Islanding-operation prevention apparatus, and dispersed power generation apparatus and power generation system using the same

摘要

Even when a plurality of dispersed power generation systems are connected to a utility gride, an islanding-operation prevention apparatus can easily and assuredly prevent an islanding operation of each dispersed power supply constituting the corresponding dispersed power generation system. The apparatus includes a breaker provided between the utility gride and a dispersed power supply, an electric-power-value detector for detecting a value of electric power from a power line connected to the utility gride, a switch for electrically connecting or disconnecting an electric-power changing device for changing the value of electric power to the power line in accordance with an output from a pulse circuit, and a controller for controlling the breaker in accordance with the width of fluctuations of the value of electric power during the connection or the disconnection. A dispersed power generation apparatus and a dispersed power generation system uses such an apparatus. By further providing a synchronous circuit for synchronizing the output of the pulse circuit with a signal output from a reference-signal source, even if the amount of the generated power and the amount of a load are in a complete equilibrium state during an islanding operation, the islanding operation can be assuredly prevented with a short time period until the stop of the islanding operation and without using large-scale equipment.