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With the frequent occurrence of electromechanical oscillation in the power systems, the fast response characteristics of the photovoltaic (PV) power generation system are used to actively damp the electromechanical oscillation in the power system. The proportion and position of PV generations in the system are usually different, therefore, the dynamic process of PV damping the grid electromechanical oscillation will also be changed. This paper divides the conventional system into two parts: the power system and the infinite power grid, the steady-state output of the PV generation system is equivalent to the active output current Id0 and the reactive output current Iq0. The analysis conclusions of these two parts shows that: the inertia level, synchronization and damping effect of the conventional system will increase with the increase of Id0, and first decrease with the increase of Iq0, then increase rapidly, and then decrease. Moreover, the closer the PV module to the electromechanical oscillation source, the better the oscillation damping effect. Finally, this paper verifies the conclusion correctness through MATLAB/Simulink.

Technological enterprises can create employment opportunities, provide quality services and have broad space for development, but there are also operational problems, capital problems, manpower problems and market problems. Among them, the biggest obstacle is credit. The existing credit evaluation mainly focuses on economic indicators and credit risk focuses on repayment risk. Scholars lack in deep empirical research on influencing factors of credit and credit risk research from the perspective of agreement fulfillment willingness once this is very scarce. Combining the characteristics of previous research object and previous scholars' research, this thesis introduces enterprise quality as an independent variable to explore its impact on credit risk. Enterprise quality refers to the function produced by the collection of various elements within a technology-based enterprise, mainly including enterprise management quality and enterprise innovation quality. The agreement fulfillment willingness is introduced as an antecedent variable of credit risk. In this thesis, agreement fulfillment willingness refers to the subjective aspect of credit awareness of technology-based enterprises' agreement fulfillment, including but not limited to providing quality products, providing real information, fulfilling social responsibilities and repaying debt on time. In addition, the enterprise policy, competitive environment and managerial quality are introduced as regulatory variables to analyze the regulatory role of enterprise policy and competitive environment in the relationship between enterprise quality and agreement fulfillment willingness and the regulatory role of enterprise managerial quality in the relationship between agreement fulfillment willingness and credit risk. Then, we draw on the classic scales studied by previous researchers to design, improve, issue and recall questionnaires, analyze the data collected and draw relevant empirical results. Results show that the enterprise quality positively affects the agreement fulfillment willingness; the agreement fulfillment willingness negatively affects credit risk; the enterprise has a significant positive regulatory effect in the relationship between the enterprise quality and the agreement fulfillment willingness; the competitive environment has a significant negative regulatory effect in the relationship between the enterprise quality and agreement fulfillment willingness, the enterprise manager quality has a positive regulatory effect in the relationship between agreement fulfillment willingness and the credit risk. As empresas tecnológicas podem criar oportunidades de emprego, fornecer serviços de qualidade e ter amplo espaço para o desenvolvimento, mas também podem ter problemas operacionais, de capital, de mão-de-obra e de mercado. Entre estes, o maior obstáculo é o crédito. A avaliação de crédito concentra-se principalmente em indicadores económicos e o risco de crédito concentra-se no risco de reembolso. A comunidade académica necessita de investigação empírica robusta sobre os fatores que influenciam o crédito e o risco de crédito na perspetiva da disposição para o cumprimento de contratos, uma vez que esta é muito rara. Combinando as características da investigação anterior de outros investigadores, esta tese introduz a qualidade da empresa como uma variável independente para explorar o seu impacto no risco de crédito. A qualidade da empresa respeita à função obtida pela recolha de vários elementos de uma empresa de base tecnológica, incluindo principalmente a qualidade da gestão e a qualidade da inovação. A disposição para cumprimento do contrato é introduzida como uma variável antecedente do risco de crédito. Nesta tese, a disposição para cumprimento de contratos refere-se aos aspetos subjetivos da consciência do cumprimento de contratos nas empresas de base tecnológica, incluindo, mas não apenas, o fornecimento de produtos de qualidade, o fornecimento de informações credíveis, o cumprimento de responsabilidades sociais e o pagamento atempado da dívida. Além disso, a política da empresa, o ambiente concorrencial e a qualidade da gestão são introduzidos como variáveis reguladoras para analisar o papel regulador da política da empresa e do ambiente concorrencial na relação entre a qualidade da empresa e a vontade de cumprimento do contrato e o papel regulador da qualidade da gestão na relação entre a disposição para cumprimento de contratos e risco de crédito. Em seguida, com base nas escalas clássicas usadas por investigadores anteriores, projetamos, aprimoramos, emitimos e recolhemos questionários, analisámos os dados recolhidos e obtivemos resultados empíricos relevantes. Os resultados mostram que a qualidade da empresa afeta positivamente a vontade de cumprimento do contrato, que a disposição para cumprir os contratos afeta negativamente o risco de crédito, que a empresa tem um significativo efeito regulador positivo na relação entre a qualidade da empresa e a vontade de cumprir o contrato, que o ambiente concorrencial tem um significativo efeito regulador negativo na relação entre a qualidade da empresa e a vontade de cumprimento do contrato e que a qualidade da gestão tem um efeito regulador positivo na relação entre a disposição de cumprimento do contrato e o risco de crédito.

