An AC-DC Power Flow Algorithm for Australian National Electricity Market

This paper develops an open-source ac-dc power flow algorithm designed to analyse complex ac grids with presence of point-to-point and multi-terminal meshed HVDC grids such as the Australian national electricity market (NEM) ac-dc power grid. The Australian NEM ac-dc power grid is a unique integrated power grid that connects five states and territories including an island state through both ac and dc transmission systems. It requires additional degrees of freedom for point-to-point HVDC systems, and diverse control modes of dc converters, which current power flow solvers lack. Thus, the proposed algorithm is customized to address these needs while retaining the adaptability to generic ac-dc power grids. The modeling captures the nonlinear physics of the ac grids, converter stations, and dc grids including a parameterized second-order converter loss model. These losses are estimated through an inherent iterative approach. The ac power grid injections are modeled as controlled quantities operating in either constant PQ or PV control. Further, it regulates voltage in both point-to-point and meshed dc grids. The proposed algorithm is validated with the existing open-source software MatACDC, which is not able to solve ac-dc power flow problems for systems such as the Australian NEM synthetic data model. Numerical simulations provide evidence of the algorithm’s effectiveness in seamlessly solving the Australian NEM synthetic data model by integrating any arbitrary dc system.