Sinusoidal three-phase current reconstruction and control using a dc-link current sensor and a curve-fitting observer

Successful operation of three-phase current controllers requires measurement of the instantaneous values of phase currents. An innovative method to estimate the three-phase currents from dc-link current is presented. A sinusoidal curve-fitting observer that does not use any of the load parameters is employed. Using the firing signals and the dc-link current for corrective action, the observer generates stable three-phase feedback signals, even during short periods when the phase current information is not present in the dc-link current.