Optimum Injected Harmonics Into Magnet Shape in Multiphase Surface-Mounted PM Machine for Maximum Output Torque
TL;DR: The optimal harmonics of different orders for maximum torque is mathematically derived and validated by the finite element (FE) method in this paper and the five-phase machine with third and fifth harmonics injection into the rotors is prototyped to verify the analytical and FE analyses.
Abstract: Harmonics can be injected into the permanent magnet (PM) shape to maximize the output torque in five-phase machines. The optimal harmonics of different orders for maximum torque is mathematically derived and validated by the finite element (FE) method in this paper. The output torque of the five-phase machine with sinusoidal shape can be improved by 12.5% by injecting the optimal third harmonic. Meanwhile, 3.2% further more torque improvement can be obtained with the optimal third and fifth harmonics injected. However, the output torque barely change with the seventh harmonic injection. The torque ripple of the machines with shaped PMs is much lower than the machines with conventional tile PM. The electromagnetic performance for all the machines including back electromotive force, average torque, torque ripple, etc., are compared. Finally, the five-phase machine with third and fifth harmonics injection into the rotors is prototyped to verify the analytical and FE analyses.
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TL;DR: A multiple reference frame (MRF) based controller for torque ripple minimization (TRM), in which the measured speed ripple is explored as the feedback control signal, which is capable of TRM under both steady-state and transient conditions.
Abstract: Torque ripple has been a critical issue for high-performance applications using permanent magnet synchronous machines (PMSMs). An efficient approach to minimize torque ripple is to control the stator current to follow an optimized current reference, which will produce an extra torque ripple to cancel the existing one. This paper proposes a multiple reference frame (MRF) based controller for torque ripple minimization (TRM), in which the measured speed ripple is explored as the feedback control signal. The proposed MRF-based controller consists of a TRM controller whose task is to find the optimal current reference and a current controller whose task is to control the actual current to follow the optimized current reference. In TRM controller, the control of reference current magnitude and phase angle is decoupled, and proportional integral (PI) controller is able to achieve TRM control. In current controller, MRF is adopted to convert harmonic current control into dc current control; thus, PI controller is able to achieve harmonic current control with the use of MRF. Compared with existing approaches, the proposed controller is capable of TRM under both steady-state and transient conditions. The proposed controller is experimentally evaluated on a laboratory PMSM drive system.
56 citations
Cites background from "Optimum Injected Harmonics Into Mag..."
...IN permanent magnet synchronous machines (PMSMs), torque ripple has been a critical issue that could prevent them from high-performance applications [1]–[5]....
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TL;DR: In this article, the advanced inverse cosine function (AICF) based on the ICF is proposed to reduce the torque ripple while improving efficiency and the control performance of an interior permanent magnet synchronous motor.
Abstract: This paper proposes a new numerical formula and a design method to reduce the torque ripple while improving efficiency and the control performance of an interior permanent magnet synchronous motor In previous studies, the inverse cosine function (ICF) has been used for torque ripple reduction by making the air gap flux density distribution sinusoidal under a no-load condition However, in this paper, the advanced inverse cosine function (AICF) based on the ICF is proposed It determines an asymmetric rotor shape for rendering the air gap flux density distribution sinusoidal, considering a certain load condition In addition to the torque ripple reduction, lower peak values, the total harmonic distortion (THD) of the induced voltage, and a lower iron loss can be achieved by applying the AICF, compared to the other conventional methods The lower peak value and THD of the induced voltage are important because they affect the control performance of the motor The lower iron loss can also lead to a higher efficiency, particularly, in the high-speed region To verify the validity of the proposed design method, the characteristics of 8-pole, 12-slot motors that have different rotor shapes are analyzed using finite element analysis and experiments
55 citations
Cites methods from "Optimum Injected Harmonics Into Mag..."
...Currently, two main methods for reducing the torque ripple are being investigated [4]....
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TL;DR: A testing-based approach for optimal harmonic current design by using the speed harmonics, which has advantages in terms of computation efficiency and simple implementation and is evaluated on a laboratory PMSM drive system.
