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Low Switching Frequency Control of Modular Multi-Level Converter


G. Darivianakis

Master Thesis, FS14 (10328)

This thesis proposes a novel control method based on the concept of model predictive control for the multilevel converter (MMC) operated as a static synchronous compensator (Statcom). The proposed control scheme is applicab le to any MMC Statcom regardless of its circuit parameters, phase configuration and number of modules. The primary objective of the controller is to regulate its output currents such that reactive power compensation and corrent harmonic filtering of the unbalanced and/or distorted load to be achieved. Moreover, the poposed scheme effectively controls the branch currents and the sum of the capacitor voltages per branch while respecting upper and lower limits imposed on them. At the top level of the poposed hierarchical control scheme the voltage references of a multilevel carrier-based pulse with modulator are evaluated. A subsequent balancing controller manipulates the capacitor voltages within each branch around their average voltage and guarantees low switching frequencies of the semiconductor devices. Unlike state of the art approaches that are based on multible PI control loops and additional filtering devices, the proposed controller is able to address the reactive power compensation and load current harmonics filtering control problems at one computational stage. Moreover, it achieves not only a very good performance at steady-state operation but also very fast current responses during load transients, while maintaining the branch currents and capacitor voltages within their safe operating limits.


Type of Publication:

(12)Diploma/Master Thesis

J. Lygeros

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% Autogenerated BibTeX entry
@PhdThesis { Xxx:2014:IFA_4804
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