Probabilistic production simulation of a power system with wind power penetration based on improved UGF techniques

Universal Generating Function(UGF)techniques have been applied to Multi-State System(MSS)reliability analysis,such as long term reserve expansion of power systems with high wind power penetration.However,using simple steady-state distribution models for wind power and large generating units in reliability assessment can yield pessimistic appraisals.To more accurately assess the power system reliability,UGF techniques are extended to dynamic probabilistic simulation analysis on two aspects of modelling improvement.Firstly,a principal component analysis(PCA)combined with a hierarchal clustering algorithm is used to achieve the salient and time-varying patterns of wind power,then a sequential UGF equivalent model of wind power output is established by an apportioning method.Secondly,other than the traditional two-state models,the conventional generator UGF equivalent model is established as a four discrete-state continuous-time Markov model by Lztransform.In the construction process of such a UGF model,the state values are transformed into the integral multiples of one common factor by choosing proper common factors,thus effectively restraining the exponential growth of its state number and alleviating the explosion thereof.The method is suitable for reliability assessment with dynamic probabilistic distributed random variables.In addition,by acquiring the clustering information of wind power,the system reliability indices,such as fuel cost and CO_(2) emissions through different seasons and on different workdays,are calculated.Finally,the effectiveness of the method is verified by a modified IEEE-RTS 79 system integrated with several wind farms of historical hourly wind power data of Zhangbei wind farm in North China.

Renewable Generation Capacity and Reliability Assessments for Resilient Active Distribution Networks Based on Time-sequence Production Simulation

The penetration of renewable generation will affect the energy utilization efficiency,economic benefit and reliability of the active distribution network(ADN).This paper proposes a time-sequence production simulation(TSPS)method for re-newable generation capacity and reliability assessments in ADN considering two operational status:the normal status and the fault status.During normal operation,an optimal dispatch model is proposed to promote the renewable consumption and increase the economic benefit.When a failure occurs,the renewable generators are partitioned into islands for resilient power supply and reliability improvement.A novel dynamic island partition model is presented based on mixed integer second-order cone programming(MISOCP).The effectiveness of the proposed TSPS method is demonstrated in a standard network integrated with historical data of load and renewable generations.

Workshop on Simulation and Systems Analysis for Rice Production(SARP) held at CNRRI

SARP Workshop on risk analysis of agroecological zonation and optimization of crop rotation was held at CNRRI’s research center on 24—27 Oct, 1995. Experts from Philippines, India, China, and IRRI were present in the workshop. Participants exchanged the research results on the field of land use, soil erosion. optimization of rice—wheat, rice—peanut, rice—corn cropping system in the different environments, risk analysis of rice based cropping system, nitrogen balance in rice based cropping system with system approach, demonstrated models used in their studies, and discussed the ongoing cooperative research.

Simulation of Potential Productivity of Early Season Rice Varieties in Different Reqions of South China

Rice is a staple food crop in China.Since the 1950’s,many new varieties havebeen used and resulted in great increase ofyield.However there were still some barriersin the nationwide extension of new varietiesdue to the insufficient information about thecharacteristics of varieties.So,it is impor-tant to find ways of determining the potential

Quantifying major sources of uncertainty in projecting the impact of climate change on wheat grain yield in dryland environments

