Improved Odd-Harmonic Repetitive Control Scheme for Ćuk-Derived Inverter

Abstract

This article proposes an improved odd-harmonic repetitive controller (IORC) for a Cuk-derived inverter. The IORC is composed of a modified structure of an odd-harmonic repetitive controller (ORC) combined with a proportional-integral (PI) controller and a feedforward controller to achieve a zero steady-state error in the Cuk-derived inverter. The IORC features much larger gains at odd-harmonic frequencies by modification of an existing ORC, so both its convergence rate and transient response become much faster. The added benefit of using the IORC is that it has wider bandwidth at odd-harmonic frequencies, so it is more insensitive to the grid frequency fluctuation. The IORC also adopts a linear phase-lead compensator to compensate for the phase lag of the Cuk-derived inverter. Hence, the IORC can effectively eliminate the odd-harmonic components in the output current of the grid-connected Cuk-derived inverter while using less memory space. However, the distinctive structure of the IORC makes it difficult to guarantee the stability of the overall control system. Thus, in this article, a new stability analysis method is developed for the IORC system, and then a practical design guideline is also provided to obtain the optimal control parameters. Experimental results are presented to validate the proposed controller in the 300-W Cuk-derived inverter prototype.