1. The basic idea of direct torque control
Direct torque control is another high-performance induction motor control mode developed after vector control. This technology solves the above-mentioned shortcomings of vector control to a great extent. With the novel control idea, concise system structure , Excellent dynamic and static performance has been rapid development.
The basic idea of direct torque control is to control the motor stator flux linkage by controlling the instantaneous input voltage of the motor under the condition of accurately observing the spatial position and size of the stator flux and maintaining the amplitude substantially constant and accurately calculating the load torque Instantaneous rotation speed, change its instantaneous slip on the rotor, so as to achieve the purpose of direct control of the motor output.
Direct Torque Control directly analyzes the mathematical model of AC motor in the stator coordinate system to control motor flux linkage and torque. It eliminates the need to equate an AC motor to a DC motor, eliminating the need for many complex calculations in vector rotation transformations; it does not require emulation of DC motor control or simplifies the mathematical model of AC motors for decoupling.
2. Characteristics and Application of Direct Torque Control
Different from vector control, direct torque control has the advantages of strong robustness, good dynamic response of torque, simple control structure and simple calculation. It solves the problem of complex structure and large amount of calculation in vector control. However, as a new theory and new technology born soon, there are some imperfections and immatures naturally. First, in the low speed zone, a series of problems are brought about due to the change of the stator resistance, mainly Stator current and flux distortion is very serious; the second is low torque ripple, thus limiting the speed range.
With the continuous development of modern science and technology, direct torque control technology will make breakthroughs and has broad application prospects. At present, the technology has been successfully applied to electric locomotive traction high-power AC drive.