Methods for Achieving >75% Instantaneous Inverter-Based Generation Capacity in Transmission Systems (GR-18-02)

Principal Investigators: Dr. Roy McCann, Dr. Lingfeng Wang, Dr. Andrea Benigni

There continues to be large increases in solar and wind generation capacity in the US. There is presently 80 GW of wind energy installed in the US and Southwest Power Pool reported 60% instantaneous wind penetration in March 2018.  California CAISO achieved 50% instantaneous capacity from solar on March 6, 2018. These trends are expected to continue such that with generator interconnect (GI) requests in queue could likely result in >75% instantaneous power from wind & solar inverter–based sources.

This project develops new tools and analysis techniques in order to achieve greater than 75% levels of instantaneous wind and solar power generation.

The research begins with collecting PMU data from a regional 345 kV transmission system (GRAPES collaborator OGE). The PMU data is then correlated and compiled with bus-branch and node-breaker models (SPP) using methods developed in prior GRAPES Projects 14-01 and 15-05. Examples of PMU data with classification of breaker events is shown in Fig. 3. The model is then modified using probabilistic methods for areas most likely to achieve increased solar and wind capacity while identifying weak grid nodes. Weak grid nodes are identified based on:

  • Short circuit ratio (SCR)
  • Weighted short circuit ratio (WSCR)
  • Composite short-circuit ratio (CSCR)
  • Short circuit ratio with interaction factors (SCRIF)

The solar and wind (inverter-based) generation is incrementally increased above the base case and then a sequence of transient and voltage stability assessments (contingency analysis) are executed using Python scripts with PSSE/PowerWorld . The results are then evaluated by an expert system which reports stability concerns. A weighted probabilistic method is then applied to incrementally increase inverter based generation based on most-likely wind-solar expansion points. Transient & voltage stability cases are iteratively executed until a stopping criteria is reached in the expert system (i.e., having reached a specified level of inverter-based generation in excess of 75%).

The research will have benefits that include:

  • The development of algorithms and software tools that enable very high wind and solar inverter-based power generation.
  • Provide solutions to meet NERC objectives for transmission system reliability.
  • Improved financial and economic operations in the electric utility industry with higher utilization of renewable energy and transmission assets (i.e., avoid negative LMP conditions).



Posted on

January 2, 2018

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