Author: Yuan, Wei
Title: Frequency and oscillation stability analysis of virtual synchronous generator-integrated power grid
Advisors: Bu, S. Q. (EE)
Degree: M.Sc.
Year: 2019
Subject: Electric generators -- Alternating current
Electric power systems -- Control
Hong Kong Polytechnic University -- Dissertations
Department: Department of Electrical Engineering
Pages: viii, 70 pages : color illustrations
Language: English
Abstract: With large demand in sustainable energy, renewable energy sources (RESs) connected with power system are growing fast. To achieve better controllability, RESs are usually connected to power system through inverters. Unlike traditional synchronous generators (SGs), the RESs including the inverters do not provide inertia for the external power system due to the different physical structure. This leads to the decrease in the effective inertia and deterioration in the frequency dynamics and damping characteristics of the power system. Therefore, the frequency stability and oscillation stability of power system are threatened and need to be properly enhanced.
To solve the problem, a virtual synchronous generator (VSG) control method is proposed to provide virtual inertia. VSG control can emulate the rotor inertia of traditional SG by adding an energy storage unit with the appropriate control algorithms. With VSG control algorithms integrated, the inverters can achieve similar frequency and voltage control characteristics and act as the role of traditional SG, from the view of the external power system. Hence, the virtual inertia provided by VSG helps improve the frequency stability.
In this thesis, a VSG control model to assess the frequency and damping interaction between RESs and the external power system will be introduced. Firstly, the virtual inertial model of the VSG can be derived by establishing the mathematical model of the energy storage unit and the inverter. In addition, variation of frequency is used as the feedback input for VSG control algorithms, with proper tuning of the control parameters of VSG, variable virtual inertia can be performed under different operation conditions. Thus, the influence of the VSG control method on the frequency and damping characteristics of the power system can be analyzed. The effectiveness of the VSG control method will be validated in a sample power system.
Rights: All rights reserved
Access: restricted access

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