Investigations and performance enhancement of transformerless photo voltaic inverter

Abstract

The present day s photo-voltaic (PV) installation and its application including grid connected system are matured. Beside safety necessities compulsory by the electrical supplier. Even through there are several transformerless inverter topologies are nowadays developed, they do generate constant common-mode voltages and hence the leakage current elimination is quite difficult. In order to meet the safety prerequisites for PV tied transformerless inverter grid system, the leakage current has to be attempted carefully through maintain the constant Common Mode Voltage (CMV). The multilevel inverter has given a grate advantages then conventional twolevel inverter, since it is producing the constant CMV. Out of two types of basic Neutral Point Clamped (NPC) - multilevel (MLI) topology, the T-type NPC-MLI is gave a lesser switching loss then I-type NPC-MLI. The T-type NPC-MLI does not uses the clamping diode and hence it has produced the better efficiency. A family of single-phase transformerless inverter full bridge topologies are developed with same idea of NPC-MLI with including the existing oH5 and some new topologies and it has a low-leakage current. Even though this topology is giving similar performance by comparing the NPC topology, the number of switches used, reliability and cost is high. One of these topologies are using the bipolar pulse width modulation However, bipolar pulse width modulation causes huge current ripple and suffer with higher switching losses, and hence inverter overall efficiency become agonized. Besides, this inverter topology would not avoid the injection of DC-link current into the grid. Hence, the new diode-free transformerless MLI topology can be defined to dealt the leakage current mitigation for the more attentions in PV grid connected system with feature high efficiency and low cost. The transformerless inverter topologies have given much interest in PV based power generation system as it had high efficiency and less installation cost. This inverter topologies highly suffered with