Deadbeat predictive current control for permanent magnet synchronous motor

• Main Author: Song, Chen
• Other Authors: Christopher H. T. Lee
• Format: Thesis-Master by Coursework
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Electrical and electronic engineering::Power electronics
• Online Access: https://hdl.handle.net/10356/152566
• Institution: Nanyang Technological University

Permanent magnet synchronous motors (PMSMs) are widely used in industry in view of their high power density and efficiency, small weight and size, high torque to inertia ratio, among other attributes. A PMSM servo system is composed of three loops: current loop, speed loop and position loop. The transient response performance of the current loop, especially the response speed, is of great significance to the overall system’s speed control quality. Nevertheless, the traditional proportional-integral (PI) regulator is limited in terms of the current tracking speed, which needs to be improved. This thesis first elaborates on the principle of field-oriented control (FOC), presenting a classical method of PI controller design in terms of both current loop and speed loop with a detailed mathematical analysis based on block diagram. Then, the original deadbeat predictive current control (DPCC) algorithm is proposed to improve the current tracking speed. As shown, the stability of the system is degraded by the motor’s parameter mismatch, particularly the stator inductance error. The transform is applied to help obtain the current loop’s pulse transfer function. The algorithm’s stability condition, which states that the system is stable as long as the nominal stator inductance is smaller than twice the actual stator inductance, is derived by analyzing pole position in domain. Moreover, to enhance the original algorithm’s robustness, a modified robust DPCC algorithm that introduces two weight coefficients into the voltage equation is proposed, which proves to broaden the stability range effectively by adjusting coefficient value. In summary, the proposed original DPCC algorithm outperforms the conventional PI control algorithm in terms of quadrature current’s transient response speed. In turn, the modified robust DPCC algorithm reduces the original algorithm’s sensitivity to stator inductance parameter mismatch, successfully boosting the algorithm’s robustness. The proposed approaches are all well supported by simulation and experimental results. Keywords: Permanent magnet synchronous motor (PMSM), parameter mismatch, deadbeat predictive current control (DPCC), field-oriented control (FOC), robust control.