Abstract: Torque ripple has been a critical issue in permanent magnet synchronous machines (PMSMs). After PMSMs are designed, an efficient way for torque ripple minimization is to inject an optimized harmonic current into the machine to produce an additional torque ripple to cancel existing torque ripple resulted from the imperfection of machine design and manufacturing. This paper proposes a testing-based approach for optimal harmonic current design by using the speed harmonics. In particular, two testing solutions (TS), TS-A and TS-B, are proposed. In TS-A, two test signals are injected into the machine, and the optimal harmonic current is calculated from the test signals as well as the measured speed harmonics. In TS-B, two test signals are injected and adjusted to achieve the designed objective in terms of speed harmonics, and the optimal harmonic current is calculated from only the test signals. These two solutions can find the optimal harmonic current to minimize the torque ripple with minimal machine losses. Moreover, machine parameters are not required in the optimal harmonic current design, so the proposed solutions are not affected by the machine and drive nonlinearities. Compared with existing approaches, the proposed solutions have advantages in terms of computation efficiency and simple implementation. The proposed solutions are evaluated on a laboratory PMSM drive system.
39 citations
Cites methods from "Optimum Injected Harmonics Into Mag..."
...In the machine design stage, torque ripple in PMSM can be reduced by optimizing the geometric structure of the stator and rotor of the machine [9], [10]....
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TL;DR: A modeling approach and an optimization strategy to exploit a third-harmonic current injection for the torque enhancement in multiphase isotropic permanent magnet synchronous machines with nonsinusoidal back electromotive forces are proposed.
Abstract: This article proposes a modeling approach and an optimization strategy to exploit a third-harmonic current injection for the torque enhancement in multiphase isotropic permanent magnet synchronous machines with nonsinusoidal back electromotive forces. The modeling approach is based on a proper vector space decomposition and on the associated rotational transformation, aimed to properly select a set of stator current space vectors to be controlled. It is presented for a generic (i.e., asymmetrical, with an arbitrary angular shift) winding configuration. The injection strategy is related to the choice of a constant synchronous current set aimed at minimizing the average stator winding losses for a given reference torque by using the first and the third spatial harmonics of the air-gap flux density. The optimal solution has been found analytically and has been developed in detail for a selected set of asymmetrical winding configurations. Both the numerical and experimental results are in good agreement with the theoretical analysis.
30 citations
TL;DR: The total torque can be enhanced by optimal angles of shifted SPMs and assisted airspace barriers because of higher utilization of both PM torque and reluctance torque.
Abstract: This paper reveals a torque-angle approaching principle in a hybrid rotor permanent-magnet (HRPM) motor. The key is to obtain the relationship between angles of shifted surface-inserted PMs (SPMs) as well as assisted airspace barriers and the current angles of maximum PM torque as well as maximum reluctance torque. In order to find out this relationship, the PM torque and reluctance torque are separated accurately and effectively by the proposed torque separation method. In this method, the parameters in an abc reference frame are transformed to a d- - q reference frame via Park transformation, and then the model considering cross-coupling and magnetic saturation effect is used to calculate four torque components. Moreover, the shifting of SPMs has been confirmed to have both influence on the current angles of maximum PM torque and maximum reluctance torque, while the assisted airspace barriers only affect the current angle of maximum reluctance torque. Thus, the total torque can be enhanced by optimal angles of shifted SPMs and assisted airspace barriers because of higher utilization of both PM torque and reluctance torque. In order to evaluate the presented principle in the HRPM motor, a prototype is manufactured for experiments. Through theoretical analysis and experimental testing, it is verified that the proposed principle is feasible and effective.
27 citations
References
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TL;DR: An attempt is made to provide a brief review of the current state of the art in the area of variable-speed drives, addressing the reasons for potential use of multiphase rather than three-phase drives and the available approaches to multiphases machine designs.
Abstract: Although the concept of variable-speed drives, based on utilization of multiphase machines, dates back to the late 1960s, it was not until the mid- to late 1990s that multiphase drives became serious contenders for various applications. These include electric ship propulsion, locomotive traction, electric and hybrid electric vehicles, ldquomore-electricrdquo aircraft, and high-power industrial applications. As a consequence, there has been a substantial increase in the interest for such drive systems worldwide, resulting in a huge volume of work published during the last ten years. An attempt is made in this paper to provide a brief review of the current state of the art in the area. After addressing the reasons for potential use of multiphase rather than three-phase drives and the available approaches to multiphase machine designs, various control schemes are surveyed. This is followed by a discussion of the multiphase voltage source inverter control. Various possibilities for the use of additional degrees of freedom that exist in multiphase machines are further elaborated. Finally, multiphase machine applications in electric energy generation are addressed.
1,683 citations
"Optimum Injected Harmonics Into Mag..." refers background in this paper
...MULTIPHASE machines have obtained wide applications due to their high torque density and high reliability, ranging from electrical vehicle to aerospace, where the volume and weight are significant [1]....
