Operation of modular multilevel matrix converters with failed branches

Karwatzki, Dennis; Hofen, Malte von; Baruschka, Lennart; Mertens, Axel

doi:10.1109/iecon.2014.7048724

Cited by 25 publications

(11 citation statements)

References 16 publications

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“…This feature causes us to use the converter without transformer, and the transformer-less operation; in addition to increase of efficiency, flexibility, scalability, modularity and reliability, this leads to a lower installation and operation costs in a power transmission system. (4) It is shown that the M3C can present the fault tolerance property, i.e., after a branch failure, the nine branch M3C can be reduced to operate as a six-branch Hexverter [44]. Furthermore, the M3C employs inductive elements on both sides and then requires five conducting branches at any instant, which means indeed that the number of under control switches in the performed system is reduced to 80.…”

Section: On Real-world Applicability Of the Proposed Approachmentioning

confidence: 99%

“…Therefore, they can be considered a mature and proven technology. Some reported applications are addressed in [17,[40][41][42][43][44], and M3Cs for these applications are commercially offered by a growing group of companies in the field [45]. (6) The M3C is the only converter system that effectively increases the power rating of the converter.…”

Section: On Real-world Applicability Of the Proposed Approachmentioning

confidence: 99%

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A Novel Control Scheme for Multi-Terminal Low-Frequency AC Electrical Energy Transmission Systems Using Modular Multilevel Matrix Converters and Virtual Synchronous Generator Concept

et al. 2020

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This paper proposes a new control scheme for the low frequency AC transmission (LFAC) system aiming at extending the point-to-point configuration to form a multi-terminal electrical energy network. The multi-terminal low frequency ac (MT-LFAC) system configuration is based on the use of modular multilevel matrix converters (M3Cs) and virtual synchronous generator (VSG) control. The M3C is the next ac/ac converter generation, which is used as an interface with the conventional AC network and the LFAC electrical energy system. Application of VSG control is proposed to enable proper power sharing, to provide synchronization of each terminal, and frequency stabilization, thus, to offer multiterminal forming capability. Two different operation modes are applied in the system to damp the frequency deviation after a dynamic perturbation, which provides additional stabilization feature to the VSG. Frequency restoration mode and commanded mode of power sharing are applied as dynamic states to validate the robustness of the VSG control system. Besides, to solve the negative impact of low X/R ratio in the LFAC electrical energy system, we enhance the VSG control by proposing a virtual-impedance-based solution, which increases the output total impedance on the low frequency side and prevents the coupling between P and Q. The operation of the proposed system is examined by simulation results with a precise model of M3Cs in the PSCAD/ EMTDC software environment (version 4.2.1, Winnipeg, MB, Canada).Energies 2020, 13, 747 2 of 19 delivery. However, neither technology is flawless. For example, the existence of the power electronic switches in the dc circuit breakers make them more vulnerable than the HVAC transmission system, especially when a fault takes place in the converter, due to the low dc-side impedances and sensitive semiconductor power converters [1,2]. On the other hand, the HVAC system offers advantages, such as more reliability of the well-known protection schemes and the change capability of voltage levels using transformers [3]. However, the HVAC transmission system's main disadvantage is the existence of the reactive power in comparison to no reactive power in the HVDC electrical energy system. Due to that, the existence of the reactive power can be translated as losses in the grid [4].The aforementioned points have led to an alternative solution which combines both sets of HVACs and HVDC advantages, known as a low frequency ac (LFAC) transmission system, or a fractional frequency transmission system (FFTS) [5][6][7]. This system transmits the power at a lower frequency range of about 1-60/3 Hz. The LFAC has already been proposed for the offshore wind energy and has offered attractive advantages compared to both transmission solutions. For example, in the HVDC electrical energy system, the implementation of a high capacity dc circuit breaker is difficult due to the absence of the zero crossing points of the DC current [8]. On the other hand, the LFAC system has zero-crossing, thus, the protection is more advantag...

