A PI-MPC based Dual-loop Controller for Grid Forming Inverters

A nested grid forming inverter is proposed in this paper. The dual loop structure consists of proportional integral (PI) controlled outer voltage loop and finite control set model predictive control (MPC) based inner current loop. An approximate bode plot developed using describing function method shows high bandwidth of the proposed PI-MPC controller. The dynamic response is demonstrated by simulating a variety of uncertainties such as DC link voltage variation, filter inductor and capacitor alterations, switching of unbalanced as well as non-linear loads and grid connected to islanded mode transition. The proposed controller also results in low voltage THD considering various non-linearities.