Study on electricity transmission systems for offshore wind power
Tutor / director / evaluatorLi, Zuyi
Document typeMaster thesis (pre-Bologna period)
Rights accessRestricted access - author's decision
This project presents the main features of each of the electricity transmission technologies available for offshore wind power and discusses their advantages and disadvantages in terms of technical, economic and environmental aspects. The transmission options studied are High Voltage Alternating Current (HVAC) and High Voltage Direct Current (HVDC). Within the HVDC there are two transmission technologies available, the classical Line Commutated Converter based HVDC and the most recently developed Voltage Source Converter based HVDC. As technical features, both operational and implementation issues are analyzed. Flexibility of control of active and reactive power or capacity to provide reactive power support are examples of the first, and size of offshore substation is an example of the latter. Cost-effectiveness and system losses are compared to derive a general rule for the best transmission option from the economic point of view and environmental concerns are also addressed. This enables reader to have a general overview of the factors that affect the decision of using one transmission technology or the other. The second part of the project is centered in the modeling and simulation of a particular case study using HVDC and HVAC. The studied system consists of a Full Scale Converter (FSC) based wind farm which is located 50 km off the shore. The wind farm has a rated power of 100MW which needs to be transmitted to the onshore grid either via VSC based HVDC or HVAC. Two models are built in order to learn about and implement the control systems of the converters. A detailed explanation on the control system design is included. Special attention is given to control strategies to comply with grid regulations related to fault ride-through capability and reactive power support. German Grid Codes are chosen as reference. In the case of HVDC reactive power support is performed by the grid-side VSC of the HVDC system, whereas in the case of HVAC it is performed by the grid-side converters of the wind turbines. Strategies to reduce the electrical power generated by the wind farm in case of fault on the onshore grid include a chopper placed on the HVDC link for the HVDC solution and a chopper placed on the wind turbine converter’s DC link for the HVAC solution.
|Final Report Aina Lleonart.pdf||Report||3.252Mb||Restricted access|