Research on an AC Variable-frequency Power Dynamometer Based on PWM Rectifier and Fuzzy Direct Torque Control

The traditional dynamometers consume more fuel or electric energy while working, so they not only waste energy, but also have lower dynamic performance. An AC variable-frequency power dynamometer scheme is presented based on PWM rectifier and fuzzy direct torque control (DTC) of induction motor in this paper. The dynamometer can operate in both motoring and generating states. The bidirectional flow of the energy with unit power factor between the power grids and the dynamometer is realized by voltage-oriented control (VOC) three-phase PWM rectifier. The dynamometer absorbs the energy from the power grids in motoring state, and feeds back the energy generated by the dynamometer to the power grids in generating state. In order to improve dynamic response capability and decrease the torque ripple of the dynamometer, the fuzzy logic idea is adopted based on conventional DTC. The stator flux angle, the stator flux error, and the torque error are reasonably fuzzified into several fuzzy subsets to optimize selection of the voltage vector. The proposed scheme is implemented with a single board microcomputer that uses TMS320LF2407A DSP and intelligent power model (IPM) to validate its feasibility. Experimental results show that the dynamometer has outstanding dynamic and static performance. The application of this novel dynamometer both saves the energy source and decreases the disturbances to power grids caused by rectification