Wind power generation system mainly consists of a wind power generator, a battery group to store generated electricity, a controller unit to transmit maximum power to load and an inverter system to supply power to AC load.
Generally, small wind power system is controlled by maximum power point tracking method, whereby the output current is controlled so that the wind power generation system can be operated at the maximum power point of the wind turbine regardless of the changing wind speed when the wind power generation system is operated independently. This method is suitable for systems where the rotational speed of the wind turbine varies sensitively with the change of wind speed due to the small inertia moment.
Hence, present papers introduce a method for maximum power output without a control circuit in a small wind power generation system. It is a driving method that approximates the active power curve of load to the maximum power curve of the wind turbine for maximum power operation by changing the generator’s electromotive force coefficient and the inductance of the two-winding generator. In wind power generation systems with two-winding generators of great inductance, however, the load power characteristics have saturation characteristics with respect to the number of turns. Therefore, the inductance alone is not enough to approximate the load power characteristics to the maximum power curve of wind turbines.
Kim Yong San, a researcher at the Faculty of Electrical Engineering, has solved scientific and technological problems arising in providing maximum power point operation of wind turbines using the two-winding generator and electromotive force coefficients in permanent magnet generators connected with wind turbines.
He theoretically analyzed how the power output of load depends on the generator’s electromotive force coefficient and the inductance of a two-winding generator, and proposed a method for determining the reasonable inductance and electromotive force coefficient that brings the generator’s effective power characteristics depending on the rotational speed closest to approach the maximum power curve of wind turbines.
Through the simulation analysis using MATLAB, he confirmed that the power characteristics of load could be operated near the maximum power curve of wind turbines.
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