Medium voltage grids are a suitable selection for the connection of high power applications. However, for certain applications, such as PV energy conversion systems or fast charging stations for PEVs, the DC voltages are limited to be below 1000 V, making difficult their connection to such grids without the use of a step-up transformer. Multilevel converters allow the grid connection of such DC loads, by connecting them in one of their multiple dc sources, however, due the nature of these applications unbalanced operation is inherent, and cannot be completely solved by the modulation stage, thus additional circuitry is required. On the other hand, the use of a multilevel converter provides higher efficiency in the power conversion stage, higher power quality and reduced stress on the switching devices, which is also beneficial due the power ratings being reached by the mentioned applications. This paper explores a four-level double star multilevel converter as interface for central or mul-tistring inverter for grid-connected photovoltaic energy systems. The topology is capable of handling three PV arrays with different MPPT (with or without additional DC-DC converters), with the use of an additional balancing stage. The four-level output voltage improves the power quality of the PV energy conversion system, while reducing the grid filter size. This paper presents the operating principle of the converter, the control scheme and the simulation results, that show this topology can be an interesting alternative for large-scale PV plants.
|Title of host publication||2017 19th European Conference on Power Electronics and Applications, EPE 2017 ECCE Europe|
|Publisher||Institute of Electrical and Electronics Engineers Inc.|
|State||Published - 6 Nov 2017|
|Event||19th European Conference on Power Electronics and Applications, EPE 2017 ECCE Europe - Warsaw, Poland|
Duration: 11 Sep 2017 → 14 Sep 2017
|Name||2017 19th European Conference on Power Electronics and Applications, EPE 2017 ECCE Europe|
|Conference||19th European Conference on Power Electronics and Applications, EPE 2017 ECCE Europe|
|Period||11/09/17 → 14/09/17|
Bibliographical noteFunding Information:
The authors acknowledge the support provided by FONDECYT 1171823, by AC3E (CONI-CYT/Basal/FB0008), and by SERC Chile (CONICYT/FONDAP/15110019)
© assigned jointly to the European Power Electronics and Drives Association & the Institute of Electrical and Electronics Engineers (IEEE).
- Converter control
- Multilevel converters
- Renewable energy systems