Author Topic: Design of Boost Circuit for Wind Generator  (Read 2210 times)

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Design of Boost Circuit for Wind Generator
« on: April 23, 2011, 02:15:02 pm »
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Author : N.Prasanna Raj, M.Mohanraj, Rani Thottungal
International Journal of Scientific & Engineering Research, IJSER - Volume 2, Issue 4, April-2011
ISSN 2229-5518
Download Full Paper - http://www.ijser.org/onlineResearchPaperViewer.aspx?Design_of_Boost_Circuit_for_Wind_Generator.pdf

Abstract This paper presents the design and implementation of a power converter for an autonomous wind induction generator (IG) feeding an isolated load through the PWM-based novel soft-switching interleaved boost converter. The output voltage and frequency of the wind IG is inherently variable due to random fluctuation of wind-speed variation. The interleaved boost converter composed of two shunted elementary boost conversion units and an auxiliary inductor. This converter is able to turn on both the active power switches at zero voltage to reduce their switching losses and evidently raise the conversion efficiency. Since the two parallel-operated elementary boost units are identical, operation analysis and design for the converter module becomes quite simple. A three-phase induction machine model and a three-phase rectifier-inverter model based on a-b-c reference frame are used to simulate the performance of the generation system. It can be concluded from the simulated results that the designed power converters with adequate control scheme can effectively improve the performance of output voltage and frequency of the IG feeding an isolated load.

Index Terms wind power generator, rectifier-inverter circuit, pulse width modulation (PWM), interleaved boost converter, soft switching.

Introduction
THE characteristics of induction generator (IG) with an externally connected capacitor bank have been extensively explored for over 60 years since 1935 [1]. Due to the fast development of environmental protection concepts, the regenerative or renewable energy sources have been significantly and widely studied and evaluated in the whole world. The primary merits of IG over a conventional synchronous generator are brushless construction with squirrel-cage rotor, small size, without DC supply for excitation, less maintenance cost, and better transient performance. The IGs have been extensively utilized as suitable isolated power sources in small hydroelectric, tidal, and wind energy applications at the remote sites, rural areas, or developing countries [2 4]. The performance of IG supplying various static loads using different control schemes are studied and analysed in various papers. The control schemes proposed so far divides into three categories. The most economic method is by means of switching series and/or parallel capacitors connected to the IG stator winding or load side for voltage regulation. The primary disadvantage of this scheme is that the equivalent capacitance is changed in discrete form and the voltage cannot be effectively and linearly regulated. Though the voltage magnitude is controlled to a certain constant level, the output frequency of the controlled IG is significantly varied with the rotor speed. The second method is to modulate the absorbed reactive power of the IG whose stator windings is directly connected to the load and the reactive power compensator. Although the terminal voltage of the stator winding can be effectively controlled, the frequency variation problem due to random
fluctuation of rotor speed is similar to the one of the first method. The third method is the most effective control scheme, which can control both voltage and frequency of the IG within a specified level by using power electronic converters such as a rectifier-inverter module (AC-to-DC and DC-to-AC converters).
Boost converters are usually applied as preregulators or even integrated with the latter-stage circuits or rectifiers into single-stage circuits [5 9]. Most renewable power sources, such as photovoltaic power systems and fuel cells, have quite low-voltage output and require series connection or a voltage booster to provide enough voltage output. Several soft-switching techniques for dc/dc converters have been proposed. The main problem with these kinds of converters is that the voltage stresses on the power switches are too high in the resonant converters, especially for the high-input dc-voltage applications. Interleaved boost converters are applied as power-factor-correction front ends. An interleaved converter with a coupled winding is proposed to provide a lossless clamp. Additional active switches are also appended to provide soft-switching characteristics [10 13]. These converters are able to provide higher output power and lower output ripple. This paper proposes a soft-switching interleaved boost converter composed of two shunted elementary boost conversion units and an auxiliary inductor. This converter is able to turn on both the active power switches at zero voltage to reduce their switching losses and evidently raise the conversion efficiency [14], [15]. Since the two parallel-operated boost units are identical, operation analysis and design for the converter module becomes quite simple.
IG fed to an isolated load through the employment of a


Fig. Wind Turbine  (Download Full Paper To View )

PWM based closed loop boost converter with controlled inverter is presented. The simulated performance of the proposed control scheme is employed to design a PWM controller for the boost converter and inverter. The implementation and design of a power converter for an autonomous wind induction generator (IG) feeding an isolated load through the PWM-based boost-inverter circuit is simulated here.

2   METHODOLOGY
The generation system is designed with IG. The stator winding terminals of the IG are connected to the load through the rectifier, DC link, Boost circuit and inverter. The closed loop PWM signal generates proper PWM signals to switch the 2 power electronics devices of the Interleaved Boost Converter (IBC). The wind turbine rotates the IG. The IG generates power when the speed of the turbine is above the rated speed. The power generated from the IG is converted to DC with a diode bridge rectifier. The obtained DC voltage will not be in a pure DC signal. A filter circuit is used to filter out the ripple current and a pure DC voltage is obtained. This DC voltage is then boosted to the required DC level and then converted to three phase AC signal with IGBT which is driven by PWM signal. To regulate the AC output voltage the IBC is controlled by close loop PWM signals. A load is connected at the output of the inverter. The voltage-current equations of the studied IG in matrix form are listed as below.

Read More: http://www.ijser.org/onlineResearchPaperViewer.aspx?Design_of_Boost_Circuit_for_Wind_Generator.pdf