Research On Variable Frequency Adjustable Speed System Based On DSP

With the development of modern power electronics technology, AC motor drive system has a trend to replace the DC motor drive system. The FOC (field - oriented vector control) and the DTC (direct torque control) are the high performance control strategies, which is comparable to the DC motor control strategies. The open-loop Constant V/F control strategy dues to its good performance and simple control programs, So far as the popular asynchronous motor speed control method.In this paper, TMS320LF240 digital signal processor that is selected as the main CPU in the system realizes the adjustable speed system. The work contains the following aspects. Firstly, analysis the squirrel-cage induction motor VVVF characteristics. The principle of Boost converter of wide range input is analyzed in the thesis, then, the main parts of the hardware are designed and selected. With the Boost converter prototype developed in the lab, some experiments have been done. The experimental results prove that the PI strategy is feasible and the system has good steady and dynamic performances.The thesis clarifies the SVPWM theory. Applying the SVPWM control technology to the inverter control system will increase the availability of volts d.c under the same waveform conditions compared with SPWM. The frame of system and the control circuit are designed. The software of the control system is compiled with assembly language and the principle of control program with a flow chart is introduced in detail. The simulation model based on the Matlab/Simulink platform is established. The simulation results showed inverter circuit parameters selected accuracy and the good performance of Constant V/F strategy. At the same time of developing engineering sample product, the whole system's experiment platform is established. Experimental results show that the control system is effective and reliability.