Abstract
Abstract. The electrical test and assessment of wind turbines go hand in hand with standards and network connection requirements. In this paper, the generic structure of advanced electrical test benches, including grid emulator or controllable grid interface, wind torque emulator, and device under test, is proposed to harmonize state-of-the-art test sites. On the other hand, modern wind turbines are under development towards new features, concerning grid-forming, black-start, and frequency support capabilities as well as harmonic stability and control interaction considerations, to secure the robustness and stability of renewable-energy-based power systems. Therefore, it is necessary to develop new and revised test standards and methodologies to address the new features of wind turbines. This paper proposes a generic test structure within two main groups, including open-loop and closed-loop tests. The open-loop tests include the IEC 61400-21-1 standard tests as well as the additional proposed test options for the new capabilities of wind turbines, which replicate grid connection compliance tests using open-loop references for the grid emulator. In addition, the closed-loop tests evaluate the device under test as part of a virtual wind power plant and perform real-time simulations considering the grid dynamics. The closed-loop tests concern grid connection topologies consisting of AC and HVDC, as well as different electrical characteristics, including impedance, short-circuit ratio, inertia, and background harmonics. The proposed tests can be implemented using available advanced test benches by adjusting their control systems. The characteristics of a real power system can be emulated by a grid emulator coupled with real-time digital simulator systems through a high-bandwidth power-hardware-in-the-loop interface.
Highlights
Wind energy has been one of the most promising renewable energy sources used worldwide, mostly located onshore
New interconnection requirements, standards, and market mechanisms are evolving in various parts of the world for variable renewable generation (VRG), including wind power, to provide various types of essential reliability services to the power systems – the role that has been typically reserved for conventional generation (NERC, 2015)
As the AC system impedance increases, the voltage magnitude of the AC system becomes even more sensitive to the power variations at the point of common coupling (PCC). This dependency is usually determined by the short-circuit ratio (SCR), which is a ratio of the short-circuit capacity (Ssc) versus the rated power of the AC grid at PCC (Pnpcc) as illustrated in Eqs. (1) and (2) (IEEE Std. 1204, 1997)
Summary
Wind energy has been one of the most promising renewable energy sources used worldwide, mostly located onshore. Nouri et al.: Generic characterization of electrical test benches for wind power plants required to ensure the power quality and stable operation of VRGs, especially WPPs. The development of European network codes and IEC standards are two of best harmonization practices in wind energy. The operation and stability of VRG-based power systems depend on the interoperability and capabilities of the individual power-generating systems such as wind turbines (WTs) In this way, the state-of-the-art WTs are under development towards advanced features, especially grid-forming and black-start capabilities. The authors aim to extend the state-of-the-art developments in wind energy towards harmonized test methods and propose additional test options to the standard tests to extend the applications of advanced industrial test benches regarding operation and stability assessment of WTs as well as WPPs. In Sect.
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