Measured Admittance Model for Dynamic Simulation of Inverter-Based Resources Using Numerical Laplace Transform

With confidentiality constraints of detailed control information of inverter-based resources (IBR), black-box models, e.g., admittance/impedance models, obtained from measurements are often used for stability analysis. This paper makes a further inquiry: If stability analysis is possible with admittance models, is it possible to produce time-domain simulation results with admittance models only? One method adopted in the literature is to create a linear state-space model for the entire system by interconnecting components. The requirement for such an approach is that each component's model should be proper. To relax this requirement, the current paper seeks an alternate approach: direct conversion of frequency-domain data to time-domain data via numerical Laplace transform (NLT). To begin with, this paper presents NLT's advantage over inverse fast Fourier transfer (IFFT) using tutorial examples. This is followed by an example of a type-4 wind farm weak grid operation stability analysis and fast simulation using admittance models obtained from measurements. It can be seen that frequency-domain measurements, along with data fitting and NLT, lead to not only stability analysis but also fast time-domain simulation for stability demonstration.

I. Introduction

Higher inverter-based resources (IBR) penetration can lead to many stability issues in real world, e.g., low-frequency oscillation observed in type-4 wind farms with weak grid interconnection [1]–[3] and subsynchronous resonances (SSR) in type-3 wind farms when integrated to series compensation [4].