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Newton-raphson based load flow analysis of AC/DC distribution systems with distributed generation

Kaya, Ferhat Emre
Increasing concerns about climate change and global pollution rates emphasized the importance of renewable energy resources. Rising pressure to utilize green energy alternatives requires some changes and rearrangements on the available alternative current (AC) oriented electric power system. Moreover, electric charging stations, renewable and distributed electricity sources like battery storage systems, solar power plants use direct current (DC) and additional power conversion is needed for their integration into the current distribution network. This explains why hybrid AC/DC smart grid concepts are developed. Although there are various load flow analysis approaches applied on hybrid AC/DC transmission systems, not much work is proposed at the distribution system level. The scope of the thesis is to develop an integrated load flow approach for AC/DC distribution networks, which include a variety of power electronic devices as well as distributed energy sources. In the method presented, AC and DC power flow equations are combined and solved using Newton-Raphson algorithm with a modified Jacobian matrix. Commonly used DC/DC converters and voltage source converters present in the grid are represented with their respective models. This load flow calculation method is implemented on MATLAB and simulations are performed for different distribution test systems, which utilize a variety of converter models and load profiles. Solution of the proposed load flow algorithm has shown consistency with the results obtained by other approaches.