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

Journal Article · Tue Sep 26 00:00:00 EDT 2017 · IEEE Journal of Emerging and Selected Topics in Power Electronics

DOI:https://doi.org/10.1109/JESTPE.2017.2756338· OSTI ID:1436029

Wang, Cheng ^[1]; Zhang, Kai ^[1]; Xiong, Jian ^[1]; Xue, Yaosuo ^[2]; Liu, Wenxin ^[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)

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.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Electricity Delivery and Energy Reliability (OE)
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1436029
• Journal Information: IEEE Journal of Emerging and Selected Topics in Power Electronics, Journal Name: IEEE Journal of Emerging and Selected Topics in Power Electronics Journal Issue: 2 Vol. 6; ISSN 2168-6777
• Publisher: IEEE
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
cascaded photovoltaic (PV) system
modulation strategy
module mismatch
switching loss