCOF based load shedding scheme can be a worthwhile choice to improve the frequency excursion under high renewable penetration.