AC coupled PV hybrid systems and micro grids - state of the art and future trends

The consequent AC-coupling of generators, storage units and loads for setting up hybrid systems or hybrid micro grids is under investigation at ISET since more than ten years. After the development of suitable components like the PV-inverter Sunny Boy¿ and the battery inverter Sunny Island¿ and after the implementation of new control concepts for parallel operation, these systems can be easily set up with series produced components. This paper describes the principals of the Modular Systems Technology and shows some examples of operat-ing hybrid micro grids containing AC-PV, AC-battery power units, wind turbines and diesel gensets. Further developments and aims are described including the dis-tributed generation and energy storage in micro grids as well as the stepwise interconnection of micro grids. A first approach for the control and management of disconnecting houses or grid parts which make use of their distributed energy generators or storage units for emergency power will be outlined.