Utility-interactive photovoltaic power conditioners - Effects of transformerless design and dc injection

It is shown that the use of isolation transformers to eliminate dc injection into the utility in utility-interactive photovoltaic (PV) systems can reduce the overall efficiency of the system. In order to improve PV efficiency, a transformerless power conditioning subsystem (PCS) is proposed for a grounded PV array having two and three connections to a utility. An additional transformerless PCS configuration is proposed for an ungrounded PV array. A detailed schematic drawing of the interconnections between the elements of a transformerless PCS is provided.