Surface-mounted Permanent Magnet Synchronous Motor Research Articles

An Enhanced Deadbeat Predictive Current Control of SPMSM With Linear Disturbance Observer

Deadbeat predictive current control (DPCC) with a linear disturbance observer (LDO) in the surface-mounted permanent magnet synchronous machine (SPMSM) has been widely applied in many applications due to better dynamic response performance and easy implementation. However, the evaluated lumped disturbances caused by current measurement noises, inverter nonlinearity, abrupt reference current, and initial inductance parameter mismatch can restrain the high-performance development. In order to handle this issue, an enhanced DPCC with LDO is proposed in this article, where a modified DPCC with the LDO model and the noninvasive inductance and inverter disturbance observer are developed. In this case, the initial inductance parameter mismatch and high-frequency disturbances effect on the DPCC with LDO is reduced, while the current measurement noises’ suppression is enhanced by the proposed LDO. The theoretical analysis has shown that the proposed DPCC with LDO has a better performance than the conventional DPCC with LDO. Also, the superiority of the proposed DPCC with LDO has been validated by an SPMSM drive test rig.

Computationally Efficient Deadbeat Direct Torque Control Considering Speed Dynamics for a Surface-Mounted PMSM Drive

In this article, a computationally efficient deadbeat (DB) direct torque and flux control is investigated for surface-mounted permanent magnet synchronous motor (SPMSM) drives. Unlike conventional DB direct torque control (DB-DTC), the proposed DB-DTC technique simultaneously manipulates the electromagnetic torque and stator flux along with rotor speed in a combined DB controller structure. Moreover, a simple and computationally efficient DB-DTC structure is achieved through a novel DB controller design in the stationary reference frame and it ensures an improved transient performance within finite time steps. The feedforward terms are properly designed to mitigate the effects of system uncertainties. The stability of the proposed DB-DTC has been proven and discussed in detail through Lyapunov theory and eigenvalue analysis. The designed DB-DTC strategy has been simulated via MATLAB/Simulink software and practically evaluated on a laboratory SPMSM drive with TI digital signal processor TMS320F28335. Extensive comparative evaluation with conventional proportional-integral (PI)-DTC and DB-DTC corroborate an improved control performance in speed/torque dynamic response (fast rise time) as well as reductions in torque and flux ripples under tough practical conditions (e.g., speed and torque step-changes, and speed reversal test cases) with significantly reduced computational complexity.

An Algorithm for Estimation of Stator Resistance and Inductance of Low-Cost SMPMSM Drives

The information on stator resistance and inductance is extremely important for advanced electrical drives, which are used for tuning of position estimators, current controllers, temperature monitoring, and so on. The properly tuned control systems can provide fast response, have higher stability, and increase the efficiency of motor drives; as a result, it is of great importance at the development and tuning stages. This article proposes a simple estimation technique for surface-mounted permanent magnet synchronous motors (SMPMSMs), capable of measuring stator resistance and inductance. In order to measure the stator resistance, the developed algorithm injects two-leveled dc currents that provide information for resistance calculation. At the next stage, the estimation algorithm initiates exponential current transient, measures electric time constant of the motor, and calculates inductance. In contradiction to the conventional approach, this work composes a more detailed model of the motor and takes inverter voltage drop into account. Furthermore, this article studies several exponential transients, compares them to each other, and provides recommendations for use of each approach. Then, the proposed ideas are verified using several motors of different powers and parameters. Finally, the recommendations on application of each approach and parameter selection are provided.

Novel Multi-Physics Computational Simulation of a 10 kW Permanent Magnet Motor for Podded Propulsion

This paper presents a 10 kW, 12-slot 10-pole surface-mounted permanent magnet synchronous motor (SPMSM) design with fractional-slot concentrated winding for a podded propulsion system. Its load is a propeller that is proportional to the square of the rotational speed and the fifth power of the propeller diameter. Taking this into account, three SPMSMs with rated rotational speeds of 600, 1200, and 1800 rpm with the same rated output power of 10 kW were analyzed. These were designed under the same conditions (i.e., torque per rotor volume, air-gap length, current density, power factor, fill-factor, and supply voltage). Based on the SPMSMs designed by electromagnetic analysis, the housing of a podded propulsor for each SPMSM was modeled for mechanical analysis, including such parameters as forced vibration, radiated noise, and modal acoustics analysis in air and water. From the modal acoustics analysis, it is confirmed that the natural frequencies of a structure in water are lower than those in air because of the added mass effect of water.

