A Computational Efficient Space-Vector Modulation Scheme for A Hybrid Seven-Level Converter for Medium Voltage Grid-Tied Applications

An Active Hybrid Modulation Strategy for a Si/SiC Hybrid Multilevel Converter

“…The space-vector diagram for the 3-L SVM under αβframe (converted to the 60° αβ-frame) [10], [11] for the three H-bridges in phase A, B, and C is given in Fig. 5, which basically resembles to a three-level space-vector diagram for a three-phase 3-L converter.…”

“…There are three steps to implement the 3-L SVM, i.e., 1) determining the sector and modulation triangle region according to the reference vector location, 2) calculating duration time of the nearest three vectors, and 3) generating switching sequences. The first step is straightforward under the adopted 60° reference frame, since the sector and modulation triangle region number can be achieved by simple geometric calculation without rational numbers [10], [11]. Defining the dwell time of the three nearest vectors V1, V2, V3 as ta, tb, tc, respectively, according to the voltsecond balancing principle, the dwell time of the three nearest vectors can be calculated through the use of (4).…”

“…In this work, the five-segment approach [10], [11] is used to form the switching sequence, since it is easier to balance DC floating capacitors voltages in three H-bridges with plenty of redundant switching sequences in the fivesegment approach.…”

“…According to Table III, there are several possible switching sequences in each modulation triangle region which have different charge/discharge effects on H-bridge capacitors. In this work, a finite-control-set (FCS) method [10], [11], [34] is adopted to select the optimal switching sequence to minimize the voltage fluctuations of the three capacitors over one switching cycle Ts. At a certain switching state, an energy function E is designed to assess derivations between the actual DC floating capacitors voltages and their references as…”