A direct torque control system

 The characteristics of the direct torque control is to control the stator flux linkage, is directly under the stator static coordinate system, with space vector concept, by detecting the stator voltage, current, direct calculation under the stator coordinate and control the flux linkage and torque of the motor, torque, high dynamic performance. It does not require the ac motor into equivalent dc motor, and thus eliminate the vector transformation of many complex calculations, it does not need to imitate the ac motor capacitor dc motor control, and thus do not need for decoupling and simplify the mathematical model of ac motor, and just care about the size of the electromagnetic torque and so on in addition to the stator resistance of all control motor parameters change good robustness, the stator flux observer is introduced by magnetic chain model can easily, and conveniently estimate the synchronous speed information, at the same time is also very easy to get torque model, flux model and torque model would constitute the complete motor model, and thus can easily achieve speed spare parts sensorless control, if again set the speed regulator in the system, can be further high-performance dynamic torque control. 

To be sure, the direct torque control inverter with different switching device, control method is also different. Depenbrock initially proposed directly from the control theory, mainly in the high voltage, high power and low switching frequency inverters are widely used in the control. Current control method is applied to general inverter is a kind of improvement, suitable for high switching frequency inverters. ABB company first launched in 1995 ACS600 series general inverter direct torque control system, the dynamic torque response speed has reached < 2 ms, when the belt speed sensor PG 0.001% rate of static accuracy of soil, in the case of without speed sensor PG even affected by the change of the input voltage or load mutation, also can be plus or minus 0.1% of the speed control accuracy. Other companies also is trying to target with direct torque control, such as Fuji company FRENIC5000VG7S series high performance electricalmotor1.blogspot.com speed sensorless vector control of general frequency converter, with direct torque control method and difference, but it also has to do the speed control accuracy + / - 0.005%, 100 hz and 800 hz current response speed response and torque control accuracy + / - 3% (PG). Other companies such as Japan's mitsubishi, Hitachi, the latest series of products such as Finland VASON speed sensorless control of similar design, performance have further improved.