Research and Performance Verification of a Flexible Interconnection Architecture for Distribution Networks Based on a Hybrid Series–Parallel Structure

The “closed-loop design, open-loop operation” scheme traditionally adopted by distribution networks results in limited power-flow regulation capability and insufficient supply reliability. Existing flexible interconnection solutions mostly employ AC–DC–AC back-to-back converter architectures, which suffer from high cost, large footprint, and low efficiency. To address these issues, this paper proposes a flexible AC controllable interconnection device based on a hybrid series–parallel structure. The device couples series voltage injection through cascaded H-bridge (CHB) submodules with parallel feeding through a multi-winding transformer: the series side synthesizes a controllable AC voltage source from the cascaded submodules, enabling independent regulation of the active and reactive power of the line, while the parallel side supplies isolated power to the DC sides of all submodules via the multi-winding transformer, thereby fundamentally resolving the DC-side energy-balance problem of series-connected converters. A decoupled vector control strategy in the dq synchronous rotating reference frame, together with an individual-phase control scheme, is developed, and the device supports both interconnected and islanded operation modes. An RTDS simulation model is established on the basis of 10 kV/5 MW rated parameters, and three groups of tests are conducted: steady-state active power control, steady-state reactive power compensation, and dynamic active power control. The simulation results show that the steady-state active power control error is below 1.5%, the reactive power compensation error is approximately 5%, and the dynamic power step response time is 12–13 ms, with the power settling at the target value within 30 ms, verifying the technical feasibility and effectiveness of the proposed scheme for power-flow regulation and reactive power compensation in distribution networks.