Correction of Field Orientation Inaccuracy Caused by Resolver Periodic Error and Rotor Time Constant Variation for IFOC Induction Motor Drives

This paper proposes an algorithm correcting the field orientation inaccuracy caused by resolver periodic error and rotor time constant variation. It is found that the periodic error brings harmonic current vectors and torque ripples while the rotor time constant variation makes dq currents deviate from the reference values. The crossproduct of fundamental and harmonic current vectors contains the information of resolver periodic error. The gradient descent method with a variable step is introduced to compensate the periodic error. During the process, the crossproduct is minimized. A new form of cross-product calculation is derived to reduce the computation time. The rotor time constant is identified by the reactive-power based model reference adaptive system (MRAS). Voltages and currents in the stationary reference frame are used in the reference model to avoid the influence of resolver periodic error. Appropriate parameters of the MRAS are selected to guarantee the stability. The algorithm is integrated with an induction motor (IM) drive which is based on indirect field-oriented control (IFOC). The feasibility of the proposed algorithm is verified by simulation results and experiments.