This paper presents the implementation of a Solid State Transformer (SST) model in OpenDSS. The goal is to develop a SST model that could be useful for assessing the impact that the replacement of the conventional iron-and-copper transformer with the SST can have on the distribution system performance. Test distribution systems of different characteristics and size have been simulated during different time periods. The simulations have been carried out assuming voltage-dependent loads and considering that power flow through either the HV/MV substation transformer or any of the MV/LV distribution transformers can be bidirectional. Simulation results prove that a positive impact should be expected on voltages at both MV and LV levels, but the efficiency of current SST designs should be improved.
Bogarra, S.; Riba, J.; Sala, V.; Garcia, A. International journal of electrical power and energy systems Vol. 87, p. 16-26 DOI: 10.1016/j.ijepes.2016.11.006 Data de publicació: 2017-05-01 Article en revista
Due to the widespread use of electronic power converters, low-voltage high-frequency cable models are being increasingly applied in industry, automobile or aeronautics applications among others. It is known that depending on switching frequency, cable configuration and length, transient overvoltage effects comprising a wide frequency range from dc up to several tens of MHz can appear. However, to accurately reproduce the wide-band frequency response, such models often require the use of ladder networks, thus being necessary to adjust the values of a relatively large number of R, L and C components, which is a complex task. This paper is focused to solve this problem, which is done by applying an iterative genetic algorithm (IGA) optimization approach. From a set of experimental short circuit and open circuit tests the high-frequency cable model of a given cable configuration is obtained, whose parameters are fitted by means of the proposed IGA-based method. Finally, the accuracy of the model obtained is validated experimentally by comparing the frequency-domain and time-domain responses through overvoltage predictions of different samples of the analyzed cable.
Rakhshani, E.; Remon, D.; Rodriguez, P. International journal of electrical power and energy systems Vol. 81, p. 140-152 DOI: 10.1016/j.ijepes.2016.02.011 Data de publicació: 2016-10-01 Article en revista
Recent advancements in power electronics have made HVDC links and renewable based generation more popular in power systems application with better grid support functionalities like frequency control and inertia emulation tasks. Conventional operation and control strategies" are undergoing of different changes and all the infrastructure of future modern power system should efficiently support the delivery of ancillary services in complex scenarios of AC/DC multi-area interconnected system. The AGC system of tomorrow must be able to handle complex interactions between control areas with HVDC links and distributed generation equipment. In such scenario, the effects of wide-area interconnections, PLL (Phase Locked Loop) and frequency measurements cannot be ignored. The dynamics effects of PLL and frequency measurements are very important for HVDC operation. For obtaining an acceptable performance of AC/DC system, the dynamic models of PLL and measurements need to be taken into account. This paper focused on the effects of PLL and frequency measurements in frequency supports of HVDC interconnected system. A novel approach for analyzing the dynamic effects of HVDC links considering PLL effects during coordination with AC system is presented and discussed. The effects of PLL are considered by introducing a second-order function. A Pade approximation method is also introduced for adding the effects of communication delays on AGC operation and the state space models are presented. The proposed model is analyzed for different multi-area test systems which contains parallel AC/DC transmission links. (C) 2016 Elsevier Ltd. All rights reserved.
Marzband, M.; Yousefnejad, E.; Sumper, A.; Dominguez, J. International journal of electrical power and energy systems Vol. 75, p. 265-274 DOI: 10.1016/j.ijepes.2015.09.010 Data de publicació: 2016-02-01 Article en revista
In this paper, an algorithm for energy management system (EMS) based on multi-layer ant colony optimization (EMS-MACO) is presented to find energy scheduling in Microgrid (MG). The aim of study is to figure out the optimum operation of micro-sources for decreasing the electricity production cost by hourly day-ahead and real time scheduling. The proposed algorithm is based on ant colony optimization (ACO) method and is able to analyze the technical and economic time dependent constraints. This algorithm attempts to meet the required load demand with minimum energy cost in a local energy market (LEM) structure. Performance of MACO is compared with modified conventional EMS (MCEMS) and particle swarm optimization (PSO) based EMS. Analysis of obtained results demonstrates that the system performance is improved also the energy cost is reduced about 20% and 5% by applying MACO in comparison with MCEMS and PSO, respectively. Furthermore, the plug and play capability in real time applications is investigated by using different scenarios and the system adequate performance is validated experimentally too. (C) 2015 Elsevier Ltd. All rights reserved.
