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    Piecewise affine large signal modeling of PFC rectifiers

    , Article 2007 IEEE International Symposium on Industrial Electronics, ISIE 2007, Caixanova - Vigo, 4 June 2007 through 7 June 2007 ; 2007 , Pages 3362-3366 ; 1424407559 (ISBN); 9781424407552 (ISBN) Tahami, F ; Molla Ahmadian, H ; Sharif University of Technology
    2007
    Abstract
    A problem associated with modeling and control of the power factor correction rectifiers is that the ac variations in duty cycle, as well as in the ac input voltage and current are not small, and hence the traditional small signal analysis is not justified. Nonetheless, the low-frequency components of the converter can be modeled via the circuit averaging technique, but the resulting equivalent circuits are, in general, time varying and highly nonlinear. Nonlinear stability analysis methods are not appropriate for analysis and control design of such complicated circuits. In this paper a piecewise affine approximation is introduced for modeling of switching circuits. This approach makes the... 

    Modeling and control of DC-DC series resonant converters: A polyhedral piecewise affine approach

    , Article PEDSTC, 2014 - 5th Annual International Power Electronics, Drive Systems and Technologies Conference ; 5- 6 February , 2014 , pp. 273-279 Afshang, H ; Tahami, F ; Molla-Ahmadian, H ; Sharif University of Technology
    Abstract
    The subject of modeling and stability analysis of dc-dc resonant converters is still a challenge. The conventional large signal nonlinear model of the resonant converter is derived using the sinusoidal approximation and averaging followed by linearization about an operating point. Models obtained with such method involve considerable approximation, and produce results that are limited for higher performance designs. Therefore, it is essential to investigate the stability of the resonant converters using a more sophisticated model. Because of semiconductors switching, dc-dc resonant converters are intrinsically hybrid systems consist of discrete input and continuous states. The complexity of... 

    Piecewise affine control design for power factor correction rectifiers

    , Article Journal of Power Electronics ; Volume 11, Issue 3 , 2011 , Pages 327-334 ; 15982092 (ISSN) Tahami, F ; Poshtkouhi, S ; Ahmadian, H. M ; Sharif University of Technology
    2011
    Abstract
    Single-phase power factor correction (PFC) converter circuits are non-linear systems due to the contribution of their multiplier. This non-linearity causes difficulties in analysis and design. Models that reduce the system to a linear system involve considerable approximation, and produce results that are susceptible to instability problems. In this paper a piecewise affine (PWA) system is introduced for describing the nonlinear averaged model. Then robust output feedback controllers are established in terms of the linear matrix inequality (LMI). Simulation and experiments results show the effectiveness of the proposed control method  

    Hybrid control of the dc-dc SRC operating below resonance

    , Article IET Power Electronics ; Volume 10, Issue 1 , 2017 , Pages 1-9 ; 17554535 (ISSN) Afshang, H ; Tahami, F ; Molla Ahmadian, H ; Sharif University of Technology
    Institution of Engineering and Technology  2017
    Abstract
    Control and stabilisation of the resonant converters are essential problems in power electronics. The conventional model of the dc-dc series resonant converter (SRC) is derived using the sinusoidal approximation and generalised averaging followed by linearisation about an operating point. This model involves considerable approximation and is not applicable for large variation of load and supply voltage. The authors have already proposed a direct piece-wise affine (DPWA) modelling and control approach for the SRC that operates above resonant frequency. However, the DPWA technique is not applicable to an SRC that operates below resonance because of the presence of harmonics. In this study, a... 

    The direct piece-wise affine modeling of llc resonant converter

    , Article 45th Annual Conference of the IEEE Industrial Electronics Society, IECON 2019, 14 October 2019 through 17 October 2019 ; Volume 2019-October , 2019 , Pages 2062-2067 ; 9781728148786 (ISBN) Barzkar, A ; Tahami, F ; Molla Ahmadian, H ; Sharif University of Technology
    IEEE Computer Society  2019
    Abstract
    Resonant converters are hard nonlinear systems which are comprised of both continuous and discontinuous nonlinearities. Many nonlinear modeling approaches lead to a very awkward, unsystematic stability analysis and controller design. Hence, stability analysis and stabilizing controller design of the popular LLC resonant converter still remain challenging as direct consequences of the absence of a "systematic modeling". In this paper, the LLC resonant converter is modeled in the form of Piece-Wise Affine (PWA) systems and a Direct Piece-Wise Affine (DPWA) model of the DC-DC LLC resonant converter is proposed. No dynamic is omitted in the modeling approach, and accordingly, the proposed... 

    Modeling of the boost power factor correction rectifier in mixed conduction mode using PWA approximation

    , Article 2008 IEEE International Symposium on Industrial Electronics, ISIE 2008, Cambridge, 30 June 2008 through 2 July 2008 ; 2008 , Pages 190-195 ; 1424416655 (ISBN); 9781424416653 (ISBN) Tahami, F ; Gholami, B ; Ahmadian, H. M ; Sharif University of Technology
    2008
    Abstract
    PFC converters for higher power are commonly designed for continuous conduction mode (CCM). However, at light load, discontinuous conduction mode (DCM) will appear close to the crossover of the line voltage, causing the converter to switch between the two conduction modes. As a result, the converter dynamics change abruptly, producing input current distortion. In this article a piecewise affine approximation has been employed in modeling a boost power factor correction converter operated in the mixed conduction mode. This approach makes the new model very useful in large signal analysis of PFC rectifiers and design of controller. The results obtained from the proposed model are compared with... 

    Robust H∞ control design for PFC rectifiers

    , Article 7th International Conference on Power Electronics and Drive Systems, PEDS 2007, Bangkok, 27 November 2007 through 30 November 2007 ; 2007 , Pages 948-952 ; 1424406455 (ISBN); 9781424406456 (ISBN) Tahami, F ; Molla Ahmadian, H ; Moallem, A ; Sharif University of Technology
    2007
    Abstract
    Power factor correction (PFC) converter circuits are non-linear system due to the contribution of their multiplier. This non-linearity reflects the difficulty of analysis and design. Models that reduce the system to a linear system involve considerable approximation, and produce results that are susceptible to instability problems. Our goal is to design a controller that achieves some performance specifications despite these uncertainties in modeling. This paper addresses a robust H∞ control problem for switched circuits with parameter uncertainties. The necessary and sufficient conditions for existence of strong robust H∞ dynamic compensators and static output feedback controllers are... 

    A novel hybrid modeling of DC-DC series resonant converters

    , Article IECON Proceedings (Industrial Electronics Conference) ; 2013 , Pages 280-286 ; 9781479902248 (ISBN) Afshang, H ; Tahami, F ; Molla Ahmadian, H ; The Institute of Electrical and Electronics Engineers (IEEE); IEEE Industrial Electronics Society (IES); Austrian Institute of Technology (AIT); Vienna University of Technology (TU Vienna) ; Sharif University of Technology
    2013
    Abstract
    The subject of modeling and stability analysis of dc-dc resonant converters is still a challenge. The conventional large signal nonlinear model of the resonant converter is derived using the sinusoidal approximation and averaging followed by linearization about an operating point. Models obtained with such method involve considerable approximation, and produce results that are limited for higher performance designs. Therefore, it is essential to investigate the stability of the resonant converters using a more sophisticated model. Because of semiconductors switching, dc-dc resonant converters are intrinsically hybrid systems consist of discrete input and continuous states. The complexity of...