This paper deals with the direct torque control (DTC) of BLDC motor drives by using particle swarm optimization technique. BLDC motors have wide variety of advantages like higher speed ranges, higher efficiency, and better speed versus torque characteristics. Direct torque control (DTC) is one of the efficient methods used in variable frequency drives to control the BLDC motor. DTC offers many advantages like fast torque response, no need of coordinate transformation and less dependence on the rotor parameters. In DTC, the estimated flux magnitude and torque are compared with their reference values. The reference torque is generated from the output of the speed regulator (PI controller).Tuning PI parameters (Kp, Ki) are essential to DTC system to improve the performance of the system at low speeds. In conventional PI controller, the performance of the motor may cause unexpected torque disturbances. Particle swarm optimization (PSO) is proposed to adjust the parameters (Kp, Ki) of the speed controller in order to minimize torque ripple, flux ripple, and stator current distortion.The simulation results of BLDC drive employing conventional PI and PSO based PI controllers is compared and evaluatedunder various load disturbances in the MATLAB/simulink environment. KEYWORDS:BLDC motor, DTC, PI, PSO, MATLAB/simulink. I.INTRODUCTIONCurrent researches have been tailored towards developing brushless direct current motors, which are fast becoming alternatives to the conventional dc motor types. The Brushless Direct Current (BLDC) motors are gaining grounds in the industries, especially in the areas of appliances production, aeronautics, medicine, consumer and industrial automations and so on. The BLDC motors are typically permanent magnet synchronous motors that are well driven by dc voltage. Some of the advantages of a brushless dc motor over the conventional brushed dc motors are better speed versus torque characteristics, high dynamic response and high efficiency. Another vital advantage is that the ratio of torque delivered to the size of the motor is higher, and this contributes to its usefulness in terms of space and weight consideration. There are several methods to vary the speed of a BLDC motor over a wide range. Techniques for control of current include vector control, predictive control, dead-beat control, and direct torque control. The most modern technique is direct torque control method (DTC). The DTC offers many advantages like fast torque response, no need of coordinate transformation and less dependence on the rotor parameters. The conventional PI (proportional, integral) control method is widely used in motor control system due to the simple control structure and easiness of design. However tuning the parameters of PI controller is a difficult task. To enhance the capabilities of traditional PI parameter tuning techniques, several intelligent approaches have been suggested such as genetic algorithms (GA) and the particle swarm optimization (PSO).Particle Swarm Optimization is one of the modern a...

This manuscript presents the modeling and simulation studies of grid connected Doubly Fed Induction Generator (DFIG) based wind farm. In current scenario, DFIG is used for the large scale wind energy systems. DFIG is high sensitive for the faults on the system due to termi-nals of stator directly fed to the grid. In this work the dynamic response of the proposed system under varying wind speeds and three transi-ent faults at different locations for different durations are studied.