Surface Permanent Magnet Synchronous Motor Research Articles

진화론적 알고리즘을 이용한 코깅토크가 적은 풍력발전기의 설계

근래에는 신재생에너지를 이용한 독립적인 발전기의 수요가 증가하고 있는 추세이며 그 중에서 소형 풍력발전기의 개발 또한 활발하게 이루어지고 있다. 이러한 소형 풍력발전기는 목적에 따라 단순화 및 소형화가 가능하도록 영구자석이 주로 쓰인다. 하지만 영구자석 동기기는 구조적인 원인으로 인하여 코깅토크를 수반하고 이는 소음과 진동의 원인이 된다. 코깅토크는 영구자석이나 코어의 형상에 의해 변하며 적절한 설계기법으로 코깅토크를 저감시킬 수 있다. 본 논문에서는 영구자석의 형상변화를 통해 소형 풍력발전기에 많이 사용되는 표면부착형 영구자석 동기전동기의 코깅토크를 저감시키는 설계기법을 제시하였다. 코깅토크를 줄일 수 있는 영구자석의 형상을 구하는 데에는 확률론적 최적화기법의 일종인 진화론적 최적화기법을 사용했다. 최적화 기법을 적용할 때에 설계변수로는 영구자석의 폭을 조절하는 각도와, 영구자석의 외경을 조절하는 반지름을 설정하였다. 제시된 설계기법을 사용해서 극/슬롯의 조합이 8극/18슬롯이고 출력이 300W급인 풍력발전기를 설계하고 코깅토크와 출력전압 등의 특성을 계산했다. 계산결과에 의하면 초기모델에 비해 최적화모델에서 코깅토크와 토크리플 모두가 감소해서, 본 연구에서 제시한 설계기법이 코깅토크를 줄이는 데에 효과가 있음을 확인하였다. The demand for independent generators using renewable energy has been increasing. Among those independent generators, small wind turbine generators have been actively developed. Permanent magnets are generally used for small wind turbine generators to realize a simple structure and small volume. On the other hand, cogging torque is included due to the structure of the permanent magnet synchronous machine, which can be the source of noise and vibration. The cogging torque can be varied by the shape of the permanent magnet and core, and it can be reduced using the appropriate design techniques. This paper proposes a design technique that can reduce the cogging torque by changing the shape of the permanent magnets for SPMSM (Surface Permanent Magnet Synchronous Motor), which is used widely for small wind turbine generators. Evolution Strategy, which is one of non-deterministic optimization techniques, was adopted to find the optimal shape of the permanent magnets that can reduce the cogging torque. The angle and outer diameter of permanent magnet were set as the design variable. A 300W class wind turbine generator, whose pole/slot combination was 8 poles/18 slots, was designed with the proposed design technique. The properties of the generator, including the cogging torque and output voltage, were calculated. The calculation results showed that the cogging torque of the optimized model was reduced compared to that of the initial model. The design technique proposed by this paper can be an effective measure to reduce the cogging torque.

Low Space Order Analysis of Radial Pressure in SPMSM With Analytical and Convolution Approaches

This paper presents an analysis of low space order of the air-gap radial Maxwell pressures in surface permanent magnet synchronous machines with fractional slot concentrated windings. The air-gap Maxwell pressures result from the multiplication of the flux density harmonics due to magnetomotive forces and permeance linked to the magnet, the armature, and the stator slots and their interactions. One low space order is selected, and different approaches are compared to determine the origin of this pressure. First, an analytical prediction tool analytical calculation of harmonic force orders (ACHFO) is used to calculate the space and time orders of these magnetic pressure harmonics while identifying their origin in terms of interactions between magnet, armature, and teeth effects. In addition, the analytical prediction of ACHFO is compared with the flux density convolution and finite-element approaches. The main advantage of our tool is the speed of computation. Finally, an experimental operational deflection shape measurement is performed to show the deflection shape of the low space order selected.

