HFSI — A promising solution to very low speed issues in DTC-SVM induction motor drive

The stator flux and electromagnetic torque are directly controlled in a DTC system using space vector modulation technique. In DTC, torque and flux ripples increases at low speeds. A DTC-SVM induction motor drive at very low speeds is investigated here and High Frequency Signal Injection (HFSI) method is adopted to mitigate the low speed issues. In this method a sinusoidal wave of small amplitude and high frequency is injected along with the PI controller output of DTC-SVM. HFSI increases the switching frequency of SVM during low speed operation. This technique reduces torque ripple, acoustic noise, and gives excellent dynamic and steady state performance. The performance of DTC-SVM and DTC-SVM with HFSI at low speed is analyzed through simulation using matlab/simulink package. The results verify the merits of the DTC-SVM using HF injection technique with respect to DTC-SVM technique at very low speeds.