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Open-Circuit Fault Diagnosis and Tolerant Control for 2/3-Level DAB Converters | IEEE Journals & Magazine | IEEE Xplore

Open-Circuit Fault Diagnosis and Tolerant Control for 2/3-Level DAB Converters


Abstract:

A two-to-three (2/3)-level dual-active-bridge (DAB) converter is a promising dc–dc converter for medium- and high-voltage applications. That is due to its advantages like...Show More

Abstract:

A two-to-three (2/3)-level dual-active-bridge (DAB) converter is a promising dc–dc converter for medium- and high-voltage applications. That is due to its advantages like high power density, galvanic isolation, and capability of withstanding higher voltage ratings compared to the two-level DAB converters. However, the open-circuit fault (OCF) is critical for the 2/3-level DAB converters, resulting in various negative effects, e.g., dc bias, overshoot current, and capacitor voltage imbalance. To address these issues, it is necessary to develop fault diagnosis and fault-tolerant control strategies. This article, thus, proposes a method to identify the faulty switch based on the dynamic characteristics when the OCF occurs. The midpoint voltages of the neutral-point-clamped bridge arms are employed as the fault diagnosis signals, where the faulty switch can be identified accurately based on the mean values and duty cycles of the midpoint voltages. Subsequently, a fault-tolerant control scheme based on a complementary-switch-blocking method is proposed. In this scheme, when the OCF occurs on one switch, the gate-driving signal of its complementary switch is blocked, and the OCF negative effects, e.g., dc bias, overshoot current, and unbalanced capacitor voltages, can be alleviated significantly. Furthermore, the power transfer capability of the 2/3-level DAB converters is enhanced with the proposed scheme compared to the traditional bypass-arm method. Finally, experimental tests are carried out to verify the theoretical analysis.
Published in: IEEE Transactions on Power Electronics ( Volume: 38, Issue: 4, April 2023)
Page(s): 5392 - 5410
Date of Publication: 30 December 2022

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I. Introduction

The development of the renewable energy generation, uninterruptable power supplies, and energy storage systems has been the major driving force to advance the dc–dc converter technology [1], [2]. In various applications, dc–dc converters generally require simple control, high power density, and high efficiency. More specifically, dual-active-bridge (DAB) dc–dc converters, proposed around 1990s [3], have been applied widely in recent years. Besides their high power density and efficiency, DAB converters have the advantages of inherent soft-switching capability and galvanic isolation [4], [5], [6]. After decades of research, the DAB converters have developed a variety of structures for different applications, such as half-bridge DAB, three-phase DAB, and multilevel DAB converters [7], [8], [9]. Among them, a two-to-three (2/3)-level DAB converter has been proposed to increase the voltage blocking capability of the high-voltage (HV) side [10], [11], [12]. As shown in Fig. 1, the 2/3-level DAB converter is composed of a two-level H-bridge in the low-voltage (LV) side, an isolated transformer, and a three-level neutral-point-clamped (NPC) bridge in the HV side. This structure is suitable for the applications where the rated voltages of the input and output sides are considerably different, e.g., the medium-voltage dc photovoltaic (PV) system, as shown in Fig. 2. Compared with the two-level DAB converters, the 2/3-level DAB converters can achieve higher voltage blocking capability and higher step-up ratio and allow the utilization of lower voltage rating power components, saving the cost to some extent. Furthermore, an increased number of switches provide more degrees of control freedom to further improve the performance of the converters.

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References

References is not available for this document.