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This paper presents new methodologies for modeling static VAr compensators (SVCs) in the power flow problem. The proposed formulations utilize sigmoid functions to model the control equations that describe the steady-state behavior of SVCs. The first methodology introduces reactive power injection as a new state variable, while the second methodology utilizes the thyristor firing angle. These steady-state SVC methodologies were applied to the power flow problem using the full Newton formulation, which incorporates the control equations into the system of nonlinear equations. One of the main contributions of these proposed methodologies is that they eliminate the need for alternating adjustments concerning the operational limits of the SVC during the iterative power flow process. The implementation of a power flow program was tested on both small-scale tutorial systems and the medium-scale IEEE Nordic system. The presented results validate and demonstrate the effectiveness of the proposed methodology. [ABSTRACT FROM AUTHOR]

The optimal wind power generation connection in power systems is a growing field of study recently. Accordingly to the literature, the Optimal Transmission Switching technique and the Power Transfer Distribution Factors have been applied to the optimization problem of the capacity of wind power connection. This paper proposes a new methodology for maximization of wind power connection that integrates these two methods mentioned. The optimization process is based on the linearized power flow and chooses the best line for a firm wind farm connection from a list of possible candidates. The proposed algorithm is evaluated considering the 11-Bus tutorial system, the IEEE New England and IEEE-118 systems. • New methodology for determining optimal connection of wind farms to power systems. • Link Optimal Transmission Switching and Power Transfer Distribution Factor methods. • Transmission Switching applied only to connection lines reduces computational effort. • New Power Transfer Distribution Factor provides real power unbalancing distribution. [ABSTRACT FROM AUTHOR]

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]

• A new methodology for the Steady-state security region for the security assessment of distribution systems with the presence of DER. • Consideration of the intermittent characteristic of the DER generations. • The proposed methodology can be used in online or offline environments. • The proposed tool can be used in planning studies of distribution systems. • The proposed methodology can also be used for DER Regulation and Allocation in Distribution Networks: Volt/Var optimization and Congestion Relief. Modern Electric Power Systems are evolving from a centralized generation model toward a complex infrastructure with the presence of Distributed Energy Resources (DER). The transformative changes are especially pronounced at the level of the distribution system. The emergence of new generation technologies as solar, for example, affects the customer profile, expansion planning, and operation procedures of distribution utilities. Therefore, this paper describes a new methodology based on steady-state security regions concept for the security assessment of distribution systems with the presence of DER. The main objective of the proposed methodology is to allow an effective evaluation of the operating conditions of distribution systems with high penetration of DER, focusing on the intermittence of the new generation resources. The proposed methodology has been tested using two distribution systems. The first one is a tutorial 13-bus system, which is a small tutorial feeder, and the second one is a real large-scale model of a distribution network. The results presented indicate the effectiveness of the proposed technique in the distribution system security analysis. The proposed methodology is implemented using the Python language and uses the OpenDSS software as a power flow solver. [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]

Power System Stabilizers are controllers installed on synchronous generators to damp power system oscillations through the excitation control. These controllers can have either a conventional fixed structure composed by stages of gain and phase compensation or a flexible modern structure composed by three bands that correspond to a specific frequency range (low, intermediate and high frequency) in which each band is composed by two branches that are based on differential filters (with a gain, lead-lag blocks and a hybrid block). Power system stabilizers design is a hard and time consuming task and an alternative for tuning controllers is by using optimization methods. This paper presents three hybrid metaheuristics for the robust and coordinated design of power system stabilizers. The tuning procedure is modeled as an optimization problem which aims at maximizing the damping ratio coefficients in closed-loop operation. Robustness requirement is met by using multiple operating scenarios in the design stage. For solving the optimization problem, three metaheuristics (Gravitational Search Algorithm, Bat Algorithm and Particle Swarm Optimization) are combined with the Steepest Descent Method for local search capability enhancement. The proposed hybrid algorithms are applied to benchmark systems for validation. [ABSTRACT FROM AUTHOR]

This paper presents a comparison study among three bio-inspired optimization algorithms applied to solve the power system stabilizers tuning problem: Ant Colony Optimization, Bat Algorithm and Genetic Algorithm. The tuning procedure is formulated as an optimization problem which aims at minimizing the system damping taking into account a set of pre-specified operating scenarios. The proposed methodologies are applied to stabilizers tuning of the well-known New England test system. [ABSTRACT FROM AUTHOR]

• A new unbalanced three-phase governor power flow formulation. • Both synchronous generators and droop-based distributed generators modeling. • Allows the evaluation of the system frequency due to active power unbalance. • The losses are distributed among the generating units in a more realistic way. • From this formulation any bus of the system can be the system reference bus. This paper presents a new unbalanced three-phase governor power flow formulation using the three-phase current injection equations (TCIM) expressed as a function of voltages expressed in rectangular coordinates. The proposed technique considers the representation of the primary frequency regulation for synchronous generators, as well as, voltage and frequency regulation in a droop-based control for distributed generation units (DGs). The static response of the generation governor, droop control equations and an equation to define the network reference angle for a given value are incorporated into the modeling. As the system is unbalanced, an internal additional bus, having balanced voltages, was created for each synchronous generator. As a consequence, two additional equations were included to keep internal voltages balanced. The inclusion of new equations results in an augmented formulation which is then linearized and solved using the Newton–Raphson method, in which the original structure of the Jacobian matrix from the current injections method is preserved. The proposed formulation allows the distribution of the active losses among the generating units as well as the determination of the frequency deviation due to variations, either in the total amount of generation or in the total system load. Any bus (load or generation bus) of the system can be chosen as the system reference bus. The results obtained using the unbalanced three-phase 6-bus test system were validated using the well known RTDS (real time digital simulator). The 25-bus islanded test system was also used in the simulations with the inclusion of synchronous generation (SG) units to demonstrate the effectiveness of the proposed methodology. [ABSTRACT FROM AUTHOR]