Sensitivity Analysis of High-Frequency Signal Injection-Based Temperature Estimation Methods to Machine Assembling Tolerances

The injection of a high-frequency signal in the stator via inverter has been proven to be a viable option to estimate the magnet temperature in permanent magnet synchronous machines (PMSMs). Injection of a pulsating d -axis current is especially appealing, as it is insensitive to the speed, and $L_{d}$ and $L_{q}$ inductance variations. Furthermore, it is suitable both for interior PMSMs and surface PMSMs. Regardless of its promising characteristics, there are a number of issues that can reduce its accuracy, including machine assembling tolerances and rotor lamination grain orientation, which might need to be considered. This paper analyzes the sensitivity of temperature estimation using pulsating d -axis high-frequency current injection to rotor eccentricities, permanent magnet assembling tolerances, and lamination grain orientation. Preliminary results indicate that these issues can have a nonnegligible impact on the accuracy of the method.

Performance Comparison Study of Space-Vector and Modified-Carrier-Based PWM Techniques for a Three-Level Neutral-Point-Clamped Traction Inverter Drive

A performance comparison study between lower switching loss-based space-vector pulsewidth modulation (PWM) strategy for a three-level neutral-point-clamped inverter and a proposed modified-carrier-based PWM strategy is carried out for an electric vehicle propulsion application. The proposed carrier-based strategy uses single carrier and reduces the switching losses compared with the conventional carrier-based strategies by eliminating the common modulation interval between the upper and lower modulating signals. The inverter switching and conduction losses, total inverter loss, and voltage and current harmonic distortions are also compared with both the control strategies. PLECS is used to simulate the inverter losses with a 54-kW surface permanent magnet synchronous machine (SPMSM). Detailed simulation and experimental performances with the proposed carrier-based strategy and the dc-link voltage balancing during the change in speed and torque variations are carried out on a scaled-down prototype of 6-kW SPMSM. Dspace is used for hardware verification. Results show that, with the proposed carrier-based strategy, the dc-link capacitors are balanced even during the change in speed and torque.

Erratum: Correction of Figure. Analysis and Experimental Characterization of Low Speed Direct Drive Fractional Slot Concentrated Winding Surface Permanent Magnet Synchronous Motor with Consequent Pole Rotor

Erratum: Correction of Figure. Analysis and Experimental Characterization of Low Speed Direct Drive Fractional Slot Concentrated Winding Surface Permanent Magnet Synchronous Motor with Consequent Pole Rotor

DC-Bus Voltage Balancing Algorithm for Three-Level Neutral-Point-Clamped (NPC) Traction Inverter Drive With Modified Virtual Space Vector

A modified-virtual-space-vector-based dc-link voltage balancing strategy is proposed in this paper for a three-level inverter. In the proposed strategy, the summation of the three-phase currents for virtual vector needs not to be zero and it also keeps the two capacitor voltages balanced with wider range of load variations. The duty cycles for all the power switches are also derived in this paper using a nearest three-voltage vector scheme. Due to the reduced use of the medium voltage vectors, the proposed control strategy can considerably decrease the neutral-point voltage fluctuation for lower power-factor-based loads as well. Detailed simulation and experimental studies are also carried out to show the effectiveness of the proposed system with a dc-link voltage balancing strategy with permanent magnet synchronous machine. Voltage and current harmonic distortions are also presented with change in modulation index. A Dspace-based real-time operating system is used for real-time implementation with a 6.0-kW surface permanent magnet synchronous motor.

Performance Analysis and Comparison of Surface and Interior Bearingless Permanent Magnet Synchronous Motors

Performance Analysis and Comparison of Surface and Interior Bearingless Permanent Magnet Synchronous Motors

Initial position estimation strategy for a surface permanent magnet synchronous motor used in hybrid electric vehicles

A novel nonlinear model for surface permanent magnet synchronous motors (SPMSMs) is adopted to estimate the initial rotor position for hybrid electric vehicles (HEVs). Usually, the accuracy of initial rotor position estimation for SPMSMs relies on magnetic saturation. To verify the saturation effect, the transient finite element analysis (FEA) model is presented first. Hybrid injection of a static voltage vector (SVV) superimposed with a high-frequency rotating voltage is proposed. The magnetic polarity is roughly identified with the aid of the saturation evaluation function, based on which an estimation of the position is performed. During this procedure, a special demodulation is suggested to extract signals of iron core saturation and rotor position. A Simulink/MATLAB platform for SPMSMs at standstill is constituted, and the effectiveness of the proposed strategy is verified. The proposed method is also validated by experimental results of an SPMSM drive.

