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The increased number of renewable energy sources causes regional imbalances in power generation. HVDC based systems present one option to provide the transmission capacity needed to compensate these imbalances. This paper presents a methodology for the design of an embedded HVDC overlay grid. An aggregated model of the European transmission network and load/generation scenarios for the year 2020 are...
This paper deals with the modelling of high-voltage direct current (HVDC) breakers in PSCAD. The models are aimed at HVDC grid simulation and are kept as simple as possible. An overview is given over recently proposed HVDC breaker concepts. Assumptions and simplifications are explained as well. The main result is that even these simplified models are too detailed for grid simulations. The reason for...
Decarbonisation of the European electricity system can become dauntingly costly due to transmission and distribution network issues arising from the integration of intermittent renewable generation sources. It is expected that wind energy will be the principal renewable source by 2050 and, as such, a number of initiatives in the academia and in the industry are being carried out to propose solutions...
This paper investigates the impact of different control modes of VSC HVdc to the transient stability of power systems. VSC HVdc offers fast bi-directional power control in addition to fast ac voltage control. This feature is utilized in this study to enhance the transient stability of a conventional generator in a power system. Simulations are carried-out for three scenarios: (i) the generator is...
This paper is focused in the control design of a DC/DC Current Flow Controller (CFC) for meshed HVDC grids. It proposes a control design methodology based on an outer current loop to regulate DC grid currents and an inner voltage loop to keep under control the CFC voltage. This approach is able to limit the CFC voltage to avoid exceeding the device limitations. A linear model of the HVDC grid including...
The large-scale penetration of renewable generation into power systems has required an integration of wind and conventional thermal generation. This has been supported by high-voltage direct-current lines for bulk power transmission as wind generation is normally located far away from the load centres. The participation of wind generators in primary frequency regulation and stability has become an...
This paper deals with a radial offshore multi-terminal HVDC (MTDC) transmission system which is formed by interconnection several existing offshore wind farm (OWF) HVDC links with a shore-to-shore (StS) HVDC link. A challenge arises when deciding the steady-state DC voltage operating level of this MTDC system due to the inherited limit from point-to-point (PtP) configuration. An analytic method is...
This paper discusses the applicability of a Full-Bridge MMC and a Half-bridge MMC to tap an LCC-HVDC. The suitability of the two types of converters has been evaluated by considering the performance of the LCC-HVDC system under AC and DC fault conditions. The energization sequences control and protection modifications to the LCC-HVDC system, equipment requirements associated with each converter technology...
This article presents preliminary results from ongoing work on establishing a simulation model for R&D activities on the impact of the increasing number of HVDC links in the Nordic power grid. The total HVDC power capacity will be 13100 MW (excluding some smaller systems) by 2021. This study addresses a future scenario with additional 7400 MW of HVDC interconnection capacity for power exchange...
HVDC links, FACTS and wind farms under construction in France and worldwide are embedded in highly meshed networks. The risk of interactions between such power electronics components can impact the performance of the network. This paper provides the different types of interactions that can occur between power electronics equipment and an analytical criteria to investigate the risk of interactions...
This paper presents a structured approach for analysing the effect of HVDC transmission system expansion on the small signal dynamics. The methodology decomposes the expansion of the system into a sequence of steps and aims especially at identifying the eigenvalues associated with interactions between the initial system and an added converter terminal. The procedure is illustrated with an example...
In this paper, a voltage droop control tuning strategy for a four-terminal high-voltage direct current (HVDC) grid is described, considering the DC multi-terminal grid, the AC grid and the modular multilevel converter (MMC) dynamics. A linear state-space model for such a system is derived including the different converter controllers. Based on this model, the primary DC grid droop voltage control...
This paper assesses the accuracy of a transient 2D axis-symmetric FE model of a Thomson coil actuator compared with experimental results. Sources of error in the coil representation are identified and the 2D model is compensated accordingly for improved accuracy. Experimental results validate the proposed approach and effects of armature bending in the predicted armature velocity are investigated...
This paper applies frequency scanning techniques to the calculation of multi-infeed interaction factor (MIIF) at harmonic frequencies as a screening method for harmonic interactions of HVDC systems. The frequency scan technique is compared with the EMT simulations based current injection method, which is commonly used for MIIF calculations, for a set of test cases and is shown to be a faster, convenient...
System stability can be affected by the interaction between the converter control and the network resonances. Current installations of VSC-HVDC converters have experienced instability issues due to this interaction and have triggered questions in industry and research such as the suitable methods to evaluate the interferences, the necessary models in order to determine them and the techniques to mitigate...
This paper investigates the coupling effect on overhead halfbridge (HB) and full-bridge (FB) MMC-HVDC transmission lines from paralleled ac transmission lines in the same right-of-way. A detailed electromagnetic HB/FB MMC-HVDC model is built and the coupled ac/dc overhead line is included in this model. The impact of the coupling line length and ac current in ac line is investigated. Three mitigation...
At present, (N-1)-security of AC-HVDC-systems is evaluated separately for both the AC and HVDC grid. The application of Voltage Source Converters (VSCs) ensures a controlled power exchange between both systems. This enables a combined system operation and therefore a combined security consideration of both systems. This work proposes a Preventive Security Constrained Optimal Power Flow (PSCOPF) which...
FACTS and HVdc systems may adversely affect the torsional dynamics of a turbine-generator system. Eigen-value analysis is a powerful approach for analysis of such instabilities. The size of the system is not a major constraint, as efficient selective eigen-value analysis tools are widely available. Eigen-value analysis requires an accurate small-signal model of the complete system including the Power...
This paper investigates the potential resonance of the MMC-MTDC system excited by ac background harmonics. First, the impact of ac background harmonics on one MMC is explored by using phase-leg voltage analysis. Then, the frequency-impedance characteristics of the MMC-MTDC system is explored to illustrate the reason why the dc network resonance occurs. Finally appropriate selection of the smoothing...
High voltage DC circuit breakers (DC CB) are essential components for the future DC transmission grid. One of the challenges after manufacturing the DC CB is testing it and confirming the working of the DC CB under different conditions. In this paper, a 320kV, 1.5kA test circuit is proposed for testing DC CB in conditions very close to real DC transmission systems. In the proposed circuit topology...
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