Elmo Motion Control Ltd

Petah Tikva, Israel

Elmo Motion Control Ltd

Petah Tikva, Israel
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Thielemans S.,Ghent University | Ruderman A.,Elmo Motion Control Ltd | Reznikov B.,General Satellite Corporation | Melkebeek J.,Ghent University
IEEE Transactions on Power Electronics | Year: 2012

Flying-capacitor converters (FCCs), like most multilevel converter topologies, require a balancing mechanism of the capacitor voltages. FCCs feature natural voltage balancing when a special modulation technique is used. The classic methods, such as phase-shifted pulse width modulation (PS-PWM), result in very slow balancing for some duty-ratio ranges. Previous work has shown that for a single-leg five-level FCC, one time constant is infinite for a zero desired output voltage. In this paper, a modified PS-PWM scheme for a single-leg five-level FCC is presented, which results in faster balancing over the total duty-ratio range. The modified PS-PWM scheme is studied, resulting in an averaged voltage-balancing model. This model is verified using simulations and experiments. The modified PS-PWM scheme solves the slow-balancing problems of the normal PS-PWM method for odd-level FCCs, while maintaining the passive control property, and it provides a self-precharge capability. © 2012 IEEE.


Ruderman M.,TU Dortmund | Ruderman A.,Elmo Motion Control Ltd | Bertram T.,TU Dortmund
IEEE Transactions on Industrial Informatics | Year: 2013

The impact of additive periodic torque disturbances on the controlled motion of permanent magnet motors can be significant. The paper shows how an observer-based drive control can efficiently reject the harmonic torque disturbances providing smooth angular velocity. The proposed control design is based on the state-space torque harmonics representation and Luenberger observer that proved to be adequate. The designed control algorithms are verified using an experimental setup with a permanent magnet synchronousmotor with well-detectable torque harmonics. The rejection of additive position periodic torque disturbances is experimentally demonstrated for two first harmonics and that for different angular velocities. © 2012 IEEE.


Ruderman A.,Elmo Motion Control Ltd | Reznikov B.,General Satellite Corporation | Busquets-Monge S.,University of Barcelona
IEEE Transactions on Industrial Electronics | Year: 2013

Voltage total harmonic distortion and quadratic voltage ripple criteria are accepted figures of merit of a multilevel pulse width modulation (PWM) converter voltage quality. The dominating frequency domain approach does not deliver simple closed-form expressions and practically requires accounting up to 40-50 switching harmonics. Assuming infinitely high switching frequency, suggested time domain approach to a multilevel multiphase PWM voltage quality evaluation provides closed-form piece-wise analytical solutions. These simple formulas clearly reveal the dependence on modulation index for arbitrary voltage level and odd phase numbers. The results are applicable to any type of multilevel converters (including interleaved, open winding and other) operated with nearest level/nearest space vector modulation and relatively high switching frequency. © 2012 IEEE.


Ruderman A.,Elmo Motion Control Ltd | Reznikov B.,General Satellite Corporation
Proceedings of the International Conference on Optimisation of Electrical and Electronic Equipment, OPTIM | Year: 2010

The paper presents simple closed-form analytical expressions for PWM power converter ripple voltage Normalized Mean Square lower and upper bounds. These estimates obtained in time domain are asymptotic in the sense that switching-to-fundamental frequencies ratio is supposed infinitely large. Ripple voltage Normalized Mean Square in the first approximation represents normalized additional eddy current iron core loss in electric motor, transformer, or coupling inductor caused by converter switching that is a dominant switching loss mechanism. Non-PWM voltage control schemes like sliding mode, hysteresis, direct torque and power control, and predictive control may deliver better tracking, and disturbance rejection performance at the expense of compromising voltage quality thus increasing converter switching caused iron core loss. Comparison with PWM voltage quality asymptotic lower and upper bounds may be useful for making a fair assessment of different non-PWM strategies from additional switching caused iron core loss perspective. ©2010 IEEE.


Ruderman A.,Elmo Motion Control Ltd | Reznikov B.,General Satellite Corporation
Proceedings of the International Conference on Optimisation of Electrical and Electronic Equipment, OPTIM | Year: 2010

The paper presents a comparison of phase-shifted and modified level-shifted carrier-based PWM strategies for a three-level H-bridge flying capacitor converter. While the optimal voltage quality of the nearest level switching may be obtained using both of them, natural voltage balancing dynamics is different. Using elementary circuit theory and switched system time domain analysis, it is possible to obtain simple analytical averaged voltage balancing dynamics solutions. Modified level-shifted carrier-based PWM is shown to provide much faster voltage balancing dynamics, especially, for small DC PWM voltage commands and AC PWM modulation indices. The explanation of this fact is obtained by analysis of zero voltage state sequences for different modulation strategies. Relatively fast voltage balancing dynamics rate provided by modified level-shifted carrier-based PWM for zero voltage command makes it possible to implement simple flying capacitors self-precharge procedure at power-up. ©2010 IEEE.


