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Loop Model and Quasi Limit Cycle for Digitally Controlled Switching DC-DC Converters

Loop Model and Quasi Limit Cycle for Digitally Controlled Sw...

The 2010 International Conference on Computer Application and System Modeling(2010计算机应用与系统建模国际会议 ICCASM 2010)

作者： Feng Li Tingcun Wei Han Yan Ran Zheng School of Computer Science and Technology Northwestern Polytechnical University Xi'an China

ISBN: (纸本)9781424472352

Loop model and controlled object model for digitally controlled switching dc-dc converters are set up in this paper, and buck converters stability for both digital control and analog control are comparatively analyzed based on the proposed models. This paper also discusses the presence of one oscillation, called as quasi limit cycle, caused by one additional switching cycle delay in the digital feedback loop, and three methods to remove it are introduced and studied. Simulation results are provided to verify the correctness of proposed models and the validity of removal methods.

关键词： switching dc-dc converter limit cycle pulse-width modulation

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From geometric invariants and symbolic matrixes towards new perspectives on forecasting of PWM converter dynamics

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CHAOS SOLITONS & FRACTALS 2009年第3期42卷 1868-1877页

作者： Kolokolov, Yury V. Monovskaya, Anna V. UGRA State Univ Inst Appl Math Informat & Control Khanty Mansiysk 628012 Russia

In this paper the fractal method of nonlinear dynamics forecasting regarding PWM converters is developed by transition towards symbolic modelling. Previously, within the fractal method bounds the technique of combining of several forms of dynamics description (in the form of periodic process domains in a bifurcation diagram and in the form of time series) into one special space was presented [Chaos, Solitons and Fractals 2005;23(1), 24(3), 25(5)]. It was answered positively on the question about the possibility of estimation of transient convergence direction in real-time mode. Now, presentation of a dynamic process is proposed as the consecution of geometric invariants. Correspondingly, the symbolical model of a periodic process represents the combination of limited number of the invariants and a transient can be analyzed through the deviations from this model. As a result, it becomes possible to forecast the direction of transient convergence under parametric uncertainties, that is important in relation to the considered class of piece-wise dynamic systems. The proposed method is illustrated by computer simulations. (C) 2009 Elsevier Ltd. All rights reserved.

关键词： CASCADE converters pulse-width modulation PREDICTION theory DYNAMICS INVARIANTS (Mathematics) MATRICES FRACTALS COMPUTER simulation

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Design of practical sliding-mode controllers with constant switching frequency for power converters

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ELECTRIC POWER SYSTEMS RESEARCH 2009年第5期79卷 796-802页

作者： Navarro-Lopez, Eva M. Cortes, Domingo Castro, Christian Univ Manchester Ctr Interdisciplinary Computat & Dynam Anal Sch Comp Sci Manchester M13 9PL Lancs England CINVESTAV IPN Dept Ingn Elect Secc Mecatron Mexico City 07360 DF Mexico IPN Ctr Invest Computac Mexico City 07738 DF Mexico

A novel experimentally motivated method in order to design a family of easy-to-implement sliding-mode controllers for power converters is proposed. Two main results are presented. First, the relation between sliding-mode control and average control is reinterpreted so that the limitation of the switching frequency for the closed-loop system is achieved in a more direct way than other methods so far reported in the literature. For this purpose, a class of sliding surfaces which makes the associated equivalent control be the system average control is proposed. Second, the achievement of a constant switching frequency in the controlled system is assured without requiring the sliding-mode-based controller to be modified, unlike most previous works. As a result, the proposed sliding surfaces-type can be directly implemented via a pulse-width modulator. The control methodology is implemented for the voltage control in a boost converter prototype in which the load is considered unknown. Experimental results confirm high performance and robustness under parameters variation. Furthermore, the solution proposed is easy to implement and well-suited for other power converters. (C) 2008 Elsevier B.V. All rights reserved.

