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