MICROGRID TECHNOLOGIES FOR FUTURE OFFSHORE WIND POWER PLANTS

Due to a possible energy shortage and environmental concerns about global warming, increasing efforts have been devoted into the development of sustainable energy sources for electric power generation. Among all the renewable electricity generation technologies, wind power generation is increasingly becoming mainstream, and large-scale offshore wind power plants (OWPPs) are gaining more attention in recent years because of their increased power production capability and low environmental impacts. However, as the wind power penetration level increases, integrating large-scale OWPPs into the utility grid will pose a series of challenges in the realm of reliability and power quality. The extent to which large-scale OWPPs can be integrated into the utility grid without adverse influences on overall reliability and stability mainly depends on the technology available to deal with possible challenges such as power fluctuations of different time scales, overcurrent and overvoltage caused by short-duration grid voltage disturbances, loss of synchronization for grid connection, and the risk of instability due to harmonics.

The aim of this PhD project is to develop new models, tools and methods to improve the performance of integrating large-scale OWPPs into power systems. Complete models of OWPPs with variable-speed wind turbine generators and long transmission cables will be established for stability analysis and simulation validation. In addition, coordinated distributed and centralized control strategies will be investigated to improve the performance of network support under both grid-connected and islanded conditions, and special attention will be paid to realize smooth switching between these operation modes without any modification of control schemes. Moreover, filtering and damping strategies will be developed to mitigate instability problems in large-scale OWPPs, and harmonic current sharing methods will be proposed in a higher layer to adjust harmonic contents on each wind turbine inverter terminal. A hierarchical control structure will be then designed to simultaneously include turbine-, convert- and farm-level control algorithms, and different layers will be defined to cope with OWPPs’ framework, grid code requirements, and different operation conditions such as weak-grid conditions, islanded operations, black-start operations and grid fault conditions.

Funding: China Scholarship Council (CSC)