The use of this kind of equipment, from a technical point of view, the control mode of the low-voltage inverter also indicates its technical genre to some extent. Therefore, the control of its low-voltage inverter is different:
The first type, the direct torque control (DTC) method, largely solves the above-mentioned shortcomings of vector control, and has been rapidly developed with novel control ideas, simple and clear system structure, and excellent dynamic and static performance.
The second, vector control frequency control, its essence is equivalent to the AC motor is equivalent to a DC motor, respectively, the speed and magnetic components are independently controlled. By controlling the rotor flux linkage and then decomposing the stator current, two components of torque and magnetic field are obtained, and coordinate transformation is performed to realize orthogonal or decoupling control.
Third, sinusoidal pulse width modulation (SPWM) is characterized by simple control structure, low cost, good mechanical properties and hardness, which can meet the requirements of smooth speed regulation of general transmissions, and has been widely used in various fields of the industry. However, in the low frequency mode, the torque is affected by the voltage drop of the stator resistance at a low frequency, so that the maximum torque of the output is reduced. In addition, its mechanical characteristics do not have DC motor hard, dynamic torque capability and static speed regulation performance are not satisfactory, and the system performance is not high, the control curve will change with the load change, the torque response is slow, the motor turns The moment utilization rate is not high, and the performance is degraded due to the existence of the stator resistance and the dead zone effect of the inverter at a low speed, and the stability is deteriorated.
The fourth type, voltage space vector (SVPWM) is based on the premise of the three-phase waveform overall generation effect, aiming at the ideal circular rotating magnetic field trajectory close to the motor air gap, generating a three-phase modulation waveform at a time, and approximating the circle with the inscribed polygon Way to control.
The embodiment of the control system is just like this. In different industries, its control response capability is different. In different mechanical systems, the control methods are different, and they are different. Embody and contribute. Therefore, the user should have an in-depth understanding of the way the device should be controlled.
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