A Study on Neutral-Point Potential in Three-Level NPC Converters

Maosong Zhang, Ying Cui, Qunjing Wang, Jun Tao, Xiuqin Wang, Hongsheng Zhao and Guoli Li
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Maosong Zhang: School of Electrical Engineering and Automation, Anhui University, Hefei 230601, China
Ying Cui: School of Electrical Engineering and Automation, Anhui University, Hefei 230601, China
Qunjing Wang: School of Electrical Engineering and Automation, Anhui University, Hefei 230601, China
Jun Tao: School of Electrical Engineering and Automation, Anhui University, Hefei 230601, China
Xiuqin Wang: School of Electrical Engineering and Automation, Anhui University, Hefei 230601, China
Hongsheng Zhao: State Grid Hubei Electric Power Company Limited Economic Research Institute, Wuhan 430077, China
Guoli Li: School of Electrical Engineering and Automation, Anhui University, Hefei 230601, China

Energies, 2019, vol. 12, issue 17, 1-22

Abstract: This paper proposes an accurate mathematical model of three-level neutral-point-clamped (NPC) converters that can accurately represent the midpoint potential drift of the DC link with parameter perturbation. The mathematical relationships between the fluctuation in neutral-point voltage, the parametric perturbation, and the capacitance error are obtained as mathematical expressions in this model. The expressions can be used to quantitatively analyze the reason for the neutral-point voltage imbalance and balancing effect based on a zero-sequence voltage injection. The injected zero-sequence voltage, which can be used to balance the DC-side voltages with the combined action of active current, can be easily obtained from the proposed model. A balancing control under four-quadrant operation modes is proposed by considering the active current to verify the effectiveness of this model. Both the simulation and experiment results validate the excellent performance of the proposed model compared to the conventional model.

Keywords: neutral-point-clamped (NPC) converters; quantitative analysis; uneven shunt loss; zero-sequence voltage; active current (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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