Repetitive controller with phase-lead compensation for cuk CCM inverter

This paper proposes a repetitive controller with phase-lead compensation for an unfolding-type Cuk continuous conduction mode (CCM) inverter operating in the CCM. The Cuk CCM inverter features medium power capacity, step up/down ability, and low input/output current ripples, so it is well suited to distributed power generation systems. To achieve accurate tracking of the reference output current, we make the use of the repetitive controller coupled with a conventional proportional-integral controller and a nominal duty ratio. In developing the proposed controller, we use the average model of the Cuk CCM inverter in the grid-connected case. The two right-half plane (RHP) zeros in the transfer function of the Cuk CCM inverter cause phase lag of the closed-loop system; to compensate for the phase lag, we implement a phase-lead compensation algorithm in the repetitive control scheme. We also provide detailed and practical design guidelines of the control parameters to develop a stable Cuk CCM inverter. Experimental tests using a 500-W Cuk CCM inverter demonstrate the desirable performance of the proposed control approach.