Magnetic Flux Linkage Research Articles

Uneven Demagnetization Fault Diagnosis in Dual Three-Phase Permanent Magnet Machines Based on Electrical Signal Difference

Dual three-phase permanent magnet (DTPPM) machines are suitable for applications with high power density and high reliability requirements. However, uneven demagnetization fault (UDF) can occur due to harsh working conditions. This article proposes a non-invasive, online detection method of UDF in DTPPM machines based on the electrical signal difference between two sets of three-phase windings, which can be more conducive to UDF diagnosis with higher sensitivity. Firstly, the influence of dual three-phase winding arrangements on phase permanent magnet (PM) flux linkage is investigated in DTPPM machines under UDF. It shows that the fault characteristic harmonics appear in fractional-slot DTPPM machines and integral-slot DTPPM machines where a single set of three-phase windings is rotationally asymmetric. Further, according to the three-phase relationship of harmonic vectors, it is analyzed whether the fault characteristic harmonics are reflected in stator currents or zero-sequence voltage components (ZSVCs). Notably, taking advantage of the structural feature in DTPPM machines, the proposed method obtains higher sensitivity of UDF detection, as the amplitudes of fault characteristic harmonics in electrical signal difference are larger than that in stator current or ZSVC in a single set of three-phase windings. Finally, experiments are conducted to validate the effectiveness of the proposed method.

Parameter and VSI Nonlinearity Hybrid Estimation for PMSM Drives Based on Recursive Least Square

Precise electrical parameters play important roles in the high-performance control of permanent magnet synchronous machines (PMSMs). This paper proposes a novel parameter and voltage source inverter (VSI) nonlinearity hybrid estimation method to accurately estimate stator resistance, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> -axis inductances, permanent magnet flux linkage, and VSI nonlinearity, in which the effects of magnetic saturation, cross-saturation, and temperature are all considered. The proposed hybrid estimation method consists of two parts: offline and online estimation. In the offline estimation, the four electrical parameters are successively identified by setting different operating conditions, and the identification results are stored in nonvolatile memory in tabular form. In the online estimation, the VSI nonlinearity and the compensation terms of stator resistance and permanent magnet flux linkage related to factors such as temperature and frequency are simultaneously identified by using the recursive least square (RLS) algorithm. Experimental results on a 300 kW PMSM drive system demonstrate that compared to the results achieved with the existing method, the proposed scheme achieves higher estimation accuracy. Consequently, the control performance of the system, such as the output current quality, is efficiently improved.

Rotor Speed and Position Estimation Analysis of Interior PMSM Machines in Low and Medium-High Speed Regions Adopting an Improved Flux Observer for Electric Vehicle Applications

This paper proposes a nonlinear flux linkage observer for the PMSM speed controls without motion sensors, introducing the deviation among the real stator flux linkage and an estimated stator flux linkage to suppress feedback and integral flux drift. In the position detection of an interior PMSM without a speed sensor, the traditional back EMF integration method uses a pure integrator, or LPF, to estimate the stator flux. Its inherent defects inevitably lead to inaccurate flux estimation, which directly affects the estimation of the motor mover position, resulting in the decline in motor control operation and the distortion of phase current. This paper uses an improved integrator with adaptive compensation. The projected value of the stator flux linkage has been derived from the estimated value of the rotor permanent magnetic flux linkage position angle and the algebraic model (m-model) of the stator flux linkage, along with a synchronous coordinate system. The IPMSM stator coil flux linkage obtained from the stator coil current and integral voltage models in the static coordinate system is compared to form a feedback closed-loop to suppress the integral drift, and using the cross-product approach of the actual and estimated flux linkage yields the projected value of the IPMSM rotor speed and position through a PLL. Compared with the existing motion-sensorless observers, the methodology proposed in this article is simple and exhibits better dynamic and static estimation performance. Extensive and comprehensive MATLAB computer simulation and experimental findings validate the proposed motion-sensorless control mechanism.

Virtual-Axis Injection Based Online Parameter Identification of PMSM Considering Cross Coupling and Saturation Effects

Existing online parameter identification methods of permanent magnet synchronous motors (PMSMs) are generally based on the voltage equations, the precision of which is affected by the cross coupling and magnetic saturation effects. In order to deal with this issue, a virtual-rotary-axis high-frequency signal injection (VHFSI) based online parameter identification method is proposed in this paper, where the cross coupling and magnetic saturation effects on the traditional d-q axis model are analyzed. On this basis, an optimized voltage model under the composite magnetic field rotary axis is introduced. In the proposed method, the cross-coupling angle and the d-q axis inductances can be identified by injecting the high-frequency signal into the constructed virtual rotary axis. In addition, the complex Simpson integral algorithm is adopted to obtain the information of the incremental and apparent inductances. Finally, the permanent magnet flux linkage can be estimated based on the composite magnetic field rotary axis voltage equations. The effectiveness and feasibility of the proposed method are verified by the experiments on a 2.2-kW PMSM drive.

