Five-phase Surface-mounted Permanent Magnet Research Articles

Surrogate-Assisted Optimization of a Five-Phase SPM Machine With Quasi-Trapezoidal PMs

In this article, an improved surrogate-assisted design optimization method is proposed and applied to the torque performance optimization of a five-phase surface-mounted permanent magnet machine with quasi-trapezoidal permanent magnets. It integrates the Taguchi and surrogate-assisted methods; the training data for surrogate models are generated by the Taguchi method to reduce reliance on the finite-element analysis (FEA), in turn, the local optimum problem caused by the Taguchi method is tackled by the surrogate model. The generalization ability of surrogate models is enhanced by the parameter transfer technique. Using the fuzzy best-worst method, the decision process of multiple solutions is placed before optimization so that the multiobjective optimization can be transformed into a single objective to facilitate the search process for the optimal design. The optimization results are validated by the test results from a prototype. Compared with the FEA-based parametric scanning method, the optimization cycle is shortened by 94% and a globally optimal design can be obtained.

A Fault-Tolerant FOC Strategy for Five-Phase SPMSM With Minimum Torque Ripples in the Full Torque Operation Range Under Double-Phase Open-Circuit Fault

This article proposes a fault-tolerant field-oriented control strategy for five-phase surface-mounted permanent magnet synchronous machine with non-sinusoidal back electromotive force under double-phase open-circuit fault, where the failure phases are either adjacent or nonadjacent. Based on the decoupled mathematical model after failure, the optimum current references which satisfy the zero-torque-pulsation constraint at the synchronous frame are presented. However, the torque operation range is small. So a full-range minimum torque ripples post-fault strategy is proposed. This strategy extends the torque operation range by gradually relaxing the zero-torque-pulsation constraint. And it can minimize the torque ripples for each torque reference value in the whole torque operation range. The synchronous frame proportional integral resonant controllers and carrier-based pulsewidth modulation are employed to implement the proposed post-fault strategy. The experimental results are provided to verify that the proposed strategy can achieve wider torque operation range and smaller torque ripples compared with the conventional fault-tolerant strategies.

Fault‐tolerant FOC for five‐phase SPMSM with non‐sinusoidal back EMF

A fault-tolerant field-oriented control (FOC) is proposed for five-phase surface-mounted permanent magnet synchronous motor (SPMSM) with non-sinusoidal back electromotive force under single-phase open-circuit fault. On the basis of the concept of preserving the circular rotation of fundamental magnetic motive force and PM flux linkage, the decoupled model of five-phase SPMSM under single-phase open-circuit fault is derived. To suppress the torque ripples caused by third-harmonic content of PM flux linkage, the closed-form solution of current references with zero-torque pulsation in the synchronous coordinate is presented. Then, the presented solution is used for obtaining optimum current references to achieve minimum stator winding losses and maximum available torque while satisfying the zero-torque-pulsation constraint. The optimal current references generation method is simple and is suitable for real-time implementation. The experimental results confirm that the proposed method can effectively suppress the torque ripples and produce lower stator winding losses as well as wider-torque operation range compared with traditional fault-tolerant FOC method.

A Constant Switching Frequency Multiple-Vector-Based Model Predictive Current Control of Five-Phase PMSM With Nonsinusoidal Back EMF

Most of the existing finite-control-set model predictive current control (FCS-MPCC) schemes for multi-phase motor suffer from heavy computational burden, inevitable low-order harmonic currents, and variable switching frequencies. Some virtual voltage vector (V3)-based FCS-MPCC schemes can effectively suppress harmonic current by zeroing the harmonic subspace voltage on average during one sampling period. However, they fail when the motor has a nonsinusoidal back electromotive force. In order to solve the aforementioned issues, this paper proposes a constant switching frequency multiple-vector-based FCS-MPCC scheme. Unlike the traditional FCS-MPCC schemes, the proposed scheme selects optimal V3s and their duty ratios in two orthogonal subspaces. Thus, it can simultaneously track the references in both orthogonal subspaces. In this approach, the optimal V3s and their duty ratios are directly obtained from the principle of deadbeat current control without time-consuming enumeration-based state predictions and cost function calculations. In addition, the obtained optimal V3s and their duty ratios are adopted to rearrange the pulse sequence to obtain constant switching frequency and can be simply synthesized by carrier-based pulsewidth modulation. Furthermore, a discrete time disturbance observer is designed to improve the robustness of the proposed FCS-MPCC against parameter mismatch. Finally, comparative experiments with traditional MPCC schemes for five-phase surface-mounted permanent magnet synchronous machine are carried out to verify the effectiveness of the proposed scheme.

Design and Analysis of a Five-Phase SPM Machine Considering Third Harmonic Current Injection

This paper analytically derives the optimal third harmonic current to improve the output torque in five-phase surface-mounted permanent magnet (SPM) machines under the constraints of the same peak/rms value. The relationship between the output torque and the third harmonic current is established and its optimal value for maximizing the output torque is derived. It is found that the optimal third harmonic current is dependent on the ratio of the third harmonic back electromotive force (EMF) to the fundamental one but it is not 1/6 of the fundamental one as pulse width modulation in an inverter. In order to improve the output torque by increasing the fundamental and third harmonic winding factors and the third harmonic airgap flux density, the unequal width tooth and permanent magnet (PM) segmentation are employed in the 10-slot/8-pole five-phase SPM machine. The optimal unequal tooth dimensions and the number of PM segmentations are analyzed for maximizing the output torque. The airgap flux density, back EMF, cogging torque, and output torque of the machine with equal/unequal tooth width and unsegmented/segmented PM are compared. Finally, the experiments on the prototype 10-slot/8-pole PM machine with unequal tooth width and segmented rotor are given to verify the analytical and finite element analyses.