Dual-Time-Scale Sliding Mode Control for Surface-Mounted Permanent Magnet Synchronous Motors

The permanent magnet synchronous motors (PMSMs) as the completely symmetrical three-phase machines, which are usually driven by symmetrical voltage signals. Unfortunately, a PMSM system usually suffers from the different lumped disturbances, such as internal parametric perturbations and external load torques, the speed regulation problem should be addressed within the different operation situations. Characterizing by the current variation speed of the motor winding is much faster than that of the mechanical dynamic velocity, a dual-time-scale sliding mode control (SMC) method for the surface-mounted PMSMs is proposed in this paper. Firstly, the mathematical model of PMSMs is established in the two-phase synchronous rotating orthogonal reference coordinate system, and the slow and fast variation subsystems are obtained based on the quasi-steady-state theory. Secondly, a tracking differentiator (TD)-based and exponential reaching law-based sliding mode controllers are individually designed within dual-time-scale, respectively. As a result, the eventual SMC strategy is presented, and the stability of control system is analyzed by applying the Lyapunov stability theory. The main contribution of this study is to present an alternative control framework for the PMSMs servo system, where the dual-time-scale characteristic is involved, and thus a non-cascade control structure that different from the traditional drive strategy is proposed in the motor community. Finally, the model of whole system is built and carried out on the simulation platform. Research results demonstrate that the presented servo control system can accurately track the reference angle velocity signal, while the strong robustness and fast response performance are guaranteed in the presence of external disturbances. In addition, the three-phase current transient response values are completely symmetrical with the rapid adjustment characteristic.

A Novel SPMSM Sensorless Drive Using Discrete-Time Synchronous-Frequency Adaptive Observer Under Low Frequency Ratio

To improve the stability and accuracy of the estimated position using the conventional sliding mode observer (CSMO) under low frequency ratio (LFR), this article proposes a novel discrete-time synchronous-frequency adaptive observer (SFAO) for surface-mounted permanent magnet synchronous motor (SPMSM) sensorless drives. The proposed SFAO has merits of high amplitude and zero-phase lag of resonant controller at synchronous frequency. The sign function and the low-pass filter (LPF) of CSMO in the proposed observer can be removed and conducive to dispel the inherent chattering of the CSMO as well as phase shift produced by the LPF. Then, taking into account the digital control delay and discretization truncation error, an exact complex-vector discrete-time model in the stationary coordinate is developed. Based on that, the direct discrete-time domain design approach is utilized in the proposed observer, which can be devised by pole placement directly on complex <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</i> -domain to assure the stability and position estimation accuracy under LFR. Finally, the availability of the proposed discrete-time SFAO scheme is verified via experiments on a 2.1-kW SPMSM drive.

Continuous Control Set Predictive Speed Control of SPMSM Drives With Short Prediction Horizon

This article proposes a continuous control set predictive speed control (CCS-PSC) strategy for surface-mounted permanent magnet synchronous motor (SPMSM) drives, where the prediction horizon is short and the computational complexity is low. The optimization problem of the proposed CCS-PSC is formulated and analyzed. The current and voltage constraints are transformed into incremental voltage constraints, which can be updated in real-time. A reduced-order incremental model of SPMSM is adopted for the prediction, where integrators are naturally embedded. Hildreth’s quadratic programming algorithm is used to solve the optimization problem, where the active constraints are identified and the reference voltage is calculated. The performance of the proposed strategy is validated through comparative experiments with finite control set predictive speed control (FCS-PSC), cascaded CCS-PSC and field-oriented control. The results demonstrate the superb dynamic performance of the proposed CCS-PSC strategy, while the phase current total harmonic distortion is relatively low.

