Dynamic Modeling and Controller Design of Dual-Mode Cuk Inverter in Grid-Connected PV/TE Applications

This paper presents a dual-mode Cuk inverter for photovoltaic/thermoelectric power applications. A dual-mode Cuk inverter operates in both discontinuous conduction mode (DCM) and continuous conduction mode (CCM), and has the advantages of low ripples of voltage and current at the input and output, medium power density, and step-up/step-down ability, but is difficult to control because DCM and CCM have distinct system dynamics. To overcome this control problem, we propose to use a repetitive controller (RC) with a multiple phase-lead compensator for the dual-mode Cuk inverter. If the RC is applied by itself, the distinct system dynamics may severely degrade its system performance. Thus, in the proposed RC, we mainly use a multiple phase-lead compensator to compensate for the different phase lags of the dual-mode Cuk inverter. To reduce the burden from the RC, we use the dual-mode nominal duty ratio as feedforward control input. We also analyze the boundary of operation modes in the dual-mode Cuk inverter, then provide detailed and practical guidelines to design the control parameters. Experimental results obtained on a 500-W digitally controlled module integrated converter prototype confirmed the effectiveness of the control approach.