Modelling the impact of climate change on cropping systems is crucial to support policy-making for farmers and stakeholders.Nevertheless,there exists inherent uncertainty in such cases.General Circulation Models(GCMs)and future climate change scenarios(different Representative Concentration Pathways(RCPs)in different future time periods)are among the major sources of uncertainty in projecting the impact of climate change on crop grain yield.This study quantified the different sources of uncertainty associated with future climate change impact on wheat grain yield in dryland environments(Shiraz,Hamedan,Sanandaj,Kermanshah and Khorramabad)in eastern and southern Iran.These five representative locations can be categorized into three climate classes:arid cold(Shiraz),semi-arid cold(Hamedan and Sanandaj)and semi-arid cool(Kermanshah and Khorramabad).Accordingly,the downscaled daily outputs of 29 GCMs under two RCPs(RCP4.5 and RCP8.5)in the near future(2030s),middle future(2050s)and far future(2080s)were used as inputs for the Agricultural Production Systems sIMulator(APSIM)-wheat model.Analysis of variance(ANOVA)was employed to quantify the sources of uncertainty in projecting the impact of climate change on wheat grain yield.Years from 1980 to 2009 were regarded as the baseline period.The projection results indicated that wheat grain yield was expected to increase by 12.30%,17.10%,and 17.70%in the near future(2030s),middle future(2050s)and far future(2080s),respectively.The increases differed under different RCPs in different future time periods,ranging from 11.70%(under RCP4.5 in the 2030s)to 20.20%(under RCP8.5 in the 2080s)by averaging all GCMs and locations,implying that future wheat grain yield depended largely upon the rising CO2 concentrations.ANOVA results revealed that more than 97.22% of the variance in future wheat grain yield was explained by locations,followed by scenarios,GCMs,and their interactions.Specifically,at the semi-arid climate locations(Hamedan,Sanandaj,Kermanshah and Khorramabad),most of the variations arose from the scenarios(77.25%),while at the arid climate location(Shiraz),GCMs(54.00%)accounted for the greatest variation.Overall,the ensemble use of a wide range of GCMs should be given priority to narrow the uncertainty when projecting wheat grain yield under changing climate conditions,particularly in dryland environments characterized by large fluctuations in rainfall and temperature.Moreover,the current research suggested some GCMs(e.g.,the IPSL-CM5B-LR,CCSM4,and BNU-ESM)that made moderate effects in projecting the impact of climate change on wheat grain yield to be used to project future climate conditions in similar environments worldwide.

A process model for simulating net primary productivity (NPP) based on the interaction of water-heat process and nitrogen: a case study in Lantsang valley

Terrestrial carbon cycle and the global atmospheric CO2 budget are important foci in global climate change research. Simulating net primary productivity （NPP） of terrestrial ecosystems is important for carbon cycle research. In this study, a plant-atmosphere-soil continuum nitrogen （N） cycling model was developed and incorporated into the Boreal Ecosystem Productivity Simulator （BEPS） model. With the established database （leaf area index, land cover, daily meteorology data, vegetation and soil） at a 1 km resolution, daily maps of NPP for Lantsang valley in 2007 were produced, and the spatial-temporal patterns of NPP and mechanisms of its responses to soil N level were further explored. The total NPP and mean NPP of Lantsang valley in 2007 were 66.5 Tg C and 416 g？m-2？a-1 C, respectively. In addition, statistical analysis of NPP of different land cover types was conducted and investigated. Compared with BEPS model （without considering nitrogen effect）, it was inferred that the plant carbon fixing for the upstream of Lantsang valley was also limited by soil available nitrogen besides temperature and precipitation. However, nitrogen has no evident limitation to NPP accumulation of broadleaf forest, which mainly distributed in the downstream of Lantsang valley.

Using simulation in layout verification of solar module assembly workshop

Facility layout problem(FLP)contemplates the optimization of space utilization,costs,and material flow.Commercial simulation softwares are commonly used to validate layouts by simulating the real world material flow and production process.To validate a layout scenario of a solar module assembly workshop,a 3D simulation model is presented which was designed on VisualComponents software.To begin with,we introduce the layout characteristics and use the systematic layout planning(SLP)method to design the block layout of workshop.Then,we built components library which contains all the facilities needed in the production line,specifically conveyors,processing equipments,robots,buffers.Finally,we have established a simulation layout model using the components in the customized library according to the block layout,and configured the components which were allocated in the layout by setting the parameters and building the connection between components via signal.To improve the performance of the workshop,we have found the best work-in-process(WIP)value for the workshop and the optimal number of workers.Additionally,the layout model was used to test collision and reachability.It demonstrated the production process in a realistic simulation environment which helped in the sales process as well.The reusable component models we have built make it easy to build a layout within a short time and validate the effectiveness of the layout scenarios for any other projects.

