Open AccessNeutral point potential balancing method for three‐level power converters in two‐stage three‐phase four‐wire power conversion system
Author(s) -
Guo Li,
Liu Rui,
Li Xialin,
Zhang Yun
Publication year - 2020
Publication title -
iet power electronics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.637
H-Index - 77
eISSN - 1755-4543
pISSN - 1755-4535
DOI - 10.1049/iet-pel.2019.1211
Subject(s) - ripple , converters , control theory (sociology) , power (physics) , automatic frequency control , buck converter , computer science , topology (electrical circuits) , electronic engineering , voltage , engineering , electrical engineering , physics , telecommunications , control (management) , quantum mechanics , artificial intelligence
Two‐stage power conversion system (PCS) for energy storage systems has been considered in islanded operation mode. A three‐level T‐type three‐leg three‐phase four‐wire topology (3LT 2 3L3P4W) is employed as AC/DC part and a three‐level buck/boost converter is used as DC/DC interface. This study is mainly focused on balancing the neutral‐point potential (NPP) of the PCS with asymmetrical load connection. An NPP low‐frequency ripple model of 3LT 2 3L3P4 inverter is proposed considering various load conditions firstly, which includes detailed expression of low‐frequency ripple components at fundamental frequency and fundamental frequency multipliers. Then, a novel NPP balancing method based on front‐end three‐level buck/boost converter under proportional resonant control is presented, in which the resonance points are set at fundamental frequency and triple fundamental frequency to suppress the dominant components of NPP ripple. Furthermore, a small‐signal model of three‐level buck/boost NPP control system is established and stability analysis is carried out. Simulation and experimental results have been provided to verify the accuracy of the NPP low‐frequency ripple model and the effectiveness of the NPP balancing method.