Research on voltage fluctuation suppression in coal mine AC/DC hybrid distribution network based on directly-coupled energy storage control

Voltage fluctuations on the DC bus caused by load variations are a common issue in coal mine AC/DC hybrid distribution networks. A typical solution involves installing energy storage devices on the DC bus, but existing control strategies often impose excessive stress on the devices and overlook their State of Charge (SOC). This study introduced a control strategy designed specifically for directly-coupled energy storage systems on the DC side of coal mine AC/DC hybrid networks to mitigate voltage fluctuations. The proposed strategy improved the conventional constant power control approach by integrating DC bus voltage feedback, enabling dynamic adjustments to the energy storage output, and reducing system power imbalances. A carrier phase-shift modulation method was applied to minimize current ripple, while a SOC-based sorting mechanism ensured balanced charging and discharging across energy storage submodules. To validate the strategy, a simulation model of the AC/DC hybrid distribution network was built using PSCAD/EMTDC. The results showed significant improvements: DC bus voltage fluctuation rates were reduced by approximately 70% during motor shutdowns and by 90% under sudden resistive load changes. The battery charge/discharge rate was controlled at 0.628C, meeting the fast-response requirements. Further validation was performed through hardware-in-the-loop testing on a real-time digital simulation platform, which demonstrated consistency with the simulation results, confirming the strategy's effectiveness.