This paper studies the cooperative absorption mechanism of wind-photovoltaic power generation and electric vehicle interconnection. Markov decision process is used to model the two random events of wind-photovoltaic generation and electric vehicle charging and discharging. Based on this, a multi-objective bilevel optimal charging and discharging scheduling model is proposed for the interconnection of wind-photovoltaic generation and electric vehicle based on cluster. The upper dispatching agency considers the consumption of wind-photovoltaic power generation and the economy of grid side operation, and EV group institution takes charge-discharge fees with battery internal losses into account. When solving the problem, making full use of the correlation between the structural features and variables between the upper and lower layers, the basic strategy of information exchange between the upper and lower layers is constructed, and based on the hierarchical features and future situation simulation, the double-layer optimal scheduling strategy is obtained. Finally, the effectiveness of the proposed optimization strategy is simulated and analyzed in IEEE 30 nodes system.

To quantify the oxygen content in molten salts, we examined the performance of an yttria-stabilized zirconia solid electrolyte oxygen sensor with a Bi/Bi2O3 reference electrode, focusing on its output accuracy. When the above sensor was tested in a flow of gas with known oxygen partial pressure, $$p_{O_2}$$ , a linear relationship between $$lgp_{O_2}$$ and the electromotive force (EMF) was observed, and the correlation slope exhibited a positive deviation from Nernstian behavior. EMF measurements performed in molten NaCl–KCl indicated that the oxygen content of this salt mixture increased with increasing oxygen partial pressure in the covering gas, in agreement with Henry’s law. Moreover, the EMF exhibited a linear decrease with increasing melt temperature of molten NaCl–KCl, in agreement with the theoretical model. Finally, a relationship between the structure of molten NaCl–KCl and its oxygen diffusion behavior was established. As a result, the developed sensor was demonstrated to be well suited for determining the oxygen content of molten salts.

Thioglycolic acid (TGA)-coated colloidal Ag2S quantum dots (QDs) emitting in the near-infrared (NIR) region upon excitation by an 808 nm diode laser were synthesized. The observed photoluminescence (PL) was attributed to the presence of ligand-modified Ag2S on the QD surfaces and could be easily controlled by a simple dilution process due to the concentration-dependent surface structure of the colloidal QDs. Upon dilution of the solution, the PL intensity initially increased before later decreasing, with a blueshift being observed in the PL spectra. These phenomena can be accounted for by the aggregation of QDs due to a decrease in the content of ligand-modified Ag2S on the QD surfaces upon dilution, which in turn affected the fluorescence resonance energy transfer (FRET), and re-emission of the surface energy level.

