Ripple Correlation Control: An Extremum Seeking Control Perspective for Real-Time Optimization

This paper links the theory of ripple correlation control (RCC) and extremum seeking control (ESC) with emphasis on application in a solar photovoltaic (PV) system. ESC has been well-established in the automatic control literature to find the extremum of an objective function. The RCC theory and applications have been developed in the power electronics literature for real-time optimization. Both ESC and RCC are reviewed and discussed. RCC is formulated in a similar approach to ESC, but distinct based on the source of perturbations-mainly external perturbations with ESC and inherent ripple with RCC. While some recent ESC implementations utilize inherent perturbations, RCC uses high-frequency perturbations in power electronics systems not currently utilized by ESC. The formulation and equivalencies presented here are intended for future research in both methods which can benefit from existing research for further development in theory and applications. Shared aspects that include stability and convergence characteristics are discussed. RCC formulation from an ESC perspective is then applied for maximum power point tracking of a solar PV panel, using high-frequency inherent ripple in power electronics. This RCC formulation is confirmed to have high tracking effectiveness and fast convergence.