Analysis of Transients in Wind Parks - System Modeling and Experimental Verification

Abstract: This thesis deals with analysis of transients and experimental verifications in wind parks. The focus is on accurate modeling of system components such as cables, vacuum circuit breaker and transformer which make any branch in a wind park. Models are also validated where possible. Although a lot has been done and fairly good models of cables and VCB have been developed, it seems that a unified wide band model of transformers which works well for broad range of frequencies has been the most difficult to develop. Critical as it is in transient studies, modeling of such a transformer has been extensively treated in this thesis. In the first part of the thesis, a frequency dependent model which represents high frequency effects like wave propagation, damping and reflection is used to model the cables using PSCAD/EMTDC. The model is also validated experimentally. Secondly, a statistical model which emulates the occurrence of re-ignitions, pre-strikes and current chopping behaviours of the VCB during opening or closing operations is dealt with. Finally, a terminal model of a transformer which represents its wide frequency response is developed based on experimental measurement of admittance matrix over a wide range of frequencies. The curve fitting algorithm is used to approximate the admittance matrix. An RLC equivalent network is realized and implemented in the time simulation software PSCAD/EMTDC.