Kite Generator System Modeling and Grid Integration

This paper deals principally with the grid connection problem of a kite-based system, named the “Kite Generator System (KGS).” It presents a control scheme of a closed-orbit KGS, which is a wind power system with a relaxation cycle. Such a system consists of a kite with its orientation mechanism and a power transformation system that connects the previous part to the electric grid. Starting from a given closed orbit, the optimal tether´s length rate variation (the kite´s tether radial velocity) and the optimal orbit´s period are found. The trajectory-tracking problem is not considered in this paper; only the kite´s tether radial velocity is controlled via the electric machine rotation velocity. The power transformation system transforms the mechanical energy generated by the kite into electrical energy that can be transferred 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 slow changes of wind speed, a maximum power point tracking (MPPT) algorithm is proposed.