Discontinuous Hybrid-PWM-Based DC-Link Voltage Balancing Algorithm for a Three-Level Neutral-Point-Clamped (NPC) Traction Inverter Drive

This paper presents a hybrid pulse width modulation-based discontinuous modulation (D-HPWM) strategy with dc-link voltage balancing for a three-level neutral-point-clamped (NPC) traction inverter drive. The results are then compared with continuous-hybrid-PWM (C-HPWM) to check the performance improvement. The HPWM strategy uses both the advantages of carrier- and space-vector-based PWM strategies. The duty cycles are generated using the carrier-based strategy to reduce the computational time and complexity of the system and redundant vector states are used to keep the two dc-link capacitor voltages balanced. As discontinuous PWM (DPWM) reduces the switching losses considerably compared to the continuous PWM, the DPWM strategy is developed in this paper for the HPWM-based strategy. Detailed comparison studies are then carried out in MATLAB/Simulink and PLECS to show the conduction and switching loss distribution with change in modulation index for different power switches. A 54.0-kW surface permanent magnet synchronous machine (PMSM) is used for this simulation studies. Moreover, the total inverter loss and losses in each insulated gate bipolar transistor (IGBT) are also compared. Detailed experimental performance analysis is also carried out with a scaled down prototype of a 6.0-kW surface PMSM, NPC inverter, and real-time emulator DSpace, to show the capacitor voltage deviation with both control strategies.

Bias compensation based partially coupled recursive least squares identification algorithm with forgetting factors for MIMO systems: Application to PMSMs

Aiming at a class of systems with multiple-input multiple-output (MIMO) output-error, this paper proposes a novel bias compensation based partially coupled recursive least squares (RLS) algorithm with forgetting factors, based on the coupled identification concept and the bias compensation technique. The proposed algorithm can not only give the unbiased estimates of the system parameters in the presence of colored noises, but also improve the tracking capability of the time-varying parameters. Additionally, complex matrix inversion is avoided in the proposed algorithm, which is required in the multivariable RLS algorithm to identify MIMO systems. The analysis indicates that the proposed algorithm requires less computational burden than the traditional multivariable RLS algorithm. Finally, the proposed algorithm is tested on a surface permanent-magnet synchronous motor example, the efficiency of which is demonstrated by the experimental results.

Design Methodology for High-Speed Permanent Magnet Synchronous Machines

In this paper, a design methodology for surface permanent magnet (PM) synchronous machines, with special application to the case of high-speed machines, will be presented. Following a discussion of the principle and assumptions inherent in the methodology, the analytical model used in the study will be presented. This model will then be implemented to solve the problem of maximizing the power-to-volume ratio from an analytical perspective. It will be shown how this formulation serves to establish design rules, in addition to setting criteria values for the selection of magnetic materials (i.e., silicon steel sheet versus a soft magnetic material). At last, the paper will present a data test bench made of two PM machines designed since the methodology presented herein.

Current Injection-Based Online Parameter and VSI Nonlinearity Estimation for PMSM Drives Using Current and Voltage DC Components

To develop a high-performance and reliable permanent-magnet synchronous machine (PMSM) drive for electric vehicle (EV) applications, accurate knowledge of the PMSM parameters is of significance. This paper investigates online estimation of PMSM parameters and voltage source inverter (VSI) nonlinearity using current injection method in which magnetic saturation is also considered. First, a novel dc component-based current injection model considering VSI nonlinearity is proposed, which employs the dc components of dq -axis currents and voltages for PMSM parameter and VSI-distorted voltage estimation. This method can eliminate the influence of rotor position error on VSI nonlinearity estimation. Second, a simplified linear equation is employed to model the cross- and self-saturation of the dq -axis inductances during current injection, which can facilitate the estimation of the inductance variations induced by magnetic saturation. Third, a novel current compensation strategy is proposed to minimize the torque ripples caused by current injection, which contributes to making our approach applicable to both surface and interior PMSMs. Therefore, the proposed online parameter estimation approach can estimate the winding resistance, rotor flux, VSI-distorted voltage, and the varying dq -axis inductances under different operating conditions. The proposed approach is experimentally validated on a down-scaled laboratory interior PMSM prototyped for direct-drive EV powertrain.

