A novel current derivative measurement using recursive least square algorithms for sensorless control of permanent magnet synchronous machine

The parasitic components of the VSI system cause high frequency oscillations in the motor current when an IGBT switches. To accomplish current derivative measurement for the position estimation using PWM voltage vector excitation, the one di/dt sample can be directly derived from the measurement of two motor current samples without sensors. In this paper, a proposed method is introduced, and which utilizes an advanced signal processing technique to estimate current samples during the oscillation period. With a robust and capable data acquisition system (FPGA/DSP), signal processing method can be implemented for the online current measurement, so the PWM excitation saliency tracking method can be definitely used to estimate the position without need of any additional di/dt sensors.