Abstract
This paper presents an experimental application of LiFePO4 battery energy storage systems (BESSs) to primary frequency control, currently being performed by Terna, the Italian transmission system operator (TSO). BESS performance in the primary frequency control role was evaluated by means of a simplified electrical-thermal circuit model, taking into account also the BESS auxiliary consumptions, coupled with a cycle-life model, in order to assess the expected life of the BESS. Numerical simulations have been carried out considering the system response to real frequency measurements taken in Italy, spanning a whole year; a parametric study taking into account different values of governor droop and of BESS charge/discharge rates (C-rates) was also performed. Simulations, fully validated by experimental results obtained thus far, evidenced a severe trade-off between expected lifetime and overall efficiency, which significantly restricts the choice of operating parameters for frequency control.
Highlights
The “smart grid” paradigm envisages a massive presence of non-programmable renewable energy sources: in this context, battery energy storage systems (BESSs) are liable to play a key role at both distribution and transmission level, given their potential ability to fulfill roles such as load shifting, peak shaving, frequency and voltage control [1,2,3,4,5,6]
The model adopted for simulating the LiFePO4 BESS consists of a coupled electrical-thermal model for a battery string, plus a “lifetime” model to take into account the long-term battery model for a battery string, plus a “lifetime” model to take into account the long-term battery loss of capacity
The paper studied the application of a LiFePO4 BESS to primary frequency control, in the ENTSO-E Continental Europe grid; technical data from Terna’s experimental system has been used for defining BESS characteristics
Summary
The “smart grid” paradigm envisages a massive presence of non-programmable renewable energy sources: in this context, battery energy storage systems (BESSs) are liable to play a key role at both distribution and transmission level, given their potential ability to fulfill roles such as load shifting, peak shaving, frequency and voltage control [1,2,3,4,5,6]. Technical features such as battery size (in terms of both rated power and energy), efficiency, transient performance, cycling and lifetime depend on the specific application. To date there is not enough operating experience confirming the PFC applicability and the performances (expected lifetime, round trip efficiency) of LiFePO4 batteries. To this end, 2016, 9, 887 a coupledEnergies electrical-thermal model of a LiFePO4 battery has been developed and validated against experimental tests by Terna (the Italian TSO). The model has been used to simulate PFC operation of a 1-MW/1MWh LiFePO4 BESS deployed by Terna, considering different values of droop and discharge rate
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