Fpga-Based Voltage Measurement Using Delta-Sigma Modulation For A Pmsm Drive

Nonlinear voltage distortion of the inverter affects the control performance of an AC drive, especially during low speed operations. For implementing advanced control algorithm such as sensorless control, compensation of the nonlinearity of the inverter is crucial. Thus, the availability of precise phase voltage measurement has great advantages. However, because of the switching nature of the PWM phase voltages, accurate phase voltage sensing is not trivial. In this paper, a novel direct measurement of the PWM phase voltages for a PMSM drive is introduced. The proposed method combines oversampling based on delta-sigma modulation and digital filtering. The implementation of the approach is based on high speed ADC and FPGA, actually well-known from current measurement and adapted to voltage measurement in this paper. The effectiveness and reliability of the proposed method are verified with experimental results.