Description
According to the three-phase power supply of the inverter, it can be divided into square wave control
and sine wave control. The square wave control strategy is simple, and the control process is direct
and effective. It adopts a six-step commutation strategy. The CPU modulates the PWM to drive the
power switch tube to generate a three-phase power supply that can run the motor. The control strategy
of sine wave is relatively complex, but the control effect is much better.
In sine wave control, there are two main control strategies.
One is direct torque control DTC Baidu Encyclopedia. The method is to calculate the estimated values
of motor flux and torque based on the measured motor voltage and current. After controlling the torque,
the motor speed can also be controlled. Direct torque control is a patent of the European ABB company. .
The second is, space vector control FOC Baidu Encyclopedia. Its essence is to equate an AC motor to a DC
motor, and independently control the speed and magnetic field components. By controlling the rotor flux linkage,
and then decomposing the stator current, the two components of torque and magnetic field are obtained. After
coordinate transformation, the normal motor is realized. handover or decoupling control.
During sine wave control, there are many derived more sophisticated control strategies, such as feedforward
control, maximum torque control, field weakening control, etc.
In the process of controlling the motor, there are multiple feedback control loops. When controlling the output
of the motor, there is a current loop; on this basis, there is a control loop that controls the speed; when a servo
motor is used, there is a position loop control.
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