On DC injection to AC grids from distributed generation

Distributed generation, DG, introduces multi-generator grids and new modes of operation. DG will likely introduce power electronic, PE, converters on a large scale at the low- and medium-voltage levels. DC injection into the AC grid is a threat from grid-connected PE converters that are badly structured. Low DC currents in AC current are difficult to measure at those low levels decided in IEEE/spl trade/ 1547 and discussed in other international working groups. Transformers and PE can be co-designed to eliminate DC injection. Modern adjustable-speed drives, ASDs, especially, those with active rectifiers, form a basis to discuss and solve issues of DC injection to AC grids from DG also named distributed energy resources, DER or even DR. DC components from power electronics, embedded in solar power, wind power, energy storage, smart houses, smart-office buildings, own generators, etc. give rise to grid-aspects like AC components give frequencies around the fundamental one. FMEA, failure mode and effects analysis, is judged to be a tool for further synthesis.