| 1. |
- Bollen, Math, et al.
(författare)
-
Trends, challenges and opportunities in power quality research
- 2010
-
Ingår i: European transactions on electrical power. - : Wiley. - 1430-144X .- 1546-3109. ; 20:1, s. 3-18
-
Tidskriftsartikel (refereegranskat)abstract
- This paper outlines a number of possible research directions in power quality. The introduction of new sources of generation will introduce the need for new research on voltage-magnitude variations, harmonic emission and harmonic resonance. Statistical performance indicators are expected to play an important role in addressing the hosting capacity of the power system for these new sources. The quickly growing amounts of power-quality data call for automatic analysis methods. Advanced signal-processing tools need to be developed and applied to address this challenge. Equipment with an active power-electronic interface generates waveform distortion at higher frequencies than existing equipment. The emission, spread, consequences and mitigation of this distortion require more research emphasis. The growing complexity of the power system calls for remote identification of system events and load transitions. Future DC networks, at different voltage levels, require the research on DC power quality next to AC power quality. Research on methods to describe and analyse time-varying harmonics has applications in a number of the above-mentioned issues. So does the use of hardware-in-the-loop (HIL) and real-time-digital simulation. Existing power quality standards should not form a barrier against future research; instead research should result in improved standards as well as completely new concepts. Examples are: voltage dips in three-phase systems, flicker due to non-incandescent lamps, and voltage variations on the timescale between 1 second and 10 minutes. All together, it is concluded in this paper that sufficient important and interesting research challenges and opportunities remain in the power quality area.
|
|
| 2. |
- Chompoobutrgool, Yuwa, 1984-, et al.
(författare)
-
Survey on Power System Stabilizers Control and their Prospective Applications for Power System Damping using Synchrophasor-Based Wide-Area Systems
- 2011
-
Ingår i: European transactions on electrical power. - : John Wiley & Sons. - 1430-144X .- 1546-3109. ; 21:8, s. 2098-2111
-
Tidskriftsartikel (refereegranskat)abstract
- Powersystemoscillationdampingremains as one of the major concerns for secure and reliable operation of largepowersystems, and is of great current interest to both industry and academia. The principal reason for this is that the inception of poorly-damped low-frequency inter-areaoscillations (LFIOs) whenpowersystemsare operating under stringent conditions may lead tosystem-widebreakups or considerably reduce thepowertransfers over critical corridors. With the availability of high-sampling rate phasor measurement units (PMUs), there is an increasing interest for effectively exploiting conventionaldampingcontroldevices, such aspowersystemstabilizers(PSSs), by using these measurements ascontrolinput signals. In this paper, we provide a comprehensive overview of distinct elements (or "building blocks") necessary forwide-areapowersystemdampingusing synchrophasors and PSSs. These building blocks together shape a tentative methodical framework, and are disposed as follows: (1) fundamental understanding of the main characteristics of inter-areaoscillations, (2)wide-areameasurement andcontrolsystems(WAMS and WACS) andwide-areadampingcontrol(WADC), (3) advanced signal processing techniques for mode property identification, (4) methods for model-basedsmall-signal analysis, (5)controlinput signals selection, and (6) methods for PSScontroldesign. We also describe the latest developments in the implementation ofsynchrophasormeasurements in WAMS and WACS as well as their prospectives for WADCapplications. This paper serves both to abridge the state-of-the-art in each of these elements, and to accentuate aspiring ideas in each building block.
|
|
| 3. |
- Eriksson, Robert, et al.
(författare)
-
Optimal coordinated control of multiple HVDC links for power oscillation damping based on model identification
- 2012
-
Ingår i: European transactions on electrical power. - : Wiley. - 1430-144X .- 1546-3109. ; 22:2, s. 188-205
-
Tidskriftsartikel (refereegranskat)abstract
- This paper deals with optimal coordinated control of several high voltage direct current (HVDC) links based on an estimated model of large power systems. The model of the power system is estimated by using subspace system identification techniques. An optimal controller is designed based on the estimated model with the aim to improve the damping in the system. The main contribution of this paper is the development of a new method which uses global Phasor measurement units (PMUs) signals for coordinated damping control of multiple HVDC links. The input signals are the controllable set-points of the HVDC links, the output signals are the speed signals of selected generators obtained from PMU. The PMU signals are used to estimate the current state of the model, i.e., the state of the system, an appropriate control action can then be applied to dampen the system. The benefit of the method is that the used output signals, i.e., the used PMU signals, are independent of the system equilibrium and therefore makes it possible to use state-feedback control, i.e., coordinated control. The method is applied to the Cigre Nordic 32-bus system including two HVDC links. The consistent results show that the damping can be significantly increased.
|
|
| 4. |
- Eriksson, Robert, et al.
