Evaluating the reliability of distributed photovoltaic energy system and storage against household blackout

Distributed energy resources have been proven to be an effective and promising solution to enhance power system resilience and improve household-level reliability.In this paper,we propose a method to evaluate the reliability value of a photovoltaic(PV)energy system with a battery storage system(BSS)by considering the probability of grid outages causing household blackouts.Considering this reliability value,which is the economic profit and capital cost of PV+BSS,a simple formula is derived to calculate the optimal planning strategy.This strategy can provide household-level customers with a simple and straightforward expression for invested PV+BSS capacity.Case studies on 600 households located in eight zones of the US for the period of 2006 to 2015 demonstrate that adding the reliability value to economic profit allows households to invest in a larger PV+BSS and avoid loss of load caused by blackouts.Owing to the differences in blackout hours,households from the 8 zones express distinct willingness to install PV+BSS.The greater the probability of blackout,the greater revenue that household can get from the PV+BSS.The simulation example shows that the planning strategy obtained by proposed model has good economy in the actual operation and able to reduce the economic risk of power failure of the household users.This model can provide household with an easy and straightforward investment strategy of PV+BSS capacity.

Role of optimal transmission switching in accommodating renewable energy in deep peak regulation-enabled power systems

Due to the shortage of fossil energy and the pollution caused by combustion of fossil fuels,the proportion of renewable energy in power systems is gradually increasing across the world.Accordingly,the capacity of power systems to accommodate renewable energy must be improved.However,integration of a large amount of renewable energy into power grids may result in network congestion.Hence,in this study,optimal transmission switching(OTS)is considered as an important method of accommodating renewable energy.It is incorporated into the operation of a power grid along with deep peak regulation of thermal power units,forming an interactive mode of coordinated operation of source and network.A stochastic unit commitment model consider!ng deep peak regulation and OTS is established,and the role of OTS in promoting the accommodation of renewable energy is analyzed quantitatively.The results of case studies involving the IEEE 30-bus system demonstrate that OTS can enable utilization of the potential of deep peak regulation and facilitate the accommodation of renewable energy.

Generation-expansion planning with linearized primary frequency response constraints

As renewable energy resources increasingly penetrate the electric grid,the inertia capability of power systems has become a developmental bottleneck.Nevertheless,the importance of primary frequency response(PFR)when making generation-expansion plans has been largely ignored.In this paper,we propose an optimal generation-expansion planning framework for wind and thermal power plants that takes PFR into account.The model is based on the frequency equivalent model.It includes investment,startup/shutdown,and typical operating costs for both thermal and renewable generators.The linearization constraints of PFR are derived theoretically.Case studies based on the modified IEEE 39-bus system demonstrate the efficiency and effectiveness of the proposed method.Compared with methods that ignore PFR,the method proposed in this paper can effectively reduce the cost of the entire planning and operation cycle,improving the accommodation rate of renewable energy.

Carbon-neutral pathway to mitigating transport-power grid cross-sector effects

Dear Editor,The growing demand for transportation energy has brought increasing challenges to reducing greenhouse gas emissions.Currently,many countries or regions have proposed solutions to achieve carbon-neutral transportation such as the rapid expansion of the global electric vehicle(EV)market.However,these benefits are not free.Before the goal of decarbonization in electricity is achieved,the“pseudo net zero emissions”effect of the transportation sector will inevitably be accompanied by a quiet shifting of carbon responsibility.1 This shift is undoubtedly fatal for both net zero emissions at the national level and carbon responsibility at the industry level;however,the corresponding effects have not yet been clarified.

Soft Open Point Planning in Renewable-dominated Distribution Grids with Building Thermal Storage

With an increasing integration of intermittent distributed energy resources(DERs),the consequent voltage excursion and thermal overloading issues limit the self-sufficiency of distribution networks(DNs).The concept of soft open point(SOP)has been proposed as a promising solution to improve the hosting capacity of DNs.In this paper,considering the ability of building thermal storage(BTS)to increase the penetration of renewable energy in DNs,we provide an optimal planning framework for SOP and DER.The optimal planning model is aimed at minimizing the investment and operational costs while respecting various constraints,including the self-sufficiency requirement of the DN,SOP,building thermal storage capacity and DER operations,etc.A steady-state SOP model is formulated and linearized to be incorporated into the planning framework.To make full use of the BTS flexibility provided by ubiquitous buildings,a differential equation model for building thermal dynamics is formulated.A hybrid stochastic/robust optimization approach is adopted to depict the uncertainties in renewable energy and market prices.IEEE 33-bus feeder and a realistic DN in the metropolitan area of Caracas are tested to validate the effectiveness of the proposed framework and method.Case studies show that SOP/BTS plays a complementary and coordinated coupling role in the thermo-electric system,thereby effectively improving the hosting capacity and self-sufficiency of DNs.

