An improved DTC-SVM method for sensorless matrix converter drives using an overmodulation strategy and a simple nonlinearity compensation

In this paper, an improved direct torque control (DTC) method for sensorless matrix converter drives is proposed, which is characterized by minimal torque ripple, unity input power factor, and good sensorless speed-control performance in the low-speed operation, while maintaining constant switching frequency and fast torque dynamics. It is possible to combine the advantages of matrix converters with the advantages of the DTC strategy using space-vector modulation and two PI controllers. To overcome the degrading of dynamic torque response compared with the basic DTC method and the phase-current distortion due to the nonlinearity of the matrix converter, an overmodulation strategy and a simple nonlinearity-compensation method using PQR transformation are also presented. Experimental results are shown to illustrate the feasibility of the proposed strategy. Index Terms--AC motor drives, ac--ac power conversion, adaptive observers, induction motor drives.