EPE Association: EPE 2013 - LS7c: High Power Multi-Level Converters

EPE 2013 - LS7c: High Power Multi-Level Converters
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2013 ECCE Europe - Conference > EPE 2013 - Topic 05: Hard switching converters and control > EPE 2013 - LS7c: High Power Multi-Level Converters

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   Capacitance and Inductance Selection of the Modular Multilevel Converter
By Marcin ZYGMANOWSKI, Boguslaw GRZESIK, Radoslaw NALEPA [View]
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Abstract: The paper presents a proposal for capacitance and inductance selection procedure of the modularmultilevel converter. Two analysis criteria are taken into consideration, the circulating current andvoltage ripple across submodule capacitors. Results are obtained numerically by using the converteraveraged model based on state equations. In the modular multilevel converter operating under a directmodulation method, based on sinusoidal modulating signals, circulating currents flows through theconverter arms. These currents are strongly dependant on the component parameters of the converter,such as: submodule DC-link capacitor capacitance and arm inductor inductance. Both componentsform a series resonance circuit in each converter arm. Resonance that occurs in the converter arm hasto be avoided and therefore it is important to properly select component parameters while taking intoaccount all possible resonances. Such components selection should be carried out at an early stage ofthe converter design.

   Global stability of modular multilevel converters with measurement lag and circulating-current control
By Lennart HARNEFORS, Antonios ANTONOPOULOS, Hans-Peter NEE [View]
[Download]

Abstract: In this paper, previously developed stability results for open-loop sum-capacitor-voltage control of modular multilevel converters are extended. To obtain improved damping, circulating-current feedback is included in the control law. A first-order measurement lag is added to this feedback. With these additions, global asymptotic stability is proven. Careful consideration of the online control-law computation is given, since this is the most critical part of the control system. Experimental results verify the theory.

   On Energy Variations in Modular Multilevel Converters with Full-Bridge Submodules for Ac-Dc and Ac-Ac Applications
By Kalle ILVES, Staffan NORRGA, Hans-Peter NEE [View]
[Download]

Abstract: The modular multilevel converter is a promising topology for high-voltage high-power applications. Bythe series-connection of submodules it can generate high-quality voltage waveforms with low harmonicdistortion at low switching frequencies. The submodules are low-voltage converters with capacitiveenergy storages. These capacitive energy storages are a driving factor of the size, weight, and cost of theconverter. For this reason it is important to ensure that the stored energy in the converter is distributedas evenly among the submodules as possible. In this paper it is found that during nominal operatingconditions, a large amount of energy is moved back and forth between the upper and lower arms inthe converter. These energy oscillations can, however, be reduced or even eliminated if an appropriatemodulation index or voltage ratio is used. It is also found that an appropriate modulation index or voltageratio can reduce the power rating of the semiconductors as well. The theoretical findings are validatedby simulating two systems with different voltage ratios for ac-ac conversion.

EPE 2013 - LS7c: High Power Multi-Level Converters
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2013 ECCE Europe - Conference > EPE 2013 - Topic 05: Hard switching converters and control > EPE 2013 - LS7c: High Power Multi-Level Converters
	[return to parent folder]

	Capacitance and Inductance Selection of the Modular Multilevel Converter By Marcin ZYGMANOWSKI, Boguslaw GRZESIK, Radoslaw NALEPA	[View] [Download]
Abstract: The paper presents a proposal for capacitance and inductance selection procedure of the modularmultilevel converter. Two analysis criteria are taken into consideration, the circulating current andvoltage ripple across submodule capacitors. Results are obtained numerically by using the converteraveraged model based on state equations. In the modular multilevel converter operating under a directmodulation method, based on sinusoidal modulating signals, circulating currents flows through theconverter arms. These currents are strongly dependant on the component parameters of the converter,such as: submodule DC-link capacitor capacitance and arm inductor inductance. Both componentsform a series resonance circuit in each converter arm. Resonance that occurs in the converter arm hasto be avoided and therefore it is important to properly select component parameters while taking intoaccount all possible resonances. Such components selection should be carried out at an early stage ofthe converter design.

	Global stability of modular multilevel converters with measurement lag and circulating-current control By Lennart HARNEFORS, Antonios ANTONOPOULOS, Hans-Peter NEE	[View] [Download]
Abstract: In this paper, previously developed stability results for open-loop sum-capacitor-voltage control of modular multilevel converters are extended. To obtain improved damping, circulating-current feedback is included in the control law. A first-order measurement lag is added to this feedback. With these additions, global asymptotic stability is proven. Careful consideration of the online control-law computation is given, since this is the most critical part of the control system. Experimental results verify the theory.

	On Energy Variations in Modular Multilevel Converters with Full-Bridge Submodules for Ac-Dc and Ac-Ac Applications By Kalle ILVES, Staffan NORRGA, Hans-Peter NEE	[View] [Download]
Abstract: The modular multilevel converter is a promising topology for high-voltage high-power applications. Bythe series-connection of submodules it can generate high-quality voltage waveforms with low harmonicdistortion at low switching frequencies. The submodules are low-voltage converters with capacitiveenergy storages. These capacitive energy storages are a driving factor of the size, weight, and cost of theconverter. For this reason it is important to ensure that the stored energy in the converter is distributedas evenly among the submodules as possible. In this paper it is found that during nominal operatingconditions, a large amount of energy is moved back and forth between the upper and lower arms inthe converter. These energy oscillations can, however, be reduced or even eliminated if an appropriatemodulation index or voltage ratio is used. It is also found that an appropriate modulation index or voltageratio can reduce the power rating of the semiconductors as well. The theoretical findings are validatedby simulating two systems with different voltage ratios for ac-ac conversion.