Frequency converter control method
There are various control methods for frequency converters, each of which has its own characteristics and applicable scenarios.
1. Classification by feedback mechanism
● Open-loop control - refers to the inverter only controlling the output frequency of the motor, but not feedback controlling the motor speed.
● Closed-loop control - refers to the inverter performing feedback control on the output frequency and speed of the motor at the same time, and realizing precise control of the motor by monitoring and adjusting the motor speed.
2. Classification by advanced control methods
● Vector control (vector control) - is an advanced closed-loop control method that can accurately control the speed, torque and position of the motor to achieve high-performance control of the motor.
● Direct torque control (DTC) - Direct torque control uses the concept of space vector coordinates to analyze the mathematical model of the AC motor in the stator coordinate system and directly control the magnetic flux and torque of the motor.
3. Classification by traditional control methods
● V/f control - the control of the ratio of voltage to frequency is proposed to obtain the ideal torque-speed characteristics.
● Slip frequency control - a control method that directly controls torque. On the basis of V/f control, it adjusts the output frequency of the inverter according to the power supply frequency corresponding to the actual speed of the asynchronous motor and the desired torque.
4. According to other classification methods
● Classification by main circuit working filter method - voltage type inverter and current type inverter.
● Classification by switching method - PAM control inverter, PWM control inverter and high carrier frequency PWM control inverter.
● Classification by use - general inverter, high-performance special inverter, high-frequency inverter, single-phase inverter and three-phase inverter, etc.
5. Intelligent control methods
With the development of technology, intelligent control methods are gradually applied to frequency converters, such as neural network control and fuzzy control.
