Research Projects

The present-day large-capacity wind farms usually consist of large number of megawatt-size distributed wind turbine generators (WTGs). The output powers of these WTGs are collected at the medium voltage collector substation through intricate collector lines and further transmitted to the grid through outgoing high voltage transmission lines (HV-TLs). The doubly-fed induction generator (DFIG) is currently the most popular wind generator due to its numerous technical and economic benefits. With the growing penetration of wind power into the grid, the latest grid codes require these WTGs to remain connected to the grid in the presence of grid voltage sags caused by faults in the wind farm collector lines or in the outgoing grid TLs and supply reactive power to the grid. However, the DFIG wind farms with low-voltage ride-through (LVRT) capability have quite different fault characteristics compared to the conventional synchronous generators. As a result, the conventional relaying schemes used for the protection of medium voltage collector lines as well as the outgoing HV-TLs are under more scrutiny. Currently, emphasis is given mainly on the development of advanced protection scheme for wind farm outgoing HV-TLs. But the research on the development of advanced protection schemes for wind farm collector lines are relatively rare. In fact, chances of fault occurrences are more in the collector lines compared to the HV-TLs and also, the protection of collector lines is more challenging especially when cables are used rather than overhead lines. The presently used single end overcurrent relaying scheme for wind farm collector line protection has selectivity problem especially during single phase-to-ground faults due to the ineffectively grounded neutral of the wind farm collector grids resulting disconnection of large number of adjacent non-faulted collector lines. Unintended tripping of large number of WTGs may affect the stability of the power system. Considering the complex fault characteristics of large-scale DFIG-wind farm with LVRT capability and the different topology of wind farm collector lines, instead of using simple single end protection methodology, the present project aims to develop a communication assisted double ended advanced intelligent relaying algorithms for solving the aforementioned problems. The present project will concentrate mainly to develop an improved protection scheme for fast and reliable detection, classification and location estimation of faults in large-scale DFIG-wind farm collector lines using both-end synchronized voltage and/or current measurements through the employment of advanced communication facility. The relaying algorithm proposed in the project will be validated on data simulated on different test systems through PSCAD/EMTDC and/or MATLAB/Simulink software and OPAL-RT manufactured real time digital simulator.