Research On Sensorless Control Technology Of The Permanent Magnet Synchronous Motor

As it has many advantages including small size, light weight, high power density, high power factor, high efficiency, high torque/inertia ratio, high reliability, easy maintenance and so on, permanent magnet synchronous motor (PMSM) is widely used nowadays. However, position sensor installed in the traditional PMSM brings installation difficulties, application environment limited and other issues. Thus sensorless control technology comes into being, and promotes wider application of PMSM, having very important significance. This thesis is derived from the application of PMSM in fan and water pump systems, as in the current society fan and pump motors are widely used in various fields of national life, and adopting sensorless PMSM has high efficiency, high performance, low cost, high reliability and other advantages.This thesis firstly studies a lot of the domestic and foreign literatures about PMSM sensorless control technology, summarizes the research significance, research status and research methods of the PMSM sensorless control technology, and selects the variable-structure control system with sliding mode, which is of strong robustness and good stability, as research core of the sensorless vector control technology in this thesis. Through coordinate transformation, the mathematical model of the PMSM is established in the dqO coordinate system, and the issues need to pay attention to research and solve are determined in the PMSM vector control system that use id=0 control. Among the issues, to the content of the SVPWM in the vector control, emphatically analyses and demonstrates a simplified T1、T2 algorithm based on judging the sign of three phase voltage values in the case of adopting the improved Clark inverse transformation. The algorithm can determine the sector which the voltage locates according to the sign of three phase voltage values under the improved Clark inverse transformation, and give the direct proportion relationship between the functioning time T1、T2 of the two basic voltages adjacent to the sector which the voltage vector locates and certain two phase voltage values at the moment.Next, the thesis focuses on the acquisition PMSM rotor position with sensorless control technology. On one hand, researches the variable-structure control system with sliding mode at the PMSM intermediate speed and high speed operating stage. Establishing the sliding mode observer according to the PMSM mathematical model in the two-phase stationary coordinate system, defining the error of the estimated current and actual current as the switching plane, adopting saturation function that can inhibit jitter as the control function, using the first-order low-pass filter for filtering the control function to extract the estimated back electromotive force (EMF) signal, bringing the control function and the estimated back EMF signal together to feed back to the sliding mode observer, constitute the complete PMSM variable-structure control system with sliding mode. Then, based on the sliding mode control theory, the existence, accessibility,stability conditions of the established PMSM variable structure control system with sliding mode is demonstrated and given. After that, the estimated back EMF signal is filtered secondly to obtain the final back EMF signal, which is used to solve the rotor position angle, and the rotor position angle compensation method based on the filter with constant delay angle is researched. The speed estimation method is studied afterwards. On the other hand, researches the open-loop starting algorithm at the PMSM zero speed and low speed operating stage. At the zero speed stage,the rotor is forced to rotate and stop at the axis of A phase windings through the rotor pre positioning method. At the low speed stage, the PMSM starting with constant acceleration through the current closed-loop starting method. Then, the method between the open-loop starting and closed-loop operation is researched.Then, a PMSM sensorless controller is developed. For the hardware part of the controller, the main circuit, the dsPIC DSC minimum system, driver circuit, detection circuit, fault protection circuit, serial communication circuit and power supply system are researched and designed. For the software design, from the perspective of the top-level design and real-time requirement, the software is divided into the design of main program and A/D interrupt program. The A/D interrupt program contains the whole control algorithm. Then the program design of the variable-structure control system with sliding mode is focused on, and research is done for the discrete realization of the first-order low-pass filter with constant delay angle and the specific solution of the rotor angular velocity in the software. Finally, lots of experiments are done to improve the controller and to verify the developed sensorless controller can drive the PMSM running smoothly and reliably, proving the practicability of the PMSM sensorless technology based on variable-structure control system with sliding mode this thesis researched.