Analytical Methods of Voltage Support Strength in Dual-infeed Hybrid HVDC System

Author(s):  
Zhou Lan ◽  
MingJiu Pan ◽  
Junxian Jiang ◽  
Ke Sun ◽  
Kai Yang
Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3222
Author(s):  
Duc Nguyen Huu

Increasing offshore wind farms are rapidly installed and planned. However, this will pose a bottle neck challenge for long-distance transmission as well as inherent variation of their generating power outputs to the existing AC grid. VSC-HVDC links could be an effective and flexible method for this issue. With the growing use of voltage source converter high-voltage direct current (VSC-HVDC) technology, the hybrid VSC-HVDC and AC system will be a next-generation transmission network. This paper analyzes the contribution of the multi VSC-HVDC system on the AC voltage stability of the hybrid system. A key contribution of this research is proposing a novel adaptive control approach of the VSC-HVDC as a so-called dynamic reactive power booster to enhance the voltage stability of the AC system. The core idea is that the novel control system is automatically providing a reactive current based on dynamic frequency of the AC system to maximal AC voltage support. Based on the analysis, an adaptive control method applied to the multi VSC-HVDC system is proposed to realize maximum capacity of VSC for reactive power according to the change of the system frequency during severe faults of the AC grid. A representative hybrid AC-DC network based on Germany is developed. Detailed modeling of the hybrid AC-DC network and its proposed control is derived in PSCAD software. PSCAD simulation results and analysis verify the effective performance of this novel adaptive control of VSC-HVDC for voltage support. Thanks to this control scheme, the hybrid AC-DC network can avoid circumstances that lead to voltage instability.


Author(s):  
J.R. McIntosh ◽  
D.L. Stemple ◽  
William Bishop ◽  
G.W. Hannaway

EM specimens often contain 3-dimensional information that is lost during micrography on a single photographic film. Two images of one specimen at appropriate orientations give a stereo view, but complex structures composed of multiple objects of graded density that superimpose in each projection are often difficult to decipher in stereo. Several analytical methods for 3-D reconstruction from multiple images of a serially tilted specimen are available, but they are all time-consuming and computationally intense.


2015 ◽  
Vol 48 (06) ◽  
Author(s):  
H Esselmann ◽  
C Hafermann ◽  
O Jahn ◽  
I Kraus ◽  
J Vogelgsang ◽  
...  

2018 ◽  
Vol 6 (3) ◽  
Author(s):  
Alawiye Abdulmumin Abdurrazzaq ◽  
Ahmad Wifaq Mokhtar ◽  
Abdul Manan Ismail

This article is aimed to examine the extent of the application of Islamic legal objectives by Sheikh Abdullah bn Fudi in his rejoinder against one of their contemporary scholars who accused them of being over-liberal about the religion. He claimed that there has been a careless intermingling of men and women in the preaching and counselling gathering they used to hold, under the leadership of Sheikh Uthman bn Fudi (the Islamic reformer of the nineteenth century in Nigeria and West Africa). Thus, in this study, the researchers seek to answer the following interrogations: who was Abdullah bn Fudi? who was their critic? what was the subject matter of the criticism? How did the rebutter get equipped with some guidelines of higher objectives of Sharĩʻah in his rejoinder to the critic? To this end, this study had tackled the questions afore-stated by using inductive, descriptive and analytical methods to identify the personalities involved, define and analyze some concepts and matters considered as the hub of the study.


2019 ◽  
Vol 7 (2) ◽  
Author(s):  
fithriah wardi

Both fuqaha (Moslem jurists) of the Sunni and the Shi’ah are in agreement that Mut’ah marriage was permitted at the beginning of Islam, based on Al-quran verses and Rasulullah (pbuh) hadiths. However, they disagree as to the annulment and permissibility. The Shi’as considered Mut’ah marriage as permitted until the Day of Resurrection, meanwhile the Sunni viewed it as forbidden. The execution of Mut’ah marriage has always been singled out as one of the specific features of the Shi’ite doctrine in which denying it means denial of the religion. They also believe that woman who practised Mut’ah marriage will result in her sins being forgiven. According to the Shi’ites, Mut’ah marriage is one of the biggest reasons for someone to be granted heaven, and his status be elevated to the rank of the Holy Prophet PBUH. Hence, it can be said that practicing Mut’ah marriage is one of the most crucial issues among the Shi’ite community which is totally contradicted to the Sunni doctrine which believed it is unlawful marriage and equalized to Zina (adultery). There is no doubt that this is one of the most important topics that lead to the dispute between the two schools of thought. Using the descriptive and analytical methods, this study aims to elaborate the views on the issue from Shi’ite and Sunni points of view based on various proofs (adillah) and their argumentations in supporting the views.


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