Capacitor Voltage Balancing of a Grid-Tied, Cascaded Multilevel Converter with Binary Asymmetric Voltage Levels Using an Optimal One-Step-Ahead Switching-State Combination Approach

Manuel Kuder, Anton Kersten, Jose-Luis Marques-Lopez, Julian Estaller, Johannes Buberger, Florian Schwitzgebel, Torbjörn Thiringer, Anton Lesnicar, Rainer Marquardt, Thomas Weyh and Richard Eckerle
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Manuel Kuder: Department of Electrical Engineering, Bundeswehr University Munich, Werner-Heisenberg-Weg 39, 85579 Neubiberg, Germany
Anton Kersten: Department of Electrical Engineering, Bundeswehr University Munich, Werner-Heisenberg-Weg 39, 85579 Neubiberg, Germany
Jose-Luis Marques-Lopez: Department of Electrical Engineering, Bundeswehr University Munich, Werner-Heisenberg-Weg 39, 85579 Neubiberg, Germany
Julian Estaller: Department of Electrical Engineering, Bundeswehr University Munich, Werner-Heisenberg-Weg 39, 85579 Neubiberg, Germany
Johannes Buberger: Department of Electrical Engineering, Bundeswehr University Munich, Werner-Heisenberg-Weg 39, 85579 Neubiberg, Germany
Florian Schwitzgebel: Department of Electrical Engineering, Bundeswehr University Munich, Werner-Heisenberg-Weg 39, 85579 Neubiberg, Germany
Torbjörn Thiringer: Department of Electrical Engineering, Chalmers University of Technology, Hörsalsvägen 11, 41258 Gothenburg, Sweden
Anton Lesnicar: Department of Electrical Engineering, Bundeswehr University Munich, Werner-Heisenberg-Weg 39, 85579 Neubiberg, Germany
Rainer Marquardt: Department of Electrical Engineering, Bundeswehr University Munich, Werner-Heisenberg-Weg 39, 85579 Neubiberg, Germany
Thomas Weyh: Department of Electrical Engineering, Bundeswehr University Munich, Werner-Heisenberg-Weg 39, 85579 Neubiberg, Germany
Richard Eckerle: Department of Electrical Engineering, Bundeswehr University Munich, Werner-Heisenberg-Weg 39, 85579 Neubiberg, Germany

Energies, 2022, vol. 15, issue 2, 1-19

Abstract: This paper presents a novel capacitor voltage balancing control approach for cascaded multilevel inverters with an arbitrary number of series-connected H-Bridge modules (floating capacitor modules) with asymmetric voltages, tiered by a factor of two (binary asymmetric). Using a nearest-level reference waveform, the balancing approach uses a one-step-ahead approach to find the optimal switching-state combination among all redundant switching-state combinations to balance the capacitor voltages as quickly as possible. Moreover, using a Lyapunov function candidate and considering LaSalle’s invariance principle, it is shown that an offline calculated trajectory of optimal switching-state combinations for each discrete output voltage level can be used to operate (asymptotically stable) the inverter without measuring any of the capacitor voltages, achieving a novel sensorless control as well. To verify the stability of the one-step-ahead balancing approach and its sensorless variant, a demonstrator inverter with 33 levels is operated in grid-tied mode. For the chosen 33-level converter, the NPC main-stage and the individual H-bridge modules are operated with an individual switching frequency of about 1 kHz and 2 kHz, respectively. The sensorless approach slightly reduced the dynamic system response and, furthermore, the current THD for the chosen operating point was increased from 3.28 to 4.58 in comparison with that of using the capacitor voltage feedback.

Keywords: modular multilevel converters; multilevel systems; power supplies; sensorless control; total harmonic distortion (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
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