Three-phase Permanent Magnet Synchronous Machine Research Articles

Evaluative assessment of a five-phase and three-phase permanent magnet synchronous machine at varied loads and fault conditions

Multiphase machines are very essential for industrial applications that require high reliability of operation. In this paper, a comparative study of three-phase and five-phase inverter fed permanent magnet synchronous motors (PMSMs) was evaluated with respect to their performance characteristics under a healthy state and during transient disturbances such as varied load and double line to ground faults. To avert inherent high oscillations in speed and torque ripples during fault condition, the machine load was significantly reduced to 1/4th of the full load and a post fault current limiting series dynamic braking resistance (SDBR) with a bypassed switch was introduced to enhance the machine fault tolerant level and improve its operational performance. Spectral analyses were carried out to determine the magnitude of harmonic distortion during these conditions. The simulation results show that the five-phase PMSM achieved a reduced oscillatory transient and a faster settling time of speed and torque under a varied load. It also exhibited good harmonic profiles as indicated in the respective % THD values when compared to the three phase PMSM which is prone to high harmonic overheat. However, when subjected to a double line to ground fault, their various %THD values in speed and torque increased with five-phase PMSM still having a reduced %THD values over the three-phase PMSM. Therefore, for a higher fault tolerant capability, greater efficiency with proven reliability, a five-phase PMSM with a fault current limiting series dynamic braking resistance is a better substitute when compared with the three-phase PMSM in industrial applications where safety and loss minimization is a top priority. All simulation processes in this paper were achieved in MATLAB 2015.

Comparative Investigation of Dual Three-Phase Permanent Magnet Synchronous Machines With Different Winding Configurations

Comparative Investigation of Dual Three-Phase Permanent Magnet Synchronous Machines With Different Winding Configurations

Harmonic Suppression Strategy for Dual Three-phase Permanent Magnet Synchronous Machines Based on a Multi-Input Multi-Output Controller

Harmonic Suppression Strategy for Dual Three-phase Permanent Magnet Synchronous Machines Based on a Multi-Input Multi-Output Controller

Dynamic Interleaving Strategy to Reduce DC-Link Ripple of Dual Three-Phase Permanent Magnet Synchronous Machine Drives by Using Discontinuous Space Vector Modulation

Dynamic Interleaving Strategy to Reduce DC-Link Ripple of Dual Three-Phase Permanent Magnet Synchronous Machine Drives by Using Discontinuous Space Vector Modulation

Current Harmonics and Unbalance Suppression of Dual Three-Phase PMSM Based on Adaptive Linear Neuron Controller

A strategy of current harmonics and unbalance suppression based on the vector space decomposition control with adaptive linear neuron (ALN) controller for the dual three-phase permanent magnet synchronous machine (DTP-PMSM) drive system is proposed in this paper. According to the conventional vector space decomposition theory, the compensation voltages from the ALN controller in the dq-frame and dqz-frame are employed to suppress the 5th and 7th current harmonics and unbalances. Compared with the VSD control using only the PI controller, the current harmonics and unbalance are sufficiently suppressed in the proposed strategy. In addition, unlike the resonant controller discretized by conventional Tustin transformation, the ALN controller has no resonant pole shift to the desired resonant frequency. Therefore, the harmonic suppression effect of the proposed strategy exhibits better performance than the VSD control with the resonant controller, especially in the high-speed region. Finally, the feasibility and effectiveness of the proposed strategy are validated by experimental results under both steady and transient states.

