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Multilevel Converters

Bauer P., Kazmierkowski M. P., Strzelecki R.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2017

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Vol. 65, nr 5

563--565

EN

The newest Special Section is intended to focus on recent research and trends in application of multilevel converters. Multilevel converters have been extensively developed over the last two decades and show several important advantages of power electronic circuits, such as: operation at high voltages, harmonics reduction, higher efficiency, modularity, smaller size and lower cost. Also, thanks to increasing interest in renewable energy systems (RES) and SGs, the development of multilevel converters is considerably accelerated. The papers included in the presented special section are grouped into the main categories that follow.

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Full-bridge MMC DC fault ride-through and STATCOM operation in multi-terminal HVDC grids

Kontos E., Tsolaridis G., Teodorescu R., Bauer P.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2017

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Vol. 65, nr 5

653--662

EN

This paper investigates a control structure to enhance the DC fault ride-through capability of a full-bridge modular multilevel converter (MMC) station, while ensuring a stable controlled operation as a STATCOM during DC faults without the need for fault isolation. Taking advantage of the switching states of a full-bridge submodule, a DC current controller is proposed, which provides the DC voltage reference for the modulation when a DC fault is detected. By changing the outer controllers strategy from DC voltage or active power control to converter energy control during a fault, the decoupling of the converter operation from the DC side dynamics is realized. In this paper, the focus is on the control methodology at all times of operation and the evaluation of the STATCOM control during a fault. To this end, extensive simulations were performed on a three-terminal high voltage direct current (HVDC) grid in radial configuration and a pole-to-pole DC fault case was investigated. The results showed that the AC voltage and current were controlled within limits at all times, while the full-bridge MMC was able to provide reactive power support to the AC grid. Moreover, using the proposed control methodology, the transients at the operation transition points between STATCOM and inverter/rectifier operation were minimized and the stations were able to safely ride through the fault.

3

Flame Arrester Performance For Rich Methane-Based Mixtures

Bauer P.

Archivum Combustionis

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2002

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Vol. 22 nr 3-4

163-171

EN

Experimental data on the feasibility of a specific static flame arrester are provided in the present study. This type of arrester consists in a series of 2-mm i.d. diameter tubes arranged in a honeycomb type structure. This is aimed at creating a heat sink at the passage of the flame through the tubes. The data are aimed at demonstrating the pertinent use of this type of arrester for the safety in the chemical process industry. Moreover, the experiments were conducted with mixtures of methane-ethane-ethylene more or less diluted in inert, namely, Co2 and Ar mixted in equal proportions. The experimental results show that this device is appropriate for the quenching of a flame or even a detonation in some cases. However, in most cases, the system failed to quench the detonation after a DDT process has occured. These unsuccessful operations of the device occured for flames at a high velocity, namely for Re numbers of the order of 15000.