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Title: An Efficient Modulation Strategy for Cascaded Photovoltaic Systems Suffering From Module Mismatch

Modular multilevel cascaded converter (MMCC) is a promising technique for medium/high-voltage high-power photovoltaic systems due to its modularity, scalability, and capability of distributed maximum power point tracking (MPPT) etc. However, distributed MPPT under module-mismatch might polarize the distribution of ac output voltages as well as the dc-link voltages among the modules, distort grid currents, and even cause system instability. For the better acceptance in practical applications, such issues need to be well addressed. Based on mismatch degree that is defined to consider both active power distribution and maximum modulation index, this paper presents an efficient modulation strategy for a cascaded-H-bridge-based MMCC under module mismatch. It can operate in loss-reducing mode or range-extending mode. By properly switching between the two modes, performance indices such as system efficiency, grid current quality, and balance of dc voltages, can be well coordinated. In this way, the MMCC system can maintain high-performance over a wide range of operating conditions. As a result, effectiveness of the proposed modulation strategy is proved with experiments.
Authors:
 [1] ;  [1] ;  [1] ; ORCiD logo [2] ; ORCiD logo [3]
  1. Huazhong Univ. of Science and Technology, Wuhan (China)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Lehigh Univ., Bethlehem, PA (United States)
Publication Date:
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
IEEE Journal of Emerging and Selected Topics in Power Electronics
Additional Journal Information:
Journal Volume: 6; Journal Issue: 2; Journal ID: ISSN 2168-6777
Publisher:
IEEE
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Electricity Delivery and Energy Reliability (OE)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; cascaded photovoltaic (PV) system; modulation strategy; module mismatch; switching loss
OSTI Identifier:
1436029

Wang, Cheng, Zhang, Kai, Xiong, Jian, Xue, Yaosuo, and Liu, Wenxin. An Efficient Modulation Strategy for Cascaded Photovoltaic Systems Suffering From Module Mismatch. United States: N. p., Web. doi:10.1109/JESTPE.2017.2756338.
Wang, Cheng, Zhang, Kai, Xiong, Jian, Xue, Yaosuo, & Liu, Wenxin. An Efficient Modulation Strategy for Cascaded Photovoltaic Systems Suffering From Module Mismatch. United States. doi:10.1109/JESTPE.2017.2756338.
Wang, Cheng, Zhang, Kai, Xiong, Jian, Xue, Yaosuo, and Liu, Wenxin. 2017. "An Efficient Modulation Strategy for Cascaded Photovoltaic Systems Suffering From Module Mismatch". United States. doi:10.1109/JESTPE.2017.2756338. https://www.osti.gov/servlets/purl/1436029.
@article{osti_1436029,
title = {An Efficient Modulation Strategy for Cascaded Photovoltaic Systems Suffering From Module Mismatch},
author = {Wang, Cheng and Zhang, Kai and Xiong, Jian and Xue, Yaosuo and Liu, Wenxin},
abstractNote = {Modular multilevel cascaded converter (MMCC) is a promising technique for medium/high-voltage high-power photovoltaic systems due to its modularity, scalability, and capability of distributed maximum power point tracking (MPPT) etc. However, distributed MPPT under module-mismatch might polarize the distribution of ac output voltages as well as the dc-link voltages among the modules, distort grid currents, and even cause system instability. For the better acceptance in practical applications, such issues need to be well addressed. Based on mismatch degree that is defined to consider both active power distribution and maximum modulation index, this paper presents an efficient modulation strategy for a cascaded-H-bridge-based MMCC under module mismatch. It can operate in loss-reducing mode or range-extending mode. By properly switching between the two modes, performance indices such as system efficiency, grid current quality, and balance of dc voltages, can be well coordinated. In this way, the MMCC system can maintain high-performance over a wide range of operating conditions. As a result, effectiveness of the proposed modulation strategy is proved with experiments.},
doi = {10.1109/JESTPE.2017.2756338},
journal = {IEEE Journal of Emerging and Selected Topics in Power Electronics},
number = 2,
volume = 6,
place = {United States},
year = {2017},
month = {9}
}