Research On IPMSM Sensorless Control Strategy

Fans&pumps consume a huge amount of energy for their extensive application. By adopting variable frequency speed control technique, system efficiency could be significantly enhanced. However, due to the inherent limitation of the physical structure of traditional induction motors, problems like low power factor and high power loss in the rotors still stand in the way of further improvement of the fan&pump systems. In comparison, Permanent Magnet Synchronous Motors (PMSM) with compact structure serve as a feasible substitute by providing a better power density and a broader frequency band without sacrificing the system efficiency. In PMSM systems, position sensors are required to acquire position signals continuously. However, due to the high cost of the position sensors, which are also vulnerable to ambient environment, PMSM systems are not popularly acknowledged in vast application. Therefore, research in sensorless control method has a major impact on improving PMSM systems. Comparing with the common surface-mounted PMSM (SPMSM), special rotor structure of interior PMSM (IPMSM) results in a more complicated mathematic model. Although there have been many effective algorithms for rotor positioning for SPMSM, these well developed algorithms cannot be simply used in the same matter for IPMSM rotor position detection.In this dissertation, different position detection algorithms are compared based on the literature. Considering the specific electrical characteristics of the system, algorithm based on flux observation is chosen as the research topic. Furthermore, mathematic model of the IPMSM system is derived. In the section of control system design, vector control theory is introduced. In the design of control system, PMSM vector control principle and features are introduced. The PMSM current loop control model using voltage source inverter power and PI controller parameter tuning method based on the oscillation index method are analyzed in detail. PI control relationship between proportional system integration time constant of the motor parameters is derived; the same approach to derive the expression of the speed loop PI controller parameters is applied, the design of the PI controller parameters is given. Futher, a simulation model is created, the vector control simulations are used to verify the design and method of vector control parameters superiority. Chapter4gives a complete investigation of the IPMSM rotor position detection algorithm used in this paper. From the motor model of synchronous rotating frame, common rotor flux calculation method for both IPMSM and SPMSM is derived, the same expression can be used for the two different structures of the motor, and a new error compensation method is put forward for the characteristics of the non-ideal integrator, which theoretically eliminates the rotor observation error caused by the non-ideal integrator. Base on the rotation movement equations, a three-stage startup method is designed to accelerate the IPMSM rotor from standstill to a certain speed at which the rotor position can be observed. Sensorless field vector control simulation model is built for a fan system driven by IPMSM, the validity of the simulation results demonstrate the startup and rotor position detection algorithm. Finally, the overall structure of hardware and software systems are introduced. Experiments have been carried out to test the performance of the sensorless algorithm. The results further validate the effectiveness of the algorithm.