Grid Impedance Estimation and Decoupling through a Series-Parallel Direct-Injection Soft Open Point
The importance of grid impedance in the stability analysis of grid-tied converters is widely acknowledged and studied. However, in meshed distribution grids, it becomes crucial to distinguish feeder impedance from the overall grid impedance to accurately assess power transfer capabilities and overload risks. Traditional research in power flow often treats line or cable impedance as a constant, overlooking its time-varying nature and the necessity for real-time evaluation. This paper presents a novel method to differentiate feeder impedance from total grid impedance, allowing for the estimation of both transformer and feeder impedances. The method uses a series-parallel direct-injection soft open points (SOP) circuit for reactive current injection, enabling precise, real-time impedance measurement without additional equipment. This approach deviates from conventional methods that typically focus on a single grid's impedance by estimating the impedance of both feeders in a two-bus system. It proves particularly effective in separating medium voltage/low voltage (MV/LV) transformers and cable impedance, providing valuable insights for stability and power transfer analysis.
