Research On Configuration Optimization Of Distributed Generation Based On Voltage Influence And Hybrid Energy Storage

In recent years,more and more Distributed Generations(DGs)have been connected to the grid.The problem of voltage quality caused by improper configuration of DG has attracted wide attention of electricians.Based on voltage level and taken the hybrid energy storage into consideration,configuration optimization of DG has been deeply studied in the thesis.Firstly,from the theoretical point of view,the main factors that influence the voltage profile are the location,capacity,power factor and number of DG,the main factors affecting the voltage fluctuation are the capacity of DG and line impedance,and the static voltage stability is studied.Then,DG and energy-storage components are modeled.The voltage profile and static voltage stability belong to the field of steady-state research,DG model can be equivalent to the ordinary power supply;so static generator is choosed to research the steady-state voltage in the thesis;voltage fluctuation is a kind of transient study,DG model needs to reflect its intrinsic characteristics.In the small time scale,the output power of photovoltaic power generation is more fluctuating,it is selected as the example of DGs to study the voltage fluctuation in the thesis.The photovoltaic power generation model is built by DIg SILENT,and the correctness of the model is verified by simulating its output characteristics.The energy storage components including super capacitor and battery are analyzed theoretically,modeled,simulated and verified.Then,the influence of location,capacity,power factor and number of DG on the voltage profile is simulated and analysed.It is pointed out that DG can improve the line voltage,but the problem of voltage overrun can be caused by improper access of DG.The change conditions of monotonicity of voltage profile are verified.The voltage fluctuation is simulated when photovoltaic power system is on and off,and its output power changes in accordance with the actual light intensity.The results show that voltage fluctuation of the common connection point is the most serious.The voltage fluctuation standard is more stringent than the voltage deviation to a certain extent.In order to increase the capacity of DG,it is necessary to suppress the voltage fluctuation.The influence of DG's location,capacity,power factor and number on static voltage stability are simulated and studied.It is pointed out that DG's access can effectively improve line static voltage stability.Finally,the configuration optimization of DG based on voltage improvement is studied.The static voltage stability and network loss are taken as the goals,and the voltage constraint is considered.The optimal location and capacity of DG are determined by genetic algorithm.And a numerical example is given to verify the correctness of the algorithm.In order to increase capacity of grid-connected DG,the hybrid energy storage system is used to suppress power fluctuation of DG.The battery is used to bear the low-frequency components of the power fluctuation,and super capacitor is used to bear the high-frequency components of the power fluctuation.Thereby the voltage fluctuations are suppressed to make the access of large capacity of DG possible.