Pavel Zuniga

Vulnerability Analysis of Power Grids Using Modified Centrality Measures

The aim of this paper is to propose modified centrality measures as a tool to identify critical nodes before a vulnerability analysis is performed in an electrical power grid. Pair dependency centrality is weighted using the grid active power flow, and this becomes the basis to define closeness and betweenness of its nodes, and hence to identify the most critical ones. To support the idea of using modified centralities, four power grids are tested to be either exponential or scale-free. To evaluate the proposal, information obtained via modified centrality measures is used to calculate global efficiency of the power grids.

Ground-Impedance Graphic Analysis Through Relative Error Images

This paper proposes a contour image-based graphic method useful to estimate the relative error between approximate ground-impedance models and the algorithmic solution of the Carsons integral over a wide ranges of frequencies and soil conductivities for any overhead transmission-line configuration.

Synchronous Generator Emulator Prototype as a Testbed for Electric Equipment

The aim of this study is to describe a synchronous generator emulator prototype based on a three-phase power electronics converter. The physical structure of the emulator and its relation with the generator mathematical model is described. A voltage-behind-reactance model is used to reproduce the behavior of the generator. Comparison of experimental results against simulations confirms the validity of the proposal.

Efficient Truncation Criterion for the Parameter Estimation of a Stratified Ground Block

A truncation criterion to solve the vector potential integrals proposed by Takahashi and Kawase is described in this letter. The main aim of those integrals is to estimate the depth and resistivity parameters of a stratified ground block. The derivation of the proposed criterion considers the error introduced by the infinite limit truncation of the integrals. In addition, an efficient solution can be obtained by the use of the trapezoidal rule of integration.

Improvement of damping impedance method for Power Hardware in the Loop simulations

The aim of this study is to present an improvement of the Damping Impedance Method (DIM) Interface Algorithm for Power Hardware in the Loop (PHIL) simulations. The improvement is based on the calculation of the Hardware Under Test (HUT) impedance, in order to include it as part of the Damping Impedance Method to enhance its accuracy and stability. To verify the results, the improved DIM interface is simulated using MATLAB/Simulink, furthermore, a laboratory implementation of a PHIL simulation is carried out using a variable load. The stability of the interface algorithm is graphically observed using the Nyquist and Bode stability criteria, whereas the precision is validated through simulations that compare the Mean Square Error (MSE), as well as laboratory experiments.

Droop controller comparison for AC microgrids

The aim of this study is to analyze and compare three droop controller schemes to regulate the operation of a microgrid. Three droop control schemes are selected because of their capability to regulate voltage, frequency and power sharing without using communication links and complex measurement systems. Specifically, the conventional droop controller and two of its variants are compared, the angular and robust controllers. An analysis regarding their differences is given in terms of voltage, frequency, and power sharing performance.

Phase compensation scheme to improve the accuracy of a power hardware-in-the-loop experiment based on a synchronous generator

The aim of this study is to present a phase compensation scheme that improves the accuracy of a power hardware-in-the-loop simulation. The ideal transformer model interface method along with feedback current filtering is used to connect a synchronous generator simulation to a test system. The generator is modeled using a voltage-behind-reactance representation. Comparison of experimental results against simulations confirms the validity of the proposal.

Identification of weak buses for proper placement of reactive compensation through sensitivity analysis using a neural network surrogate model

The aim of this work is to present a surrogate model appropriate for carrying out sensitivity analysis studies. The surrogate model is obtained using a radial basis functions neural network. The study is based on the sensitivity of the overall power system bus voltage magnitudes to reactive power change. The objective is to locate a suitable power system bus for reactive compensation. To validate the proposed method, a power flow based sensitivity analysis is carried out in a power system in order to identify the most vulnerable bus. The findings can be used to identify buses where reactive power compensation can have the most impact. Simulation results are presented that confirms the validity of the proposal.

Autotuning technique for droop controllers to mitigate voltage and frequency deviations caused by load changes

The aim of this paper is to explain a novel technique to improve voltage and frequency profiles on microgrids controlled using the droop control scheme. The method consists on retuning the controller according to the present load scenario by adjusting the droop coefficients in a way that is proportional to the load changes. The proposed technique is tested through numerical simulations and the results show a significant improvement on the quality of voltage and frequency profiles, as well as in other important operating parameters of a microgrid. The proposed scheme can lead to a widening on the scope of droop based controllers within microgrids and renewable energy systems.

Analysis of harmonic and inter-harmonic signals through generalized-Fourier series

A harmonic and inter-harmonic signal analysis technique is presented in this paper. The technique consists in the use of The Fourier Theory for synthesizing harmonic signals and the use of two generalized-Fourier approximations based in different orthogonal basis for inter-harmonic signals. A numerical example yields that polynomial Chebyshev and Legendre function approximations can be very efficient to analyze inter-harmonic signals in a very short running time.