Modelling of wind energy converters for slow and fast transients

To improve the accuracy of wind generator grid impact studies, it is needed to develop faster and sophisticated models using various simulation tools. The simulations are usually carried out independently for fast and slow transients. Traditional slow transient analysis methods are based on simplified solution methods with various approximations. These methods fall into the category of electromechanical transients. More sophisticated models are based on the detailed simulation of all wind generator components. Such models fall into the category of electromagnetic transients (EMT). It is, however, complicated to run detailed simulations for long simulation periods due to computer time restrictions. This is especially true in large grid integration simulations. The objective and innovation of this thesis is the simulation of wind generators in EMTP-type (Electromagnetic Transients Program) programs using faster modeling techniques with small integration time-steps and the capability to combine with detailed models. This way fast and slow transients are solved in the same environment and with acceptable computational speed. Another objective of this thesis is the contribution of wind generator models for wind farm integration studies.;This thesis presents the integration of three types of models, two mean value type models and one detailed EMTP-type (Electromagnetic Transients Program type), in the same EMTP-RV (software of EMTP-type) environment and with the same numerical methods. The mean value type models are distinguished by their precision levels. At the first level the model is demonstrated to contribute to significant reduction of computing time while limiting the loss of accuracy. At the second level the model provides precision improvement over the first level while still limiting computational efforts.;The presented modeling techniques are validated using comparative simulation techniques based on EMTP-RV and PSS/E. PSS/E is only used for the simulation of electromechanical transients.;Since the development of wind generator models is a complex task on its own, this thesis also contributes by developing various comprehensive models with appropriate improvements in several aspects, such as initialization techniques, aggregation, controls, model components and the complicated establishment of validation and comparison of models in two different environments, namely PSS/E and EMTP-RV. The contributed models will be also used in future research works related to wind generation integration into power systems and related controls.;The contributed models are of wideband type and are used for studying power system integration problems, such as overvoltages, undervoltages, frequency deviation, power quality and islanding.