This letter, based on measuring the admittance of a black-boxed grid-following inverter (GFLI) at seven distinct operating points to synthesize an operating-point-parameterized state-space model (OPP SSM), presents an efficient method for analytical prediction of the maximum transferable active power (MTAP) injected by the black-boxed GFLI into the grid under any arbitrary grid condition and reactive power injection level. The proposed method obviates the need for repetitive electromagnetic transient time-domain simulations or frequency-domain impedance criteria by gradually increasing active power output until the MTAP is reached. The feasibility of the synthesized OPP SSM for MTAP prediction has been experimentally validated on a power-controlled GFLI, demonstrating its potential for aiding the integration of inverter-based resources in modern power systems.

This paper presents a Python-driven graphical user interface (GUI) explicitly crafted for benchmarking the electromagnetic transient (EMT) models of inverter-based resources (IBRs) across Matlab/Simulink and PSCAD/EMTDC platforms through impedance measurement techniques. The GUI ensures a user-friendly experience, enabling seamless interactions between these platforms while offering advanced visualization of impedance measurement results and associated benchmarking errors. This paper delves into the Python-based implementation that powers these features. Through a series of case studies, the tool's efficacy in benchmarking IBR's EMT models is validated. The benchmarking methodology and corresponding GUI design are extensible to other leading EMT platforms such as DIgSILENT/PowerFactory, PSSE, EMTP-RV, EMTP-ATP, and DSATools TM /SSAT, fostering expansive and holistic research in the stability analysis of the IBR-based modern power systems.

A document by Weihua Zhou . Click on the document to view its contents.

The theoretical maximum power transfer capability of the phase-locked loop (PLL)-based grid-following inverters can be limited under weak-grid conditions due to the non passivity of control loops. This article aims to reveal the passivity violation mechanism and develop passivity oriented feed-forward control to cancel out the negative effects of inner current control and PLL on low-frequency passivity. To this end, the contributions of these control loops and the mutual interactions among individual control loops to inverter terminal admittance are identified using the admittance decomposition technique, based on which the nonpassivity effect of each control loop is canceled out using a point of common coupling voltage feed-forward loop. The effectiveness of the presented control loops passivation method is validated by eigenvalue analysis, simulation studies, and experiments.

As power systems undergo a transformation with increasing inverter-based resources (IBRs), understanding the stability and dynamics of IBR-dominated systems becomes imperative. Though analytical models offer insights into these changes, intellectual property constraints introduce a challenge due to the black-box nature of IBRs, highlighting the importance of frequency-domain-based methods using IBRs’ measured admittance. While simulation environments provide ease in impedance measurement, real-world implementation faces challenges due to the absence of ideal voltage or current sources. This has prompted the use of varied devices, such as power amplifiers and frequency response analyzers, for perturbation generation and injection. Notably, utilizing another measurement inverter as the perturbation source offers a promising approach, despite its limitations such as degrading system stability and prolonging the measurement time. This article introduces an innovative control strategy for the measurement inverter, detailing the effects of abc/dq and dq/abc transformations on the measured admittance. The groundbreaking contributions are the revelations about the admittance contributions of these transformations and the introduction of double phase-locked loops, optimizing both system stability and measurement time.

Due to the capability to perform participation factor analysis and oscillation origin location, the state-space model (SSM)-based eigenvalue method has been widely used for stability assessment of inverter-penetrated power systems. However, possible internal confidentiality of inverters impedes the derivation of their SSMs. In addition, conventional derivation procedure of system SSM can be tedious when complicated transmission network topology and various transmission cables are involved, which may result in a high-order system SSM. To this end, this article presents a black box-based incremental reduced-order modeling framework. The reduced-order SSMs of the inverters and transmission cables are extracted from their dq-domain admittance frequency responses and abc-domain impedance frequency responses, respectively, by the matrix fitting algorithm. Then, the SSM operators proposed in this article recursively assemble the fitted components’ SSMs in the similar manner as the impedance model operator-based recursive components’ impedance aggregation, while preserving the dynamics of individual components. Simulation results show that the presented state-space modeling framework can properly identify the state-space models of black-box devices at component modeling stage, simplify assembling procedure at subsystems/components integration stage, and release computational burden at system participation factor analysis stage.