Study Of Direct Torque Control System Of An Induction Machinein Closed Loop

In this thesis, a DSP of TI inc.-TMS320F240 is used as a main control chip, and then the author carries out the research on fully digital closed loop Direct Torque Control (DTC) system.In DTC system, the concept of space vector is introduced to analyze and control the AC motor, the electromagnetic torque and flux are calculated and controlled in the stationary coordinate, and the optimal PWM gating signals are generated to control the inverter to acquire high dynamic torque according to the output of the Bang-Bang regulators. It does dot need the complex vector transformation and the simplifying AC motor any more. Instead, it has simple control structure and direct control method, these make the control method simple. DTC system is a high-performance adjustable speed system with fast torque response, but it still has some defects such as torque ripple, speed fluctuate and bad performance in low speed. In this thesis, the characteristics and thedefects of DTC system are detailedly analyzed. A torque-tracking method is used to resolve torque ripple, and a simple mutual lock compensating method aiming to dead time effect influencing system's performance is adopted. In this thesis, a simple switching method of flux estimating is presented to improve low speed performance.Based on the theoretical analysis, the algorithm is implemented by using assemble programs and is validated its feasibility on a set of SDF-4x MG. The result of experimentation in this thesis proves the validity of the mending scheme.