Coordinated Voltage Regulation Strategy for an Energy Storage Integrated Distribution Network in Bidirectional Power Flow Mode

The high penetration of renewable energy sources (RESs) accessed to distribution networks (DNs) causes frequent power exchanges between transmission networks (TNs) and DNs and makes voltage control more difficult. To address this issue, a coordinated voltage regulation strategy for different RES penetration levels is presented in this paper. First, a bidirectional transformer model is established to quantify the voltage control profiles when facing bidirectional power flows. Second, an energy storage system (ESS) management model considering the influence of ambient temperature on batteries is developed and acts as a key regulating approach for voltage profiles. Finally, the multi-level coordinated regulation strategy is proposed by the RES penetration levels to mitigate the voltage fluctuations during bidirectional power flow modes. The simulation analysis based on IEEE-33 system shows that traditional voltage control method, when performing in the bi-directional flow mode, results in over-voltage during 87.5% scheduling time at a RES penetration rate of 150%. But the strategy proposed in this paper can maintain voltage operation within permissible limits with penetration level ranging from 80% to 215%. Furthermore, as the penetration rate escalates, the regulation mechanisms become progressively intricate.