Design of Three-phase AC-DC-AC Frequency Converter Construction of Experimental Cases Based on PI Control

Due to excellent speed regulation function, efficient starting and braking efficiency and sound energy saving effect, the frequency converter has been widely applied in industrial production, scientific research and experimental teaching. However, due to its high integration, complicated internal structure, high cost and small quantity, it can only be used to assist students to do basic operations in the laboratory such as motor speed adjustment, and it is difficult to teach the theories of rectification, filtering, inverter, proportional-integral (PI) control, and sinusoidal pulse width modulation (SPWM) wave to students. This paper has designed a AC-DC-AC variable frequency speed control system using Simulink, and converted fundamental frequency power supply to frequency-varying alternating voltage, and achieved three-phase asynchronous motor speed control by combining with PI control and control techniques of modulated wave. Based on this teaching simulation model, students can perform simulation analysis on different PI, filtering and modulation wave control parameters, namely, allowing students to verify the important theoretical knowledge related to the frequency converter through simulation analysis. This helps further deepen the students’ understanding of the control theory, lay a good foundation for the experimental teaching of motor control, and improve the students’ ability to design circuits, simulate analysis and solve problems.