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DIRECT STATOR FLUX FIELD ORIENTED CONTROL (DSFOC). Direct Rotor Flux FOC (DRFOC). Two methods of estimating the rotor flux in Direct Rotor flux FOC :. Current model:. Voltage model:. Direct Rotor Flux FOC (DRFOC). Both methods are sensitive to parameter variations.
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Direct Rotor Flux FOC (DRFOC) Two methods of estimating the rotor flux in Direct Rotor flux FOC : Current model: Voltage model:
Direct Rotor Flux FOC (DRFOC) • Both methods are sensitive to parameter variations • To improve control characteristic, a more accurate feedback signal is needed • This leads to Direct Stator Flux FOC
Direct Stator Flux FOC (DSFOC) • All quantities are referred to a frame which is attached to the stator flux
Direct Stator Flux FOC (DSFOC) • All quantities are referred to a frame which is attached to the stator flux Since sq= 0 and sd= s
Direct Stator Flux FOC (DSFOC) • A closer look at the equations reveals a coupling between torque producing current and flux (X. Xu, PESC 1988):
d q Direct Stator Flux FOC (DSFOC) There exists a coupling between iqs and s Any change in isq will cause a transient in s
Direct Stator Flux FOC (DSFOC) • How does the stator flux estimated? Only Rs is required ! – the vs and is are measured
vd d + id Rs iq Rs vq q + Direct Stator Flux FOC (DSFOC) • How does the stator flux estimated? However, in practice ……. DC offset – causing integrator to saturate Use of LP filter instead of pure integrator N.R.N. Idris and A.H.M Yatim “Improved stator flux estimation in steady state operation for Direct Torque Control of Induction Machines”, IEEE Transaction on Industry Applications Volume: 38 Issue: 1 , Jan./Feb. 2002 Pg: 110 -116
Tref isq isd 2 3 ejs current controlled VSI decoupler s IM isd + flux regulator ref s is stator flux estimator |s| vs Direct Stator Flux FOC (DSFOC) - Block diagram - For the detail of the decoupler, please refer to: X. Xu, R. K. Doncker, and R. W. Novotny, “ A stator flux oriented induction machine drive”, IEEE Power Electronics Specialist Conference, April 1988