Five-phase Permanent Magnet Motor Research Articles

Temperature field analysis and equal-amplitude temperature rise constraint current control method under open-circuit fault-tolerant operation for five-phase permanent magnet motor

The phase redundancy and freedom of the five-phase permanent magnet motor (FPPMM) enhance the reliability of the motor system. However, the temperature rise and torque reduction issues of the motor during open-circuit fault operation need to be further studied. In order to study the temperature distribution characteristics and the output capability of the motor under fault operation subject to temperature rise constraints, a 3-D global temperature field model containing a complex heat dissipation structure has been established. And the equal-amplitude temperature rise constraint current control method is proposed under open-circuit fault-tolerant operation to improve its output capability. The temperature distribution of the motor during steady state operation under rated operating conditions is analyzed with emphasis. Based on this, the temperature field changes of the motor during single-phase and two-phase open-circuit fault-tolerant operation are investigated. Then, the proposed equal-amplitude temperature rise constrained current method is introduced in detail to ensure the safe operation of the motor. An experimental platform is built, which verifies the accuracy of the temperature field calculation, as well as the correctness of equal-amplitude temperature rise constrained current method.

Single-phase Open-circuit Fault-tolerant Control for a Dual Five-phase Permanent Magnet Motor with Multi-operational Modes

Single-phase Open-circuit Fault-tolerant Control for a Dual Five-phase Permanent Magnet Motor with Multi-operational Modes

Disturbance-Observer-Based Direct Torque Control of Five-Phase Permanent Magnet Motor Under Open-Circuit and Short-Circuit Faults

Multiphase permanent magnet (PM) motors are popularly adopted for their high torque density, high efficiency, and good fault tolerance. Open-circuit and short-circuit faults can result in high fluctuating torque and deteriorated dynamic performance. This article proposes a novel direct torque control (DTC) approach based on disturbance observer (DOB) to minimize the torque pulsations and enhance dynamic performance of a five-phase PM motor under open-circuit and short-circuit fault conditions. The novelty of the proposed strategy is the development of fault-tolerant switching table based on closed-loop mode of third harmonic current regulation and the incorporation of DOB. Based on the switching table, the proposed method can restrain the torque fluctuations caused by open-circuit fault and suppress y-axis current. The DOB is introduced to eliminate the external disturbances, which include torque fluctuations caused by short-circuit current and unmodel dynamic. Then, the proposed strategy is applicable to the PM motor, whose back electromotive force contains third harmonic, under open-circuit or short-circuit fault condition. This fault-tolerant DTC strategy can not only smooth fluctuating torque and ensure that its dynamic performance reaches the healthy performance, but also enhance the robustness against the external disturbances under both open-circuit and short-circuit fault conditions. The simulation and experimental results are presented to validate the proposed strategy.

Comparative Analysis of Three-phase and Five-phase Permanent-magnet Motor Based on Finite Element Method

Permanent-magnet motors are suitable choice for special applications such as aircrafts, marine, and electric vehicles Because of the fault tolerance and high power density capability. In this paper, an analytical design of a five-phase permanent-magnet motor is done and the advantages of multi phase motor over three phase motor are studied. Next Finite-element method is applied to verify and validate different machine designs. Finally thermal analysis of the designed machines is done. The results are shown multi phase motor has lower cogging torque and operation temperature, higher electromagnetic torque and back-emf in comparison with three phase motor.

Unified Decoupling Vector Control of Five-Phase Permanent-Magnet Motor With Double-Phase Faults

Multi-phase permanent-magnet (PM) motor is a competitive candidate for application where uninterrupted operation is demanded under fault condition. However, double-phase open-circuit or short-circuit faults result in serious problems, such as high fluctuating-torque, deteriorated dynamic performance, even breakdown. This paper proposes a novel unified decoupling vector control strategy to restrain torque fluctuations and improve dynamic performance for a five-phase PM motor with arbitrary double-phase failures. The novelty of the proposed strategy is the development of reduced-order orthogonal transformation matrices and remedies voltages, and then the smooth operation with vector control strategy can be achieved under double-phase open-circuit or short-circuit fault condition. The decoupled motor model in the synchronous rotating frame is achieved by the combination of the reduced-order orthogonal transformation matrices deduced from the optimal fault-tolerant currents and the remedy voltages. The torque fluctuations cancellation is achieved by the remedy voltages. This control strategy exhibits the improved dynamic performance with smooth torque of the faulty PM motor. The experimental results are presented to verify the feasibility of the proposed strategy.

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.

