Interoperability Specifications for Multi-Vendor Converter-Dominated Grid: a Robust Stability Perspective

Stability of multi-vendor power electronicsdominated grids requires proper specifications for converters interoperability, e.g. tuning boundaries for the converters’ control loops to be respected by all vendors. The confidentiality and variety of implementation of the converters’ control system by different vendors and the nonlinear dynamics of power converters make this task arduous. This paper formulates this research question as a robust stability problem, embedding frequency-dependent uncertainties in the converter control systems and analytically quantifying the amount of uncertainty able to warranty the power grid stability. Grid following converters are considered and modeled with a nonlinear grey-box approach, in contrast with conventional small-signal black-box models which suffer from inaccuracy when their operating point deviates from the nominal one. This paper also demonstrates both analytically and with Hardware-In-the-Loop (HIL) experiments that different converters operating points (e.g. active power injections, ac bus voltages) radically affect their stability, empathizing the necessity of nonlinear converters models to realize accurate power grid stability analyses.