트랙션용 다자유도 구형 전동기의 구동을 위한 간접 벡터 제어 연구

The multi-degree-of-freedom spherical motor for traction has characteristics of rotation and steering. Although it is base on the rotation principle of an induction motor, only a spherical motor control method is required for rotation and steering. In order to estimate the speed command of the rotor, the mechanical angular velocity of the rotor is measured using an optical sensor, and the slip angular velocity is calculated with the current command of the d-q axis stator of the synchronous coordinate system. The rotor magnetic flux angle can be obtained in the above two ways, and through this, the vector control of the spherical motor is achieved. The desired magnetic flux component current and torque component current are distributed to operate the spherical motor. As such, the indirect vector control method has advantages in that it is simple to implement because it does not use the magnetic flux linkage of the rotor and that it is easy to operate from low speed to rated speed.

Design Tradeoff Between Saliency Ratio and PM Flux Linkage in Variable Flux Memory Machines

To achieve flexible flux regulation, variable flux memory machines (VFMMs) are normally characterized by a high permanent magnet (PM) flux linkage design, which generally reduces the saliency ratio of the machine. In order to further reveal the internal performance tradeoffs, this paper investigates the relationship between the saliency ratio and PM flux linkages of VFMMs by combining the equivalent magnetic circuit models and the finite element (FE) method. Three hybrid-magnetic-circuit (HMC) VFMMs having different PM grades and saliency ratios are chosen as the case studies to analyze and reveal the influence of flux linkages and saliency ratios on the major electromagnetic characteristics. First, the no-load and dq-axes equivalent magnetic circuit models of the investigated machines are established successively to obtain the PM flux linkages and dq-axes inductances of the machines. Then, the relationships between the electromagnetic torque and the key design parameters are obtained based on the space vector model. Next, the maximum torque per ampere (MTPA) trajectory is portrayed to determine the flux-weakening characteristics of the VFMMs. Afterwards, the electromagnetic characteristics of the three machines are compared and analyzed to confirm the previous theoretical analyses. Finally, an HMC-VFMM prototype is fabricated and tested to verify the effectiveness of the analysis.

Modified Active-Power MRAS Based Adaptive Control With Reduced Sensors for PMSM Operated Solar Water Pump

In a permanent magnet synchronous motor operated solar water pump (SWP), a current sensor is used for realizing maximum power control of photovoltaic array, while a speed sensor is used for implementing vector control of motor. These sensors increase cost and reduce reliability of SWP. Besides, such sensors are temperature sensitive, which thereby limits applicability of system for applications like surface water-pumping. Thus, a modified active-power model reference adaptive system (MAP-MRAS) for elimination of these two sensors is presented in this article. The presented MRAS structure estimates speed along with permanent magnet flux linkage and armature resistance, where estimated parameters are continuously updated in adaptive model. Thus, presented MAP-MRAS is parameter independent unlike conventional MRAS. The PV power is then estimated by using estimated speed. Based on the sensed voltage and estimated power of photovoltaic (PV) array, its maximum power control is realized. Hence, there is no need for sensing PV current. Besides, developed estimated speed based maximum power control scheme does not demands extra converter. The presented MRAS structure is realized on dSPACE1202 platform, and then its effectiveness is demonstrated through test performances obtained on a laboratory prototype of system under different operating conditions.

Efficient Nonlinear Multi-Parameter Decoupled Estimation of PMSM Drives Based on Multi-State Voltage and Torque Measurements

Accurate and fast parameter estimation is essential for efficient operation and control of permanent magnet synchronous machine (PMSM). In this paper, a novel multi-parameter decoupling estimation method based on multi-state measurement is proposed to analyze and estimate the important parameters including winding resistance, permanent magnetic flux linkage, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$d-q$</tex-math></inline-formula> axis inductances. An improved PMSM model containing inverter distorted voltage and nonlinear inductance considering magnetic saturation is established at first, then the model is decoupled to reduce the cross influences among the parameters and improve the computation efficiency through model dimension reduction according to the proposed decoupling method, and finally each parameter is estimated from multi-state voltage and torque measurement with improved efficiency and accuracy. This decoupling method separates the resistance and the inductance based on electromagnetic torque and reluctance torque, which is the crucial part of the estimation method proposed in this paper. Experiment on a PMSM driving system and comparison with existing methods are conducted to show that the proposed estimation method can improve the accuracy of estimation and calculation efficiency.

