A Research On Dispatch Strategy And Planning Of Microgrids Based On Reducing Operational Cost

The electricity grid structure is evolving rapidly in view of contemporary energy policies which ensure the addition of more renewable sources to reduce carbon footprint.Compared to the centralized approach,low voltage grid(decentralized and distributed)are promising approaches to integrate nondispatchable renewable energy sources(RESs).The centralized grids are now being converted to a new paradigm called distributed energy hub to accommodate and integrate different types of energy networks.Installing local micro level power generation sources like fuel cell,microturbine,and energy storage system are a recent trend which helps in intermittent the effect of RESs and makes microgrids less dependable on the main grid.Due to the increasing variety of distributed generation sources having diverse characteristics,power dispatch scheduling of distributed microgrids is getting challenging.A dispatch scheduling solution from an operator's point of view for the microgrids is presented by the author.The dispatch scheduling solution aims to minimize the carbon emissions and the cost of each microgrid.Further,it is observed that sales and purchases from the main grid are reduced.Consequently,transmission losses are also decreased.The author also focuses on the minimization of operational cost and optimal power dispatch associated with microgrids coupled with natural gas networks using particle swarm optimization(PSO).Introducing a natural gas turbine in a microgrid to overcome the drawbacks of renewable energy resources is a recent trend.This results in increased load and congestion in the gas network.To avoid congestion and balance the load,it is necessary to coordinate with the electric grid to plan optimal dispatch of both interactive networks.A modified PSO is used to solve this coupled network problem.To study the proposed approach,a7-node natural gas system coupled with the IEEE bus 33 test system is used.The proposed strategy provides optimal power dispatch.Moreover,it indicates that power sharing between the main grid and microgrid is reduced in such a way that it may help the main grid to shave the load curve peaks.As aforesaid electricity grids structure is evolving rapidly and energy policies ensuring the addition of more RES to reduce carbon footprint but in context to planning and collaboration with main grid,the question “which type of RES and energy storage system and in what ratio as the most suitable?” is unanswered.To answer the question,a number of valid possible arrangements of renewable energy sources(wind turbines,solar photovoltaics)with energy storage systems(electrochemical storage,fuel cell,battery)for the large-scale electric grid system(Pakistan National Grid,26 GW)are explored in this dissertation.There are two core motivations for choosing such arrangements.First,microgrids having the same type of renewable resources located at a single site have high fluctuation,so we model distributed microgrids having various type of renewable resources and located at various locations to have lesser fluctuations accompanied with relatively compact energy storage systems.The second incentive is to find the true minimum cost combination,excluding subsidies and relaxation in taxes for governments.This study includes the whole year(hourly,8760 hours in total)electric load and related weather elements.It is found that the least cost combinations require excessive generation capacity,diverse renewable generation resources,and energy storage techniques,which would meet the load requirements and have less carbon emissions.