New method for current and voltage measuring offset correction in an induction motor sensorless drive

This paper presents a new algorithm for electromagnetic torque and flux estimation in a sensorless drive when uncompensated dc offset of current and/or voltage sensors are present. The novel feature of the offset error correction algorithm is an attempt not to eliminate the consequence of problem but to identify its source. The algorithm uses the first harmonic of estimated torque and dc value of estimated stator flux to identify the source and value of the current and/or voltage offset error. Identified values can be used for offset cancelation which improves estimation process.