Five-phase Motor Research Articles

Improved SVPWM Fault-Tolerant Control Strategy for Five-Phase Permanent-Magnet Motor

Multiphase permanent-magnet motors have received a lot of attention in the past few years owing to the merits of high power density, high efficiency and high fault-tolerant capability. Particularly, high fault tolerance is very desirable for safety-critical applications. This paper proposes an improved space vector pulse-width modulation (SVPWM) fault-tolerant control for five-phase permanent-magnet motors. First, generalized five-phase SVPWM fault-tolerant control is deduced and analyzed based on single-phase open-circuit fault, thus obtaining various SVPWM fault-tolerant control strategies and yielding a greatly increased capacity to enhance fault-tolerant performance of motor. Then, an improved SVPWM fault-tolerant control strategy with increased DC bus voltage utilization and reduced current harmonics is proposed and compared with the traditional one. Last, effectiveness and superiority of the proposed control strategy is verified by both simulation and experimental results on a five-phase permanent-magnet motor.

Predictive Torque Control Algorithm for a Five-Phase Induction Motor Drive for Reduced Torque Ripple With Switching Frequency Control

This article presents a progressive comparison of predictive torque control (PTC) algorithms for a five-phase induction motor fed with a two-level five-phase inverter. The extension of three-phase PTC to the five-phase motor, introduces current harmonics of the order 10n $\pm$ 3 (n = 0, 1, 2.. .), which are not responsible for torque/flux production. The inherent disadvantage of PTC is being a variable frequency algorithm, which adds complexity to the design of magnetic components. This disadvantage of PTC can be overcome by applying dwell time ( $t_{s}$ ) to the voltage vectors obtained through a minimum torque ripple condition, which is determined based on the ripple equation. In the proposed algorithm, a set of synthetic voltage vectors are generated and used for reducing flux and torque error through cost function. The use of synthetic voltage vector simplifies the cost function and further reduces the computation time. A two-step delay compensation is adopted to improve the precision of the control algorithm further. In each control cycle, an optimal switching time is calculated to reduce the torque ripple and to maintain the constant switching frequency. In this article, a modified PTC is proposed, which targets to achieve constant switching frequency, eliminate the xy-subspace current harmonics, reduce the torque ripple, and minimize the computational burden involved in the conventional predictive torque control algorithm. The experimental study is carried out on a laboratory prototype. The results show compliance with all the experimental study with different PTC algorithms with different sampling frequencies, and the modified cost function.

Reducing root‐mean‐square current stress on the DC link capacitor of a five‐phase electric drive through multiple carrier pulse‐width modulation technique

This study investigates the angle of phase shift between interleaved carriers in pulse-width modulation, as an additional design parameter to reduce the DC link stress of a five-phase drive. Several phase shift strategies are studied and defined with a focus on the DC link root-mean-square current. The effect of adjusting the phase shift between interleaved carriers on the DC link stress is analysed and a general mathematical model is proposed to estimate the effect for any phase shift strategy. The trends predicted by simulations and analytical models have been validated through the application of the control algorithm on a five-phase motor drive system.

Neural Network-Based Model Reference Adaptive System for Torque Ripple Reduction in Sensorless Poly Phase Induction Motor Drive

This paper proposes the modified, extended Kalman filter, neural network-based model reference adaptive system and the modified observer technique to estimate the speed of a five-phase induction motor for sensorless drive. The proposed method is generated to achieve reduced speed deviation and reduced torque ripple efficiently. In inclusion, the result of speed performance and torque ripple under parameter variations were analysed and compared with the conventional direct synthesis method. The speed estimation of a five-phase motor in the four methods is analysed using MATLAB Simulink platform, and the optimum method is recognized using time domain analysis. It is observed that speed error is minimized by 60% and torque ripple is reduced by 75% in the proposed method. The hardware setup is carried out for the optimized method identified.

A New Control Strategy of 5-Phase PM Motor under Open-Circuited Phase Based on High Order Sliding Mode and Current References Real-Time Generation

The high quality of electrical power in high power and high reliability applications is a crucial necessity even under fault mode function. However, in these conditions, the quality of the torque is a key feature. To overcome this problem, the multiphase permanent magnet (PM) motors seems to be a very attractive choice. In order to highlight the robustness and reliability of this technology, this paper investigates the control of a five-phase PM motor under an open circuited phase fault conditions. Moreover, a High Order Sliding Mode (HOSM) controller combined to an optimal reference current generation is tested and compared to a PID controller under fault mode conditions. This original control strategy is proposed for faulted conditions. Compared to classical fault tolerant control, this strategy allows a better dynamic tracking of the non-sinusoidal reference currents and leads to a smooth torque with minimal losses even in severe fault conditions. To validate the proposed control strategy, simulation, and experimental results are presented and discussed.