A Novel Methodology for the Demagnetization Analysis of Surface Permanent Magnet Synchronous Motors

A surface permanent magnet synchronous motor (SPMSM) using ferrite magnet represents small air gaps and high stack lengths relatively. Thus, it has small edge effects on the performance of the motor, and a 2-D finite-element analysis (FEA) method is largely used to design it. In the case of the demagnetization analysis in the SPMSM, however, it is difficult to neglect fringing effects in air gaps, because the permeability of the permanent magnet is the same as air and the direction of the armature reaction is opposite to the magnetization direction. Therefore, the accuracy of the 2-D FEA is significantly degraded. In this paper, the edge effect of SPMSM on the demagnetization analysis is analyzed. For achieving it, the opposing magnetic field that contributes to the demagnetization is analyzed by two different elements, such as permanent magnet and armature reaction. In addition, a simplification model of the ${ {yz}}$ plane that can consider the edge effect is proposed to increase the accuracy of the conventional 2-D FEA, which is analyzed on the ${ {xy}}$ plane, and correction factors are also induced. Finally, its validity is verified by applying the proposed method to the conventional motors.

Dynamic and steady state performance comparison of line-start permanent magnet synchronous motors with interior and surface rotor magnets

Abstract A comprehensive comparison of the dynamic and steady state performance characteristics of permanent magnet synchronous motors (PMSM) with interior and surface rotor magnets for line-start operation is presented. The dynamic model equations of the PMSM, with damper windings, are utilized for dynamic studies. Two typical loading scenarios are examined: step and ramp loading. The interior permanent magnet synchronous motor (IPMSM) showed superior asynchronous performance under no load, attaining faster synchronism compared to the surface permanent magnet synchronous motor (SPMSM). With step load of 10 Nm at 2 s the combined effect of the excitation and the reluctance torque forced the IPMSM to pull into synchronism faster than the SPMSM which lacks saliency. The ability of the motors to withstand gradual load increase, in the synchronous mode, was examined using ramp loading starting from zero at 2 s. SPMSM lost synchronism at 12 s under 11 Nm load while the IPMSM sustained synchronism until 41 seconds under 40 Nm load. This clearly suggests that the IPMSM has superior load-withstand capability. The superiority is further buttressed with the steady state torque analysis where airgap torque in IPMSM is enhanced by the reluctance torque within 90° to 180° torque angle.

Adaptive Compensation Method for High-Speed Surface PMSM Sensorless Drives of EMF-Based Position Estimation Error

To improve the performance of the surface permanent magnet synchronous motor drives, a sensorless control scheme based on the sliding-mode observer with an orthogonal phase-locked loop (PLL) incorporating two synchronous frequency-extract filters (SFFs) is proposed. The rotor position estimation errors are analyzed. The analysis results show that the harmonic errors of the estimated signal are hard to eliminate completely. Therefore, an improved adaptive notch filter - The SFF is proposed to extract the fundamental wave of the rotor position estimation before applying to the PLL. This method of the PLL combined SFFs can compensate the estimated back electromotive force harmonic error efficiently and adaptively. An experimental driveline system used for testing the electrical performance of the developed magnetically suspended motor is built. The effectiveness and the feasibility of the proposed method are validated with the experimental results.

Performance Comparison of Line-Start Permanent Magnet Synchronous Motors with Interior and Surface Rotor Magnets

Objectives: The aim is to undertake a comprehensive comparison of the dynamic and steady state performance of Permanent Magnet Synchronous Motors (PMSM) with interior and surface rotor magnets for line-start operation. Methods/Analysis: The dynamic model equations of the PMSM, with damper windings, are utilized for dynamic studies. Two typical loading scenarios are examined: Step and ramp loading. Emphasis was on the synchronization and load-withstand capabilities of the two motor classes. Also, the steady state torque performance was compared using the torque/torque angle relationship. Findings: The interior permanent magnet synchronous motor (IPMSM) showed superior asynchronous performance under no load, attaining faster synchronism compared to the Surface Permanent Magnet Synchronous Motor (SPMSM). With step load of 10Nm at 2 seconds the combined effect of the excitation and the reluctance torque forced the IPMSM to pull into synchronism faster than the SPMSM which lacks saliency. The ability of the motors to withstand gradual load increase, in the synchronous mode, was examined using ramp loading starting from zero at 2seconds. SPMSM lost synchronism at 12seconds under 11Nm load while the IPMSM sustained synchronism until 41seconds under 40Nm load. This clearly suggests that the IPMSM has superior load-withstand capability. The superiority is further buttressed with the steady state torque analysis where airgap torque in IPMSM is enhanced by the reluctance torque within 90o to 180o torque angle. Applications: The findings of this research will serve as guide in taking logical decisions in the design and operation of permanent magnet synchronous motors to achieve desired objectives in specific applications.

