A new topology was recently developed to drive generators, aiming to avoid power electronic devices directly connected to the grid, and making possible the hybridization of the wind power with other sources. The system is composed by an induction machine with rotor in squirrel cage, and a rotating armature endowed with a three-phase winding that may be fed by a secondary source. The previous purpose was to convert a variable velocity imposed by the wind turbine to the armature in a constant velocity to be developed by the cage rotor, driving a shaft of synchronous generator. This article proposes the use of an induction generator instead of a synchronous one in order to explore the maximum available wind energy (MPPT). The simulation results show that the proposed topology is viable and supports both variations in wind speed and disturbances in power grid.

The major objective of the investigation reported in this article is to demonstrate the feasibility of controlling a Doubly Fed Induction Generator actuating directly on the rotor voltage produced by the Rotor Side Converter, as its reference value may be determined analytically, after definition of the control objective. Two usual objectives are here considered: maximum power extraction from wind (MPPT) and stator reactive power equal to zero. This last objective defines the reference slip to be considered in the formulation of developed power that, jointly with the reactive power equation, forms the system to calculate the rotor reference voltages. The process is completed by specifying the desired dynamical response. Thus, the angular velocity of the rotor should quickly reach its reference value, which requires maximal power acceleration at the beginning, but respects the restriction that no overshoot should be allowed. This is achieved by means of a constrained optimization process solved in real time. Following recent trends, only measurements obtained from stator (voltages and currents) sensors are used. This way, angular velocity and rotor currents are estimated in real time. An algorithm for inductance estimation is also included, which prevents deviations of nominal values that could lead to false reference voltages.

In coastal cities, the most visited tourist spots are the beaches. However, this leisure place is forgotten by the public power in relation to the accessibility infrastructure for wheelchair users. Several entrances make it difficult for the wheelchair user to access the beach, among them, the ease of the traditional wheelchair to get stuck in sandy soil. Due to rains and tides, the layout of sand banks tend to constantly change. As a solution, this paper proposes an electric traction vehicle powered by photovoltaic energy, mechanically and electrically adapted to facilitate the access of the wheelchair user, aiming for accessibility and independence. In order to overcome the sand obstacles and improve the usability of the vehicle, the power sources must be correctly designed to provide enough power to the motors and autonomy for wheelchair users. The electric part of this vehicle is composed by photovoltaic modules, a power converter, a MPPT based battery charge control, a battery bank and DC motors. This paper presents the vehicle power system design, control design and analysis of operation points through simulation results. Some experimental results are also presented to validate the simulations.