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Primary Droop Current-Sharing Control of the Parallel DC/DC Converters System considering Output Cable Resistance  [PDF]
J. B. Wang
Advances in Power Electronics , 2011, DOI: 10.1155/2011/713250
Abstract: This paper presents a primary droop current-sharing controller that can integrate into voltage feedback controller and, thus, provides a low-cost and simple solution for parallel DC/DC converters system. From the equivalent small-signal model, a two-port network was adapted to describe the output and control variables for designing voltage and droop current-sharing loops. From the analysis results, the designed primary droop current-sharing controller will not affect the original voltage loop gain profile to let the DC/DC converter preserve desire control performance. After designing a stable DC/DC converter with primary droop current-sharing control, the stability of the interconnected parallel DC/DC converters system was studied. When the cable resistance is reduced, when the cable resistance is reduced, the interconnected system might be unstable. Finally, some simulation and experimental results demonstrated the effectiveness of the proposed controller in a prototype parallel DC/DC converters system. 1. Introduction In general, the server power system infrastructure consists of frond end AC/DC converters to build up high DC voltage and DC/DC converters to provide power to downstream load. The AC/DC converter uses power factor correction control to let the input line current meet the current harmonic specification; furthermore, the second-stage DC/DC converters and the interconnected cables construct a DC-distributed power system. A DC power system consists of many standard DC/DC converters through interconnected cables or copper buses in series or parallel to obtain desire output voltage, current, and power [1–4]. The structures of the interconnected DC power system have four topologies, that is, input series output series, input series output parallel, input parallel output series, and input parallel output series [2, 4]. The series structure can obtain high output voltage or withstand high input voltage; the kernel of the control strategy is to achieve voltage balance operation among the DC/DC converters. As to the parallel operation, high output current is the major advantage. However, the equal current-sharing control among each of DC/DC converters is the key performance index. In the server power system infrastructure, the parallel DC/DC converters system plays the key role to provide low voltage and high output current capability through the delicate designed interconnected system. In order to obtain equal current-sharing control in the parallel DC/DC converters system, the current-sharing control should be designed. The most prevailing
Direct Sensitivity Analysis of the DC-to-DC Converters
Elena Niculescu,Eugen Iancu,Dorina Mioara-Purcaru,Marius-Cristian Niculescu
Journal of Electrical and Electronics Engineering , 2009,
Abstract: The mathematical principle of the directsensitivity analysis of the dynamic systems and itsapplication to the DC-to-DC PWM converters arepresented. The model of the dynamic system associatedto the PWM Sepic converter with parasitic includedand continuous conduction mode (CCM), and coupledinductors was used in this study. The modelling of theconverter and the state sensitivity analysis with respectto some parameters of the converter have beenperformed with MATLAB environment. The algorithmcarried out for computing the state sensitivity functionsof converter can be applied to other configurations ofDC-to-DC PWM converters, for the two operatingmodes (CCM and DCM), with parasitic included andwith coupled or separate inductors, regardless ofsystem order.
Comparison of PID and Fuzzy Controlled DC to DC Converter with Inductor Resistance.  [PDF]
R.Anand,P.Melba Mary
International Journal of Engineering Sciences & Research Technology , 2013,
Abstract: The DC-DC boost converter reveals highly non-linear and non-minimum phase properties, is very difficult task to design a controller that is healthy against load variation. For this purpose a Fuzzy PID Controller is proposed to control DC-DC boost converter which has a practical inductor and a series resistance. A balancing ProportionalIntegral-Differential (PID) controller to the parallel-damped passivity-based controller PD-PBC is also proposed for removing the steady state error even though the parasitic resistance. MATLAB simulations are performed under step changes and load perturbations to measure the improvement in performance of the proposed approach.
Extra-High-Voltage DC-DC Boost Converters Topology with Simple Control Strategy  [PDF]
P. Sanjeevikumar,K. Rajambal
Modelling and Simulation in Engineering , 2008, DOI: 10.1155/2008/593042
Abstract: This paper presents the topology of operating DC-DC buck converter in boost mode for extra-high-voltage applications. Traditional DC-DC boost converters are used in high-voltage applications, but they are not economical due to the limited output voltage, efficiency and they require two sensors with complex control algorithm. Moreover, due to the effect of parasitic elements the output voltage and power transfer efficiency of DC-DC converters are limited. These limitations are overcome by using the voltage lift technique, opens a good way to improve the performance characteristics of DC-DC converter. The technique is applied to DC-DC converter and a simplified control algorithm in this paper. The performance of the controller is studied for both line and load disturbances. These converters perform positive DC-DC voltage increasing conversion with high power density, high efficiency, low cost in simple structure, small ripples, and wide range of control. Simulation results along theoretical analysis are provided to verify its performance.