Development of a 20-Pole–24-Slot SPMSM With Consequent Pole Rotor for In-Wheel Direct Drive

In-wheel motors bring a fundamental change in electric vehicle technology by removing conventional mechanical components and freeing up space inside the vehicle body. This approach ultimately helps to realize all-wheel independent control for improved vehicle dynamics and increased vehicle design freedom. However, when space allowed for an in-wheel motor is taken into consideration, high torque density, high efficiency, and wide-speed-range capability are typically required. This paper specifically investigates a 20-pole–24-slot surface permanent magnet synchronous motor with consequent pole rotor for in-wheel direct drive since this topology is well suited for high-pole motors and thus high-torque direct-drive applications. Extensive finite-element analysis is carried out to characterize the proposed motor, and the practical feasibility of the proposed motor is discussed. Finally, the validity of the analysis was experimentally verified.

Modified DC-Bus Voltage Balancing Algorithm for a Three-Level Neutral-Point-Clamped PMSM Inverter Drive With Reduced Common-Mode Voltage

This paper presents an improved dc-link voltage balancing algorithm for a three-level neutral-point-clamped inverter by considering phase current direction. Detailed studies on the effects of change in load current direction on the dc-link capacitor voltages are presented. A maximum value of power factor is numerically derived, above which it affects the capacitor voltage balancing capability. Compared with the previously presented research work, the inputs to the space-vector pulsewidth-modulation block are the three phase currents and the difference between the two capacitor voltages. Depending on the states of the two dc-link capacitor voltages and phase current direction, redundant voltage vector sequences are selected. The selected vectors keep the capacitor voltage deviations within 5% of the total dc-link voltage. Two zero switching vectors (i.e., PPP and NNN) are also removed from all subsectors of the earlier proposed strategy, which one used to produce higher common-mode voltages. Detailed simulation and experimental results are presented in this paper for a 6.0-kW surface permanent-magnet synchronous machine. Both the simulation and experimental results show the required performance of the proposed system.

Analysis and Experimental Characterization of Low Speed Direct Drive Fractional Slot Concentrated Winding Surface Permanent Magnet Synchronous Motor with Consequent Pole Rotor

This paper describes analysis and experimental characterization of low speed direct drive fractional slot concentrated winding (FSCW) surface permanent magnet synchronous motor (SPMSM) with consequent pole (CP) rotor, for which studies have been recently performed. The proposed motor, which consists of 30 poles and 36 slots, is analyzed and characterized by extensive 2D finite element analysis (FEA) and together with 3D FEA for an appropriate PM overhang length design. The validity of the analysis is confirmed by the corresponding experiments which fully characterize the proposed motor with excellent agreement between the FEA and the experiments. Thermal stability is also experimentally examined to determine continuous operating points and instantaneous operating points of the proposed motor. It is highly expected that the proposed motor is applicable for low speed direct drive applications.

Permanent-Magnet Temperature Estimation in PMSMs Using Pulsating High-Frequency Current Injection

The injection of a high-frequency signal in the stator via inverter has been shown to be a viable option to estimate the magnet temperature in permanent-magnet synchronous machines (PMSMs). The variation of the magnet resistance with temperature is reflected in the stator high-frequency resistance, which can be measured from the resulting current when a high-frequency voltage is injected. However, this method is sensitive to d- and q-axis inductance (L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> and L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</sub> ) variations, as well as to the machine speed. In addition, it is only suitable for surface PMSMs (SPMSMs) and inadequate for interior PMSMs (IPMSMs). In this paper, the use of a pulsating high-frequency current injection in the d-axis of the machine for temperature estimation purposes is proposed. The proposed method will be shown to be insensitive to the speed, L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</sub> , and L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> variations. Furthermore, it can be used with both SPMSMs and IPMSMs.