Integration of Capture Based Phase Voltage Measurement for Surface Permanent Magnet Machine Position Sensorless Drive

This paper improves the position sensorless drive of permanent magnet (PM) machine by measuring actual phase voltages with pulse width modulation (PWM). On the basis, the phase voltage is obtained based on the digital integration of PWM voltage using the capture modulator in existing drive microcontrollers (MCU's). Comparing to existing phase voltage measurement, no separated A/D converter and communication hardware are required because PWM pulses are directly measured using MCUs. However for standard machines without neutral points, only line-to-line AC PWM voltages can be measured for the phase voltage reconstruction. Since the capture based on TTL logics receives only digital signals, a preprocess circuit to convert AC PWM line voltages to equivalent digital signals is proposed. This paper clearly explains the hardware implementation using MCU capture modulator. According to experimental results, a 150MHz sampling rate for phase voltage measurement is achieved based on the proposed capture-based voltage measurement.