Optimal Planning of Integrated Energy Systems Considering Multi-Day Low-Output Events and Efficiency Degradation of Electrolyzer

Hydrogen storage plays a key role in mitigating the long-term fluctuations in integrated energy systems (IESs), such as the multi-day low-output events (MLEs) that last for several days. However, most studies do not consider the impacts of the MLEs on the IES planning. Therefore, this paper proposes an optimal planning for IESs considering the MLEs of wind power and the efficiency degradation of electrolyzer (EZ). First, a comprehensive evaluation index characterizing the severity of the MLE is proposed. On this basis, a novel representative chronological time period clustering (RCTPC) method is proposed to preserve the MLEs during the clustering, where the MLEs and regular intraday fluctuations are clustered separately. Moreover, an improved IES planning model considering the MLEs of wind power and hydrogen storage is further proposed to address the long-term fluctuations, where an EZ model considering the efficiency degradation is developed with different load rates and continuous operation time. Finally, the methodology is validated on an IES comprising an IEEE 33-node power network and 6-node heat network. Numerical results show that the proposed RCTPC can better retain MLE in the clustering process, and considering the efficiency attenuation of EZ can reduce the total annual cost by 4.13%. This method provides guidance for IES planning under extremely renewable intermittent conditions.