A bi-level optimization framework for charging station design problem considering heterogeneous charging modes

Purpose–The purpose of this paper is to optimize the design of charging station deployed at the terminal station for electric transit,with explicit consideration of heterogenous charging modes.Design/methodology/approach–The authors proposed a bi-level model to optimize the decision-making at both tactical and operational levels simultaneously.Specifically,at the operational level(i.e.lower level),the service schedule and recharging plan of electric buses are optimized under specific design of charging station.The objective of lower-level model is to minimize total daily operational cost.This model is solved by a tailored column generation-based heuristic algorithm.At the tactical level(i.e.upper level),the design of charging station is optimized based upon the results obtained at the lower level.A tabu search algorithm is proposed subsequently to solve the upper-level model.Findings–This study conducted numerical cases to validate the applicability of the proposed model.Some managerial insights stemmed from numerical case studies are revealed and discussed,which can help transit agencies design charging station scientifically.Originality/value–The joint consideration of heterogeneous charging modes in charging station would further lower the operational cost of electric transit and speed up the market penetration of battery electric buses.

A new nonlinear photoconductive terahertz radiation source based on photon-activated charge domain quenched mode

We present a high-performance terahertz(THz)radiation source based on the photon-activated charge domain(PACD)quenched mode of GaAs photoconductive antennas(GaAs PCA).The THz radiation characteristics of the GaAs PCA under different operating modes are studied.Compared with the linear mode,the intensity of THz wave radiated by the GaAs PCA can be greatly enhanced due to the avalanche multiplication effect of carriers in the PACD quenched mode.The results show that when the carrier multiplication ratio is 16.92,the peak-to-peak value of THz field radiated in the PACD quenched mode increases by as much as about 4.19 times compared to the maximum values in the linear mode.

Dynamic time prediction for electric vehicle charging based on charging pattern recognition

Overcharging is an important safety issue in the charging process of electric vehicle power batteries,and can easily lead to accelerated battery aging and serious safety accidents.It is necessary to accurately predict the vehicle’s charging time to effectively prevent the battery from overcharging.Due to the complex structure of the battery pack and various charging modes,the traditional charging time prediction method often encounters modeling difficulties and low accuracy.In response to the above problems,data drivers and machine learning theories are applied.On the basis of fully considering the different electric vehicle battery management system(BMS)charging modes,a charging time prediction method with charging mode recognition is proposed.First,an intelligent algorithm based on dynamic weighted density peak clustering(DWDPC)and random forest fusion is proposed to classify vehicle charging modes.Then,on the basis of an improved simplified particle swarm optimization(ISPSO)algorithm,a high-performance charging time prediction method is constructed by fully integrating long short-term memory(LSTM)and a strong tracking filter.Finally,the data run by the actual engineering system are verified for the proposed charging time prediction algorithm.Experimental results show that the new method can effectively distinguish the charging modes of different vehicles,identify the charging characteristics of different electric vehicles,and achieve high prediction accuracy.

Experimental investigation of limit space charge accumulation mode operation in a semi-insulating GaAs photoconductive semiconductor switch

Experiments with the limited space-charge accumulation（LSA） mode of oscillation in a large gap semiinsulating （SI） GaAs photoconductive semiconductor switch（PCSS） are discussed.It has been observed that growth and drift of a photo-activated charge domain（PACD） are quenched only when the bias voltage is more than twice the threshold voltage.The original negative resistance characteristics are directly utilized in the LSA mode;during LSA operation the spatial average of the electric field varies over a large portion of the negative differential mobility region of the velocity-electric field characteristic.The work efficiency of an SI GaAs PCSS is remarkably enhanced by electric field excursions into the positive resistance region when the total electric field is only below the threshold part of the time.The LSA mode can only operate in the certain conditions that satisfy the quenching of the accumulation layer and the smaller initial domain voltage.

A double-stage start-up structure to limit the inrush current used in current mode charge pump

A double-stage start-up structure to limit the inrush current used in current-mode charge pump with wide input range,fixed output and multimode operation is presented in this paper.As a widely utilized power source implement,a Li-battery is always used as the power supply for chips.Due to the internal resistance,a potential drop will be generated at the input terminal of the chip with an input current.A false shut down with a low supply voltage will happen if the input current is too large,leading to the degradation of the Li-battery＇s service life.To solve this problem,the inrush current is limited by introducing a new start-up state.All of the circuits have been implemented with the NUVOTON 0.6 μm CMOS process.The measurement results show that the inrush current can be limited below 1 A within all input supply ranges,and the power efficiency is higher than the conventional structure.