35 research outputs found
Convex Relaxations of Probabilistic AC Optimal Power Flow for Interconnected AC and HVDC Grids
High Voltage Direct Current (HVDC) systems interconnect AC grids to increase
reliability, connect offshore wind generation, and enable coupling of
electricity markets. Considering the growing uncertainty in power infeed and
the complexity introduced by additional controls, robust decision support tools
are necessary. This paper proposes a chance constrained AC-OPF for AC and HVDC
grids, which considers wind uncertainty, fully utilizes HVDC control
capabilities, and uses the semidefinite relaxation of the AC-OPF. We consider a
joint chance constraint for both AC and HVDC systems, we introduce a piecewise
affine approximation to achieve tractability of the chance constraint, and we
allow corrective control policies for HVDC converters and generators to be
determined. An active loss penalty term in the objective function and a
systematic procedure to choose the penalty weights allow us to obtain
AC-feasible solutions. We introduce Benders decomposition to maintain
scalability. Using realistic forecast data, we demonstrate our approach on a
53-bus and a 214-bus AC-DC system, obtaining tight near-global optimality
guarantees. With a Monte Carlo analysis, we show that a chance constrained
DC-OPF leads to violations, whereas our proposed approach complies with the
joint chance constraint
Chance-Constrained AC Optimal Power Flow Integrating HVDC Lines and Controllability
The integration of large-scale renewable generation has major implications on
the operation of power systems, two of which we address in this work. First,
system operators have to deal with higher degrees of uncertainty due to
forecast errors and variability in renewable energy production. Second, with
abundant potential of renewable generation in remote locations, there is an
increasing interest in the use of High Voltage Direct Current lines (HVDC) to
increase transmission capacity. These HVDC transmission lines and the
flexibility and controllability they offer must be incorporated effectively and
safely into the system. In this work, we introduce an optimization tool that
addresses both challenges by incorporating the full AC power flow equations,
chance constraints to address the uncertainty of renewable infeed, modelling of
point-to-point HVDC lines, and optimized corrective control policies to model
the generator and HVDC response to uncertainty. The main contributions are
twofold. First, we introduce a HVDC line model and the corresponding HVDC
participation factors in a chance-constrained AC-OPF framework. Second, we
modify an existing algorithm for solving the chance-constrained AC-OPF to allow
for optimization of the generation and HVDC participation factors. Using
realistic wind forecast data, for 10 and IEEE 39 bus systems with HVDC lines
and wind farms, we show that our proposed OPF formulation achieves good in- and
out-of-sample performance whereas not considering uncertainty leads to high
constraint violation probabilities. In addition, we find that optimizing the
participation factors reduces the cost of uncertainty significantly
Load Flow Solution of Distribution Systems - A Bibliometric Survey
In this paper, Bibliometric Survey has been carried out on ‘Load Flow Solution of Distribution Systems’ from 2012 to 2021. Scopus database has been used for the analysis. There were total 1711 documents found on this topic. The statistical analysis is carried out source wise, year wise, area wise, Country wise, University wise, author wise, and based on funding agency. Network analysis is also carried out based on Co-authorship, Co-occurrence. Results are presented. During 2020 and 2018, there were 263 documents published which is the highest. ‘IEEE Transactions on Power Systems’ has published 90 documents during the period of study which is the highest in terms of articles under the category of sources. Highest citations were received by the article authored by Hung and Mithulanathan with 484 citations in the collected database with the chosen key words. VOSviewer 1.6.16 is the software that is used for the statistical analysis and network analysis on the database. It provides a very effective way to analyze the co-authorship, co-occurrences, citation and bibliometric analysis etc. The Source for all Tables and figures is www.scopus.com, The data is assessed on 6th July, 2021
Flexible Transmission: A Comprehensive Review of Concepts, Technologies, and Market
As global concerns regarding climate change are increasing worldwide, the
transition towards clean energy sources has accelerated. Accounting for a large
share of energy consumption, the electricity sector is experiencing a
significant shift towards renewable energy sources. To accommodate this rapid
shift, the transmission system requires major upgrades. Although enhancing grid
capacity through transmission system expansion is always a solution, this
solution is very costly and requires a protracted permitting process. The
concept of flexible transmission encompasses a broad range of technologies and
market tools that enable effective reconfiguration and manipulation of the
power grid for leveraged dispatch of renewable energy resources. The
proliferation of such technologies allows for enhanced transfer capability over
the current transmission network, thus reducing the need for grid expansion
projects. This paper comprehensively reviews flexible transmission technologies
and their role in achieving a net-zero carbon emission grid vision. Flexible
transmission definitions from different viewpoints are discussed, and
mathematical measures to quantify grid flexibility are reviewed. An extensive
range of technologies enhancing flexibility across the grid is introduced and
explored in detail. The environmental impacts of flexible transmission,
including renewable energy utilization and carbon emission reduction, are
presented. Finally, market models required for creating proper incentives for
the deployment of flexible transmission and regulatory barriers and challenges
are discussed