Optimization-Based Capacitor Balancing Method with Selective DC Current Ripple Reduction for CHB Converters

Luis Galván, Pablo Jesús Gómez, Eduardo Galván and Juan Manuel Carrasco
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Luis Galván: Electronical Engineering Department, University of Seville, 41092 Seville, Spain
Pablo Jesús Gómez: Electronical Engineering Department, University of Seville, 41092 Seville, Spain
Eduardo Galván: Electronical Engineering Department, University of Seville, 41092 Seville, Spain
Juan Manuel Carrasco: Electronical Engineering Department, University of Seville, 41092 Seville, Spain

Energies, 2021, vol. 15, issue 1, 1-20

Abstract: From its introduction to the present day, Cascaded H-Bridge multilevel converters were employed on numerous applications. However, their floating capacitor, while advantageous for some applications (such as photovoltaic) requires the usage of balancing methods by design. Over the years, several such methods were proposed and polished. Some of these methods use optimization techniques or inject a zero-sequence voltage to take advantage of the converter redundancies. This paper describes an optimization-based capacitor balancing method with additional features. It can drive each module DC-Link to a different voltage for independent maximum power point tracking in photovoltaic applications. Moreover, the user can specify the independent active power set points to modules connected to batteries or any other energy storage systems. Finally, DC current ripple can be reduced on some modules, which can extend the lifespan of any connected ultra-capacitors. The method as a whole is tested on real hardware and compared with the state-of-the-art. In its simplest configuration, the presented method shows greater speed, robustness, and current wave quality than the state-of-the-art alternative in spite of producing about 1/3 fewer commutations. Its other characteristics provide additional functionalities and improve the adaptability of the converter to other applications.

Keywords: capacitor balance; cascaded H-bridge converter (CHB); common-mode voltage; current ripple; multilevel converter; optimal control; pulse-width modulation (PWM) (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: 2021
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