Voltage Electrical Networks Research Articles

Extension algorithm for generic low-voltage networks

Distributed energy resources (DERs) are increasingly penetrating the energy system which is driven by climate and sustainability goals. These technologies are mostly connected to low- voltage electrical networks and change the demand and supply situation in these networks. This can cause critical network states. Network topologies vary significantly and depend on several conditions including geography, historical development, network design or number of network connections. In the past, only some of these aspects were taken into account when estimating the network investment needs for Germany on the low-voltage level. Typically, fixed network topologies are examined or a Monte Carlo approach is used to quantify the investment needs at this voltage level. Recent research has revealed that DERs differ substantially between rural, suburban and urban regions. The low-voltage network topologies have different design concepts in these regions, so that different network topologies have to be considered when assessing the need for network extensions and investments due to DERs. An extension algorithm is needed to calculate network extensions and investment needs for the different typologies of generic low-voltage networks. We therefore present a new algorithm, which is capable of calculating the extension for generic low-voltage networks of any given topology based on voltage range deviations and thermal overloads. The algorithm requires information about line and cable lengths, their topology and the network state only. We test the algorithm on a radial, a loop, and a heavily meshed network. Here we show that the algorithm functions for electrical networks with these topologies. We found that the algorithm is able to extend different networks efficiently by placing cables between network nodes. The main value of the algorithm is that it does not require any information about routes for additional cables or positions for additional substations when it comes to estimating network extension needs.

Analysis And Study On Distribution Of Defect Electric Field On Basin-type Insulator In GIS

With the increase of electric network voltage in power system, the internal discharge phenomenon of gas insulated substation (GIS) during operation often happens. In this paper, a 3-D simulation model of GIS with metal protrusion on basin-type insulator was utilized to study the effect of metal protrusion on the electric field distortion in GIS. It can be concluded from simulation results that the electric field increases with the height of metal protrusion when the radius is constant, while decrease with the increase of radius of metal protrusion. In addition, the metal protrusion near high voltage conductor lead to more severe electric field distortion than that near grounded enclosure. This work is of significance for the actual operation and maintenance of GISs in the power system.

Planificación y Diseño Automático Óptimo de Grandes Redes Eléctricas de Distribución: Aplicación al Centro Histórico de Quito

El presente trabajo describe la herramienta computacional desarrollada por CoDyPower (CDP) para la planificación automática óptima de grandes redes eléctricas de distribución. El objetivo principal es el diseño de redes eléctricas que minimicen el coste económico de la instalación y operación. La función de coste a optimizar tiene en cuenta el número y tipo de subestaciones, la longitud y tipo de conductores, la instalación de líneas aéreas o subterráneas y los costes de operación y pérdidas en un horizonte temporal dado. La optimización considera la geometría de las calles, los catálogos de transformadores y cables disponibles para el proyecto, las restricciones de distancias, caídas de tensión, corrientes y potencias máximas. Debido al carácter computacional NP-hard del problema, el software aplica estrategias de inteligencia artificial y de estadística, fraccionando el problema en etapas de macro y micro optimización. Con ello se encuentra un camino viable de cálculo en tiempos de computación accesibles. Además, los algoritmos propuestos son capaces de encontrar soluciones multi-circuito para cada transformador. El presente trabajo muestra también la aplicación del software CDP al diseño y planificación de las redes eléctricas de distribución de baja y media tensión del Centro histórico de Quito, con unos 20.000 usuarios. Los resultados obtenidos cumplen todas las especificaciones y reducen en aproximadamente un 40% el coste inicialmente estimado.

DVR시스템에 사용되는 인버터부의 LC필터 설계와 피드백 성능분석

Voltage sags are considered the dominant disturbances affecting power quality. Dynamic voltage restorers(DVRs) are mainly used to protect sensitive loads from the electrical network voltage disturbances such as sags or swells and could be used to reduce harmonic distortion of ac voltages. The typical DVR topology essentially contains a PWM inverter with LC Filter, an injection transformer connected between the ac voltage line and the sensitive load, and a DC energy storage device. For injecting series voltage, the PWM inverter is used and the passive filter consist of inductor(L) and capacitor(C) for harmonics elimination of the inverter. However there are voltage pulsation responses by the characteristic of the LC passive filter that eliminate the harmonics of the PWM output waveform of the inverter. Therefore, this paper presented design and feedback performance of LC filter used in the DVRs. The voltage control by LC filter should be connected in the line side since this feedback method allows a relatively faster dynamic response, enabling the elimination of voltage notches or spikes in the beginning and in the end of sags and strong load voltage THD reduction. Illustrative examples are also included.

Physical Modeling of Secondary Arcing at Environmental Pressures in the Range from Atmospheric to Vacuum

An electrical breakdown in the onboard equipment of orbital space vehicles is a consequence of multifactor physical process related to vacuum electronics, low-temperature plasma physics, and gas discharge. The problem becomes especially urgent in connection with the application of an onboard electrical network voltage of 100 V and higher that exceeds the arcing threshold. The given problem is being actively investigated for more than 10 years; as a result, a number of standards regulating measures on prevention of secondary arcing as a consequence of electrostatic breakdown are currently in force in the world. However, arcing caused by internal processes in onboard equipment without high-voltage initiation has not yet practically been studied, despite the existence of such problem that makes these investigations urgent. The present work contains results of experiments on registration of the threshold parameters, first of all, the pressure that determines the risk of secondary arcing in the presence of the plasma imitating the primary discharge plasma and caused by wire evaporation. Results of experiments confirm the expected decrease of the threshold breakdown voltage below the minima of the Paschen curve. Experimental approaches used in this work are of methodological interest for imitation of arcing conditions and testing of stability of the equipment against arcing in orbital space.

