Sub/super-synchronous oscillations in renewable energy stations pose significant threats to the secure and stable operation of power systems. While synchronous condensers (SCs) can partially suppress such oscillations

a multi-channel supplementary damping control strategy based on energy storage doubly-fed condenser (ESDFC) is proposed to further enhance oscillation suppression capability. First

a supplementary damping controller (SDC) is designed to target oscillations within specific frequency bands. The current signal at the point of common coupling (PCC) is modulated by the SDC and then fed into the rotor-side control system. This modulation adjusts the reactive power output of the SC

effectively suppressing system oscillations. Second

the controller is divided into multiple channels based on phase compensation deviations introduced by phase-shifting blocks. Each channel is dedicated to suppressing oscillations within a predefined frequency band. Third

the Prony algorithm is employed to extract power oscillation signals for damping ratio calculation

enabling quantitative evaluation of the multi-channel SDC's oscillation suppression performance. Finally

simulations are conducted on both a single-machine system and a renewable energy station system. The results demonstrate that the proposed multi-channel supplementary damping control strategy significantly enhances the ESDFCs to suppress sub/super-synchronous oscillations. This strategy improves the small-signal stability of renewable energy stations

thereby supporting the long-term sustainable development of renewable power generation.