Sharing Economy in Local Energy Markets

With an increase in the electrification of end-use sectors,various resources on the demand side provide great flexibility potential for system operation,which also leads to problems such as the strong randomness of power consumption behavior,the low utilization rate of flexible resources,and difficulties in cost recovery.With the core idea of“access over ownership”,the concept of the sharing economy has gained substantial popularity in the local energy market in recent years.Thus,we provide an overview of the potential market design for the sharing economy in local energy markets(LEMs)and conduct a detailed review of research related to local energy sharing,enabling technologies,and potential practices.This paper can provide a useful reference and insights for the activation of demand-side flexibility potential.Hopefully,this paper can also provide novel insights into the development and further integration of the sharing economy in LEMs.

Dispatching Fuel-cell Hybrid Electric Vehicles Toward Transportation and Energy Systems Integration

With the increasing integration of traditional elec-tric vehicles(EVs),the ensuing congestion and overloading issues have threatened the reliability of power grid operations.Hydrogen has been advocated as a promising energy carrier to achieve low-carbon transportation and energy(trans-energy)systems,which can support the popularization of fuel-cell hybrid EVs(FCHEVs)while enhancing the flexibility of power grids.In this paper,we propose an optimal scheduling framework for trans-energy systems that evaluates the merits of the hydrogen supply chain from water electrolysis,compressed storage and transportation to FCHEV utilization.A detailed FCHEV model is established,and mileage is modeled as a function of the stored electricity and hydrogen mass.A stochastic programming-based scheduling model is formulated,which minimizes the total cost of unit commitment and the hydrogen supply chain.The Dijkstra algorithm is adopted to search the shortest path for hydrogen transportation.Case studies demonstrate that FCHEVs can reduce the operational costs of tran-energy systems and facilitate the accommodation of renewable energy when compared to traditional EVs.Index Terms-Fuel-cell hybrid electric vehicle,hydrogen,mileage model,shortest path search,trans-energy systems.

Resilience-oriented Valuation for Energy Storage Amidst Extreme Events

In power grids,the frequency is increasing of extreme accidents which have a low probability but high risk such as natural disasters and deliberate attacks.This has sparked discussions on the resilience of power grids.Energy-storage systems(ESSs)are critical for enhancing the resilience of power grids.ESSs,with their mechanism of flexible charging and discharging,adjust energy usage as needed during disasters,thereby mitigating the impact on the grid and enhancing security and resilience.This,in turn,ensures the power system’s stable operation.Currently,there is limited systematic research quantifying the economic value of energy storage in resilience scenarios.Therefore,a model and methodology were proposed to quantify the value of energy storage systems for enhancing grid resilience during extreme events.A two-stage stochastic optimization mathematical model was developed.The first stage involves pre-deployment based on day-ahead expectations,and the second stage involves simulating potential failure scenarios through real-time scheduling.Considering the temporal dimension,the energy storage systems with flexible regulation capabilities was used as emergency power sources to reduce occurrences of load-shedding.Here,a novel index was proposed that quantifies the resilience value of energy storage as the economic value of energy storage per unit of capacity,as reflected in the emergency dispatch model.This index helps determine the balance between the energy storage investment cost and resilience value.Finally,an IEEE-30 node transmission system was used to verify the feasibility and effectiveness of the proposed method.The findings revealed a significant improvement in the resilience value,with a 23.49%increase observed when energy storage systems were implemented compared to the scenario without energy storage systems.The optimal capacity configurations for the flywheel,lithium-ion batteries,and pumped hydro storage were 10 MW,11 MW,and 12 MW,respectively,highlight their potential to maximize value in experimental system.

