FUZZY LOGIC CONTROL OF A WIND DRIVEN DC GENERATOR

FUZZY LOGIC CONTROL OF A WIND DRIVEN DC GENERATOR

The purpose of control is to influence the behavior of a system by changing an input (or inputs) to that system according to a rule or set of rules that model how the system operates. The system being controlled may be mechanical electrical, chemical or any combination of these. A battery charging system employing a Wind Turbine Generator (WTG), with a step-up DC chopper (using a MOSFET) interposed between them, requires a control strategy for the optimum charging of the battery. The charging current to the battery and the output of the generator varies with the wind speed and the state of charge of the battery. Therefore, to maintain maximum charging current to the battery, controller is needed which can vary the duty cycle of the step-up chopper, based on the turbine output (i.e., the torque TL, which depends on the wind speed) and the state of charge of the battery (i.e., the battery voltage, Vb).

Fuzzy logic can make control engineering easier for many types of tasks and also add control where it was previously impractical, as applications such as fuzzy-controlled washing machines. Keeping in mind the inherent advantages of using fuzzy logic, a Fuzzy Logic Controller has been designed to control the duty cycle of the step-up chopper for the reasons mentioned above.
The control rules for the designing were framed based on a simulation study of a wind turbine generator set-up feeding a battery and a load. The scheme with the FLC was simulated in MATLAB using simulink and the built in block sets like the Power System Block sets. The duty cycle was found to vary as expected and the charging current to the battery was found to be optimum in all cases.