A Study On PMSM Sensorless Vector Control Technology

Permanent magnet synchronous motors (PMSM) are widely used in lots of fields such as aerospace, CNC machining, robotics with its advantages of small size, high efficiency, energy saving etc. In PMSM vector control system, speed and position feedback is critical. Traditional mechanical sensors cost high price, difficult to fix and has poor environmental adaptability. Therefore, sensorless technology has become a hot topic.On the basis of studying PMSM mathematical model and space vector pulse width modulation (SVPWM) technology, a id = 0 rotor flux oriented vector control strategy is adapted and the physical simulation model is established using Saber Designer software.For PMSM vector control system with a sensor, the digital PI regulator of current loop and speed loop are designed. To optimize the dynamic performance, negative speed differential feedback is adapted to suppress overshoot, and a load torque compensation method is adapted to enhance the system robustness. Simulation results show that the control system with a sensor has high precision, small overshoot, and good robustness.Then PMSM sensorless vector control system based on model reference adaptive algorithm (MRAS) is studied to estimates the rotor speed, with PMSM itself as a reference model, and the current model with a state feedback matrix as an adjustable model. To obtain the adaptive law of the estimated speed, hyperstability theory is used to solve the Popov inequality. Simulation results show that the MRAS based sensorless speed estimation system has good dynamic and static performance.Given the importance of initial rotor position in the field orientation of PMSM vector control system with or without a sensor, two different methods of locating the initial rotor position are introduced accordingly.