3,835 research outputs found
Congestion and Price Prediction in Locational Marginal Pricing Markets Considering Load Variation and Uncertainty
This work investigates the prediction of electricity price and power transmission network congestions under load variation and uncertainty in deregulated power systems. The study is carried out in three stages.
In the first stage, the mathematical programming models, which produce the generation dispatch solution, the Locational Marginal Price (LMP), and the system statuses such as transmission congestions, are reviewed. These models are often referred to as Optimal Power Flow (OPF) models, and can be categorized into two major groups: Alternating Current OPF (ACOPF) and Direct Current OPF (DCOPF). Due to the convergence issue with the ACOPF model and the concern of inaccuracy with the DCOPF model, a new DCOPF-based algorithm is proposed, using a fictitious nodal demand (FND) model to represent power losses at each individual line. This is an improvement over the previous work that assigns losses to a few user-defined buses, and is capable of achieving a better tradeoff between computational effectiveness and the accuracy of the results.
In the second stage, the solution features are explored for each of the three OPF models to predict critical load levels where a step change of LMP occurs due to the change of binding constraints. After careful examinations of the mathematical relationship of the OPF solutions, nodal prices, and congestions, with respect to load variation, simplex-like method, quadratic interpolation method, and variable substitution method are proposed for each of the three OPF models respectively in order to predict price changes and system congestion.
In the last stage, the probabilistic feature of the forecasted LMP is investigated. Due to the step change characteristic of the LMP and uncertainty in load forecasting, the forecasted LMP represents only a certain possibility in a lossless DCOPF framework. Additional possible LMP values exist, other than the deterministically forecasted LMP. Therefore, the concept of Probabilistic LMP is introduced and a systematic approach to quantify the probability of the forecasted LMP, with respect to load variation, is proposed. Similar concepts and methodology have been applied to the ACOPF and FND-based DCOPF frameworks, which can be useful for power market participants in making financial decisions
Study of the quasi-two-body decays B^{0}_{s} \rightarrow \psi(3770)(\psi(3686))\pi^+\pi^- with perturbative QCD approach
In this note, we study the contributions from the S-wave resonances,
f_{0}(980) and f_{0}(1500), to the B^{0}_{s}\rightarrow \psi(3770)\pi^
{+}\pi^{-} decay by introducing the S-wave \pi\pi distribution amplitudes
within the framework of the perturbative QCD approach. Both resonant and
nonresonant contributions are contained in the scalar form factor in the S-wave
distribution amplitude \Phi^S_{\pi\pi}. Since the vector charmonium meson
\psi(3770) is a S-D wave mixed state, we calculated the branching ratios of
S-wave and D-wave respectively, and the results indicate that f_{0}(980) is the
main contribution of the considered decay, and the branching ratio of the
\psi(2S) mode is in good agreement with the experimental data. We also take the
S-D mixed effect into the B^{0}_{s}\rightarrow \psi(3686)\pi^ {+}\pi^{-} decay.
Our calculations show that the branching ratio of B^{0}_{s}\rightarrow
\psi(3770)(\psi(3686))\pi^ {+}\pi^{-} can be at the order of 10^{-5}, which can
be tested by the running LHC-b experiments.Comment: 10 pages, 3 figure
Robust Matrix Completion State Estimation in Distribution Systems
Due to the insufficient measurements in the distribution system state
estimation (DSSE), full observability and redundant measurements are difficult
to achieve without using the pseudo measurements. The matrix completion state
estimation (MCSE) combines the matrix completion and power system model to
estimate voltage by exploring the low-rank characteristics of the matrix. This
paper proposes a robust matrix completion state estimation (RMCSE) to estimate
the voltage in a distribution system under a low-observability condition.
Tradition state estimation weighted least squares (WLS) method requires full
observability to calculate the states and needs redundant measurements to
proceed a bad data detection. The proposed method improves the robustness of
the MCSE to bad data by minimizing the rank of the matrix and measurements
residual with different weights. It can estimate the system state in a
low-observability system and has robust estimates without the bad data
detection process in the face of multiple bad data. The method is numerically
evaluated on the IEEE 33-node radial distribution system. The estimation
performance and robustness of RMCSE are compared with the WLS with the largest
normalized residual bad data identification (WLS-LNR), and the MCSE
Fast Low-rank Representation based Spatial Pyramid Matching for Image Classification
Spatial Pyramid Matching (SPM) and its variants have achieved a lot of
success in image classification. The main difference among them is their
encoding schemes. For example, ScSPM incorporates Sparse Code (SC) instead of
Vector Quantization (VQ) into the framework of SPM. Although the methods
achieve a higher recognition rate than the traditional SPM, they consume more
time to encode the local descriptors extracted from the image. In this paper,
we propose using Low Rank Representation (LRR) to encode the descriptors under
the framework of SPM. Different from SC, LRR considers the group effect among
data points instead of sparsity. Benefiting from this property, the proposed
method (i.e., LrrSPM) can offer a better performance. To further improve the
generalizability and robustness, we reformulate the rank-minimization problem
as a truncated projection problem. Extensive experimental studies show that
LrrSPM is more efficient than its counterparts (e.g., ScSPM) while achieving
competitive recognition rates on nine image data sets.Comment: accepted into knowledge based systems, 201
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