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This paper presents an online maximum torque per ampere (MTPA) control that considers both magnetic saturation and cross-magnetization effects of interior permanent-magnet synchronous machines (IPMSMs). For IPMSM drives, especially in torque-controlled applications, torque accuracy and high-efficiency operations are important issues. They can be dealt as a constrained optimization problem to satisfy both torque reference tracking and loss-minimizing operation. In this paper, nonlinear simultaneous equations are derived from Lagrange multiplier method, which could be solved by numerical algorithms. Among them, Levenberg–Marquardt algorithm (LMA) is employed to guarantee a robust calculation of optimal current references. It is optimized to alleviate calculation burden while maintaining the stability of the proposed algorithm. In addition, a torque reference limiter is implemented to satisfy a current limit in real time. The feasibility of the proposed method is verified under various operating conditions by simulation and experimental results. Through the proposed algorithms, accurate MTPA control is achieved under not only unsaturated but also highly saturated operating conditions. [ABSTRACT FROM AUTHOR]

In this paper, the theoretical analysis of the position estimation error in position-sensorless operation using pulsating square wave signal injection is presented. The purpose of this paper is to analyze the phenomenon that the position estimation performance varies depending on the injection frequency. Mathematical derivation supported by simulation and experimental results shows that, in no-load condition, the voltage distortion induces position estimation error with 3rd-order harmonics if the frequency of the injected square wave is the same to the switching frequency. While, if the frequency is a half of the switching frequency or heavier load condition in either injection frequency, the effect of nonideal characteristics of inverter disappears and there is no 3rd harmonics in the position estimation error. Therefore, only the effect of cross-coupling inductance is reflected in the estimation error. As the result, the position estimation error appears in the form of 6th-order harmonics due to the spatial harmonics of inductances, and the error is relatively small compared with the switching frequency injection case. The theoretical analysis was verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]

In this paper, new model-based sensorless control methods are proposed that include independent estimations of position and speed errors, and compatible position and speed estimators. Using the proposed position estimator, a unity transfer function can be achieved from the actual position to the estimated position, eliminating the effects of load disturbances. This implies that the position error would ideally be zero, even in a transient state. In addition, the effects of parameter and voltage synthesis errors on the steady-state position error are analyzed. Experimental results verify both the analysis and the effectiveness of the proposed methods under severe load disturbances such as speed transient (20 000 r/min/s) and load torque transient (10 p.u./s). With the proposed methods, position estimation errors are significantly reduced by more than 50% during speed and load torque transients at identical dominant-pole placements, verifying the enhanced tracking capability and robustness of the proposed methods against external load disturbances. [ABSTRACT FROM AUTHOR]