Analysis of Inter-Turn Short Circuit Faults in Dual Three-Phase PMSM for Electromechanical Actuator

Dual three-phase permanent magnet synchronous machine (DTPM) is an attractive choice for electromechanical actuator owing to its advantages of double redundancy, high power density and high reliability. However, the winding insulation is susceptible to the high thermal and mechanical stress, which will lead to the inter-turn short circuit faults (ITSCF) and poses threat to the safety of the machine system. Moreover, the ITSCF of DTPM is not only limited to single-phase, but also occurs between adjacent phases. Therefore, in this paper, the characteristics of single-phase and phase-to-phase ITSCFs are investigated and compared while the short-circuit contact resistance is considered. Firstly, a general mathematical model for single-phase and phase-to-phase ITSCFs are established, and the expressions of short circuit current (SCC) and output torque are derived. Then, the characteristics of flux density, back-EMF, SCC, fault phase current and output torque of the different fault models are compared by finite element analysis. It is demonstrated that when the contact resistance is not zero ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R_f</i> ≠0), the amplitude of SCC and the third harmonic content of fault phase current are inversely proportional to the contact resistance and proportional to the number of short-circuit turns. In addition, the amplitude of SCC, torque ripple and braking torque caused by a phase-to-phase ITSCF will be larger than those of the single-phase ITSCF under the same fault conditions, especially when the contact resistance is small. Finally, an experimental prototype is made and tested to validate these analyses.

Sensorless Control Design of High-Speed Electric Drives in Discrete-Time Domain for Mild-Hybrid Turboprop Aircraft Applications

High-speed Permanent Magnet Synchronous Machine (PMSM) sensorless control design is not without challenges, especially when the ratio of power electronic modulation frequency to electrical fundamental frequency (M-F ratio) is relatively low. The Model Reference Adaptive System (MRAS) is a mature sensorless control method and has been widely used in industrial drives. There, an observer is commonly used to estimate rotor speed and angle using machine voltages and currents. The estimated angle is then further implemented for voltage and current frame transformations. Thus, the MRAS sensorless control is indeed a strong-coupled, multi-variable and nonlinear system. This paper proposes a detailed MRAS sensorless control system design method in discrete-time domain for high speed drives with relatively low M-F ratio with good system stability confidence. A detailed discrete local-linearized small-signal model is developed and state-space evolution matrix of current closed-loop system has been derived. The system stability can be defined and analysed with its maximum eigenvalue and the controller design is to make sure that the maximum eigenvalue is falling within the stable region. This proposed design method has been validated on a dual three-phase PMSM by simulation and experiment results with selected stable design point.

Harmonic Current Suppression for Dual Three-Phase PMSM Based on Deadbeat Control and Disturbance Observer

Harmonic currents always exist in a dual three-phase permanent magnet synchronous machine due to the inverter nonlinearity, nonsinusoidal back-electromotive force, and external disturbances. This article proposes a deadbeat predictive harmonic current control (DPHCC) method to suppress the harmonic currents. The DPHCC method can directly calculate the harmonic control voltage based on the sampled harmonic currents and the machine model. Thus, the steady-state and transient-state performance of harmonic current control can be improved. Further, a disturbance observer is designed to avoid the influence of inaccurate machine parameters and other unmodeled disturbances. The observer is designed based on discrete-time sliding mode theory and an improved sliding mode reaching law. The stability of the observer has been analyzed, and the value range of the observer parameters has been determined theoretically. Finally, experimental results have been presented to verify the effectiveness of harmonic current suppression for the proposed control system.

Fundamental PWM Excitation Based Rotor Position Estimation for a Dual Three-Phase Permanent Magnet Synchronous Machine

Two rotor position estimation methods for a dual three-phase (DTP) permanent magnet synchronous machine (PMSM) are investigated in this article, where the rotor position is estimated by exploiting the saliency of the motor through the phase current derivative measurement during the fundamental PWM excitation of a standard six-phase two-level inverter. It is found that in a DTP PMSM, the wide speed range rotor position estimation is possible not only in the torque-producing subspace, but also in the harmonic subspace. The principle and practical implementation of the methods are explained in details. The experimental results verify the effectiveness of the proposed rotor position estimation methods.

