Operation scheduling method in an off-grid considering frequency violation probability caused by short-term variation

Abstract

The use of renewable energy (RE) resources in off-grid applications is a promising solution from both the economic and environmental perspectives. However, the employment of RE generation should consider the uncertainty in their generation output; in particular, short-term variations in generation output result in serious frequency violations. The development of the off-grid planning, operation, and scheduling considering frequency variation is significant. This study proposes a probabilistic model for the frequency variation caused by load variation, which includes the dynamics of rotating generators and frequency-supporting smart inverters. The proposed method calculates the maximum frequency deviation by transforming the block, considering the output limit of the governor and smart inverters. This calculation is fast because it does not require time-sequential simulation. The effectiveness of the proposed method for off-grid operational scheduling problems was demonstrated through numerical studies. The results show that the proposed method can evaluate the same results as time series simulations 1500 times faster. Additionally, frequency deviations caused by short-term variations can be avoided, and battery capacity for zero frequency deviation is estimated with a 5% error. These results have the potential to contribute significantly to the operation of the grid with a large portion of RE resources.