An Efficient Universal AC/DC Branch Model for Optimal Power Flow Studies in Hybrid AC/DC Systems

This paper introduces a new efficient universal AC/DC branch model, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SADRA</i>, for modelling hybrid AC/DC systems in optimal power flow studies, with provisions of voltage and power controls. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SADRA</i> offers a versatile approach for modelling diverse AC, DC, and AC/DC elements including VSCs and VSC-interfaced elements (including point-to-point and multi terminal HVDC), phase-shifter and tap-changing transformers, and in general, hybrid AC/DC systems, all within a universal model. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SADRA</i> directly links AC and DC grids, and therefore it is able to use conventional AC equations for modelling. Moreover, it is capable of implementing VSC control actions as well. Due to its compact and simple structure, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SADRA</i> is fast and robust. To demonstrate <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SADRA</i>’s performance, versatility, and speed, two large AC/DC systems with 1359 bus and 3125 buses are studied and the results are compared with the existing methods in the literature. It is shown that <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SADRA</i> is a truly universal model, and also successfully implements voltage and power control actions. Additionally, it is demonstrated that in addition to its advantages, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SADRA</i> is as fast or faster than the comparable methods in recent literature, and is up to more than six times faster compared to models with control actions provisions.