Fuzzy Logic Control for motor flux reduction during steady states and for flux recovery in transient states of Indirect-FOC AC drives

The aim of this paper is to present a new fuzzy control scheme for real time drive efficiency improvement by the adaptive flux reduction at light loads during steady states and by the optimum flux recovery during transient states. The optimum flux recovery instead of the rated flux does not sacrifice the drive dynamic response since the torque capacity remains the same and accelerates the search convergence in steady states. The control scheme is cooperated with an Indirect-Field-Oriented-Control (IFOC) motor drive. The design of the new fuzzy control scheme is focused to recognize the motor state operation in order to control under the corresponding circumstances. The proposed fuzzy control scheme includes three main units: one Fuzzy-Logic-Search Controller FLSC1, one Fuzzy-Logic-Controller FLC2 and a State detector unit. The State detector unit decides which of the FLSC1 or FLC2 controllers is used, in accordance to the operation circumstances. The fuzzy controllers utilize the stator flux-producing current component into d-q reference frame (stator current direct axis i_sd) as control variable, in order to estimate the next optimal change of Δi_sd. The drive efficiency improvement and the drive dynamic response is currently validated in laboratory using an experimental array of a 3-phase 1 Hp induction motor drive. The control scheme is implemented using the platform eZdsp from Digital Spectrum based on the fixed point 32 bit DSP TMS320F2812 from TI.