Research on Regulation Method of Energy Storage System Based on Multi-Stage Robust Optimization

To address the scheduling problem involving energy storage systems and uncertain energy,we propose a method based on multi-stage robust optimization.This approach aims to regulate the energy storage system by using a multi-stage robust optimal control method,which helps overcome the limitations of traditional methods in terms of time scale.The goal is to effectively utilize the energy storage power station system to address issues caused by unpredictable variations in environmental energy and fluctuating load throughout the day.To achieve this,a mathematical model is constructed to represent uncertain energy sources such as photovoltaic and wind power.The generalized Benders Decomposition method is then employed to solve the multi-stage objective optimization problem.By decomposing the problem into a series of sub-objectives,the system scale is effectively reduced,and the algorithm’s convergence ability is improved.Compared with other algorithms,the multi-stage robust optimization model has better economy and convergence ability and can be used to guide the power dispatching of uncertain energy and energy storage systems.

Multi-stage Co-planning Model for Power Distribution System and Hydrogen Energy System Under Uncertainties

The increased deployment of electricity-based hydrogen production strengthens the coupling of power distribution system(PDS)and hydrogen energy system(HES).Considering that power to hydrogen(PtH)has great potential to facilitate the usage of renewable energy sources(RESs),the coordination of PDS and HES is important for planning purposes under high RES penetration.To this end,this paper proposes a multi-stage co-planning model for the PDS and HES.For the PDS,investment decisions on network assets and RES are optimized to supply the growing electric load and PtHs.For the HES,capacities of PtHs and hydrogen storages(HSs)are optimally determined to satisfy hydrogen load considering the hydrogen production,tube trailer transportation,and storage constraints.The overall planning problem is formulated as a multistage stochastic optimization model,in which the investment decisions are sequentially made as the uncertainties of electric and hydrogen load growth states are revealed gradually over periods.Case studies validate that the proposed co-planning model can reduce the total planning cost,promote RES consumption,and obtain more flexible decisions under long-term load growth uncertainties.

Mechanical and hydraulic properties of fault rocks under multi‑stage cyclic loading and unloading

The rock mass in fault zones is frequently subjected to cyclic loading and unloading during deep resource exploitation and tunnel excavation.Research on the mechanical and hydraulic characteristics of fault rock during the cyclic loading and unloading is of great signifcance for revealing the formation mechanism of water-conducting pathways in fault and preventing water inrush disasters.In this study,the mechanical and seepage tests of fault rock under the multi-stage cyclic loading and unloading of axial compression were carried out by using the fuid–solid coupling triaxial experimental device.The hysteresis loop of the stress–strain curve,peak strain rate,secant Young's modulus,and permeability of fault rock were obtained,and the evolution law of the dissipated energy of fault rock with the cyclic number of load and unloading was discussed.The experimental results show that with an increase in the cyclic number of loading and unloading,several changes occur.The hysteresis loop of the stress–strain curve of the fault rock shifts towards higher levels of strain.Additionally,both the peak strain rate and the secant Young's modulus of the fault rock increase,resulting in an increase in the secant Young's modulus of the fault rock mass.However,the growth rate of the secant Young's modulus gradually slows down with the increase of cyclic number of loading and unloading.The permeability evolution of fault rock under the multi-stage cyclic loading and unloading of axial compression can be divided into three stages:steady increase stage,cyclic decrease stage,and rapid increase stage.Besides,the calculation model of dissipated energy of fault rock considering the efective stress was established.The calculation results show that the relationship between the dissipated energy of fault rock and the cyclic number of loading and unloading conforms to an exponential function.

