Search results for "AC power"
showing 10 items of 92 documents
Inertial response of isolated power networks with wind power plants
2019
The constant increase of power generation provided by renewable energy source (RES) power plants is causing a progressive reduction of the overall inertia of the power systems. Especially in the case of small, isolated power networks, the replacement of conventional generation plants with RES power plants can affect significantly the frequency response of the system. The critical low-inertia conditions can be improved by the introduction of specific additional controls to the RES power converters. These control schemes are known as “synthetic inertia” or “virtual inertia” controls. The paper analyzes the impact of a derivative-based inertial control on a small, isolated power system, with a…
Integration Issues of Distributed Generators Considering Faults in Electrical Distribution Networks
2014
In the recent years there is a great interest in integration of distributed generation (DG) units at distribution level; this integration leads to planning as well as operational challenges. Some possibilities to handle grid planning issues are addressed in this paper. Effects on grid protection, fault current level, and voltage profile are investigated and described for different types of DG units; the classification of DG units is based on their terminal characteristics in terms of real and reactive power delivering capability. Different scenarios for mis-coordination problems caused by DG interconnection are discussed. The effect of the DG on the voltage profile of a distribution network…
A Simulation Analysis of VSM Control for RES plants in a Small Mediterranean Island
2020
The paper presents an application of Virtual Synchronous Machine control for managing inverter-interfaced renewable energy sources in a small Mediterranean island not supplied by the main grid. In the proposed analysis, the island's renewables-based generators area assumed interfaced to the grid by voltage source converters with a swing controller and a vector-current controller with two different options for the reference current for regulating the voltage at the Point of Common Coupling and the active power output. The system, modeled in PScad environment, allows to verify the response of the renewables-based generators with VSM control in the presence of a fault in the grid.
Influence of losses partition criteria on power flow tracing
2012
The paper proposes a methodology for tracing active power flow which also considers power losses partition. It requires the partition of the active power losses in each line over different flow components. Then, the differences arising from the selection of different criteria for the allocation of the mutual terms (deriving from the non-linearity of losses) are investigated. Power flows tracing and losses allocation at each generator (or load) must be carried out simultaneously; therefore, a suitable order is required for the analysis of nodes and lines in a network. A procedure for the direct evaluation of all the components of the power flows and of the losses in the lines assigned to the…
TCSC allocation based on line flow based equations via mixed-integer programming
2007
Summary form only given. Research effort has been given to locate the optimal locations of thyristor-controlled series capacitor (TCSC) and their initial compensation levels using mixed-integer programming (MIP). As a useful technique for combinatorial optimisation over integer and continuous variables, the MIP approach can provide robust performance as well as high computational efficiency while solving complex optimal problems. Previous work using MIP employed DC load flow model ignoring reactive power balance, power loss and transformer tap ratios. In this paper, a new planning method is developed based on recently reported line flow equations and basic linearisation of binary-continuous…
Some improvements in solving radial distributions networks through the backward/forward method
2005
In the electrical radial distribution networks analysis, the backward/forward method shows good features in terms of robustness, independence from load nature, small use of hardware resources and limited calculation time. In the present paper, some procedures to improve the b/f method with the aim of reducing the calculation time are presented. The adopted procedures regard the choice of the initial values of the nodes voltages and the way in which the convergence criterion is applied. The results of some tests carried out on some electrical test systems here reported have shown the efficiency of the proposed methodology in terms of calculation time reduction, especially when solving heavil…
Robust estimation of partial directed coherence by the vector optimal parameter search algorithm
2009
We propose a method for the accurate estimation of Partial Directed Coherence (PDC) from multichannel time series. The method is based on multivariate vector autoregressive (MVAR) model identification performed through the recently proposed Vector Optimal Parameter Search (VOPS) algorithm. Using Monte Carlo simulations generated by different MVAR models, the proposed VOPS algorithm is compared with the traditional Vector Least Squares (VLS) identification method. We show that the VOPS provides more accurate PDC estimates than the VLS (either overall and single-arc errors) in presence of interactions with long delays and missing terms, and for noisy multichannel time series. ©2009 IEEE.
Measurement Uncertainty of Harmonic Emission Indicators based on IEEE Std. 1459-2010
2020
The study presented in this paper is aimed at analyzing the measurement uncertainty impact on the evaluation of some power ratio parameters for harmonic emissions assessment based on IEEE Std. 1459-2010 apparent power decomposition. In addition to power factors for line utilization and harmonic pollution levels evaluation defined in the Standard, the study covers also some new parameters, which have been introduced by the authors as IEEE Std. 1459-2010 power quantities ratios. The measurement of the aforesaid parameters is implemented on a PC-based wattmeter, in order to investigate the measurement uncertainty impact on the evaluation of the power ratios. The obtained results show that, in …
The Blockchain in Microgrids for Transacting Energy and Attributing Losses
2017
In recent years novel models for energy distribu- tion appeared and islanded microgrids quest for new ways to exchange energy between consumers and producers without the need of central authorities. The blockchain mechanism has emerged as a distributed solution for recording energy transactions in power systems. The blockchain has been used to permit users bartering and selling energy and to keep track of such exchanges without exposing them to tampering. In this work, we consider a novel application of the blockchain in islanded microgrids that includes also annotating energy losses caused by energy transactions, in order to have a more realistic matching between the physical status of the…
Assessing Frequency Domain Causality in Cardiovascular Time Series with Instantaneous Interactions
2009
Summary Background: The partial directed coherence (PDC) is commonly used to assess in the frequency domain the existence of causal relations between two time series measured in conjunction with a set of other time series. Although the multivariate autoregressive (MVAR) model traditionally used for PDC computation accounts only for lagged effects, instantaneous effects cannot be neglected in the analysis of cardiovascular time series. Objectives: We propose the utilization of an extended MVAR model for PDC computation, in order to improve the evaluation of frequency domain causality in the presence of zero-lag correlations among multivariate time series. Methods: A procedure for the identif…