Modelling and verification of doubly fed induction generator (DFIG) using real time digital simulator (RTDS)
Examensarbete för masterexamen
This master thesis deals with Doubly Fed Induction Generator (DFIG) controller in RSCAD model. The controller in RSCAD is built and designed according to the available PSCAD model and differences between two models are highlighted. Also an investigation is made to increase power in RSCAD by using a scaling transformer; finally scaled models in both models are verified against each other. The work starts with a brief introduction of different wind turbine generators and their specifications, and describing the theory of variable wind turbines and their advantages over the fixed wind turbines. In this project doubly fed Induction generator (DFIG) wind turbines are considered and studied, DFIG and different parts of its controller are discussed, and required equations for DFIG are derived. Real Time Digital Simulator (RTDS) hardware and RSCAD software, which are used as the simulator tools at this project are introduced for readers and then a sample DFIG is modeled in RSCAD. For verification purposes in first part of the project a 5 MW DFIG model with complete controllers and scaling transformer in PSCAD are used, by sending scaling level to 40 in PSCAD the model will represent 200 MW. The base model in RSCAD is a single 200 MW DFIG; both models in PSCAD and RSCAD are connected to an infinite 154 kV network with known R, L and C values. Different fault cases are applied to both models to compare behavior of models during transients and also in normal operation. System studies show that current RSCAD model behavior is completely different from the PSCAD model. The controllers in both models in RSCAD and PSCAD, with all possible reasons for having different results were investigated and it was tried to make the RSCAD model similar to the PSCAD model as much as it was possible. The second task of this work is about adding scaling feature to the model in RSCAD, as in most cases 800 MW wind farm or even higher power ratings should be implemented in RSCAD for a typical wind farm project. As the base model in PSCAD is 5 MW to model an 800 MW DFIG in PSCAD scaling factor of 160 should be used, and for RSCAD model scaling should be 4 as the RSCAD base model is 200 MW. It was shown that the scaled model in RSCAD would be unstable after scaling, and the second task at this project was to study the scaling system concept in both RSCAD and PSCAD, and find any possible differences between the two models.
Elkraftteknik , Electric power engineering