Integral refinable operators exact on polynomials

AbstractWe study integral refinable operators of integral type exact on polynomials of even degree constructed by using refinable B-bases of GP type. We prove a general theorem of existence and uniqueness. Then we study the Lp-norm of these operators and we give error bounds in approximating functions and their derivatives belonging to suitable classes. Numerical results and comparisons with other quasi-interpolatory operators having the same order of exactness on polynomial reproduction are presented

Kinetic-Rotor Self-Commissioning of Synchronous Machines for Magnetic Model Identification with Online Adaptation

This paper proposes a new magnetic model self-identification technique for synchronous machines to build the flux-map look-up tables (LUTs). Provided the shaft is free to turn, an alternating self-acceleration and deceleration sequence is envisaged for identification without a dedicated experimental rig or additional hardware. Respect to previous works, the stator flux and the stator resistance are adapted online during the run, thus eliminating the need for post-processing and the sensitivity to winding temperature variations during the test. Experimental validations on a 1.1 kW synchronous reluctance (SyR) and a 11 kW permanent-magnet assisted synchronous reluctance (PM-SyR) motors are provided

FIELD ORIENTED CONTROL OF IPM DRIVES FOR FLUX WEAKENING APPLICATIONS

Interior Permanent Magnet (IPM) drives are adapted to flux-weakening, then to constant power operation over a wide speed range. Most of the control strategies for IPM motor drives are based on the control of the current vector. Flux-weakening is obtained by proper current references, that are calculated according to the magnetic model of the motor. This approach needs the accurate characterization of the motor and it is sensitive to the inaccuracy and the variation of the model parameters. Moreover, in the case of a variable dc-link, an additional voltage loop is necessary to correct the current references values at different dc-link voltage levels. The direct control of the flux vector, in the stator flux oriented frame, is proposed here, with the aim of obtaining the constant voltage operation of the IPM motor drive in the flux weakening range by means of a very simple control algorithm. The proposed direct flux control is tested on an IPM motor drive designed for traction. The exploitation of the maximum torque in all the operating speed range is demonstrated. The control is also capable to adapt its flux and current set-points to different dc-link voltage levels with no need of additional voltage regulators. Discrete-time simulation and experimental results are presented and compared showing good accordance

On the exact evaluation of integrals of wavelets

Wavelet expansions are a powerful tool for constructing adaptive approximations. For this reason, they find applications in a variety of fields, from signal processing to approximation theory. Wavelets are usually derived from refinable functions, which are the solution of a recursive functional equation called the refinement equation. The analytical expression of refinable functions is known in only a few cases, so if we need to evaluate refinable functions we can make use only of the refinement equation. This is also true for the evaluation of their derivatives and integrals. In this paper, we detail a procedure for computing integrals of wavelet products exactly, up to machine precision. The efficient and accurate evaluation of these integrals is particularly required for the computation of the connection coefficients in the wavelet Galerkin method. We show the effectiveness of the procedure by evaluating the integrals of pseudo-splines

Three-phase SiC inverter with active limitation of all MOSFETs junction temperature

Estimating the junction temperature of power electronic devices is of paramount importance for assuring the reliable operation of power converters. Wide bandgap devices, that allow extremely high-power density levels, make thermal management even more critical than before. Despite the efforts of the scientific community, this problem is far from being solved. Techniques based on thermo-sensitive electrical parameters are gaining momentum in the scientific literature, although their application to real case scenarios is slowed down by many unsolved challenges. The aim of this paper is to present a three-phase SiC inverter capable of accurate junction temperature estimation for all the SiC power MOSFETs and of active limitation of the maximum junction temperature. The temperature estimate is based on the well-known correlation between the conduction resistance and the junction temperature of a semiconductor. It is implemented here on a 3-phase SiC inverter for racing cars used in formula SAE electric student competitions. The experimental results show the effectiveness of the proposed technique in terms of augmented reliability and augmented performance of the power converter

Three-phase Inverter for Formula SAE Electric with Online Junction Temperature Estimation of all SiC MOSFETs

The ability to monitor the junction temperature of power devices during the operation of a power converter will be the key enabler towards combined higher performance and higher reliability of power electronics. Starting from the well-known dependency of the RON with the junction temperature of SiC power MOSFETs, an innovative solution is proposed to obtain the high-dynamic estimation of the junction temperature of all the power devices. This work focuses on the commissioning stage of a three-phase, 2-level voltage source inverter, enabling the real-time temperature feedback of all six power devices of the bridge during operation. A selection of experimental results is reported

Highly effective and isotropic pinning in epitaxial Fe(Se,Te) thin films grown on CaF2 substrates

We report on the isotropic pinning obtained in epitaxial Fe(Se,Te) thin films grown on CaF2 (001) substrate. High critical current density values larger than 1 MA/cm2 in self field in liquid helium are reached together with a very weak dependence on the magnetic field and a complete isotropy. Analysis through Transmission Electron Microscopy evidences the presence of defects looking like lattice disorder at a very small scale, between 5 and 20 nm, which are thought to be responsible for such isotropic behavior in contrast to what observed on SrTiO3, where defects parallel to the c-axis enhance pinning in that directio