An Efficient Method to Estimate Admittance of Black-boxed Inverter-based Resources for Varying Operating Points

Admittance frequency responses of inverter-based resources (IBRs) are typically measured in the electromagnetic transient simulation or lab environments when their internal structures and parameters are unknown. Nevertheless, such ad?mittance measurements must be performed repeatedly when the operating point changes, since various non-linear control loops make the IBRs’ admittance models operating-point dependent. To avoid the time-consuming and cumbersome measurements, this letter presents a simple and efficient admittance estimation method for black-boxed IBRs, where the admittance at any arbitrary operating point can be estimated using as few as seven measured admittance data points. Case studies demonstrate that the proposed approach is efficient on various types of IBRs, including both grid-following and grid-forming inverters. The estimation accuracy is satisfying even when non-negligible measurement errors exist.