1. (1) A. Nabae, I. Takahashi, and H. Akagi: “A new neutral-point-clamped PWM inverter”, IEEE Trans. Ind. Appl., Vol. 17, No. 5, pp. 518-523 (1981)
2. (2) R. H. Baker: “Synthesizer circuit for generating three-tier waveforms”, US Patent, No. 4, 135, 235 (1977)
3. (3) P. M. Bhagwat and V. R. Stefanovic: “Generalized structure of a multilevel PWM inverter”, IEEE Trans. Ind. Appl., Vol. 19, No. 6, pp. 1057-1069 (1983)
4. (4) T. Migaki, K. Sato, Y. Kondo, and T. Fukao: “Control method of DC yard voltage fluctuation in 5-level output self-excited VAR compensator”, IEEJ Papers of Technical Meeting on Semiconductor Power Converter, SPC-96, pp. 89-98 (1996)
5. A New Control Method of a Resonant Switched-Capacitor Converter and the Application for Balancing of the Split DC Voltages in a Multilevel Inverter