Abilio Manuel Variz

Improved representation of control adjustments into the Newton -Raphson power flow

Abstract This paper describes a sparse (4 n ×4 n ) formulation for the solution of power flow problem, comprising 2 n current injection equations written in rectangular coordinates plus the set of control equations. This formulation has the same convergence characteristics of the conventional Newton power flow problem, expressed in terms of power mismatches written in polar coordinates and can be reduced to a (2 n ×2 n ) formulation plus the control equations. It is best suited to the incorporation of flexible AC transmission system devices and controls of any kind. Complex user-defined control functions, involving the participation of several regulating devices, can be directly introduced as power flow control data. The results presented validate the proposed method.

Harmonic analysis of the power distribution Neutral-to-Earth Voltage (NEV) test case using four-wire three-phase harmonic current injection method

This work presents several harmonic analyses using the Four-Wire Three-Phase Harmonic Current Injection Method (FHCIM) to simulate the Power Distribution Neutral-to-Earth Voltage (NEV) Test Case. FHCIM is a fast and reliable Newton-Raphson multi-frequency power flow methodology to simulate unbalanced three-phase electric power systems with explicit representation of the network characteristics and components, including the harmonic couplings of non-linear loads as well as neutral conductors and groundings. The NEV test case is a radial distribution network in which the neutral voltages and currents present an important role due the system unbalances, grounding impedances and neutral conductors. Harmonic distortion on real networks, are due to the proliferation of non-linear loads, and can affect both neutral-to-earth voltage levels and neutral currents. Therefore, a digital tool for harmonic analysis is becoming very important for planning studies of electrical power systems. Simulations of the original NEV test case with unbalanced 3rd harmonic loads, as well as a modified case with non-linear loads, represented by SVCs, were carried out with the purpose of investigating the presence of a wide harmonic propagation spectrum.

Cálculo do fluxo de harmônicos em sistemas de potência trifásicos utilizando o método de injeção de correntes com solução iterativa

Este trabalho apresenta uma metodologia, baseada nas equacoes de injecao de correntes (MICT), para o calculo do fluxo de potencia harmonico trifasico em sistemas eletricos equilibrados e desequilibrados (MICTH). A metodologia desenvolvida emprega o metodo iterativo de Newton-Raphson para obter a solucao do sistema de equacoes nao-lineares, onde o sistema matricial e formado por blocos relativos as frequencias harmonicas investigadas. Dessa maneira e possivel representar as interacoes entre as componentes harmonicas de diferentes frequencias. Em paralelo foram desenvolvidos modelos dos principais dispositivos lineares e nao-lineares conectados aos sistemas eletricos de potencia. O MICTH (Metodo de Injecao de Correntes Trifasicas Harmonicas) e os modelos de componentes foram implementados em C++, com programacao orientada a objetos, e utilizando tecnicas de programacao esparsa. Os resultados das simulacoes, no dominio da frequencia, obtidos com o programa MICTH foram validados a partir de comparacoes com resultados de simulacoes, no dominio do tempo, obtidos com o programa ATP/EMTP (Alternative Transients Program of Electromagnetic Transients Program).

Harmonic state estimation for distribution systems based on synchrophasors

This paper describes a harmonic state estimation technique for unbalanced three-phase distribution systems using Phasor Measurement Units (PMUs), considering the presence of non-linear loads connected to the system. In the proposed approach, the measured phasor values are harmonic voltages and branch currents in those buses continuously monitored by PMUs. For the non-monitored buses, their loads are represented by a set of bounded inequality constraints in a proposed constrained optimization problem. The state variables to be estimated by the methodology are harmonic branch currents in rectangular coordinates. The method is capable of estimating harmonic components in distribution feeders and power quality indicators such as THD (Total Harmonic Distortion). A modified IEEE 33-bus test system is used to validate the proposed methodology.

A PMU-based distribution system harmonic state estimation using parallel processing

This paper presents a novel approach for harmonic state estimation for a real-time power quality management in distribution networks using Phasor Measurement Units (PMUs). In the developed methodology, the PMUs measure voltages and currents signals with harmonic distortion in those buses which are continuously monitored by these meters. Load historical data are considered for the non-monitored buses. They are treated as bounded inequality constraints with predefined upper/lower limits in a proposed constrained non-linear optimization problem. A modified IEEE 33-bus test system is used to validate the proposed methodology and the use of parallel processing is discussed for the real-time applications in harmonic monitoring.

Allocation of power harmonic filters using Genetic Algorithm

In this paper it is confirmed that the placement of harmonic filters in power systems is not a trivial task. Although it seem obvious the allocation of filters in the buses with the biggest harmonic distortions and/or with the largest harmonic sources, it is going to be proven that these choices are not the best solution regard the network operation and the importance of some areas. The decision criterion in the present problem has the objective to minimize the network average distortion. The presented methodology also uses associated weight for each bus to categorize the most important network nodes and areas. The proposed methodology uses the three-phase harmonic current injection method with Newton-Raphson iterative solution (THCIM) associated with Genetic Algorithm (GA).

Novos desenvolvimentos numa formulação de injeção de corrente para solução do fluxo de potência

This paper presents a generic methodology of control devices representation into the power flow problem, using a sparse Newton Raphson formulation expressed in terms of current injection equations in rectangular coordinates. This formulation yields the same convergence characteristics presented by power mismatches conventional formulation in polar coordinates. The results validate the proposed methodology.

Power distribution systems planning with distributed thermal and wind generation

This paper presents a new approach for distribution systems planning with thermal and wind distributed generation (DG). This approach determines the optimal placement of biomass-based thermal and wind distributed generation aiming at minimizing the energy loss, emissions and the total investment and operation costs, as well as improving the voltage regulation. The costs for the purchased energy from grid and thermal generation based on biomass resource are considered. The wind power is given by pre-established nominal power and capacity factor. To solve the mixed integer nonlinear problem, a genetic algorithm (GA) with embedded optimal power flow (OPF) tool is proposed. The OPF is used to determine the size of the thermal generators. Results are presented for well-known systems from literature.

Modelagem do elo de corrente contínua no domínio da frequência em sistemas assíncronos desequilibrados

This work proposes the modeling of High Voltage Direct Current Link (HVDC) for harmonic analysis in AC electrical power systems using frequency domain formulation with complete and explicit representation of the AC and DC networks, as well as, the converters non-linear characteristics and their harmonic interdependences. The proposed model development is based on the Three-phase Harmonic Current Injection Method (THCIM) and it allows the systemic simulation of AC networks with DC link of high complexity, as 12-pulse converter systems and asynchronous AC connection. The proposed model simulation results, in frequency domain, were validated against ATP (Alternative Transients Program) results, in time domain simulation.