Avaliação do impacto da intermitência da geração eólica na estabilidade de tensão de sistemas elétricos de potência utilizando um método de análise de sensibilidade

Abstract

This work addresses, in a first step, the voltage and frequency control in electrical networks containing wind generation. To this end, four distinct types of wind generators are mathematically modeled and then included in a power flow formulation capable of representing the primary frequency regulation of the grid. In addition, a Coordinated Voltage Control strategy for wind farms composed of Permanent Magnet Synchronous Generators is presented. This strategy allows controlling the magnitude of the terminal voltage of these wind farms and adjusting the reactive power generations of these wind generators. For this purpose, participation factors are used in this control strategy. They are calculated based on the maximum limits of reactive power generation of the machines that participate in the voltage control. Case studies show that wind generators can assist in the primary frequency regulation of the systems and that the proposed voltage control strategy can avoid the premature violation of the reactive power generation limits of the Permanent Magnet Synchronous Generators. This work evaluates, in a second stage, the impact of the intermittent characteristic of the wind generation on the voltage stability of the Electric Power Systems. For this purpose, linear and quadratic sensitivities of the Loading Margin with respect to the wind speed are calculated. These sensitivities are based on the equations inserted into a power flow formulation capable of representing the secondary frequency regulation. With these sensitivities, changes in the Loading Margin due to wind speed perturbations in the wind farms can be estimated. In addition, a sensitivity of the state variables at the system Maximum Loading Point with respect to the wind speed is also obtained during the calculation of the quadratic sensitivity. Based on this sensitivity, the active power generation of the synchronous generators after wind speed perturbations in the wind farms can be estimated. In the analyses performed in this second part of the work two types of wind generators are considered, the Doubly Fed Induction Generators and the Stall Regulated Fixed Speed Wind Generators. Precise estimates of the Loading Margin are obtained in the case studies in networks containing these types of wind generators, demonstrating the effectiveness of the proposed methodology.