A Novel Control Scheme for Soft Open Points with Battery Energy Storage Systems

Soft Open Points (SOPs) are advanced power electronic devices designed to provide flexible power flow control between interconnected buses in electrical networks. Integrating a Battery Energy Storage System (BESS) with an SOP allows for enhanced dynamic power flow control. The SOP offers spatial flexibility, while the BESS provides temporal flexibility. Conventionally, BESSs are interfaced with SOPs through a DC-DC converter. This paper proposes a novel control scheme based on DC-link power balance and droop control. This scheme eliminates the need for a DC-DC converter and allows one of the SOP converters to directly control the BESS operation. To validate the proposed approach, the system is simulated in MATLAB/Simulink and integrated into the IEEE 33-bus radial distribution system by connecting buses 9 and 29. The simulation results demonstrate the control scheme's effectiveness in enabling the SOP to match the additional load requirements. It also effectively manages the BESS operation under varying load conditions. While the SOP consistently facilitates spatial power transfer, the BESS provides temporal flexibility. It charges when the additional load is below 200 kW and discharges once this threshold is exceeded. The control scheme's validity is demonstrated by dynamically adjusting the DC-link voltage according to the additional load and BESS voltage. Overall, the system achieves stable operation, resulting in viable, simpler, and more cost-effective integration between two relevant devices in modern electrical networks.