The contamination and accumulation of microplastics(MPs)in mangrove ecosystems have become an increasing concern due to their potential ecological risks.This study investigated and analyzed the abundance of MPs in sed...The contamination and accumulation of microplastics(MPs)in mangrove ecosystems have become an increasing concern due to their potential ecological risks.This study investigated and analyzed the abundance of MPs in sediments,water,and benthos of mangrove areas(MA)and adjacent non-vegetated areas(NA)in Qinglan Bay.Results showed that the abundance of MPs in MA was significantly higher than in adjacent NA[sediment:(4.39±2.20)items/50 g dry weight(dw)vs.(4.10±2.71)items/50 g dw;water:(11.79±7.61)items/L vs.(10.61±5.93)items/L;benthos:(4.94±5.27)items/individual vs.(3.5±0.71)items/individual].The primary components identified in sediments and benthos were rayon and cellulose,while polyethylene(PE)and polypropylene(PP)dominated in water.Smaller MPs(<1000μm)accounted for 44%,43%,and 61%of the MPs in sediments,water,and benthos,respectively,indicating that smaller MPs are more likely to be ingested or captured by benthic organisms.Additionally,MPsenrichment was calculated in benthos[enrichment index(EI)=1.41],water(EI=1.11),and sediments(EI=1.09),confirming that the unique ecological environment of the MA leads to different distribution and accumulation characteristics of MPs compared to the NA.The ecological risk assessment revealed low MPs pollution levels in sediments and water,but higher risks were observed for polychaetes and bivalves.展开更多
Direct current(DC)power grids based on flexible high-voltage DC technology have become a common solution of facilitating the large-scale integration of distributed energy resources(DERs)and the construction of advance...Direct current(DC)power grids based on flexible high-voltage DC technology have become a common solution of facilitating the large-scale integration of distributed energy resources(DERs)and the construction of advanced urban power grids.In this study,a typical topology analysis is performed for an advanced urban medium-voltage DC(MVDC)distribution network with DERs,including wind,photovoltaic,and electrical energy storage elements.Then,a multi-time scale optimal power flow(OPF)strategy is proposed for the MVDC network in different operation modes,including utility grid-connected and off-grid operation modes.In the utility grid-connected operation mode,the day-ahead optimization objective minimizes both the DER power curtailment and the network power loss.In addition,in the off-grid operation mode,the day-ahead optimization objective prioritizes the satisfaction of loads,and the DER power curtailment and the network power loss are minimized.A dynamic weighting method is employed to transform the multi-objective optimization problem into a quadratically constrained quadratic programming(QCQP)problem,which is solvable via standard methods.During intraday scheduling,the optimization objective gives priority to ensure minimum deviation between the actual and predicted values of the state of charge of the battery,and then seeks to minimize the DER power curtailment and the network power loss.Model predictive control(MPC)is used to correct deviations according to the results of ultra short-term load forecasting.Furthermore,an improved particle swarm optimization(PSO)algorithm is applied for global intraday optimization,which effectively increases the convergence rate to obtain solutions.MATLAB simulation results indicate that the proposed optimization strategy is effective and efficient.展开更多
Due to the advantages such as low line cost,low transmission loss,and high power supply reliability,DC distribution networks have become the main development trend for future distribution networks.In this paper,a typi...Due to the advantages such as low line cost,low transmission loss,and high power supply reliability,DC distribution networks have become the main development trend for future distribution networks.In this paper,a typical DC distribution network with multiple voltage levels is considered as a research object.It is proposed that the interface converters between DC buses with different voltage levels be implemented through the series-parallel combination of full-bridge LLC resonant converters.To realize the decentralized self-discipline control of DC voltage under various working conditions,different slack buses are prepared according to the voltage ranges of the DC buses,and the voltage regulation modes of the DC distribution network are divided into main voltage regulation mode,backup voltage regulation mode,and off-grid voltage droop regulation mode.By introducing a voltage coefficient related to DC voltage deviation as a basis for mode switching,the voltage fluctuations caused by slow switching between control modes in the method of traditional voltage margin control is reduced,facilitating fast and smooth switching between different voltage regulation modes.Finally,a simulation model for DC distribution networks is constructed utilizing MATLAB/Simulink.Simulation results verify the effectiveness and feasibility of the proposed voltage regulation modes and switching methods for DC distribution networks.Finally,an experimental platform is also constructed to verify the feasibility of the mode switching method proposed in this paper.展开更多
基金The Natural Science Foundation of China under contract Nos 41806130 and 42407149the National Science Foundation for Post-doctoral Scientists of China under contract No.2024M750629+2 种基金the Natural Science Foundation of Guangdong Province under contract No.2018A0303130063the Marine Ecological Survey and Evaluation in Guangdong Province under contract No.0877-23GZTP01F179the Project of the Marine Geological Survey Program of China Geological Survey under contract Nos DD20230460,DD20242792,DD20211394,and DD20190308.
