| 1. |
- Babazadeh, Davood, et al.
(författare)
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Real-Time Estimation of AC-Grid Short Circuit Capacity for HVDC Control Application
- 2016
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Ingår i: IET Generation, Transmission & Distribution. - : IET. - 1751-8687 .- 1751-8695.
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Tidskriftsartikel (refereegranskat)abstract
- Being able to estimate the AC grid strength using Short Circuit Capacity (SCC) fromthe perspective of a connected HVDC station allows adjustment of converter control parameters orto select the converter’s operational control mode. The short circuit capacity can be calculated byestimation of the grid’s impedance and its equivalent voltage. This paper presents the operationaland practical challenges in real-time implementation of the grid estimation algorithms especiallyfor HVDC applications. This paper shows that the Recursive Least Square (RLS) algorithm can bevery efficiently used for the real-time estimation of SCC. This technique forms a regression prob-lem using algebraic complex equations with an objective to minimize the error between estimatedand measured parameters. The algorithm has been reformulated and simplified to make it non-complex without the use of matrices, in order to facilitate further implementation on an industrialreal-time controller. The performance of the real-time implementation has been evaluated usinga HIL platform. A sensitivity analysis has been also carriedout to study the impact of differentparameters and operational conditions on the performance of the estimation algorithm. Finally, theactual application of real-time SCC estimation for the HVDCsystems has been demonstrated.
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| 2. |
- Babazadeh, Davood, et al.
(författare)
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Selection of DC Voltage Controlling Station in an HVDC Grid
- 2016
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Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 144, s. 224-232
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a real-time quantitative evaluation of HVDC converters’ in an HVDC grid to select the suitable DC slack converter. This real-time evaluation considers the strength of connecting AC grid and the converter's on-line capacity margin as selection metrics. The strength of AC grid is evaluated in real-time by the estimation of grid short circuit capacity using recursive lease square algorithm. Given these selection metrics, the credibility of HVDC stations in controlling the DC voltage can be offered to the system operator in real-time for further operational decisions. This paper also studies the practical aspect of the estimation algorithm regarding selection of the operating points. As major contribution, it suggests to intelligently use a naturally occurring droop response in HVDC grids as a second operating point in the estimation algorithm to calculate the short circuit capacity. The method has been tested through set of scenarios using a real-time co-simulation platform. This platform includes real-time power system simulator to model AC/DC grid, industrial HVDC controllers and corresponding ICT systems. The results show that the proper selection of DC slack station can improve the AC system response and DC voltage drops during disturbances.
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| 3. |
- Babazadeh, Davood, et al.
(författare)
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Short Circuit Capacity Estimation for HVDC Control Application
- 2016
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Ingår i: Power Systems Computation Conference (PSCC), 2016. - : IEEE conference proceedings.
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Konferensbidrag (refereegranskat)abstract
- This paper studies various operational aspects ofrecursive least square algorithm as a potential solution for theestimation of short circuit capacity in HVDC application. Inthis work, low computational requirement, minor operationalcomplication and acceptable accuracy of the estimated gridparameters have been considered as the performance metricsfor the selection of the suitable estimation algorithm. The chosenalgorithm forms a regression problem using at least two algebraiccomplex equations based on two different operating points. Theappropriate selection of the second operating point which fulfillsthe minimum required accuracy and convergence rate is of greatimportance, particularly in the practical implementation. Thispaper proposes and analyzes several choices of providing thesecond operating point for the estimation algorithm adopted toHVDC application. Furthermore, a sensitivity analysis has beencarried out to assess the impact of different parameters andoperational conditions such as execution time on the performanceof the estimation algorithm for the HVDC control purposes.
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| 4. |
- Clark, Angel, et al.
(författare)
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Development of a Base Model in RMS and EMT Environment to Study Low Inertia System
- 2021
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Ingår i: IEEE General Meeting Power& Energy Society. - : Institute of Electrical and Electronics Engineers (IEEE).
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Konferensbidrag (refereegranskat)abstract
- This research performs a detailed comparison of fundamental frequency positive sequence (RMS) and electromagnetic transient (EMT) based simulations of a two-area four-machine system with power-electronics based non-synchronous generation (NSG). The RMS based simulations are performed in PowerFactory and the equivalent EMT simulations are performed in PSCAD. Parity between the two-area four-machine model constructed in PSCAD and PowerFactory is rigorously established. The default fully rated wind converter model from PowerFactory with fault ride through is adopted in PSCAD, utilizing the same control strategy. The transient stability of the two-area four-machine model with NSG in PSCAD and PowerFactory is evaluated with respect to one another. Specific RMS modeling limitations are also discussed in this paper.