Four-Dimensional Space Vector PWM Strategy for Five-Phase Voltage Source Inverter

For a five-phase motor with non-sinusoidal windings arrangement, the electromagnetic torque can be enhanced by injecting third harmonic current. This paper studies the driving system and the fundamental and third harmonic spaces of the five-phase motor with non-sinusoidal windings, proposing a four-dimensional space vector PWM strategy based on modulation function method. According to the relationship of duty circle and modulation function of the periodic midpoint, for a symmetric regular sampling method, the phase modulation function can be obtained. It greatly simplifies the computational complexity and the occupied storage space. To deal with saturation, it only needs to limit the duty cycle or the amplitude of modulation function, which eliminates the complex division operation. To verify the correctness of the proposed method, the simulation and experiment are conducted on MATLAB/Simulink and hardware-in-the-loop simulation platform of RT-LAB/dSPACE, respectively. Finally, the phase current of the motor is analyzed with Fast Fourier Transform (FFT), showing the third harmonic content is basically the same as the set value.

Modeling and simulation of charging and braking regimes of AC/AC powertrain of HEV vehicle

The paper deals with modeling and simulation of chosen operational modes of HEV vehicle with direct AC/AC transfer and five-phase IM traction motors. Such configuration yields smaller voltage drops com-pared with the serial AC/DC/AC converter and five-phase machines offer some inherent advantages over their three-phase counterparts. The advantages include reduced electromagnetic torque pulsation and also noise characteristics of the five-phase drives are better when compared with the three-phase ones. Charging and braking regimes were chosen as possible operational modes for modeling and analyses. The result of the simulation. carried out with using of Matlab/Simulink are given in the paper.

Finite control set model predictive current control of a five-phase PMSM with virtual voltage vectors and adaptive control set

This paper presents an improved finite control set model predictive current control (FCS-MPCC) of a five-phase permanent magnet synchronous motor (PMSM). First, to avoid including all the 32 voltage vectors provided by a two-level five-phase inverter into the control set, virtual voltage vectors are adopted. As the third current harmonics can be much reduced by virtual voltage vectors automatically, the harmonic items in the cost function of conventional FCS-MPCC are not considered. Furthermore, an adaptive control set is proposed based on voltage prediction. Best control set with proper voltage vector amplitude corresponding to different rotor speed can be achieved by this method. Consequently, current ripples can be largely reduced and the system performs much better. At last, simulations are established to verify the steady and transient performance of the proposed FCS-MPCC, and experiments based on a 2 kW five-phase motor are carried out. The results have validated the performance improvement of the proposed control strategy.

Open-Phase Fault Detection of a Five-Phase Permanent Magnet Assisted Synchronous Reluctance Motor Based on Symmetrical Components Theory

This paper presents a novel approach for open-phase fault detection of a five-phase permanent magnet assisted synchronous reluctance motor (PMa-SynRM). Under faults, the five-phase PMa-SynRM is expected to run at fault-tolerant control (FTC) mode, otherwise it draws a large amount of current with a significant reduction in the reluctance torque. To successfully achieve FTC operation of five-phase PMa-SynRM, the accurate detection of a fault condition has to be preceded. With the best of these authors knowledge, the detection of faults has been limitedly studied for five-phase motors. The analysis of open-phase fault in five-phase machine involves complicated conditions including single-phase open fault, two-phase adjacent fault, and two-phase nonadjacent fault. To perform the timely fault-tolerant operation, those faults have to be accurately analyzed and detected. In this paper, a novel symmetrical components (SCs) analysis is utilized to extract the feature of those fault conditions. This analysis will provide the types of faults by logically analyzing the pattern of magnitude and phase angle changes of the fundamental signal in the SCs. The proposed method has been comprehensively analyzed through theoretical derivation, finite-element simulations, and experimental testing through a 5 hp PMa-SynRM controlled by TI-DSP F28335.

