Academic literature on the topic 'Hvdc; mtdc'
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Journal articles on the topic "Hvdc; mtdc":
1
Rios, Mario A., and Fredy A. Acero. "Planning multi-terminal direct current grids based graphs theory." International Journal of Electrical and Computer Engineering (IJECE) 11, no. 1 (February 1, 2021): 37. http://dx.doi.org/10.11591/ijece.v11i1.pp37-46.
Abstract:
Transmission expansion planning in AC power systems is well known and employs a variety of optimization techniques and methodologies that have been used in recent years. By contrast, the planning of HVDC systems is a new matter for the interconnection of large power systems, and the interconnection of renewable sources in power systems. Although the HVDC systems has evolved, the first implementations were made considering only the needs of transmission of large quantities of power to be connected to the bulk AC power system. However, for the future development of HVDC systems, meshed or not, each AC system must be flexible to allow the expansion of these for future conditions. Hence, a first step for planning HVDC grids is the planning and development of multi-terminal direct current (MTDC) systems which will be later transformed in a meshed system. This paper presented a methodology that use graph theory for planning MTDC grids and for the selection of connection buses of the MTDC to an existing HVAC transmission system. The proposed methodology was applied to the Colombian case, where the obtained results permit to migrate the system from a single HVDC line to a MTDC grid.
2
Oni, Oluwafemi Emmanuel, Andrew G. Swanson, and Rudiren Pillay Carpanen. "Impact of LCC–HVDC multiterminal on generator rotor angle stability." International Journal of Electrical and Computer Engineering (IJECE) 10, no. 1 (February 1, 2020): 22. http://dx.doi.org/10.11591/ijece.v10i1.pp22-34.
Abstract:
<span>Multiterminal High Voltage Direct Current (HVDC) transmission utilizing Line Commutated Converter (LCC-HVDC) technology is on the increase in interconnecting a remote generating station to any urban centre via long distance DC lines. This Multiterminal-HVDC (MTDC) system offers a reduced right of way benefits, reduction in transmission losses, as well as robust power controllability with enhanced stability margin. However, utilizing the MTDC system in an AC network bring about a new area of associated fault analysis as well as the effect on the entire AC system during a transient fault condition. This paper analyses the fault current contribution of an MTDC system during transient fault to the rotor angle of a synchronous generator. The results show a high rotor angle swing during a transient fault and the effectiveness of fast power system stabilizer connected to the generator automatic voltage regulator in damping the system oscillations. The MTDC link improved the system performance by providing an alternative path of power transfer and quick system recovery during transient fault thus increasing the rate at which the system oscillations were damped out. This shows great improvement compared to when power was being transmitted via AC lines.</span>
3
Jiahui, Wu, Wang Haiyun, Wang Weiqing, and Zhang Qiang. "Three-terminal Hybrid HVDC Transmissions Control Strategies for Bundled Wind-thermal Power Plants." Open Electrical & Electronic Engineering Journal 10, no. 1 (December 30, 2016): 156–65. http://dx.doi.org/10.2174/1874129001610010156.
Abstract:
This paper evaluates application feasibility of a Hybrid Multi-terminal HVDC system and wind-thermal-bundled plants simulated in DIgSLIENT PowerFactory environment. The proposed hybrid MTDC system consists of two line-communicated converters (LCC), which are connected to both wind farms and thermal power plants, and one voltage source converter (VSC) at the grid side. Control strategies for each converter are designed to handle this system under different disturbance conditions. Simulation results show that the wind power fluctuation can be compensated by the thermal-generated power. Results demonstrate the effectiveness of the proposed control strategies of the hybrid MTDC system compared to a conventional MTDC system. The proposed scheme combines advantages of both LCC and VSC HVDC systems and provides a new way to transmit wind power over long distances to the main grid.
4
Xu, Han Ping, Xia Chen, Wang Xiang, and Jin Yu Wen. "Control and Operational Characteristics Research on Multi-Terminal HVDC for Wind Power Transmission." Advanced Materials Research 1092-1093 (March 2015): 248–53. http://dx.doi.org/10.4028/www.scientific.net/amr.1092-1093.248.
Abstract:
This paper proposed the line-commutated converter based multi-terminal HVDC (LCC-MTDC) combining with the static synchronous compensator (STATCOM) for doubly-fed induction generator (DFIG) based wind farms integration with bulk wind power transmission over long distance. This paper is aimed at the control strategy design and the operational characteristics research of LCC-MTDC for wind power transmission. Then, the control methodologies of the complex integration system are addressed from two aspects: the MTDC and the wind farm. The coordination control strategy is developed to ensure the stable operation of the MTDC system and the wind farm controller is designed to capture the maximum wind power and ensure all the wind power transferred into the MTDC. Simulation results in PSCAD/EMTDC show that LCC-MTDC could achieve desirable operational performances with the control strategy proposed.
5
Hwang, Sungchul, Sungyoon Song, Gilsoo Jang, and Minhan Yoon. "An Operation Strategy of the Hybrid Multi-Terminal HVDC for Contingency." Energies 12, no. 11 (May 28, 2019): 2042. http://dx.doi.org/10.3390/en12112042.
