Power Quality Improvement Using ZSI-DVR

Our power system's main concerns are power quality issues. Voltage sags, swells, flicker, voltage notches, harmonic distortions, transients, and momentary interruptions are examples of such phenomena. These issues are mainly effecting to the industrial customers. Custom power system devices are the most suitable solution to mitigate such issues, which includes D-STATCOM, DVR, UPQC etc. Among them DVR is a better choice due to its better, efficient, reliable operation. Main part of a DVR is the Voltage Source Inverter (VSI) which is supplied by means of a battery or from a DC link capacitor. Basically VSI are buck in action, obtainable output voltage cannot exceed the DC source voltage. For a PV supplied system there is a need of separate DC-DC boost converter in the input side of the VSI. DC-DC boost converter require more switches. This makes the overall system costly and also switching losses and total volume of the system become high. Also whenever the two switches of the same leg is ON it leads to the shoot through (ST) and damages the inverter and reduce its reliability. Impedance source inverter (ZSI) is beneficial to inversion application that demands a high voltage gain from a very low voltage DC source such as Photo Voltaic generation. Voltage boosting, inversion and maximum power point tracking are all accomplished in a single stage with this inverter topology. It has minimized number of switching devices and it utilizes the shoot through state for the boost function. So this paper mainly aims to improve the performance of DVR with the replacement of VSI by a ZSI and UVT-PWM(Unit Vector Template-Pulse Width Modulation) based control algorithm is used as the DVR controller. This paper analyses the voltage compensation performance under voltage sag and voltage swell conditions, also harmonic mitigation performance of the ZSI-DVR were analysed. This paper also aims to compare the performance of ZSI-DVR with performance of traditional VSI-DVR.