A Dynamic-Segment-Alternating SVPWM for a Five-Level NNPP Converter With Neutral-Point Voltage Control

The neutral-point (NP) potential balance has always been an essential issue for multilevel converters. In this article, the primary cause of the NP potential deviation using seven-segment space vector pulse width modulation (SVPWM) is theoretically revealed. A dynamic-segment-alternating SVPWM (DSA-SVPWM) based on a five-level nested NP piloted converter is proposed, which can effectively balance the NP potential, suppress capacitor voltage oscillations and reduce harmonic distortions. The performance is observed with different power factors and modulation indexes, and the steady state and transient responses are analyzed. The conduction loss and switching loss of the converter are studied. The loss distributions among switching devices are also presented. The proposed DSA-SVPWM is simple to implement with good generalization ability, which allows it to be applied to converters of other topologies and levels. Simulations and experiments are performed to verify the method's effectiveness and practicality.