Grid-connected kite generator system: Electrical variables control with MPPT

This paper presents a control scheme of a closed-orbit kite generator system (KGS), which is a wind-based energy producing system with a relaxation cycle. Such a system is divided into two main parts: a kite with its orientation mechanism and a power transformation system. Starting from a given closed orbit, the optimal tether´s length rate variation (kite´s tether radial velocity) and the optimal orbit´s period are found. A trajectory-tracking control is developed for the kite´s orientation. The power transformation system controls the kite´s tether radial velocity and transforms the mechanical energy generated by the kite into electrical energy that can be added to the grid. A Matlab/simulink model of the KGS is employed to observe its behavior, and to insure the control of its mechanical and electrical variables. In order to improve the KGS´s efficiency in case of changing wind speed, a maximum power point tracking (MPPT) algorithm is proposed.