Next-Generation Modeling for Inverter-Based Distributed Energy Resources
This 2021 project developed a circuit-based analytical model for inverter-based distributed energy resources (DERs) to improve power system simulations and operational planning.
Challenges
Traditional power flow models fail to accurately represent inverter-based generation, leading to unstable simulations and inaccurate planning.
Existing DER models struggle with convergence issues, particularly in systems with high penetration of renewable generation.
Grid operators need better analytical tools to model real-time inverter behavior and its impact on system stability.
Approach (Methodology & Analysis)
1. Development of an Inverter-Based Distributed Generator (IBDG) Model
Created an analytical model for inverter-based distributed generation to better represent steady-state behavior in power flow simulations.
Extended prior work by incorporating overcurrent limits and Volt/VAR control, ensuring compliance with IEEE 1547 regulations.
Used equivalent circuit modeling techniques to construct a first-order continuous model, improving convergence for large-scale power flow analysis.
2. Implementation of Improved Volt/VAR Control for Inverters
Developed a piecewise continuous function to better model reactive power support under different voltage conditions.
Avoided traditional PV/PQ switching algorithms, which are known to cause convergence issues in Newton-Raphson solvers.
Applied homotopy and relaxation techniques to ensure robust simulation performance across various grid conditions.
3. Performance Validation and Simulation Testing
Compared the proposed model against GridLAB-D inverter models and validated results using synthetic electromagnetic transient simulations in EMTP-RV.
Evaluated three PG&E prototypical distribution feeders, assessing the impact of different inverter placements and penetration levels.
Key Findings & Insights
More Accurate Representation of Inverter-Based Generation in Power Flow Analysis
The model correctly accounts for inverter control modes, overcurrent limits, and Volt/VAR response, ensuring better alignment with real-world inverter behavior.
Improved Voltage Profiles Compared to Traditional Models
GridLAB-D models overestimated inverter contributions, leading to potential misrepresentations of system stability.
The new model provided voltage magnitudes that were closer to the actual steady-state behavior, reducing overvoltage and undervoltage errors.
Better Grid Planning for High-DER Systems
The model allows utilities to simulate realistic inverter behavior, supporting better planning decisions for high-renewable energy distribution networks.