The power quality issues are very high in the modern-day distribution network. The power quality issues are mainly caused due to unbalanced networks, faults, coordination mismatch between the control stations, high usage of the power electronic devices due to these problems the issues like voltage sag, swell and harmonics are presented in the distribution networks. To avoid the power quality issues the custom power devices (CPD’s) are incorporated in the distribution networks. This paper presents a review on the different types of CPD’s present in the system. Here the distributed static compensator (DSTATCOM), dynamic voltage restorer (DVR), unified power quality conditioner (UPQC) are presented. In this paper, the detailed review is given for these devices based on their topologies (depends on the structure of the device), control algorithms and controllers. For the distribution network the optimal sizing and to identify the location of the devices are explained with different types of optimization techniques. Finally, a case study has been done on these CPD’s, for this the IEEE-33 bus system has been taken and which CPD is showing better performance in terms of voltage compensation and harmonic reduction has been done. © 2020 IJSTR.