Search results for: Ruifeng Yan

Authors: Jie Zheng, Ruifeng Luo

Abstract:

The United States is the world’s most developed economy with the strongest military power. China is the fastest growing country with growing comprehensive strength and its economic strength is second only to the US. However, the conflict between them is getting serious in recent years. President’s address is the representative of a nation’s ideology. The paper has built up a small sized corpus of President Xi Jinping and Trump’s speech in Davos to investigate their respective use and types of metaphors and calculate the respective percentage of each type of metaphor. The result shows President Xi Jinping employs more metaphors than Trump. The metaphors of Xi includes “building” metaphor, “plant” metaphor, “journey” metaphor, “ship” metaphor, “traffic” metaphor, “nation is a person” metaphor, “show” metaphor, etc while Trump’s comprises “war” metaphor, “building” metaphor, “journey” metaphor, “traffic” metaphor, “tax” metaphor, “book” metaphor, etc. After investigating metaphor use differences, the paper makes an analysis of the underlying ideology between the two nations. China is willing to strengthen ties with all the countries all over the world and has built a platform of development for them and itself to go to the destination of social well being while the US pays much concern to itself, emphasizing its first leading position and is also willing to help its alliances to development. The paper’s comparison of the ideology difference between the two countries will help them get a better understanding and reduce the conflict to some extent.

Keywords: metaphor; corpus; ideology; conflict

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Authors: Ting Kai Chia, Ruifeng Yan, Feifei Bai, Tapan Saha

Abstract:

This research presents a real-world power system oscillation incident in 2022 originated by a hybrid solar photovoltaic (PV) and wind renewable energy farm with a rated capacity of approximately 300MW in Australia. The voltage and reactive power outputs recorded at the point of common coupling (PCC) oscillated at a sub-synchronous frequency region, which sustained for approximately five hours in the network. The reactive power oscillation gradually increased over time and reached a recorded maximum of approximately 250MVar peak-to-peak (from inductive to capacitive). The network service provider was not able to quickly identify the location of the oscillation source because the issue was widespread across the network. After the incident, the original equipment manufacturer (OEM) concluded that the oscillation problem was caused by the incorrect setting recovery of the hybrid power plant controller (HPPC) in the voltage and reactive power control loop after a loss of communication event. The voltage controller normally outputs a reactive (Q) reference value to the Q controller which controls the Q dispatch setpoint of PV and wind plants in the hybrid farm. Meanwhile, a feed-forward (FF) configuration is used to bypass the Q controller in case there is a loss of communication. Further study found that the FF control mode was still engaged when communication was re-established, which ultimately resulted in the oscillation event. However, there was no detailed explanation of why the FF control mode can cause instability in the hybrid farm. Also, there was no duplication of the event in the simulation to analyze the root cause of the oscillation. Therefore, this research aims to model and replicate the oscillation event in a simulation environment and investigate the underlying behavior of the HPPC and the consequent oscillation mechanism during the incident. The outcome of this research will provide significant benefits to the safe operation of large-scale renewable energy generators and power networks.

Keywords: PV, oscillation, modelling, wind

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