A methodology for the efficient computer representation of dynamic power systems : application to wind parks

This contribution presents a methodology to efficiently obtain the numerical and computer solution of dynamic power systems with high penetration of wind turbines. Due to the excessive computational load required to solve the abc models that represent the behavior of the wind turbines, a parallel processing scheme is proposed to enhance the solution of the overall system. Case studies are presented which demonstrate the effectiveness and applications of the proposed methodology

Comparative study of 220 kV overhead transmission lines models subjected to lightning strike simulation by using electromagnetic and alternative transients program

Introduction. In high voltage networks intended for the transport of electrical energy, lightning can strike an electric line striking either a phase conductor, a pylon or a ground wire, causing significant overvoltage on the transmission lines classified as stresses the most dangerous for transformer stations and electro-energy systems in general. Modeling transmission lines becomes more complicated, if the frequency dependence of resistance and serial inductance due to the effect of lightning strike in the conductors and in the earth is considered. The difficulty increases the fact that the parameters of the line can be defined and calculated only in the frequency domain, while the simulation of transients is wanted to be in the time domain. Problem. Several models (J.R. Marti, Bergeron, nominal PI, Semlyen and Noda) exist for the modeling of transmission lines, the Electromagnetic Transients Program/Alternative Transient Program software (EMTP/ATPDraw) gives the possibility to choose between these models which is delicate due to the fact that we do not have experimental results to validate and justify the choice among the models available in the software. In this context, practical value: the overhead transport line OAT-El Hassi (220 kV) of the city of Sétif located in the north east of Algeria is used for the modeling of lightning strike by using the EMTP/ATPDraw software. Originality. A comparative study of the investigation of a lightning strike on an existing high voltage transmission line by different models of existing lines in the EMTP/ATPDraw software library of this software. Results. It was concluded that the choice of the model of the line is very important given the accuracy and quality of the curves of the voltage presented at the different calculation points. Вступ. У високовольтних мережах, призначених для передачі електроенергії, блискавка може вдарити по лінії електропередач, уразивши або фазний провід, опору, або заземлюючий провід, викликаючи значні перенапруги на лініях електропередач, визначені як загрози, найбільш небезпечні для трансформаторних підстанцій та електроенергетичних систем загалом. Моделювання ліній електропередач ускладнюється, якщо враховувати частотну залежність опору та послідовної індуктивності внаслідок дії удару блискавки у провідниках та землі. Складність підвищується тим, що параметри лінії можуть бути визначені і розраховані тільки в частотній області, в той час як моделювання перехідних процесів бажано проводити в часовій області. Проблема. Існує кілька моделей (J.R. Marti, Bergeron, номінальна П-подібна схема заміщення, Semlyen і Noda) для моделювання ліній електропередач, комп‘ютерна  програма електромагнітних перехідних процесів/альтернативна програма перехідних процесів EMTP/ATPDraw дає можливість вибирати між цими моделями, що є «тонким питанням» через те, що ми не маємо експериментальних результатів для перевірки та обґрунтування вибору серед моделей, доступних у програмному забезпеченні. У цьому контексті, практична цінність: для моделювання удару блискавки за допомогою програмного забезпечення EMTP/ATPDraw використана повітряна лінія електропередачі ОАТ-Ель-Хассі (220 кВ) міста Сетіф, розташованого на північному сході Алжиру. Оригінальність. Порівняльне дослідження вивчення удару блискавки на існуючій високовольтній лінії електропередач за різними моделями існуючих ліній у бібліотеці програм  EMTP/ATPDraw цього програмного забезпечення. Результати. Зроблено висновок, що вибір моделі лінії дуже важливий з урахуванням точності та якості кривих напруг, представлених у різних розрахункових точках.

