In this paper, the zero sequence circulating current in open winding permanent magnet synchronous machine (OW-PMSM) drives with common dc bus is systematically analyzed for the first time. It is ...revealed that the zero sequence circulating current is affected by zero sequence back-electromotive force, cross coupling voltages in zero sequence from the machine side, pulse-width modulation induced zero sequence voltage, and inverter nonlinearity from the inverter side. Particularly, the influences from the cross coupling voltages in zero sequence and parasitic effect of inverter nonlinearity are investigated for the first time in this paper. Then, the synthetic model of the equivalent zero sequence circuit is proposed as well. Each cause is studied independently via analytical modeling, finite element analysis, and experiments. Meanwhile, to tackle this issue, the relevant suppression strategy using frequency adaptive proportional resonant controller is presented and tested on the 3 kW OW-PMSM platform.
This article overviews novel magnetic-field-shifting techniques for enhancing the torque in a new class of asymmetric rotor pole interior permanent magnet (AIPM) machines. The principle for torque ...enhancement is introduced first. AIPM topologies are then categorized in terms of asymmetries and symmetries of PM configuration and rotor core geometry. Subsequently, the merits and demerits of various AIPM rotor topologies in each category are analyzed and compared. Finally, the torque capabilities of selected AIPM machines are compared.
Single-layer (SL) non-overlapping windings are applied to flux reversal permanent magnet (FPRM) machines, to extend the family of stator-PM machines. The machine topology and operating principle are ...introduced, and the general rules of symmetrical phase flux-linkages in machines with various slot/pole number combinations are found. The even order coil flux-linkage harmonics can be cancelled in the resultant phase waveforms due to opposite polarities of either magnets or coils. Moreover, based on finite element (FE) analysis, the FRPM machines with different rotor pole numbers, equipped with SL or double-layer (DL) windings, are comprehensively compared. The results reveal that compared to their DL counterparts, the FRPM machines with SL windings (FRPM-SL) exhibit similar torques and iron losses, as well as enhanced flux-weakening and fault-tolerant capabilities due to higher self-inductances but lower mutual-inductances. A pair of FRPM-SL prototype machines are manufactured and tested to validate the predictions.
This paper proposes a novel scheme for the identification of the whole flux linkage map of permanent magnet synchronous machines, by which the map of dq -axis flux linkages at different load or ...saturation conditions can be identified by the minimization of a proposed estimation model. The proposed method works on a conventional three-phase inverter based vector control system and the immune clonal based quantum genetic algorithm is employed for the global searching of minimal point. Besides, it is also noteworthy that the influence of uncertain inverter nonlinearity and circuit resistance are cancelled during the modeling process. The proposed method is subsequently tested on two PMSMs and shows quite good performance compared with the finite element prediction results.
In this article, a low noise and simple initial position estimation and startup method based on high-frequency rotating sinusoidal voltage injection is proposed for interior permanent magnet ...synchronous machine. Different from the conventional method that uses negative sequence current and closed-loop position observer, the proposed method simply compares the three-phase high-frequency current amplitudes calculated by discrete Fourier transform to detect the rotor sector. The initial position can be obtained within only half of the injection cycle without parameter tuning. Thus, it is fast and simple compared to the conventional method. Both discrete and continuous rotor positions can be obtained and used for startup. Furthermore, to mitigate the acoustic noise during starting, a multifrequency injection strategy is introduced to reduce the noise emission caused by high-frequency voltage injection. Experiments are carried out to verify the effectiveness of the proposed method.
R2 corrections on screening length Zhang, Zi-qiang; Zhu, Xiangrong
Physics letters. B,
June 2024, 2024-06-00, 2024-06-01, Letnik:
853
Journal Article
Recenzirano
Odprti dostop
We study finite-coupling corrections on the screening length of a heavy quark-antiquark (QQ¯) pair moving in strongly coupled Super Yang-Mills plasma. We performed the analysis by computing the ...Wilson loop in a general AdS5 space with curvature-squared (R2) corrections and the Gauss-Bonnet (GB) background, respectively. For the general case, it is shown that the screening length with R2 corrections can be larger or smaller than that without R2 corrections depending on the correction coefficients, and these effects are more pronounced for the perpendicular case compared with parallel case. For the GB case, it turns out that increasing λGB (a dimensionless parameter in GB gravity) leads to decreasing the screening length thus reducing the binding energy of QQ¯ pair. In addition, we discuss how the screening length changes with the ratio of shear viscosity to entropy density at strong coupling under GB corrections.
In this article, a method of simultaneous sensorless rotor position and torque estimation is proposed for interior permanent magnet synchronous machines at standstill and low speed. The proposed ...method estimates the torque using high-frequency inductances identified from the current variations due to high-frequency square wave voltage injections in the estimated dq -axes, which are simultaneously used for sensorless rotor position estimation. The proposed method is not dependent on the fundamental model and has taken the cross-coupling effect into consideration, allowing for low cost and fast torque estimation at standstill and low speed. Both simulations and experiments are carried out to verify the effectiveness of the proposed method.
The imaginary part of a heavy quarkonium potential is studied at finite temperature and chemical potential using a holographic AdS/QCD model with conformal invariance broken by a background dilaton. ...It is shown that the presence of the confining scale increases the absolute value of the imaginary potential thus increasing the thermal width, reverse to the effect of the chemical potential. One step further, the results imply that the inclusion of the confining scale reduces the quarkonia dissociation while the chemical potential enhances it.
This article proposes a novel method for estimating the high-frequency (HF) incremental dq -axis and cross-coupling inductances of interior permanent magnet synchronous machines based on both the HF ...rotating and pulsating voltage injection techniques. It mainly includes three HF voltage injection stages, i.e., a HF rotating voltage injection in the stationary reference frame, and a pulsating voltage injection in the d -axis and a pulsating voltage injection in the q -axis of the synchronous rotating reference frame. Compared with conventional estimation methods which either use only rotating voltage injection, or use only pulsating voltage injections in the dq -axes, the proposed method neither requires the closed-loop position estimator to obtain the offset angle caused by the cross-coupling effect nor is sensitive to the delay effects caused by digital filters and voltage synthesis. The estimated results obtained by the proposed method show a good agreement with those by finite element analysis and are also compared with those obtained by the conventional methods.
Dual three-phase (DTP) permanent magnet synchronous machine (PMSM) systems exhibit high current harmonics due to low impedance to voltage disturbance such as inverter voltage errors and back-EMF ...harmonics. This article proposes a concept of virtual multi three-phase systems to achieve independent regulation of the current harmonics in a DTP PMSM system. The virtual multi three-phase currents are first reconstructed by appropriately shifting the phase of original physical DTP currents, and then decomposed with the help of vector space decomposition techniques. As a result, the fundamental and the major current harmonics, i.e., the 5th, 7th, 11th, and 13th, can be completely separated in several isolated subspaces, where the independent current control loops can be easily designed and implemented. Compared with existing methods, the steady-state and dynamic-state performance of current harmonic regulation are enhanced by the proposed virtual multi three-phase systems and the effectiveness is validated by experimental.
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