Formulas calculating the reactance of tubular busbars and their derivation in primary electrical connection schemes

Electrical switching operation in a substation which locates in a high-voltage transmission system alters operating modes of main wiring in either the substation or the system. Major alterations may have negative influences on the switchgear of main wiring in a short time. The quantitative study of this problem has to be based on establishing equivalent circuits of main wiring, when there rarely are formulas to calculate the reactance of tubular busbars. In this paper on the basis of the electromagnetic field theory, the magnetic induction and flux linkages outside and inside tubular conductors are obtained from the Ampere Loop Theorem, and then the formulas to calculate approximately the reactance of tubular busbars with a three-phase parallel arrangement are derived. From the process and results of the calculation in an example it may be seen that the formulas are applied simply, conveniently and rapidly, and may be valuably spread in practical electrical engineering.

Design and analysis of a new bearingless switched reluctance motor

A bearingless switched motor with permanent magnets in the stator yoke (BSRM-PMSY) with two sets of windings on each stator tooth pole is studied. The current in one set of windings mainly controls the motor torque, and rotor suspension can be realised by adjusting the current in the other set of windings. Each stator module unit of the motor is composed of a permanent magnet and two U-shaped iron cores. Finally, a BSRM-PMSY finite element simulation model is established to explore the static characteristics of the motor, including magnetic field distribution, permanent magnet flux linkage and harmonic analysis, back electromotive force (EMF) and harmonic analysis, suspension performance, and so on. The analysis of the simulated results lays a foundation for the establishment of a BSRM-PMSY mathematical model and control system.

A Study of Reduced Torque Compensation Method Under Temperature Variation Based on Single Torque-Current Lookup Table

In permanent magnet motors, the stator resistance and magnetic flux of the magnet change as the temperature increases. These changes result in a change in the maximum torque point per unit ampere (MTPA) of the motor. Without adequate compensation, this leads to a decrease in output torque. For this reason, look-up table (LUTs) are prepared over the temperature range and used for interpolation. This paper proposes a method to compensate for the output torque reduction due to a temperature increase using only a single LUT prepared at a base temperature. First, an estimation of the magnetic flux linkage and the output torque using a single LUT is performed. Second, the problem is modeled as a limited optimization problem to minimize the loss due to the torque reduction. The magnetic flux linkage and output torque are calculated in real time through the fundamental active power. The compensation value is calculated using the Lagrange multiplier method, an optimization technique, using the estimated magnetic flux linkage and output torque. The proposed method is verified by comparing it with other algorithms through simulation and experiment.

Adaptive Deadbeat Predictive Control for PMSM-based solar-powered electric vehicles with enhanced stator resistance compensation

This article introduces an innovative approach called Adaptive Deadbeat Predictive Control (ADPC), specifically designed to regulate the operation of a Permanent Magnet Synchronous Motor (PMSM) within a solar-powered electric vehicle (SEV). Considering the influence of factors such as magnetic saturation, material aging, and temperature fluctuations, discrepancies may arise between actual and nominal parameter values. Notably, the stator inductance, permanent magnet flux linkage, and stator resistance are crucial variables in this context. The article conducts an in-depth theoretical examination of the consequences of these parameter mismatches on the overall stability of the system. To mitigate the effects of stator resistance variability, an adaptive control methodology is proposed. This strategy hinges on real-time control adaptation, achieved by continuously estimating the resistance value through diligent consideration of the actual winding temperature. The proposed Adaptive Deadbeat Predictive Control framework is seamlessly implemented and simulated within the MATLAB Simulink environment. The simulation results eloquently validate the efficacy of the proposed control approach, showcasing its adeptness in mitigating the system’s sensitivity to stator resistance deviations, thereby fortifying the overall control resilience.

Transient Performance Improvement of Deadbeat Predictive Current Control of High-Speed Surface-Mounted PMSM Drives by Online Inductance Identification

This article presents an analytical derivation of transient performance deterioration for high-speed surface-mounted permanent magnet synchronous machine (SPMSM) drives under parameter mismatches, with an advanced deadbeat predictive current control (DBPCC), which exhibits fast dynamics and strong robustness with disturbances rejection. All the influential factors, including permanent magnet flux linkage and inductance mismatches, inverter nonlinearity, and speeds are taken into account in the analysis. It is shown that the transient performance with the advanced DBPCC is only dependent on inductance accuracy. Large transient overshoot and cross-coupling in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> -axis currents at high speeds arise due to inductance mismatch. Based on the understanding gained through the analysis, a novel inductance identification method is also proposed in this article, which significantly improves the transient performance of high-speed SPMSM drives. The proposed online inductance identification method does not require signal injection, is nonintrusive, and can be easily implemented. By integrating the proposed method with the advanced DBPCC, the close-to-ideal deadbeat control can be achieved for high-speed SPMSM drives even in the presence of parameter mismatch and inverter nonlinearity. Both the analysis and proposed method have been validated experimentally on a prototype high-speed (30 000 r/min) SPMSM drive under various conditions.

