Robust Control of Grid-Tied Inverters using Particle Swarm Optimization and Linear Matrix Inequalities

This paper provides a new design procedure for robust current controllers applied to LCL-filtered grid-tied inverters suitable for the integration of renewable energy sources. The design takes into account the digital implementation delay, multiple resonant controllers and operation under uncertain grid impedance. The procedure is based on the optimization of an objective function that allows to get a good trade-off between the settling of transient responses and rejection of disturbances. A particle swarm algorithm is used to find the optimal control gains and, differently from other works, here the robust stability of the closed-loop system under uncertain parameters is theoretically certified by means of linear matrix inequalities. Experimental results are shown, confirming that the closed-loop system with gains obtained by the proposed procedure presents a good tradeoff between robustness and performance, with suitable transients and grid currents with low harmonic content, complying with requirements from IEEE 1547 Standard, becoming a useful robust control design alternative for power converters in the distributed generation scenario.