Edmarcio Antonio Belati

Primal-Dual Logarithmic Barrier and Augmented Lagrangian Function to the Loss Minimization in Power Systems

This article presents a new approach to minimize the losses in electrical power systems. This approach considers the application of the primal-dual logarithmic barrier method to voltage magnitude and tap-changing transformer variables, and the other inequality constraints are treated by augmented Lagrangian method. The Lagrangian function aggregates all the constraints. The first-order necessary conditions are reached by Newtons method, and by updating the dual variables and penalty factors. Test results are presented to show the good performance of this approach.

A new solution to the optimal power flow problem

A new approach to solving the optimal power flow problem is described, making use of some findings especially in the area of primal-dual methods for complex programming. In this approach, equality constraints are handled by Newtons method inequality constraints for voltage and transformer taps by the logarithmic barrier method and the other inequality constraints by the augmented Lagrangian method. Numerical test results are presented, showing the effective performance of this algorithm.

A new approach type-Newton for optimal reactive dispatch problem

This paper presents a new approach that improves the performance of the Newtons method for optimal reactive dispatch problem. In this approach the inequality constraints are divided into two groups: constraints treated by penalty function, which are added to the objective function through penalty factors, and constraints treated by barrier function that are grouped with the set of active constraints (power flow equations). The first order necessary conditions for optimality are reached by Newtons method, and by updating the penalty and barrier terms. The factorization is carried out on elements instead of structures in blocks. The main advantage is not to identify the biding constraints set. The effectiveness of the proposed approach has been examined by solving the 53-bus and 118-bus systems.

Linearized AC Load Flow Applied to Analysis in Electric Power Systems

This paper presents a method for load flow calculation to electrical power systems called Linearized AC Load Flow (LACLF). The method is developed based on the linearization of the full set of equations of AC Load Flow (ACLF) . Unlike ACLF algorithm, this method does not require an iterative process, which results in a fast and robust method. The LACLF considers all ACLF couplings, i.e., the coupling of active power with the magnitude of voltage as well as the coupling between reactive power and voltage angle, different from the traditional DC load flow method (DCLF).The proposed method is applied to the distribution 34-bus, 70-bus and 126-bus systems and transmission 14-bus, 30-bus and 118-bus systems. The solutions of the LACLF were compared with the ACLF and DCLF. The results of the tests demonstrate the effectiveness of the method.

Evaluating Harmonic Voltage in Electric Distribution Systems due to Six-Pulse Static Power Converter

The circulation of harmonic currents in power systems, caused by particular nonlinear loads, leads to harmonic voltages which depend on the circuit and on the load it drives. Harmonic currents in the system also contribute with a portion of the system technical losses and produce a series of undesirable effects. This paper presents an alternative approach based on an efficient harmonic load flow algorithm in order to evaluate harmonic voltages along distribution systems due to nonlinear loads, more specifically a six-pulse static power converter. The proposed methodology uses frequency-domain formulations which allow dealing directly with voltage and current phasors. Tests were carried out on 04 and 34 bus distribution systems in order to evaluate the proposed technique performance.

Influence of the Operational Constraint in the Active Transmission Losses Allocation Via Lagrange Multipliers

This paper presents an approach for the active transmission losses allocation between the agents of the system. The approach uses the primal and dual variable information of the Optimal Power Flow in the losses allocation strategy. The allocation coefficients are determined via Lagrange multipliers. The paper emphasizes the necessity to consider the operational constraints and parameters of the systems in the problem solution. An example, for a 3-bus system is presented in details, as well as a comparative test with the main allocation methods. Case studies on the IEEE 14-bus systems are carried out to verify the influence of the constraints and parameters of the system in the losses allocation.

Optimal Allocation of Capacitor Banks using Genetic Algorithm and Sensitivity Analysis

This paper presents a methodology for allocation of Bank of Capacitor (BC), based on the genetic algorithm (GA) and in the use of Sensitivity Analysis (SA). The AS is used to evaluate the candidate solutions directly instead of using a Optimal Power Flow (OPF), which is an iterative method. The proposed methodology was applied on three distribution systems, containing 34, 70 bus, respectively. Scenarios were analyzed for the insertion of two units of BC in each system. The proposed methodology AG - AS was compared with exhaustive methodology, solved by only OPF method and the gain in computational processing time is showed. As a main result, it was obtained the best locations for placement of BC units considering the minimization of real power losses, and consequently an improvement in the voltage levels in the buses of the system.

Sensitivity Analysis Applied on the Electrical Power Systems Operation Planning

This paper proposes a study of electrical power system operation planning by Sensitivity Analysis (SA). The SA implemented was oriented by Optimal Power Flow (OPF). An optimal operation point was obtained by OPF. If some perturbation occurs in the power system, a new operation point will have to be evaluated to keep the feasibility of the power grid. This new operation point will be evaluated by SA. The SA was methodologically based in the theorem proposed by Fiacco. The set of non-linear equations generated by SA was solved by Newton´s method. Sparsity techniques were used. The principals contributions of this paper are the inclusion of transmission line constrained in the SA model and the complete use of the Fiacco´s theorem. Studies of cases were carried out in the IEEE 14, 118 and 300 buses, where the efficiency of the SA was verified.

Transmission loss allocation by sensitivity approach

This paper presents an approach to the allocation of transmission losses to the agents of a power system operating under pool conditions, which consider all the operational constraints of the system. The approach belongs to the family of incremental methods of allocation. The technique is based on the perturbation of optimum theorem, which works with a Lagrangian function associated with the perturbed problem. Starting from an optimal operating point obtained by solution of an optimal power flow problem, the new optimal operating point that satisfies constraints after making a small increment in the loads is calculated directly. This solution is used to obtain the allocation coefficients of the losses for the generators and loads of the system. Numerical results are obtained for the well-known transmission networks, IEEE 14-bus and IEEE 30-bus, to illustrate the approach.

Analysis of Reactive Power Support From Wind Generators as Ancillary Service Providers

This paper proposes the use of wind generators for the provision of reactive power support as ancillary service, The reason behind this proposal is the ability of some of these generators to operate with variable power factor, It was considered the analysis of a set of DFIG (Doubly Fed Induction Generator) generators with power factor ranging up to the limit of 0,95 compared to a set of DFIG generators with power factor equal to 1,0, i,e, without reactive power support capability, Therefore, the formulation of an optimal power flow so as to analyze the reactive power supplied by the set of wind generators providing this ancillary service to the reduction of transmission losses was used.