Current Limit Strategy for BLDC Motor Drive With Minimized DC-Link Capacitor

Brushless dc motor drive system employing minimized dc-link capacitor is becoming popular for the reason of compactness and long lifetime. However, once the capacitance is reduced, reversal dc-link current will lead to excessive voltage rise in the dc link when conventional current limit strategy is used. In order to avoid the damage caused by oversize pumping-up voltage, a novel current limit strategy without reversal dc-link current is necessary. In this paper, the traditional all-turn-off current limit logic is replaced by half-turn-off logic. Then, an improved current sampling scheme is presented to replace the cycle-by-cycle mode, which induces failure of current limiting after the elimination of reversal current. Finally, the proposed strategy is verified by simulation and experiment.