Multiple Synchronous Rotating Frame Transformation-Based 12th Current Harmonic Suppression Method for an IPMSM

In order to solve the problem that the three-phase current of the interior permanent magnet synchronous motor (IPMSM) contains the 11th and 13th current harmonics, a multiple synchronous rotating frame transformation (MSRFT)-based current harmonic suppression method is established. Firstly, the influencing factors of current harmonics in IPMSM vector control are analyzed, and the influence mechanism of the inverter’s dead-time effect and the permanent magnet flux linkage harmonics on the current harmonics is described. Secondly, a simple current harmonic extraction method is proposed by optimizing the traditional current harmonic extraction method based on MSRFTs. The proposed method achieves the accurate extraction of the current harmonic components. Thirdly, a harmonic voltage generation method is established and is combined with the proposed current harmonic extraction method to form a current harmonic suppression strategy. Finally, the feasibility and effectiveness of the proposed method are verified via MATLAB/Simulink simulations and experiments. The simulation and experimental results show that the proposed current harmonic extraction method can extract the current harmonic components accurately, and the proposed current harmonic suppression strategy can suppress the 11th and 13th current harmonics effectively.

Analysis of mechanical flux-weakening by using the end-cap of the switched flux permanent magnet machines

PurposeThe purpose of this study is to develop a novel mechanical flux-weakening topology for the switched flux permanent magnet (SFPM) machine to extend the speed range, which will be suitable for the electric vehicles and hybrid electric vehicles.Design/methodology/approachThe 3 dimensional mechanical flux-weakening model with flux adjusters (FAs) in the end-cap is established. Subsequently, the electromagnetic performance is compared between the SFPM machine with FAs in the end-cap and without FAs. The open circuit flux-linkage is calculated by finite element analysis (FEA) to investigate the influence of this mechanical flux-weakening topology together with the d/q-axis inductance. The flux-weakening capability and torque-speed curve is also calculated.FindingsThe proposed topology decreases the permanent magnet flux-linkage and increases the d-axis inductance, which improve the flux-weakening capability simultaneously. Subsequently, the speed range and constant power region are much wider than those without FAs. Finally, the prototype is fabricated and the measured result of the open circuit back electromotive force has good agreement with the FEA result.Originality/valueThis paper provides a novel mechanical flux-weakening topology with FAs in the end-cap for the SFPM machine, whose volume is smaller than another mechanical flux-weakening topology with FAs at the stator outside. Thus, higher torque and power density can be obtained compared with the SFPM machine with FAs at the stator outside.

Design of an Aviation Dual-Three-Phase High-Power High-Speed Permanent Magnet Assisted Synchronous Reluctance Starter-Generator With Antishort-Circuit Ability

This article proposes a novel dual-three-phase high-power high-speed permanent magnet assisted synchronous reluctance starter generator (PMaSynR SG) for aviation application, which has the characteristics of high efficiency, high power density, high reliability, and excellent antishort-circuit ability. The proposed PMaSynR SG can obtain higher efficiency and power density by embedding permanent magnet in the rotor topology compared with the synchronous reluctance generator, and has better antishort-circuit ability compared with the permanent magnet synchronous starter-generator. Moreover, design of dual-three-phase winding is adopted, which not only reduces the phase current, but also improves the reliability. In this article, the topological structure, characteristics and principle of PMaSynR SG are systematically studied at first. Second, a simplified <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> -axis equivalent magnetic circuit model is established, and the expressions of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> -axis inductance and permanent magnet flux linkage are derived on the basis of the basic parameter selection. Then, combined with parameter sensitivity analysis, the influence law of rotor structural parameters on antishort-circuit ability and electromagnetic performance is revealed. Finally, a 40 kW 24 000 r/min PMaSynR SG is designed and manufactured. The simulation and experimental results show that the proposed PMaSynR SG has excellent electromagnetic performance with the power density of 3.1 kW/kg and the efficiency of 94%, while the short-circuit current is only 59% of its rated value.

