An Improved AC System Strength Measure for Evaluation of Power Stability and Temporary Overvoltage in Hybrid Multi-Infeed HVDC Systems

We developed a new strength measure, the hybrid multi-infeed effective short-circuit ratio (HMESCR), for evaluating hybrid multi-infeed high-voltage direct current (MIDC) systems. The HMESCR defines the strength of hybrid MIDC systems with line-commutated converter (LCC) high-voltage direct current (HVDC) and voltage-source converter (VSC) HVDC systems. Unlike previous measures, the HMESCR considers the capacity of VSC HVDC systems to provide reactive power and thus, enhance the strength of AC systems connected at different buses with LCC HVDC systems. To demonstrate how the HMESCR reflects power stability (PS) and temporary overvoltage (TOV), we used MATLAB/Simulink software to perform quasi-steady-state analyses and dynamic simulations. The HMESCR can be used to determine the strength of hybrid MIDC systems.