Impedance interactions in bidirectional cascaded converter

Tian, Yanjun; Loh, Poh Chiang; Chen, Zhe; Deng, Fujin; Hu, Yuxin

doi:10.1049/iet-pel.2015.0559

Cited by 21 publications

(13 citation statements)

References 40 publications

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“…Despite the above merits, the DAB-based two-stage converter suffers from unstable problems. Similar instability issues have also been reported in [7]- [9]. The stability criteria for unidirectional two-stage converters have been proposed in [10]- [12].…”

Section: Introductionsupporting

confidence: 64%

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Impedance Shaping of Isolated Two-Stage AC-DC-DC Converter for Stability Improvement

Fan

Gooi

2019

IEEE Access

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The isolated two-stage ac-dc-dc converter containing an isolated dual-active-bridge (DAB) dc-dc converter and an ac-dc rectifier has been widely used for connecting the dc sources to the ac utility grid. However, the impedance interaction between the DAB converter and the ac-dc rectifier may cause the instability problem. To address this issue, this paper proposes two control methods to reshape the impedances of the isolated two-stage ac-dc-dc converter by building a virtual impedance connected in parallel or series with the input impedance of the DAB converter. The magnitude of the input impedance of the DAB converter is increased to satisfy the Middlebrook criterion without changing its negative resistance characteristics by the proposed control methods. Furthermore, the design requirements for the proposed controllers are also given to ensure the stable operation of the two-stage converter. The comparison of these two proposed methods is also discussed in terms of stabilizing ability, dynamic performance, and cost. The comprehensive experimental results are provided to validate the proposed methods. INDEX TERMS Impedance shaping, modeling, stability criterion, two-stage converter.

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Section: Introductionsupporting

confidence: 64%

“…It has been found that the stability of the bidirectional two-stage converter is related to its control strategy. When the power is transferred from the voltage controlled sub-converter to the current controlled sub-converter, the bidirectional two-stage converter may be unstable [9].…”

Section: Introductionmentioning

confidence: 99%

Impedance Shaping of Isolated Two-Stage AC-DC-DC Converter for Stability Improvement

Fan

Gooi

2019

IEEE Access

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“…To study the effects of proposed stabilization, measurements of Z in from the full order nonlinear simulation model have been performed, as commonly done by other researchers as well (see e.g. [46]). As discussed in Section II-B, measurement of frequency responses is a standard approach to study the dynamic behavior of complex nonlinearities for which such response is difficult to analytically calculate (e.g.…”

Section: A Dc-link Stabilitymentioning

confidence: 99%

Dynamic Stabilization of DC Microgrids With Predictive Control of Point-of-Load Converters

Dragičević

2018

IEEE Trans. Power Electron.

146

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This paper investigates the possibility of deploying a finite control set model predictive control (FCS-MPC) algorithm for dynamic stabilization of a dc microgrid that supplies tightly regulated point-of-load (POL) converters. Within their control bandwidth, such converters behave as constant power loads (CPLs), where the microgrid sees them as impedances with a negative incremental resistance. Due to this characteristic, POL converters have a destabilizing impact which may cause large voltage oscillations or even a blackout of the whole microgrid. This paper proposes an active damping method realized by introducing a stabilization term in the cost function of the FCS-MPC algorithm that is used for regulation of the POL converter. This approach, on one hand, stabilizes a dc microgrid without implementing any additional active or passive components, thus providing higher energy efficiency and better cost-effectiveness than methods which rely on such components. On the other hand, when compared to other approaches that focus on dc link stabilization via POL converter control, the proposed method has a significantly lower influence on the load voltage regulation performance. These findings are confirmed through comprehensive analytical investigation that shows how the proposed stabilization term affects the input impedance of the POL converter and the load voltage tracking performance. This is followed by experimental validation, where an FCS-MPC regulated UPS inverter was used as a particular CPL example. Index Terms-Finite control set model predictive control (FCS-MPC), constant power load (CPL), dc microgrid (MG), stability, impedance analysis.

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“…But the implementation of the method in [18][19] is complicated. In [20], the DC impedance characteristics of the dual active bridge (DAB) Inverter cascaded system were analyzed, and the impedance interaction between DAB and the inverter, caused by different power flow directions, may result in instability in the cascaded system. Similarly, in [21], a DC-AC cascaded system was used as a topology to study the effects of bidirectional power flow on DC impedance characteristics.…”

Section: Introductionmentioning

confidence: 99%

DC‐side current compensation control in the rectifier terminal for power variations in back‐to‐back converters

Jiang

Tian

et al. 2021

IET Renewable Power Gen

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Back-to-back (BTB) converters, which consist of an AC/DC rectifier cascaded with a DC/AC inverter, have been widely adopted in the interconnection of power systems. The DC link, being the interface between the rectifier and inverter terminals, is susceptible to disturbances, particularly from power fluctuations. Regardless of the magnitude of power or changes in the power flow direction, stability degradation will occur. To lessen the influence of power, a DC-link current compensation control scheme is proposed and applied to the rectifier terminal. The proposed scheme reduces the DC link impedance gain of the rectifier terminal to balance the impedance at both ends, and thus enhance stability and controllability. The scheme is applied to a BTB converter to improve the system's resistance to disturbance, regardless of variations in power magnitude or power flow direction. The accuracy of the theoretical analysis and the effectiveness of the proposed scheme are verified using simulations and a scaled-down experimental setup.

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Impedance interactions in bidirectional cascaded converter

Cited by 21 publications

References 40 publications

Impedance Shaping of Isolated Two-Stage AC-DC-DC Converter for Stability Improvement

Impedance Shaping of Isolated Two-Stage AC-DC-DC Converter for Stability Improvement

Dynamic Stabilization of DC Microgrids With Predictive Control of Point-of-Load Converters

DC‐side current compensation control in the rectifier terminal for power variations in back‐to‐back converters

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