Full scale power quality emulation system for testing of low voltage grid components

Power quality and grid stability are gaining importance due to the increasing number of installed power electronic based appliances and distributed power sources. The decreasing amount of rotating masses in electricity grids demands for the implementation of new features into power electronic converters of generation systems to ensure grid stability. This paper presents a method to verify the operation of grid connected equipment, such as solar inverters by means of a power electric converter. In particular, proof of grid stability and extended grid service features need be conducted under real operating conditions. The grid emulator is operating as a controllable source or sink, as it is capable of bidirectional power flow. Possible critical grid conditions, which can be reproduced by the grid emulator, are e.g. voltage / frequency fluctuations, unbalanced phase voltages, reactive power or harmonic currents. Cancelling or injection of harmonic currents are described in earlier work [4]. As an example of a test case, this paper will show the emulation of severe voltage dips in a distribution grid and the response of a commercial solar inverter during energy feeding mode under different operating conditions. Experimental and simulation results will be provided.