Maximum Reachable Torque, Power and Speed for Five-Phase SPM Machine With Low Armature Reaction

In this paper, the study of the torque and power versus speed characteristics for a family of five-phase surface-mounted permanent magnet machine is carried out. With considering hypotheses [linear magnetic modeling, only first and third harmonic terms in the back electromotive force (EMF) and current spectrums], an optimization problem that aims to maximize the torque for given maximum peak voltage and root mean square (RMS) current is formulated: the optimal torque sharing among the two virtual machines (the two dq -axis subspaces) that represent the real five-phase machine is thus calculated for any mechanical speed. For an inverter and a dc voltage sized with only considering the first harmonic of back EMF and current, the problem is solved with changing the virtual machine back EMFs and inductances ratios. With the introduction of the maximum torque/speed point, maximum power/speed point, and maximum reachable speed, it can be shown that, if the inductance ratio is large enough for given Volt–Ampere rating, the machine can produce higher torque without reducing its speed range, thus meaning that the capability of the inverter to work is improved with the use of the third harmonic. This property is all the truer as the base armature reaction is large. A particular five-phase machine is sized and numerically analyzed to check this property.

Geometry Optimization of Five-Phase Permanent Magnet Synchronous Motors using Bees Algorithm

Among all types of electrical motors, Permanent Magnet Synchronous Motors (PMSMs) are reliable and efficient motors in industrial applications. Because of their superiority over other kinds of motors, they are replacing conventional electric motors. On the other hand, high-phase PMSMs are good candidates to be used in certain industrial and military projects such as electric vehicles, spacecrafts, naval systems and etc. In these cases, the motor has to be designed with minimum volume and high torque and efficiency. Design optimization can improve their features noticeably, thus reduce volume and enhance performance of motors. In this paper, a new method for optimum design of a five-phase surface-mounted permanent magnet synchronous motor is presented to achieve minimum Permanent Magnets (PMs) volume with an increased torque and efficiency. Design optimization is performed in search for optimum dimensions of the motor and its permanent magnets using Bees Algorithm (BA). The design optimization results in a motor with great improvement regarding the original motor which is compared with two well- known evolutionary algorithms i.e. GA and PSO. Finally, finite element method simulation is utilized to validate the accuracy of the design.

Torque Improvement of Five-Phase Surface-Mounted Permanent Magnet Machine Using Third-Order Harmonic

This paper presents optimal third harmonics in both permanent magnet (PM) shaping and current waveform to improve the output torque of five-phase surface-mounted PM (SPM) machines. The optimal value of third harmonic injected into the sinusoidal PM shape and current waveform for maximum torque improvement is analytically derived and validated by both finite element (FE) analyses and experiments. It is found that the optimal third harmonic is 1/6 of the fundamental one for both PM shape and current waveform. For the five-phase SPM machines having rotors without shaping, Sine shaping, or Sine shaping with third harmonic injected, the electromagnetic performance including the back EMF waveform, cogging torque, average torque, torque ripple, copper loss, iron loss, impact on power inverter, and demagnetization withstand capability are compared. It is demonstrated that, although the copper loss and iron loss increase due to additional third harmonic in the winding current and magnet shape, the average torque with optimal third harmonics injected in PM shaping and current waveform can be improved by >30% while the torque ripple and remains similar to that of the one with Sine shaping. In addition, this will reduce the dc bus voltage while maintaining the machine torque density. Furthermore, the machine with Sine and Sine+3rd rotors presents much better demagnetization withstand capability performance than conventional rotor.

Optimum Design of a Five-phase Permanent Magnet Synchronous Motor for Underwater Vehicles by use of Particle Swarm Optimization

Permanent magnet synchronous motors are efficient motors which have widespread applications in electric industry due to their noticeable features. One of the interesting applications of such motors is in underwater vehicles. In these cases, reaching to minimum volume and high torque of the motor are the major concern. Design optimization can enhance their merits considerably, thus reduce volume and improve performance of motors. In this paper, a new method for optimum design of a five-phase surface-mounted permanent magnet synchronous motor is presented to achieve minimum loss and magnet volume with an increased torque. A multi-objective optimization is performed in search for optimum dimensions of the motor and its permanent magnets using particle swarm optimization. The design optimization results in a motor with great improvement regarding the original motor. Finally, finite element analysis is utilized to validate the accuracy of the design.

Optimum Design of a Five-Phase Permanent Magnet Synchronous Motor for Underwater Vehicles by use of Particle Swarm Optimization

Permanent magnet synchronous motors are efficient motors which have widespread applications in electric industry due to their noticeable features. One of the interesting applications of such motors is in underwater vehicles. In these cases, reaching to minimum volume and high torque of the motor are the major concern. Design optimization can enhance their merits considerably, thus reduce volume and improve performance of motors. In this paper, a new method for optimum design of a five-phase surface-mounted permanent magnet synchronous motor is presented to achieve minimum loss and magnet volume with an increased torque. A multi-objective optimization is performed in search for optimum dimensions of the motor and its permanent magnets using particle swarm optimization. The design optimization results in a motor with great improvement regarding the original motor. Finally, finite element analysis is utilized to validate the accuracy of the design. DOI: http://dx.doi.org/10.11591/telkomnika.v10i5.1176