Abstract:
The application of the direct current (DC) transmission is increasing through the interconnection between grids or the renewable energy resource integration. Various types of DC transmission topology are researched, and the hybrid multi-terminal high voltage DC (HVDC), called the “MTDC”, is one of the research subjects. The hybrid multi-terminal HVDC is the MTDC system that is composed with the Line Commutated Converter (LCC) and Voltage Source Converter (VSC). Most hybrid MTDC research has been focused on the connection of the renewable energy generation sources, especially offshore wind farms. However, the DC grid built with a hybrid MTDC was recently proposed due to the development of the converter technology. Therefore, the DC grid is expected to be able to substitute some parts of the transmission grid instead of the alternating current (AC) system, and the operation strategies of the DC grid are still being researched. The DC grid has the advantage of being able to control the power flow, which can even improve the stability of the connected AC system. The dynamic model is required to analyze the improvement of the AC system by the operation strategy of the hybrid MTDC, however, there is no generic model for the system. In this paper, an operation strategy of the hybrid MTDC is proposed to improve the stability of the AC power system by increasing the utilization of parallel AC transmission lines under the contingency condition. Furthermore, studies on the modeling method for a hybrid MTDC analysis were performed. The proposed modeling method and operation strategy were verified in simulations for which a modified IEEE 39 bus test system was used. The improvement of transient stability by the proposed hybrid MTDC system was shown in the simulation results.
6
Qin, Boyu, Wansong Liu, Ruowei Zhang, Jialing Liu, and Hengyi Li. "Review on Short-circuit Current Analysis and Suppression Techniques for MMC-HVDC Transmission Systems." Applied Sciences 10, no. 19 (September 27, 2020): 6769. http://dx.doi.org/10.3390/app10196769.
Abstract:
The modular multilevel converter (MMC) has been widely adopted in high voltage direct current (HVDC) transmission systems due to its significant advantages. MMC-HVDC is developing towards multi-terminal direct current (MTDC) power grid for reliability enhancement. However, there exist a huge amplitude and a steep rise in fault current due to the low impedances of DC lines and MMCs, which threaten the security and reliability of the DC power grids. It is necessary to restrain the DC short circuit current in order to ensure the safe and stable operation of DC power grids. This paper gives a comprehensive review and evaluation of the proposed DC short-circuit current analysis and suppression techniques used in MMC-based MTDC power girds, in terms of MMC modeling, short circuit calculation, and suppression method. In addition, future trends of countermeasures to short circuit current in MMC-based MTDC power grids are also discussed.
7
Lee, Chun-Kwon, Gyu-Sub Lee, and Seung-Jin Chang. "Solution to Fault of Multi-Terminal DC Transmission Systems Based on High Temperature Superconducting DC Cables." Energies 14, no. 5 (February 26, 2021): 1292. http://dx.doi.org/10.3390/en14051292.
Abstract:
In this paper, we developed the small-signal state-space (SS) model of hybrid multi-terminal high-voltage direct-current (HVDC) systems and fault localization method in a failure situation. The multi-terminal HVDC (MTDC) system is composed of two wind farm side voltage-source converters (VSCs) and two grid side line-commutated converters (LCCs). To utilize relative advantages of the conventional line-commutated converter (LCC) and the voltage source converter (VSC) technologies, hybrid multi-terminal high-voltage direct-current (MTDC) technologies have been highlighted in recent years. For the models, grid side LCCs adopt distinct two control methods: master–slave control mode and voltage droop control mode. By utilizing root-locus analysis of the SS models for the hybrid MTDC system, we compare stability and responses of the target system according to control method. Furthermore, the proposed SS models are utilized in time-domain simulation to illustrate difference between master–slave control method and voltage droop control method. However, basic modeling method for hybrid MTDC system considering superconducting DC cables has not been proposed. In addition, when a failure occurs in MTDC system, conventional fault localization method cannot detect the fault location because the MTDC system is a complex form including a branch point. For coping with a failure situation, we propose a fault localization method for MTDC system including branch points. We model the MTDC system based on the actual experimental results and simulate a variety of failure scenarios. We propose the fault localization topology on a branch cable system using reflectometry method. Through the simulation results, we verify the performance of fault localization. In conclusion, guidelines to select control method in implementing hybrid MTDC systems for integrating offshore wind farms and to cope with failure method are provided in this paper.
8
Ge, Le, Limin Lu, Xiaodong Yuan, and Yongzhou Yu. "Optimal Operation Strategy of Flexible Interconnected Distribution Network Based on SES-VSC-MTDC." Mathematical Problems in Engineering 2020 (August 24, 2020): 1–14. http://dx.doi.org/10.1155/2020/9732378.
Abstract:
The increasing integration of renewable energy is challenging the secure operation of the power system. System flexibility or the capability to address the significant power fluctuations from renewable energy is becoming more and more relevant. Self-energy storage-based multiterminal back-to-back VSC-HVDC (SES-VSC-MTDC) technology is first proposed, and it can realize the power regulation on both temporal and spatial dimensions, which helps improve the power supply reliability and the capacity to accommodate renewable energy of the interconnected distribution networks. Then, to address the coordination control problem of the energy storage and back-to-back VSC-HVDC, a comprehensive control strategy of SES-VSC-MTDC is proposed based on the optimal power flow preprocessing and state of charge interval division. Then, the power regulation model and the energy-power regulation timing model of SES-VSC-MTDC are established for different control strategies. Then, we use the primal-dual interior-point method to solve the developed optimal operation model of flexible interconnected distribution network. Finally, a 33-bus system with four interconnected feeders is used to test the effectiveness of the SES-VSC-MTDC technology and its operation control strategy.
9
Wang, Kai, Hai Shun Sun, Yu Hua, Yuan Liu, Wei Xing Lin, and Cheng Hao Li. "Research on DC Voltage Control Strategies for Typical Four-Terminal HVDC System." Applied Mechanics and Materials 521 (February 2014): 222–28. http://dx.doi.org/10.4028/www.scientific.net/amm.521.222.
Abstract:
The continuous development of alternative energy has put forward higher requirement for electricity transmission. To cope with its fluctuation characteristics, high voltage direct current (HVDC) technology has received more attention. Voltage Source Converter (VSC) based Multi-Terminal High Voltage Direct Current (MTDC) represents the future trend of HVDC technology. This paper mainly focuses on the control strategies of a four-terminal VSC based MTDC power transmission system. The operation characteristic of the system was studied, and the proposed two control strategies, master-slave control strategy and DC voltage droop control strategy, were verified through simulations. The latter control strategy was proved to be performing well under various conditions, including converter station disconnection and faults at AC side of the converter.
