Dynamic Model of Back-to-Back Converter for System-Level Phasor Simulation

The power system is expected to evolve rapidly with the increasing deployment of power electronic interface and conditioning systems, microgrids, and hybrid AC/DC grids. Among power electronic systems, back-to-back (BTB) converters can be a powerful interface to integrate microgrids and networked microgrids. To study the integration of such devices into large power systems, a balance between power electronics model fidelity and system-level computational efficiency is critical. In system-level simulations of bulk power systems dominated by synchronous generators, detailed electromagnetic models of back-to-back converters may be unnecessary and also computationally inefficient. This paper focuses on developing a simple phasor model for back-to-back converters that can be easily integrated into powerflow solvers to facilitate large-scale power system simulations. The model is implemented using C⁺⁺ language and integrated into GridLAB-D, an open source software for distribution systems studies, as a potential new capability. The GridLAB-D phasor domain model is validated against the electromagnetic transient (EMT) simulation of the detailed switching model. Simulation results show that the phasor model successfully captures the dominant dynamics of the converter with significantly shorter simulation elapsed time.