Fundamental Study on Control and Operation of Innovative Electric Power Distribution System with a Large Penetration of Distributed Generations

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In this research, we focus on abnormal voltage profile on distribution feeder, distribution system instability, unstable operation of power converters of distributed generations (DGs) caused by their mutual interference and the system frequency deviation in distribution system into which a lot of rotating machines such as synchronous generator, generating facilities with power converters such as photovoltaic generation, a kind of wind power generation, microgas turbine generation and fuel cell and power electronics based power flow controllers such as FACTS devices will be connected. For solving the above problems maintaining the current power supply reliability and cost performance, new operation, control and planning methods of the distribution system were proposed.First, a new method to control abnormal voltage profile on a high-voltage feeder with a large penetration of photovoltaic generations and wind power generations by using FACTS devices was proposed and the control performan … More ces of some kinds of FACTS devices were compared from viewpoints of their locations and minimum required capacities.Second, in order to suppress the system frequency deviation caused by a large penetration of wind power generations, a large capacity of energy stored battery was proposed to be introduced to the grid. An effective method for evaluating the minimum required MW and MWh capacity for the appropriate frequency control was developed here.Third, an introduction of superconducting generator (SCG) into the distribution system, that is, replacement of the conventional synchronous generator by SCG in the distribution system was considered for stabilizing the system unstable phenomena originating from the rotating synchronous generator and the feeder voltage fluctuation.Last, digital type of three-phase instantaneous-valued network simulator for distribution system with a lot of distributed generations was developed and was used for off-line simulation of demand-supply control in micro-grid system. This simulator is helpful for analyzing unstable operation of DG converters caused by their mutual interference and for developing the stable operation method. Less