Optimal mix of solar and wind distributed generations considering performance improvement of electrical distribution network

Renewable energy sources are gaining more and more interest because they are nonpolluting and sustainable. Recently, a notable number of renewable distributed generations (DGs) having intermittent generation patterns are being interconnected with the distribution network to meet growing load demand and nullify environmental threats. Appropriate integration of renewable DGs in distribution networks is crucial to guarantee the qualitative network operational benefits. In this paper a simple but efficient approach has been proposed for optimal placement and sizing of solar and wind DGs in distribution territory by considering electrical network power loss minimization, voltage stability and network security improvement. The stochastic nature of solar irradiance and wind speed are accounted using suitable probabilistic models. Weighted aggregation particle swarm optimization technique is employed to optimize the objective functions considering bus voltage limit, line loading capacity, discrete size limit and penetration constraints of DGs. Strategic weight selection technique has been adopted to assess the well trade-off solution by persuasion of multiple objectives regarding the performance of distribution network. The proposed method has been applied to a typical Indian rural distribution network, and the satisfactory results are obtained.

A New Method to Solve Static Voltage Collapse Point with Hybrid Power Network Equations

Electric power network components can be simulated with equivalent circuit and establish the hybrid node voltage and branch current electricity network analysis model based on it. We form the equations reflected the voltage collapse conditions, and establish the extended power flow equations with the hybrid equations, the static voltage collapse point can be calculated by solving them. The advantage of this method is that the power flow calculation can be convergence smoothly near the collapse point because of the extended power flow equations when the Jacobian matrix tends to be singular. The convergence can be achievable just because the joining of the equation reflecting the voltage collapse conditions has changed the structure of the Jacobian matrix. The simulation results show that this method is very effective.

Evolutionary approach to optimisation of the operation of electric power distribution networks

An idea of using a classifying system and co-evolutionary algorithm for operation support of electric power distribution systems operators has been presented in the paper. The method proposed by the author of the work is typified by the short time of designating the most rational post breakdown configurations in complex electric power Medium Voltage distribution network structures. It is the use by the classifying system working with the co-evolution algorithm that enables the effective creation of substitute scenarios for the Medium Voltage electric power distribution network. The method drawn up may be used in current systems managing the work of distribution networks to assist network operators in taking decisions concerning connection actions in supervised electric power systems.

OPTIMAL FEATURE SET AND PARAMETER SELECTION FOR POWER QUALITY DATA MINING

The significance of detection and classification of power quality (PQ) events that disturb the voltage and/or current waveforms in electrical power distribution networks is well known. Consequently, in spite of a large number of research reports in this area, research on the selection of useful features from the existing feature set and the parameter selection for specific classifiers has thus far not been explored. The choice of a smoothing parameter for a probabilistic neural network classifier (PNN) in the training process, together with feature selection, will significantly impact the classification accuracy. In this work, a thorough analysis is carried out, using two wrapper-based optimization techniques—the genetic algorithm and simulated annealing—for identifying the ensemble of celebrated features obtained using discrete wavelet transform together with the smoothing parameter selection of the PNN classifier. As a result of these analyses, the proper smoothing parameter together with a more useful feature set from among a wider set of features for the PNN classifier is obtained with improved classification accuracy. Furthermore, the results show that the performance of simulated annealing is better than the genetic algorithm for feature selection and parameter optimization in Power Quality Data Mining.

Study on Hybrid Filtering Solution for Marine Electric Network

Study on Hybrid Filtering Solution for Marine Electric NetworkThis paper presents a Hybrid APF/PFC/PPF Circuit (active power filtering and power factor correction circuit aided by shunt passive filter) for harmonic suppression and power factor correction in a marine electric network. By employing the proposed hybrid circuit, marine electric power network voltage and current can be maintained as being sinusoidal, and the power factor is close to 1. The effectiveness of the proposed method that is applied to a marine electric network is demonstrated through a simulation experiment. The results show that the expected performances are achieved.

DC Motor Velocity Adaptive Control through Buck-Boost AC/DC Converter with Power Factor Correction

This paper deals with the problem of velocity control of DC motors taking account the dynamics of the involved power converter. The latter is an AC/DC Buck Boost type. First, a 6th order model is developed for the global system, constituted of the motor and the converter. Based on this model, a regulator is then designed, using the backstepping technique, to achieve speed regulation and unitary power factor operation. The proposed regulator involves three loops: (i) an inner current control loop enforcing the converter input current to be in phase with the electric network voltage (unitary power factor), (ii) an outer speed control loop that regulates the machine velocity, (iii) a parameter adaptation loop that compensates the load torque uncertainty. The resulting multi-loop adaptive nonlinear regulator is formally proved to meet its objectives. This is further checked by simulation.

Multiple Model Filtering for the Detection of Transformer Ratio Changes in Electric Power Systems

Multiple model filtering approach is used for transformer ratio change detection and estimation in electric power systems. Transformers with variable transformer ratios are considered separately from the other part of electric network and power flow and voltage magnitude measure-ments are used for estimation purposes. The performance of the presented algorithm is examined using measurements from a real-life power system.