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The main objective of this paper is to review and compare two methodologies to solve the power flow problem considering active power generation droop control. The first methodology is based on a DC power flow model, and the second one is based on a conventional full Newton power flow formulation. The study of two test systems is used to validate the proposed analysis; the first one is the 11-bus system with two distinct areas, and the second one is the 39-bus New England power system. The results presented validate and indicate the effectiveness of the DC power flow approach in order to estimate the steady-state system frequency deviations. [ABSTRACT FROM AUTHOR]

The use of Direct Current (DC) transmission links in power systems is increasing continuously. Thus, it is important to develop new techniques to model the inclusion of these devices in network analysis, in order to allow studies of the operation and expansion planning of large-scale electric power systems. In this context, the main objective of this paper is to present a new methodology for a simultaneous AC-DC power flow for a multi-terminal High Voltage Direct Current (HVDC) system with a generic representation of the DC network. The proposed methodology is based on a full Newton formulation for solving the AC-DC power flow problem. Equations representing the converters and steady-state control strategies are included in a power flow problem formulation, resulting in an expanded Jacobian matrix of the Newton method. Some results are presented based on HVDC test systems to confirm the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

• The wind speed can significantly impact the loading margin of the power systems. • Precise estimates of the loading margin are obtained for wind speed perturbations. • The quadratic estimate is generally more accurate than the linear estimate. • The synchronous generators dispatch is accurately estimated after wind speed changes. • Estimation errors tend to grow with greater perturbations, but are still acceptable. The main objective of this paper is to evaluate the impacts in electrical networks, particularly on the voltage stability margins, due to the presence of Wind Generation (WG) and its intermittent characteristic. For this purpose, linear and quadratic sensitivities of the Loading Margin (LM) with relation to the wind speed are calculated, and then utilized to estimate possible alterations in the LM due to perturbations in the wind speed of the wind farms. To include the variable wind speed in the sensitivity analysis of the LM two types of wind generators are mathematically modeled and then incorporated into the power flow formulation. Lastly, three case studies are performed, where accurate estimates of the LM are obtained for wind speed perturbations in the wind farms, demonstrating the effectiveness of the proposed methodology and its potential to assist in the real-time operation and the operation planning of power systems with WG. [ABSTRACT FROM AUTHOR]