A Simulation Study of Proportional Resonant Controller Based on the Implementation of Frequency-Adaptive Virtual Flux Estimation with the LCL Filter

This paper discusses the implementation of
proportional resonant (PR) current controllers for a Voltage
Source Converter (VSC) with LCL filter which is synchronized
to the grid by virtual flux (VF) estimation with inherent
sequence separation. Even though there is an extensive amount
of literature and studies on the PR current controller for
tracking the current reference of a VSC in the stationary
reference frame, there is no discussion taking into account
voltage-sensorless operation based on virtual flux estimation
with an LCL-filter. Separate estimation of the positive and
negative sequence virtual flux components at the grid-side of the
LCL-filter, well as current sequence separation, using the
Second Order Generalized Integrator-Frequency Locked Loop
(SOGI-FLL) is presented as part of a proposed method. The
LCL filter is characterized in order to reduce the parameter
deviation that might affect the virtual flux estimation. The
stability of the proposed method is analyzed in the frequency
domain while the operation and performance of the proposed
system is verified by simulation studies.