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

Traditional analytical approaches for stability assessment of inverter-based resources (IBRs), often requiring detailed knowledge of IBR internals, become impractical due to IBRs' proprietary nature. Admittance measurements, relying on electromagnetic transient simulation or laboratory settings, are not only time-intensive but also operationally inflexible, since various non-linear control loops make IBRs' admittance models operating-point dependent. Therefore, such admittance measurements must be performed repeatedly when operating point changes. To avoid time-consuming and cumbersome measurements, admittance estimation for arbitrary operating points is highly desirable. However, existing admittance estimation algorithms usually face challenges in versatility, data demands, and accuracy. Addressing this challenge, this letter presents a simple and efficient admittance estimation method for black-boxed IBRs, by utilizing a minimal set of seven operating points to solve a homogeneous linear equation system. Case studies demonstrate this proposed method ensures high accuracy across various types of IBRs. Estimation accuracy is satisfying even when non-negligible measurement errors exist.