Experimental verification of conduction noise of three-level V-connection rectifier-inverter system

This paper discusses the conduction noise reduction possibility of a transformer-less three-level V-connection rectifier-inverter system. This circuit is used for the main circuit in an Uninterruptible Power Supply (UPS) system. The efficiency of this circuit is higher than that of the conventional three-phase rectifier-inverter circuit due to no isolated transformer in output side. In this paper, to verify the conduction noise of the V-connection system, a theoretical analysis about the common-mode currents which based on the common-mode equivalent circuit, is discussed. Based on this, the comparison of the conduction noise between the three-level V-connection Back To Back (BTB) system and the conventional three-level three-phase connection BTB system is assumed. In addition, the conduction noise of two systems are measured and compared in order to confirm the assumption. As a result, it is confirmed that the conduction noise which is generated from the three-level V-connection rectifier-inverter circuit is higher than that of the conventional three-phase rectifier-inverter circuit.