Multiphase Permanent Magnet Synchronous Motor Research Articles

Model-Free Predictive Current Control of Five-Phase PMSM Drives

Model predictive control is highly dependent on accurate models and the parameters of electric motor drives. Multiphase permanent magnet synchronous motors (PMSMs) contain nonlinear parameters and mutual cross-coupling dynamics, resulting in challenges in modeling and parameter acquisition. To lessen the parameter dependence of current predictions, a model-free predictive current control (MFPCC) strategy based on an ultra-local model and motor outputs is proposed for five-phase PMSM drives. The ultra-local model is constructed according to the differential equation of current. The inherent relation between the parameters in the predictive current model and the ultra-local model is analyzed in detail. The unknowns of the ultra-local model are estimated using the motor current and voltage at different time instants without requiring motor parameters or observers. Moreover, space vector modulation technology is employed to minimize the voltage tracking error. Finally, simulations and experiments are conducted to verify the effectiveness of the MFPCC with space vector modulation. The results confirm that the proposed method can effectively eliminate the impact of motor parameters and improve steady-state performance. Moreover, this control strategy demonstrates good robustness against load variations.

Fuzzy logic based vector control of multi-phase permanent magnet synchronous motors

This paper presents a fuzzy-logic-based vector control for a five-phase permanent-magnet synchronous motor (PMSM). The high-performance of the proposed fuzzy logic control (FLC)-based PMSM drive are investigated and compared with the conventional proportional-integral (PI) controller at different conditions, such as step change in command speed and load, and robustness against machine parameter variations. Finally, Simulation results shows that FLC presents better performances and high robustness compared to the conventional PI controller.

Backstepping speed controller design for a multi-phase permanent magnet synchronous motor drive

This paper deals with the synthesis of a speed control strategy for a six-phase permanent magnet synchronous motor (PMSM) drive based on backstepping controller (BC). The Backstepping control is a systematic and recursive design methodology for nonlinear feedback control. The results demonstrate that backstepping controller has the advantage of rapid response, no overshoot and stability compared with PI controller.

An ampere‐second‐vector pulse width modulation technique and fault‐tolerant control for CSI11 fed five‐phase permanent magnet synchronous motor with multiple harmonic electromotive forces

AbstractWhen dealing with safety‐critical applications that involve multiphase permanent magnet synchronous motors (PMSMs), the current source inverter (CSI) is a superior choice compared with the voltage source inverter. The conventional technique of pulse width modulation (PWM) presents a challenge for CSI, particularly during faults. The fault‐tolerant control of multiphase PMSMs fed by CSIs has not been well investigated, particularly in situations involving double‐phase open‐circuit faults. Furthermore, fault‐tolerant control becomes more complex when the multiphase PMSM includes harmonic back electromotive forces (EMFs). To deal with these issues, an ampere‐second (AS) vector PWM technique is developed for a five‐phase PMSM powered by CSI11. The modulation ratio of the proposed PWM is identical to that of space vector PWM. The proposed method, however, is easier to implement. A fault‐tolerant control method using AS‐vector is proposed for single‐phase, adjacent double‐phase, and non‐adjacent double‐phase open‐circuit faults. Additionally, a method is developed to suppress the torque ripple that results from harmonic back‐EMFs during fault conditions. Compared without the torque ripple suppression method, during the speed rising, the proposed method can reduce torque ripple to 16.7%, 54.5%, and 37.5%, respectively. The experiments have confirmed the effectiveness of the proposed PWM technique and fault‐tolerant control method.

