Optimal Sizing of Battery Energy Storage to Enable Offshore Wind Farm Black Start Operation

The goal of transitioning toward 100% renewable energy sources (RES) poses serious challenges to the black start service in electrical power systems. In the instance of a blackout, black start units must restore the power. Conventional black start sources are often taken out of operation to accommodate a larger share of RES and this jeopardises the resiliency of the grid. To replace conventional black start units, offshore wind farms (OWFs) can become future black start providers. However, a black start unit must meet stringent technical requirements, and due to the variable power output of OWFs, it may be challenging to meet these requirements without external support. Therefore, battery energy storage systems (BESSs) are a promising solution to support OWFs to satisfy black start requirements. In this paper, a probabilistic method is applied to determine the optimal BESS power output to support the OWF during black start operation. The considered black start technical requirements are taken from the British Transmission System Operator (TSO). The wind generation behavior is approximated with a Weibull distribution, and BESS power output is estimated considering a worst-case scenario logic. Finally, results are validated with a series of load-flow simulations to verify the time series generation of an OWF. The analysis conducted shows that the required power output from a BESS is dependent mainly on the size of the OWF and the availability requirement dictated by the TSO.