Research On The Reliability Evaluation Of Distribution Networks Containing Photovoltaic Power Generation

The vigorous development of renewable energy power generation technologies isvital to solve environment and energy problems. Among these renewable energy powergeneration technologies, photovoltaic power generation (PPG), which is pollution-free,widely distributed and easily to operate, becomes pro-gaze around the world. Accordingto the current development, photovoltaic power generation integrated into electricaldistribution network (EDN) has become a trend. As for the research on the reliability ofEDN, photovoltaic power generation brings to the improvement of the reliability ofEDN and new problems as well. The traditional reliability evaluation model andreliability analysis method is incapable of meeting the requirement of the reliabilityevaluation and analysis of distribution network with photovoltaic power generation;therefore, exploring new evaluation approach for the reliability of EDN is of greatsignificance.A reliability evaluation algorithm for END is proposed. Considering the processes,such as fault isolation, fault restoration and switching to standby power in END, and theaction principle of switching devices (SD), concepts and forming algorithms ofreliability level tree (RLT) for sectionalizing switches (SS) and circuit breakers (CB) arepresented. Using the proposed forming techniques, an END can be equivalent to a SStree and a CB tree. A dynamic linked list is used to store the information of reliabilitylevel trees to reduce the redundancy storage and storage complexity. Considering theimpacts of component failures and tie switches on the load point reliability, an unifiedmodel to evaluate the reliability indices of load points is proposed based on thereliability level trees. The proposed algorithm is efficient due to the fact that it has thefeatures of simplifying an END using reliability level trees and only one time up-streamsearch in the reliability evaluation process. The proposed algorithm is applied toevaluate the reliability of RBTS, a practical10kV EDN. Analysis results show that theproposed algorithm is useful to evaluate the reliability of traditional medium voltageEDNs.The impacts of complementary relationship between PPG and EDN, the selectionof interconnection point and access methods on the reliability of EDN with PPGintegrated are analyzed. The empirical distribution model of PPG is constructed usinghistorical data considering its fluctuating and intermittent nature. Based on the island operation characteristic and requirement, the forming scheme and calculation model ofisland is proposed which can determine the state numbers, the scope and the formationprobability of island and then the multi-state reliability model of EDN containing PPGis established.Based on the RLT algorithm and the mulit-state reliability model of PPG, thereliability index revised model and the reliability evaluation algorithm of EDNcontaining PPG are presented. The model divide the evaluation process into two parts,day-mode and night-mode. In the night-mode, the load point reliability index is directlycalculated using RLTA without considering PPG. In the day-mode, the load pointreliability index is calculated under each state of PPG which is equivalent to a backupsupply with constant output. Finally, calculate the system reliability index usingmodified reliability index calculation formula. The reliability of EDN containing PPG indifferent configuration is evaluated.The results show that the proposed algorithm iseffective and can be used to assess the reliability performance of PPG.