Enhanced Torque Control of a PMSM Supplied by a Four-Leg Voltage Source Inverter Using the Third Harmonic

This paper investigates an electrical drive composed of a four-leg voltage source inverter and a three-phase starconnected surface permanent magnet synchronous machine with concentrated windings. The inverter fourth leg is clamped to the neutral point of the machine. We find the current references leading to smooth torque and maximal torque per ampere operation in the presence of a third harmonic electromotive force component. We further analyze the advantages of the proposed topology in terms of torque increase and dc-link voltage requirements

EEMD-based windturbinebearingfailuredetectionusing the generatorstatorcurrenthomopolarcomponent

International audienceFailure detection has always been a demanding task in the electrical machines community; it has become more challenging in wind energy conversion systems because sustainability and viability of wind farms are highly dependent on the reduction of the operational and maintenance costs. Indeed the most efficient way of reducing these costs would be to continuously monitor the condition of these systems. This allows for early detection of the generator health degeneration, facilitating a proactive response, minimizing downtime, and maximizing productivity. This paper provides then an assessment of a failure detection techniques based on the homopolar component of the generator stator current and attempts to highlight the use of the ensemble empirical mode decomposition as a tool for failure detection in wind turbine generators for stationary and non stationary cases

Homopolar Current’s Copper Losses Analysis for Different Modulations in Open-End Winding Five-Phase drives

This work has been achieved within the framework of CE2I project. CE2I is co-financed by European Union with the financial support of European Regional Development Fund (ERDF), French State and the French Region of Hauts-de-France.This paper analyses the copper losses due to the homopolar current of a five-phase open-end winding machine supplied by a 10-leg inverter and a single DC voltage source. This topology can have non-null high frequency homopolar current components that can increase the machine’s copper losses and result in overheating of the motor phase windings. Accordingly, different modulation strategies are compared with the goal of reducing the homopolar current and, consequently the resulting copper losses. The comparison study is achieved using Matlab/Simulink and a finite element model in order to evaluate these losses.European Regional Development Fund (ERDF

Space Charge Studies on Mid-voltage Cable by Thermally Stimulated Depolarization Currents in the Melting Temperature Range.

In the present work, a XLPE mid-voltage cable from General Cable CO. has been studied by Thermally stimulated depolarization currents. Systematic measurements have been carried out in order to compare the conductive processes in this cable with previous results. Depolarization current as a function of thermal annealing, thermal history, polarizing field and polarizing time and temperature has been obtained. The results show the presence of a broad and complex heteropolar process between 60 and 120°C as expected. Annealing of the sample at temperatures above SOT develops an homopolar contribution associated to chemical components diffused from the cable semiconducting layers into the XLPE bulk. For annealing times of 60min at 140T and 2 days at 90°C, the homoplar current intensity reaches a maximum, decreasing and recovering the heteropolar sign with further annealing. Experiments performed with different polarizing times and temperatures show as well the presence of an homopolar contribution, overlapped to the heteropolar behavior, that increases continuously with polarizing time. These results indicate that conductive processes within the XLPE are probably responsible of homopolar charge injection

Introducing small storage capacity at residential PV installations to prevent overvoltages

Low voltage distribution feeders are designed for unidirectional energy supply from transformer to consumer. However, the implementation of small-scale PV production units on local utilities may result in bidirectional energy flows. The simultaneous power injection at sunny moments may cause a serious voltage rise along the feeder. These overvoltages may not only damage critical loads but also switches PV inverters off causing loss of green energy at the most productive moments. This paper presents a method to limit the voltage rise by introducing small battery buffers at local production sites. A smart inverter decides whether the PV energy is injected in the grid or buffered in the batteries. The relation between battery buffer size and overvoltage reduction is presented for a typical Belgian residential distribution feeder. The influence of the buffer along the feeder is calculated by working with synthetic load profiles and solar irradiation data

Understanding the three and four-leg inverter Space Vector

This paper shows a new point of view of the classical voltage space vectors and its implications on three and four-leg converters. It is easy to find in the literature, authors using bi-dimensional and threedimensional representations of the converter states. Nonetheless, the literature rarely specifies what these spaces represent. Therefore, this paper proposes a wide analysis of the state voltages and its references for three-leg, three-leg four-wire and four-leg inverters, in favour of understanding the space vector behaviour under three and four-wire scenarios.Postprint (published version

Analytical Optimal Currents for Multiphase PMSMs Under Fault Conditions and Saturation

An original analytical expression is presented in this paper to obtain optimal currents minimizing the copper losses of a multi-phase Permanent Magnet Synchronous Motor (PMSM) under fault conditions. Based on the existing solutions [i]opt1 (without zero sequence of current constraint) and [i]opt2 (with zero sequence constraint), this new expression of currents [i]opt3 is obtained by means of a geometrical representation and can be applied to open-circuit, defect of current regulation, current saturation and machine phase short-circuit fault. Simulation results are presented to validate the proposed approach

Inefficiencies in unbalanced three-phase power systems. Relationship between system asymmetry and instantaneous power waves

[EN] This work analyzes the energy phenomena occurring in linear power systems characterized by the presence of load unbalances, using the principles of the Unifying General Theory of Electric Power [1],[2]. The energy fluxes characterize each phenomenon in the power system, especially the energy associated with the asymmetry phenomenon; thus it is possible to quantify the asymmetry phenomenon from the instantaneous power shapes, manifested by three unbalanced sinusoidal fluxes, whose resultant is a sinusoidal wave. In addition, this work presents the relationship between the quantification of the phenomenon and the amplitudes of the power fluxesSabater I Serra, R.; Donderis Quiles, V. (2004). Inefficiencies in unbalanced three-phase power systems. Relationship between system asymmetry and instantaneous power waves. Renewable Energy and Power Quality Journal. 1(2):112-117. doi:10.24084/repqj02.223S1121171

Study of the charge profile of thermally poled electrets

The charge profile of thermally poled electrets has been studied using two different methods, laser induced pressure pulse (LIPP) and pulsed electroacoustic (PEA), to gain insight into the mechanisms that are activated and assess which is the most appropriate method to study the charge profile. Disc--shaped PET samples have been conventionally poled to activate both the alpha and the rho relaxation and, right after, partially discharged up to a temperature Tpd. In this way, samples with a different combination of dipolar and space charge polarization have been obtained. Both LIPP and PEA reveal asymmetric profiles for Tpd below the glass transition temperature, that progressively become antisymmetric for higher temperatures. The shape and evolution of the charge profiles can be explained assuming injection of negative carriers from the anode that enhances the trapping of positive carriers near this electrode. It can be observed that PEA is able to detect a wider variety of polarization mechanisms in the system while LIPP gives a simpler picture of the charge profile.Comment: 19 pages, 11 figure

Power-Integrated Circuit Active Leakage Current Detector

Most of the failures of induction motors become insulation faults, causing a permanent damage. Using differential current transformers, a system capable of insulation fault detection was developed, based on the differential relay protection scheme. Both signal injection and fault detection circuitry were integrated in a single chip. The proposed scheme is faster than other existing protection and not restricted to protect induction motors, but several other devices (such as IGBTs) and systems. This paper explains the principle of operation of fault protection scheme and analyzes an integrated implementation through simulations and experimental results. A power-integrated circuit (PIC) implementation is presented.Fil: Bulacio, M. F.. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Electronica; ArgentinaFil: González, Tomás Andrés. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Electronica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Marinelli, Guido. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Electronica; ArgentinaFil: Alonso, Ramiro. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Electronica; ArgentinaFil: Tacca, Hernán Emilio. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Electronica; Argentin