Díaz, F.; Hau, M.; Sumper, A.; Gomis-Bellmunt, O. International journal of electrical power and energy systems Vol. 68, p. 313-326 DOI: 10.1016/j.ijepes.2014.12.062 Data de publicació: 2015-06-01 Article en revista
This work assesses the participation of wind power plants in primary frequency control support. To participate in frequency control-related tasks, the wind power plants have to maintain a certain level of power reserves. In this article, the wind power plant is equipped with a flywheel-based storage system to fulfil the power reserve requirements set by the network operator. The article focuses on two main aspects: the definition of the control strategy to derate the wind turbines to provide a part of the required power reserves; and the coordinated regulation of the power reserves of the wind turbines and the flywheels while participating in primary frequency control. This coordinated regulation enables the wind power plant to maintain the net level of power reserves set by the network operator while alleviating the need of deloading the wind turbines. The performance of the proposed control schemes are shown by simulation. (C) 2015 Elsevier Ltd. All rights reserved.
This paper studies the effects of voltage sags caused by faults on doubly-fed induction generators to overcome grid faults. A wide range of sag duration and depth values is considered. It is observed that sag duration influence is periodical. Sag effects depend on duration and depth and on the fault-clearing process as well. Two approaches of the model are compared: the most accurate approach, discrete sag, considers that the fault is cleared in the successive natural fault-current zeros of affected phases, leading to a voltage recovery in several steps; the least accurate approach, abrupt sag, considers that the fault is cleared instantaneously in all affected phases, leading to a one-step voltage recovery. Comparison between both sag models reveals that the fault-clearing process smoothes sag effects. The study assumes that the rotor-side converter can keep constant the transformed rotor current in the synchronous reference frame, thus providing insights into wind turbine fault ride-through capability. The voltage limit of the rotor-side converter is considered to show the situations where the rotor current can be controlled. Finally, a table and a 3D figure summarizing the effects of the most severe grid faults on the rotor-side converter to overcome the most severe faults are provided. (C) 2014 Elsevier Ltd. All rights reserved.
Egea, A.; Junyent-Ferré, A.; Bergas, J.; Bianchi, F.; Gomis-Bellmunt, O. International journal of electrical power and energy systems Vol. 61, p. 523-530 DOI: 10.1016/j.ijepes.2014.03.069 Data de publicació: 2014-10-01 Article en revista
A control scheme for Squirrel Cage Induction Generator (SCIG) based wind turbine cluster (or entire wind farm) connected by means of a single high voltage direct current-Voltage Source Converter (VSC-HVDC) is presented. The proposed scheme extends the SCIG vector control of a single wind turbine with a full power converter to a whole wind turbine cluster with a single power converter calculating and regulating the optimal wind turbine cluster electrical frequency. This concept can be used in wind farms composed of multiple clusters of multiple wind turbines, and for entire offshore wind farms connected to the main grid using a HVDC point-to-point connection or a multiterminal HVDC grid. (C) 2014 Elsevier Ltd. All rights reserved.
