A multilevel converter topology for a STATCOM system based on four-leg two-level inverters and cascaded Scott Transformers

• Autor(a) principal: Fernao Pires, Vitor
• Data de Publicação: 2022
• Outros Autores: Cordeiro, Armando, Foito, Daniel, Silva, José Fernando
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.21/14720
• topic: Automatic voltage control; Topology; Windings; Capacitors; Load flow; Reactive power; Voltage source inverters; Static synchronous compensator (STATCOM); Multilevel power converter; Fourl-leg two-level voltage source converters; Scott Transformer

This paper presents a new power electronic topology for a STATCOM allowing the generation of multilevel AC voltages. This topology is characterized by a modular configuration since it uses two well known four-leg two-level voltage source inverters. A Scott transformer with multiple secondary windings connects the two four-leg inverters to the grid. One of the important features of the proposed power topology is the capability to generate AC voltages with high number of levels, in spite of using only two four-leg two-level voltage source inverters. To maximize the number of voltage levels a geometric progression ratio of 3 between the windings of the transformers connected in cascade is proposed. However, to reduce the turns-ratio span, alternatively a fractional geometric ratio of 1.5 is also proposed and analyzed. A control strategy adapted to the proposed power converter topology is also presented. Besides the control of the reactive power the regulation of the four-leg inverter DC voltage will also be considered. To support the theoretical studies and assumptions, simulations and experiments are presented. Experimental results were obtained using a low power laboratory prototype. The results shown give evidence to the characteristics and features of the proposed power converter topology and control system.