Fast Solution Method for the Large-scale Unit Commitment Problem with Long-term Storage

Long-term storage(LTS)can provide various services to address seasonal fluctuations in variable renewable energy by reducing energy curtailment.However,long-term unit commitment(UC)with LTS involves mixed-integer programming with large-scale coupling constraints between consecutive intervals(state-of-charge(SOC)constraint of LTS,ramping rate,and minimum up/down time constraints of thermal units),resulting in a significant computational burden.Herein,an iterative-based fast solution method is proposed to solve the long-term UC with LTS.First,the UC with coupling constraints is split into several sub problems that can be solved in parallel.Second,the solutions of the sub problems are adjusted to obtain a feasible solution that satisfies the coupling constraints.Third,a decoupling method for long-term time-series coupling constraints is proposed to determine the global optimization of the SOC of the LTS.The price-arbitrage model of the LTS determines the SOC boundary of the LTS for each sub problem.Finally,the sub problem with the SOC boundary of the LTS is iteratively solved independently.The proposed method was verified using a modified IEEE 24-bus system.The results showed that the computation time of the unit combination problem can be reduced by 97.8%,with a relative error of 3.62%.

Ubiquitination and degradation of SIK2 by DNA-PKcs deficiency promote radiation-induced mitotic catastrophe

Salt-inducible kinase 2 (SIK2) is a member of the AMP-activated serine/threonine kinase family. It has been reported that inhibition of SIK2 can enhance the cytotoxicity of paclitaxel,1 promote premitotic apoptosis, and lead to cell cycle arrest in the metaphase.2 Thus, targeting SIK2 may be a therapeutic strategy for cancers drug and radiotherapy resistance. Mitotic catastrophe is a type of abnormal mitosis leading to cell death characterized by the multipolar spindle and multinucleation, which was first discovered during an ionizing radiation (IR)-induced cell damage.3 However, the mechanism of mitotic catastrophe is not well understood. The present study aimed to assess the effect of the knockdown of SIK2 on IR-induced mitotic catastrophe.

Incentive mechanism for sharing distributed energy resources

To improve the controllability and utilization of distributed energy resources(DERs),distribution-level electricity markets based on consumers’bidding and offers have been proposed.However,the transaction costs will dramatically increase with the rapid development of DERs.Therefore,in this paper,we develop an energy sharing scheme that allows users to share DERs with neighbors,and design a novel incentive mechanism for benefit allocation without users’bidding on electricity prices.In the energy sharing scheme,an aggregator organizes a number of electricity users,and trades with the connected power grid.The aggregator is aimed at minimizing the total costs by matching the surplus energy from DERs and electrical loads.A novel index,termed as sharing contribution rate(SCR),is presented to evaluate different users’contributions to the energy sharing.Then,based on users’SCRs,an efficient benefit allocation mechanism is implemented to determine the aggregator’s payment to users that incentivize their participation in energy sharing.To avoid users’bidding,we propose a decentralized framework for the energy sharing and incentive mechanism.Case studies based on real-world datasets demonstrate that the aggregator and users can benefit from the energy sharing scheme,and the incentive mechanism allocates the benefits according to users’contributions.

Transmission network expansion planning with embedded constraints of short circuit currents and N-1 security

An approach of transmission network expan-sion planning with embedded constraints of short circuit currents and N-1 security is proposed in this paper.The problem brought on by the strong nonlinearity property of short circuit currents is solved with a linearization method based on the DC power flow.The model can be converted to a mixed-integer linear programming problem,realizing the optimization of planning model that considers the constraints of linearized short circuit currents and N-1 security.To compensate the error caused by the assump-tions of DC power flow,the compensation factor is pro-posed.With this factor,an iterative algorithm that can compensate the linearization error is then presented.The case study based on the IEEE 118-bus system shows that the proposed model and approach can be utilized to:opti-mize the construction strategy of transmission lines;ensure the N-1 security of the network;and effectively limit the short circuit currents of the system.

On the Consistency of Renewable-to-Hydrogen Pricing

With the proposal of carbon neutrality goals and hydrogen energy development strategies in various countries,the development and construction of hydrogen supply chains have become important priorities.However,existing research has paid little attention to the hydrogen market and pricing.Therefore,a hydrogen pricing method based on marginal pricing theory is proposed in this paper,which adapts to hydrogen systems with renewable-to-hydrogen as a major source,in the future.A hydrogen energy market is established to define the industrial chain of hydrogen and the hydrogen trading process.The hydrogen market-clearing model is formulated considering a dynamic line pack.Due to its nonconvexity,the model is equivalently converted into mixed-integer second-order cone programming,and the optimality gap is minimized by introducing a penalty term.Based on the clearing solution,the concept and calculation method of the locational marginal hydrogen price(LMHP)are proposed with respect to the locational marginal price(LMP)in electricity markets.Case studies based on a modified Belgium 20-node gas network and Pennsylvania,New Jersey,and Maryland(PJM)market operation data demonstrate the consistency between LMHP and LMP.

