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A Detailed Analysis of the Impact of Increasing Inverter-Based Resources on the Oscillatory Behavior of the Western Interconnection
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  • Urmila Agrawal ,
  • Renke Huang ,
  • Tawsif Ahmad ,
  • Jim Follum ,
  • Ning Zhou ,
  • Yousu Chen ,
  • Pavel Etingov ,
  • Shaobu Wang ,
  • Zhenyu Huang
Urmila Agrawal
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Renke Huang
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Tawsif Ahmad
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Jim Follum
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Ning Zhou
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Yousu Chen
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Pavel Etingov
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Shaobu Wang
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Zhenyu Huang
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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.