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In high-power traction drive systems, the switching frequency of the inverter is strictly limited owing to the restrictions on switching losses and cooling conditions. In this case, the multimode modulation strategy is usually adopted. Based on the analysis of a modified 24-sector space vector pulse width modulation (SVPWM) technique, several synchronous modulation strategies with different pulse...
The neutral-point voltage balancing problem is a key issue for three-level three-leg neutral-point clamped (NPC) inverter used in three-phase four-wire system. In this paper, a detailed discussion on this issue and a mathematical model for the neutral-point voltage fluctuation are given. Then a novel neutral-point voltage control strategy based on the disassembly of zero level is proposed. To balance...
For medium/high voltage high-power neutral-point-clamped (NPC) three-level converters, narrow pulses appear usually when modulation waves are close to ±1 and 0. To ensure reliable switching and the safety, a long narrow pulse limit time needs to be set. Narrow pulse problems will become prominent. Meantime, neutral-point voltage balance problem of three-level NPC converters is a key issue that should...
A spectrum calculation method based on double Fourier series for chaotic SPWM control is firstly established in this paper, where, a chaotic sawtooth carrier is used in the SPWM control; further, a PV inverter under SPWM control is employed in this paper and the spectrum of its output voltage are calculated by the proposed method in this paper. By comparing with the simulation and experiment results,...
In this paper, The development of the topologies in multilevel converters is summarized and the relationship between the different topologies is analyzed. A conclusion that all existing topologies can be deduced from the generalized topology is obtained. Then two novel topologies are proposed. The operating concept and control strategy of the novel topologies are studied. Simulation results show the...
The neutral-point (NP) potential of the three-level neutral-point-clamped converters is needed to maintain balanced. Zero-sequence voltage is the only freedom degree when carrier-based PWM is utilized. Appropriate zero-sequence voltage should be identified to control the NP potential. The relationship between the neutral current and injected zero- sequence voltage is studied comprehensively, and a...
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