Sensorless Control of Dual Three-Phase Permanent Magnet Synchronous Machines—A Review

This paper presents an overview of various sensorless control methods, with a focus on dual three-phase permanent magnet synchronous machines (DTP-PMSM). Owing to the important role that DTP-PMSMs play in motion-control applications in industry, most academic researchers and industry activists seek to reduce costs and size while increasing the capability and efficiency of motion applications. This has led to an increase in the number of publications about multiphase machines in recent years. The purpose of this article is to review the most important sensorless control techniques, which are divided into two main categories, namely saliency-based control method for low-speed range and model-based control method for high-speed range. Both methods are subdivided into other categories, with a focus on DTP-PMSMs. The methods are compared with each other for the purpose of selecting the most suitable control technique for implementation in applications such as ship propulsion, wind turbines, and aerospace.

Open-Phase Fault-Tolerant Control Strategy for Dual Three-Phase Permanent Magnet Synchronous Machines Without Controller Reconfiguration and Fault Detection

Due to high power-transforming capability and excellent fault-tolerant performance, dual three-phase permanent magnet synchronous machines (DT-PMSMs) are widely used in high-reliability applications. Concerning on the remedial strategy for DT-PMSMs under open-phase faults, the conventional method is to reconfigure the controller or the current references in order to obtain optimum postfault performances. Two different control schemes should be separately designed for normal and fault conditions, respectively. Meanwhile, related fault detection measures need to be adopted and the inherent fault detection delay will further result in transient performance deterioration. In order to solve these problems, this article proposes a control strategy, which can achieve natural fault-tolerant capability of DT-PMSMs without additional fault detection algorithm. With the proposed control method adopted, reconfiguration of the control structure and modification of the current command are not required. Thus, the control scheme is simplified. The transition from the healthy to the postfault operation can be improved, meanwhile, the steady-state performances in prefault and postfault situations can be guaranteed. The proposed strategy can be generally applied to single open-phase faults and multiple open-phase faults in DT-PMSMs. Experimental validations are presented on a 1 kW DT-PMSM platform to prove the effectiveness of the proposed strategy.

A Novel Decoupling Control Scheme for Non-Salient Multi-Three-Phase Synchronous Machines Based on Multi-Stator Model

As competitive alternatives to conventional three-phase synchronous machines, synchronous multi-three-phase machines (MTPMs) are gaining increasing interests in various fields such as electrified transportation and power generation. The modular configuration is preferred for multi-three-phase drives in specific applications regarding the availability of advanced three-phase power electronics techniques and the superior capability of fault tolerance. The multi-stator (MS) modelling would be an ideal solution for the control of such modular drives as it facilitates power sharing among winding sets in a straightforward way and enables simple post fault strategies compared with the well-known vector space decomposition (VSD) modelling approach. Nevertheless, the strong magnetic coupling existing in MS model has hindered its use due to the instability and the performance deterioration issue. To solve the problem, a new decoupling control scheme directly applied in MS frame is proposed in this paper. The proposed method can deal with non-salient multi-three-phase machines whose three-phase winding sets can be identical or different, under the assumption of the sinusoidal airgap flux. Furthermore, it is shown by analysis the proposed method is characterized by significant simplicity and flexibility compared with the existing decoupling methods. The effectiveness of the proposed method has been verified through experiments including a single-side operation, a power-sharing test, and a post fault tolerant operation on a non-salient dual three-phase permanent magnet synchronous machine with quasi sinusoidal air gap flux.

Three-Phase Dual-Winding Multitasked PMSM Machine Using Double Layer Concentrated Winding for HEV Application

This paper proposes a three-phase dual-winding permanent magnet synchronous machine (PMSM) providing multitasked operation for accessory drive systems in hybrid electric vehicles (HEV). The novelty of this research lies in the machine having special slots and pole combinations with specific configuration of two sets of double-layer concentrated group winding separated by the unwound tooth between the phase groups formed on the same stator to achieve both the motoring and generator operation simultaneously as well as independently. These operations are accomplished by incorporating motor and generator winding separately on the same stator of a single PMSM machine. This single machine is particularly designed to eliminate the mutual coupling between these two sets of windings such that the load variation on the generator does not affect the mechanical output power of the motor. To confirm this multitasking, the electromagnetic design of the machine has been presented, and its operating modes are analyzed. The performance is compared using finite element analysis with that of a conventional PMSM machine having a double-layer winding configuration.

