Projects

Grid Integration of Renewable Energy Sources with Power Quality Improvement

Global electrical energy consumption is steadily increasing and there is a necessity to increase the power generation capacity. Conventional power generation schemes have serious environmental issues like climate change, high oil price, and water and oil pollution. These issues are the major drive for the search for new sustainable energy sources. The solution to this problem could be renewable energy sources, which provide significant percentage of required installed capacity addition and also eliminates the harmful emissions from the conventional power generation sources. The availability of renewable energy sources are completely based on daily and seasonal patterns. But the power required by the consumers could have very different characteristics than renewable energy sources. Therefore, it would be very difficult to operate a power system installed with only renewable generation units due to the characteristic differences and the high uncertainty of the availability of the renewable sources. The way of fully exploiting the renewable energy is by grid connection, normally at distribution level. The introduction of renewable energy source to the distribution system will have a significant impact on the customers and utility equipments. The utility is concerned due to high penetration level of renewable energy sources in distribution systems as it may pose threat to power system in terms of stability, voltage regulation and power quality issues. The recent development in interfacing of renewable energy source to distribution supply (grid) have been proposed with shunt active filter which can simultaneously compensate for problems like power factor correction, current unbalance and current harmonics and also inject energy generated by renewable energy power sources to grid with a very low THD. Even when there is no energy available from the power source (when there is no sun or wind) the shunt active filter can still operate, increasing the power quality of the electric grid. To provide better efficiency and to meet the required interconnecting standards a well designed controller is necessary. In this regard controllers play a very important role and control strategies applied to grid integration converters are gaining more importance. Though functionally effective, control algorithms reported in literature involve multiple computations and complicated circuitry while trying to make the algorithms adaptable to balanced, unbalanced and non-linear load conditions. It is thus seen that the need exists for the development of a Shunt Active Filter interfacing Unit with a simple and efficient controller using minimum computational steps and simple circuits, which can be applied to practical system conditions like balanced, unbalanced and non-linear loads under steady state and transient switching conditions. This research expounds the work done by the author on integration of renewable energy sources with grid at distribution level, by developing a Shunt Active Filter as an Integrating Unit for Renewable Energy Source with an efficient Controller, so as to reduce the burden on the grid by properly utilizing the available renewable energy and also taking care of current harmonic compensation, power factor correction and reactive power compensation. A cost effective and efficient three phase shunt active filter interface unit for renewable energy source – grid integration with two newly proposed controllers namely ‘IRPT Controller for Shunt Active Filter based RES-Grid Interface Units’and ‘ICosɸ Controller for Shunt Active Filter based RES-Grid Interface Units’, is proposed. Prototypes for the same are designed, simulated and tested for linear/non- linear, static/dynamic loads under steady/transient conditions.To improve the performance of the renewable energy source side power conditioning, author has also proposed a new topology for the DC-DC converter which is a cascade of buck-boost converter and high step-up converter. The high DC bus voltage with higher voltage conversion ratio is obtained using hybrid switched capacitor technique. This proposed topology results in the reduction of voltage stress of semiconductor devices to half of the output voltage. Through the project we designed and developed a laboratory prototype of the proposed three-phase shunt active filter interface unit for renewable energy source-grid integration and also the DC-DC converter topology at the input side of grid interface converter. The same has been tested with the newly proposed ‘ICosɸ Controller for Shunt Active Filter based RES-Grid Interface Units’ using analog circuit implementation for various linear/ non-linear static/dynamic loads under steady/transient conditions. This research was funded by DST-SERC scheme for Young Scientists under Fast Track scheme.