Premium
Asymmetrical modulation and overmodulation of parallel‐connected NPC‐PWM inverters
Author(s) -
Matsui Keiju,
Kawata Yasutaka,
Yamaguchi Tadashi,
Ueda Fukashi
Publication year - 1997
Publication title -
electrical engineering in japan
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.136
H-Index - 28
eISSN - 1520-6416
pISSN - 0424-7760
DOI - 10.1002/(sici)1520-6416(19970730)120:2<49::aid-eej7>3.0.co;2-t
Subject(s) - overmodulation , pulse width modulation , waveform , inverter , ripple , modulation (music) , harmonic , control theory (sociology) , voltage , electronic engineering , harmonics , computer science , engineering , electrical engineering , physics , acoustics , control (management) , artificial intelligence
The neutral point clamped (NPC)‐PWM inverter has significant advantages, such as its ability to operate motors with nearly sinusoidal current waveforms. For this reason, in larger‐capacity inverter systems, NPC‐PWM inverters using GTOs and the like have been put into practical use, because of great advantages to large‐capacity ac motor drives, such as lower ripple currents and higher output voltages. With the spread of applications, inverters of still larger capacity are expected. However, since the capacities of such switching devices are insufficient, a certain technique and controlling method are proposed for the parallel connection of NPC inverters. In this paper, conventional modulation techniques are extended to improve the inverter characteristics; asymmetrical modulation and overmodulation techniques are introduced for the parallel‐connected NPC inverter. In the proposed modulation strategies, the waveforms become more complicated, so that it is difficult to analyze the output waveforms. For those waveforms, an analytical waveform analysis method using the switching function is proposed. With such a method, the physical meaning of harmonic generation can be realized to some extent. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(2): 49–58, 1997