In this paper, a Z-source inverter (ZSI) and back to back connected Z-source inverter (BB-ZSI) are presented for power quality (PQ) upgrading in a power distribution network (PDN). It is noticed from previous research that the ZSI has some drawbacks like low voltage boost gain and weak active power filtering. But BB-ZSI possesses a high modulation index and stronger voltage boost inversion ability. Compared to ZSI, BB-ZSI supports a common dc link voltage for both back to back connected ZSIs. This research work analyses the PQ enhancement capability of ZSI and BB-ZSI based distribution static compensators (DSTATCOM) like supply side distortion reduction, enhanced voltage regulation, reduced switching losses, power factor (p.f) correction and balanced system voltage. Both ZSI and BB-ZSI are operated using adaptive least mean square (ALMS) control techniques which reflect the enhancement of PQ and reliability. The theoretical studies of the BB-ZSI show a close match with simulation results with the help of MATLAB-Simulink software capturing the reflection of the paradigm value of the IEEE grid code.