Abstract
Diode-clamped multi-level converters have DC-side capacitors in series, which will lead to the unbalance of DC-side capacitor voltage, the distortion of the output waveform, the increase of total harmonic distortion (THD), and even the damage of switching devices, which will make the system inoperable. The proposal of virtual space vector pulse-width modulation (VSVPWM) realizes the balanced control of the capacitor voltage, but when the output level of converter increases, the implementation of VSVPWM becomes very complicated, and the amount of calculation also increases greatly, thus hindering its application in the multi-level circuit. Compared with VSVPWM, the carrier-based pulse-width modulation (CBPWM) is simple to operate and easy to implement. If the equivalent relationship between CBPWM and VSVPWM can be found, the application of VSVPWM can be generalized to any level, and the advantages of VSVPWM can be fully utilized. This paper aims to study the inner relationship of VSVPWM and the multi-modulation carrier CBPWM (MCBPWM). After strict theoretical analysis, the equivalent relationship of VSVPWM and MCBPWM in the three-level and four-level and converter is realized by injecting the zero-sequence component into the modulation waves. Furthermore, the equivalent relationship between VSVPWM and MCBPWM is deduced to the N-level converter. Finally, the correctness of the relevant theoretical analysis is verified by the experiment.
Highlights
In recent years, the diode-clamped multi-level converter has been widely used in many fields due to its low switching stress and low harmonic distortion rates [1], such as power system DC transmission [2], reactive power compensation [3], active power filter and frequency conversion speed regulation of high-voltage high-power AC motor, etc
This paper aims to study the inner relationship of virtual space vector pulse-width modulation (VSVPWM) and the multi-modulation carrier
The equivalent relationship of VSVPWM and modulation carrier CBPWM (MCBPWM) in the three-level and four-level and converter is realized by injecting the zero-sequence component into the modulation waves
Summary
The diode-clamped multi-level converter has been widely used in many fields due to its low switching stress and low harmonic distortion rates [1], such as power system DC transmission [2], reactive power compensation [3], active power filter and frequency conversion speed regulation of high-voltage high-power AC motor, etc. Reference [16] proposed a brand-new modulation wave decomposition strategy, which makes the decomposition of more than eight-segment space vector output sequences possible, perfecting the realization of the equivalent relationship. It only studies a three-level converter and does not study higher-level output converters. By solving the volt-second balance and the boundary condition equations, the equivalence between the three-phase dual-modulated wave CBPWM and VSVPWM 10-segment sequences was realized It does not study how the command voltage modulated wave is decomposed into double modulated waves and does not give the expression of the zero-sequence component of the equivalent relationship.
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