AnImproved Natural Field Orientation Control ofa Current FedInduction Machine

Natural FieldOrientation (NFO)isa simplified s A rx=+ -) version ofstator fluxoriented (SFO)control foran induction = 6 machine. Theessential difference fromtraditional SFOisthat NFO doesnotestimate thestator fluxmagnitude butassumes ,; thatit's equal tothereference value. TheNFO algorithm only - t requires knowledge ofthestator resistance andisextremely simple toimplement. However, ithasbeenfoundthatNFO has stability problems underregeneration. Alsowhenimplemented ona current fedinduction machine, thecontrol framehasan x (ral) axis undesirable tendency tomisalign withrespect tothestator flux vector. Thispaperexamines boththeaboveissues indetail. It proposes asolution thatmitigates this undesirable behaviour and, R atthesametime, retains theinherent simplicity oftheNFOcontrol scheme. Thefindings ofthepaperaresubstantiated bysimulation andexperimental results.