The uncertainty of wind power poses great challenges to the cluster development and grid connection of wind power. The point prediction of wind power is difficult to meet the actual need of flexible planning of the power network. Regarding to the problem of interval prediction for long-term wind power of wind farms clusters, the D-vine Pair Copula-GARCH-t model based on cloud theory is proposed to predict the output range of wind farms. The GARCH-t model can accurately reflect the leptokurtic characteristics of prediction errors and thus improve the precision of wind power prediction. Meanwhile, the D-vine Pair Copula model effectively describes the correlation between the wind power of wind farm clusters. Based on such cloud model with the digital characteristics of expectation, entropy and hyper entropy, the interval wind power can not only reflect the randomness and fuzziness, but also describe reasonably the relationship between them. The interval prediction for wind power could provide a reference for planner to do the long-term planning of wind farms.

选取长三角地区4家不同装机容量的典型火电厂,模拟不同情景下发电权、排污权以及碳排放权的交易情况,寻求区域环境效益与经济效益共赢的优化配置方案.结果 表明,强控情景下,区域整体经济利润可达最高,为4.85×109元,比基准情景增加7.30％的经济利润,排放物的排放量也最低,SO2、NOx和碳排放量分别为1 246.02、3 169.78、18 319 500 t,比基准情景分别减排40.32％、4.34％、5.39％.相比发电权交易、排污权交易,火电厂未来应重点关注碳排放权交易.小装机容量机组关停、大装机容量机组多发电有助于实现区域的资源优化配置,达到经济效益和环境效益的共赢,但在初始分配、价格体系方面尚需优化完善、形成联动.

传统的确定性风险分析方法由于存在多种弊端,难以适应新形势下的输电网规划和方案评估,为了更加合理地管控输电网风险水平,基于概率性分析方法对输电网风险规划和评估等研究成果进行了综述。介绍了输电网中的安全、设备、结构、管理和市场等一系列风险因素及相应建模方法;从场景规划、随机规划、模糊规划和区间规划等方面,评述了考虑多种不确定因素的输电网风险规划方法;基于评估指标和方法,综述了近年来国内外考虑多种不确定因素的系统风险评估体系研究成果。在此基础上,结合高比例可再生能源、交直流混联、网源协调、需求响应和建模优化等研究热点,展望了未来考虑多种不确定因素的输电网风险规划领域中需要关注的问题。

In recent years, failure recovery after faults is concerned and discussed worldwide as an important and hot topic. Facing the challenge of heavy loads and ultra-high voltage transmission, it’s urgent to propose some solutions to enhance transient voltage stability for failure recovery. Therefore, a novel dynamic volt ampere reactive (VAR) planning methodology is proposed in this paper to help failure recovery and improve transient voltage stability after contingencies. First, a transient voltage fluctuation (TVF) index is proposed to evaluate transient voltage condition after faults. Then dynamic compensation sensitivity is presented for searching the best candidate locations. Following that, the dynamic VAR planning methodology based on an improved Tent chaos multi-objective algorithm is discussed in detail. There are two optimization objects in the optimization. One is to minimize TVF to enhance transient voltage stability for failure recovery. And the other optimization is to minimize dynamic VAR investment cost and operation cost. Finally, IEEE 39 power system and a practical power system are analyzed and discussed. The proposed dynamic VAR planning methodology can support enough reactive power for failure recovery. With the least SVC planning amount and the power loss cost, it can greatly decrease the system TVF index and enhance the transient voltage stability. It’s proved that the proposed dynamic VAR planning optimization is effective and helpful for safety operation of power system.

Improving the power supply capability and accommodation of DG (Distributed Generation) are the new objectives of expansion planning of future loop distribution network.Therefore,a multi-objective bi-level optimization planning model for distribution network is proposed,which considers the N-1 security and coordination between network and DG by introducing the safety assessment index of safe distance.The model takes the reformed feeders,new load locations and installation locations and capacities of DG as decision variables,and considers the transfer of system failure load and uncertainties caused by uncontrollable DG output and load fluctuations.According to the characteristics of the model,the stochastic problem is transformed into deterministic problems by multi-scenario technology,and then is solved by the hybrid strategy combining normal boundary intersection and dynamic niche differential evolution algorithm.The planning results considering N-1 security and coordination between network and DG or not are compared by case analysis.Simulative results show that,the proposed planning model can improve the DG penetration level,exploit the potential power supply capability of distribution network and postpone the upgrade of lines simultaneously,and the planning scheme realizes the comprehensive optimization of economic benefit and safety of distribution network,which is more applicable to short-term expansion planning of urban developed distribution network with slow load growth and scarce line corridors.