关键词： Power converters Sliding-mode control pulse-width modulation Nonlinear systems Discontinuous control

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A Modified Sector Based Space Vector PWM Technique for Five-Phase Drives

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IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING 2009年第4期4卷 453-464页

作者： Duran, Mario J. Glasberger, Tomas Dujic, Drazen Levi, Emil Peroutka, Zdenek Liverpool John Moores Univ Sch Engn Liverpool L3 3AF Merseyside England Univ Malaga Dept Elect Engn Malaga 29013 Spain Univ W Bohemia Dept Electromech Engn & Power Elect Plzen 30614 Czech Republic

Space vector PWM (SVPWM) is a Popular and well-known technique for standard three-phase drives, which has been extended recently to multi-phase voltage source inverters (VSIs). Several SVPWM techniques, which utilize the principle of vector space decomposition (VSD), have been developed for various operating modes. The VSD approach inherently relies on considerations in two-dimensional (2-D) subspaces, while SVPWM for a multi-phase VSI is in essence a Multidimensional problem. Hence, ail alternative approach to SVPWM, which is based oil the direct multi-dimensional space consideration in the space vector selection process rather than oil space vector selection in 2-D subspaces obtained by vector space decomposition, has been recently introduced. Good performance has been identified, but the method is complex and difficult for the real-time implementation. This article therefore combines multi-dimensional SVPWM approach with offline calculations to achieve required output voltage generation under non-sinusoidal and/or unbalanced voltage requirements, which represent the most challenging operating conditions from the point of view of the vector selection for PWM. As a consequence, the implementation becomes rather simple in standard DSPs. The performance of the algorithm is verified by simulation and experimentation. (C) 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

关键词： multi-phase voltage source inverters pulse-width modulation multi-dimensional space

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Harmonic analysis of pulse-width modulated systems

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AUTOMATICA 2009年第4期45卷 851-862页

作者： Almer, Stefan Jonsson, Ulf Royal Inst Technol S-10044 Stockholm Sweden

The paper considers the so-called dynamic phasor model as a basis for harmonic analysis of a class switching systems. The analysis covers both periodically switched systems and non-periodic systems where the switching is controlled by feedback. The dynamic phasor model is a powerful tool for exploring cyclic properties of dynamic systems. It is shown that there is a connection between the dynamic phasor model and the harmonic transfer function of a linear time periodic system and this connection is used to extend the notion of harmonic transfer function to describe periodic solutions of non-periodic systems. (C) 2008 Elsevier Ltd. All rights reserved.

关键词： pulse-width modulation Harmonic analysis Dynamic phasors Periodic systems Switched-mode circuits

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An Integrated Approach to Design High Performance Controllers for PWM VSC Converters

An Integrated Approach to Design High Performance Controller...

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2nd International Conference on Power Engineering, Energy and Electrical Drives

作者： Ramos, Carlos Martins, Antonio Carvalho, Adriano Univ Porto Fac Engn P-4200465 Oporto Portugal

ISBN: (纸本)9781424446117

The modeling of grid connected voltage source converters results in a MIMO system with cross coupling between the two inputs and the two outputs. The usual approach is to design the two compensation controllers for the direct path and use a feed forward component to compensate the coupling. However, this term can lead to significant errors since the associated parameters can change in time. A controller that can directly handle this coupling term is the best approach to maintain high performance levels. The main purpose of the paper is to present a methodology to design a current controller based on the concept of a controller in the complex domain. The complex controller is obtained using the pole placement method and its extension to high order systems is discussed. Finally, simulation and experimental results are presented, clearly, demonstrating the validity of the design approach.

关键词： Complex state-space Digital control pulse-width modulation Vector control Voltage-source rectifier

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Single Current Sensor Operation with Fixed Sampling Points Using a Common-mode Voltage Reduction PWM Technique

Single Current Sensor Operation with Fixed Sampling Points U...

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6th IEEE International Power Electronics and Motion Control Conference

作者： Cheng Xiaomeng Lu Haifeng Qu Wenlong Fan Yang Li Yituo Sheng Shuang Tsinghua Univ Dept Elect Engn Div Power Elect State Key Lab Power Syst Beijing 100084 Peoples R China

ISBN: (纸本)9781424435562

A method is proposed for reconstructing AC currents with a single DC side current sensor in three-phase AC motor drive system. The method is based on a common-mode voltage (CMV) reduction PWM technique called LuPWM, which eliminates most of the invalid regions for current reconstruction both around zero voltage and near active-vectors. It realizes fixed-point sampling which is favorable for implementation. And the current prediction is also easier than traditional methods. Furthermore, it remains the good property of LuPWM that the peak-to-peak value of CMV, which leads to the premature deterioration of motor bearings, is reduced to 1/3 of the traditional three-phase PWM method in each sector. The additional computation load is minimal, and it can be widely applied. Experimental results are presented to fully support the above-mentioned claims.