A Novel Dual-Redundancy Permanent Magnet Synchronous Motor With Small Teeth

A novel dual-redundancy permanent magnet synchronous motor (DRPMSM) with small teeth is proposed, which combines the advantages of fault-tolerant permanent magnet synchronous motor (PMSM) and multi-phase PMSM. When fractional slot concentrated winding (FSCW) is used in PMSM, no electromagnetic coupling can be realized by selecting a reasonable slot-pole (SP) combination and using single-layer (SL) winding. However, the goal of no electromagnetic coupling can also be achieved by adding small teeth in the common slot center between two adjacent phase windings under appropriate SP combination and double layer (DL) winding. Compared with the former method, the latter has smaller eddy current loss and a lower saturation level of the magnetic field caused by lower-order harmonics. In addition, the influence of small teeth on electromagnetic properties is analyzed. The correctness of the theoretical derivation is verified by simulation and experiment.

Research on High Frequency Vibration Reduction Using Carrier Phase Shifted PWM for 4-Module 3-Phase Permanent Magnet Synchronous Motor

This article investigates the effect of the carrier phase shifted pulsewidth modulation on the vibration reduction of inverter-fed multiphase permanent magnet synchronous motors. This approach reduces vibration by changing the order of the carrier harmonic-induced electromagnetic force on the stator. Experiments verify that this method can effectively suppress vibration at a specific carrier frequency, but the vibration reduction effect depends on the carrier frequency, the modal frequency of the motor and the phase-shifted angles.

Improved Multi-Stage Decoupling Space Vector Modulation for Asymmetrical Multi-Phase PMSM With Series Winding Connection

This article is devoted to developing a unique series-winding drive (SWD) topology, analyzing and implementing its control schemes for asymmetrical multiphase permanent magnet synchronous motor (PMSM). Proposed SWDs have higher voltage utilization than ordinary wye or delta connection, but vary with the number of inverter legs and connection sequence. Also, they have a simpler topology, fewer inverter legs, and power modules than the open-end winding drives. The article selects the typical asymmetrical six-phase (ASP) PMSM as the target. The complex space vector mapping is screened and simplified by unified hexadecimal coding for both eight-leg and seven-leg drives. Given the multiple suspaces in ASP-PMSM, a multistage decoupling space vector modulation scheme is proposed and improved for SWDs. It incorporates the processes of vector synthetization, cost function minimization, and zero-sequence compensation. Prototype fabrication and control experiments are carried out. Results show that the proposed MSD SVM is applicable to all connection sequences. It can suppress the harmonic current to a quite low level, in both steady-state and dynamic states. Also, this article discusses the current burden of the inverter and provides suggestions.

An nth Harmonic Current Suppression Method Based on the Impulse Current PWM Technique for a Multi-Phase Permanent Magnet Synchronous Motor Fed with a Current Source Inverter

Among the existing harmonic current suppression methods, it is difficult and complicated to suppress any nth harmonic current accurately for multi-phase permanent magnet synchronous motors (PMSMs). To solve this problem, this paper takes a five-phase dual-rotor PMSM fed with a current source inverter (CSI) as an example, and proposes an nth harmonic current suppression method based on the impulse current PWM algorithm. Firstly, the analysis is conducted and presented for the nth harmonic current in the mth harmonic space. Then, based on the Sliding Discrete Fourier Transformation (SDFT), a low-pass filter (LPF) named SDFT-LPF is designed. Additionally, the impulse current PWM technique for the five-phase CSI is realized. In this paper, the experiments have confirmed that the SDFT-LPF has good filter performance. Compared with the SVPWM, the impulse current PWM technique has the same DC-link current utilization rate, but it is easier to implement. Moreover, the proposed harmonic current control method can accurately control any nth harmonic current without changing the PWM technique, which has significantly reduced the complexity of the harmonic current control. Additionally, the proposed scheme is easy to implement and can be directly extended to the multiple harmonic current’s control.

