Strategy to detect and prevent the current zero-crossing for inverter powered drives

The output voltage of an inverter is often assumed proportional to the drive modulation signal. However, in practice the inverter presents nonlinear characteristics that may significantly affect the output voltage, and this may be critical in the context of sensorless drives and parameter identification. Nowadays, several solutions exist to compensate for the nonlinear behaviour of the inverter. Nevertheless, for the nonlinear effects at zero-crossing currents, no satisfying solution has yet been found. This paper proposes a calculation method that detects the occurrence of one or multiple zero-crossings of the current during a switching period. Then, an offset, selected in order to minimize the disturbance on the torque, is injected in the current control which prevents the current to cross zero. In that way, the disturbing effects of the zero-crossing current on the output voltages can be prevented. The method is evaluated for a permanent-magnet synchronous machine.