Improvement of Fault Current Calculation and Static Security Risk for Droop Control of the Inverter-Interfaced DG of Grid-Connected and Isolated Microgrids

The contribution current of an inverter-interfaced distributed generator unit during a fault is one of the significant challenges for two modes: grid-connected and isolated AC microgrid. For this challenge, this article is aimed to study two methods of fault current calculation for two modes: grid-connected and isolated microgrids. These methods include a virtual equivalent impedance and a proposed method. The proposed method is a new technique for calculating the fault current contribution depending on the droop control of inverter-interfaced DG. The proposed method can control the contribution short-circuit current of DG within its limit (2 p.u.) where it is dependent on the voltage value of the DG bus to calculate the short circuit current of DG by using the control criterion. Static security risk and load shedding are calculated after fault clearance using an operation scenario in which the distribution system will be divided into small subsystems and is then gridconnected and isolated due to the removal of the faulted bus by protection devices. The proposed technique is applied to a standard IEEE 33-bus distribution network with five DGs. The results show that the contribution current of inverter-interfaced DG during the fault has more effects than the fault current of the nearest faulted bus to the DG bus. The proposed technique improves the calculated fault current value by about 30% for the grid-connected microgrid and by about 50% for the isolated microgrid from its value of the virtual impedance method. The static security risk is improved after load shedding. The static security risk improved by about 0.025%. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Đại Học Lạc Hồng; Ministry of Higher Education, Egypt, MHEFunding: The study presented in this paper is funded in part by the Ministry of Higher Education in Egypt and in part by the Lac Hong University in Vietnam

Proučavanje relativističke tvorbe hadrona prema naprijed i unatrag u sudarima 3he i 4he s jezgrama u emulziji na energiji ubrzivača u dubni

The experimental results on 3He- and 4He-emulsion interactions accompanied by relativistic (shower) hadrons flying into the backward (θlab ≤ 90◦ ) hemisphere at 4.5 AGeV/c are presented and analyzed. The dependence of the probabilities of these interactions on the different target sizes, impact parameter and projectile spectator charges is studied. An investigation of average values and multiplicity distributions of these hadrons for the interactions with light and heavy emulsion nuclei has been carried out. In addition, the correlations between the multiplicities of different types of the emitted particles are studied. The data show that backward shower particles are a sensitive target parameter. The values of impact parameters can be used as good indicators for selecting events which occured with light or heavy emulsion nuclei. A comparison with the modified cascade model shows a good performance in describing the data produced in the region having less cascading (i.e. interactions with light nuclei). As for the interactions with heavy nuclei, the model overestimates the experimental data.Predstavljamo eksperimentalne rezultate i analize mjerenja međudjelovanja 3He i 4He u emulziji na 4.5 AGeV/c, u kojima se opažaju relativistički pljuskovi hadrona koji lete unatrag (θlab ≤ 90◦ ). Proučavamo ovisnost vjerojatnosti tih međudjelovanja o veličini jezgre mete, sudarnom parametru i naboju projektila-promatrača. Istražili smo prosječne vrijednosti i raspodjele višestrukosti hadrona za lake i teške jezgre u emulziji. Nadalje, proučavali smo korelacije višestrukosti različitih izlaznih čestica. Podaci pokazuju da su pljuskovi čestica unatrag osjetljiv parametar jezgri mete. Vrijednosti parametara mogu poslužiti kao dobar pokazatelj sudara s lakim odnosno teškim jezgrama. Usporedba s promijenjenim kaskadnim modelom pokazuje dobro slaganje s podacima u kojima je manje kaskada (tj. Manje sudara s lakim jezgrama). Rezultati tog modela za teške jezgre veći su od eksperimentalnih podataka

Proučavanje relativističke tvorbe hadrona prema naprijed i unatrag u sudarima 3he i 4he s jezgrama u emulziji na energiji ubrzivača u dubni

