The upscaling requirements of energy transition highlight the urgent need for ramping up renewables and boosting system efficiencies. However

the stochastic nature of excessive renewable energy resources has challenged stable and efficient operation of the power system. Battery energy storage systems (BESSs) have been identified as critical to mitigate random fluctuations

unnecessary green energy curtailment and load shedding with rapid response and flexible connection. On the other hand

an AC/DC hybrid distribution system can offer merged benefits in both AC and DC subsystems without additional losses during AC/DC power conversion. Therefore

configuring BESSs on an AC/DC distribution system is well-positioned to meet challenges brought by carbon reductions in an efficient way. A bi-level optimization model of BESS capacity allocation for AC/DC hybrid distribution systems

considering the flexibility of voltage source converters (VSCs) and power conversion systems (PCSs)

has been established in this paper to address the techno-economic issues that hindered wide implementation. The large-scale nonlinear programming problem has been solved utilizing a genetic algorithm combined with second-order cone programming. Rationality and effectiveness of the model have been verified by setting different scenarios through case studies. Simulation results have demonstrated the coordinated operation of BESS and AC/DC hybrid systems can effectively suppress voltage fluctuations and improve the cost-benefit of BESSs from a life cycle angle.