A Comprehensive Review of Machine-Integrated Electric Vehicle Chargers

Electric Vehicles are becoming increasingly popular due to their environment friendly operation. As the demand for electric vehicles increases, it has become quite important to explore their charging strategies. Since charging and traction do not normally occur simultaneously and the power electronics converters for both operations have some similarities, the practice of integrating both charging and traction systems is becoming popular. These types of chargers are termed ‘Integrated Chargers’. The aim of this paper is to review the available literature on the integrated chargers and present a critical analysis of the pros and cons of different integrated charging architectures. Integrated chargers for electric vehicles with three-phase permanent magnet synchronous machines, multi-phase machines and switched reluctance machines were compared. The challenges with the published integrated chargers and the future aspect of the work were been discussed.

Zero-sequence Current Suppressing Strategy for Dual Three-phase Permanent Magnet Synchronous Machines Connected with Single Neutral Point

Dual three-phase permanent-magnet synchronous machines (DTP-PMSM) connected with a single neutral point provide a loop for zero-sequence current (ZSC). This paper proposes a novel space vector pulse width modulation (SVPWM) strategy to suppress the ZSC. Five vectors are selected as basic voltage vectors in one switching period. The fundamental and harmonic planes and the zero-sequence plane are taken into consideration to synthesis the reference voltage vector. To suppress the ZSC, a non-zero zero-sequence voltage (ZSV) is generated to compensate the third harmonic back-EMF. Rather than triangular carrier modulation, the sawtooth carrier modulation strategy is used to generate asymmetric PWM signals. The modulation range is investigated to explore the variation of modulation range caused by considering the zero-sequence plane. With the proposed method, the ZSC can be considerably reduced. The simulated and experimental results are presented to validate the effectiveness of the proposed modulation strategy.

A Novel Space Vector PWM Technique With Duty Cycle Optimization Through Zero Vectors for Dual Three-Phase PMSM

In this paper, a novel space vector pulse width modulation (SVPWM) technique with duty cycle optimization through zero vectors for dual three-phase (3-ph) permanent magnet synchronous machines (PMSMs) is proposed. Dual 3-ph PMSMs can be optimally controlled in vector space decomposition, which allows controls of the fundamental component and main low-frequency harmonics separately in two orthogonal subspaces, i.e., αβ and xy subspaces. However, the space voltage vector modulations of voltage references in two subspaces are not independent, because each voltage vector possesses its unique and fixed spatial location in two subspaces. Therefore, many SVPWM techniques intend to extend the modulation capability by designing the voltage vector selection principle, but the duty cycle saturation determines the limit of phase voltage regardless of the voltage vector selection principle. Therefore, a simple SVPWM technique with duty cycle optimization by adjusting dwell times of zero vectors is developed to offer a reasonable modulation capability with reduced switching frequency and no complex voltage vector selection principle. The linear modulation range is explained as well. Finally, the experimental results validate the performance of the proposed SVPWM technique through voltage injection and closed-loop current control.