(författare)
-
Transfer capacity enhancement by adaptive coordinated controlof HVDC-links based on forecasted load paths
- 2011
-
Ingår i: European transactions on electrical power. - : Wiley. - 1430-144X .- 1546-3109. ; 21:3, s. 1455-1466
-
Tidskriftsartikel (refereegranskat)abstract
- Due to the intensive use of the transmission networks one of the major issues in electric energy trading is bottlenecks limiting the transfer capacity between different system areas. In this article, a new method for increasing transfer capacity is suggested. The increase in transfer capacity is obtained by an adaptive coordinated modulation control of multiple HVDC-links in the system. The control method is based on maximizing the distance to the bifurcation surface by adjusting the feedback gain of the HVDC-links modulation controllers. The system is linearized along the forecasted load path. The feedback gains are then chosen in such a way that system remains stable, in a small signal sense, as long as possible along the forecasted load path. The arising optimization problem is then solved using a particle swarm optimization method. If the load is predicted to increase, instability will eventually occur when the loading reaches a critical limit. Using the proposed control method the point in load-space where instability occur will be at a significantly higher loading level. The main contribution of this paper is the proposed new method for adaptively coordinating the power modulation of multiple HVDC-links in a power system, to enhance the total transfer capacity. This in turn will lead to a possibility to increase the traded volumes on the electricity market.
|
|
| 5. |
- Holmberg, Pär, et al.
(författare)
-
Coupled FEM and lumped circuit model of the electromagnetic response of coaxially insulated windings in two slot cores
- 2007
-
Ingår i: European transactions on electrical power. - : Wiley. - 1430-144X .- 1546-3109. ; 17:6, s. 554-568
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a coupled FEM and lumped circuit modelling approach that is primarily intended for high-frequency and overvoltage simulations of rotating electric machines with coaxially insulated windings, such as Powerformer and Motorformer. The magnetic fields and their interaction with the conductors of the winding are simulated with the aid of a FEM-program. The displacement current and its losses are modelled with an external lumped circuit. To consider eddy current losses, the stranded conductors and the laminated steel cores are replaced by homogeneous bodies with similar losses over a wide frequency range. The approach is illustrated and experimentally verified for a set-up with a cable wound around two slot cores. The model agrees well with measurements up to 1 MHz.
|
|
| 6. |
- Perninge, Magnus, 1980-, et al.
(författare)
-
Analysis of transfer-limit induced power system security by Markov chain Monte Carlo simulation
- 2012
-
Ingår i: European transactions on electrical power. - : Wiley. - 1430-144X .- 1546-3109. ; 22:2, s. 140-151
-
Tidskriftsartikel (refereegranskat)abstract
- Adequate security margins are commonly applied in power systems by keeping predefined transfer limits through certain transmission corridors in the system. These limits are often set to keep the criterion stating that the system should remain stable after the loss of any component. For many stability criteria such as, voltage stability, and voltage limits at specific nodes, the distribution of the injected power amongst the nodes of the system will be of vital importance. To incorporate this into the analysis of transfer limits the uncertainties in nodal loading and wind power production will have to be considered. In this article we propose a new method for generating samples of the power at all nodes given a set of transfers through specified corridors of the power system. It is then shown how the method can be used to evaluate the risk of violating the system stability limits induced by choosing a specific set of transfer limits. The method can be used in power system operations planning when setting the limits for trading and transfer between the different nodes of the power system.
|
|
| 7. |
- Perninge, Magnus, et al.
(författare)
-
Modeling the electric power consumption in a multi-area system
- 2011
-
Ingår i: European transactions on electrical power. - : Wiley. - 1430-144X .- 1546-3109. ; 21:1, s. 413-423
-
Tidskriftsartikel (refereegranskat)abstract
- In this article a model of the electric power consumption in a multi-area power system is derived. The model is based on stochastic differential equations to mimic the stochastic behavior of electric power consumption in large systems. The developed model considers correlations between the consumptions in the different areas. A numerical example showing how to find the parameters of the process will be given. The load data used in the numerical example is hourly energy consumption data for the Nordic countries: Sweden, Norway, and Finland.
|
|
| 8. |
- Stadler, Michael, et al.
