Investigation and Compensation of Circulating Current Errors in Low Frequency Operation of Modular Multilevel Converters

Sabbagh, Muneer Al; Pan, Jianyu; Ke, Ziwei; Xu, Longya

doi:10.1109/ecce.2018.8558193

Cited by 4 publications

(5 citation statements)

References 12 publications

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“…The existence of p err pa causes voltage fluctuations v err cpa in MMC capacitors. These fluctuations are governed by the differential equation [5], [15] dv err cpa dt = 1 4C…”

Section: B Definition and Effects Of Circulating Current Errorsmentioning

confidence: 99%

“…(1 − α cos θ) i oa (11) where C is the submodule capacitance. Both α and θ change continuously during operation [15], so obtaining an analytical solution to (11) is not possible. However, it has been demonstrated that the frequency of v err cpa fluctuations is equal to f o [15].…”

Section: B Definition and Effects Of Circulating Current Errorsmentioning

confidence: 99%

“…To simplify the technique proposed in [14], we proved in [15] that the same objective can be achieved by only one additional parameter in the circulating current reference instead of two. As a result, the proposed technique becomes simpler, and is able to enhance the suppression of voltage fluctuations in the MMC capacitors.…”

Section: Introductionmentioning

confidence: 99%

“…This paper is based on our earlier work presented in [14] and [15] with the following additional contributions: (i) The reasons for circulating current errors are explained when the common-mode frequency increases. (ii) A method for computing the circulating current error is introduced and a clear relationship between the error and the compensation parameter is established.…”

Section: Introductionmentioning

confidence: 99%

“…(iii) Improvements in suppressing the voltage fluctuations are analyzed and validated in the time and frequency domains. (iv) Computer simulations for a medium-voltage MMC drive are performed instead of a lowvoltage drive [14], [15]. (v) Experimental results showing a comparison of the old and proposed techniques are added in this paper.…”

Section: Introductionmentioning

confidence: 99%

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Suppressing the Capacitor Voltage Fluctuations in Low Frequency Operation of Modular Multilevel Converters

et al. 2020

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Low frequency operation in the modular multilevel converters (MMCs) is enabled by applying a reference common mode voltage and circulating currents at a frequency much higher than the desired output frequency. The frequency of injected common-mode signals is limited for maintaining a good performance in the circulating current control. Firstly, this paper theoretically analyzes the effect of increasing the frequency of injected common-mode signals by evaluating the error between reference and actual circulating currents. Secondly, we introduce an additional parameter in the reference circulating current to enhance the suppression of MMC's capacitor voltage fluctuations. Intensive computer simulations are developed for a seven-level MMC driving a medium-voltage induction motor drive system to verify the circulating current error analysis and assess the capacitor voltage fluctuations. Finally, the proposed technique for suppressing the capacitor voltage fluctuations is experimentally validated on a 600-V three-level MMC feeding an inductive load. The voltage fluctuations are reduced by more than 50% (63.6%) when the proposed technique is applied with a high common-mode frequency. INDEX TERMS Modular multilevel converter, variable speed drive, low frequency operation, circulating current control.

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“…The existence of p err pa causes voltage fluctuations v err cpa in MMC capacitors. These fluctuations are governed by the differential equation [5], [15] dv err cpa dt = 1 4C…”

Section: B Definition and Effects Of Circulating Current Errorsmentioning

confidence: 99%