Abstract: This paper introduces the limitations of general-purpose frequency converters, analyzes the control strategies of high-performance general-purpose frequency converters, describes the application and development of vector control and direct torque control, and discusses the prospects of sensorless control. Keywords: General-purpose frequency converter; Vector control; Direct torque control 1 Limitations of General-Purpose Frequency Converters When using general-purpose frequency converters to power asynchronous motors, stepless smooth speed regulation can be achieved, and starting and stopping are very convenient. However, there is a steady-state error during speed regulation, the accuracy is not high, the speed regulation range is no more than 1:10, and it cannot provide the high dynamic performance of DC speed regulation systems. 2 Control Strategies of High-Performance General-Purpose Frequency Converters To achieve high dynamic performance, it is necessary to fully study the physical model and dynamic mathematical model of the motor. Currently, the commonly used high-performance control strategies are vector control and direct torque control. The characteristics of a vector control system are: it employs a dq synchronous rotating coordinate system whose d-axis direction is determined by the rotor flux linkage; it decomposes the stator current of the asynchronous motor into its excitation and torque components, obtaining a torque model similar to a DC motor; and then takes measures to transform the nonlinear system into two independent subsystems of speed and rotor flux linkage, thereby mimicking the control of a DC motor using PI regulators. When using a high-precision photoelectric encoder speed sensor, the speed regulation range of the vector control system can reach 1:1000, and the dynamic performance is also very good. However, the rotor flux linkage orientation is affected by changes in motor parameters, resulting in distortion and reducing the speed regulation performance of the system. Using an intelligent regulator can overcome this shortcoming and improve the robustness of the system. [b][align=center]For more details, please click: Ways to Improve the Performance of General-Purpose Frequency Converters[/align][/b]