The Effect of Load Shedding on Improving the Power System Voltage Instability with VSC-HVDC Connection of Offshore Wind Farm

Mehdizadeh, Masoud and Seyed Shenava, Seyed Jalal and Shayeghi, Hosein (2016) The Effect of Load Shedding on Improving the Power System Voltage Instability with VSC-HVDC Connection of Offshore Wind Farm. Masters thesis, University of Mohaghegh Ardabili.

Text (بررسی تأثیر بارزدايي در بهبود ناپایداری ولتاژ سیستم قدرت با اتصالVSC-HVDC مربوط به مزرعهی بادی دور از ساحل) Masoud Mehdizadeh.pdf Download (1MB)

Abstract

In recent years, different events have led to voltage collapse in power systems, including short circuit in transmission lines, consequently transmission lines outage, system islanding, or the sudden generator's switch-off in the circuit. Growing the usage of offshore wind farms, it seems necessary to study the voltage collapse phenomenon in power systems with the presence of such farms. The main purpose of this thesis is to study the effect of load shedding in preventing voltage collapse in a power system, in the presence of an offshore wind farm connected to the main network. To achieve this goal, first the voltage collapse phenomenon and its reasons, are studied. Then, different kinds of methods for discovering the online voltage instability are studied to determine the proper time and place for load shedding and two of these methods are chosen as the most modern and practical ways. In the next part of the thesis, these two methods have been studied with the dynamic and Quasi-steady state studies in terms of errors and island power system. Software used in this study is DigSILENT. Accordingly, the first thing to check is the dynamic modeling of the wind farm, VSC-HVDC lines and controllers in DigSILENT. In the simulation stage, first the three introduced indices: Lmn, VCPI and NLSI are used to determine the time of instability and the bus rankings of the power system. Then the method of matching the Thevenin impedance is used with the help of the equivalent circuit of the VSC-HDVC line, to determine the time of instability, the proper bus for load shedding and the amount of the load shedding. Finally, these methods are compared, their pros and cons are discussed and a new method for the load shedding is proposed. The simulation results in DigSILENT, represents the success of the proposed method to predict the right time load shedding, load shedding convenient location, the least amount of load shedding and maintain voltage stability after the load has been removed. Keywords: Load shedding, Offshore wind farms, Voltage collapse, Voltage stability indexes

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