Phase shift based equivalent virtual impedance loop for droop-controlled inverters

Virtual impedance (VI) loops are frequently employed in droop based controllers for grid-connected inverters so as to improve the dynamic response which can be very oscillatory when large droop factors are used. They neither yield active power losses nor reactive power demand but they tend to create a drop in the bus voltage. This paper discusses an approach based on phase shifting the reference voltage, which is shown to be equivalent to a virtual impedance loop but does not reduce the bus voltage. Simulation results with MATLAB Simulink are presented.