Optimal proportion of wind and PV capacity in provincial power systems based on bilevel optimization algorithm under low-carbon economy

In order to boost contributions of power systems to a low-carbon economy,the installed capacity of renewable power generation,such as wind and photovoltaic(PV)power generation should be well planned.A bilevel formulation is presented to optimize the proportion of wind and PV capacity in provincial power systems,in which,carbon emissions of generator units and features of renewable resources are taken into account.In the lowerlevel formulation,a time-sequence production simulation(TSPS)model that is suitable for actual power system has been adopted.In order to maximize benefits of energy conservation and emissions reduction resulting from renewable power generation,the commercial software called General Algebraic Modeling System(GAMS)is employed to optimize the annual operation of the power system.In the upper-level formulation,the optimal pattern search(OPS)algorithm is utilized to optimize the proportion of wind and PV capacity.The objective of the upper-level formulation is to maximize benefits of energy conservation and carbon emissions reductions optimized in the lowerlevel problem.Simulation results in practical provincial power systems validate the proposed model and corresponding solving algorithms.The optimization results can provide support to policy makers to make the polices related to renewable energy.

Model and application of renewable energy accommodation capacity calculation considering utilization level of inter-provincial tie-line

At present, the problem of abandoning wind and PV power in “Three North” region of China is particularly significant, and how to alleviate this problem has become the focus of universal attention. Calculation of renewable energy accommodation capacity is the basis to solve the problem of abandoning wind and PV power. Main problems of Chinese renewable energy accommodation is analyzed from power supply, power grid and load side aspects, and it focuses on the effect of inter-provincial tie-line to renewable energy accommodation capacity. At present, the inter-provincial tie-line utilization level is limited, which affected renewable energy accommodation to a certain extent. Based on the sequential production simulation model, a new kind of renewable energy accommodation capacity model is put forward considering the utilization level of inter-provincial tie-line. According to different system stability constraints and different electricity constraints of inter-provincial tie-line, 4 schemes are designed for comparative analysis, and the evaluation model is used to calculate renewable energy accommodation capacity of “Three North” region of China in 2020. Example analysis results verify validity of the model that releasing curve constraints, electricity constraints and stability constraints in turn can significantly enhance renewable energy accommodation capacity through effective use of inter-provincial tie-line transmission capacity. Research work in this paper can provide strong support for the planning and scheduling control of power grid.

An Economic Benefit Evaluation Model and its Application for Optimizing Transmission Capacity of Multinational Interconnections

Multinational power grid interconnections play a critical part in supporting the vision of global energy internet.During the early stages of the Global Energy Internet,the value proposition of multinational interconnections should be carefully investigated in order to stimulate the activities for associated countries in such potential interconnections.This paper proposes a new e conomic benefit evaluation model which is quantified by using a chronological production cost simulation approach.The economic benefit model comprehensively considered investment costs and the benefits of the decrease of load payments and the increase of net generation revenue due to a transmission project interconnected with different countries.This economic benefit model can assist to quantitatively determine the optimal transmission capacity for multinational interconnections to achieve maximum economic benefits as a whole.In the case study,the economic benefit of an interconnected system of western China and the Gulf States is assessed by using the method proposed in this paper.And the optimal interconnection capacity with maximum benefit is achieved.The case study shows that the proposed method can be used for economic benefit assessment and is of great significance to the multinational and intercontinental transmission interconnections.

Towards modeling pedestrian’s invisible trail for simulating crowd movement

Facility layout problem(FLP)contemplates the optimization of space utilization,costs,and material flow.Commercial simulation softwares are commonly used to validate layouts by simulating the real world material flow and production process.To validate a layout scenario of a solar module assembly workshop,a 3D simulation model is presented which was designed on VisualComponents software.To begin with,we introduce the layout characteristics and use the systematic layout planning(SLP)method to design the block layout of workshop.Then,we built components library which contains all the facilities needed in the production line,specifically conveyors,processing equipments,robots,buffers.Finally,we have established a simulation layout model using the components in the customized library according to the block layout,and configured the components which were allocated in the layout by setting the parameters and building the connection between components via signal.To improve the performance of the workshop,we have found the best work-in-process(WIP)value for the workshop and the optimal number of workers.Additionally,the layout model was used to test collision and reachability.It demonstrated the production process in a realistic simulation environment which helped in the sales process as well.The reusable component models we have built make it easy to build a layout within a short time and validate the effectiveness of the layout scenarios for any other projects.