| Summary: | 碩士 === 國立臺灣科技大學 === 電機工程系 === 105 === The thesis aims to develop bidirectional three-phase induction machine drives for dynamometer with the feature of energy recovery when the electric motor under test serves as a prime mover. The bidirectional power conversion consists of power converter, dc-link and power inverter. The three-phase induction machine is operated either in motor or generator mode, corresponding to the motoring or braking operation of the electric motor under test. Under motor mode, indirect rotor field-oriented control is introduced. The feedback signals of three-phase current, rotor position and speed are obtained for current vector as well as speed closed-loop controls. Whereas, for induction generator under grid-connected operation, the reversed three-phase power conversion and digital phase-lock loop are designed to calculate the phase angle of power grid to facilitate synchronous frame transformation for the dc voltage and current closed-loop controls.
System simulation is given using Matlab/Simulink. A 32-bit digital signal processor, TMS320F28335, is adopted as the control core. Since control strategies are mostly implemented by software program, circuit components are reduced largely. Experimental results show that when the three-phase induction machine is operated in motor mode at 2000 rpm, the power output from the induction motor is 2 kW with the peak phase current and total harmonic distortion (THD) of 12.80 A and 4.31%, respectively, on the motor input; the corresponding values on the grid side are 7.44A and 5.14%. The overall efficiency of the motor drive reaches 76.50%. While in generator mode at 2000 rpm, the mechanical power input to the induction generator is 2 kW, the peak generator phase current and THD are 12.83A and 3.04%, respectively. The corresponding values on the grid side are 5.82A and 4.57%. The overall efficiency of the generator system is 72.69%. The experimental results verify the feasibility of the proposed system.
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