Dominguez, J.; Ugalde , C.; Bianchi, F.; Gomis-Bellmunt, O. International journal of electrical power and energy systems Vol. 58, p. 75-84 DOI: 10.1016/j.ijepes.2014.01.001 Data de publicació: 2014-06-01 Article en revista
During the last years wind power has emerged as one of the most important sources in the power generation share. Due to stringent Grid Code requirements, wind power plants (WPPs) should provide ancillary services such as fault ride-through and damping of power system oscillations to resemble conventional generation. Through an adequate selection of input-output signal pairs, WPPs can be effectively used to provide electromechanical oscillations damping. In this paper, different analysis techniques considering both controllability and observability measures and input-output interactions are compared and critically examined. Recommendations are drawn to select the best signal pairs available from WPPs to contribute to power oscillations damping. Control system design approaches including single-input single-output and multivariable control are considered. The recommendation of analysis techniques is justified through the tools usage in a test system including a WPP. (C) 2014 The Authors. Published by Elsevier Ltd. All rights reserved.
Muñoz-Aguilar, R. S.; Rodriguez, P.; Doria-Cerezo, A.; Candela, J.; Luna, A. International journal of electrical power and energy systems Vol. 60, p. 275-282 DOI: 10.1016/j.ijepes.2014.03.003 Data de publicació: 2014-04-01 Article en revista
This paper presents a sliding mode control for a wound rotor synchronous machine acting as an isolated generator connected to an unbalanced load. In order to simplify the control methodology, the standard dq-model of the machine is connected to a balanced resistive load. A switching function is defined in order to fulfill the control objective. From the desired surface, the standard sliding methodology is applied to obtain a robust and very simple controller. Then, the actual measured voltage of the machines is acquired and treated trough a frequency locked loop algorithm in order to extract the positive sequence and control it to guarantee a good definition of the park transformation. A phase locked loop algorithm is also used to avoid speed sensors. Numerical simulations and experimental results validate the control law and show good performance and a fast response to load and reference changes
de Prada, M.; Mancilla, F.; Dominguez, J.; Muljadi, E.; Singh, M.; Gomis-Bellmunt, O.; Sumper, A. International journal of electrical power and energy systems Vol. 55, p. 714-722 DOI: 10.1016/j.ijepes.2013.10.025 Data de publicació: 2014-02 Article en revista
Girbau, F.; Sumper, A.; Díaz, F.; Galceran-Arellano, S. International journal of electrical power and energy systems Vol. 55, p. 285-296 DOI: 10.1016/j.ijepes.2013.09.016 Data de publicació: 2014-02 Article en revista
Muñoz-Aguilar, R. S.; Doria-Cerezo, A.; Puleston, P. International journal of electrical power and energy systems Vol. 47, p. 264-279 DOI: 10.1016/j.ijepes.2012.11.012 Data de publicació: 2013-05-01 Article en revista
This paper presents a proposal for a series hybrid electric vehicle propulsion system. This new configuration is based on a wound-rotor synchronous generator (WRSM) and a doubly-fed induction machine (DFIM). The energy-based model of the whole system is obtained taking advantage of the capabilities of the port-based modeling techniques. From the dq port-controlled Hamiltonian description of the WRSM and DFIM, the Hamiltonian model of the proposed Direct Synchronous-Asynchronous Conversion System (DiSAC) is developed. Subsequently, the bond graph models of the DiSAC and associate systems are also provided. Numerical simulations are also presented in order to validate the proposed system.
