Atif Iqbal (Keynote Speaker for PSE)

Grid-Connected Renewable Energy Sources-Challenges and Trends

The world is moving towards decentralized power station, formally called distributed power generation. The main sources of distributed power generations are Solar Power and Wind Power systems. Among solar Power sources, solar photovoltaic has received much attention.

Wind energy is also one of the most important and promising sources of renewable energy, mainly because it is considered to be non-polluting and economically viable. At the same time, there has been a rapid development of related wind turbine technology. The current surge in wind energy development is driven by multiple forces in favor of wind power. These include tremendous environmental, social and economical benefits, technological maturity, deregulation of electricity markets throughout the world, public support, and governmental incentives. Recent developments in wind power generation have provided an economically competitive and technically sound solution to reduce greenhouse gas emissions. The conversion efficiency of the wind power plant is much higher compared to the solar PV system and this can be further enhanced by employing appropriate maximum power point tracking strategy. According to Betz limit, the conversion efficiency of a wind power plant is as high as 59.3%.

Grid-connected photovoltaic (PV) systems are one of the fastest growing renewable energy conversion systems in the world. In fact it has increased more than 7 times in the in recent past (from 5.4GW to 40GW of installed capacity). The main reason for this remarkable development is the cost reduction of PV modules and the introduction of economic incentives or subsidies due to growing environmental concerns. This has made PV generated electrical energy cost-effective and competitive in some regions of the world with good sun radiation conditions. Projections show that PV technology costs will continue declining in the next decade, making large-scale PV systems more and more attractive.

Power electronics, used as an interface between the distributed generation sources and the electricity grid play an important role in facilitating an efficient and optimal energy transfer, as well as increasing system reliability and utilizing an economically viable solution. However, despite the clear trend in the increase of power rating of PV plants, power converter interfaces for large-scale PV systems have not evolved much and are concentrated in a couple of system configurations and converter topologies.

The talk will focus on the energy scenario, existing international standards in relation to the grid-connected distributed energy source, existing inverter topologies, their classifications and operations. The control of grid connected inverters and synchronization requirements. The present challenges and requirements related to grid-connected inverters is presented. The issue related with Partial shading and MPPT requirement is discussed in the talk. The new class of PV inverters namely Z-Source, quasi Z Source and their cascaded structure is elaborated. The future directions of research is also given.