Unaprijeđeno upravljanje momentom visokobrzinskog pogona s asinkronim motorom bez mjerenja brzine

This paper presents improved torque control scheme for a high speed sensorless induction motor drive. The proposed high speed torque control scheme substitutes the flux oriented control by the voltage angle control in the flux weakening regime. This scheme uses maximum of available inverter voltage, alleviates well known problems of current control schemes in conditions with insufficient voltage margin and avoids the influence of estimated speed error to the achieved flux level. The algorithm uses similar slip control as flux oriented control algorithm, but is applied without an outer flux trajectory reference which is typical for the flux weakening, providing a fast and well damped torque response even if error in estimated speed is present. Experiments confirm the effectiveness of proposed torque control algorithm, smooth transition from the flux oriented control in the base speed region to the voltage angle control in the flux weakening, superior dynamic performance of the voltage angle torque control, and its robustness to an estimated rotor speed error.U radu je predstavljena unaprijeđena shema upravljanja za pogon visokobrzinskog asinkronog motora bez mjerenja brzine. Predloženi postupak zamjenjuje vektorsko upravljanje upravljačkom strukturom s upravljanjem kutom napona u slabljenju polja. Predložena shema koristi maksimalni raspoloživi napon invertora, eliminira dobro poznate probleme strujno reguliranih pogona u uvjetima s nedovoljnom rezervom napona i eliminira utjecaj greške u estimaciji brzine na dostignutu razinu toka. Algoritam koristi sličnu kontrolu klizanja kao i vektorsko upravljanje, ali bez tipičnog vanjskog zadavanja toka u slabljenju polja, pružajući brz i dobro prigušen odziv momenta čak i u slučaju greške u estimaciji brzine. Eksperimenti izvedeni na velikoj brzini vrtnje potvrđuju učinkovitost predložene regulacije momenta, gladak prijelaz iz baznog područja brzine u slabljenje polja, vrhunske dinamičke performanse upravljanja kutom napona i robusnost na pogrešku u estimiranoj brzini vrtnje

Designing Energy Conversion Systems for the Next Decade

Sustainable growth in energy consumption requires transition to clean and green energy sources and energy systems. Environment friendly and renewable energy systems deal with electrical energy and rely on efficient electrical power converters. High power electronics is the key technology to deal with the next generation of electrical energy systems. The door to future breakthroughs in high power electronics is opened by major improvement in semiconductor power devices and their packaging technologies.  New materials allow for much higher junction temperatures and higher operating voltages. Most importantly, advanced power semiconductor devices and novel converter topology open the possibility to increase the energy efficiency of power conversion and reduce the amount of heat. Although the waste heat created by high power converters can be put to use by adding on to heating systems, this option is not always available and the conversion losses are mostly wasted. At the same time, wasted heat is a form of pollution that threatens the environment. Another task for high power converters is efficient harvesting of renewable energy sources, such as the wind energy and the sun. Intermittent in nature, they pose a difficult task to power converter topology and controls. Eventually, high power converters are entering power distribution and transmission networks. With their quick reaction, with fast communication between the grid nodes and with advanced controllability of high power converters, a number of innovations can be introduced, facilitating the power system control and allowing for optimizations and loss reduction. Coined smart grid, this solution comprises two key elements, and these are intelligent controls and large static power converters. At virtually no cost, smart grids allow for a better utilization of available resources and it enlarges the stable operating range of the transmission systems. Therefore, it is of interest to review the future trends in designing high power converters

Analysis of the magnetomotive force in the multiphase machines within integrated battery chargers for the electric vehicles

In this paper we discuss magnetomotive force (MMF) in the multiphase machines during fast charging of batteries in electric vehicles (EV). Analytical considerations show that using an adequate topology of power converter and additional levels of freedom one can achieve a fast charging without creating any revolving magnetic field within the machine. They also show that this regime can be achieved by using only the elements of the traction system and without changing the configuration between charging and traction regimes. The simulation models have been developed for the relevant configurations of the stator asymmetrical winding in six-phase and nine- phase integrated electrical machines within the charging system of an EV. As the result, the time-space distribution of the magnetic field in charging mode is obtained. Based on the results, suggestions are given for the design of an integrated traction / charging system within electric vehicles

Finite Element Design of Rotor Permanent Magnet Flux Switching Machine with Arbitrary Slot, Pole and Phase Combinations

A two-dimensional finite element approach for designing RPMFS (Rotor Permanent Magnet Flux Switching) machines is presented in this paper. The proposed method enables fast, accurate and computationally efficient assessment of different RPMFS machine designs with an arbitrary number of rotor poles, stator slots and stator phases. The appropriate stator winding layout is assembled for any feasible slot, pole and phase combination by employing the winding distribution table, which contributes to automating the design process. Based on the proposed method, a program is developed using the Octave FEMM (Finite Element Method Magnetics) toolbox. The program is suited for the use in the design stage, where it is necessary to determine various machine parameters for given core dimensions, terminal voltage constraints and adopted value of current density in the conductors, while taking iron saturation effects into account. Verification was carried out by simulating torque and EMF waveforms for several RPMFS machine designs

Expression of Bcl-2-family proteins in peripheral blood B-lymphocytes in patients with cronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a neoplastic disease characterized by the accumulation of morphologically mature monoclonal CD 5+ B cells in the early phase (G0/G1) of the cell cycle. It is considered that the accumulation of neoplastically transformed lymphocytes B (CLL cells) is primarily the consequence of the disturbance, i.e., blockade of these cells' apoptosis process. Apoptosis is the specific process of programmed cell death regulated by numerous extracellular and intracellular mechanisms. The Bcl-2 proteins are well-known modulators of this process. Some of these proteins (such as Bcl-2, and Bcl-Xl) are anti-apoptotic, while others (such as Bad or Bax) are pro-apoptotic. Our study included the analysis of 20 peripheral blood specimens from 20 patients with CLL, and 20 peripheral blood specimens of healthy persons who represented the control group. Using Western blotting analysis, we quantitatively examined the protein expression of Bcl-2 family (Bcl-2, Bax, Bad, and Bcl-Xl). The level of Bcl-2 (p=3,68´10-10), Bax (p=0,019), and Bad (p=0,073) proteins expression was significantly increased in all the analyzed peripheral blood samples of patients, while the level of Bcl-Xl protein (p=0,75) did not significantly differ in peripheral blood samples of patients, compared to the controls. The results of this study showed that the increased level of expression of Bcl-2, Bax, and Bad protein represented the most striking feature of CLL cells. Moreover, the variations in the expression of only one protein of the Bcl-2 family could not represent the prognostic parameter in the treatment of this disease