Second Harmonic Seamless Splicing Technique Based on Maximum Active-Voltage Vector for Online MTPA Tracking Control of SynRM

Maximum-torque-per-ampere (MTPA) control strategy is widely employed to achieve the optimal efficiency control of synchronous reluctance machines (SynRMs). However, the control efficiency of the conventional method that the optimal current distribution angle is directly calculated based on the knowledge of the machine parameters is seriously affected by the highly nonlinear and time-varying characteristics of SynRMs. Therefore, in order to effectively resolve this problem, a novel MTPA control scheme based on the second harmonic splicing technique is proposed in this article. Differing from the conventional method, the proposed solution utilizes the transient response current slopes of fundamental maximum active-voltage vector to splice a specific second harmonic signal that contains the optimal current distribution angle. After selecting two available and different splicing coefficients in each sector to guarantee the continuity of the spliced second harmonic signal, the optimal current distribution angle can be obtained accurately without any machine parameters through a simple signal demodulation, which significantly enhances the robustness to machine parameter variations. Furthermore, the influence of rotor position acquisition errors caused by the position sensor's limited accuracy and installation misalignment is analyzed in detail. Finally, the experimental results demonstrate the effectiveness and feasibility of the proposed MTPA control scheme.