文摘The contamination and accumulation of microplastics(MPs)in mangrove ecosystems have become an increasing concern due to their potential ecological risks.This study investigated and analyzed the abundance of MPs in sediments,water,and benthos of mangrove areas(MA)and adjacent non-vegetated areas(NA)in Qinglan Bay.Results showed that the abundance of MPs in MA was significantly higher than in adjacent NA[sediment:(4.39±2.20)items/50 g dry weight(dw)vs.(4.10±2.71)items/50 g dw;water:(11.79±7.61)items/L vs.(10.61±5.93)items/L;benthos:(4.94±5.27)items/individual vs.(3.5±0.71)items/individual].The primary components identified in sediments and benthos were rayon and cellulose,while polyethylene(PE)and polypropylene(PP)dominated in water.Smaller MPs(<1000μm)accounted for 44%,43%,and 61%of the MPs in sediments,water,and benthos,respectively,indicating that smaller MPs are more likely to be ingested or captured by benthic organisms.Additionally,MPsenrichment was calculated in benthos[enrichment index(EI)=1.41],water(EI=1.11),and sediments(EI=1.09),confirming that the unique ecological environment of the MA leads to different distribution and accumulation characteristics of MPs compared to the NA.The ecological risk assessment revealed low MPs pollution levels in sediments and water,but higher risks were observed for polychaetes and bivalves.
基金supported by Fundamental Research Funds for the Central Universities(No.2019JBM057).
文摘Direct current(DC)power grids based on flexible high-voltage DC technology have become a common solution of facilitating the large-scale integration of distributed energy resources(DERs)and the construction of advanced urban power grids.In this study,a typical topology analysis is performed for an advanced urban medium-voltage DC(MVDC)distribution network with DERs,including wind,photovoltaic,and electrical energy storage elements.Then,a multi-time scale optimal power flow(OPF)strategy is proposed for the MVDC network in different operation modes,including utility grid-connected and off-grid operation modes.In the utility grid-connected operation mode,the day-ahead optimization objective minimizes both the DER power curtailment and the network power loss.In addition,in the off-grid operation mode,the day-ahead optimization objective prioritizes the satisfaction of loads,and the DER power curtailment and the network power loss are minimized.A dynamic weighting method is employed to transform the multi-objective optimization problem into a quadratically constrained quadratic programming(QCQP)problem,which is solvable via standard methods.During intraday scheduling,the optimization objective gives priority to ensure minimum deviation between the actual and predicted values of the state of charge of the battery,and then seeks to minimize the DER power curtailment and the network power loss.Model predictive control(MPC)is used to correct deviations according to the results of ultra short-term load forecasting.Furthermore,an improved particle swarm optimization(PSO)algorithm is applied for global intraday optimization,which effectively increases the convergence rate to obtain solutions.MATLAB simulation results indicate that the proposed optimization strategy is effective and efficient.
基金supported by Fundamental Research Funds for the Central Universities(No.2019JBM057)。
文摘Due to the advantages such as low line cost,low transmission loss,and high power supply reliability,DC distribution networks have become the main development trend for future distribution networks.In this paper,a typical DC distribution network with multiple voltage levels is considered as a research object.It is proposed that the interface converters between DC buses with different voltage levels be implemented through the series-parallel combination of full-bridge LLC resonant converters.To realize the decentralized self-discipline control of DC voltage under various working conditions,different slack buses are prepared according to the voltage ranges of the DC buses,and the voltage regulation modes of the DC distribution network are divided into main voltage regulation mode,backup voltage regulation mode,and off-grid voltage droop regulation mode.By introducing a voltage coefficient related to DC voltage deviation as a basis for mode switching,the voltage fluctuations caused by slow switching between control modes in the method of traditional voltage margin control is reduced,facilitating fast and smooth switching between different voltage regulation modes.Finally,a simulation model for DC distribution networks is constructed utilizing MATLAB/Simulink.Simulation results verify the effectiveness and feasibility of the proposed voltage regulation modes and switching methods for DC distribution networks.Finally,an experimental platform is also constructed to verify the feasibility of the mode switching method proposed in this paper.
