Consequences on Ringhals Operation from Introduction of Adjacent Offshore Wind Power

Abstract

Abstract As of the 16th of May, two offshore wind power plants (WPPs) located outside the coast of Halland was granted approval from the Swedish government. The combined installed capacity of the WPPs is expected to be over 1500 MW, and both prospectors were planning to connect to the same transmission lines that Ringhals power plant are utilizing, however when the approval came from the Swedish government only one of the projects were approved a large enough capacity to connect to the transmission grid. This has not been taken into account throughout the project so instead both WPPs are aggregated into a single power plant in this project. This report investigates possible electrical phenomena inherent to large scale WPPs that may affect the operation of a close by thermal power plant. A literature review was conducted which indicated subjects of interest, four key subjects were chosen to study further, namely harmonic emission, sub-synchronous oscillations, behavior during fault and abnormal grid states, and finally, inter-area oscillations. Through further literature analysis, the findings showed that harmonic emission should be manageable, while sub-synchronous oscillations could pose an issue given a situa tion of weakened grid and poor damping techniques. It was also found that there is a minor risk that an introduction of a WPP could increase the risk of inter-area oscillation. Dynamic phenomena was studied though extensive simulations in PSS/E, the simulations indicate that the grid, in its current condition should be able to sustain the impact of a sudden disconnection of a WPP without serious voltage deviations, and that the critical fault clearing times of the generators at Ringhals could either increase or decrease from an introduction of a WPP, depending on if the WPP rides through the fault or if it disconnects from the grid and if it injects any fault current or not. For cases were the WPP disconnects from the grid during fault the critical fault clearing time at Ringhals decreases noticeably whereas strong fault current injection from the WPP can increase the critical fault clearing times for the closest generator.