Optimal control design for proportional-resonant controllers with active damping applied to grid-connected converters

The main objective of this paper is to provide an automatic procedure to design optimal proportional-resonant controllers with active damping applied to the current control of LCL-filtered grid-connected converters subject to parameter uncertainties. In order to achieve that, first the converter is described by means of a polytopic model with two vertices. Then, the control gains are written as decision variables of an optimization problem, where the cost function to be minimized is written in terms of quadratic errors and takes into account grid parameter uncertainties. A particle swarm optimization is then used to find, in an offline procedure, the active damping and the proportional-resonant gains in a single step procedure, avoiding iterative designs based on trial and error which can be time consuming and largely dependent on the designer expertise. The proposed procedure leads to grid current responses with superior performance than the one obtained with a conventionally designed controller, demanding less human-machine iterations and with a higher capability of providing robust and optimal responses