Simplified Fault-Tolerant Model Predictive Control for a Five-Phase Permanent-Magnet Motor With Reduced Computation Burden

This article proposes a fault-tolerant finite control set model predictive control for a five-phase permanent-magnet (PM) motor drive, which offers reduced computation burden and simplified control model. The virtual voltage vectors synthesized from two basic vectors are used to reduce the computation burden. Meanwhile, the steady-state performance is improved. Combining with a reduced decoupling matrix, the discrete model of the five-phase PM motor before and after fault remains unchanged. So, the reconfiguration of the control structure is minimal. Then, a control set and corresponding switching sequence are proposed, which are very suitable for the real-time system. Finally, the validity of the proposed fault-tolerant control is proved by experiments.

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.

Dynamic Performance Improvement of Five-Phase Permanent-Magnet Motor With Short-Circuit Fault

Multiphase permanent-magnet (PM) brushless motors are popularly adopted for their high efficiency and high power density. However, short-circuit phase fault results in serious problems, such as increased torque fluctuations and deteriorated dynamic performance. This paper proposes a new vectorial approach to minimize pulsating torque and improve dynamic performance in a five-phase PM motor with short-circuit fault. The novelty of the proposed strategy is voltage feedforward compensation based on the relation of the short-circuit current and its fault-phase back electromotive force. First, the compensatory voltages are used to eliminate the impact of the short-circuit current. Then, its combination with the orthogonal reduced-order transformation matrices derived from fault-tolerant current references can improve the dynamic performance of the faulty PM motor. The effect of the short-circuit phase fault on the PM motor model under rotating synchronous frame is also discussed. This control strategy allows minimal reconfiguration of the control structure from healthy operation to fault-tolerant one and exhibits the improved dynamic performance. The simulated and experimental results are presented as validation for the proposed strategy.

Cancellation of Torque Ripples With FOC Strategy Under Two-Phase Failures of the Five-Phase PM Motor

This paper investigates torque ripples cancellation of a five-phase (5Ph) permanent magnet (PM) motor under open fault of two phases, where failure phases are either adjacent or nonadjacent. In recent works, torque ripples cancellation is performed at a stationary frame and postfault current solutions for constant output torque are complicated. To implement field-oriented control (FOC) and carrier-based pulse width modulation, reduced-order Clarke and Park transformations are proposed. With the coordinate transformation, a 5Ph motor model under unbalanced conditions has been decoupled. Along with this, the fundamental torque at the d-q frame also remains the same as the healthy case. However, third harmonic of winding density distribution results in torque ripples. To reduce dependence on mathematical model of torque ripples, sliding mode control is employed to calculate q -axis current reference while keeping constant the rotor speed. Decoupled models corresponding to two types of faults, which are adjacent and nonadjacent open fault, are confirmed by finite element analysis, and effectiveness of proposed torque ripples cancellation method is verified on the 5Ph drive in the laboratory.

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.

자이로 구동기를 위한 자기베어링 구조의 토로이달 형 회전자 제어

This paper deals with the position and torque control of a toroidal type rotor which has a magnetic bearing structure. The proposed magnetic bearing structure supports the rotor by the repulsive forces of permanent magnets, and has a two degree of freedom for rotor position when the rotor is rotating. Permanent magnets and coils in the stator allow for a two degree of freedom control of the rotor position and torque generation by reacting with permanent magnets of the rotor. The executed gyro actuator has a number of poles such as five-phase permanent magnet motors and 10 stator coils for the rotor position control. In this study, the verification of the stability of the magnetic bearing was conducted using the equation of motion when the rotor was rotating, and the coil current commutation method for the position control and torque generation was studied. As a result, the feasibility of the proposed structure and control was verified by simulations of Finite Element Method (FEM) and experiments using the executed gyro actuator.

Observer‐based open transistor fault diagnosis and fault‐tolerant control of five‐phase permanent magnet motor drive for application in electric vehicles

To meet increasing demand for higher reliability in power electronics converters applicable in electric vehicles, fault detection (FD) is an important part of the control algorithm. In this study, a model-based open transistor fault diagnsosis method is presented for a voltage-source inverter (VSI) supplying a five-phase permanent magnet motor drive. To realise this goal, a model-based observer is designed to estimate model parameters. After that, the estimated parameters are used to design a sliding mode observer in order to estimate the phase current in an ideal model. Subsequently, the proposed FD technique measures the similarity between the estimated current and real current using cross-correlation factor. This factor is used for the first time in this study to define a FD index in VSI. The presented FD scheme is simple and fast; also, it is able to detect multiple open switch or open phase faults in contrast to conventional methods. On the other side, in order to track reference current of the motor, the estimated parameters are used to design a proportional resonant controller. The FD technique is used to operate a multiphase fault-tolerant brushless direct current (BLDC) motor drive. Experimental results on a five-phase BLDC motor with in-wheel outer rotor applicable in electrical vehicles are conducted to validate the theory.

