Improved Direct Torque and Reactive Power Control of a Matrix-Converter-Fed Grid-Connected Doubly Fed Induction Generator

Doubly fed induction generator (DFIG) is the most popular variable-speed generator for wind energy application due to its superior performance, lower cost, and control flexibility. Instead of back-to-back converters, matrix converter (MC) can be a good alternative for connecting the DFIG rotor to the grid. This paper presents a novel lookup-table-based hysteresis controller for a variable-speed constant-frequency DFIG supplied from a direct MC. For the machine control, a modified direct torque controller (DTC) with reactive power and speed control in the outer loops has been used. The reactive component of the MC input current has been also controlled using a hysteresis controller considering all active switch states based on estimated input current and load power factor. This upgradation of the input current control switching table reduces the distortion in the grid-supplied current waveform. Overall, the performance of the DFIG with MC is experimentally shown to be superior while using the proposed controller compared with a standard DTC-based control or space-vector-pulsewidth-modulation-based vector control of MC-fed DFIG reported in the literature.