Browsing by Keyword "Voltage control"
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Item Circulating current control for modular multilevel converter based on selective harmonic elimination with ultra-low switching frequency(Institute of Electrical and Electronics Engineers Inc., 2016-10-25) Perez-Basante, Angel; Ceballos, Salvador; Konstantinou, Georgios; Liserre, Marco; Pou, Josep; De Alegria, Inigo Martinez; POWER ELECTRONICS AND SYSTEM EQUIPMENTMultilevel converters (MCs) are utilized in medium voltage (MV) high power applications due to its higher efficiency than two level converters. On the other hand, modular multilevel converters (MMCs) provide several advantages with regard to other MCs, such as higher scalability, reliability and no requirement of a common DC capacitor. Particularly, low switching frequency modulations, such as (2N+1) selective harmonic elimination (SHE) - pulse width modulation (PWM), may improve the efficiency of MMCs when they are utilized in MV and high power applications, where the number of sub-modules is not high. This work presents a new circulating current control for MMC when (2N+1) SHE-PWM is utilized. Therefore, it is possible to operate the converter simultaneously with low switching frequency and low capacitor voltage ripple at every sub-module besides a correct energy balance between arms. In addition, a new method to implement (2N+1) SHE-PWM for MMCs, which is also valid to implement standard SHE-PWM for any MC, is provided. Using this method, different equation systems are not required for every switching pattern. In this way, this technique provides simultaneously both the switching patterns and the firing angles which solve the SHE problem, simplifying the searching task. Simulation results which have been obtained from a MMC with 5 sub-modules at every arm, have validated the novel proposed circulating current control. Furthermore, the spectrum of the simulated line to line voltage waveform has proved the correct performance of the proposed (2N+1) SHE-PWM implementation method. Several sets of angles have been provided throughout the ma range, where 17 harmonics have been controlled.Item Connection requirements for wind farms: A survey on technical requierements and regulation(2007-10) de Alegría, Iñigo Martinez; Andreu, Jon; Martín, José Luis; Ibañez, Pedro; Villate, José Luis; Camblong, Haritza; SG; GENERALThe increase of the wind power penetration in the electrical grids of Denmark, Germany, Spain and other countries and regions is challenging the stability of the system. The subject of this paper is to review the main problems of the connection of wind farms to the grid and how the grid codes must be adapted in order to integrate wind power generation capacity without affecting the quality and stability of the grid. This paper also summarizes the grid codes that have already been modified to incorporate high levels of wind power.Item Control Room Requirements for Voltage Control in Future Power Systems(2018) Coelho, António; Soares, Filipe; Merino, Julia; Riaño, Sandra; Peças Lopes, João; Tecnalia Research & Innovation; SISTEMAS FOTOVOLTAICOSIn future power grids, a large integration of renewable energy sources is foreseen, which will impose serious technical challenges to system operators. To mitigate some of the problems that renewable energy sources may bring, new voltage and frequency control strategies must be developed. Given the expected evolution of technologies and information systems, these new strategies will benefit from increasing system observability and resources controllability, enabling a more efficient grid operation. The ELECTRA IRP project addressed the new challenges that future power systems will face and developed new grid management and control functionalities to overcome the identified problems. This work, implemented in the framework of ELECTRA, presents an innovative functionality for the control room of the cell operator and its application in assistance with the voltage control designed for the Web-of-Cells. The voltage control method developed uses a proactive mode to calculate the set-points to be sent to the flexible resources, each minute, for a following 15-min period. This way, the voltage control method developed is able to mitigate voltage problems that may occur, while, at the same time, contributes to reduce the energy losses. To enable a straightforward utilization of this functionality, a user interface was created for system operators so they can observe the network state and control resources in a forthright manner accordingly.Item Digital control of a three-phase four-leg inverter under unbalanced voltage conditions(2007) Vechiu, I.; Curea, O.; Camblong, H.; Ceballos, S.; Villate, J. L.; POWER ELECTRONICS AND SYSTEM EQUIPMENT; GENERALIn this paper, the implementation of an innovative inverter control strategy based on the symmetrical components is presented. Symmetrical components of the inverter output voltage and current are decomposed into dq DC quantities to control a three-phase four-leg inverter. This kind of inverter can be a good choice for the applications with hybrid power system based on renewable energy used to supply unbalanced loads. The addition of a fourth leg provides an extra degree of freedom, making possible to handle the neutral current caused by the unbalanced load. Simulation results are compared with experimental results for a prototype inverter to verify the validity of the proposed control strategy.Item Electra IRP voltage control strategy for enhancing power system stability in future grid architectures(2017-10-01) Merino, Julia; Rodríguez-Seco, J.E.; García-Villalba, Íñigo; Temiz, Armağan; Caerts, Chris; Schwalbe, Roman; Strasser, Thomas I.; Temiz, Armaǧan; Tecnalia