关键词： common-mode voltage current prediction current reconstruction pulse-width modulation single current sensor

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Equalizing DC Capacitor Voltages in Multimodule HVDC Using SHE-PWM

Equalizing DC Capacitor Voltages in Multimodule HVDC Using S...

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8th International Conference on Power Electronics and Drive Systems (PEDS 2009)

作者： Flourentzou, Nikolas Agelidis, Vassilios G. Univ Sydney Sch Elect & Informat Engn Sydney NSW 2000 Australia

ISBN: (纸本)9781424441662

Multimodule converter based high-voltage dc (HVDC) power transmission incorporates numerous voltage-source converters (VSCs) connected in series/parallel to provide increased voltage/current and hence power ratings. When a selective harmonic elimination pulse-width modulation (SHE-PWM) technique is employed to reduce the switching losses of the VSC modules, equalizing the voltages of the series-connected dc capacitors is required. In this paper, a voltage-balancing technique is reported. The technique relies on monitoring the voltage of each dc capacitor and when such voltage exceeds its pre-set band, the realization of the multilevel waveform reallocates the task to another VSC module to ensure that voltage balance between all capacitors is achieved. Eight VSC modules are considered in this paper and each one is modulated by a pre-calculated multilevel SHE-PWM waveform. The time-domain waveforms and their line-to-line voltage spectra are verified by simulation using PSCAD/EMTDC. Selected results are presented to confirm the viability of the proposed method.

关键词： Multimodule converter voltage-source converter selective-harmonic elimination pulse-width modulation high-voltage dc transmission

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Control of Neutral Point and Flying Capacitor Voltages in Five-Level SHE-PWM Controlled ANPC Converter

Control of Neutral Point and Flying Capacitor Voltages in Fi...

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4th IEEE Conference on Industrial Electronics and Applications

作者： Pulikanti, Sridhar R. Agelidis, Vassilios G. Univ Sydney Sch Elect & Informat Engn Sydney NSW 2006 Australia

ISBN: (纸本)9781424427994

This paper presents a control strategy for a five-level active neutral point clamped (ANPC) converter using selective harmonic elimination pulse-width modulation (SHE-PWM) method. The control strategy is used to balance both the voltage across the flying capacitors and the dc-link neutral point. The strategy introduces a small change in the switching angles, which is decided upon the voltage across the lower dc-link capacitor, the voltage of the flying capacitor and the direction of the load current. Simulation results generated by MATLAB/SIMULINK are presented to confirm the satisfactory performance of the proposed control strategy. The simulated distribution profile of the semiconductor losses is also reported.

关键词： Selective harmonic elimination pulse-width modulation neutral point clamped converter active neutral point clamped converter flying capacitor converter

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Driving method to reduce data refresh rate in nematic liquid crystal optical phased array

Driving method to reduce data refresh rate in nematic liquid...

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5th International Symposium on Instrumentation Science and Technology

作者： Liu Xiang Zhang Jian Wu Liying Xu Lin Harbin Inst Technol Sch Elect Engn & Automat Harbin 150080 Peoples R China

ISBN: (纸本)9780819473677

The structure of a storage capacitor in nematic liquid crystal optical phased array causes the data refresh rate to be higher than the liquid crystal switching frequency, which demands a high data bandwidth. A novel driving method was therefore proposed to reduce the data refresh rate. Without using a storage capacitor, the proposed method uses digital scanning instead of conventional analog scanning. Furthermore, digital scanning is able to drive all pixels in parallel and transmit driver data only once for one frame. 1-D nematic liquid crystal optical phased array was used to test the novel driving method. During the experiment two frames of driver data were alternately transmitted at a refresh rate of 10 Hz, and diffraction patterns were acquired. Experimental results demonstrate that the proposed method can be used to keep the data refresh rate lower than the liquid crystal switching frequency.

关键词： Nematic liquid crystal optical phased array pulse-width modulation data refresh rate

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