Research On Direct Torque Control System Of Synchronous Motor For Rolling Mill

Electrically excited synchronous motor(ESM) has been widely used in adjustable-speed motor control system with high voltage and high power due to its advantages(adjustable power factor and high efficiency etc.). Vector control or direct torque control is adopted in the synchronous motor drive system at present. The vector control system is mainly based on field oriented control, although the dynamic performance of the motor is compared with scalar control system performance is improved a lot, but because the assumption of the use of too much, and the influence of motor parameters on the control effect is large, so the actual effect is often not ideal.Direct torque control system, is the motor and inverter as a whole, the direct control of stator flux and torque using the hexagonal space voltage vector output inverter, so as to direct torque and fast control, simple process, small amount of calculation, fast response,high accuracy.The main contents of this paper are as follows:This paper presents a mathematical model of synchronous motor in synchronous three-phase static coordinate system and two-phase rotating dq coordinate system; this paper introduces the basic principle of voltage space vector and discuss the relationship between space voltage vector and stator flux; and the synchronous motor direct torque control theory(torque control, stator flux control, excitation current control) was introduced in detail.Secondly, in the research of synchronous motor direct torque control based on the theory, established the simulation model of synchronous motor with Matlab/Simulink software, and loading and removing the load and variable speed constant torque motor to simulate the process in the condition of unit power factor, obtained a series of test curve,Finally, the simulation results are analyzed and compared in detail, which provides a reference for the research of direct torque control of synchronous motor.