A Generalized Fault-Tolerant Control Strategy for Five-Phase PM Motor Drives Considering Star, Pentagon, and Pentacle Connections of Stator Windings

In this paper, a generalized optimal fault-tolerant control (FTC) technique is proposed for open-circuit faults in five-phase permanent-magnet (PM) machine drives. The proposed FTC technique considers pentagon and pentacle connections of stator windings in addition to conventional star connection. Open-circuit faults in stator windings of the machine as well as switches of the inverter are analyzed. The optimization objective is to produce ripple-free electromagnetic torque with minimum ohmic losses under open-circuit fault conditions. This is achieved by a simple closed-form equation to calculate reference optimal currents in all cases where a lookup table is utilized to represent the effect of fault type. The proposed FTC technique is easily extended to PM machines with higher number of phases. Experimental results for a five-phase PM machine drive are provided to demonstrate the proposed FTC strategy. In addition to single and double faults, which are analyzed for five-phase machine with star connection, triple-phase faults are also considered in pentagon and pentacle connections.

A Unified Fault-Tolerant Current Control Approach for Five-Phase PM Motors With Trapezoidal Back EMF Under Different Stator Winding Connections

A unified approach for fault-tolerant current control of five-phase permanent-magnet (PM) motors with trapezoidal back EMF is proposed for open-circuit phase and line faults. In addition to conventional star connection, five-phase PM motors can be connected in two penta-type connections, pentagon and pentacle. In the proposed unified approach, a general solution for fault-tolerant currents is presented which uses only the fundamental and third-harmonic current components for the excitation of the healthy stator phases. The proposed approach is based on mirror symmetry of healthy phase current with respect to the fault location and it is optimized to increase output average torque while reducing torque pulsations and minimizing ohmic losses. A general parametric solution is presented which can be applied to five-phase motor drives with any fault condition and winding connection by selecting proper optimization constraints. It is shown that penta-type connection results in improved fault-tolerant capability in terms of maximum ripple-free torque due to the absence of zero-neutral current constraint. Experimental results are presented to verify the proposed solutions for fault-tolerant current control.

Thermal Analysis of a Five-Phase Motor Under Faulty Operations

This paper describes the thermal behavior of a five-phase permanent-magnet motor during the postfault control strategy, considering the open-circuit fault of both one and two phases. Proper current control strategies are applied to get proper performance under faulty operating conditions. The current of the healthy phases is contextually increased to get a higher average torque, but maintaining the same Joule losses of the healthy case. It is shown that such increase on the average current does not affect the thermal dissipation, and the motor can continue to operate properly also in faulty conditions. Experimental results confirm the simulation predictions.

Performance of Five-phase Motor Drive under Post-fault Operations

This article experimentally compares the post-fault performance of a five-phase permanent magnet motor drive, considering the open circuit fault of both one and two phases. The use of both a half-bridge and a full-bridge converter is considered. Proper current control strategies are applied to get proper performances under faulty operating condition. It is shown that the adoption of the full-bridge converter allows overcoming the constraint of having a zero sum of the currents, and this is particularly advantageous under the fault of two phases. All healthy and faulty operating conditions are experimentally tested.

Fault-Tolerant Control of Five-Phase Permanent-Magnet Motors With Trapezoidal Back EMF

This paper presents fault-tolerant control techniques for five-phase permanent-magnet motors with trapezoidal back electromotive forces under various open-circuit conditions. The proposed fault-tolerant control methods use only the fundamental and third-harmonic current components for the excitation of the healthy stator phases. The control techniques are developed by applying a concept that correlates the currents in the healthy phases based on their symmetry in space with respect to the fault in a machine. Optimum solutions under the single-phase open-circuit fault condition and double-phase open-circuit fault conditions are presented. The presented solutions are derived to increase the average output torque while reducing the torque pulsations and satisfying the zero-neutral-current constraint. Detailed experimental results are presented for the verification of the proposed solutions.

A New Control Strategy of Five-Phase Permanent-Magnet Motor Drives with a Third Harmonic Current Injection

In this paper, a five-phase permanent-magnet (PM) brushless dc (BLDC) motor is investigated, which has almost trapezoidal back electromotive force(EMF) due to its concentrated windings. Since the third harmonic component in the magnetic field is utilized, the presented five-phase BLDC motors have a higher torque density over conventional three-phase ones, in which the third harmonic current is injected. This paper proposes a new five-phase transformation system, by which the vector control is easily applicable to five-phase BLDC motors. Finally, the results verify the validity of the proposed method.

Fault-Tolerant Interior-Permanent-Magnet Machines for Hybrid Electric Vehicle Applications

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.