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| 5. |
- Clark, Angel, et al.
(författare)
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EMT and RMS Analysis of a Two-Area System with Wind Power Generation
- 2020
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Konferensbidrag (refereegranskat)abstract
- In this work, a two-area four-machine system with wind power generation is developed in parallel in bothRMS and EMT environments. The fundamental frequency positive sequence (RMS) model is developed in DIgSILENTPowerFactory and the electromagnetic transient (EMT) model, in PSCAD. Specifically, this paper focuses on the systematicdevelopment of the comparable converter model in both environments. To model the wind farm, a PSCAD EMTvoltage source converter model is reconfigured and simplified to replicate the control of the default PowerFactory convertermodel that is used. The performance of the two models is assessed within a simple system, before integrating the windfarm into the two-area system. The selection of the control parameters is chosen in both models to provide a comparableresponse for a step change to the reference power. The default fault ride through (FRT) control is enabled in PowerFactoryand a FRT control strategy is developed in PSCAD to achieve a realistic response. A three-phase short circuit fault on a paralleltransmission line segment and a 100 MW load step change are independently applied in order to compare the dynamicresponse of both models. The specific limitations of converter modelling in RMS simulations are discussed.
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| 6. |
- Fornari, Walter, et al.
(författare)
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Rheology of Confined Non-Brownian Suspensions
- 2016
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 116:1
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Tidskriftsartikel (refereegranskat)abstract
- We study the rheology of confined suspensions of neutrally buoyant rigid monodisperse spheres in plane-Couette flow using direct numerical simulations. We find that if the width of the channel is a (small) integer multiple of the sphere diameter, the spheres self-organize into two-dimensional layers that slide on each other and the effective viscosity of the suspension is significantly reduced. Each two-dimensional layer is found to be structurally liquidlike but its dynamics is frozen in time.
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| 7. |
- Fornari, Walter, 1989-, et al.
(författare)
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Rheology of extremely confined non-Brownian suspensions
- 2016
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 116:1
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We study the rheology of confined suspensions of neutrally buoyant rigid monodisperse spheres in plane-Couetteflow using Direct Numerical Simulations.We find that if the width of the channel is a (small) integer multiple of the spherediameter, the spheres self-organize into two-dimensional layersthat slide on each other and the effective viscosity of the suspension issignificantly reduced. Each two-dimensional layer is found to be structurallyliquid-like but its dynamics is frozen in time.
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| 8. |
- Rogersten, Robert, et al.
(författare)
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A Quantitative Method for the Assessment of VSC-HVdc Controller Simulations in EMT Tools
- 2014
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Ingår i: Innovative Smart Grid Technologies Conference Europe (ISGT-Europe), 2014 IEEE PES. - : IEEE conference proceedings. ; , s. 1-5
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Konferensbidrag (refereegranskat)abstract
- Voltage-Source Converter-Based High-voltage dc (VSC-HVdc) technology has received growing interest during recent years due to its benefits for separated active and reactive power control. Before the installation of VSC-HVdc links, different simulation-based studies need to be performed, usually by different parties and using different electromagnetic transient (EMT) simulation platforms. This paper provides a systematic method to assess discrepancies between simulation tools. Models of the VSC and its control systems are implemented from scratch in two different tools. A metric and a methodology to quantitatively assess the discrepancies between simulation results is proposed and illustrated. The paper shows that even with a pedantic re-implementation of the models from the ground up, simulation results are still inconsistent. The objective of this paper is to develop a quantification method for comparing the models developed in different EMT simulation tool and to emphasize differences that can arise with the numerical solvers in such tools.
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| 9. |
- Rogersten, Robert, et al.
(författare)
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Applying Power-Synchronization Control in a Multi-Terminal DC System
- 2014
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Ingår i: 2014 IEEE PES General Meeting - Conference & Exposition. - : IEEE Computer Society. - 9781479964154
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Konferensbidrag (refereegranskat)abstract
- The performance of traditionally used converter control strategies in a multi-terminal dc system depends on the ac system conditions. One limiting factor for the converter controls to perform well is the short-circuit capacity of the ac system. This work is motivated by the rapid proliferation of high-voltage dc technology, which enables many converter stations being linked together by a dc transmission network. The dc network can be embedded in the conventional ac network and used to facilitate large power transfers across great distances between the interconnecting terminals. A previously proposed control method, power-synchronization control, has been demonstrated to perform well on a point-to-point high-voltage direct current link in connection to a weak ac system. In this paper, the potential of power-synchronization control is demonstrated in a multi-terminal dc grid with one very weak ac system connection.
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