Controller design method for a cascaded converter system comprised of two DC-DC converters considering the effects of mutual interactions

Ahmadi, Reza; Ferdowsi, Mehdi

doi:10.1109/apec.2012.6166072

Cited by 21 publications

(9 citation statements)

References 8 publications

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“…For passive components of a converter system, such as an input filter or an electrical load, the two-port state-space model is given in general form in (1). The number of state variables, and therefore the size of the matrices A, B, C depends on the order of the respective system, that is, the number of storage elements.ẋ Figure 1 illustrates the definition of input and output voltages and currents for a generic two-port system.…”

Section: Model For Passive Componentsmentioning

confidence: 99%

“…With no storage elements, there are no dynamics in a resistive system as shown in Figure 12a, which means that A = 0, B = 0, C = 0 hold. Only the D matrix elements of a two-port state-space model according to (1) are present, and one obtains the model (16).…”

Section: A1 Resistive Loadmentioning

confidence: 99%

“…Building and analyzing models for multi-converter configurations has of course been of increasing interest since the advent of DC microgrids [14,15], but has been the subject of research long before, especially when studying converter interactions in a cascaded source-load setup [16,18,23]. Matters of particular interest are impedance analysis [2,4,38], implications for controller design [1,16,25] and, of course, stability [3,18,23]. It has been pointed out [8,36] that studying detailed dynamic interactions between source and load converters is important for stability analysis, going beyond constant power load assumptions.…”

Section: Introductionmentioning

confidence: 99%

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A Building-Block Approach to State-Space Modeling of DC-DC Converter Systems

Herbst

2019

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Small-signal models of DC-DC converters are often based on a statespace averaging approach, from which both control-oriented and other frequencydomain characteristics, such as input or output impedance, can be derived. Updating these models when extending the converter by filters or non-trivial loads, or adding control loops, can become a tedious task, however. To simplify this potentially error-prone process, a modular modeling approach is being proposed in this article. It consists of small state-space models for certain building blocks of a converter system on the one hand, and standardized operations for connecting these subsystem models to an overall converter system model on the other hand. The resulting state-space system model builds upon a two-port converter description and allows the extraction of control-oriented and impedance characteristics at any modeling stage, be it open loop or closed loop, single converter or series connections of converters. The ease of creating more complex models enabled by the proposed approach is also demonstrated with examples comprising multiple control loops or cascaded converters.

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Section: Model For Passive Componentsmentioning

confidence: 99%

Section: A1 Resistive Loadmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Building-Block Approach to State-Space Modeling of DC-DC Converter Systems

Herbst

2019

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“…Therefore, they draw constant power from the grid and exhibit negative incremental impedance property which causes stability issues for the entire system. This has resulted to the formation of a new research area in academia concerning the stability analysis and controller design methods for dc distribution power systems [13][14][15][16][17]. In contrary to conventional control design methods that only consider the stability of individual converters in the dc power system, the new research efforts are focused on the analysis of the converters in the system considering the interactions between them and the network.…”

Section: Introductionmentioning

confidence: 99%

Improving performance of a DC-DC cascaded converter system using an extra feedback loop

Ahmadi

Ferdowsi

2013

2013 IEEE Energy Conversion Congress and Exposition

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This paper introduces the extra feedback method as a technique to improve the performance of a cascaded converter system and stabilize its operation. In this paper, first, the block diagram representation of the small-signal model of a single converter is presented. The open-loop and closed-loop transfer functions of this converter are provided in this stage as well. Next, the presented model is expanded to the block diagram model of a cascaded converter system comprised of two dc-dc converters. Then, the extra feedback method which is the main contribution of the paper is introduced. Some design guidelines for applying this method to an experimental cascaded converter system are provided in this part as well. Finally, some experimental results are provided to verify the theoretical outcomes.

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“…These methods do not typically incur extra power losses; however, some of them reduce the power-density of cascaded systems, such as the solution proposed in [23]. Several noticeable limitations or disadvantages are observed in the proposed solutions in the literature, which can be classified into ensuring stability with poor dynamics (i.e., long settling time) [24], limiting the controller application to a single converter topology (e.g., buck converters) [25,26], and inability to handle multiple converter load systems [27][28][29][30].…”

Section: Introductionmentioning

confidence: 99%

Impedance Decoupling in DC Distributed Systems to Maintain Stability and Dynamic Performance

Etemadi

2017

Energies

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DC distributed systems are highly reliable and efficient means of delivering DC power or adopting renewable energy resources. However, DC distributed systems are prone to instability and dynamic performance degradation due to the negative incremental input impedance of DC-DC converts. In this paper, we propose a generic method to eliminate the impact of the negative input impedance on DC systems by shaping the source output impedance such that its bode-plot is restricted in the area that is contained below the product of the source's duty ratio and its characteristic impedance. The performance deterioration originates whenever the output impedance of the source exceeds, in magnitude, the input impedance of the load converter due to deficiency in stability margins. Hence, confining the impedance in the proposed region helps decouple the interaction between the converters and preserve their own dynamic performances. The proposed method was proven by analytical analysis, time-based simulation, and practical experiments. All of their outcomes were in agreement, proving the effectiveness of the proposed method in preserving the dynamic performance of distributed systems.

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Controller design method for a cascaded converter system comprised of two DC-DC converters considering the effects of mutual interactions

Cited by 21 publications

References 8 publications

A Building-Block Approach to State-Space Modeling of DC-DC Converter Systems

A Building-Block Approach to State-Space Modeling of DC-DC Converter Systems

Improving performance of a DC-DC cascaded converter system using an extra feedback loop

Impedance Decoupling in DC Distributed Systems to Maintain Stability and Dynamic Performance

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