Interconnection Technology for Engine Generators

The development of the 1 kW-class inverter unit with a small engine generator that conforms to “Guideline for the interconnection technology requirements” has succeeded. To connect distributed electrical sources such as wind power generation, photovoltaic generation, or cogeneration to the utility grid, it is necessary to detect demand-side problems including the distributed sources (short circuit, ground fault, troubles in generated voltage or frequency) and to detect problems in the grid (power failure and troubles of voltage or frequency). It is also necessary to protect electric power systems, distributed sources, and electrical appliances. The inverter unit uses both passive and active islanding detection methods. Total distortion factor is reduced to less than 1% by applying two kinds of input current to the power supply unit. Efficiency of the interconnection inverter unit has achieved 91% and total efficiency of power generation of the cogeneration unit has achieved 20%.