Constructing a V2G-enabled Regional Energy Internet for Cost-efficient Carbon Trading

The increasing penetration of plug-in electric ve- hicles (PEVs) has highlighted the importance of coordinating ubiquitous distributed energy resources (DERs) via the internet of things (IoT).With the help of vehicle-to-grid (V2G) technology, PEVs can be aggregated to behave as a storage system, yielding both economic and environmental benefits. In this paper, we propose an optimal bidding framework for a V2G-enabled re- gional energy internet (REI) to participate in day-ahead markets considering carbon trading. The REI operator aims to maximize the net profits from day-ahead markets while anticipating real- time adjustments. A detailed battery model is developed to depict the charging and discharging capability of V2G-enabled PEVs. A two-stage stochastic optimization model is formulated to schedule the operation of PEV fleets against various sources of uncertainties, e.g., the arrival and departure time of PEVs, solar power and real-time prices. Case studies undertaken based on realistic datasets demonstrate that the coordination of the V2G- enabled PEVs and other DERs can facilitate the accommodation of renewable energy, thus improving the REI’s revenues in energy and carbon markets.

Insulating materials for realising carbon neutrality:Opportunities,remaining issues and challenges

The 2050 carbon-neutral vision spawns a novel energy structure revolution,and the construction of the future energy structure is based on equipment innovation.Insulating material,as the core of electrical power equipment and electrified transportation asset,faces unprecedented challenges and opportunities.The goal of carbon neutral and the urgent need for innovation in electric power equipment and electrification assets are first discussed.The engineering challenges constrained by the insulation system in future electric power equipment/devices and electrified transportation assets are investigated.Insulating materials,including intelligent insulating material,high thermal conductivity insulating material,high energy storage density insulating material,extreme environment resistant insulating material,and environmental-friendly insulating material,are cat-egorised with their scientific issues,opportunities and challenges under the goal of carbon neutrality being discussed.In the context of carbon neutrality,not only improves the understanding of the insulation problems from a macro level,that is,electrical power equipment and electrified transportation asset,but also offers opportunities,remaining issues and challenges from the insulating material level.It is hoped that this paper en-visions the challenges regarding design and reliability of insulations in electrical equipment and electric vehicles in the context of policies towards carbon neutrality rules.The authors also hope that this paper can be helpful in future development and research of novel insulating materials,which promote the realisation of the carbon-neutral vision.

Operational Risk-averse Routing Optimization for Cyber-physical Power Systems

The extensive application of modern information and communication technology in the power system through the in-depth integration of the information system and the power system has led to the gradual development of the cyberphysical power system(CPPS).While advanced information technology increases the safety and reliability of power system operations,it also increases the risks of fault propagation.To improve the reliability of CPPS from the perspective of power communication routing,it is proposed that the CPPS model and vulnerability assessment of power node reflect the correlation between information and energy flows with the service impact on power grid operation,which is an important index for evaluating communication services.According to the distribution of services at the different important levels on the links,the importance of the cross-layer link is established as the vulnerability evaluation index of the communication network.Then,the routing optimization model is proposed in combination with the service transmission risk under cyber-attack and the operating characteristics of the information system,which is solved through an improved fast-convergent genetic algorithm.The simulation results show that the proposed method allocates the alternate route to the low-risk link without significantly increasing the delay of the main route,which effectively improves the power supply reliability of CPPS in extreme cyber-attack scenarios.

氧化石墨炔提升界面电荷传输及分离以构筑高效二元有机太阳能电池器件

通过界面工程调节载流子动力学是提高太阳能电池器件效率的关键方式.在本工作中,我们成功制备了具有大量官能团的高分散性氧化石墨炔(GDYO),并将其应用于优化空穴传输材料PEDOT:PSS的性质以制备有机太阳能电池器件.结果表明,GDYO与PEDOT:PSS之间的π–π相互作用有利于优化电荷转移通道,提高空穴传输层的电导率和载流子迁移率.此外,界面接触的改善有助于抑制电荷的复合,提高空穴传输层和活性层之间的电荷提取.同时,活性层的形貌得到有效改善,瞬态吸收测试结果证实这有利于载流子分离率的提升,进而提高器件性能.因此,通过对载流子动力学的系统性优化,二元有机太阳能电池的光电转换效率达到17.5%,认证效率达到17.2%.本工作结果表明功能化石墨炔在有机光电器件领域具有广阔的应用前景.