Generic Characterization of Electrical Test Benches for AC- and HVDC-Connected Wind Power Plants

The electrical test and assessment of wind turbines (WT) are going hand in hand with standards and network connection requirements. In this paper, the latest developments in the testing of the electrical characteristics of WTs, including IEC standards, compliance test methods, and industrial test benches, are studied. In this paper, the general structure of advanced electrical test benches, including grid emulator or controllable grid interface (CGI), wind torque emulator and device under test (DUT), has been proposed to harmonize the available industrial test sites. The AC and HVDC transmission systems impose different electrical characteristics on wind power plants (WPP). HVDC connection leads to a converter-based grid, yet AC connection has different grid characteristics in terms of grid impedance, short circuit ratio (SCR), inertia, and background harmonics. Therefore, this paper recommends performing compliance tests in two divisions as AC- and HVDC-connected WTs using a converter-based CGI and emulate the corresponding AC grid for DUT. Also, this paper recommends the additional tests for the current version of IEC 61400-21-1. The additional tests consist of test options for new features of modernWTs, such as Grid-forming, system restoration, and black start capabilities, as well as emulation of different grid characteristics, such as detailed power system, inertia, SCR, and different grid connection emulations for DUT. This way, the possibility of research, development, and demonstration studies on WTs and WPPs would increase. The proposed additional tests can be implemented using the available advanced test benches by adjusting their control systems. Since most of the industrial test benches are based on converters, the characteristics of a real power system can be emulated by a CGI coupled with real-time digital simulator (RTDS) systems through high-bandwidth power-hardware-in-the-loop (PHIL) interface.