Candidate Modulation Patterns Solution for Five-Phase PMSM Drive System

Model predictive control (MPC) schemes applied in multiphase permanent magnet synchronous motors (PMSMs) should provide the precise torque output and suppress the harmonic currents at the same time. Then, the trade-off between precise torque output and harmonic currents suppression is inevitable in the finite control set MPC (FCS-MPC). To provide an alternative to this problem, this article presents a new extension strategy of FCS-MPC applied in multiphase PMSMs. The novelty of this article includes two parts. First, the control sets are extended from the candidate voltage vectors to the candidate modulation patterns. These modulation patterns consist of switching signals with specific rules. The second one is the new cost function which realizes the harmonic current suppression with the modulation patterns selection. Two groups of modulation patterns are developed to assess the performance of this structure. The first group is called “semi-controlled modulation pattern” which could provide the precise voltage vectors in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha \beta $ </tex-math></inline-formula> subspace. The second group is called “fundamental torque-controlled modulation pattern” which could further suppress the harmonic currents. These two groups of modulation patterns could realize the required performance with a much lower switching frequency (SW). Moreover, the parameter mismatches in the harmonic subspace caused by the uncertainties of the system and errors in the parameter values are also compensated in the proposed MPC. Finally, the comparative experiments show the performance differences between two modulation patterns and those existing controllers.

Fault-tolerant model predictive control of six-phase permanent magnet synchronous hub motors

Permanent magnet synchronous hub motors (PMSHMs) have been gradually introduced into the applications of electric vehicles. On this basis, the six-phase motor has the characteristics of high reliability, high power density and low torque ripple. And its fault tolerance is a large advantage compared with the three-phase motor. The multi-phase permanent magnet synchronous motor is redundant due to the number of phases. When the motor fails, it does not have to stop running, merely adjust its control mode and enter the fault-tolerant compensation control algorithm to resume the operation of the system. The FCS-MPC algorithm can replace the cascade structure in the traditional control and eliminate the modulation module. This makes it have good steady-state performance. The speed response is also improved. It can be combined with multiple control objectives with strong flexibility by simply changing the objective function. The prediction model is compensated. Finally, the experimental results show the effectiveness of this method.

Virtual current vector‐based method for inverter open‐switch and open‐phase fault diagnosis in multiphase permanent magnet synchronous motor drives

Virtual current vector‐based method for inverter open‐switch and open‐phase fault diagnosis in multiphase permanent magnet synchronous motor drives

Direct Modulation Pattern Control for Dual Three-Phase PMSM Drive System

The additional harmonic currents in multiphase permanent magnet synchronous motors (PMSMs) have been widely discussed and suppressed by the virtual vectors (VVs). However, the concept of VVs would result in an increasing in the switching frequency and losing the controllability in the harmonic subspace. In this article, a novel direct modulation pattern control (DMPC) method is proposed to provide the further discussion on the lower switching frequency and the better harmonic current suppression. First, a deadbeat control concept is applied to calculate the reference voltage vectors in torque production. In dual three-phase PMSM, there are several switching patterns which could generate the reference voltage vector. The designs of these switching patterns are determined according to the demand. In fact, two design concepts under the structure of DMPC is proposed. One is called the low switching frequency design. The control sets of this design is several switching patterns with only one switching signal. Another is called the low THD design. The control sets of this design is two switching patterns with opposite harmonic voltage vectors. Second, the influence of these different switching patterns in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xy</i> currents is optimized by a cost function. Actually, there are two types of cost function. One is a multiobjective cost function, which is designed to regulate both the amplitude of switching patterns and suppress the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xy</i> currents. Another is derived from the first cost function that regulates only the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xy</i> currents. The amplitude is determined directly in the voltage vector calculation. Finally, the experimental results show a good performance of these control strategies, in terms of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">αβ</i> currents production, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xy</i> currents and the switching frequency reduction.

Modeling and fault diagnosis of multi-phase winding inter-turn short circuit for five-phase PMSM based on improved trust region

Multi-phase Permanent Magnet Synchronous Motors (PMSMs) are widely used in fault-tolerant control applications. As an electrical fault with a high probability, inter-turn short circuit (ITSC) fault seriously affects the reliability of five-phase PMSM. However, due to high coupling of fault parameters, most of the fault models and diagnosis methods in fault-tolerant control focus on one-phase winding ITSC fault of three-phase PMSM. In this paper, a novel model and a fault diagnosis method are proposed for multi-phase winding ITSC (MP-ITSC) of five-phase PMSM. First, by analysing the related physical parameters of the motor, a mathematic model of MP-ITSC fault is established. Then, a parameter estimation method based on improved trust region (ITR), which accelerates the convergence speed of trust region algorithm and reformulates the fault diagnosis as the extreme seeking for fault parameters is proposed to detect the ITSC fault level. Experimental results provide verification of the proposed model and fault diagnosis method.