Ruderman A.,Elmo Motion Control Ltd | Reznikov B.,General Satellite Corporation
Proceedings of EPE-PEMC 2010 - 14th International Power Electronics and Motion Control Conference | Year: 2010

Voltage source converter Pulse Width Modulation common-mode voltages have an adverse affect of inducing motor shaft voltages and bearing currents that result in premature bearings failure. Common-mode voltage cancellation PWM strategies significantly compromise the optimal voltage quality of the nearest three space vector modulation. The paper presents a quantitative estimation of associated motor PWM loss increase for a three-phase multilevel converter. © 2010 IEEE.


Ruderman A.,Elmo Motion Control Ltd | Reznikov B.,General Satellite Corporation
IEEE International Symposium on Industrial Electronics | Year: 2010

Voltage total harmonic distortion and related quadratic criteria are accepted as figures of merit of a multilevel PWM converter voltage quality. The dominating frequency domain voltage quality evaluation approach, in fact, is essentially numerical as it involves infinite double Fourier series expansion with Bessel function coefficients and requires high switching harmonics count. Suggested time domain approach for multilevel PWM converter voltage quality evaluation delivers simple piece-wise analytical solutions that clearly reveal the dependence on modulation index for an arbitrary number of voltage levels. The results are applicable to any type of multilevel converters with optimal nearest three space vector PWM allowing for fast comparative evaluation of voltage quality for filterless grid-connected converters with different levels count. © 2010 IEEE.


Busquets-Monge S.,University of Barcelona | Ruderman A.,Elmo Motion Control Ltd
IEEE International Symposium on Industrial Electronics | Year: 2010

This paper presents four carrier-based PWM strategies for diode-clamped converters of any number of levels and any number of legs (phases). These carrier-based PWM strategies guarantee the dc-link capacitor voltage balance in every switching cycle without the need of additional hardware and with low dc-link capacitance values for any modulation index and load, provided that the sum of leg currents equals zero. The performance of the presented carrier-based PWM strategies, in terms of dc-link capacitor voltage balance and total harmonic distortion in the output line-to-line voltages, is evaluated through simulation, showing a tradeoff between the simplicity of the carrier-based PWM implementation and its total harmonic distortion performance. © 2010 IEEE.


Ruderman A.,Elmo Motion Control Ltd | Reznikov B.,General Satellite Corporation
IEEE International Symposium on Industrial Electronics | Year: 2010

Accepted voltage balancing dynamics research methods flying capacitor converters are based on frequency domain transformations that involve double Fourier series with Bessel function coefficients. Therefore, these methods require high mathematical skills, are not truly analytical and difficult to use in engineering practice. In this paper, a "physical" approach to switched systems analysis based on stitching analytical solutions for consecutive switching subintervals, is applied to flying capacitor average voltage balancing dynamics analysis. It is shown that time domain averaging methodology generates simple analytical solutions that reveal the dependences on load parameters, carrier frequency, and normalized DC voltage command (AC modulation index). The power of suggested approach is demonstrated using single-leg converter voltage balancing dynamics analysis examples. © 2010 IEEE.


Ruderman A.,Elmo Motion Control Ltd
Proceedings of the International Conference on Optimisation of Electrical and Electronic Equipment, OPTIM | Year: 2012

A challenge for DC-DC converters miniaturization is the inability to integrate passive components on silicon due to their relatively large size at modern operating frequencies of some MHz. Switched Capacitor Converters may be a preferred choice for developing new miniaturized product formats because of their relatively small size and elimination of magnetic elements. The size and cost a DC-DC power supply are essentially defined by its bulky filter (storage) capacitor that is selected to meet output voltage ripple requirements. This paper investigates into filter capacitance reduction possibilities in different reconfigurable step-down capacitive converters by capacitor balanced switching. It is shown that balanced switching approach allows for filter capacitor reduction by 30-50% for an open-loop operation with a target voltage conversion ratio. Reducing filter capacitance also allows to speed up converter open-loop dynamic response. © 2012 IEEE.

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