Capacitor Voltage Estimation Scheme with Reduced Number of Sensors for Modular Multilevel Converters

Osama Sh. Mohamed Abushafa, Shady Gadoue, Mohamed S. A. Dahidah, David Atkinson, Petros Missailidis

Research output: Contribution to journalArticlepeer-review


This paper presents a new method to measure the voltage across the submodule (SM) capacitors in a modular multilevel converter (MMC). The proposed technique requires only one voltage sensor per arm. This reduces the number of sensors required compared to conventional sensor-based methods. Therefore, the cost and complexity of the system are reduced, which in turn improves the converter’s overall reliability. The proposed method employs an exponentially weighted recursive least square (ERLS) algorithm to estimate the SM capacitor voltages through the measured total arm voltage and the switching patterns of each SM. There is thus no need for extra sensors to measure these control signals as they are directly provided from the controller. The robustness of the proposed method is confirmed via introducing deviations for the capacitance values, dynamic load changes, DC voltage change and start-up transient condition. Simulation and experimentally validated results based on a single-phase MMC show the effectiveness of the proposed method in both, steady-state and dynamic operations.
Original languageEnglish
Pages (from-to)2086-2097
Number of pages12
JournalIEEE Journal of Emerging and Selected Topics in Power Electronics
Issue number4
Early online date24 Jan 2018
Publication statusPublished - 1 Dec 2018

Bibliographical note

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Funding: Libyan Ministry of Higher Education and Scientific
Research and Scholar Program of Zawia and Sabratha


  • Modular multilevel converter (MMC)
  • reduced number of sensors
  • pulse width modulation (PWM)
  • recursive least square (RLS)
  • voltage balancing control algorithm


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