Multiphase PMSM with Asymmetric Windings for Electric Drive

Multiphase permanent magnet synchronous motors (PMSM) are widely utilized in high power and high reliability electric propulsion systems. In electric propulsion systems, the motor may work at a low efficiency area for a long time, which increases energy consumption and reduces cruise range. In order to improve motor efficiency, this paper proposes a multiphase motor structure. The stator winding of proposed motor consists of three independent windings that have different rated speed and torque. In this paper, winding match mode, operation characteristic and efficiency characteristic are analyzed, and a torque distribution strategy with optimal efficiency is given. The results show that in propeller load such as electric aircrafts and ships, the proposed motor can reduce motor total loss and temperature rise in a drive cycle, which improves system efficiency, reliability and fault tolerance performance.

High Resistance Fault-Detection and Fault-Tolerance for Asymmetrical Six-Phase Surface-Mounted AC Permanent Magnet Synchronous Motor Drives

In the last decade, the interest for higher reliability in several industrial applications has boosted the research activities in multiphase permanent magnet synchronous motors realized by multiple three-phase winding sets. In this study, a mathematical model of an asymmetric surface-mounted six-phase permanent magnet synchronous motor under high resistance connections was developed. By exploiting the intrinsic properties of multiphase machines in terms of degrees of freedom, an improved field-oriented control scheme is presented that allows online fault detection and a quite undisturbed operating condition of the machine under high resistance connections. More specifically, the proposed strategies for online fault-detection and fault-tolerance are based on the use of multi-reference frame current regulators. The feasibility of the proposed approach was theoretically analyzed, then confirmed by numerical simulations. In order to validate experimentally the proposed strategies, the entire control system was implemented using TMS-320F2812 based platform.

Guaranteeing the fault transient performance of aerospace multiphase permanent magnet motor system: An adaptive robust speed control approach

To enhance the fault transient performance of aerospace multiphase permanent magnet synchronous motor (PMSM) system, an adaptive robust speed control is proposed regardless of the phase open-circuit (OC) and short-circuit (SC) fault in this paper, which can be applied for both the redundant motor system and fault tolerant motor system. For aerospace multiphase PMSM system, besides external load disturbance and system parameter perturbation, there inevitably exists the electromagnetic torque ripple in fault transient process, which can degrade the system performance and even cause the system instability. To cope with this issue, the electromagnet torque ripple of the multiphase PMSM system in fault transient process is first analyzed. Then, by considering the electromagnet torque fluctuation caused by fault transient as a system uncertainty, a novel adaptive robust speed control scheme is proposed, while the adaptive law is constructed to emulate the total system uncertainty bound, which include the load disturbance, the parameter variation, and the electromagnetic torque fluctuation due to fault transient. The resulting control can ensure the speed control performance even in fault transient process regardless of the uncertainty, in which no prior estimation of the uncertainty bound is required. In addition, the proposed adaptive robust speed control is demonstrated by a six-phase PMSM experimental platform. The novelty of this research is to explore a novel adaptive robust speed control to strengthen the fault tolerance performance of multiphase PMSM system even in fault transient process, which requires no prior estimation of the uncertainty bound.

