Modeling, estimation, and self-tuning control of AC/DC systems

Currently, most of the design and planning studies of HVDC systems are performed on analog and scaled-down simulators in industrial laboratories. In this research, we developed a modular digital simulation of the DC terminal and interfaced it with the efficient Bergeron's technique for network simulation. This combination is much easier to setup than the TACS in the Electromagnetic Transient Program, and has the same capability to represent, in detail, a large piece of the AC network. Other additions to the program include the representation of static var compensator, nonlinear transformers and zinc oxide arresters.;Another aspect of simulation dealt with in this research is the establishment of a linear model for determining suitable parameters and for stability studies. A key component in such modeling is the discrete nature of the converter. Based on the model proposed by Sucena Paiva, a discrete linear model of a complete AC/DC link was developed. This model was then tested and the test results, verified by detailed simulation, confirmed the suitability of such a model for stability and controller optimization studies.;The last phase of this research is on the application of self-tuning technique to the current controller of a DC converter. A combination of Singular Value Decomposition and Recursive Least Square techniques was used to determine a model of the AC/DC system as viewed by the current controller of the terminal. The estimation technique uses only the natural perturbations inherent in converter operation. The usefulness of such an estimated model of the AC/DC system was demonstrated by using it to tune the gain of the current controller. Results obtained from detailed simulation indicates improvement in dynamic performance with self-tuning.