System frequency must be kept very close to its nominal range to ensure the stability of an electric power grid.Excessive system frequency variations are able to result in load shedding,frequency instability,and even ...System frequency must be kept very close to its nominal range to ensure the stability of an electric power grid.Excessive system frequency variations are able to result in load shedding,frequency instability,and even generator damage.With increasing wind power penetration,there is rising concern about the reduction in inertia response and primary frequency control in the electric power grid.Converter-based wind generation is capable of providing inertia response and primary frequency response;nevertheless,the primary frequency and inertia responses of wind generation are different from those of conventional synchronous fleets;it is not completely understood how the primary frequency and inertia responses affect the given system under various disturbances and available kinetic energy levels.Simulations are used to investigate the influences of inertia and droop control strategies on the dynamic frequency responses,particularly the index of the second frequency drop under various disturbance and wind conditions.A quantitative analysis provides insight into setting of inertia and droop control coefficients for various wind and disturbance conditions to facilitate adequate dynamic frequency responses during frequency events.展开更多
Wearing masks is an easy way to operate and popular measure for preventing epidemics.Although masks can slow down the spread of viruses,their efficacy in gathering environments involving heterogeneous person-to-person...Wearing masks is an easy way to operate and popular measure for preventing epidemics.Although masks can slow down the spread of viruses,their efficacy in gathering environments involving heterogeneous person-to-person contacts remains unknown.Therefore,we aim to investigate the epidemic prevention effect of masks in different real-life gathering environments.This study uses four real interpersonal contact datasets to construct four empirical networks to represent four gathering environments.The transmission of COVID-19 is simulated using the Monte Carlo simulation method.The heterogeneity of individuals can cause mask efficacy in a specific gathering environment to be different from the baseline efficacy in general society.Furthermore,the heterogeneity of gathering environments causes the epidemic prevention effect of masks to differ.Wearing masks can greatly reduce the probability of clustered epidemics and the infection scale in primary schools,high schools,and hospitals.However,the use of masks alone in primary schools and hospitals cannot control outbreaks.In high schools with social distancing between classes and in workplaces where the interpersonal contact is relatively sparse,masks can meet the need for prevention.Given the heterogeneity of individual behavior,if individuals who are more active in terms of interpersonal contact are prioritized for mask-wearing,the epidemic prevention effect of masks can be improved.Finally,asymptomatic infection has varying effects on the prevention effect of masks in different environments.The effect can be weakened or eliminated by increasing the usage rate of masks in high schools and workplaces.However,the effect on primary schools and hospitals cannot be weakened.This study contributes to the accurate evaluation of mask efficacy in various gathering environments to provide scientific guidance for epidemic prevention.展开更多
基金This work was supported by the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(20KJB470026)Key Project of Smart Grid Technology and Equipment of National Key Research and Development Plan of China(2016YFB0900601).
文摘System frequency must be kept very close to its nominal range to ensure the stability of an electric power grid.Excessive system frequency variations are able to result in load shedding,frequency instability,and even generator damage.With increasing wind power penetration,there is rising concern about the reduction in inertia response and primary frequency control in the electric power grid.Converter-based wind generation is capable of providing inertia response and primary frequency response;nevertheless,the primary frequency and inertia responses of wind generation are different from those of conventional synchronous fleets;it is not completely understood how the primary frequency and inertia responses affect the given system under various disturbances and available kinetic energy levels.Simulations are used to investigate the influences of inertia and droop control strategies on the dynamic frequency responses,particularly the index of the second frequency drop under various disturbance and wind conditions.A quantitative analysis provides insight into setting of inertia and droop control coefficients for various wind and disturbance conditions to facilitate adequate dynamic frequency responses during frequency events.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.62173065,11875005,61976025,and 11975025)the University Synergy Innovation Program of Anhui Province(Grant No.GXXT-2021-032)+1 种基金the Natural Science Foundation of Liaoning Province(Grant No.2020-MZLH-22)Major Project of the National Social Science Fund of China(Grant No.19ZDA324).
文摘Wearing masks is an easy way to operate and popular measure for preventing epidemics.Although masks can slow down the spread of viruses,their efficacy in gathering environments involving heterogeneous person-to-person contacts remains unknown.Therefore,we aim to investigate the epidemic prevention effect of masks in different real-life gathering environments.This study uses four real interpersonal contact datasets to construct four empirical networks to represent four gathering environments.The transmission of COVID-19 is simulated using the Monte Carlo simulation method.The heterogeneity of individuals can cause mask efficacy in a specific gathering environment to be different from the baseline efficacy in general society.Furthermore,the heterogeneity of gathering environments causes the epidemic prevention effect of masks to differ.Wearing masks can greatly reduce the probability of clustered epidemics and the infection scale in primary schools,high schools,and hospitals.However,the use of masks alone in primary schools and hospitals cannot control outbreaks.In high schools with social distancing between classes and in workplaces where the interpersonal contact is relatively sparse,masks can meet the need for prevention.Given the heterogeneity of individual behavior,if individuals who are more active in terms of interpersonal contact are prioritized for mask-wearing,the epidemic prevention effect of masks can be improved.Finally,asymptomatic infection has varying effects on the prevention effect of masks in different environments.The effect can be weakened or eliminated by increasing the usage rate of masks in high schools and workplaces.However,the effect on primary schools and hospitals cannot be weakened.This study contributes to the accurate evaluation of mask efficacy in various gathering environments to provide scientific guidance for epidemic prevention.