Against the background of the interconnected structures among substations in smart distribution network,this paper proposes a stochastic planning method for distribution network based on security distance to improve power supply efficiency and save investment cost.Firstly,the method and indices for N-1 security evaluation of the distribution network are described based on security region methodology.Secondly,the fault load restoration as well as uncertainties of time-varying load and distributed generator(DG)output is considered for the chance-constrained distribution network planning model, which aims to minimize the present value of total cost.Then,the hybrid solving strategy in conjunction with fuzzy C-means clustering and dynamic niche differential evolution algorithm is utilized to solve the model.Finally,compared with two available planning methods,planning results show that the scheme proposed can improve power supply efficiency of the original network and optimize system economy and security at the same time on the premise of N-1 security.The methodology is more suitable for short-term planning of urban developed distribution networks,which have the characteristics of slow load growth and scarce line corridors.

With the gradual increase of their penetration rates,the wind power and photovoltaic power have brought many challenges to the operation of power grid,especially its peak-shaving.Under the impetus of energy internet,more and more attentions are paid to alleviating the peak-shaving pressure by ESS(Energy Storage System).The research status of large-capacity energy storage technologies suitable for peak-shaving is summarized;with the ESS connecting mode as the breakthrough point,the ESS planning methods for centralized and distributed connecting modes are studied and induced respectively;the solvers of planning models are reviewed;and the key scientific topics for future research are discussed.

As penetration of wind power increases, impact of wind power fluctuations on reliability and stability of power system becomes more significant. Different countries have set distinct wind power fluctuation indexes for wind farms according to features of their own power systems. Under impetus of energy internet, it gradually turns into a hotspot of theoretical study and pilot engineering application to smooth wind power outputs with energy storage systems (ESSs) integrated to wind farms. At first, this paper summaries pilot project construction achievements of new energy storage technology. Then, ESS type selection is teased out. Subsequently, key technologies, including wind power smoothing strategy and power and capacity configuration, are reviewed. At last, key scientific problems to be studied in the future are discussed.

Since the existing planning model of distributed wind-turbine and photovoltaic generations DGs (Distributed Generations) does not take the N-1 constraint of main transformers and feeders into account,the obtained planning scheme may not satisfy the security requirement,for which,a multi-objective planning model with N-1 security is proposed for the siting and sizing of DGs.The method and indexes of N-1 security evaluation are introduced based on the security distance model.The quasi Monte Carlo simulation and singular value decomposition are adopted to generate the correlation sample matrix among wind speed,light intensity and load for improving the accuracy of planning results.The chance-constrained programming method is applied to build the DG planning model with the minimum annual comprehensive cost and the minimum security distance equilibrium ratio as its optimization objectives and the dynamic niche differential evolution algorithm,combined with the normal boundary intersection,is adopted to solve the model.Case results show the DG siting and sizing scheme obtained ensures the N-1 security and realizes the optimal system economy and security,proving the rationality and effectiveness of the proposed model and algorithm.

As multi-infeed HVDC greatly influences the safe and stable operation of hybrid AC/DC system,a method is proposed to quantitatively calculate the system voltage interaction factor and average voltage interaction factor between HVDC systems in hybrid AC/DC system.Furthermore,a reactive-power planning method considering the voltage interaction among HVDC systems is proposed,which takes the minimum voltage interaction as the objective of its upper layer while the minimum power-loss and minimum investment as the objectives of its lower layer.Simulation and analysis for IEEE 39-bus extended system show that the proposed reactive-power planning method improves the voltage stability of hybrid AC/DC system.

In order to quantitatively analyze the reliability level of the power system with UHV penetration,the reliability evaluation model for devices applied in generation and transmission system and UHV AC/DC power transmission system is established by using Monte Carlo simulation method,in which the derating operation state of UHV DC transmission system is considered.Then an overload correction method is presented by combining sensitivity analysis and linear programming,and new reliability indexes that closely relate to UHV are put forward.The example analysis of IEEE RTS-79 system verifies the accuracy of the proposed model.In the end,the model is applied to the actual system of a regional power grid in China,the reliability indices of the system under different scenarios are calculated,and the reliability level of the system with UHV AC/DC transmission system penetration is evaluated,which can provide reference for the operation of the actual system.

