The shift to net zero energy systems has changed the face of our power grid. Traditional large-scale synchronous generators found inside coal and natural gas plants are being replaced with inverter-based resource (IBR) technologies. This transition to an IBR-dominant power grid introduces new characteristics, altering how our grid operates. Therefore, the role of IBRs has expanded, requiring them to provide a range of essential services to keep our grid reliable, resilient, and secure.

The changing nature of power systems dynamics is challenging present practices related to modeling and study of system-level dynamic behavior. While developing new techniques and models to handle the new modeling requirements, it is also critical to review some of the terminology used to describe existing simulation approaches and the embedded assumptions. This article provides a first-principles review of the simplifications and transformations commonly used in the formulation of time-domain simulation models. It introduces a taxonomy and classification of time-domain simulation models depending on their frequency bandwidth, network representation, and software availability. Furthermore, it focuses on the fundamental aspects of averaging techniques, and model reduction approaches that result in modeling choices, and discusses the associated challenges and opportunities of applying these methods in systems with large shares of Inverter Based Resources (IBRs). The article concludes with an illustrative simulation that compares the trajectories of an IBR-dominated system.

This paper addresses the positive sequence modeling of converter-based sources in commercial transient stability analysis software. A simple and computationally economical model of the converter has been developed while ensuring a reliable representation of the detailed converter behavior. This model has been implemented as a user defined model in commercial positive sequence software such as PSLF. The behavior of the proposed model in positive sequence has the same form as the behavior obtained from detailed point on wave simulation. Tests have been carried out on a three-generator nine-bus equivalent system and the 18,205 bus Western Electricity Coordinating Council system to assess the impact and performance of the converters. The behavior of these converter interfaced generation sources for various system contingencies has been investigated.

In this study, modifications are proposed to the state‐of‐the‐art positive sequence generic converter model in order to capture the small‐signal and large‐signal oscillatory instabilities associated with converters interfaced at low short circuit locations. The performance of the positive sequence model is validated against detailed electromagnetic simulations to lend confidence in this proposed model. Additionally, validation of performance of the model against observed field measurements is also carried out.

A current limiter (CL), which protects virtual synchronous generators (VSGs) from overcurrents, may significantly alter the operation of the VSGs when activated. In this letter, a transient stability analysis of VSGs equipped with quadrature (q-)prioritized CL is performed. This study shows that in addition to the instability caused by the positive feedback of the primary controller, a VSG could become unstable after large disturbances due to the failure of the inner voltage controller. In this study, a stability criterion is provided for the voltage control loop.

This paper reviews potential operational challenges facing hybrid power plants, particularly solar photovoltaic (PV) plus battery energy storage systems (BESS). Real-world operation has witnessed many challenges, e.g., overvoltage at fault recovery, oscillations during solar PV ramping up, large phase angle change during faults, etc. This paper reviews potential operational challenges while focusing on those caused by plant-level control and inverter-level control coordination. To this end, detailed plant-level frequency-power droop control and voltage control are presented. Effect of the communication delay from the plant level to the inverter level is examined. This paper also presents recommendations on how to test hybrid power plants to detect those potential operational challenges in the planning stage. The contribution of the paper is two-fold. (i) A list of operational challenges has been reviewed with several analyzed in detail and demonstrated in case studies. Modeling and testing recommendations to capture those challenges in the planning stage have been presented. (ii) The paper presents the details of IBR controls at both the plant level and the inverter level and reveals the connection between control parameters and operational challenges. Mitigation plans, e.g., control parameter tuning, can be derived based on the insights revealed from this paper.