Impedance Modeling and Stability Analysis of Grid-Forming Converters for Distribution Networks with Virtual Negative Resistance

The extensive integration of distributed photovoltaic, wind, and energy storage systems in distribution networks exacerbates their low-inertia characteristics. Grid-forming converters with frequency and voltage regulation capabilities are essential for ensuring safe and stable operation. Due to the high resistance-to-inductance ratio in distribution networks, active and reactive power exhibit significant coupling. Virtual negative resistance effectively mitigates this coupling but may induce oscillations. This study develops an impedance model based on harmonic state-space theory to analyze the impact of virtual negative resistance on system stability.