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Since photovoltaic generators (PV) have been mainly introduced in residential areas, it is necessary to consider the consequences of setting up large numbers of PVs locally. In such a situation, it will be difficult to manage the voltage in distribution lines, because the reverse power supplied from the PV raises the voltage of the power lines. In this study, a large PV system was connected to a distribution system, and for every inverter the authors used simulations to verify the appraisal of systematic voltage and the electric power generation. As a result, the authors verified that power factor control is more effective than output control. In addition, the authors verified that with each user the power generation becomes more unequal. In the future, when a large PV system is connected to a distribution system, the problem of unsatisfactory equalization of demand for home appliance usage may arise. A method for determining the set value for the inverter for each user was proposed in order to solve this problem, and the effectiveness of the proposed technique was verified through simulations. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 91(10): 46– 58, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10166

In recent years, distributed resources such as photovoltaic power generation system or wind-turbine generator system are increased, therefore the distributed resources which connect to distribution networks are increased gradually. Under the situation there are several problems such as expansion of the voltage fluctuation, increase of the short circuit current, increase of harmonics phenomenon which we have to consider, and the problems make us difficult to examine the effect of interconnection and to design the distribution system. However, analysis support system to evaluate the influence to connect distributed resources to low voltage distribution system has not developed.Therefore We have developed the analysis system for low voltage for low voltage distribution systems. We can evaluate the influence of distributed resources accurately, examine the interconnection and design the configuration of distribution networks by using the analysis system. In this paper, the concept of the analysis system, the load flow method for unbalanced V-connection 3-phase 4-line distribution system and the calculation method for the connectable capacity of distributed resources. Outline of the man/machine interface and examples of calculation results for sample network are also described.