Grid code testing of full power converter based wind turbines using back-to-back voltage source converter system

Paper in proceeding, 2013

This paper presents an alternative approach of grid code testing for wind turbines (WTs) using back-to-back Voltage Source Converter (VSC). In particular, this paper focuses on grid code analysis for WTs, and low voltage ride through (LVRT) testing for full power converter (FPC) based WTs. Recent European grid codes are analyzed and selected for testing according to their strictness and wind power penetration in each country. The investigated testing setup consists of a 4 MW FPC-based WT and an 8 MW back-to-back VSC system, operated as a test equipment. The effectiveness of the investigated grid code testing method is validated using the simulation tool PSCAD/EMTDC, where the electrical systems of the WT as well as the test equipment are modeled in detail. A control strategy for the WT is given; in addition, hardware and control algorithms for the converter-based test equipment are described, with special focus on their limitations for testing procedures. The results demonstrate the capability of the investigated testing device in producing a controllable voltage dip at the terminals of the WT, at the same time that is being fed with short circuit currents. Moreover, its flexibility in emulating the behavior of the grid in continuous and dynamic condition is highlighted and discussed in extent.