Design an advanced multi-timescale grid-forming control for inverter-based DERs to improve the resilience and stability of power grids with high penetration of power electronics.

PI: Wei Du, wei.du@pnnl.gov

This project is addressing the insufficiency of existing device-level grid-forming controls and developing data-driven adaptive methods to coordinate their response under both physical and cyber adverse conditions.

In FY 2021, the project developed and tested a fault-current-limiting control strategy for inverter-based DERs. The baseline droop control dominates the system behavior during normal operations. However, once a fault occurs, the current-limiting control will be activated to quickly block the pulse width modulation signals and limit the inverter output current with a predefined threshold. Once the fault is cleared by the system protection, the inverter output current will drop below the set limit and the inverter control will automatically return to the droop control mode. The control strategy has been implemented on both the HYPERSIM and RT-LAB platforms in collaboration with Thrust 1 under a small microgrid environment. The control was successfully validated to limit short-circuit current within one millisecond.

In FY 2022, the project will complete the voltage collapse mitigation control design based on the experimental data (dynamical response of the grid-forming photovoltaic inverter to various overload events) obtained in FY 2021. In addition, the project will extend the work to system-level adaptive controls that use the federated reinforcement learning technique to coordinate the grid-forming inverters for improved resilience.

• Goal I: Design and validate DC bus voltage collapse mitigation in the HYPERSIM or RT-LAB platform.
• Goal II: Develop federated RL-based coordination algorithm for several grid-forming inverters in a single microgrid and validate their performance in a simulation environment.

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