Electromagnetic Performance Prediction for the Symmetrical Dual Three-phase Surface-mounted PMSM under Open-phase Faults Based on Accurate Subdomain Model

The paper presents an accurate analytical subdomain model for predicting the electromagnetic performance in the symmetrical dual three-phase surface-mounted permanent magnet synchronous machine (PMSM) under open-phase faulty conditions. The model derivations are extended from previous accurate subdomain models accounting for slotting effects. Compared with most conventional subdomain models for traditional three-phase machines with nonoverlapping winding arrangement, the subdomain model proposed in this paper applied for the 24-slot/4-pole dual three-phase machine with symmetrical overlapping winding arrangement. In order to investigate the postfault electromagnetic performance, the reconfigured phase currents and then current density distribution in stator slots under different open-circuit conditions are discussed. According to the developed model and postfault current density distribution, the steady-state electromagnetic performance, such as the electromagnetic torque and unbalanced magnetic force, under open-circuit faulty conditions are obtained. For validation purposes, finite element analysis (FEA) is employed to validate the analytical results. The result indicate that the postfault electromagnet performance can be accurately predicted by the proposed subdomain model, which is in good agreement with FEA results.

Current Prediction-Based Fast Diagnosis of Electrical Faults in PMSM Drives

Open-phase fault (OPF) and open-switch fault (OSF) are two common electrical faults in the permanent magnet synchronous machine (PMSM) drives. To locate the faults rapidly and relieve the fault damage, a current prediction-based diagnosis scheme is proposed for OPF and OSF in three-phase PMSM drives. The proposed diagnosis scheme consists of three steps, namely, determining fault occurrence, locating the faulty phase, and identifying the specific fault. The general current deviations between dq-axis predicted currents from the normal model and dq-axis feedback currents are used to determine the fault occurrence. The general current deviations between dq-axis feedback currents and dq-axis predicted currents from different faulty models are used to locate the faulty phase. Then, an intervention-based diagnosis is developed to identify the specific fault. In this way, the specific fault can be quickly located within several switching periods. Finally, the effectiveness of the proposed diagnosis scheme is verified by the experimental results.

Six-Step Operation of a Symmetric Dual Three-Phase PMSM With Minimal Circulating Currents for Extended Speed Range in Electric Vehicles

Automotive applications demand high efficiency, good reliability, and a wide operating speed range within limited dc bus voltage constraints. In this article, a zero degree displacement dual three-phase permanent magnet synchronous machines (PMSM) is derived from an original three-phase PMSM to enhance the power rating as well as the operating speed range. The proposed topology can be used as an alternative to the conventional configuration of three-phase PMSM with a bidirectional dc–dc converter for electric vehicles. Even though the commonly used dual three-phase PMSM with split-phase winding eliminates the sixth harmonic torque pulsation, a large circulating current is generated during six-step operation, which results in additional stator copper loss. In this article, six-step operation of the symmetric dual three-phase PMSM with zero degree winding displacement is proposed to achieve maximum inverter utilization. Both harmonic circulating current and torque pulsation were observed to be within satisfactory levels using this configuration. A changeover algorithm is also proposed to enable a smooth transition between closed-loop current vector control during low and medium speed operation to open-loop six-step voltage angle control for high speed operation. The performance of the proposed method is experimentally validated on a 3-kW dual three-phase PMSM drive.

A Novel High Torque Density Dual Three-Phase PMSM With Low Space Harmonic Content

A novel 36-slot/14-pole dual three-phase permanent magnet synchronous machine (PMSM) is proposed to suppress non-working space harmonics in the synthesized magnetomotive force (MMF) and improve torque density simultaneously. The machine adopts unequal coil-turns winding and special stator core which includes two different types of slots, namely double-layer slots (DLSs) and single-layer slots (SLSs). The special structure of the machine improves the working space harmonic and eliminates lower non-working space harmonics in MMF, which leads to torque promotion and permanent magnet (PM) loss reduction. Harmonic content in MMF of the proposed machine is derived from theoretical analysis and verified by finite element (FE) calculation. Besides, the proposed machine is compared with existing machines, from aspects of MMF, back electromotive force (EMF), torque, losses, efficiency, unbalanced magnetic force (UMF), and torque-speed characteristic. The proposed machine has higher torque density, higher efficiency, and lower PM loss than existing machines.