Basic Principles of Inverter Control of Servo AC Motors
2.1 Working Principle of the Inverter
An inverter is a power electronic device that converts DC power into AC power, mainly composed of switching devices (such as IGBT, MOSFET, etc.), control circuits, and filter circuits. By controlling the on-off states of the switching devices, the inverter can output AC power with different frequencies and voltages, thereby controlling the servo AC motor.
2.2 Working Principle of the Servo AC Motor
A servo AC motor is a closed-loop control system that uses feedback devices such as encoders or decoders to monitor the motor's position and speed information in real-time and compares it with given commands to form closed-loop control. The inverter outputs voltage and frequency commands based on the control algorithm to drive the servo AC motor to rotate and adjusts the output voltage and frequency through the feedback device to ensure the motor operates accurately according to the given commands.
3. Control Strategies for Inverter Control of Servo AC Motors
3.1 Voltage-to-Frequency Ratio (V/F) Control
Voltage-to-Frequency Ratio (V/F) control is a simple control strategy that maintains a constant ratio between the output voltage and frequency to control the motor's speed. This control method is suitable for applications with little load variation and low dynamic performance requirements. However, V/F control may not yield ideal results in situations with significant load variations or high-precision control requirements.
3.2 Vector Control
Vector control is a high-precision control strategy that decouples the motor's current vector and voltage vector to achieve independent control of the motor's torque and speed. Vector control decomposes the stator current of the motor into two components: excitation current and torque current, which are controlled separately, thereby improving the motor's dynamic response speed and steady-state accuracy.
3.3 Direct Torque Control (DTC)
Direct Torque Control (DTC) is a control strategy based on direct torque feedback from the motor. By monitoring the motor's torque and flux information in real-time, DTC adjusts the inverter's output voltage and frequency to achieve rapid torque control of the motor. DTC offers fast response speeds and high control accuracy, making it suitable for applications requiring rapid torque response.
4. Key Techniques for Inverter Control of Servo AC Motors
4.1 Rational Selection of Inverter Types
Based on the rated power, rated voltage, and rated current of the servo AC motor, select the appropriate type and specification of the inverter. Ensure that the inverter has sufficient output power and current capacity to meet the motor's operational requirements.
4.2 Optimization of Control Algorithm Parameters
Optimize the parameter settings in the control algorithm, such as proportional gain, integral gain, and derivative gain, according to the actual application scenario and load characteristics. Adjusting these parameters can improve the system's dynamic response performance and steady-state accuracy.
4.3 Enhanced Thermal Management
The inverter generates heat during operation, and poor heat dissipation can lead to overheating protection or even damage to the inverter. Therefore, enhance the inverter's thermal management by adding heatsinks, using fans, or employing liquid cooling methods for heat dissipation.
4.4 Real-Time Monitoring and Fault Diagnosis
Monitor the inverter's output voltage, current, and temperature parameters in real-time to detect and address potential fault hazards promptly. Additionally, establish a comprehensive fault diagnosis mechanism to quickly locate and resolve faults when the inverter malfunctions.