Analysis of Analytical Magnetic Field and Flux Regulation Characteristics of Axial-Flux Permanent Magnet Memory Machine

Due to the high power density, short axial size, and wide permanent magnet (PM) flux linkage regulation range, an axial-flux PM memory machine (AFPMMM) with hybrid Halbach array is investigated in this article. To solve the problem of magnetic density variation of Halbach array composed of different types of PMs in asymmetric bilateral air-gap structure, the analytical method for calculating the air-gap flux density of AFPMMM is presented through mathematical analysis, which uses cylindrical coordinate system instead of Cartesian coordinate system and is solved by equivalent method, separated variable method, and boundary conditions. The magnetic field generated by the Halbach array is divided into three directions: radial, circumferential, and axial. The analytical model is compared with the finite element method (FEM) simulation results to verify its effectiveness. In addition, an approximate piecewise linear hysteresis model with parallelogram return line is established based on the analytical expression of magnetic field. By applying different pulse currents to change the residual flux density of PM, the flux regulation characteristics of the motor are studied, and it is found that the air-gap flux density of the motor can be smoothly adjusted by continuously changing the pulse current, which plays a positive role in solving the problem of online magnetic regulation of the motor.

Permanent Magnet Flux Linkage Identification Method of the Model Predictive Current Control System for PMSM

Accurate identification of permanent magnet flux linkage can effectively improve the control performance of model predictive current control system of permanent magnet synchronous motor (PMSM). This paper reviews the existing identification methods of permanent magnet flux linkage of PMSM first and then proposes an identification method of permanent magnet flux linkage based on an improved unscented particle filter, the problem of particle diversity reduction of the traditional unscented particle filtering algorithm is solved, and the identification performance of permanent magnet flux is improved. Simulation research and experimental verification of the proposed method are carried out, and the simulation and experimental results confirm the effectiveness of the proposed method.

Effect of Mutual Magnetic Flux Linkage Between Stages of an Induction Coilgun on Its Performance

In a multistage electromagnetic induction coilgun (EIC), the time-varying magnetic flux generated by the first stage (or coil) links with the coils in the subsequent stages and induces EMF across their terminals. The magnetic flux linkage and the induced EMFs depend on the distance between the stages (or coils). This induced EMF circulates a current through the coils in the subsequent stages, if allowed to flow by such means of the pulsed power source (PPS) connection with these coils, i.e., it depends on the winding direction (clockwise or anticlockwise) of the coils and the connection of the crowbar diode (CD) in the PPS circuit. If CD is connected in parallel to the capacitor bank, then the main series switch averts this induced current flow through the coil, but if CD is connected in parallel to the coil following its winding direction, then induced current flows through the coil. In this article, the effect of this induced current on the projectile motion inside a multistage EIC is analyzed using hollow projectiles of different lengths but of fixed mass and outer diameter. Computational analysis is performed using a finite element method (FEM)-based software, Ansoft Maxwell, with excitation given only to the first stage. The results are then experimentally validated with a two-stage EIC facility developed. Only two stages are considered since farther stages will have insignificant magnetic flux linkage with the first stage and the projectile. For each projectile, the distance between the two stages (or coils) is varied, starting from 2.8 to 14.8 cm with a linear step of 1 cm. The results indicate that the projectile motion is affected in a multistage system, depending on the distance between the stages and the projectile length. The analysis will be beneficial for maintaining a suitable distance between the stages in a multistage type of EIC.

A Phase-Domain Model of Dual Three-Phase Segmented Powered Linear PMSM for Hardware-Assisted Real-Time Simulation

In this article, a hardware-assisted real-time simulation phase-domain (PD) model of a dual three-phase segmented powered linear permanent magnet synchronous machine (SP-LPMSM) used in electromagnetic drive is established. The model is able to consider the end-effect, saturation effect, coupling effect, and open-phase fault conditions, which are specially occurs in the segmented structure in SP-LPMSM. The unbalanced inductances and saturation effect caused by the segmented structure are investigated and a simplified look-up table for inductances is introduced. Additionally, to accurately evaluate the coupling effect, the permanent magnet (PM) flux linkage is decoupled into the product of unit PM flux linkage and coupling coefficient. In order to avoid the numerical impulse caused by the derivative in the progress of calculating back-EMF, sigmoid function is adopted to express the coupling coefficient. Meanwhile, to make the PD-model compatible with the open-circuit fault conditions, incidence matrices and current constraint matrices are introduced to unify the PD-models with different winding connection types and open circuit faults into one general form. The PD-model realized in field-programmable gate arrays (FPGA) based hardware is validated in comparison with finite-element analysis results.