A Super-Twisting-Like Fractional Controller for SPMSM Drive System

A new super-twisting-like fractional (STLF) controller is proposed in this article to improve the control performance for surface-mounted permanent magnet synchronous motor (SPMSM) system. Compared with the conventional super-twisting sliding mode (STSM) algorithm, the most distinctive characteristic of the proposed strategy is to replace the discontinuous switching function hidden under the integration with a nonsmooth term, which can significantly optimize the performance of SPMSM system. Meanwhile, the introduction of nonsmooth term can provide stronger anti-disturbance capability than the widely used smooth controller. In addition, the desired control performance can be achieved by adjusting the parameters of the proposed STLF controller according to the specific situations. Comparative experiments among the proposed STLF, conventional STSM and proportional integral controllers are carried out to demonstrate the feasibility and effectiveness of the proposed STLF technique.

On Continuous-Set Model Predictive Control of Permanent Magnet Synchronous Machines

This article presents a real-time realization of a continuous-control-set model predictive current controller for the two types of permanent magnet synchronous machines: 1) surface-mounted permanent magnet synchronous machine (SMPMSM) and 2) interior permanent magnet synchronous machine (IPMSM). The constrained optimization problem is solved online using a slack formulation of the primal-dual interior-point method. The proposed controller is tested on a 14.5 kW SMPMSM based on the linear time-invariant (LTI) model of the machine and on a 0.5 kW IPMSM. For the latter, we present in detail how the nonlinear first-principles modeling yields the fastest possible transient as well as an offset-free steady-state performance. The experimental results were obtained at sampling times typically used in the electrical drive applications (125 and 100 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> s for the two machines, respectively).

Application of Surrogate Models to the Multiphysics Sizing of Permanent Magnet Synchronous Motors

The application of surrogate models in engineering design is becoming popular due to their mimicking capabilities. In the design of electric motor drives for example, where a control-drive circuit is connected directly to the electric motor, the finite element simulations of the integrated motor drive system can be time-consuming. A complete motor simulation can run into several hours, if not days. Therefore, the main contribution of this article resides in the effort to address the computational burden associated with the design process by replacing the finite element models with surrogate models to achieve a faster design process. Briefly, the procedure involves filling the design space with multiple motor geometries created from an 8-pole 12-slot surface-mounted permanent magnet (SPM) synchronous motor. Then, a multiphysics performance evaluation is performed over the design space for different switching frequencies over a range of dc bus voltages. The design variables of the motor, the inverter, and the calculated performance objectives are used to train a collection of surrogate models to obtain the objective functions that could potentially be used as possible replacements for the finite element models in order to reduce the solution time.

Multi-objective Predictive Control of 3L-NPC Inverter Fed Sensorless PMSM Drives for Electrical Car Applications

This paper proposes a multi-objective FS-MPC approach based on three-step optimization for a surface-mounted PMSM fed by a 3L-NPC inverter. It helps to significantly reduce torque ripples, current harmonics while controlling the inverter's neutral point voltage. To overcome the drawbacks of using mechanical sensors, a sliding mode observer is used to estimate the machine speed and rotor angular position. Compared to existing works, the proposed control method is implemented using the proportionality between the electromagnetic torque and the current component on the q-axis to eliminate the computational redundancy related to the current and torque control. To further reduce torque ripples and current harmonics, a 3L-NPC inverter is used. Compared to other types of three-level inverters, it uses less power semiconductors and attenuates the problem of voltage fluctuation at the neutral point and current harmonics. Matlab/Simulink simulations of the proposed approach yield a current THD of 1.69 %.

Mitigation of high-resistance connection in surface-mounted PMSM drive system based on model predictive current control

High-resistance connection fault can result in the increasing of power loss and the rise of heat, so the electric machine drive system possibly can be damaged. Therefore, to reduce the copper loss caused by high-resistance connection in surface mounted permanent magnet synchronous machine drive system, a method to minimize the copper loss based on the model predictive current control is shown in this paper. First, the permanent magnet synchronous machine model is deduced under high-resistance connection fault condition. Then, the direct axis current is deduced to minimize the copper loss. Next, the predictive model of permanent magnet synchronous machine is deduced under fault condition, and the cost function is defined to select the optimal voltage vector. Finally, the proposed model predictive current control strategy is realized to minimize the copper loss. And the effectiveness of this method is verified through the simulation and experiment. According to the results of the simulation and experiment, the proposed model predictive current control method has the same performance as the traditional model predictive current control method, as well as can reduce the copper loss effectively.

