First comparison of the electrical properties of two grid emulators for UVRT test against field measurement

Abstract

The technical rules for connecting turbines to the medium, high or extra-high voltage grid in Germany require the certification of the UVRT characteristics of wind turbines. The state-of-art voltage divider-based test equipment, also named UVRT-Container, is well equipped for executing UVRT tests in field. To conduct the UVRT in field the full wind turbine should be already installed. A second option to perform UVRT tests are system level test benches. They enable the testing of the nacelle. The components that are not actually present, such as the turbine tower or the blades, are emulated via a mechanical hardware in the loop (HiL) system. In this work, for the first time, the performance of two different grid simulators installed at the DyNaLab at Fraunhofer IWES and at the CWD at RWTH Aachen University is compared with a field measurement of the same type of wind turbine. Thus, not only a system test bench measurement is compared to a field measurement. Rather, two system test benches with individual technical approaches are additionally compared with each other. The focus of this work is to investigate the characteristics of the grid simulators within the steady-state range of the UVRT tests to replicate identical fault shapes on the test benches and in the field.

Medium-Voltage Megawatt Power-Electronic-Based Grid Emulators: Testing Capability Requirements and Dynamics Challenges—A Review

“…In addition, the X/R ratio is another critical parameter for the grid impedance. In the FGW TR3, DUTs are required to stably operate at a minimum SCR of 2 and an X/R ratio of at least 3 [7], [39]. Recently, a more stringent requirement has been introduced by AEMO, i.e., the minimum SCR and X/R ratio are reduced to 1.5 and 2, respectively [40].…”

“…Fig. 5(b) shows the time sequence of the voltage-magnitude changes and the impedance variation [7], [43], [44]. Hence, the MFRT test can be realized by shunting multiple impedances [5].…”

“…(a) Shunt-impedance-based grid emulator [22]. (b) Time sequence of impedance variation and voltage-magnitude changes [7].…”

Influences on the LVRT behavior of DFIG wind turbine systems

“…The concept of a certification process using a system test bench was investigated in the research project CertBench [7]. In this project the LVRT behavior of a WT on two different test bench setups are compared to field tests [8]. They have shown that the test bench results are comparable to field test results, if proper test setup is followed.…”

Impact of Multi-Physics HiL Test Benches on Wind Turbine Certification

“…This project achieved the worldwide first wind turbine certification, solely based upon test bench measurements by means of the German FGW TR3 guideline. An overview of the results [28], and some results on MHiL- [29] and PHiL-specific [30] aspects have been published already.…”