Auto-Tuning of Droop Controllers Using Lead-Lag Filters for Grid-Forming Inverters

This paper presents an auto-tuning strategy of the droop control loop in grid-forming inverters. To this end, a lead-lag filter is employed in the P -f droop controller. Such filters, compared to the more commonly used low-pass filters, allow to enhance the stability of the grid-forming inverter besides allowing virtual inertia emulation. To achieve the auto-tuning, the crossover frequency and phase margin of the droop controller are monitored on-line. Key parameters of the lead-lag filter are then adaptively adjusted based on the monitored performance indexes. It is shown that the considered crossover frequency and phase margin can be maintained at desired values, thus ensuring the desired control performance. The solution is particularly valuable in practical scenarios, where it allows to dynamically adapt the controller to potentially unknown variables (e.g., grid impedances, inverter parameters values) that affect control performances. Simulation and experimental tests are presented to demonstrate the proposed solution.