A composite sliding-mode observer with PLL structure for a sensorless SPMSM system

To achieve high-precision speed and position control for the surface-mounted permanent magnet synchronous motor (SPMSM), this paper proposes a sensorless vector control strategy based on a composite sliding-mode observer (SMO) and an improved phase-locked loop (PLL) structure. Different from the existing sensorless methods, the proposed control strategy can further improve the accuracy of observation position and speed. First, a new sliding-mode function and the equivalent control are introduced to weaken the chattering and accelerate the reaching rate. Then, a sliding-mode current observer based on an adaptive law control is designed to observe the back electromotive force (back EMF). Meanwhile, the adaptive law can ensure the stability of the system in different states and reduce the system chattering. Second, an adaptive back EMF observer is presented to accurately observe the estimated back EMF. Furthermore, the stability of the two observers is proved by employing the Lyapunov second method. Next, the variable gain PLL with the signal suppressor is used to obtain an accurate rotor position and speed. Finally, the simulations and experiments are implemented to validate the performance of the proposed control strategy, in terms of speed and position tracking as well as anti-disturbance ability.

Magnetic Field Prediction of the Saturated Surface-Mounted Permanent Magnet Synchronous Machine With Rotor Eccentricity

This article presents an analytical method to predict the magnetic field of eccentric surface-mounted permanent magnet synchronous machine (SPMSM) by applying the hybrid magnetic circuit and subdomain method. Taking stator saturation into account, the surface current is appended to the stator coil conductor, which can generate a magnetomotive force (MMF) to compensate the MMF drop across the stator core. The rotor yoke saturation effect is modeled by increasing the air-gap length. To solve the problem resulted from rotor eccentricity in analytical analysis, an equivalent transformation method is given. The transformation principle is that the eccentric machine can be equivalent to a concentric one with redistributed PM remanence and armature current density. On this basis, the subdomain method is adopted to predict the magnetic field of the reestablished machine. The proposed analytical method is implemented and evaluated on the 6p/36s and 8p/12s SPMSM and exhibits good agreement with the FEM and experiment results.

Novel Method of Deriving Torque and Speed Curve of the Permanent Magnet Synchronous Motor Using Initial State Finite Element Analysis

This article proposes the novel method of deriving torque and speed curve (TS curve) of the permanent magnet synchronous motor (PMSM) using the initial state finite element analysis (ISF) for the purpose of reducing the high calculation cost of the repetitive finite element analysis (FEA). The ISF is a method that conducts the FEA only for the initial rotor position. As the ISF neglects other periodic parts, the calculation time for analyzing the PMSMs can be drastically reduced. To verify the performance of the proposed method, the ISF and conventional method of full period FEA (FPF) with many steps were applied to three types of the PMSMs, interior PMSM (IPMSM), surface-mounted PMSM (SPMSM), and flux switching machine (FSM). The proposed method reduces the calculation time for deriving the TS curves of the SPMSM, IPMSM, and FSM as 86.35%, 89.39%, and 89.41%, respectively, compared with conventional methods of considering the periodic parts. The analysis accuracies at the operating points of each test models are 94.24%, 99.24%, and 99.86%, and the ISF ensures acceptable accuracy considering the reduced calculation time. Therefore, the ISF can be effectively used when deriving the TS curves of the PMSMs at the early design stage of the motors.

