In this paper, the theoretical study and comparison between the a-b-c Hysteresis PWM technique which is proposed in 1] at 1997 and 3 Dimensional (α-β-0) Hysteresis PWM which is proposed in [2] at 1998 are performed for 3-Phase 4-Wire 3-Leg Center-Split Power Quality Compensators. There is description on dc voltage variation control in the a-b-c Hysteresis PWM technique, however, no description of dc voltage variation and no determination of error bands are performed for 3-Dimensional (α-β-0) Hysteresis one. In this paper, a novel 3-D Hysteresis Control is proposed with dc voltage control by the concept of keeping the same overall error bounded volume with higher the dc control ability.