Search

This article proposes a maximum efficiency per torque (MEPT) control strategy for interior permanent magnet synchronous motor (IPMSM) based on the acquisition of loss criteria. First, the characteristics and practical occasions of four different efficiency optimization strategies are theoretically analyzed. Based on the mathematical model of IPMSM considering iron loss, the extremum equation satisfying torque control accuracy and loss minimization is established. Meanwhile, a criterion F, which can reflect IPMSM loss is proposed. Criterion F is characterized by crossing the point of zero, which corresponds to the minimization point of loss. Then, the current reference setting method for the MEPT control is designed based on criterion F. In addition, the impact of voltage errors and parameter variations on the accuracy of the current reference setting is evaluated. The proposed method avoids the complex solution process of high-order nonlinear equation in efficiency optimization, thereby simplifying the implementation of the current reference setting. Furthermore, it also avoids the approximate simplification of the current reference solving process, which enhances the precision of the current reference. Finally, the effectiveness and superiority of the proposed method are verified by experiment.

Considering the large number of switching devices and complex input/output coupling in multiphase indirect matrix converter (IMC) drive, it is difficult to establish the periodic pulsewidth modulation (PWM) strategy according to the current ripple index. To solve this problem, this article proposes a dynamic periodic PWM (DP-PWM) strategy with flux ripple locus for 3×6 IMC drives. First, we analyze the limitations of classic periodic PWM on the 3×6 IMC drive. Second, the flux ripple locus is established from the voltage errors. And, the mapping relationship between flux fluctuations and input/output variables is constructed. At last, the conventional current ripple index is replaced with the flux ripple locus, then a novel frequency density function employed in DP-PWM, which has the same distribution as the flux fluctuations is designed. Theoretical and experimental results show that the flux ripple locus can accurately reflect the coupling relationship between the grid- and output-side of 3×6 IMC drives, as well as the losses of motor system. This ensures that DP-PWM has uniform harmonic distribution while optimizing system operating efficiency and quality.

Two practical methods for fast optimizing the position of the high-speed permanent magnet synchronous motor (HSPMSM) are proposed in this article, utilizing the prediction methodology. They directly use the characteristics of the predicted stator current to demodulate the estimated position, without obtaining the back electromotive force first and second judgment. Both can simplify the sensorless control algorithm while ensuring precise position estimation, which are more conducive to the digital realization of HSPMSM sensorless control. The performances of the proposed methods are verified on a 1.1 kW, 30 000 r/min HSPMSM experimental platform, and compared with the traditional finite position set-phase locked loop and the common adaptive sliding mode observer. The experimental results prove the validity of the proposed methods for HSPMSM sensorless control.

Dual-stator permanent magnet motors (DSPMMs) have the advantages of fault-tolerant capability and high control flexibility due to the presence of both outer and inner stators. The DSPMM is studied in this article, whose operation performance with different stator winding connection modes is analyzed. First, a hybrid subdomain model that takes into account the influence of stator core saturation is proposed by combining the subdomain method and magnetic circuit method. The key to the model lies in using the equivalent surface current to represent the nonlinear effects of the outer and inner stator cores, which is adopted by the boundary conditions for the hybrid subdomain model. The equivalent surface current is obtained by the magnetic circuit based on the structure of stator cores. The principle and derivation process of hybrid subdomain model for DSPMM is provided in detail. The accuracy and rapidity of the proposed model are verified by comparing with the finite-element analysis (FEA) and experiment. In addition, based on the proposed hybrid subdomain model of DSPMM, the output torque, efficiency, and fault-tolerant ability with four winding connection modes are analyzed when the outer and inner stators are controlled independently or in series. The analysis results provide a reference for applying different winding structures of DSPMM to adapt different application scenarios and operation conditions.

This article proposes a solution to the challenge of achieving a reliable restart in sensorless permanent magnet synchronous motors transitioning from a three-phase six-switch inverter to a three-phase four-switch (TPFS) inverter due to faults. The proposed rotating restart method employs the injection of dual effective voltage vectors to synthesize the equivalent zero-voltage vector, under unbalanced capacitor voltage conditions in the TPFS inverter. This synthesis is achieved by incorporating the capacitor voltage offset into the duration calculation of the dual effective voltage vectors. Once the main power supply is restored, the dual effective voltage vectors are injected into the motor windings through the TPFS inverter, producing the short-circuit current influenced by the back electromotive force. The method utilizes the accumulated short-circuit current values to estimate the initial rotor position and speed, enabling a smooth and efficient rotating restart. This innovative method enhances the accuracy of rotor position and speed detection, reduces impulse current, and ensures the fault-tolerant operation of the system. The theoretical analysis is validated through experimental results, demonstrating the effectiveness and reliability of the proposed method.

Aiming at asymmetrical winding (ASW) layouts design for fractional-slot permanent magnet synchronous machine (PMSM), this article improves the conventional star-of-slot theory and proposes an effective design method of fractional-slot ASW layouts for various slot-pole combinations. In the design process, the proposed method considers the characteristic components of air-gap field time–space harmonics and the harmonic characteristic of unbalanced magnetic force (UMF). It can be used to investigate the design principles of ASW layout with a lower UMF through extracting and analyzing force vectors produced by air-gap field time–space harmonics that mainly contribute to UMF. Finally, two 39-slot and 12-pole surface-mounted PMSMs with different winding layouts are manufactured and tested. Both finite-element analysis and experimental results confirm the effectiveness of the proposed design method for double-layer ASW structures.

In this article, a variable structure sliding mode observer (VS-SMO) for load torque observation is designed by adding a decoupling term to the structure of the traditional sliding mode observer. The VS-SMO can remove the coupling relationship between the parameter to be estimated and the derivative of the estimated speed error, as well as the chattering signal in the estimated load torque. Then, a variable structure extended sliding mode observer (VS-ESMO) is designed on this basis, with the moment of inertia used as an extension, to achieve simultaneous identification of the load torque and the moment of inertia. This article analyzes the estimation errors and the impact of measurement noise on estimation errors. The stability of the VS-ESMO is proved by backstepping control theory. An experiment is carried out on a 3.1 kW surface-mounted permanent magnet synchronous motor to validate the identification performance. The experimental results demonstrate that the VS-ESMO has a high estimation accuracy and fast convergence speed, and the identification value does not contain a chattering signal. Using the inertia and load torque identified by VS-ESMO for parameter tuning and compensation can improve system dynamic performance and anti-interference performance to the load.

The utilization of the explicit model predictive (EMP) control method for direct speed control (DSC) of permanent magnet synchronous motors (PMSMs) achieves high-bandwidth speed control and excellent dynamic performance. However, the commonly used regular hexagonal current and voltage constraints restrict the motor's operational region, resulting in a narrow speed range and low load capacity. In addition, the conventional formula-based field-weakening method leads to undesirable allocation of $d$- and $q$-axis currents, reducing the degree of freedom in adjusting the motor's operating point. These drawbacks restrict the EMP-DSC method's application in the motor's extreme operation. Therefore, this article proposes an expanded limit boundary EMP-DSC method to realize cascade-free speed control with a wider speed range and higher load capacity. First, the proposed method constructs irregular hexagonal constraints, expanding the limit boundary of the motor's operational region in the $i_{\mathrm{d}}$–$i_{\mathrm{q}}$ plane to broaden the speed and load ranges simultaneously. Then, based on these new constraints, an easily implementable optimal-trajectory field-weakening method is skillfully designed to optimize the current distribution, maintain the operating point near the optimal position, and improve field weakening performance. The proposed method enhances the competitiveness of EMP control in motor servo drive fields, and its feasibility is verified by experiments.