An Improved UFLS Scheme based on Estimated Minimum Frequency and Power Deficit

In the event of a power system disturbance, it is important that the decision to implement under frequency load shedding is based on both the minimum frequency and the magnitude of the disturbance. In this paper, we propose the use of higher order polynomial curve fitting to estimate the minimum frequency. If the prediction shows that the minimum frequency threshold will be violated, the magnitude of the total disturbance is estimated using the swing equation. In addition, the minimum amount of load that must be shed to restore the frequency just above the minimum value can also be directly calculated. Simulations are carried out for the considered Taiwan power system and the results prove the efficiency of the proposed technique

The 2G allele of promoter region of Matrix metalloproteinase-1 as an essential pre-condition for the early onset of oral squamous cell carcinoma

<p>Abstract</p> <p>Background</p> <p>Matrix metalloproteinase (<it>MMP</it>) is known to be involved in the initial and progressive stages of cancer development, and in the aggressive phenotypes of cancer. This study examines the association of single nucleotide polymorphisms in promoter regions of <it>MMP-1 </it>and <it>MMP-3 </it>with susceptibility to oral squamous cell carcinoma (OSCC).</p> <p>Methods</p> <p>We compared 170 Japanese OSCC cases and 164 healthy controls for genotypes of <it>MMP-1 </it>and <it>MMP-3</it>.</p> <p>Results</p> <p>The frequency of the <it>MMP-1 </it>2G allele was higher and that of the 1G homozygote was lower in the OSCC cases (<it>p </it>= 0.034). A multivariate logistic regression analysis revealed that subjects who were 45 years old or older had a significantly increased (2.47-fold) risk of OSCC (95%CI 1.47–4.14, <it>p </it>= 0.0006), and those carrying the <it>MMP-1 </it>2G allele had a 2.30-fold risk (95%CI 1.15–4.58, <it>p </it>= 0.018), indicating independent involvement of these factors in OSCC. One of the key discoveries of this research is the apparent reduction of the <it>MMP-1 </it>1G/1G and 1G/2G genotype distributions among the early onset OSCC cases under the ages of 45 years. It should be noted that the tongue was the primary site in 86.2% of these early onset cases. This could suggest the specific carcinogenic mechanisms, i.e. specific carcinogenic stimulations and/or genetic factors in the tongue.</p> <p>Conclusion</p> <p>Since the 2G allele is a majority of the <it>MMP-1 </it>genotype in the general population, it seems to act as a genetic pre-condition in OSCC development. However this report suggests a crucial impact of the <it>MMP-1 </it>2G allele in the early onset OSCC.</p

A Novel Unknown Input Observer-Based Optimal Load Frequency Control for Smart Power Systems Considering EV and DR Participation

A new decentralized load frequency control (LFC) scheme based on the concept of dynamic state estimation is proposed in this paper. The suggested novel, scheme makes use of an efficient deterministic state estimator, known as unknown input observe (UIO) utilized in each area-control for online observing of the dynamic states of the system. To achieve a decentralized approach, the demand and transferred power among areas are considered as unknown inputs to the power system operators. Then, the optimal control theory is adopted to control the frequency deviation in each area which is designed based on the observed dynamic states. An interconnected power system with four-areas is used to verify the applicability of the proposed scheme, while the robustness, accuracy, and superiority of the proposed method is shown by several comparisons with other methods recently published in literature

Evaluating the Operational Flexibility of Generation Mixture with an Innovative Techno-Economic Measure

This paper aims at providing a novel techno-economic flexibility index to quantify the relative flexibility of different conventional generation technologies. The proposed measure takes into account a comprehensive set of technical flexibility characteristics of generation units including minimum stable generation level, operating range, minimum up/down times and ramp up/down capability. The impact of various technical parameters on the flexibility restriction is determined based on the additional costs imposed to the system operator in order to satisfy that constraint. Afterward, the calculated flexibility index is incorporated into day-ahead market clearing procedure as a new objective function beside operation cost using a multi-objective decision-making approach. Simulation results show that the need of different flexibility levels changes the optimal generation dispatch and results in different operation costs. Furthermore, the impact of two emerging flexible options i.e., bulk energy storages and a typical demand response program in the flexibility contribution of other generation technologies is also investigated. The results reveal that the integration of emerging flexible options frequently changes the flexibility share of conventional units and can provide the required flexibility level at a lower cost

Frequency response models and control in smart power systems with high penetration of renewable energy sources

The high penetration of renewable energy sources in modern power systems introduces opportunities and challenges to power system operators. The frequency, which is a global variable in power systems, is being affected due to the increase of the renewable energy shares. This paper suggests dynamic models of power systems for assessing the frequency response due to different types of disturbances and uncertainties from renewable energy sources. The introduced model is built based on the sub-transient model of synchronous generating units. Likewise, a simplified system frequency response model is presented, in which the demand-side participation in providing ancillary services is considered. Different types of power systems are considered to verify the introduced models. The results show the effectiveness of the presented models in evaluating the impact of different parameters on power system frequency response. The impacts of increasing the renewable energy shares and its uncertainties are also investigated