10
Li, Zhou, Yan He, Ting-Quan Zhang, and Xiao-Ping Zhang. "Universal Power Flow Algorithm for Bipolar Multi-Terminal VSC-HVDC." Energies 13, no. 5 (February 26, 2020): 1053. http://dx.doi.org/10.3390/en13051053.
Abstract:
An effective and accurate power flow algorithm provides control references for active power dispatch and initial steady state operating points, used for stability analysis, short-circuit calculations, and electromagnetic transient simulations, which is not only a fundamental precondition to analyze the system operating conditions, but also the basis to improve the accuracy of power flow and DC voltage control of the multi-terminal voltage source converter-based high voltage direct current (VSC-HVDC). This paper proposes a nodal voltage-based universal steady-state power flow algorithm for the newly-developed bipolar multi-terminal VSC-HVDC (VSC-MTDC). Firstly, as the positive-pole and negative-pole DC network of the bipolar VSC-MTDC can be operated individually, a bipolar power flow alternating iterative method is proposed here to obtain the positive/negative-pole DC network power flow. Secondly, a series of nodal equivalent methods involving various control strategies are proposed for the universal power flow algorithm. Then the detailed calculation procedure and a general MATLAB(TM) program for the universal power flow algorithm is presented. A typical 4-terminal bipolar VSC-MTDC system was built in the PSCAD/EMTDC to verify the validity of the proposed algorithm, and the results are discussed here. Moreover, the calculation results of more complex bipolar VSC-MTDC systems under different operating conditions, employing the proposed universal power flow algorithm, are presented to illustrate its universality and efficiency.
Dissertations / Theses on the topic "Hvdc; mtdc":
1
Junior, Rui Bertho. "Um novo algoritmo de proteção para redes HVDC multiterminais." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/18/18154/tde-26042018-105556/.
Abstract:
Recentes avanços em relação aos dispositivos semicondutores utilizados no processo de conversão CA/CC levaram à aplicação de conversores fonte de tensão, do inglês Voltage Source Converter (VSC), na transmissão de energia elétrica em altas tensões e corrente contínua, do inglês High Voltage Direct Current (HVDC). Uma das vantagens da utilização de VSCs é simplificr o processo de criação de redes HVDC com múltiplos terminais, identificadas pela sigla em inglês Multi-terminal HVDC (MTDC). Entretanto, a severidade das faltas em linhas CC, aliada à fragilidade dos conversores, exige a utilização de algoritmos capazes de identificar corretamente a ocorrência de faltas em um reduzido intervalo de tempo. Neste sentido, este trabalho tem por objetivo a elaboração de uma nova metodologia de proteção que possa ser aplicada na proteção primária de sistemas HVDC, especialmente para redes MTDC. Para tanto, foi elaborado um modelo detalhado de rede MTDC com três terminais e, a partir dos dados obtidos por meio de extensivas simulações de falta, foram identificadas características dos sinais de corrente na linha CC capazes de auxiliar na proteção da rede. Pela utilização da Transformada wavelet, análise de componentes principais e sistemas Genético-Fuzzy, foi possível a elaboração de um algoritmo de proteção sem comunicação, rápido, confiável e seletivo para utilização em redes MTDC. Adicionalmente, foi realizada a implementação em hardware do algoritmo proposto, evidenciando sua aplicabilidade em sistemas reais. A metodologia proposta foi capaz de garantir seletividade, confiabilidade e velocidade de atuação ao sistema de proteção, identificando corretamente faltas nos condutores CC em menos de 1,5 ms.Recent progress regarding semiconductor devices used in AC/DC conversion led to the use of Voltage Source Converters (VSC) in High Voltage Direct Current (HVDC) power transmission systems. AN advantage of using VSCs it to simplify the creation of Multi-terminal HVDC (MTDC) networks. However, the severity of DC faults, combined with the converters vulnerability, requests the use of algorithms able to correctly identify fault occurrences in a short period of time. Therefore, this work aims to elaborate a new primary protection methodology that could be applied to HVDC systems, especially in MTDC networks. For this purpose, a detailed three terminals MTDC network has been modeled and, through extensive computational faulty simulations, DC current characteristics that are able to assist network protection methods were identified. By means of the wavelet transform, principal component analysis and genetic fuzzy systems, it was possible to develop a fast, reliable an selective non-unit protection for MTDC grids. Moreover, the proposed algorithm was implemented in hardware, emphasizing its applicability in actual systems. The proposed methodology was able to ensure selectivity, reliability and speed of operation, correctly identifying DC faults in less than 1.5 ms.
2
Sheridan, Caitríona Evelyn. "Assessment of HVDC technologies for an offshore MTDC grid." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/38552.
Abstract:
This thesis examines various HVDC converter technologies that could be used in offshore Multi-Terminal DC (MTDC) grids. MTDC grids rely on AC/DC converters to interface with AC systems and also for control services. Two AC/DC topologies were compared, the half-bridge Modular Multi-level Converter (MMC) and the Alternate Arm Converter (AAC). As new DC system voltages emerge the DC/DC converter could be an enabling technology for interconnection and future MTDC networks. As yet there is no consensus on DC/DC converter topology and a critical comparison of several potential designs was conducted. An MMC based DC/DC converter had distinct advantages compared with other designs. Several average value converter models of the converters were developed to allow efficient simulation of MTDC networks, while maintaining a high level of accuracy of the converter characteristics. These models were verified with full switching models for steady state and fault conditions. Two o shore MTDC networks were studied; a four-terminal network, and a MTDC network. The four-terminal network used a normally open point to connect two existing point-to-point links, allowing reconfiguration in the event of a DC fault. The MTDC network uses a DC/DC converter to interconnect a bipole HVDC link with the previously studied four-terminal network. Several simulation studies show how new converters can improve the operation of a MTDC and provide additional capabilities such as DC fault blocking.