Multiscale simulation of frequency dependent line models and network equivalents

The evaluation of power systems encompasses phenomenon of distinct timeframes and so leads to the adoption of different simulation tools. For instance, fast transients related to switching maneuvers require time-steps of microseconds while slow transients, related to energy exchange between generators, demand timesteps of milliseconds. However, the need to assess conditions where slow frequency oscillations might be combined with fast transients is becoming more common. This research evaluates the use of frequency dependent admittance-based models in the development of multiscale algorithms for phase-coordinate modeling of overhead lines, subsea cables and frequency dependent network equivalents. Unlike the modeling with the Method of Characteristics, the direct fitting of the nodal admittance matrix and two alternative schemes are considered to cope with the trade-off between time-step and traveling times, namely: the Folded Line Equivalent and Idempotent Decomposition. The concept of Latency is also addressed in a distinct way to provide more efficient realization frequency dependent models to allow the so-called multirate simulation. The major advantage of the designed models is the straightforward implementation in EMTP-like programs such as PSCAD, EMTP-RV and ATP since they attain the same Norton-type structure. In addition, dynamic phasors allowed the unification of electromagnetic and electromechanical modeling into a single model. Both numerical performance and accuracy of the proposed schemes are evaluated through several test cases. The Method of Characteristics and the Numerical Laplace Transform are used for comparison. The computational burden is considerably reduced without significant loss of accuracy and with no numerical oscillations or discontinuities in the waveforms.A análise de sistemas elétricos engloba fenômenos com diferentes constantes de tempo, o que acarreta na utilização de diversas ferramentas de simulação. Como exemplo, transitórios rápidos envolvendo surtos de manobra demandam passos de integração na ordem de microssegundos enquanto para transitórios lentos, advindos da troca de energia entre geradores, adotam-se passos de integração de milissegundos. O presente trabalho investiga a utilização de modelos baseados em matrizes de admitância variantes na frequência para representação de linhas de transmissão aéreas, cabos submarinos e equivalentes de rede em coordenadas de fase para o desenvolvimento de algoritmos para simulação multiescala. Ao invés da utilização do Método das Características, a matriz de admitância nodal e duas decomposições alternativas são consideradas de modo a contornar a limitação do passo de integração em função do tempo de tráfego de linhas, a saber: o Folded Line Equivalent e a Decomposição Idempotente. O conceito de Latência será também investigado de modo a prover uma realização mais eficiente de modelos variantes na frequência. As formulações desenvolvidas neste trabalho encontram aplicação imediata em programas para simulação de transitórios eletromagnéticos, tais como PSCAD, EMTP-RV e ATP dado que é mantida a representação através dos equivalentes de Norton. Por meio de fasores dinâmicos, torna-se viável a representação de fenômenos eletromagnéticos e eletromecânicos com o mesmo modelo computacional. Casos teste são empregados na avaliação do desempenho e precisão das formulações propostas. O Método das Características e a transformada numérica de Laplace são utilizados para fins de comparação. Com reduzido esforço computacional, resultados com excelente precisão são obtidos sem a presença de oscilações numéricas ou descontinuidades nas formas de onda

Graphics-processing-unit-based acceleration of electromagnetic transients simulation.

This paper presents a novel parallelization approach to speedup EMT simulation, using GPU-based computing. This paper extends earlier published works in the area, by exploiting additional parallelism to accelerate EMT simulation. A 2D-parallel matrix-vector multiplication is used that is faster than previous 1D-methods. Also this paper implements a simpler GPU-specific sparsity technique to further speed up the simulations as available CPU-based sparse techniques are not suitable for GPUs. Additionally, as an extension to previous works, this paper demonstrates modelling of a power electronic subsystem. A low granularity system, i.e. one with a large cluster of busses connected to others with a few transmission lines is considered, as is also a high granularity where a small cluster of busses is connected to other clusters thereby requiring more interconnecting transmission lines. Computation times for GPU-based computing are compared with the computation times for sequential implementations on the CPU. The paper shows two surprising differences of GPU simulation in comparison with CPU simulation. Firstly, the inclusion of sparsity only makes minor reductions in the GPU-based simulation time. Secondly excessive granularity, even though it appears to increase the number of parallel computable subsystems, significantly slows down the GPU-based simulation

Application of Numeric Routine for Simulating Transients in Power Line Communication (PLC) Systems

Applying numerical routines based on trapezoidal rule of integration (Heun’s method for numerical integration), simple models of transmission lines are used to analyze and simulate the propagation of communication signals in PLC-type systems (power line communication systems). Such systems are shared by the same systems for the transfer of electrical power and signal transmission. For the mentioned routines, the main objectives are: simulate the propagation of electromagnetic transients in these systems and analyze the interference of such phenomena in the transmitted signal. Such simulations are performed with classical structures that represent infinitesimal units of transmission lines. Modifications in the structure of such units are analyzed to improve the results obtained by the mentioned simulations

Phase domain transmission line modelling for EMTP-type studies with application to real-time digital simulation

