Abstract
this paper presents an improved two-level voltage source converter for dc transmission systems with relatively low rated power and dc operating voltage. Unlike conventional two-level converter, the presented converter employs two distributed cell capacitors per three-phase; thus, do not contribute any current when converter is blocked during dc short circuit fault as in modular multilevel converter case. The use of three-phase cells is proven to be beneficial because the arm currents do not contain 2nd order harmonic currents, and cell capacitors tend to be small as they only experience high-order harmonic current associated with the switching frequency. For the same rated dc link voltage and switching devices, the rated power of the improved two-level converter will be twice that of the conventional two-level converter. Average, switching function and electromagnetic transient simulation models of the improved two-level converter are discussed and validated against detailed switch model. The viability of the improved two-level converter for HVDC applications is examined, considering dc and ac short circuit faults. Besides, reduced complexity of the control and power circuit of the improved two-level converter, it has been found that its transient responses to ac and dc faults are similar to that of the modular multilevel converter.
Original language | English |
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Journal | IEEE Journal of Emerging and Selected Topics in Power Electronics |
Early online date | 13 Jul 2017 |
DOIs | |
Publication status | E-pub ahead of print - 13 Jul 2017 |
Keywords / Materials (for Non-textual outputs)
- ac and dc fault ride-through capability
- Capacitors
- Circuit faults
- Complexity theory
- Harmonic analysis
- high-voltage dc transmission systems
- HVDC transmission
- modular multilevel converter
- Modular multilevel converters
- Switches
- two-level voltage source converter