Analysis and design of an advanced static VAr compensator using quad-series voltage-source inverters

This paper presents an advanced static VAr compensator (ASVC) using quad-series voltage-source inverters. The ASVC consists of four three-phase voltage-source inverters having a common DC capacitor and four three-phase transformers, the primary windings of which are connected in series to each other. Although each inverter outputs a square wave voltage, the synthesized output voltage of the ASVC has a 24-step wave shape. This results not only in a great reduction of harmonic currents and DC voltage ripples but also in less switching and snubbing losses. This paper develops the analysis of the transient response and the resonance between AC reactors and the DC capacitor with the focus on practical use. Experimental results obtained from a small-rated laboratory model of 10 kVA are also shown to verify the analysis leading to the design of the DC capacitor. The experimental and analytical results agree well each other.