Optimization Design of the Electromagnetic Torque for Surface-Mounted PMSM Using GA and Finite Element Analysis for Electric Vehicle

Optimization Design of the Electromagnetic Torque for Surface-Mounted PMSM Using GA and Finite Element Analysis for Electric Vehicle

Simplified 3-D Hybrid Analytical Modelling of Magnet Temperature Distribution for Surface-mounted PMSM With Segmented Magnets

In this article, a simplified three-dimensional (3-D) hybrid analytical thermal model for surface-mounted permanent magnet (PM) synchronous machines is proposed and applied to investigate the influence of PM segmenting strategies on the spatial PM temperature distributions and hotspots. The developed 3-D hybrid thermal model synergies the lumped-parameter thermal model and analytical method and is able to estimate 3-D spatial temperature distributions and hotspots for both unsegmented and segmented surface-mounted PMs accounting for the uneven PM eddy current loss distributions. Meanwhile, by utilizing the proposed matrix-based post-processing methods, the developed hybrid analytical thermal model has a simple mathematical expression but persists in high estimation accuracy. Finally, the proposed hybrid analytical modelling method is validated by 3-D electromagnetic-thermal coupled FEA and experiments.

Design and Analysis of Modulated Magnetic Pole for Dual Three-Phase Surface-Mounted Permanent Magnet Synchronous Motor

In order to improve the air-gap magnetic field waveform and reduce the torque ripple of dual three-phase surface-mounted permanent magnet synchronous motors (PMSMs), a new surface-mounted modulated permanent magnet (PM) structure is proposed in this paper. Compared with the existing pole-cutting structure, the modulated magnetic pole does not need to customize the precise machining mold. However, when the modulation pole structure is installed, only the magnetic block-assisted assembly structure is designed to reduce the manufacturing cost. Based on the principle of specific harmonic elimination technology (SHET), the number, size and position angle of the modulated magnetic poles can be calculated, and the elimination or the injection of specific harmonics of the air-gap magnetic field can be realized, which can optimize the performance of the motor. It can be seen that the modulation pole structure based on SHET is also an effective method to improve the sinusoidal waveform of the air-gap magnetic field of the surface-mounted PM motor.

A Compensation Strategy of Flux Linkage Observer in SPMSM Sensorless Drives Based on Linear Extended State Observer

Flux linkage estimation based on the voltage model has been widely employed in surface-mounted permanent magnet synchronous machine (SPMSM) sensorless drives due to its simple implementation. To deal with dc-offset and dc-drift problems, the pure integrator is modified as a programmable low pass filter (LPF)in practice. However, the estimation accuracy of the rotor position is affected by the adopted filter. Although the position deviation is compensated in steady-state based on the frequency characteristics of the filter, the compensation effect deteriorates during a dynamic process which severely degrades the sensorless control performance. In order to effectively tackle this problem, a novel compensation strategy based on the linear extended state observer (LESO) is proposed in this paper. With the constructed LESO in the estimated synchronous rotating reference frame, the position estimation error can be detected and compensated both in the steady and dynamic state. Moreover, the observer is enhanced to improve the estimation accuracy in linear acceleration and deceleration. Finally, the feasibility of the proposed method is verified under various operating conditions with a 5.5 kW SPMSM drive system.

Analytical Modeling for Rotor Eddy Current Loss of a Surface-Mounted PMSM With Both Non-Ferromagnetic Conductive Retaining Sleeve and Shielding Cylinder

It is recognized that the rotor with shielding cylinder (SC) is one of the effective measures to restrain the rotor eddy current loss (RECL) for high-speed surface-mounted permanent magnet synchronous motors (PMSMs). At present, the RECL of PMSMs with multilayer composite rotor structure is mainly analyzed by the finite element method (FEM), which has obvious shortcomings in time-consumption and the mesh generation of thin SC. In this paper, a multi-layer subdomain analytical model for calculating the RECL of high-speed PMSMs with both non-ferromagnetic retaining sleeve and SC is proposed by taking the effects of eddy current reaction, stator slotting and current harmonics into account. Moreover, the 3-D distribution coefficient of eddy current in the SC is derived by the equivalent impedance method and the effects of temperature on the conductivity of the SC and RECL are obtained through equivalent thermal network (ETN) model. Based on the analytical model, the SC parameters are calculated to obtain the variation ranges when the RECL is minimum. Finally, the C-shape core experiment was built up to verify the correctness of the multilayer analytical model under different shielding layer conductivities and thicknesses.