The experimental results on 3He- and 4He-emulsion interactions accompanied by relativistic (shower) hadrons flying into the backward (θlab ≤ 90◦ ) hemisphere at 4.5 AGeV/c are presented and analyzed. The dependence of the probabilities of these interactions on the different target sizes, impact parameter and projectile spectator charges is studied. An investigation of average values and multiplicity distributions of these hadrons for the interactions with light and heavy emulsion nuclei has been carried out. In addition, the correlations between the multiplicities of different types of the emitted particles are studied. The data show that backward shower particles are a sensitive target parameter. The values of impact parameters can be used as good indicators for selecting events which occured with light or heavy emulsion nuclei. A comparison with the modified cascade model shows a good performance in describing the data produced in the region having less cascading (i.e. interactions with light nuclei). As for the interactions with heavy nuclei, the model overestimates the experimental data.Predstavljamo eksperimentalne rezultate i analize mjerenja međudjelovanja 3He i 4He u emulziji na 4.5 AGeV/c, u kojima se opažaju relativistički pljuskovi hadrona koji lete unatrag (θlab ≤ 90◦ ). Proučavamo ovisnost vjerojatnosti tih međudjelovanja o veličini jezgre mete, sudarnom parametru i naboju projektila-promatrača. Istražili smo prosječne vrijednosti i raspodjele višestrukosti hadrona za lake i teške jezgre u emulziji. Nadalje, proučavali smo korelacije višestrukosti različitih izlaznih čestica. Podaci pokazuju da su pljuskovi čestica unatrag osjetljiv parametar jezgri mete. Vrijednosti parametara mogu poslužiti kao dobar pokazatelj sudara s lakim odnosno teškim jezgrama. Usporedba s promijenjenim kaskadnim modelom pokazuje dobro slaganje s podacima u kojima je manje kaskada (tj. Manje sudara s lakim jezgrama). Rezultati tog modela za teške jezgre veći su od eksperimentalnih podataka

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

Backward slow protons production in the inelastic interactions of 6^{\bf 6}Li and 7^{\bf 7}Li nuclei with emulsion nuclei at Dubna energy

We report the experimental measurements on the multiplicity of slow target associated particles, in the forward ($\theta_{lab} \le 90^{\circ}$) and backward ($\theta_{lab} > 90^{\circ}$) hemispheres, and the different correlations between the backward slow protons and the production of hadrons in both hemispheres in the interactions of $^{6}Li($3.7 A GeV) and $^{7}Li($2.2 A GeV) with emulsion nuclei. The study of the number of backward slow protons ($N^{b}_{b}$ and $N^{b}_{g}$) indicates that while the number of backward black particles, $N^{b}_{b}$, is a good factor representing the purely target fragments, the number of backward grey particles, $N^{b}_{g}$, can be considered as an accurate experimental factor for the impact parameter dependence of the collision. It is also shown that the most central collisions are events having $N^{b}_{g}>0$ and $N^{b}_{s}>0$. We confront the data with a multiple scattering model incorporating both binary cascading and evaporation of residual nucleus. The model applies well in the region of limited cascading (backward hemisphere). As for the forward hemisphere, where cascading becomes more branched, the model becomes less applicable

Central events in the interactions of 28Si\bf{^{28}Si} and 32S\bf{^{32}S} with heavy emulsion targets

Data on the multiplicity of secondaries in central events of $\mathsf{^{28}Si}$ (14.6 AGeV) and $\mathsf{^{32}S}$ (3.7 AGeV) interactions with AgBr emulsion nuclei have been compiled and studied. The dependence of the multiplicities of the outgoing charged stripping particles on the number of interacting nucleons and therefore on the impact parameter, as indicated by the target size, and consequently, on the degree of centrality is investigated. The resultant multiplicity distribution of the produced pions for each studied case is fitted by both Negative Binomial (NB) and Poisson distributions. The NB distribution is valid for most of the considered cases. The transparency of the target for a projectile was found to become more pronounced as the incident energy increased