Automatic Design of Robust Controllers for Grid-Tied Inverters based on PSO and Kharitonov's Theorem

This paper provides an offline procedure for automatic tuning of robust PI controllers applied to the control of LCL-filtered grid-tied inverters. A particle swarm optimization algorithm is used to tune the control gains based on an objective function, which encompasses frequency and time domain specifications, a limit for the control signal, together with a theoretical assessment of robust stability, by means of Kharitonov's Theorem. Experimental results based on hardware-in-the-loop are provided, confirming that the proposed procedure leads to controls gains that ensure robust stability and suitable grid-injected currents under uncertain grid impedances, complying with the IEEE 1547 Standard and with superior performance when compared to other design alternatives.