Abstract
The increasing penetration of renewable generation increases the need for flexibility to accommodate for growing uncertainties. The level of flexibility is measured by the available power that can be provided by flexible resources, such as dispatachable generators, in a certain time period under the constraint of transmission capacity. In addition to conventional flexible resources, energy storage is also expected as a supplementary flexible resource for variability accommodation. To aid the cost-effective planning of energy storage in power grids with intensive renewable generation, this study proposed an approach to determine the minimal requirement of power capacity and the appropriate location for the energy storage. In the proposed approach, the variation of renewable generation is limited within uncertainty sets, then a linear model is proposed for dispatchable generators and candidate energy storage to accommodate the variation in renewable generation under the power balance and transmission network constraints. The target of the proposed approach is to minimize the total power capacity of candidate energy storage facilities when the availability of existing flexible resources is maximized. After that, the robust linear optimization method is employed to convert and solve the proposed model with uncertainties. Case studies are carried out in a modified Garver 6-bus system and the Liaoning provincial power system in China. Simulation results well demonstrate the proposed optimization can provide the optimal location of energy storage with small power capacities. The minimal power capacity of allocated energy storage obtained from the proposed approach only accounts for 1/30 of the capacity of the particular transmission line that is required for network expansion. Besides being adopted for energy storage planning, the proposed approach can also be a potential tool for identifying the sufficiency of flexibility when a priority is given to renewable generation.
Highlights
Integrating renewable energy is considered as a pathway to de-carbonize the power sector.The increasing penetration levels of variable renewable energy increase the need for sufficient flexible resources
The available flexible resources considered in the flexibility assessment (FAST) approach are diversified into dispatchable power plants, energy storage, interconnection between adjacent power systems and Energies 2017, 10, 468; doi:10.3390/en10040468
The proposed model can be employed as a flexibility assessment tool to determine whether the level of flexibility provided by existing dispatchable generators and transmission capacity is sufficient or limited
Summary
Integrating renewable energy is considered as a pathway to de-carbonize the power sector. The level of flexibility provided by existing power plants has a great impact on the grid integration of renewable generation. We present an approach to determine the minimal power capacity of energy storage from the aspect of providing flexibility to accommodate variability from high penetration levels of renewable generation. If the energy storage is required to improve the level of flexibility, the minimal power capacity and the appropriate location are determined From this aspect, the proposed model can be employed as a flexibility assessment tool to determine whether the level of flexibility provided by existing dispatchable generators and transmission capacity is sufficient or limited. We show impacts of uncertain renewable generation on constraints of power balance and the transmission network
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