Sensorless Motor Drives with Predictive Current Control

Hardware complexity of a motor drive can be reduced by estimating controls rather than measuring using sensors. In this way the corresponding sensors are eliminated and the system becomes more robust. This article is about speed control of a sensor less induction motor with predictive current controller technique. This particular speed control technique does not require direct measurements of motor speed or motor flux. The PCC is based on a closed loop observer, which is insensitive to parameter variations. This closed loop observer calculates the required state variables over wide frequency range. This technique is more reliable even at very low frequency due to its insensitive nature against changes of motor parameters. It is proved that the drive system is applicable to the high dynamic performance and wide range of rotor speed. The obtained simulation results confirm the good properties of the proposed speed sensor less induction motor drive. Keywordspredictive current control, closed loop observer, sensorless induction motor. I. Nomenclature PCC – Predictive current controller IM – Induction motor, FOC – Field oriented control, PWM – Pulse width modulation, EMF – Electromagnetic force (back EMF) SVM – Space vector modulation, αβ – Stationary frame of references, dq – Rotating frame of references, p.u. – per unit system com – Superscript denotes commanded value, pred – Superscript denotes predicted value, ^ – Denotes value calculated in the observer, bold style font denotes vector CEMF – EMF transformation matrices, C2EMF – EMF transformation matrices, e – Motor EMF, is, ir – Stator and rotor current vector, J – Inertia, k, k-1 – Instants of calculation: actual, previous, etc., kab – Observer gain, Lr – Rotor inductance, Ls – Stator inductance, Lm – Mutual inductance, Rr – Rotor resistance, Rs – Stator resistance Timp – Inverter switching period, TL – Load torque, us – Stator voltage vector, υe – Angle position of the motor EMF vector, ρψs – Angle position of the rotor flux vector, ωr – Rotor mechanical speed, ω2 – Motor slip, I