This research project is primarily concerned with the development of a new generation of power transmission lines for both non-real-time and real-time electromagnetic transient studies. The method proposed is entirely formulated in phase co-ordinates, avoiding the use of modal transformation matrices at every stage in the analysis. In comparison, the phase domain models presented thus far in the open literature have all incorporated the concept of modal decomposition in the initial frequency domain formulation of the problem. Only the time domain analysis is conducted in the phase domain. These models can therefore be regarded as a hybrid between the phase and modal methodologies. Algorithms are presented which allow accurate and efficient determination of the characteristic admittance matrix, Yc(), and wave propagation matrix, H(), directly in phase co-ordinates. A Padé iteration scheme is used for evaluating the characteristic admittance matrix, derived by exploiting a relationship between the matrix sign function and the matrix square root. Padé techniques have also been used to approximate the matrix exponential in order to evaluate the wave propagation function. By evaluating Yc() and H() directly in phase co-ordinates, any imbalances naturally present in the line will intrinsically be taken into account in these functions. Both methods have been extensively tested using line configurations of different size and complexity and both algorithms are shown to be very robust, accurate and efficient in all cases. One of the main difficulties in formulating the analysis entirely in phase co-ordinates for multiconductor systems concerns the unwinding of the wave propagation matrix. This is addressed in this research by evaluating a matrix phase shift function in phase co-ordinates. Since the method inherently takes into account the coupled time delays of the line, the elements of H() can be successfully unwound, irrespective of the configuration of the line, e.g. single-circuit, multi-circuit or asymmetrical

Power quality and electromagnetic compatibility: special report, session 2

The scope of Session 2 (S2) has been defined as follows by the Session Advisory Group and the Technical Committee: Power Quality (PQ), with the more general concept of electromagnetic compatibility (EMC) and with some related safety problems in electricity distribution systems. Special focus is put on voltage continuity (supply reliability, problem of outages) and voltage quality (voltage level, flicker, unbalance, harmonics). This session will also look at electromagnetic compatibility (mains frequency to 150 kHz), electromagnetic interferences and electric and magnetic fields issues. Also addressed in this session are electrical safety and immunity concerns (lightning issues, step, touch and transferred voltages). The aim of this special report is to present a synthesis of the present concerns in PQ&EMC, based on all selected papers of session 2 and related papers from other sessions, (152 papers in total). The report is divided in the following 4 blocks: Block 1: Electric and Magnetic Fields, EMC, Earthing systems Block 2: Harmonics Block 3: Voltage Variation Block 4: Power Quality Monitoring Two Round Tables will be organised: - Power quality and EMC in the Future Grid (CIGRE/CIRED WG C4.24, RT 13) - Reliability Benchmarking - why we should do it? What should be done in future? (RT 15

Time domain analysis of switching transient fields in high voltage substations

Switching operations of circuit breakers and disconnect switches generate transient currents propagating along the substation busbars. At the moment of switching, the busbars temporarily acts as antennae radiating transient electromagnetic fields within the substations. The radiated fields may interfere and disrupt normal operations of electronic equipment used within the substation for measurement, control and communication purposes. Hence there is the need to fully characterise the substation electromagnetic environment as early as the design stage of substation planning and operation to ensure safe operations of the electronic equipment. This paper deals with the computation of transient electromagnetic fields due to switching within a high voltage air-insulated substation (AIS) using the finite difference time domain (FDTD) metho

Detailed modelling and analysis of digital mho distance relay with single-pole operation

This paper introduces a methodology for modelling a digital admittance-type distance relay using PSCAD/EMTDC. The proposed distance relay was tested in a simulation of the Brazilian power grid with predetermined fault scenarios. The goal of this paper is to make a detailed evaluation of the mho distance relay. The main aspects include the correct operation of the distance relay, fault resistance effects on the mho characteristics, and the fault detection time of this relay. A new approach to analyse the fault detection time is presented, considering several simulated fault scenarios. The results demonstrate that the fault resistance influences the fault detection time and severely affects the distance relay’s general performance. The fault detection time is not constant. It varies within a time interval, considering different fault types, fault locations, and fault resistances. The confidence interval calculation provides a detailed range of the fault detection time, considering its upper and lower limits

Influences of damping resistances on transient simulations in transmission lines

Simulations of electromagnetic transients in transmission lines can be carried out using simple circuit model. In the case of applications of simple circuit models based on π circuits, there are problems mainly caused by numeric oscillations. The lumped-parameter π equivalent model can be used with some advantages. The numeric integration method applied to the simulations of electromagnetic transients is the trapezoidal rule. If this numeric method is associated with the π equivalent model, results obtained from the simulations are distorted by Gibbs' oscillations or numeric ones. The introduction of damping resistance parallel to the series RL branch of the π equivalent model can mitigate Gibbs' oscillations in obtained results. Voltage peaks caused by these oscillations can also be decreased. So, in this paper, the combined in uences of the introduction of damping resistance, the number of π circuits and the time step are investigated searching for minimizing Gibbs' oscillations and the voltage peaks in electromagnetic transient simulations. For this, transient simulations are exhaustively carried out for determining the highest voltage peaks, ranges of damping resistances and other parameters of the model, which minimize these voltage peaks caused by Gibbs' oscillations752739FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP2015/21390-