Coordinated generation and transmission expansion planning with energy storage systems to allow high penetration of renewable energy

Renewable energy sources (RES) integration in power system has increased globally in recent years and renewable portfolio standards (RPS) are broadly adopted to encourage further investments in RES. However, large-scale integration of these variable energy sources poses several challenges to network operators. Traditional planning models also do not lead to economic expansion plans at high integration of renewable energy due to renewable energy curtailments. Researchers have incorporated several techniques, such as dynamic line rating and demand side management, into network expansion planning for effective utilization of RES, but these techniques are not effective at high penetration of renewable energy. There is growing interest in energy storage system (ESS) due to its ability to deal with intermittency issues of RES by storing excess energy when available and delivering back during peak hours. This paper introduces a coordinated generation, transmission, and storage expansion planning model, formulated as a mixed integer linear programming (MILP) optimization problem. The model is used to study the economic impact of co-optimizing investments in these three asset classes subject to RPS targets up to 75%. We also analyze ESS impact on CO 2 emissions from thermal sources and overall network performance. The model is implemented on a modified IEEE 24-bus system and numerical results show that up to 16.2% savings could be achieved in total cost at 75% RPS by utilizing the existing network more optimally compared to the case when no ESS investments are considered. Moreover, the renewable curtailments are significantly reduced at high RPS by integrating ESS and network utilization is also increased.