A 6.6-kV Transformerless STATCOM Based on a Five-Level Diode-Clamped Converter-Experiment by the Three-Phase Laboratory Model Rated at 200 V and 10 kVA-

This paper discusses a 6.6-kV transformerless STATCOM intended for installation on industrial and utility distribution systems in the near future. In addition, this paper provides experimental results obtained from a laboratory model rated at 200V and 10kVA. The authors propose such a control method as to superimpose a 6th-harmonic zero-sequence component on each of three-phase voltage references. This helps to stabilize the voltage of the inner midpoint in the dc link. As a result, the laboratory model installs two bi-directional buck-boost choppers on the dc link for the porpose of stabilizing the voltages of two outer midpoints. Experimental results obtained from the laboratory model verify the validity of the system design, giving promise of the viability of the 6.6-kV transformerless STATCOM.