Conventional droop control methods cannot achieve accurate proportional reactive power sharing, due to the mismatch of components, system disturbances, etc. In this paper, an uncertainty and disturbance estimator (UDE)-based robust droop controller is proposed to address these problems. As a result, the model nonlinearity and uncertainty (e.g., power angle and uncertain output impedance) and system disturbances (e.g., variations of output impedance, load change, and fluctuating dc-link voltage) can be estimated and compensated. Experimental results from a single-phase system with two inverters are provided to demonstrate the effectiveness of the proposed strategy. In order to further demonstrate the advantage and flexibility of the proposed UDE-based control strategy, simulation results from a three-phase system with two inverters are presented with comparison to a robust droop control strategy reported.
- Droop control
- inverters in parallel operation
- proportional load sharing
- robust droop control
- uncertainty and disturbance estimator (UDE)