3
Akkari, Samy. "Contrôle d'un système multi-terminal HVDC (MTDC) et étude des interactions entre les réseaux AC et le réseau MTDC." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLC069/document.
Abstract:
La multiplication des projets HVDC de par le monde démontre l'engouement toujours croissant pour cette technologie de transport de l'électricité. La grande majorité de ces transmissions HVDC correspondent à des liaisons point-à-point et se basent sur des convertisseurs AC/DC de type LCC ou VSC à 2 ou 3 niveaux. Les travaux de cette thèse se focalisent sur l'étude, le contrôle et la commande de systèmes HVDC de type multi-terminal (MTDC), avec des convertisseurs de type VSC classique ou modulaire multi-niveaux. La première étape consiste à obtenir les modèles moyens du VSC classique et du MMC. La différence fondamentale entre ces deux convertisseurs, à savoir la possibilité pour le MMC de stocker et de contrôler l'énergie des condensateurs des sous-modules, est détaillée et expliquée. Ces modèles et leurs commandes sont ensuite linéarisés et mis sous forme de représentations d'état, puis validés en comparant leur comportement à ceux de modèles de convertisseurs plus détaillés à l'aide de logiciels de type EMT. Une fois validés, les modèles d'état peuvent être utilisés afin de générer le modèle d'état de tout système de transmissions HVDC, qu'il soit point-à-point ou MTDC. La comparaison d'une liaison HVDC à base de VSCs classiques puis de MMCs est alors réalisée. Leurs valeurs propres sont étudiées et comparées, et les modes ayant un impact sur la tension DC sont identifiés et analysés. Cette étude est ensuite étendue à un système MTDC à 5 terminaux, et son analyse modale permet à la fois d'étudier la stabilité du système, mais aussi de comprendre l'origine de ses valeurs propres ainsi que leur impact sur la dynamique du système. La méthode de décomposition en valeurs singulières permet ensuite d'obtenir un intervalle de valeurs possibles pour le paramètre de"voltage droop", permettant ainsi le contrôle du système MTDC tout en s'assurant qu'il soit conforme à des contraintes bien définies, comme l'écart maximal admissible en tension DC. Enfin, une proposition de "frequency droop" (ou "statisme"), permettant aux convertisseurs de participer au réglage de la fréquence des réseaux AC auxquels ils sont connectés, est étudiée. Le frequency droop est utilisé conjointement avec le voltage droop afn de garantir le bon fonctionnement de la partie AC et de la partie DC. Cependant, l'utilisation des deux droop génère un couplage indésirable entre les deux commandes. Ces interactions sont mathématiquement quantifiées et une correction à apporter au paramètre de frequency droop est proposée. Ces résultats sont ensuite validés par des simulations EMT et par des essais sur la plate-forme MTDC du laboratoire L2EPHVDC transmission systems are largely used worldwide, mostly in the form of back-to-back and point-to-point HVDC, using either thyristor-based LCC or IGBT-based VSC. With the recent deployment of the INELFE HVDC link between France and Spain, and the commissioning in China of a three-terminal HVDC transmission system using Modular Multilevel Converters (MMCs), a modular design of voltage source converters, the focus of the scientific community has shifted onto the analysis and control of MMC-based HVDC transmission systems. In this thesis, the average value models of both a standard 2-level VSC and an MMC are proposed and the most interesting difference between the two converter technologies -the control of the stored energy in the MMC- is emphasised and explained. These models are then linearised, expressed in state-space form and validated by comparing their behaviour to more detailed models under EMT programs. Afterwards, these state-space representations are used in the modelling of HVDC transmission systems, either point-to-point or Multi-Terminal HVDC (MTDC). A modal analysis is performed on an HVDC link, for both 2-level VSCs and MMCs. The modes of these two systems are specifed and compared and the independent control of the DC voltage and the DC current in the case of an MMC is illustrated. This analysis is extended to the scope of a 5-terminal HVDC system in order to perform a stability analysis, understand the origin of the system dynamics and identify the dominant DC voltage mode that dictates the DC voltage response time. Using the Singular Value Decomposition method on the MTDC system, the proper design of the voltage-droop gains of the controllers is then achieved so that the system operation is ensured within physical constraints, such as the maximum DC voltage deviation and the maximum admissible current in the power electronics. Finally, a supplementary droop "the frequency-droop control" is proposed so that MTDC systems also participate to the onshore grids frequency regulation. However, this controller interacts with the voltage-droop controller. This interaction is mathematically quantified and a corrected frequency-droop gain is proposed. This control is then illustrated with an application to the physical converters of the Twenties project mock-up
4
Nazari, Mohammad. "Control of DC voltage in Multi-Terminal HVDC Transmission (MTDC) Systems." Licentiate thesis, KTH, Elektriska energisystem, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-147551.
