DC-link capacitors are one of the components with the largest physical volume and highest failure rate in motor drives

and current ripple is an important factor limiting its performance. This paper establishes an optimization model based on time domain analysis

which transforms the capacitor current stress reduction into a linear programming (LP) problem. Then a capacitor current stress minimization strategy based on extended out-of-sector vectors is proposed for three-phase half-bridge motor drives. First

an optimization model in the time domain is established according to the switching state

DC-link current

optimization objective function

and constraint conditions

revealing that the vectors outside the sector containing the reference voltage vector help reduce capacitor current stress. Next

the model is solved by the graphical method of LP to obtain the optimal vector time allocation for capacitor current stress reduction. Further

vector sequences with the non-action characteristics of single-phase switching devices are designed for three modes: leading vector

lagging vector

and conventional vector modulation. Finally

the analysis and experiments show that the proposed method can achieve the theoretical minimum capacitor current stress for three-phase half-bridge motor drives. Compared with the conventional method

this method can reduce the capacitor current stress by about 30% at a high power factor.