Analyzing stability issues in a cascaded converter system comprised of two voltage-mode controlled dc-dc converters

Ahmadi, Reza; Paschedag, Darren; Ferdowsi, Mehdi

doi:10.1109/apec.2011.5744836

Cited by 20 publications

(13 citation statements)

References 10 publications

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“…In the following, a general procedure is being described that combines a two-port converter model featuring one (scalar) control input ctl(t) as given in (2) with a model of the controller according to (3). Firstly, an open-loop model is being constructed, followed by the closed-loop model, both of which maintaining the same interface of the general two-port state-space model (2).…”

Section: Adding Control Loops To Converter Modelsmentioning

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: Adding Control Loops To Converter Modelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Herbst

2019

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“…For instance, a phase margin of 30 • adds 5.8 dB to the output impedance, while a gain margin of 5 dB adds 7.20 dB. Reducing the magnitude of Z o below Z in to ensure stability is mathematically quantifiable because Z in , within the load controller bandwidth, can be described as [40]:…”

Section: Impedance Reshaping For Decoupling the Source-load Interactionmentioning

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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“…The stability problem is one of the intriguing areas for researchers in academia and industry because of its high importance for the reliability of a dc network [5][6][7][8].…”

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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Analyzing stability issues in a cascaded converter system comprised of two voltage-mode controlled dc-dc converters

Cited by 20 publications

References 10 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

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

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

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