Connection requirements and Grid Codes for distributed generation

Traditionally, most of the generation plants in the countries all over the world are constituted of big hydro or thermal generating units, which are subjected to grid codes minimum requirements concerning their operation either in normal or under emergency conditions. Such minimum requirements are intended to guarantee reliability and an economic and safe operation. With the rising of new renewable energy generation plants, different kinds of generation units are being introduced in the power systems. The characteristics of these new generation units are still being modeled in order to allow its correct representation in transient and dynamic studies. Due to environmental demands, there has been an increase of clean energy projects, including wind farms, small hydroelectric plants, biomass, micro-turbines, photovoltaic, fuel cells and other kinds of generation, with a growing penetration degree into the power systems. In Brazil this penetration degree is not high yet, but the trend for new distributed generation in the country is growing very fast. It is foreseen that in the next five years, only bio-mass distributed generators in Southeastern Region will reach 10.000 MW, which will represent 10% of total installed capacity in the country. Challenges will have to be faced due to seasonal bio-mass production along the year, mainly when the amount of this kind of generation become significant. Another example is the Brazilian eolic generation program - the Ministry of Mines and Energy is promoting an auction in the second semester of 2009 for the integration of an appreciable pack of eolic energy, remarkably in the Northeastern region of the country. Concerns on the operation of these new generation units together with traditional generation units in terms of guaranteeing that such new generation units will not be shut off during disturbances due to frequency or voltage sags, as well as concerns on the spinning reserve, are examples of new challenges that should be fa- ced in this new environment.