Impedance Circuit Model of Grid-Forming Inverter: Visualizing Control Algorithms as Circuit Elements

The impedance model is widely used for analyzing power converters. However, the output an external representation of a converter system, i.e., it compresses entire dynamics into single transfer function with internal details interaction between states hidden. As result, there are no programmatic routines to link each control parameter system dynamic modes and show interactions among them, which makes designers rely on their experience heuristic interpret its implications. To overcome these obstacles, this article proposes new modeling tool named as circuit model, visualizing closed-loop discrete elements rather than all-in-one function. It can reveal virtual essence all parameters at different locations and/or within frequency bandwidths, coupling effects. A grid-forming voltage source inverter investigated example, considering controller, current delay, voltage/current dq-frame cross-decoupling terms, output-voltage/current feedforward control, droop controllers, three typical impedances. proposed validated by frequency-domain spectrum measurement time-domain step response in simulations experiments.