This paper firstly verifies the relationship between reactive power compensation and unbalanced load compensation in three-phase three-wire system. In order to give full play to the effect of power capacitors, compensation ability and optimal parameter configuration for delta-connected capacitor bank to compensate reactive current and negative-sequence current are analyzed under unbalanced load. Dynamic Capacitor (D-CAP) is equivalent to continuously adjustable capacitor when duty ratio ranges from 0 to 1. Applying theory analysis about delta-connected capacitor bank on delta-connected D-CAP, an optimal compensation strategy is proposed to compensate reactive current and negative-sequence current as much as possible. Finally, simulation results verify the effects of optimal parameter configuration and control strategy of D-CAP.