Comparative analysis of three-phase to five-phase transformer connections

Five-phase supply is needed for supplying five-phase motor drive systems. Special transformer connection schemes have been developed over the years and reported in the literature to convert three-phase supply from the grid to obtain a balanced five-phase output which can be used to supply multiphase motor. In this paper, two existing transformer connections have been investigated and a new connection scheme has been proposed. Similar to the existing connection schemes, the proposed transformation system also employs three separate cores, each consisting of one primary and several secondary coils. The secondary coils comprise of different numbers of turns and are connected in specific ways so as to achieve the desired 72 degrees phase shift with equal magnitudes. The feasibility of the proposed scheme is proved using simulation and experimental approach. Moreover, a comparative analysis of the three solutions is presented.

Asymmetrical SVPWM Fault-Tolerant Control of Five-Phase PM Brushless Motors

In this paper, an asymmetrical space vector pulse-width modulation (SVPWM) fault-tolerant control is proposed for the five-phase permanent-magnet motor under the open-circuit condition of a single phase. The key of this method comes from two parts. First, the voltage vector diagram is rebuilt in the event of an open-circuit fault. Second, the switching signals constructing an asymmetry waveform are selected in one sector. Then, this asymmetrical SVPWM control can reduce the amplitude and total harmonic distribution of currents in healthy phases, though it has limitation for the open-circuit condition of two phases. Additionally, both simulated and experimental results are provided to validate the good performances of the proposed fault-tolerant drive, maintaining average torque, and low torque ripple during fault. Finally, the dynamic responses of open-loop and close-loop condition are measured. The results show that the proposed method can offer comparable dynamic performance of normal SVPWM control that is widely used in healthy five-phase motor drive.

An investigation of operating algorithms of a five-phase converter in the vector pulse-width modulation mode

Seven control algorithms of a five-phase converter running on a five-phase symmetrical load have been analyzed. A theoretical study of the formation of resultant rotating vector of current when implementing seven control algorithms has been carried out. The space of states of the resulting rotating vectors of a five-phase converter includes six switching sequences: three sequences of five keys, one sequence of three keys, and one sequence of two keys. Each of these switching sequences can be used to form a symmetrical five-phase voltage required for feeding a five-phase motor. The sequence of commutations that generate voltage that is symmetrical in time, but do not provide the formation of a circular rotating field using the five-phase winding, has been investigated. Experimental results confirming theoretical studies are given.

Space-Vector PWM With Common-Mode Voltage Elimination for Multiphase Drives

Switching common-mode voltage (CMV) generated by the pulse width modulation (PWM) of the inverter causes common-mode currents, which lead to motor bearing failures and electromagnetic interference problems in multiphase drives. Such switching CMV can be reduced by taking advantage of the switching states of multilevel multiphase inverters that produce zero CMV. Specific space-vector PWM (SVPWM) techniques with CMV elimination, which only use zero CMV states, have been proposed for three-level five-phase drives, and for open-end winding five-, six-, and seven-phase drives, but such methods cannot be extended to a higher number of levels or phases. This paper presents a general (for any number of levels and phases) SVPMW with CMV elimination. The proposed technique can be applied to most multilevel topologies, has low computational complexity and is suitable for low-cost hardware implementations. The new algorithm is implemented in a low-cost field-programmable gate array and it is successfully tested in the laboratory using a five-level five-phase motor drive.

Nonsinusoidal Power Supply Analysis for Concentrated-Full-Pitch-Winding Multiphase Induction Motor

This paper investigates a nonsinusoidal power supply technique for a multiphase motor with a concentrated full-pitch winding. The technique focuses on how to select harmonics, how to determine the harmonics ratio, and the effects on the air-gap and yoke flux densities. Generally, the third-harmonic current is utilized for the air-gap flux density optimization in a five-phase motor. However, the method has a negative effect on the yoke flux density, and the yoke iron width should be increased. Alternatively, this problem can be solved by providing more control freedom degrees of the motor with a phase number greater than five. A nine-phase motor is employed to achieve the air-gap and yoke flux density distribution optimization simultaneously. Moreover, the performance of both motors is compared in the sinusoidal and nonsinusoidal power supply modes. The analysis of the torque density and the efficiency demonstrates that a nonsinusoidal power supply is more suitable for a heavy-load operation. Theoretically obtained results are verified by experiments.

