Voltage and frequency stabilizer based on Fuzzy logic control for three-level NPC converters in stand-alone wind energy systems

The paper proposes a Fuzzy logic approach for controlling three-level NPC converters in stand alone wind energy systems. A key function of this controller is to maintain constant voltage and frequency for customers while maintaining smooth voltage waveform with less filtering requirements. The principle of the proposed Fuzzy controller is based on a modified PI approach in which the error and its integral are utilized as an input for the controller. The direct and quadrature components are used as control variables for the controller. Due to the integrity of the wind energy systems, a complete system is developed including machine-side converter controller and power balancing controller. The entire system is simulated in MATLAB/SIMULINK environment and tested on several load and wind conditions. A real wind speed measurements were imposed to the wind turbine in the system to ensure some realistic responses of the system.