Program for Closed-Loop Controlled Three-Phase Asynchronous Motor

Analysis of SPWM Closed-Loop Control Program for Three-Phase Asynchronous Motors

In the field of industrial drives, closed-loop control using Sinusoidal Pulse Width Modulation (SPWM) is a classic solution for achieving precise speed regulation of three-phase asynchronous motors. When implementing this program in MATLAB, it typically includes the following core modules:

SPWM Generation Module: Generates drive signals by comparing carrier waves with sinusoidal reference waves, with key parameters being modulation ratio and carrier frequency adjustment. In MATLAB, this can be implemented using comparator blocks or by writing S-functions for dynamic modulation control.

Vector Control Strategy: Utilizes FOC (Field Oriented Control) to decouple three-phase currents into torque and excitation components, controlled separately through PI regulators. Accurate implementation of Clarke/Park transformations and rotor flux observer design are critical considerations.

Closed-Loop Feedback System: Typically features a dual-loop structure comprising speed and current loops. The speed loop calculates speed error using encoder feedback, while the current loop samples phase currents for hysteresis control or predictive control implementations.

Protection Mechanism Design: The program must integrate safety logic including overcurrent protection and DC bus voltage monitoring to prevent IGBT module damage under abnormal operating conditions.

Key implementation challenges include parameter tuning (such as PI controller gains) and optimal switching frequency selection. Using MATLAB/Simulink's real-time simulation capabilities, dynamic response characteristics under varying load conditions can be validated. This approach can be extended to other AC motor control applications, such as permanent magnet synchronous motor drive systems.