Abstract:
With recent advances in power electronic technology, High-Voltage Direct Current (HVDC) transmission system has become an alternative for transmitting power especially over long distances. Multi-Terminal HVDC (MTDC) systems are proposed as HVDC systems with more than two terminals. These systems can be geographically wide. While in AC grids, frequency is a global variable, in MTDC systems, DC voltage can be considered as its dual. However, unlike frequency, DC voltage can not be equal across the MTDC system. Control of DC voltage in MTDC systems is one of the important challenges in MTDC systems. Since the dynamic of MTDC system is very fast, DC voltage control methods cannot rely only on remote information. Therefore, they can work based on either local information or a combination of local and remote information. In this thesis, first, the MTDC system is modeled. One of the models presented in this thesis considers only the DC grid, and effects of the AC grids are modeled with DC current sources, while in the other one, the connections of the DC grid to the AC grids are also considered. Next, the proposed methods in the literature for controlling the DC voltage are described and in addition to these methods, some control methods are proposed to control the DC voltage in MTDC system. These control methods include two groups. The first group (such as Multi-Agent Control methods) uses remote and local information, while the second group (such as Sliding Mode Control and H¥ control) uses local information.The proposed multi-agent control uses local information for immediate response, while uses remote information for a better fast response. Application of Multi-Agent Control systems leads to equal deviation of DC voltages from their reference values. Using remote information leads to better results comparing to the case only local information is used. Moreover, the proposed methods can also work in the absence of remote information. When AC grid is considered in the modeling, the MTDC system has anon-linear dynamic. Sliding Mode Control, a non-linear control method with high disturbance rejection capability, which is non-sensitive to the parameter variations, is applied to the MTDC system. It controls the DC voltage very fast and with small or without overshoot. Afterward, a static state feedback H¥ control is applied to the system which minimizes the voltage deviation after a disturbance and keeps the injected power of the terminals within the limits. Finally, some case studies are presented and the effectiveness of the proposed methods are shown. All simulations have been done in MATLAB and SIMULINK.QC 20140911
5
Akhter, Faheem. "Secure optimal operation and control of integrated AC/MTDC meshed grids." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/19531.
Abstract:
Offshore wind energy is seen as the most promising source of electricity generation for achieving the European renewable energy targets. A number of wind farms are planned and under installation to collect the huge potential of wind energy at farther distances in the North Sea. The number of HVDC links in the North Sea is expected to increase with the development of offshore installations in Round 3 of the UK offshore windfarm programme. The increasing number of HVDC links and high power transfer control requirements leads to the formation of Multi-Terminal HVDC (MTDC) grid systems, which have become possible due to the technical advancements of VSC based HVDC systems. Additionally, a meshed MTDC grid structure can also provide interconnections for power trade across the Europe, which can help in better utilisation of power from offshore installations and can also support the AC network in tackling wind power variation issues. However, the integration of the meshed MTDC grid with the existing AC grid has more challenges to overcome alongside the added advantages. One of the major challenge is to ensure the secure and optimal operation of the combined AC/MTDC grid considering stability requirements of the AC and DC grids in different operating conditions. The behaviour of the DC grid is governed by the fast acting controllers due to the high number of power electronic equipment unlike AC grid. In combined operation the response to a disturbance of two integrated grids can be different. The power balancing, co-ordination and dispatch requirements need to be identified, to implement appropriate controls and formulate a control structure for combined operation of two grids with different characteristics under normal and disturbance conditions. In this thesis, the basic principles of well-established three-layered AC grid control is employed to identify the power balancing, coordination and dispatch requirements of the DC grid. Appropriate control methods are proposed for primary, secondary and tertiary control layers in order to accomplish the identified requirements for the secure and optimal operation of combined AC/MTDC grids. Firstly, a comparison study is performed on different power balancing controls to find the most suitable control method for the primary control of the meshed DC grid. Secondly, the combined AC/DC grid power flow method is proposed to provide updated references of the VSC station in order to maintain coordinated power flow control under secondary control layers. Finally, security constraint optimization method for combined AC/DC grid is proposed for economic dispatch under the tertiary control layer of the three-layered hierarchal control. A number of case studies are performed to implement the proposed control methods on a combined AC/DC test case network. The performance of the proposed control methods is validated in a hierarchical control structure for secure and optimal operation integrated AC/MTDC grids.
6
Gonzalez-Torres, Juan Carlos. "Transient stability of high voltage AC-DC electric transmission systems." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS041.
Abstract:
Les nouvelles politiques adoptées par les autorités nationales ont encouragé pendant les dernières années l'intégration à grande échelle des systèmes d'énergie renouvelable (RES). L'intégration à grande échelle des RES aura inévitablement des conséquences sur le réseau de transport d'électricité tel qu'il est conçu aujourd'hui, car le transport de l'électricité massif sur de longues distances pourrait amener les réseaux de transport à fonctionner près de leurs limites, réduisant ainsi leurs marges de sécurité. Des systèmes de transport d’électricité plus complexes seront donc nécessaires.Dans ce scénario, les systèmes de transmission à Courant Continu Haute Tension (HVDC) constituent la solution la plus intéressante pour le renforcement et l'amélioration des réseaux à Courant Alternatif (AC) existants, non seulement en utilisant des configurations point à point, mais aussi dans des configurations multi-terminales. L'introduction des systèmes HVDC aboutira à terme à un réseau électrique hybride haute tension AC/DC, qui doit être analysé comme un système unique afin de mieux comprendre les interactions entre le réseau AC et le réseau DC.Cette thèse porte sur l'analyse de la stabilité transitoire des systèmes de transmission électrique hybrides AC/DC. Plus particulièrement, deux questions ont été abordées: Quel est l'impact d'un défaut du réseau DC sur la stabilité transitoire du réseau AC? Comment