This paper presents a proposal for a series hybrid electric vehicle propulsion system. This new configuration is based on a wound-rotor synchronous generator (WRSM) and a doubly-fed induction machine (DFIM). The energy-based model of the whole system is obtained taking advantage of the capabilities of the port-based modeling techniques. From the dq port-controlled Hamiltonian description of the WRSM and DFIM, the Hamiltonian model of the proposed Direct Synchronous-Asynchronous Conversion System (DiSAC) is developed. Subsequently, the bond graph models of the DiSAC and associate systems are also provided. Numerical simulations are also presented in order to validate the proposed system
López-García, I.; Espinosa-Pérez, G.; Siguerdidjane, H.; Doria-Cerezo, A. International journal of electrical power and energy systems Vol. 45, num. 1, p. 303-312 DOI: 10.1016/j.ijepes.2012.08.067 Data de publicació: 2013-02-01 Article en revista
In this paper the stator-side power regulation control problem of DFIM is approached. It is shown how a
passivity-based controller can deal with this problem establishing a viable solution from both a dynamic
performance perspective and a practical implementation point of view. The evaluation of the presented
scheme is carried out by considering typical operation conditions, namely: active power generation with
demanded or delivered reactive power. Special interest is given to the rigorous establishment of the stability
properties of the closed-loop system, which allows for achieving remarkable dynamic responses, in
terms of convergence rates as well as the region of attraction of the equilibrium point defined by a given
operation regime. From a practical viewpoint, the usefulness of the scheme is concluded by realizing that
the requirements imposed concerning the structural features of both the generator by itself and the
power converter required for its operation, can be fulfilled by commercially available off-the-shelf
Arias, A.; Ortega, C.; Zaragoza, J.; Espina, J.; Pou, J. International journal of electrical power and energy systems Vol. 45, num. 1, p. 78-86 DOI: 10.1016/j.ijepes.2012.08.073 Data de publicació: 2013-02 Article en revista
Permanent Magnet Synchronous Machines (PMSMs) have several advantages, such as high ef¿ciency and
low volume and weight, which make them attractive for aerospace applications and high performance
Matrix Converters (MCs) are an all-silicon alternative, with no bulky reactive elements, to the standard
voltage source inverter.
The most common control technique for such PMSM MC-fed drives is the so-called Field-Oriented Control (FOC), which requires the permanent magnet ¿ux position to achieve high dynamic performance.
Encoders or resolvers are the most common sensing devices used for such a purpose, which not only
increases the total cost of the PMSM drive but also adds extra electronics and cabling that may cause failures. This paper investigates and proposes an all range (from zero to full) speed hybrid sensorless FOC.
The novelty of this paper relies on the use of a hybrid sensorless four quadrant FOC that averages the
needed angle estimation from a model based angle estimator and a voltage pulse test injection angle estimator when feeding the PMSM with an MC instead of a standard voltage source inverter. Speed reversal
and load impact simulation results are included, fully supporting the claims made in this paper
Liang, J.; Gomis-Bellmunt, O.; Ekanayake, J.; Jenkins, N.; An, W. International journal of electrical power and energy systems Vol. 43, num. 1, p. 54-62 DOI: 10.1016/j.ijepes.2012.04.063 Data de publicació: 2012-12 Article en revista
The improvements obtained on the torque with low currents using rotor with spiral sheets are analyzed
in this paper. To have a complete study, several rotors and stators have been built to verify the electromagnetic
variations on the three-phase asynchronous motors where they combine different constructive
and mechanical characteristics of the related elements: changing inertias, constructive materials, and the
geometrical shapes and disposition of the sheets. These different types of motors have been first tested in
the laboratory, then, are simulated using computer aided tools (Matlab–Simulink). In particular four stators
(1000, 1500, 1500-type A, and 3000 rpm) having the same constructive parameters, have been tested
with the following rotors: solid rotor, solid rotor with diamagnetic rings, drag cup, and simple and double
squirrel cage rotor. All these results have been compared to those obtained with the seven variants of
spiral sheet rotor, presented in this paper.
Power grids are prone to failure. Time series of reliability measures such as total power loss or energy not supplied can give significant account of the underlying dynamical behavior of these systems, specially when the resulting probability distributions present remarkable features such as an algebraic tail, usually considered the footprint of self-organization and the existence of critical points. In this paper, 7 years (from 2002 to 2008) of Europe’s transport of electricity network failure events have been analyzed and the best fit for this empirical data probability distribution is presented. With the actual span of available data and although there exists a moderate support for the power-law model, the relatively small amount of events contained in the function’s tail suggests that causal factors other than self-organization or a critical state might be significantly ruling these systems’ dynamics.