Discrete-Time Repetitive Control of Flyback CCM Inverter for PV Power Applications

In this paper, a discrete-time repetitive controller (RC) is proposed for a flyback inverter operating in continuous conduction mode (CCM), which has a simple structure, low cost, and high efficiency. Conventional controller results in poor control performance due to the effect of the right-half-plane zero in CCM operation. To achieve accurate tracking performance and disturbance rejection, the RC is developed and applied to the flyback inverter in CCM operation. In the RC scheme, a low-pass filter is used to allow tracking and rejection of periodic signals within a specified frequency range. A phase lead compensator is also used to compensate for the effect of the closed-loop system dynamics. The stability of the closed-loop system is derived, and the zero tracking error is achieved. Numerical simulations validated the proposed control approach, and experimental tests using a 200-W digitally controlled module-integrated converter prototype confirmed its feasibility.