8,753 research outputs found
Improved methodologies for security of electricity supply of future power system
The security of electricity supply has always been important, but it has recently
become one of the critical issues for the planning and operation of modern electricity
networks. There are several reasons for that, including increased demands and
deregulation of electricity markets, resulting in much lower infrastructural investments,
which both pushed existing networks to operate closer to their security limits. The
increasing penetration levels of variable and inherently non-dispatchable renewable
energy resource, as well as the implementation of demand-responsive controls and
technologies on the demand side, together with the application of real-time thermal
ratings for system components, have introduced an unprecedented level of
uncertainties into the system operation. These uncertainties present genuinely new
challenges for the maintenance of high system security levels.
The first contribution of this thesis is the development of advanced computational tools
to strengthen the decision-making capabilities of system operators and ensure secure
and economic operation under high uncertainty levels. It initially evaluates the hosting
capacities for wind-based generation in a distribution network subject to operational
security limits. In order to analyse the impacts of variations and uncertainties in the
wind-based generation, loads and dynamic thermal ratings of network components,
both deterministic and probabilistic approaches are applied for hosting capacity
assessment at each bus, denoted as “locational hosting capacity”, which is of interest
to distributed generation (DG) developers. Afterwards, the locational hosting
capacities are used to determine the hosting capacity of the whole network, denoted as
“network hosting capacity”, which is of primary interest to system operators. As the
available hosting capacities change after the connection of any DG units, a sensitivity
analysis is implemented to calculate the variations of the remaining hosting capacity
for any number of DG units connected at arbitrary network buses.
The second contribution of this thesis is a novel optimisation model for the active
management of networks with a high amount of wind-based generation and utilisation
of dynamic thermal ratings, which employs both probabilistic analysis and interval/affine arithmetic for a comprehensive evaluation of related uncertainties.
Affine arithmetic is applied to deal with interval information, where the obtained
interval solutions cover the full range of possible optimal solutions, with all
realisations of uncertain variables. However, the interval solutions overlook the
probabilistic characteristics of uncertainties, e.g. a likely very low probabilities around
the edges of intervals. In order to consider realistic probability distribution information
and to reduce overestimation errors, the affine arithmetic approach is combined with
probabilistic (Monte Carlo) based analysis, to identify the suitable ranges of
uncertainties for optimal balancing of risks and costs.
Finally, this thesis proposes a general multi-stage framework for efficient management
of post-contingency congestions and constraint violations. This part of the work uses
developed thermal models of overhead lines and transformers to calculate the
maximum lead time for system operators to resolve constraint violations caused by
post-fault contingency events. The maximum lead time is integrated into the
framework as the additional constraint, to support the selection of the most effective
corrective actions. The framework has three stages, in which the optimal settings for
volt-var controls, generation re-dispatch and load shedding are determined
sequentially, considering their response times. The proposed framework is capable of
mitigating severe constraint violations while preventing overheating and overloading
conditions during the congestion management process. In addition, the proposed
framework also considers the costs of congestion management actions so that the
effective corrective actions can be selected and evaluated both technically and
economically
Power quality and electromagnetic compatibility: special report, session 2
The scope of Session 2 (S2) has been defined as follows by the Session Advisory Group and the Technical Committee: Power Quality (PQ), with the more general concept of electromagnetic compatibility (EMC) and with some related safety problems in electricity distribution systems.
Special focus is put on voltage continuity (supply reliability, problem of outages) and voltage quality (voltage level, flicker, unbalance, harmonics). This session will also look at electromagnetic compatibility (mains frequency to 150 kHz), electromagnetic interferences and electric and magnetic fields issues. Also addressed in this session are electrical safety and immunity concerns (lightning issues, step, touch and transferred voltages).
The aim of this special report is to present a synthesis of the present concerns in PQ&EMC, based on all selected papers of session 2 and related papers from other sessions, (152 papers in total). The report is divided in the following 4 blocks:
Block 1: Electric and Magnetic Fields, EMC, Earthing systems
Block 2: Harmonics
Block 3: Voltage Variation
Block 4: Power Quality Monitoring
Two Round Tables will be organised:
- Power quality and EMC in the Future Grid (CIGRE/CIRED WG C4.24, RT 13)
- Reliability Benchmarking - why we should do it? What should be done in future? (RT 15
Solar Enablement Initiative in Australia: Report on Efficiently Identifying Critical Cases for Evaluating the Voltage Impact of Large PV Investment
The increasing quantity of PV generation connected to distribution networks
is creating challenges in maintaining and controlling voltages in those
distribution networks. Determining the maximum hosting capacity for new PV
installations based on the historical data is an essential task for
distribution networks. Analyzing all historical data in large distribution
networks is impractical. Therefore, this paper focuses on how to time
efficiently identify the critical cases for evaluating the voltage impacts of
the new large PV applications in medium voltage (MV) distribution networks. A
systematic approach is proposed to cluster medium voltage nodes based on
electrical adjacency and time blocks. MV nodes are clustered along with the
voltage magnitudes and time blocks. Critical cases of each cluster can be used
for further power flow study. This method is scalable and can time efficiently
identify cases for evaluating PV investment on medium voltage networks
A review of the tools and methods for distribution networks' hosting capacity calculation
Integration of distributed energy resources (DERs) has numerous advantages as well as some disadvantages. To safely integrate DERs into a given distribution network and to maximize their benefits, it is important to thoroughly analyze the impact of DERs on that particular network. The maximum amount of DERs that a given distribution network can accommodate without causing technical problems or without requiring infrastructure modifications is defined as the hosting capacity (HC). In this work, a review of the recent literature regarding the HC is presented. The major limiting factors of HC are found to be voltage deviation, phase unbalance, thermal overload, power losses, power quality, installation location and protection devices’ miscoordination. The studies are found to employ one of four different methods for HC calculation: (i) deterministic, (ii) stochastic, (iii) optimization-based and (iv) streamlined. Commercially available tools for HC calculation are also presented. The review concludes that the choice of tools and methods for HC calculation depends on the data available and the type of study that is to be performed
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