Design and cost analysis for STATCOM in low and medium voltage systems

With more installation of electronic loads and of distributed renewable energy sources, static compensators gain more interest to encounter the resulting power quality issues in low and medium voltage grids. Traditionally, two-level inverter topology, is utilized for this application, eventually with transformer at medium voltage. However, due to the low harmonics performance and the requirement for bulky filtering, the multilevel converters topologies become more attractive. Different topologies have been introduced during the last few decades and among the others, the Single-Star bridge cell is well applied to this application for its satisfactory performance and superior component count. Generally, the feasibility of adoption of static compensators for low and medium voltage systems relies strictly on their performance and cost-effectiveness. Theoretically, the harmonics performance improves with increasing the number of levels. However, this has a direct effect on their design and hence on their overall complexity and cost. In authors' knowledge, no paper has extensively discussed the impact of the number of levels on the cost of static compensators. Thus, this paper investigates some key factors in STATCOM design with emphasis on their impact on the overall cost in low and medium voltage applications.