Research On Induction Motor Direct Torque Control System

Direct Torque Control technology, after the development of vector control AC motors is up to a high performance frequency control technology.It uses space vector control method and motor torque as the control object observes stator flux and torque directly in the stator two-phase stationary frame, and then select the appropriate stator voltage space vector by hysteresis controllers output signals, in order to control stator flux and torque. Induction motor speed control system based on direct torque control has simple structure, fast torque response, low dependence on motor parameter. The technology has been a successful example in the field of electric locomotive traction applications at home and abroad. Traditional direct torque control programs, though simple, quick response, but because of the voltage model of stator flux observer based on the pure integrator, the inevitable result of DC disturbances will cause the pure integrator error accumulation so that integrator saturation, leading to observations decreased accuracy, low speed situations, or even erroneous results.To improve the accuracy of the stator flux observer, this paper comparison the stator flux observer based on pure integrator model and the traditional limitations of low-pass filter model, proposed a stator flux observer based on modified low-pass filter. In the proposed improved low-pass filter model,It gets induction motors synchronous speed by accurate observation of the frequency the stator current, and adjusts the low-pass filter cutoff frequency by the induction motors synchronous speed, in order to improve the accuracy of the syator flux observer.To verify the correctness and validity of the above flux observer model of induction motor direct torque control system in this paper, the system was simulated under matlab/simulink platform. The simulation results shows that the design of the stator flux model can accurately estimate the induction motor stator flux effectively, and has strong anti-interference ability, good low speed performance and dynamic response.In this paper,I have motor control ASIC TMS320LF2812A digital processor produced by TI as core, high-performance intelligent power module (IPM) as the inverter device, the 5.5kW induction motor as the control of the object making the induction motor direct torque control system hardware test platform, realized digital control of the direct torque control of induction motor variable frequency speed regulation system. Finally, The author concluded the system's inadequacies, and provided the future research recommendations.