A current-limiting droop controller is proposed#R##N#for single-phase grid-connected inverters with an#R##N#LCL filter that can operate under both normal and faulty#R##N#grid conditions. The controller introduces bounded nonlinear#R##N#dynamics and, by using nonlinear input-to-state stability#R##N#theory, the current-limiting property of the inverter is analytically#R##N#proven. The proposed controller can be operated#R##N#in the set mode to accurately send the desired power to the#R##N#grid or in the droop mode to take part in the grid regulation,#R##N#while maintaining the inverter current below a given#R##N#value at all times. Opposed to the existing current-limiting#R##N#approaches, the current limitation is achieved without external#R##N#limiters, additional switches or monitoring devices#R##N#and the controller remains a continuous-time system guaranteeing#R##N#system stability. Furthermore, this is achieved#R##N#independently from grid voltage and frequency variations,#R##N#maintaining the desired control performance under grid#R##N#faults as well. Extensive experimental results are presented#R##N#to verify the droop function of the proposed controller and#R##N#its current-limiting capability under normal and faulty grid#R##N#conditions.
['Qing-Chang Zhong', 'George C. Konstantopoulos']
Current-Limiting Droop Control of Grid-connected Inverters