Stability Boundary Analysis and Design Considerations for Power Hardware-in-the-Loop Simulations of Grid-Following Inverters Under Weak and Stiff Grids

This technical paper presents practical design guidelines to ensure stability in power-hardware-in-the-loop simulations for an experimental AC microgrid. Using an OPAL-RT TECHNOLOGIES platform, the study analyzes a PHIL setup with two parallel three-phase grid-following inverters (with LCL filters) and experimentally maps stability boundaries, showing how stability depends on the utility-grid short-circuit ratio and the feedback current-filter cutoff frequency. The results demonstrate smooth transitions across operating conditions and provide validated modeling recommendations for secure, reliable PHIL execution in microgrid applications.