Application of a Dynamic Voltage Restorer to Regulate the Terminal Voltage of a Grid-tied Squirrel-cage Induction Generator
Date Issued
2012
Date
2012
Author(s)
Chang, Chia-Ming
Abstract
As the issue of energy crisis and climate change receives increasing attention, intensive efforts have been devoted to the research of renewable energy. Wind power generation is a popular research subject because of the advantages such as low cost, zero pollution, and inexhaustible supply of wind energy. Among the types of wind generator sets, squirrel-cage induction generators have been widely used due to its low cost, simple structure, and easy control strategy.
However, the reactive power of squirrel-cage induction generators cannot be controlled due to the lack of rotor excitation. Besides, the power generated by squirrel -cage induction generators is highly dependent on the generator terminal voltage. Therefore, when the power system is subjected to load changes or faults, the terminal voltage of squirrel-cage generators will drop, leading to the stall of generators. Moreover, the ever-changing wind speed results in fluctuating generator terminal voltage and the resultant unpredictable real power output.
In this thesis, a dynamic voltage restorer (DVR) based on the fuzzy logic controller is designed to regulate the terminal voltage of a grid-tied squirrel -cage induction generator. From experimental results, it is verified that the proposed DVR can effectively regulate the generator terminal voltage when load or wind speed changes. Two compensating methods, in-phase voltage compensation and purely reactive power compensation, are realized in this thesis. The experimental results indicate that, tocompensate for the same voltage drop, the injected voltage by DVR is smaller if in-phase voltage compensation method is employed, which reducing the installed capacity of DVR.
Subjects
wind power generation
induction generator
dynamic voltage restorer
fuzzy logic controller
in-phase voltage compensation
Type
thesis
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