Economic analysis of solar energy development in North Africa

The economic analysis of solar energy development is the basis of promoting the solar energy planning in north Africa and realizing the clean energy power transmission among continents. In this paper, the cost development trend of photovoltaic(PV) power and concentrating solar power(CSP) generation is analyzed, and the levelized cost of energy(LCOE) of solar power generation is forecasted. Then, taking the development of Tunisian solar energy as an example in the context of transcontinental transmission, PV power with energy storage and PV-CSP power generation are given as two kinds of development plan respectively. The installed capacity configurations of the two schemes are given with production simulation method, and comprehensive LCOE are calculated. The studies show that based on the LCOE forecast value, the LCOE of PV-CSP combined power generation will decrease when the annual utilization hours of transmission channel is increased. It can be chosen as one of important mode of the North Africa solar energy development.

HPDS133-bus:A Benchmark Test System for Distribution Systems with High Penetration of Distributed Generation

The benchmark test system for distribution systems is necessary and important for system analysis and result data checking.In order to meet the development demand of the distribution systems which integrate with a high penetration of distributed generation(DG),a benchmark test system for the distribution systems which adapts to current and future development trends is proposed.Based on the concentric zone theory and the typical regional settlement model in China,three typical distribution system scenarios corresponding to different system circle structures and regional development characteristics are designed in this paper.In order to adapt to the trend that the distribution systems will present the mixed state of AC and DC,a typical improvement scheme of distribution systems in urban scenario is presented.The benchmark test system of low-voltage distribution systems in a rural scenario is also designed because of the high penetration of DG.Moreover,the system structure,load parameters,integrated capacity and output characteristics of varies types of DG in different scenarios are described in detail.Finally,the simulation results,such as the time series power flow,reliability evaluation and hosting capacity of DGs are given.The benchmark test system proposed in this paper will lay a foundation for future research on distribution systems with a high proportion of DG and effectively support the distribution systems planning,design,operations and dispatches.

Structural and chemical engineering of metal-organic framework-derived nickel disulfide nanosheets as the compacted cathode matrix for lithium-sulfur batteries

Lithium-sulfur(Li–S)batteries are recognized as promising high-energy-density storage systems.It is crucial to develop the compacted sulfur cathodes with high sulfur content and high sulfur loading for practical applications.The metal-containing nanosheets are promising cathode matrix to mediate the accompanying problems,such as low sulfur utilization,unavoidable polysulfides shuttling and poor rate performance.Herein,we develop Ni-MOF-based strategy to fabricate nickel disulfide nanosheets on the reduced graphene oxide surface(NSG).Benefiting from nanosheets structure,strong polysulfides affinity,high electronic conductivity and superior electrocatalytic effect of NSG heterostructure,the resultant electrode exhibits high electrochemical performance with 0.021%capacity decay per cycle in 1000 cycles.Remarkably,the electrode with 88 wt%sulfur content and 5.9 mg cm^(−2) sulfur loading delivers reversible capacity of 945 mA h g^(−1),areal capacity of 6.1 mA h cm^(−2) and volumetric capacity of 997 mA h cm^(−3) at 0.5 C,which is comparable with the state-of-the-art those in the reported energy storage systems.This work provides methodology guidance for the development of cathode matrix to achieve high-energy-density and long-life Li–S batteries.

KPI-based Real-time Situational Awareness for Power Systems with a High Proportion of Renewable Energy Sources

With the increasing complexity of power systems and the widespread penetration of renewable energy sources(RES),real-time situational awareness for power systems is of great significance for operational scheduling.Considering the impact of RES on power system operations,a situational awareness key performance index(KPI)system for power systems with a high proportion of RES is proposed in this paper,which consists of reserve capacity abundance,ramp resource abundance,center of inertia(COI)frequency deviation,interface power flow margin,synthesized voltage stability,and angle stability margin.Then,the KPIs are synthesized and visualized by the decision tree method and radar chart method,respectively,for monitoring the operation states(i.e,normal,alert,and emergency states)of power systems with a high proportion of RES.Numerical simulations are conducted in a revised New England 16-machine 68-bus power system and an actual CEPRI-RE power system in the northwest region of China with a high proportion of RES.The results show that the proposed KPI-based situational awareness method is able to accurately monitor the real-time state of power systems with a high proportion of RES,and can assist power dispatchers to make effective decisions.

Wind power forecasting error-based dispatch method for wind farm cluster

With the technical development of wind power forecasting,making wind power generation schedule in power systems become an inevitable tendency.This paper proposes a new dispatch method for wind farm(WF)cluster by considering wind power forecasting errors.A probability distribution model of wind power forecasting errors and a mathematic expectation of the power shortage caused by forecasting errors are established.Then,the total mathematic expectation of power shortage from all WFs is minimized.Case study with respect to power dispatch in a WF cluster is conducted using forecasting and actual wind power data within 30 days from sites located at Gansu Province.Compared with the variable proportion method,the power shortage of the WF cluster caused by wind power forecasting errors is reduced.Along with the increment of wind power integrated into power systems,the method positively influences future wind power operation.

Analysis on Application of a Current-source Based DFIG Wind Generator Model

Models for simulation are vital for the authenticity of the simulation.Modeling doubly fed induction generation(DFIG)for power system stability analysis has attracted a great deal of research interests in the past few years due to the wide applications of DFIG in wind power generation.The models developed by the wind generator manufacturers are not only complicated,but also proprietary and very specific to their own products.Many simplified generic models have been proposed.Among them,the current-source based model is most widely used for power system stability analysis.The validation work on this model so far has been based on the selected simulation scenarios or limited real measurements.However,there has been no systematic and theoretic analysis on the validity of the current-source based model,which may cause inappropriate applications of this type of model in real engineering practices.This paper presents the conditions for using the current-source based model for power system stability analysis;then examines the model’s validity under symmetrical and asymmetrical fault conditions.Our practices for modeling and validating a real wind farm in North China confirm the validity analysis of this work on the current-source based DFIG model.