HYBRID MODELING OF OPEN LOOP DC-DC CONVERTERS
Zulueta,Ekaitz; Rico,Teodoro; González de Durana,José María;
Revista Facultad de Ingeniería - Universidad de Tarapacá , 2003, DOI: 10.4067/S0718-13372003000200007
Abstract: power electronic converters always have been circuits of difficult modelling because differential equations that describe them have discontinuities. although this situation has been improved since the appearance of the hybrid systems theory, able to jointly describe both continuous and discrete behaviors exhibited by some physical systems, nowadays it is possible to obtain very precise models which help us in the study and design of such circuits. an excellent option for the discrete part model (reactive system) is to use statecharts, since this powerful language has recently been implemented and named stateflow as a part of the simulink toolbox of matlab. so, today, the complete modeling of some hybrid systems within matlab environment is possible. in this work the open loop hybrid modeling and simulation of the well-known dc-dc converters named buck and boost, using matlab-simulink-stateflow, is presented
HYBRID MODELING OF OPEN LOOP DC-DC CONVERTERS  [cached]
Ekaitz Zulueta,Teodoro Rico,José María González de Durana
Revista Facultad de Ingeniería - Universidad de Tarapacá , 2003,
Abstract: Power electronic converters always have been circuits of difficult modelling because differential equations that describe them have discontinuities. Although this situation has been improved since the appearance of the Hybrid Systems theory, able to jointly describe both continuous and discrete behaviors exhibited by some physical systems, nowadays it is possible to obtain very precise models which help us in the study and design of such circuits. An excellent option for the discrete part model (reactive system) is to use statecharts, since this powerful language has recently been implemented and named Stateflow as a part of the Simulink toolbox of Matlab. So, today, the complete modeling of some hybrid systems within Matlab environment is possible. In this work the open loop hybrid modeling and simulation of the well-known dc-dc converters named buck and boost, using Matlab-Simulink-Stateflow, is presented
Local Bifurcations in DC-DC Converters  [PDF]
Chung-Chieh Fang,Eyad H. Abed
Computer Science , 2012,
Abstract: Three local bifurcations in DC-DC converters are reviewed. They are period-doubling bifurcation, saddle-node bifurcation, and Neimark bifurcation. A general sampled-data model is employed to study the types of loss of stability of the nominal (periodic) solution and their connection with local bifurcations. More accurate prediction of instability and bifurcation than using the averaging approach is obtained. Examples of bifurcations associated with instabilities in DC-DC converters are given.
Stability of Interconnected DC Converters  [PDF]
Gustavo Cezar,Ram Rajagopal,Baosen Zhang
Mathematics , 2015,
Abstract: This paper addresses stability issues of DC networks with constant power loads (CPL). Common DC networks, such as automotive electrical systems and DC microgrids, typically have a step-up/down converter connected in one side to the main bus and, on the other, to the load. When load is constant power it can generate destabilizing effects if not proper controlled. This paper shows that converters driving CPLs can make the system unstable, even if they are individually stable, depending on network parameters. We mitigate this problem by means of passive components externally connected to the converter/CPL subsystem. The analysis is verified through simulations. We are able to show that certain converter circuit configurations achieve the so called plug-and-play property, which stabilizes the interconnected system for all network parameters. This property is desirable since it is does not require the knowledge of detailed system topology and parameters, which can be time varying and difficult to obtain. This method also contrasts to existing practices of load augmentation, which can lead to severe efficiency losses.
Step-Up DC/DC Converters with the Tristate Quasi-Z-Source Network  [PDF]
S. Diwahar,S. Surjith Barnala,N. Vikneswaran,M. Gurunathan
International Journal of Advanced Electrical and Electronics Engineering , 2013,
Abstract: This paper presents the Step-Up DC/DC Converters With The Tristate quasi- Z-Source Network. This paper is based on the step-up dc/dc converter family with a cascaded quasi-Z-source network. The tri-stage network could be derived by adding of one diode, one inductor, and two capacitors to the two quasi-Z-source inverter. It has advantages of Voltage boost and buck functions in a single stage, continuous input current and improved reliability. Theoretical analysis of the tri-stage quasi Z-Source network in the shoot-through and non-shoot-through operating modes is described. To further decrease the shoot-through duty cycle at the same voltage boost factor, the number of stages of the quasi Z-Source-network could be increased.
Modeling the Bi-directional DC-DC Converter for HEV's
Chongwu Wang,Xiangzhong Meng,Xiaowei Guo
Modern Applied Science , 2009, DOI: 10.5539/mas.v1n4p87
Abstract: Hybrid Electrical Vehicles-HEV!?s are the importnt ways to improve vehicle performance. The transformer isolated bi-directional DC-DC converters are the key components of the traction system in HEV!?s. This paper presents adetail mathematic model of isolated bi-directional DC-DC converter for HEV!?s. Approximate models are important mathematic methods especially for analysis and closed-loop control design converter circuits. These differential equations, which govern the converter operation, change periodically among a set of linear differential equations because of the switch effect. Basing on the time-scale the state variables was separate as fast-scale and slow-scale variables. The fast changing variable of the leakage inductor was eliminated by substitute the fast-scale variable into slow-scale variable equations, resulting in reduced order differential equations. From this set of reduced order differential equations the completely averaged model of the isolated DC/DC converter was derived. The simulated results reveal that the circuit and mathematical model are consistent very well. The averaged state variables can be treated as a small component plus a DC component, so the averaged model can be separated a dynamic small signal part and a DC part. This linearized small signal model is suit for control design and analysis at a steady point that is decided by the DC component. As an example a PI controller was design basing on the linear model.
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