Identification and compensation of inverter dead-time effect on zero speed sensorless control of AC machines based on voltage pulse injection

In this paper the influence of the non-ideal behavior of power electronics, sensors, and signal processing on pulse signal injection based speed sensorless control is addressed and investigated. The speed sensorless control signals are obtained from the transient current response resulting from an excitation of the machine with voltage pulses. The investigation is focused on sensorless control of induction machines however, the results are applicable also for other types of ac machines. By using pulse width modulation in combination with voltage source inverters the inverter interlock dead-time is essential necessary to prevent the short circuit of the dc link. A new approach to identify the interlook dead-time by utilizing the transient voltage pulses and the current response is presented. The disturbing influences and effects of the inverter interlock dead-time on the resulting signal include the deviation of the operating point during the pulse injection, as well as additional resulting harmonics in the control signal. For the specific problem of compensating these effects on the signal injection measurement a new approach is applied in this paper. After identifying the effective dead time the switching commands are adapted in order to clearly reduce the disturbing effects. Further simulation results and additionally measurement results are presented to show the influence on the resulting control signals.