Multiphase PMSM With Asymmetric Windings for More Electric Aircraft

This article presents a multiphase permanent magnet synchronous motor (PMSM) for the more electric aircraft propulsion. The stator winding of the motor is composed of multiple sets of multiphase windings with different parameters. The purpose of the motor design is to modify the distribution of the high-efficiency area of the motor by reasonably matching the winding parameters of each set, thereby making the motor more suitable for the working condition of more electric aircraft and improving the working efficiency of the motor. This article analyzes the selection principle of slot-pole combination and the influence that asymmetric windings have on the motor magnetic field. Three basic matching modes are proposed: equal torque matching, equal power matching, and equal speed matching. The motor model is established, with the external characteristics, efficiency, and dynamic response of different matching modes being compared and analyzed. The results show that equal torque matching and equal speed matching can reduce the total loss of the motor in a complete flight working condition, whereas equal power matching is not suitable for more electric aircraft.

Performance evaluation of multi-phase permanent magnet synchronous motor based on different winding configurations and magnetization patterns

Permanent magnet synchronous motor (PMSM) is the most reliable and efficient machine that widely used in robotics and automation, industrial applications, electric vehicles, home appliances, aircraft and aerospace technology due to its high efficiency, good dynamic performance and high torque density. In this paper, the influence of various types of winding configuration and different magnetization patterns in the performance of a five-phase PMSM is investigated. Three types of magnetization patterns such as radial magnetization (RM), parallel magnetization (PaM), and multi-segmented Halbach magnetization (SH) are applied to the five-phase 10-slot/4-pole PMSM during open-circuit and on-load conditions. A 2D finite element method (FEM) is intensively used in this investigation to model and predict the electromagnetic characteristics and performance of the PMSM. The detailed results from the finite-element analysis (FEA) on the cogging torque, induced back-emf, airgap flux density and electromagnetic torque are analysed. The induced back-emf of the machine is computed further into its harmonic distortions. Additionally, the skewing method for minimization of cogging torque of PMSM is proposed. From the results, it is observed that the five-phase, 10-slot/4-pole PMSM with double layer distributed winding and parallel magnetization gives the best machine performance.

Position sensorless direct torque control for six‐phase permanent magnet synchronous motor under two‐phase open circuit

A position sensor is usually required in the existing fault-tolerant direct torque control (FT-DTC) system for the multiphase permanent magnet synchronous motor (PMSM). Thus, the volume, weight, and cost of the system is increased, and the reliability is decreased. The conventional high-performance position sensorless strategies for the multiphase motor under fault-free condition cannot be directly applied to FT-DTC system. To improve this situation, a high-speed position sensorless FT-DTC strategy for a six-phase symmetrical winding PMSM with two opened phases is proposed in this study. Firstly, modified variables and a new rotating coordinate system are defined to achieve the symmetrical and decoupled mathematical model. Secondly, a stator flux observer based on the modified variables and a new coordinate system is proposed. According to the current model of modified stator flux, the estimated modified stator current can be achieved. Then, the estimated error of the modified stator current is sent to the integrator of the modified stator flux observer to correct the voltage model. Finally, the proposed stator flux observer is applied in FT-DTC for six-phase PMSM with two opened phases to realize the position sensorless operation at high speed. The experimental results verify the feasibility and effectiveness of the proposed strategy.

Fault-Tolerant Control of a Five-Phase Permanent Magnet Synchronous Motor for Industry Applications

The next big change in various industry applications is associated with power dense motors, such as permanent magnet synchronous motors (PMSMs). Utilization of multiphase PMSM can offer an additional fault-tolerant capability to their applications. Combining both advantages, this paper proposes a simple yet robust current control strategy for a five-phase PMSM under normal operation and in a case of a loss of one phase. Traditional linear current controllers successfully applied to reference tracking of a healthy motor may become less efficient during postfault operation due to additional unmodeled dynamics. This paper proposes a modified angular transformation to a special rotating frame in which the postfault permanent magnet flux linkage remains unchanged and the motor model remains decoupled. Following this, a nonlinear current control scheme based on sliding mode control is proposed, which successfully treats model inaccuracies and provides good dynamic performance and tracking accuracy. Feasibility of the proposed control strategy is experimentally validated on a laboratory scale PMSM motor with a digital signal processor/field programmable gate array based drive.