1. Enhancing the Ride-Through Capability of DC-Link Voltage in NPC Multilevel Unified Power-Flow Controllers.
- Author
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Santos, Natalia M. R., Silva, J. Fernando, Verveckken, Jan, Pires, Vitor M. Fernao, and Castro, Rui M. G.
- Subjects
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DIRECT currents , *ELECTRIC potential , *LOAD flow control (Electric power systems) , *PULSE width modulation transformers , *POWER capacitors , *REACTIVE power - Abstract
Multilevel converters are attractive for unified power-flow controller (UPFC) applications, due to their high-voltage and power capability. Among multilevel topologies, the three-level neutral-point-clamped (NPC) converter allows back-to-back connection as the UPFC shunt and series converters. Besides the pulsewidth-modulated (PWM) multilevel control schemes, UPFCs require constant dc-link voltage and balanced voltages in the NPC multilevel dc capacitors. This paper proposes three main contributions to increase the dc-link voltage steadiness of multilevel UPFCs under line faults: 1) decoupled active and reactive linear power controllers; 2) real-time PWM generation; and 3) double balancing of dc capacitor voltages. A case study using part of the Portuguese transmission network is presented. The results show the effectiveness of the real-time PWM generation and dc-link capacitor voltages balancing included in NPC series and shunt converters to keep the dc-link voltage steadiness under line faults, overall enhancing the UPFC ride-through capability. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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