est-il possible de se servir des systèmes de transmission DC en tant qu'actionneurs afin d'améliorer la stabilité transitoire AC ?Dans la première partie de ce travail, les modèles mathématiques du réseau hybride AC/DC sont décrits ainsi que les outils nécessaires à l'analyse du système en tenant compte de sa nature non linéaire. Ensuite, une analyse approfondie de la stabilité transitoire du réseau électrique dans le cas particulier d'un court-circuit dans le réseau DC et l'exécution des stratégies de protection correspondantes sont effectuées. En complément, des indicateurs de stabilité et des outils pour dimensionner les futurs réseaux de la MTDC afin de respecter les contraintes des stratégies de protection existantes sont proposés.La deuxième partie de la thèse porte sur les propositions de commande pour la modulation des références de puissance des systèmes de transmission HVDC dans le but d'améliorer la stabilité transitoire du système AC connecté à ce réseau DC. Tout d'abord, nous axons notre étude sur le contrôle non linéaire des liaisons HVDC point à point dans des liaisons hybrides AC/DC. La compensation rapide des perturbations de puissance, l'injection de puissance d'amortissement et l'injection de puissance de synchronisation sont identifiées comme des mécanismes par lesquels les systèmes HVDC peuvent améliorer les marges de stabilité des réseaux AC.Enfin, une stratégie de contrôle pour l'amélioration de la stabilité transitoire par injection de puissance active dans par un réseau MTDC est proposée. Grâce à la communication entre les stations, la commande décentralisée proposée injecte la puissance d'amortissement et de synchronisation entre chaque paire de convertisseurs en utilisant uniquement des mesures au niveau des convertisseurs. L'implémentation proposée permet d'utiliser au maximum la capacité disponible des convertisseurs en gérant les limites de puissance d'une manière décentraliséeThe new policy frameworks adopted by national authorities has encouraged the large scale-integration of Renewable Energy Systems (RES) into bulk power systems. The large-scale integration of RES will have consequences on the electricity transmission system as it is conceived today, since the transmission of bulk power over long distances could lead the existing transmission systems to work close to their limits, thus decreasing their dynamic security margins. Therefore more complex transmissions systems are needed.Under this scenario, HVDC transmission systems raise as the most attractive solution for the reinforcement and improvement of existing AC networks, not only using point-to-point configurations, but also in a Multi-Terminal configuration. The introduction of HVDC transmission systems will eventually result in a hybrid high voltage AC/DC power system, which requires to be analyzed as a unique system in order to understand the interactions between the AC network and the DC grid.This thesis addresses the transient stability analysis of hybrid AC/DC electric transmission systems. More in particular, two questions sought to be investigated: What is the impact of a DC contingency on AC transient stability? How can we take advantage of the of DC transmission systems as control inputs in order to enhance AC transient stability?In the first part of this work, the mathematical models of the hybrid AC/DC grid are described as well as the necessary tools for the analysis of the system taking into account its nonlinear nature. Then, a thorough analysis of transient stability of the power system in the particular case of a DC fault and the execution of the corresponding protection strategies is done. As a complement, stability indicators and tools for sizing future MTDC grids in order to respect the constraints of existing protection strategies are proposed.The second part of the thesis addresses the control proposals for the modulation of power references of the HVDC transmission systems with the purpose of transient stability enhancement of the surrounding AC system. Firstly, we focus our study in the nonlinear control of point-to-point HVDC links in hybrid corridors. Fast power compensation, injection of damping power and injection of synchronizing power are identified as the mechanisms through which HVDC systems can improve stability margins.Finally, a control strategy for transient stability enhancement via active power injections of an MTDC grid is proposed. Using communication between the stations, the proposed decentralized control injects damping and synchronizing power between each pair of converters using only measurements at the converters level. The proposed implementation allows to fully use the available headroom of the converters by dealing with power limits in a decentralized way
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Johansson, Henrik, and Lucas Tunelid. "Operation and Control of HVDC Grids." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-293882.
Abstract:
In order to meet the increasing demand ofenergy in today’s society while at the same time minimizing theenvironmental impact, renewable energy sources will be requiredto be integrated into the existing energy mix. Technologicaladvances in high voltage direct current (HVDC) grids playa crucial role in making this possible. Therefore the purposeof this project has been to validate the properties of basiccontrol strategies in terms of how they respond to four differentsimulation cases. All simulations have been conducted on asimplified version of the CIGR ́E B4 test grid, consisting offour monopolar HVDC converters. After analyzing the resultsobtained from each control strategy it became evident thatprovided if the benefits of the redundancy introduced by amulti-terminal grid are to be fully utilized, a distributed voltagecontrol should be used. Moreover, after substituting one ofthe four internal controllers with an external one, it becameclear that simply deciding the droop constants based on resultsfrom the simulation model wouldn’t be sufficient for real worldapplications.För att möta det ökande energibehovet i dagens samhälle, samtidigt som energiproduktionens miljöpåverkan ska minimeras, krävs det att förnyelsebara energikällor integreras i den existerande energimixen. Tekniska framsteg inom högspända likströmsnät (HVDC) spelar en avgörande roll i att göra detta möjligt. Därför har syftet med detta projekt varit att validera egenskaperna hos grundläggande kontrollstrategier efter hur dem reagerar på fyra olika simuleringsfall. Alla simuleringar har genomförts på en förenklad version av CIGRE´ B4 testsystem, bestående av fyra monopolära HVDC omriktare. Efter att analyserat de erhållna resultaten från varje kontrollstrategi blev det uppenbart att om fördelarna med multiterminala elnät skulle uppnås, bör en distribuerad spänningskontroll användas. Dessutom, efter att ha bytt ut en av dem fyra interna kontrollerna med en extern, visade det sig att endast bestämma droppkonstanterna baserat på resultat från simuleringsmodellen inte är tillräckligt för verkliga applikationer.
Kandidatexjobb i elektroteknik 2020, KTH, Stockholm
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Ahmadi, Seyedhesam, and Mehrdad Bahmani. "Reglering av effektflöde i HVDC-system genom centraliserad och distribuerad spänningskontroll i realtid." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-254267.
