Space Vector Modulation with Flexible Three-Segment Switching Sequence for Five-Level Inverters

This paper presents a space vector modulation (SVM) algorithm with flexible 3-segment switching sequence and its application to five-level inverters. In the flexible 3-segment SVM, the leading state of the switching sequence is selected according to minimum change of state value to ensure minimum switchings when the space vector hops between different triangles in the vector plane, and the switching sequence is generated in a flexible way according to the state value of the leading state, rather than using predefined patterns as most conventional SVM schemes do. The algorithm is simplified and the waveform symmetry is guaranteed by a simple ´state rotation and inversion´ to reproduce the switching sequence of Sector I for the other sectors. Simulation results show that the flexible 3-segment scheme can minimize or eliminate extra switchings. For a given switching frequency, the proposed 3-segment scheme yields lower WTHD than the conventional 7-segment scheme. Experimental spectrum of the output voltage verifies the simulation results