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Closed-Loop Discontinuous Modulation Technique for Capacitor Voltage Ripples and Switching Losses Reduction in Modular Multilevel Converters

2014; Institute of Electrical and Electronics Engineers; Volume: 30; Issue: 9 Linguagem: Inglês

10.1109/tpel.2014.2368055

1941-0107

Ricard Picas, Salvador Ceballos, Josep Pou, Jordi Zaragoza, Georgios Konstantinou, Vassilios G. Agelidis,

High-Voltage Power Transmission Systems

In this paper, a new discontinuous modulation technique is presented for the operation of the modular multilevel converter (MMC). The modulation technique is based on adding a zero sequence to the original modulation signals so that the MMC arms are clamped to the upper or lower terminals of the dc-link bus. The clamping intervals are controlled according to the absolute value of the output current to minimize the switching losses of the MMC. A significant reduction in the capacitor voltage ripples is achieved, especially when operating with low modulation indices. Furthermore, a circulating current control strategy suitable for this modulation technique is also proposed. Simulation and experimental results under various operating points are reported along with evaluation and comparison results against a conventional carrier-based pulse width modulation method.