Modular interleaved single-phase series voltage injection converter used in small-signal dq impedance identification

Stability analysis of modern three-phase ac power systems is performed using small-signal impedances identified in synchronous reference dq frame. A single-phase series voltage injection is used to perturb ac and dc systems in order to perform small-signal impedance identification. This paper proposes to use interleaved cascaded H-bridge converter to generate a voltage perturbation in series with power system. Special attention is focused on the design procedure, including the selection of inductors and capacitors values, trying to optimize converter´s performance and maximize injection range. The decoupling control is proposed to regulate ac injection voltage, providing robust and reliable strategy to regulate series voltage injection. Furthermore, low bandwidth dc voltage control is included into the control, assuring dc voltage control for each H-bridge module. Analytical expressions, which describe the control procedure, are derived and presented in the analysis. The proposed converter is extensively simulated using switching simulation model and excellent agreement with the developed design procedure is presented. Simulation model and hardware prototype results verify effectiveness of the proposed series voltage injection solution.