Dead-time Compensation Based on Pole Voltage Measurement

This paper presents a simple dead-time compensation method for a three phase PWM inverter based on the measured pole voltage using enhanced capture (eCAP) module usually embedded in a digital signal processor (DSP). The information of the inverter pole voltages can be employed to compensate the voltage difference between commanded voltage and actual output voltage of the PWM inverter. Because the method does not rely on any other information except for the measured switching instants of each phase of the inverter, it can be easily accommodated into the low cost drive system where accurate and instantaneous measurement of the phase current is not available. The difference can be added at the next sampling time of the switching period of the PWM and could be updated after one sampling period due to the digital sampling delay. These total two sampling periods delay would degrade the performance of the dead-time compensation. To enhance the performance, a PI regulator is employed to nullify the difference in controlled manner. The effectiveness of the proposed compensation methods has been verified through the experimental results. Through the proposed compensation method, the 5th and 7th harmonic currents are reduced by 85% and 70%, respectively.