Thursday, April 18, 2013

Real-Time Implementation of DSP based Stand-Alone DOIG (Double Output Induction Generator) for VSCF generation

It is also named as Double Fed Induction Generator (DFIG)
In the past few decades wind power has become one of the most attractive solutions for clean and renewable energy. Recent years have seen a huge application and improvement of wind energy systems particularly with the improvement in power semiconductor technology, high speed DSP controllers and software tools which facilitate rapid implementation of digital control algorithms and real-time control. Now-a-days most of the renewable energy generation is done through variable speed induction generators. Squirrel cage and Wound rotor induction machines as well as synchronous machines have found increasing application in the wind energy. Though the requirements of utility (grid/load) are not fulfilled directly just by the machine, the control strategy is used in both the stator as well as rotor side along with power electronic converters to fulfil the requirements of utility.



The statistical data conveys that Double Output Induction Generator (DOIG) based wind turbine with variable speed and variable pitch control is the most common wind turbine in the growing wind market. The basic control of the total system (DOIG with Two back-to-back connected PWM voltage-fed converters) is that the machine-side converter controls the active and reactive power by controlling the dq components of rotor current (i.e.,  and ), while the grid-side converter controls the dc-link voltage.
The double output induction generator (DOIG) can supply power at constant voltage and constant frequency while the rotor speed varies and so supplying grid connected or isolated load. This makes it suitable for variable speed wind energy applications. The load voltage is maintained at constant frequency and its magnitude is regulated through control of the stator flux of the generator. By means of a bidirectional converter the speed range can be extended above and below synchronous speed and power can be generated both from the stator and the rotor. The main advantage of this type of DOIG drive is that the rotor converter need only be rated for a fraction of the total output power, the fraction depending on the allowable sub- and super-synchronous speed range.

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