The retirement of conventional synchronous generators and the integration of inverter-based renewable energy sources (RES) are transforming power systems in unprecedented ways. Understanding the impact and consequences of this resource mix transition is crucial to maintaining reliable grid operation. In this regard, this paper examines the impact of increased renewable energy sources on the oscillatory behavior of the U.S. Eastern Interconnection. From our analysis, we found that no single trend could be used to correlate the impact of increased RES penetration levels on the damping ratio of system modes. In fact, the impact of the increased RES penetration levels on a system mode was influenced by the group of synchronous machine models that were replaced with RES machine models. For example, replacing the synchronous generators in Florida significantly increased the damping ratio of the 0.21 Hz mode, whereas the impact was relatively small on the mode when synchronous machines were replaced in the North-eastern areas of the EI.

With an increase in the oscillation events observed in the U.S. Eastern Interconnection (EI), it has become increasingly important to have a good understanding of the EI system oscillatory behavior. However, as compared to the Western Interconnection system (WI), not much work has been done in this regard for the EI system. Therefore, in this paper, a thorough analysis is carried out to identify inter-area modes and their properties for the EI system using a 80000+ bus real EI model. Multi-channel Prony method is used in this paper for estimating system modes and mode-shapes.

The retirement of conventional synchronous generators and the integration of inverter-based renewable energy sources (RESs) are transforming power systems in unprecedented ways. Understanding the impact and consequences of this resource mix transition is crucial to maintaining reliable grid operations. Aiming at this, the paper examines the impact of increasing RESs on the oscillatory behavior of the U.S. Western Interconnection (WI). Two approaches were used in the paper for performing this assessment: measurement- and model-based. In the measurement-based approach, quantile-regression-based correlation analysis was performed using historical data collected from the WI to analyze the impact of increasing RES penetration levels on system modes. In the model-based approach, the 2018 heavy summer operating WI model was used as a base-case to create several use-cases by replacing synchronous machine models with RES machine models in different proportions to analyze the impact of increasing RES penetration levels on the system modes. In this analysis, four scenarios were considered that included system-wide and area-specific increases in RES penetration levels. In the model-based approach, a detailed eigenvalue analysis was also performed to understand the trends observed in the damping ratio of system modes. Our detailed analysis concludes that the increasing RES penetration levels can have a significant impact on system modes. However, no single trend could be identified to correlate the impact of the increasing RES penetration levels on system modes. According to our model-based analysis, this impact was, in fact, dependent on the group of synchronous generators that were replaced by the RES machine models; for instance, replacing synchronous generators in Alberta, that have high participation factors and significantly contribute to the damping of the NS-A mode, had the most impact on the NS-A mode, while the impact on the NS-A mode was little when synchronous generators were replaced in the rest of the WI. Based on this analysis, the authors conclude that the impact of the increasing RES penetration level on a system mode is dependent on the overall dynamics of the evolving system and the damping contribution to that mode by the generators having high participation factors in that mode.

High quality generator dynamic models are critical to reliable and accurate power systems studies and planning. With the availability of PMU measurements, measurement-based approach for model validation has gained significant prominence. Currently, the model validation results are analyzed by visually comparing real--world PMU measurements with the model-based response measurements, and parameter adjustments rely mostly on engineering experience. This paper proposes advanced performance metrics to systematically quantify the generator dynamic model validation results by separately taking into consideration slow governor response and comparatively fast oscillatory response. The performance metric for governor response is based on the step response characteristics of a system and the metric for oscillatory response is based on the response of generator to each system mode calculated using modal analysis. The proposed metrics in this paper is aimed at providing critical information to help with the selection of parameters to be tuned for model calibration by performing enhanced sensitivity analysis, and also help with rule-based model calibration. Results obtained using both simulated and real-world measurements validate the effectiveness of the proposed performance metrics and sensitivity analysis for model validation and calibration.