Transformer Based FRT Test Unit Becomes Common.

Three medium voltage transformer-based test units for Fault Ride Through (FRT) tests are already in operation. Others are in planning or in process of building. The new users are impressed of the wide range of possibilities for testing with a smarter test device. The increasing requirements of accuracy in model validation of the devices under test (DUT) caused the requirements that as well the test unit itself needs a better description. This paper will serve mathematic approaches how to handle this kind of network fault generator in the computer simulation area. FRT test devices in general were taken to demonstrate that real wind turbines or other DUT are able to handle grid faults. In this context a grid fault is a 2 or 3 phase instantaneous voltage drop or rise over some 100 ms up to not more than 3 s usually. The way how a DUT has to handle this grid faults is postulated in the grid codes of each system operator or in general country grid codes. In Europe the network code requirements for generators and in Germany the VDE AR N 4105, -4110 and -4120 in conjunction with the measurement procedures of FGW technical guideline TR 3 and DIN VDE 0124-100 are setting the standards. Compared to previous years, not only voltage drops need to be simulated but also overvoltage events up to 150%voltage. Long term measurements with voltages of 115% or 85% have a test duration of up to 60 s. The new IEC 61400-21-1 proposes to measure not only the requirements according to the grid codes. The suggestion of the new IEC 61400-21-1 is, to simulate the maximum capabilities of the wind turbines. These capabilities can be far beyond the mentioned test. To meet these new requirements a new generation of FRT test equipment was developed. [ABSTRACT FROM AUTHOR]