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...Most literature focuses on the technique of the current injection to maximize the output torque [1]–[4]....
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TL;DR: A wide range of motor- and controller-based design techniques that have been described in the literature for minimizing the generation of cogging and ripple torques in both sinusoidal and trapezoidal PMAC motor drives are reviewed.
Abstract: Permanent magnet AC (PMAC) motor drives are finding expanded use in high-performance applications where torque smoothness is essential. This paper reviews a wide range of motor- and controller-based design techniques that have been described in the literature for minimizing the generation of cogging and ripple torques in both sinusoidal and trapezoidal PMAC motor drives. Sinusoidal PMAC drives generally show the greatest potential for pulsating torque minimization using well-known motor design techniques such as skewing and fractional slot pitch windings. In contrast, trapezoidal PMAC drives pose more difficult trade-offs in both the motor and controller design which may require compromises in drive simplicity: and cost to improve torque smoothness. Controller-based techniques for minimizing pulsating torque typically involve the use of active cancellation algorithms which depend on either accurate tuning or adaptive control schemes for effectiveness. In the end, successful suppression of pulsating torque ultimately relies on an orchestrated systems approach to all aspects of the PMAC machine and controller design which often requires a carefully selected combination of minimization techniques.
978 citations
"Optimum Injected Harmonics Into Mag..." refers methods in this paper
...Lots of techniques have been employed to obtain low torque ripple by modifying the stator or rotor parameters [5]....
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TL;DR: In this article, a five-phase brushless permanent magnet motor with concentrated windings has been proposed, where the produced back electromotive force is almost trapezoidal and the motor is supplied with the combined sinusoidal plus third harmonic of currents.
Abstract: A five-phase brushless permanent-magnet (PM) motor is introduced. The proposed motor has concentrated windings such that the produced back electromotive force is almost trapezoidal. The motor is supplied with the combined sinusoidal plus third harmonic of currents. This motor, while generating the same average torque as an equivalent PM brushless dc motor (BLDC), overcomes its disadvantages. The motor equations are obtained in the d/sub 1/q/sub 1/d/sub 3/q/sub 3/0 rotating reference frame. Therefore, the so-called vector control is easily applicable to this kind of motors and the motor has the same controllability as a PM synchronous motor (PMSM). For presenting the superior performance of the proposed five-phase motor, its three and five-phase PMSM and BLDC counterparts are also analyzed. Finite element method is used for studying the flux density and calculating the developed static torque. Also, the developed torque is obtained using the mathematical model in the d-q reference frame. The average torque and the torque ripple for all cases are calculated and compared. Experimental results are in good agreement with the simulation results.
428 citations
TL;DR: A control strategy that provides fault tolerance to five-phase permanent-magnet motors is introduced and will guarantee high efficiency, high performance, and high reliability, which are required for automotive applications.
Abstract: Multiphase interior permanent magnet (IPM) motors are very good candidates for hybrid electric vehicle applications. High torque pulsation is the major disadvantage of most IPM motor configurations. A five-phase IPM motor with low torque pulsation is discussed. The mathematical model of the five-phase motor is given. A control strategy that provides fault tolerance to five-phase permanent-magnet motors is introduced. In this scheme, the five-phase system continues operating safely under loss of up to two phases without any additional hardware connections. This feature is very important in traction and propulsion applications where high reliability is of major importance. The system that is introduced in this paper will guarantee high efficiency, high performance, and high reliability, which are required for automotive applications A prototype four-pole IPM motor with 15 stator slots has been built and is used for experimental verification.
295 citations
TL;DR: Analysis was made to combine the modeling efforts with the expected behavior concerned with mutual inductance and armature reaction effects, so as to have realistic simulation results verified by the experimental setup.
Abstract: This paper presents the design, analysis, simulation, and modeling of a high-torque low-speed multiphase permanent-magnet brushless; machine. The machine fits an in-wheel motor arrangement to be used for electric vehicle applications. This paper presents issues regarding the high-level modeling comprised of a transient model in conjunction with their corresponding experimental evaluation. Analysis was made to combine the modeling efforts with the expected behavior concerned with mutual inductance and armature reaction effects, so as to have realistic simulation results verified by the experimental setup. Comprehensive experimental results corroborate the work.
121 citations
"Optimum Injected Harmonics Into Mag..." refers background in this paper
...Most literature focuses on the technique of the current injection to maximize the output torque [1]–[4]....
[...]