Design and control of modular multilevel alternate arm converter (AAC) with Zero Current Switching of director switches

Najmi, Vahid; Burgos, Rolando; Boroyevich, Dushan

doi:10.1109/ecce.2015.7310610

Cited by 28 publications

(34 citation statements)

References 25 publications

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“…On the basis of Mitcheson et al [13] and Farr et al [30], the 'sweet spot' voltage is attained by selecting the turns ratio of the power transformer between the AAC and AC grid accordingly. The derivation of the 'sweet spot' voltage is also presented in [4,12,13,15,22]. The 'sweet spot' voltage method is employed in [21,[41][42][43] to achieve energy balance between the upper and lower arms of the AAC.…”

Section: 'Sweet Spot' Voltagementioning

confidence: 99%

Arm energy balancing control in AACs: a comparative analysis

Leow

Ooi

2020

IET Power Electronics

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The alternate arm converter (AAC) is an emerging state-of-the-art topology for voltage-source converter (VSC) by combining two-level converter and modular multilevel converter (MMC). The AAC performs better than the MMC in terms of the ability to block DC-side faults and ride through AC-side faults. Moreover, the number of sub-modules (SMs) per arm of the AAC is reduced by about 50% compared with the MMC. The key issue with AAC is the energy deviation during the alternate operation between the upper and lower arms. Presently, several AAC balancing techniques have been proposed, but no comparative analysis has been performed to provide insight on the effect of each balancing technique on AAC performance. In this study, five proposed balancing techniques are reviewed accordingly, followed by comparing them in terms of four parameters-the presence of DC filter, balancing capability, the presence of redundant SMs and zero-current switching control. Furthermore, a simulation work has been performed to study and compare the effects of each of the five balancing techniques. Both literature and simulation-based comparative analysis are significant to help select appropriate balancing technique as well as to provide helpful insights to improve the existing balancing techniques.

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Section: 'Sweet Spot' Voltagementioning

confidence: 99%

Arm energy balancing control in AACs: a comparative analysis

Leow

Ooi

2020

IET Power Electronics

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“…Due to the AAC discontinuous operations, the energy is only controllable during the Overlap period. This specificity inherent to the AAC induces modifications on the basic stored energy model obtained in (17). Indeed, as explained in Section 2.1, even though i di f f j cannot be handled all along the grid current, this current, which is purely mathematical, is not null when the phase returns to its Non-overlap mode.…”

Section: Stored Energy Control Designmentioning

confidence: 99%

“…For both improved energy efficiency and safety reasons, the DSs should be zero-current soft switched, especially as they are in the direct conduction path of the arm and grid inductors. This issue is assessed in [16,17].…”

mentioning

confidence: 99%

Energy and director switches commutation controls for the alternate arm converter

Vermeersch

Gruson

Guillaud

et al. 2019

Mathematics and Computers in Simulation

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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. This is an author-deposited version published in: https://sam.ensam.eu Handle IDAbstract The Alternate Arm Converter (AAC) is promising multilevel Voltage Source Converter (VSC) suitable for High Voltage Direct Current (HVDC) transmission systems. This converter exhibits interesting features such as a DC Fault Ride Through capability thanks to the use of Full-Bridge Sub-Modules (SM) and a smaller footprint than an equivalent Modular Multilevel Converter (MMC).After an analysis of the converter operating modes called Non-overlap and Overlap mode, a sequential representation of the AAC operation is proposed. The main originality of this paper is the use of the Petri Net to describe all the phases and to highlight their sequencing. According to the phases identified thanks to the sequential approach, models and control structures for the grid currents, the internal energy and the Zero Current Switching (ZCS) are detailed. Furthermore, the step-by-step approach proposed in this paper allows a clear and rigorous modelling of this complex converter.

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“…This type of controller exists only in AAC converters, and regulates the period during which both arms conduct simultaneously. Although different implementations of overlap angle control, such as average energy and current-based control, exist [23,24],such implementations may be inadequate if hardware delays are also considered. In the utilised models, therefore, fixed overlap angles (which are dependent upon modulation index) are adopted, as shown in Fig.…”

Section: Overlap Angle Controller (Aac)mentioning

confidence: 99%

“…40 kJ/MW [29,30].) The AAC arm inductance should be sufficient to enable the arm current to be transferred between arms during overlap, while providing a degree of current filtering [23]. In MMC the arm inductance (or accumulated DC side inductance [31]) can act as a filter for the circulating currents and to prolong current rise time in the event of a DC-side fault.…”

Section: Passive Components Sizingmentioning

confidence: 99%

Steady-state performance of state-of-the-art modular multilevel and alternate arm converters with DC fault-blocking capability

Vozikis¹,

Adam²,

Rault

et al. 2018

International Journal of Electrical Power & Energy Systems

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This paper presents a comparison of the steady-state behaviour of four state-of-the-art HVDC converters with DC fault-blocking capability, based on the modular multilevel and alternate arm converter topologies.AC and DC power quality, and semiconductor losses are compared, whilst considering different operating conditions and design parameters, such as the number of cells and component sizing. Such comparative studies have been performed using high-fidelity converter models which include detailed representation of the control systems, and of the converter thermal circuit. The main findings of this comprehensive comparison reveal that, the mixed cell modular converter offers the best design trade-off in terms of power losses and quality, and control range. Moreover, it has been established that the modular converter with a reduced number of cells per arm and with each cell rated at high voltage (i.e. 10-20 kV), tends to exhibit higher switching losses and relatively poor power quality at the DC side.

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Design and control of modular multilevel alternate arm converter (AAC) with Zero Current Switching of director switches

Cited by 28 publications

References 25 publications

Arm energy balancing control in AACs: a comparative analysis

Arm energy balancing control in AACs: a comparative analysis

Energy and director switches commutation controls for the alternate arm converter

Steady-state performance of state-of-the-art modular multilevel and alternate arm converters with DC fault-blocking capability

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