Abstract:
“High voltage direct current” (HVDC) teknologi har blivit allt viktigare teknik för att integrera förnybara energikällor i elnätet. För att styra ett sådant elsystem på bästa möjliga sätt krävs optimala kontrollstatergier både för omvandlarna och nätet. Så syftet med detta projekt är att undersöka hur olika regleringsmetoder, såsom centraliseradoch distribuerad spänningskontroll, kan påverka driften i ett 4-terminal HVDC-system. Ett optimalt effektflöde uppstår i systemet endast när likspänningen inte avviker från sitt börvärde och det uppnås genom att ha aktiv effekt regulator i varje nod i nätet. Olika scenarier som ändring av effektens börvärde och omvandlaravbrott har simulerats med hjälp av HIL-processen i realtid. Simuleringarna hjälper till att analysera hur väl dem implementerade regleringsmetoder i nodernas regulatorer hantera dessa förändringar. Resultatet ger bevis på att både centraliseradoch distruebued metoden har positiva och negativa aspekter. Fördelen med centraliserade metoden är att den ger en väldefinierad operationspunkt men den hanterar den inte svåra transienter (tex. avbrott) vilket distribuerade metoden gör.
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Shinoda, Kosei. "Contrôle et opération des réseaux HVDC multi-terminaux à base de convertisseurs MMC." Thesis, Ecole centrale de Lille, 2017. http://www.theses.fr/2017ECLI0017.
Abstract:
Cette thèse porte sur la commande de réseaux multi-terminaux à courant continu (MTDC) basés sur des convertisseurs multiniveaux modulaires (MMCs).Tout d’abord, notre attention se focalise sur l'énergie stockée en interne dans le MMC qui constitue un degré de liberté additionnel apporté par sa topologie complexe. Afin d’en tirer le meilleur parti, les limites de l’énergie interne sont formulées mathématiquement.Afin de maîtriser la dynamique de la tension DC, l’utilisation de ce nouveau degré de liberté s’avère d’une grande importance. Par conséquent, une nouvelle de stratégie de commande, nommée «Virtual Capacitor Control», est proposée. Cette nouvelle méthode de contrôle permet au MMC de se comporter comme s’il possédait un condensateur de taille réglable aux bornes, contribuant ainsi à l’atténuation des fluctuations de la tension DC.Enfin, la portée de l’étude est étendue au réseau MTDC. L'un des défis majeurs pour un tel système est de faire face à une perte soudaine d'une station de convertisseur qui peut entraîner une grande variation de la tension du système. A cet effet, la méthode de statisme de tension est la plus couramment utilisée. Cependant, l'analyse montre que l'action de contrôle souhaitée risque de ne pas être réalisée lorsque la marge disponible de réserve de puissance du convertisseur est insuffisante. Nous proposons donc une nouvelle structure de contrôle de la tension qui permet de fournir différentes actions en fonction du signe de l'écart de la tension suite à une perturbation, associée à un algorithme qui détermine les paramètres de statisme en tenant compte du point de fonctionnement et de la réserve disponible à chaque stationThe scope of this thesis includes control and management of the Modular Multilevel Converter (MMC)-based Multi-Terminal Direct Current (MTDC).At first, our focus is paid on the internally stored energy, which is the important additional degree of freedom brought by the complex topology of MMC. In order to draw out the utmost of this additional degree of freedom, an in-depth analysis of the limits of this internally stored energy is carried out, and they are mathematically formulated.Then, this degree of freedom of the MMC is used to provide a completely new solution to improve the DC voltage dynamics. A novel control strategy, named Virtual Capacitor Control, is proposed. Under this control, the MMC behaves as if there were a physical capacitor whose size is adjustable. Thus, it is possible to virtually increase the equivalent capacitance of the DC grid to mitigate the DC voltage fluctuations in MTDC systems.Finally, the scope is extended to MMC-based MTDC grid. One of the crucial challenges for such system is to cope with a sudden loss of a converter station which may lead to a great variation of the system voltage. The voltage droop method is commonly used for this purpose. The analysis shows that the desired control action may not be exerted when the available headroom of the converter stations are insufficient. We thus propose a novel voltage droop control structure which permits to provide different actions depending on the sign of DC voltage deviation caused by the disturbance of system voltage as well as an algorithm that determines the droop parameters taking into account the operating point and the available headroom of each station
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Bakhos, Gianni. "Gestion de la sécurité du réseau électrique AC & DC : évaluation et amélioration." Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALT014.
