Permanent magnet synchronous motors (PMSM) have been universally used as variable speed drives due to its characteristics such as small volume, light weight, high efficiency, small inertia and hence high torque / inertia ratio, maintenance free and ease of control, high steady state torque density create possibility of replacing induction machines with PMSMs in industrial drive applications. PMSM are now widely accepted as high performance drives such as industrial robots and machine tools. A novel direct torque control (DTC) scheme incorporating space vector pulse width modulated (SVPWM) inverter, for speed control of PMSM drive has been presented in this paper, which has advantage of fast dynamic response with low ripples in torque and speed response, elimination of current controllers and least dependency on motor parameters. According to the differences in estimated value of torque and stator flux linkage with actual reference value; the stator voltage vectors are directly selected, in DTC to control the speed of motor. Mathematical model of PMSM and proposed DTC scheme is presented here. A simulation model is developed in MATLAB / SIMULINK to judge the various performance parameters.

In recent years, there has been a considerable interest in installation of dispersed generation systems such as wind farms. The DFIG based variable speed wind turbine is the most popular in the growing wind market. This machine can be operate either in grid connected or stand alone mode. The interaction between the wind farm and the grid should be in compliance with the power quality standards. The system uses two back-to-back PWM voltage source converters in the rotor circuit designed as grid side converter (GSC) and rotor side converter (RSC). The vector control strategy is used for both converters. These high frequency switching converters of DFIG will inject additional harmonics in the system, which are increasing with wind speed variations. The presence of non linear load will further inject harmonic current and as a consequence, there is a violation of IEEE-519 power quality standard, and chances of damage of power system equipment may increase. As a solution, Hybrid Active Power Filter; a combination of shunt active filter and shunt passive filter is used in conjunction with non linear load. Indirect current control scheme based on hysteresis controller has been used for controlling of active filter. The SAPF eliminates higher order harmonics while most dominant lower order harmonics are filtered out using passive filter. In this paper the performance of wind driven DFIG feeding non linear load with HAPF is analyzed for steady state and dynamic conditions, using MATLAB/Simulink.

Hybrid active power filter are used for eliminating harmonics in the power system. This paper deals with the hybrid active power filter for non-linear load along with its control scheme. In a hybrid active power filter, the active part is used to filter out the higher order harmonics, while lower order harmonics are eliminated by passive filter tuned for 5^th and 7^th order harmonic frequencies. The combination of shunt active and shunt passive filter considerably reduces the cost and size of active power filter at the same time problem of passive filters are overcome. The effectiveness of proposed filter topology have been verified by MATLAB/Simulink.