Grid interaction and power quality parameters of grid coupled photo-voltaic systems and wind energy converters

Distributed generators with energy conversion from solar energy, wind energy, bio mass and fuel cells will deliver an increasing energy portion in the future. One of the main arguments against the integration of dispersed energy generation is their influence on the power quality of the grid. This contribution contains results of extensive power quality investigations of grid connected photovoltaic systems and wind energy converters. The characteristic of the devices, their power quality properties and measurement results at the low- and medium-voltage level are outlined. Power quality parameters are introduced and their standard limits and definitions are given. Photovoltaic systems are connected mostly to the low voltage bus because of their limited power. Despite the high pulse frequencies of the inverters used, mutual influences and dynamic instabilities occur. Wind energy converters work with low voltage generators connected to power electronic inverters, that feed the converted energy into the medium voltage level. The inverter switching causes grid distortions, which is also the topic of our work. Curves of harmonic parameters for different wind energy converters are presented.