Single-phase multilevel neutral-point-clamped (NPC) voltage source inverter has been widely applied in AC traction drive system, the carrier-based pulsewidthmodulation (CBPWM) method and the spacevectorpulsewidth...
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Single-phase multilevel neutral-point-clamped (NPC) voltage source inverter has been widely applied in AC traction drive system, the carrier-based pulsewidthmodulation (CBPWM) method and the spacevectorpulsewidthmodulation (SVPWM) method are mainly two modulationmethods for single-phase NPC multilevel converters, and there is a certain relationship between these two modulation strategies. In this study, the unified relationship between SVPWM and CBPWM in single-phase three-level and five-level NPC has been analysed. Then by injecting the zero-sequence component into the initial modulation wave, the same switching state and output current as SVPWM can be achieved through modulation waves decomposed under the CBPWM strategy. Finally, the unified theory of SVPWM and CBPWM in an N-level inverter with an arbitrary number of segments sequence was deduced. The simulation and experimental results illustrate that the unified theory between CBPWM and SVPWM is correct. With the zero-sequence injected, CBPWM can realise the same effect as SVPWM, but the former is simpler than the latter, which is easy to promote for higher-level applications.
This study proposes a cost-effective four-switch single-phase to three-phase converter with an improved space vector pulse width modulation method. This structure employs the quasi-Z-source (QZs) topology that can be ...
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This study proposes a cost-effective four-switch single-phase to three-phase converter with an improved space vector pulse width modulation method. This structure employs the quasi-Z-source (QZs) topology that can be utilised in induction motor drive applications. Compared with conventional four-switch structures, buck-boost operation is a unique property of this configuration. This four-switch QZs structure decreases the switching losses, load current total harmonic distortion and cost in comparison with traditional six-switch structures. Without using any extra filtering circuits, the applied modulationmethod can work well to reject the influence of DC-link voltage ripples on the converter voltage, which can be accomplished by either power supply or voltage variations in the four-switch structure. The closed-loop modulation strategy recognises via sensing any unbalanced voltage that occurs across two split capacitors, and by applying the changes in the vector's activation interval time, the three-phase output voltage can be balanced. The simulation and experimental results of the suggested converter with the improved modulationmethod have demonstrated the converter's performance and the potential of the structure to be further developed.
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