Search

Interior permanent magnet synchronous machines (IPMSMs) are extensively used in electric drives due to their high-power density and wide-speed operation capability. In order to improve the performance of the drive application, low torque ripple of the IPMSM is valuable and necessary. However, as far as the existing analytical models are concerned, it is difficult to establish a direct relationship between the structural parameters and the torque ripple law of IPMSMs due to the complexity of their flux circuits, and therefore, it is not easy to achieve a directional suppression of the torque ripple by means of design. With this in mind, this article establishes a general analytical model for electromagnetic torque and its ripples (including synchronous torque, reluctance torque, and cogging torque) based on the harmonic interaction effects. Thereby, a novel and simple design method to reduce torque ripple is proposed, and its principle is to change the rotor surface shape to artificially construct the specific number of reluctance harmonics. As a result, it is verified by finite element method and experiments that the proposed method can precisely eliminate the specific torque ripple and reduce the overall torque ripple.

Permanent magnet (PM) machines garner significant attention due to their high-power density and high efficiency. As research progresses, high-end motor applications are placing higher and more comprehensive performance demands on PM machines, driving the need for multifaceted and synergistic motor design optimization. In response to this demand, this article proposes a multi-objective optimization design process aimed at improving the overall electromagnetic performance of PM machines. The objectives include enhancing torque density, suppressing torque ripple, and reducing vibration and noise. The optimization process utilizes a meta-model fitted to the numerical model solved by the finite element method, leading to a substantial acceleration of the overall optimization process. Furthermore, an optimization approach is employed to optimize several key structural parameters of a double layer interior PM machine using an evolutionary algorithm. The resulting optimized motor is fabricated and tested, and both numerical simulations and experiments validate that the optimized motor exhibits enhanced torque, low torque ripple, and avoids resonance vibration noise near the rated speed. This comprehensive validation confirms the effectiveness of the structural design and the optimization process.

The first-order inertia of the armature winding of the brushless DC motor will cause current offset, which will reduce the electromagnetic torque. In the sensorless drive of brushless DC motors, correction of commutation point is an effective solution to improve motor performance. This paper analyzes the relationship between the electromagnetic torque and the compensation angle in the static coordinate system, and it is concluded that the internal power factor angle (IPFA) is equal before and after the commutation. The dc component of the IPFA is constructed as a feedback variable, a novel iterative sliding mode observer is designed to improve the compensation accuracy, and the adaptive output of the optimal angle is realized through the PI regulator. The scheme is simple to implement, and has higher accuracy, stronger adaptability and robustness. Simulation and experimental results verify the effectiveness and feasibility of the proposed correction strategy.

Torque is a significant parameter in the design and control of permanent magnet synchronous motor (PMSM). Torque measurement systems are usually expensive, which correspondingly require extra room and add weight. Alternatively, torque can be estimated by the product of the measured current and the estimated magnetic flux. In general, the conventional torque estimation method for PMSM is established based on ignoring core saturation. However, in special vehicles, due to the high power density and narrow installation space of the motors, the saturation degree of the core is high, and the nonlinear characteristic between torque and current is more prominent, which would bring significant errors to the conventional torque estimation method. In order to solve the aforementioned problem, this paper studies on the torque from the perspective of magnetomotive force (MMF). A saturation coefficient is proposed to modify the conventional torque model by considering the core reluctance. Then, a practical analytical expression of average torque and an improved torque estimation method are proposed. Compared with the conventional method, the proposed method significantly improves the accuracy of the estimation. At last, comprehensive simulation and experimental results based on a prototyped 300 kW interior PMSM have fully demonstrated that the proposed method can get accurate torque under different load conditions.

In the field of heavy-duty transportation of electric locomotives, the power of traction converters can reach MW, but the switching frequency needs to be kept at several hundred Hz. In addition, the converter needs to maintain a high transient response to load changes and keep grid-side harmonics at a low level, which is difficult to meet simultaneously. More critically, load disturbances often occur in electric locomotives during operation, which may lead to DC voltage pulsations and more serious overvoltage faults, which in turn lead to an increase in grid harmonics and a reduction in the stability of the traction system. To address the above challenges, this paper proposes a state observer-based power feedforward control method for high-power locomotives, which helps to improve the dynamic performance of the converter while minimizing harmonics to the grid, thus achieving more stable operation of the traction system. Finally, the feasibility and effectiveness of the proposed method are verified by simulations and multi-condition experiments on a 1.2MW electric traction platform.

Accurate modelling of motor magnetic fields facilitates all aspects of motor analysis, design, and optimization. Existing methods are difficult to balance the speed and accuracy of modeling, among which the widely popular finite element method is relatively time-consuming and the accuracy of magnetic circuit modeling is difficult to guarantee. In this regard, this paper presents a magnetic equivalent circuit model based on the multiple flux source network for interior permanent magnet (IPM) machines. The model considers the magnetic saturation effect through a non-linear iterative process. The accuracy improvement of the proposed model has been verified by comparison with the traditional single-flux-source model. Furthermore, the proposed model greatly saves the calculation time while bringing fairly good accuracy compared to the finite-element method, which is beneficial for the design optimization of the IPM machines.