Calculation of parameter ranges for robust gain tuning of power system controllers

This work proposes a computational tool to assist power system engineers in the field tuning of power system stabilizers (PSSs) and Automatic Voltage Regulators (AVRs). The outcome of this tool is a range of gain values for theses controllers within which there is a theoretical guarantee of stability for the closed-loop system. This range is given as a set of limit values for the static gains of the controllers of interest, in such a way that the engineer responsible for the field tuning of PSSs and/or AVRs can be confident with respect to system stability when adjusting the corresponding static gains within this range. This feature of the proposed tool is highly desirable from a practical viewpoint, since the PSS and AVR commissioning stage always involve some readjustment of the controller gains to account for the differences between the nominal model and the actual behavior of the system. By capturing these differences as uncertainties in the model, this computational tool is able to guarantee stability for the whole uncertain model using an approach based on linear matrix inequalities. It is also important to remark that the tool proposed in this paper can also be applied to other types of parameters of either PSSs or Power Oscillation Dampers, as well as other types of controllers (such as speed governors, for example). To show its effectiveness, applications of the proposed tool to two benchmarks for small signal stability studies are presented at the end of this paper. O presente trabalho propõe uma ferramenta computacional para auxiliar engenheiros de sistemas de potência no ajuste em campo de controladores de amortecimento e reguladores automáticos de tensão. A abordagem proposta gera faixas de valores de parâmetros para o ajuste em campo dos controladores do sistema. As faixas de valores geradas teoricamente garantem a estabilidade para o sistema em malha fechada. Estas faixas de valores são dadas na forma de valores limites para os ganhos estáticos dos controladores de interesse, de maneira que o engenheiro responsável pelo ajuste em campo dos controladores tenha garantia da estabilidade do sistema durante o ajuste do ganho do controlador. Esta característica da abordagem proposta é altamente desejavel do ponto de vista prático, pois a etapa de comissionamento de controladores de amortecimento e reguladores automáticos de tensão sempre envolve algum reajuste dos ganhos dos controlares, devido às diferenças entre o modelo nominal e o comportament