A new generalized state-space averaged model, control design and stability analysis for three phase grid-connected quasi-Z-Source inverters

A comprehensive dynamic model of the three-phase grid-connected quasi Z-Source inverter (qZSI) with LCL filter is presented based on the generalized state-space averaging (GSSA) method. The developed model mathematically describes (i) the dynamic interaction between DC and AC side variables of converter and (ii) good dynamical precision that ensures a good description of the input–output dynamics, as well as the internal. Then, based on the developed model, a cascaded PI controller by nesting multi-control loops to regulate DC side capacitor voltage and inductor current is proposed. The PI controllers determine the grid and inverter current references in the d- and q-axes by regulating the DC side capacitor voltage. An LMI approach for stability analysis of the proposed controller, reliability calculations and switching losses are investigated. The accuracy of the developed qZSI inverter model and the effectiveness of proposed controls are verified by time-domain simulations of a study system in the MATLAB/SIMULINK environment and hardware-in-the-loop (HIL) simulation.