Abstract:
L'intégration des Énergies Renouvelables pose aujourd'hui des problèmes de congestion et d'incertitude sur le réseau électrique vu l'intermittence et l'imprévisibilité de ce type d'énergie. De plus, pour des questions de rentabilité et d'efficacité, la puissance produite à partir du renouvelable est transmise sous forme de Haute Tension en Courant Continu (HVDC). Un nouveau concept a donc émergé, celui de la fusion d'interconnexions HVDC dans un réseau maillé existant et ceci apportera plus de flexibilité dans le fonctionnement du système global. Le résultat : une hybridation du système de transmission d'électricité avec des interactions mutuelles importantes entre système AC existant et DC intégré. Si les problèmes de stabilité du réseau AC sont aujourd'hui identifiés, ceux du système hybride doivent encore être étudiés puisque l'intégration de convertisseurs de puissance commandables et contrôlables rapidement pourrait modifier le comportement du système entier. De ce fait, ce projet de thèse cherche à établir une étude innovante englobant tout le système hybride AC/DC. Celle-ci portera tout d'abord sur une évaluation de la sécurité prenant en compte les contraintes opérationnelles et la capacité du système à atteindre un nouvel équilibre. En outre, cette thèse relèvera les défis de stabilisation du système hybride global. Pour cela, les missions consisteront en une étude préliminaire de l'état de l'art : quelles nature physique des problèmes d'instabilité du système AC ? Quels types et gammes de perturbations à considérer pour l'évaluation de la stabilité ? Finalement, quels modélisation et contrôle du système HVDC ? Tout cela permettra de développer un outil inclusif d'évaluation de la sécurité prenant en compte différentes méthodes de contrôle du système. Une analyse sera également faite pour comprendre l'influence des paramètres et des méthodes de contrôle adoptés. Cela nous aidera à mettre en place un moyen de contrôle systématique pour améliorer la sécurité du réseau et optimiser la distribution de la puissance à travers un réseau Multi-Terminal DCToday, the integration of renewable energies poses problems of congestion and uncertainty on the electricity network, given the intermittency and unpredictability of this type of energy. What's more, for reasons of profitability and efficiency, the power generated from renewables is transmitted in the form of High Voltage Direct Current (HVDC). A new concept has therefore emerged, that of merging HVDC interconnections into an existing meshed network, which will bring greater flexibility to the operation of the overall system. The result is a hybrid electricity transmission system with significant mutual interactions between the existing AC system and the integrated DC system. While the stability problems of the AC network have now been identified, those of the hybrid system still need to be studied, since the integration of rapidly controllable power converters could modify the behaviour of the entire system. As a result, this thesis project seeks to establish an innovative study encompassing the entire AC/DC hybrid system. This will focus on a security assessment that takes into account operational constraints and the ability of the system to reach a new equilibrium. In addition, this thesis will address the stabilisation challenges of the overall hybrid system. To this end, the assignments will consist of a preliminary study of the state of the art: what is the physical nature of the instability problems of the AC system? What types and ranges of disturbances should be considered for stability assessment? Finally, what modelling and control of the HVDC system? All of this will enable the development of an inclusive security assessment tool that takes into account different system control methods. An analysis will also be carried out to understand the influence of the parameters and control methods adopted. This will help us to implement a systematic means of control to improve network security and optimise power distribution across a Multi-Terminal DC network
Book chapters on the topic "Hvdc; mtdc":
1
Irnawan, Roni. "Control of MTDC Transmission Systems." In Planning and Control of Expandable Multi-Terminal VSC-HVDC Transmission Systems, 35–59. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-27488-7_3.
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"MMC-HVDC Transmission Technology and MTDC Networks." In Design, Control and Application of Modular Multilevel Converters for HVDC Transmission Systems, 336–72. Chichester, UK: John Wiley & Sons, Ltd, 2016. http://dx.doi.org/10.1002/9781118851555.ch10.
Conference papers on the topic "Hvdc; mtdc":
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Zhao, Yi, Wentao Huang, Nengling Tai, and Xiaoping Tang. "Economy Optimization Configuration Scheme for the MMC-MTDC System with Renewable Energies." In 2020 4th International Conference on HVDC (HVDC). IEEE, 2020. http://dx.doi.org/10.1109/hvdc50696.2020.9292802.
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Long, M., X. Wang, B. Li, and R. Qian. "A chance-constrained power optimization method for MTDC considering PV and load uncertainties." In Annual Meeting of CSEE Study Committee of HVDC and Power Electronics (HVDC 2023). Institution of Engineering and Technology, 2023. http://dx.doi.org/10.1049/icp.2023.3036.
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Liu, G., P. Guo, Z. Yuan, and Y. Zhao. "Fault current suppression for MMC-MTDC with the resistive type superconducting fault current limiter." In 2021 Annual Meeting of CSEE Study Committee of HVDC and Power Electronics (HVDC 2021). Institution of Engineering and Technology, 2021. http://dx.doi.org/10.1049/icp.2021.2530.
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Liu, Siyuan, Ajay Shetgaonkar, and Marjan Popov. "Coordinative performance of HVDC circuit breakers in MTDC grids." In 2020 IEEE Power & Energy Society General Meeting (PESGM). IEEE, 2020. http://dx.doi.org/10.1109/pesgm41954.2020.9281921.
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Khan, S. A., C. Liu, and J. A. Ansari. "Unified voltage droop control strategy for VSC-MTDC in HVDC system." In The 16th IET International Conference on AC and DC Power Transmission (ACDC 2020). Institution of Engineering and Technology, 2021. http://dx.doi.org/10.1049/icp.2020.0184.
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Kangwa, Nsofwa M., Chitra Venugopal, and Innocent E. Davidson. "A review of the performance of VSC-HVDC and MTDC systems." In 2017 IEEE PES/IAS PowerAfrica. IEEE, 2017. http://dx.doi.org/10.1109/powerafrica.2017.7991235.
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Sun, Jianlong, Xiao Han, Yan Li, Zheren Zhang, Zheng Xu, and Yuzhe Xu. "Study of Superconducting Fault Current Limiters for MMC-MTDC with HVDC CBs." In 2019 IEEE Innovative Smart Grid Technologies - Asia (ISGT Asia). IEEE, 2019. http://dx.doi.org/10.1109/isgt-asia.2019.8881817.
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Bernal-Perez, S., S. Ano-Villalba, R. Blasco-Gimenez, and N. Aparicio. "Connection of off-shore wind power plants to VSC-MTdc networks using HVdc diode-rectifiers." In 2013 IEEE 22nd International Symposium on Industrial Electronics (ISIE). IEEE, 2013. http://dx.doi.org/10.1109/isie.2013.6563795.
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Han, Xiao, Yan Li, Jianlong Sun, Zheren Zhang, Zheng Xu, and Yuzhe Xu. "DC Side Main Circuit Parameter Selection of MMC-MTDC Systems with HVDC CBs and SFCLs." In 2018 International Conference on Power System Technology (POWERCON). IEEE, 2018. http://dx.doi.org/10.1109/powercon.2018.8602287.
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Kumar, Ancha Satish, and Bibhu Prasad Padhy. "Headroom based Frequency and DC-Voltage Control for Large Disturbances in Multi-Terminal HVDC (MTDC) Grids." In 2022 IEEE International Conference on Power Electronics, Drives and Energy Systems (PEDES). IEEE, 2022. http://dx.doi.org/10.1109/pedes56012.2022.10080455.