永磁式同步馬達之無電流感測器控制

Abstract

本論文針對永磁式同步馬達發展一簡單且具有寬廣操作範圍特性的無電流感測器控制。根據一般小型電動機的雙時階特性，應用奇點干擾法來發展控制器，可使得控制器在毋須知道馬達電流狀態的情形下，仍可達到所要求的速度位置伺服控制。此種控制不同於傳統全狀態回饋的雙迴路控制設計。在正常操作下，論文中所建議的控制器雖然無電流回饋，但為求提高能源使用效率，仍可間接控制馬達電流狀態達到最小銅損的設計要求。再者，當電壓飽和（過調變）發生時，所建議的控制器將自動轉變為具有弱激磁控制特性的控制器，故馬達的操作範圍不因電壓飽和的發生而提前受限。在此性能下，馬達控制的操作範圍得以擴展。此外，更進一步的分析發現，那自動生成的弱激磁電流會隨負載自行調整，使之恆處於最小銅損狀況中。此最小銅損下之弱激磁控制特性，與現有文獻中最大扭力或定功率輸出的弱激磁設計完全不同。另一方面，對於控制設計所必須面對的穩定性問題，在本論文中亦對所建議控制的穩定性有完整的分析探討。電腦模擬與實驗結果驗證了此控制器即使在電壓發生飽和的情形下仍可達到有效的速度位置控制。另外，由於控制器已將電流雜訊完全隔絕於外，實驗結果證明此控制具有高精度的定位控制性能。

This thesis presents a novel means of designing a simple and effective velocity and position controller for permanent magnet synchronous motors (PMSM). In contrast to the conventional two-loop control methods with full-state feedback, the proposed controller does not need current information of the motor for feedback purposes. The proposed current-sensorless controller is developed from a singular perturbation analysis of the PMSM model by taking advantage of the two-time-scale property of small electrical machines. However, under normal operation the steady-state d-axis current can still be controlled to zero to reduce copper loss. In addition, implementing a simple overmodulation strategy allows the controller to automatically generate a flux-weakening control to expand the range of operating speed when voltage saturation occurs. In addition to not depending on system parameters used by the controller, the automatically generated flux-weakening current is also optimal in the sense of minimum copper loss that differs from the maximum output torque design or the constant power design of the general flux-weakening control methods. Complete stability analyses for the current-sensorless control are also presented herein. Simulation and experimental results show that the controller can achieve an effective speed and position control with near-minimum copper loss, even when voltage saturation occurs. In addition, the performance of this current-sensorless controller is compared with that of a full-state feedback controller in experiment. Clearly, the proposed current-sensorless controller can achieve zero positioning error within the resolution of an optical encoder. However, the same result is less easy to achieve using a full-state feedback controller due to the noise effect on the current measurements.