Cyber Times International Journal of Technology & Management

The increasing consumer demand and government incentives are driving the rapid growth of renewable energy generation. In particularly, the number of distributed photovoltaic (PV) system installations is increasing quickly. However, the high cost of the PV systems and he potential impacts on the safe operation of utility grid could become barriers to their future expansion. To enable the high penetration of distributed PV systems, it is necessary to bring down the PV system cost and mitigate its adverse impacts on utility grid operation. As the interface between the renewable sources and the utility grid, advanced power electronics technologies will play important roles in realizing the above goals. The paper present a single-phase grid-connected transformer less photovoltaic (PV) module-integrated converter (MIC) based on cascaded quasi-Z- source inverters (qZSI).In this system ,each qZSI module serves as an MIC and is connected to one PV panel .Due to the cascaded structure & qZSI topology ,the proposed MIC features low-voltage gain requirement , single-stage energy conversion ,enhanced reliability & good output power quality. Furthermore, the enhancement mode gallium nitride field-effect transistor (eGaN FET’s) are employed in the qZSI module for efficiency improvement at higher switching frequency. It is found that the qZSI is very suitable for the application of eGaN FETs because of the shoot-through capability. Optimized module design is developed based on the derived qZSI ac equivalent model and power loss analytic model to achieve high efficiency and high power density .A design example of qZSI module is presented for a 250-Watt PV panel with 25-50 o/p Voltage. The simulation & experimental result prove the validity of analytical models. The final module prototype design achieves up to 98.06% efficiency with 100 kHz switching frequency. The peak efficiency can be further improved to 98.66% with synchronous rectification. Though the transformer less CMI based PV systems can achieve high performance and low cost.