Research & Innovation; POWER SYSTEMSThis study is intended to show the future voltage control strategy designed in the framework of the ELECTRA Integrated Research Programme (IRP) project for the web-of-cells (WoC) concept. This scheme, called post-primary voltage control, aims to keep the node voltages at any time within the bands defined by the regulations and to minimise the power losses in the system by calculating the optimal voltage set-points for the different nodes. The reactive power will mainly be used to restore the voltages but also active power could be delivered in some cells depending on their voltage levels. Different operating modes of the voltage control will be discussed taking both planning and the real-time operation phases into account. The application of the voltage control strategy to one test grid considered as representative of the WoC structure will also be shown in this study.Item Elimination of Low-Frequency Ripples and Regulation of Neutral-Point Voltage in Stacked Multicell Converters(2017-01) Ghias, Amer M.Y.M.; Pou, Josep; Acuna, Pablo; Ceballos, Salvador; Heidari, Alireza; Agelidis, Vassilios G.; Merabet, Adel; POWER ELECTRONICS AND SYSTEM EQUIPMENTThis paper introduces a modulation method for the stacked multicell converters (SMCs). The proposed method is implemented using phase-disposition pulse width modulation and is capable of balancing and regulating the voltages of all the capacitors in the topology, i.e., the flying capacitors and the dc-link capacitors. The proposed method is also able to eliminate the low-frequency voltage ripples that may appear in the neutral point (NP) of SMCs. In SMCs with two stacks, the NP voltage level can be generated by direct connection of the output to the dc-link NP, but also using two extra states available. This redundancy is used to regulate the NP voltage. Furthermore, since the proposed method can eliminate the low-frequency voltage ripples in the capacitors, the capacitances of all the capacitors of the SMCs can be reduced, while maintaining high quality of the output voltages and currents. This enables the use of film capacitors. Simulation and experimental results are presented from a three-phase five-level 2× 2 SMC to verify the effectiveness of the proposed method.Item Integration of der into power system operation through Virtual Power Plant concept applied for voltage regulation(2009) Oyarzabal, José; Martí, Juan; Ilo, Albana; Sebastian, María; Alvira, David; Johansen, Knud; POWER SYSTEMSThis paper reports on the solution adopted at the Southern Scenario demonstrator of the R&D project FENIX for the effective integration of distributed energy resources (DER) into power system operation. DER reactive power production, on load tap changers (OLTC) and shunt capacitors are optimally coordinated to alleviate/eliminate distribution network constraints. This general objective is defined within an optimal power flow (OPF) algorithm targeting other goals such as network losses reduction or influencing transmission network node' voltages. A commercial distribution management system (DMS) is adapted to integrate the voltage VAr control (VVC) module and the whole system is brought into operation with real time measurements and commands send on open loop basis.Item Low-frequency voltage ripples in the flying capacitors of the nested neutral-point-clamped converter(Institute of Electrical and Electronics Engineers Inc., 2016-05-10) Ghias, Amer M.Y.M.; Pou, Josep; Ceballos, Salvador; Agelidis, Vassilios G.; POWER ELECTRONICS AND SYSTEM EQUIPMENTThe flying capacitors (FCs) of the nested neutral-point-clamped (NNPC) converter show an inherent voltage ripple at fundamental frequency. This ripple can be significantly large under some operating conditions of the converter. In this paper, the amplitudes of the low-frequency voltage ripples in the FCs are determined. An averaged model of the NNPC converter is introduced and used in the analysis. The amplitudes of the capacitor voltage ripples are provided using normalized variables so that this information can be used to size the FCs of the converter in different applications. The results of the analysis are validated experimentally in a laboratory prototype.Item Technologies and Protocols: The Experience of the Three SmartNet Pilots: The experience of the three smartnet pilots(Springer, 2019-10-25) Madina, Carlos; Jimeno, Joseba; Ortolano, Luca; Palleschi, Margherita; Ebrahimy, Razgar; Madsen, Henrik; Pardo, Miguel; Corchero, Cristina; POWER SYSTEMSThe deployment of technological pilots is of paramount importance for testing and demonstrating the technical feasibility of the concepts described in this book for two main reasons. On the one hand, there are few real-life experiences in the application of these concepts, as TSO-DSO coordination is a relatively new topic. On the other hand, there may be some implementation difficulties which cannot be anticipated by the scenario analysis and CBA. Whenever possible, more than one pilot should be deployed, so that each of them can focus on different parts of the TSO-DSO coordination value chain. In that sense, it is important to demonstrate different potential TSO-DSO coordination schemes, so that issues arising from each of them can be identified. Moreover, it is also important to demonstrate different types of DER, so that their flexibilities can be better assessed and the advantages and disadvantages for real-life implementation can be properly identified and addressed. As a third complementarity aspect, having different technological pilots allows for focusing on different parts of the value chain, so that one of them may take the vision of the TSO or DSO, while another one can focus on the needs of the aggregator or DER owners.