Passivity-based control of cascaded multilevel converter based D-STATCOM integrated with distribution transformer

•The structure of a cascaded multilevel converter (CMC) based D-STATCOM connected to a group of taps on the primary windings of a transformer is proposed in this paper.•The winding currents distribution and compensation capacity constraint are analyzed in detail by steady-state phasor diagrams.•The nonlinear PBC method is introduced to control the CMC based D-STATCOM to enhance the robustness and simplify the controller design of the proposed system.

This paper proposes a novel adaptive passivity-based control (PBC) of cascaded multilevel converter based D-STATCOM integrated with distribution transformer for medium voltage reactive power compensation. A cascaded multilevel converter-based D-STATCOM is connected to a group of taps on the primary windings to form an integrated structure. The power transformer is used as coupling transformer at the same time. The structure is helpful to achieve a flexible connection point voltage and improve the capacity utilization of the transformer. The winding currents distribution and compensation capacity constraint are analyzed in detail by steady-state phasor diagrams. A nonlinear passivity-based control is designed to achieve reference currents tracking. Furthermore, an adaptive control is also presented to attenuate the effects of parameters perturbation on the performance of the D-STATCOM. Finally, down-scaled prototype experimental results are provided to verify the steady and dynamic performances of the integrated D-STATCOM with PBC for reactive power compensation.