Whole-lifetime Coordinated Service Strategy for Battery Energy Storage System Considering Multi-stage Battery Aging Characteristics

One battery energy storage system(BESS)can be used to provide different services,such as energy arbitrage(EA)and frequency regulation(FR)support,etc.,which have different revenues and lead to different battery degradation profiles.This paper proposes a whole-lifetime coordinated service strategy to maximize the total operation profit of BESS.A multi-stage battery aging model is developed to characterize the battery aging rates during the whole lifetime.Considering the uncertainty of electricity price in EA service and frequency deviation in FR service,the whole problem is formulated as a twostage stochastic programming problem.At the first stage,the optimal service switching scheme between the EA and FR services are formulated to maximize the expected value of the whole-lifetime operation profit.At the second stage,the output power of BESS in EA service is optimized according to the electricity price in the hourly timescale,whereas the output power of BESS in FR service is directly determined according to the frequency deviation in the second timescale.The above optimization problem is then converted as a deterministic mixed-integer nonlinear programming(MINLP)model with bilinear items.Mc Cormick envelopes and a bound tightening algorithm are used to solve it.Numerical simulation is carried out to validate the effectiveness and advantages of the proposed strategy.

Multi-stage expansion planning of energy storage integrated soft open points considering tie-line reconstruction

With the rapid development of flexible interconnection technology in active distribution networks(ADNs),many power electronic devices have been employed to improve system operational performance.As a novel fully-con-trolled power electronic device,energy storage integrated soft open point(ESOP)is gradually replacing traditional switches.This can significantly enhance the controllability of ADNs.To facilitate the utilization of ESOP,device loca-tions and capacities should be configured optimally.Thus,this paper proposes a multi-stage expansion planning method of ESOP with the consideration of tie-line reconstruction.First,based on multi-terminal modular design characteristics,the ESOP planning model is established.A multi-stage planning framework of ESOP is then presented,in which the evolutionary relationship among different planning schemes is analyzed.Based on this framework,a multi-stage planning method of ESOP with consideration of tie-line reconstruction is subsequently proposed.Finally,case studies are conducted on a modified practical distribution network,and the cost-benefit analysis of device and multiple impact factors are given to prove the effectiveness of the proposed method.

Exergy analysis of multi-stage crude distillation units

This paper aims effect on crude distillation to investigate the multi-stage units （CDUs） in thermody- namics. In this regard, we proposed three-, four-, five-, and six-stage CDU processes with all variables constrained to be almost the same except for the number of stages. We also analyzed the energy and exergy to assess the energy consumed by each process. Because additional distillation units would share the processing load and thus prevent products with low boiling points from overheating, the heat demand of the CDUs decreases with increasing stages and thus reduces the heat supply. Exergy loss is considered as a key parameter to assess these processes. When the exergy losses in heat exchangers are disregarded, the three- and four-stage CDUs have lower exergy losses than the five- and six-stage CDUs. When the overall exergy losses are considered, the optimum number of stages of CDUs depends on the exergy efficiency of heat integration.

Hydraulic Characteristics of Multi-Stage Orifice Plate

Energy dissipater of multi-stage orifice plate, as a kind of effective energy dissipater with characteristics of high energy dissipation ratio and low cavitations risk, has become welcomed more and more by hydraulics researchers. The relationship between the contraction ratio of upper stage orifice plate and the lower one's under the principle of equal-cavitation characteristics, and the reasonable distance between upper stage orifice plate and the lower one under the condition of complying with this principle, are two important factors to be considered for multi-stage energy dissipater design. In the present paper, these two factors were analyzed by theoretical consideration and numerical simulations, and solving methods were put forward. The conclusion in this paper was proved to be reasonable by model experiment.

Development of Novel Water-extraction System with Thermoelectric Module Using Solar and Wind Power in Arid Land

This study aimed to develop a water-extraction system which could produce the fresh water from the air in arid regions and which used renewable energies as the electric power source. In this paper, the experiments for water extraction from the air were carried out by using the novel multi-stage water-extraction device with Peltier deices for two cases of temperature and related humidity of the air. One was the case where the temperature and the related humidity of the air were constant, and the other was the case where they were simulated the variation of the temperature and related humidity of the air in a day of summer and spring in Loess Plateau, China. The effects of the temperature and related humidity of the atmospheric air and supply the electric power to Peltier devices on performance of water production of the device were investigated and reported.