Ag2S quantum dots (QDs) coated with thioglycolic acid (Ag2S QDs-TGA) have been synthesized in an organic solvent via a stepwise addition of reagents. When excited by a 980 nm laser, the near-infrared-emitting colloidal Ag2S QDs-TGA exhibit upconversion luminescence (UCL). The observed photoluminescence (PL) was attributed to the presence of ligand-modified Ag2S on the QD surfaces. Hence, upon dilution of the solution, the PL intensity initially increased before subsequently decreasing, accompanied by a blue shift in the PL spectra. The PL phenomena can be attributed to the increase in the amount of ligand-modified Ag2S on the QD surfaces upon dilution, which in turn affected the fluorescence resonance energy transfer (FRET) and re-emission of the surface energy level. The relations between the emission intensity of Ag2S QDs-TGA and the excitation power are investigated, and the results confirm that the UCL in Ag2S QDs-TGA can be ascribed to a two-photon-assisted absorption process via a real energy state.

It is an important part for the power system operation risk control to identify the critical lines. Fluctuation of wind power and fluctuation of load will have a great influence on power transmission and distribution, which will lead to the change of critical lines. Based on probabilistic load flow (PLF) analysis, the risk theory is introduced to put forward, and probabilistic flow betweenness considering uncertainty of wind power and load is presented for critical line identification, which reflects the influence of power grid structure characteristics, change of system running state and uncertain factors on power transmission. It can identify critical lines more accurately. Simulation calculation on CEPRI-36 bus system integrated with wind farms and IEEE-39 bus system with wind farms verify effectiveness of this method. It is able to search for the critical lines according to system running state in actual application, so as to adopt security control measures for the system.

The optimal charge and discharge schedule of EVs is studied under distribution network considerring wind power. Markov decision process is adopted to model the randomness of supply and demand. Two-level scheduling model of electric vehicles with electric vehicle agents are adopted. The electric vehicle agents are responsible for collecting the real-time charging-discharging demand of electric vehicles in the region and reported to the upper dispatching center. The goal of the upper dispatching center considers the power losses in the distribution network, load variance and the matching degree between EV charging-discharging and wind energy. The goal of the lower agent considers the EV charging-discharging fees and EV charging battery losss costs. When deciding the optimal charging strategy, two-level Rollout methodis adopted considering the the effects on future decisions by the current decisions. Finally, the optimal results under four different strategies are simulated on the IEEE 30 nodes distribution network system.

Voltage is one of the measurement standard of power quality. The issue of low voltage in distribution network seriously affect the social economic development and people's life. Consequently, it would optimize low voltage investment program, clear direction of low voltage investment and provide decision support for the management of low voltage. Canopy- Kmeans is one of the widely used classical partition clustering algorithm. Support vector machine is a kind of sorting algorithms that could take full advantage of limited learning sample to acquire generalization. Both Canopy-Kmeans and Support Vector Machine have better behavior and precision rate. However, the runtime and RAM would be the bottleneck in the case of large amount of data. The application of data mining algorithm based on big data is particularly important. This paper take advantage of distributed Kmeans and SVM algorithm to realize diagnosis model of cause of low voltage based on big data platform of Hadoop. Experiments have shown that this method has a higher accuracy and reliability compared to traditional Kmeans and SVM algorithm.

With the increasing voltage class of power equipment, the turn number of winding equipment becomes more great and the coupling between the turns becomes stronger. As a result, it is difficult to solve circuit equation by analytical algorithm. This paper provides a method using waveform relaxation (WR) to solve the circuit equation. This method could be applied in calculation of complex computation, such as turn- to-turn voltage calculation of winding equipment and flow calculation of big power grid. Before calculation, this paper provide a method to calculate electromagnetic parameters of an air-core reactor. At last the paper presents a calculating example and experiment. From the experiment, the method provided in this paper proves its veracity and superiority.

Accurately mastering the capability of wind power accommodation is conducive to construction planning of wind plant and provide auxiliary to dispatching decision in actual operation. Based on deep analysis of key factors influencing accommodation capability of wind power basic idea and method were proposed to manoeuvre wide and flexible adequacy resources involved in system regulation. Comprehensively considering technical characteristics of various power generations and such constrains as the balance of power and thermal loads and transfer capacity and taking the maximum accommodation capability of new energy as objective function, a model is built to analyze new energy accommodation capacity of power grid. Taking shanxi province in China, which is rich in new energy resources, as calculation example, the changes of new energy accommodation capability were simulated and analyzed under different scenes of introducing in different flexible resources.