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Value evaluation of ancillary service offered by energy storage systems

Under the deregulation of the electric power industry, the provision of ancillary service takes on an important role. Energy storage systems can provide ancillary service in addition to generators. However, as energy storage systems are still quite expensive, it would be helpful to estimate the potential revenue from the ancillary service. The value of ancillary service related to active power, for example, the frequency control, is relatively easy to estimate. On the other hand, the value of ancillary service related to reactive power is difficult to estimate. In this paper, we propose a new method for assessing the value of reactive power provided by energy storage systems. Reactive power from the energy storage system benefits power systems such as the increase of energy transactions, reduction of transmission losses and voltage sustainability. Reactive power is assessed by converting these benefits into active power causing the same effect.