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Section: On Real-world Applicability Of the Proposed Approachmentioning

confidence: 99%

Section: On Real-world Applicability Of the Proposed Approachmentioning

confidence: 99%

A Novel Control Scheme for Multi-Terminal Low-Frequency AC Electrical Energy Transmission Systems Using Modular Multilevel Matrix Converters and Virtual Synchronous Generator Concept

et al. 2020

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“…Additional hardware is incorporated into each cell to bypass the faulty cell. To increase system availability in case a whole cluster is lost, the method proposed in [88] allows operating the M 3 C as a reduced matrix converter utilising six of the remaining clusters to reconfigure it as a Hexverter. This solution requires minimal extra hardware; however, the converter suffers a considerable power capability loss because when a single cluster is lost, two additional healthy clusters need to be symmetrically removed.…”

Section: Fault Tolerance Capabilitymentioning

confidence: 99%

An Overview of Modelling Techniques and Control Strategies for Modular Multilevel Matrix Converters

et al. 2020

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The Modular Multilevel Matrix Converter is a relatively new power converter topology appropriate for high-power Alternating Current (AC) to AC purposes. Several publications in the literature have highlighted the converter capabilities such as modularity, control flexibility, the possibility to include redundancy, and power quality. Nevertheless, the topology and control of this converter are relatively complex to design and implement, considering that the converter has a large number of cells and floating capacitors. Therefore multilayer nested control systems are required to maintain the capacitor voltage of each cell regulated within an acceptable range. There are no other review papers where the modelling, control systems and applications of the Modular Multilevel Matrix Converter are discussed. Hence, this paper aims to facilitate further research by presenting the technology related to the Modular Multilevel Matrix Converter, focusing on a comprehensive revision of the modelling and control strategies.

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“…Similar to BTB-MMC, which can connect two AC systems with different frequencies, modular multilevel direct AC/AC converters have been proposed in recent years. For example, the Modular Multilevel Matrix Converter (MMMC or M 3 C) [2,3], which consists of nine branches, each comprising several series-connected H-bridge submodules and an inductor, is suitable for a 3Φ-to-3Φ AC/AC bidirectional power conversion. In addition, large capacity AC/AC converters are needed in many applications, such as the asynchronous interconnection of different power systems and medium or high voltage motor drives.…”

Section: Introductionmentioning

confidence: 99%

Research on an Asymmetric Fault Control Strategy for an AC/AC System Based on a Modular Multilevel Matrix Converter

Zhang

Liang

2019

Energies

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This paper studies control strategies for an AC/AC system based on a modular multilevel matrix converter (M3C) when an asymmetric fault occurs in the secondary side ac system. Firstly, the operating principle of M3C is briefly introduced and verified by simulation. Then, based on its mathematical model by double αβ0 transformation, the decoupled control strategies for the primary side and secondary side systems are designed. In view of the asymmetric fault condition of the secondary side system, the positive sequence and negative sequence components of voltages and currents are separated and extracted, and then a proportional resonant controller (PR) is used to regulate the positive and negative sequence currents at the same time to realize decoupled current control in the αβ reference frames. The capacitor voltage balancing control, which consists of an inter-subconverter balancing control and an inner-subconverter balancing control, is realized by adjusting four circulating currents. Finally, the proposed control strategy is validated by simulation in the PSCAD/EMTDC software (Manitoba HVDC Research Center, Canada). The result shows that during the period of the BC-phase short-circuit fault occurring in the secondary side system, the whole system can still operate stably and transmit a certain amount of active power, according to their set values. Furthermore, the capacitor voltages are balanced, with a slight increase during the fault period. The simulation results verify the effectiveness of the proposed control strategy.

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Operation of modular multilevel matrix converters with failed branches

Cited by 25 publications

References 16 publications

A Novel Control Scheme for Multi-Terminal Low-Frequency AC Electrical Energy Transmission Systems Using Modular Multilevel Matrix Converters and Virtual Synchronous Generator Concept

A Novel Control Scheme for Multi-Terminal Low-Frequency AC Electrical Energy Transmission Systems Using Modular Multilevel Matrix Converters and Virtual Synchronous Generator Concept

An Overview of Modelling Techniques and Control Strategies for Modular Multilevel Matrix Converters

Research on an Asymmetric Fault Control Strategy for an AC/AC System Based on a Modular Multilevel Matrix Converter

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