(författare)
-
Control of greenhouse gas emissions by optimal DER technology investment and energy management in zero-net-energy buildings
- 2011
-
Ingår i: European transactions on electrical power. - : Wiley. - 1430-144X .- 1546-3109. ; 21:2, s. 1291-1309
-
Tidskriftsartikel (refereegranskat)abstract
- The U.S. Department of Energy has launched the commercial building initiative (CBI) in pursuit of its research goal of achieving zero-net-energy commercial buildings (ZNEB), i.e., ones that produce as much energy as they use. Its objective is to make these buildings marketable by 2025 such that they minimize their energy use through cutting-edge, energy-efficiency technologies and meet their remaining energy needs through on-site renewable energy generation. This paper examines how such buildings may be implemented within the context of a cost-or CO2-minimizing microgrid that is able to adopt and operate various technologies: photovoltaic (PV) modules and other on-site generation, heat exchangers, solar thermal collectors, absorption chillers, and passive/demand-response technologies. A mixed-integer linear program (MILP) that has a multi-criteria objective function is used. The objective is minimization of a weighted average of the building's annual energy costs and CO2 emissions. The MILP's constraints ensure energy balance and capacity limits. In addition, constraining the building's energy consumed to equal its energy exports enables us to explore how energy sales and demand-response measures may enable compliance with the ZNEB objective. Using a commercial test site in northern California with existing tariff rates and technology data, we find that a ZNEB requires ample PV capacity installed to ensure electricity sales during the day. This is complemented by investment in energy-efficient combined heat and power (CHP) equipment, while occasional demand response saves energy consumption. A large amount of storage is also adopted, which may be impractical. Nevertheless, it shows the nature of the solutions and costs necessary to achieve a ZNEB. Additionally, the ZNEB approach does not necessary lead to zero-carbon (ZC) buildings as is frequently argued. We also show a multi-objective frontier for the CA example, which allows us to estimate the needed technologies and costs for achieving a ZC building or microgrid.
|
|
| 9. |
- Tavakoli, Hanif, et al.
(författare)
-
Localization of mechanical deformations in transformer windings using time-domain representation of response functions
- 2014
-
Ingår i: European transactions on electrical power. - : Hindawi Limited. - 1430-144X .- 1546-3109. ; 24:1, s. 16-29
-
Tidskriftsartikel (refereegranskat)abstract
- Time domain reflectometry (TDR) has been used for localization of discontinuities in transmission lines in diverse applications. In this paper, its potential as an alternative to frequency response analysis for the detection and localization of mechanical changes (damages) in transformer windings is investigated. This is done by computer simulations of a lumped-element circuit model of a disc winding which has been verified with measurements on an experimental coil. We also suggest that the idea of TDR can be used to visualize the results of frequency response measurements in time domain, where they are easier to interpret. When applying TDR to transformer windings instead of transmission lines, two main new problems have to be addressed, namely (i) the basic inhomogeneity of most winding designs, and (ii) the strong effect of dispersion (distortion of signals as they travel along the winding). We argue that TDR is still useful under these circumstances if it is applied as a differential method and in the right frequency window, i.e. using signals of suitable shapes. Under these conditions, it allows the detection and, to some extent, localization of certain mechanical changes in a transformer winding.
|
|
| 10. |
- Vanfretti, Luigi, et al.
(författare)
-
Application of ambient analysis techniques for the estimation of electromechanical oscillations from measured PMU data in four different power systems
- 2011
-
Ingår i: European transactions on electrical power. - : Wiley-Blackwell. - 1430-144X .- 1546-3109. ; 21:4, s. 1640-1656
-
Tidskriftsartikel (refereegranskat)abstract
- The application of advanced signal processing techniques to power system measurement data for the estimation of dynamic properties has been a research subject for over two decades. Several techniques have been applied to transient (or ringdown) data, ambient data, and to probing data. Some of these methodologies have been included in off-line analysis software, and are now being incorporated into software tools used in control rooms for monitoring the near real-time behavior of power system dynamics. In this paper we illustrate the practical application of some ambient analysis methods for electromechanical mode estimation in different power systems. We apply these techniques to phasor measurement unit (PMU) data from stored archives of several hours originating from the US Eastern Interconnection (EI), the Western Electricity Coordinating Council (WECC), the Nordic Power System, and time-synchronized Frequency Disturbance Recorder (FDR) data from Nigeria. It is shown that available signal processing tools are readily applicable for analysis of different power systems, regardless of their specific dynamic characteristics. The discussions and results in this paper are of value to power system operators and planners as they provide information of the applicability of these techniques via readily available signal processing tools, and in addition, it is shown how to critically analyze the results obtained with these methods.
|
|