Electromagnetic/Thermal Design Procedure of an Aerospace Electric Propeller

Much attention is focused upon the integration of electric actuators in aerospace applications to accomplish many functions, including the propulsion one. Within this trend, this paper is aimed at the design, modeling, and optimization of a five-phase fractional-slot permanent-magnet synchronous motor to be integrated in an electrically propelled plane. Accounting for the fact that the design procedure concerns both electromagnetic and thermal features, an analytical formulation of the corresponding major design parameters is derived. Then, an electromagnetic/thermal finite-element analysis (FEA)-based investigation of the initial concept has led to an average temperature rise lower than the aerospace application limit one. An optimization of the initial design is achieved using a FEA-based iterative procedure that yields a 22.5% decrease of the stack length, resulting in a weight reduction of 22.6%.

Multiphase Transformer Modelling using Finite Element Method

In the year of 1970 saw the starting invention of the five-phase motor as the milestone in advanced electric motor. Through the years, there are many researchers, which passionately worked towards developing for multiphase drive system. They developed a static transformation system to obtain a multiphase supply from the available three-phase supply. This idea gives an influence for further development in electric machines as an example; an efficient solution for bulk power transfer. This paper highlighted the detail descriptions that lead to five-phase supply with fixed voltage and frequency by using Finite-Element Method (FEM). Identifying of specification on a real transformer had been done before applied into software modeling. Therefore, Finite-Element Method provides clearly understandable in terms of visualize the geometry modeling, connection scheme and output waveform.

Low Computational-cost determination of Vibrational Behavior: Application to Five-phase Flux-Switching Permanent-Magnet Motor

This paper presents a study of the vibrational behavior of a five-phase flux-switching permanent-magnet (FSPM) motor with a low computational-cost. Magnetic and mechanical models are sequentially considered to predict the acoustic noise generated by the structure. After the description of the motor, stress due to magnetic source is obtained by finite element simulations, particularly at the interface between the air-gap and the stator. Then, the most significant eigenmodes of the stator structure, obtained by finite element simulation and by experimental measurements, are presented to determine how the motor is then excited. Finally, from the knowledge of the magnetic excitations and the modal basis, an analytical model is proposed to determine the dynamic behavior of the stator outer surface, instead of a costly dynamic finite element analysis. This model is applied to the five-phase FSPM motor and validated by experimental measurements.

Investigation of a Five-Phase Dual-Rotor Permanent Magnet Synchronous Motor Used for Electric Vehicles

This paper presents a novel five-phase permanent magnet synchronous motor (PMSM), which contains dual rotors and a single stator, equivalent to two five-phase motors working together. Thus, this kind of motor has the potential of good fault tolerant capability and high torque density, which makes it appropriate for use in electric vehicles. In view of the different connection types, the inside and outside stator windings can be driven in series or parallel, which results in the different performances of the magnetomotive force (MMF) and torque under open-circuit fault conditions. By decomposing the MMF, the reason that torque ripple increases after open-circuit faults is explained, and the relationship between MMF and torque is revealed. Then, the current control strategy is applied to adjust the open-circuit faults, and the electromagnetic analysis and MMF harmonics analysis are performed to interpret the phenomenon that the torque ripple is still larger than in the normal situation. The investigations are verified by finite element analysis results.

Computer Aided Modeling and Analysis of Five-Phase PMBLDC Motor Drive for Low Power High Torque Application

In order to achieve high torque at low power with high efficiency, a new five-phase permanent magnet brushless DC (PMBLDC) motor design was analyzed and optimized. A similar three-phase motor having the sameD/Lratio (inner diameter (D) and length of the stator (L)) is compared for maximum torque and torque ripple of the designed five-phase PMBLDC motor. Maxwell software was used to build finite element simulation model of the motor. The internal complicated magnetic field distribution and dynamic performance simulation were obtained in different positions. No load and load characteristics of the five-phase PMBLDC motor were simulated, and the power consumption of materials was computed. The conformity of the final simulation results indicates that this method can be used to provide a theoretical basis for further optimal design of this new type of motor with its drive so as to improve the starting torque and reduce torque ripple of the motor.

Finite Element Modeling of Five Phase Permanent Magnet BLDC Motor for High Power Density Application

Fault-tolerant capability of electrical motor drives is an essential feature in applications such as automotive, aeronautic, and many others. A multi-phase permanent-magnet BLDC motor exhibits a high fault tolerant capability hence increasing the reliability, as it can be designed to reduce the fault occurrence as well as to operate indefinitely in the presence of fault. With multi independent phases, in the event of failure of one or more, the remaining healthy phases let the motor to operate properly. This paper presents finite element modeling and results of a five-phase permanent magnet brushless motor designed for high power density application. DOI: http://dx.doi.org/10.11591/ijpeds.v3i4.4184