With the development of large-scale HVDC and increase of load demand,AC-DC hybrid system is gradually formed,which may bring some influences on static and transient voltage stability that can't be underestimated.As reactive power planning can enhance the safe and stable operation ability for power system,most researches on reactive power planning at present are only focused on planning schemes considering static or transient voltage stability.Therefore,integrated reactive power planning methodology considering static and transient voltage stability meanwhile for AC-DC hybrid system was proposed in this paper.Firstly,a transient voltage stability assessment index was defined and the candidate locations approach for reactive power planning was discussed.Then,the model of integrated reactive power planning methodology based on bi-level programming was presented to enhance static and transient voltage stability with the minimum reactive power investment.Finally,IEEE 39 extended power system and a practical power system was analyzed in detailed.It's proved that the integrated reactive power planning methodology is effective and practical.

随着经济的不断发展,新型设备对电网电能质量的影响越来越多,用户对电能质量的需求也不断多样化,因此对电能质量进行有效的综合评估非常重要.该文提出一种考虑指标不稳定性的电能质量综合评估方法,在概率统计均值法的基础上,用标准差对指标评分进行修正,同时运用主客观权重相结合的组合赋权法计算权重,最后用模糊合成算子进行计算得到最终的综合评估结果,为电能质量的治理提供参考.结合算例,综合评估了铁路供电系统的电能质量,证明了评估方法的可行性.

The study of building energy intemet,which is featured by integration of renewable energy and intemet information technology,will be the fundamental way to forge a green energy structure and improve energy efficiency.Firstly,this paper introduces the general research of energy internet at home and abroad,and indicates that electricity is the major energy form of energy internet and the smart grid is the carder.Based on that,the system architecture of energy internet is studied.Secondly,the situation of sophisticated network system that includes power network,transportation system and natural gas network is analyzed;coordinated planning of electrified transportation system and power network,coordinated planning of gas and power network considering various uncertain factors,combined heat and power network are proposed as the research emphases of energy internet.Finally,key technologies of energy internet are analyzed and future research directions are pointed out.

More benefits can be earned for wind farms integrated with a battery energy storage system(BESS)by improving the acceptance of wind power.Firstly,this paper proposes a double optimization model for battery energy storage system considering grid structure. The optimal configuration node, power, capacity of BESS are determined with the aim of incremental benefits maximization for wind and storage joint system compared with wind farms only considering system security constraints in the outer planning model.The benefits maximization of wind and storage joint system is chosen as the objective function,and the output of generating units,wind farm,BESS as decision variables.In the constraints,power balance,spinning reserve, power and capacity of BESS are considered in the inner optimization model. A numerical optimization algorithm,which is based on an improved empirical competition algorithm is proposed to calculate the model. Finally,the validity of this model is verified in an improved IEEE 1 18-node system.Case results suggest that the best configuration of BESS can increase wind farm benefits,meanwhile both benefits increments and the improvement of abandoned wind show an increasing trend with reduction in investments or the increase in grid price.Furthermore,an appropriate initial capacity of BESS is able to improve the benefits of composite BESS and wind generation system.And on the premise of guaranteed convergence,the improved empirical competition algorithm can effectively increase the computing speed compared with the traditional one.

Owing to the variations of loads and sustainable energy, the power injections and the load increment direction are of uncertainties, which pose great challenges to the traditional models of power system operation. To determine the effects of those uncertainties on the reactive power reserve (RPR), an interval optimal RPR dispatch with generator rescheduling (GR) is formulated. To evaluate the RPR interval more comprehensively, two sub-models, namely the optimistic and pessimistic sub-models, are built. The proposed method is applied to several IEEE systems to illustrate its effectiveness. Case tests show that, proper GR schemes can enhance the RPR of power system by postponing the limit hitting of the generator reactive power. The obtained RPR scheme shows better robustness to the uncertainties of power injections compared with that of the conventional RPR dispatches, and the restriction on the RPR interval widths also suggests the operating risk reduction.

With dynamic voltage supporting ability, generator reactive power reserve can maintain bus voltage stability when disturbances occur in power system. It is generally recognized that generator reactive power reserve plays a vital role on the improvement of system voltage stability. The amount of reactive reserves at generating stations is a measure of the degree of voltage stability. Concepts and assessing methods were summed up in this paper. Optimization models were fully discussed and solving algorithms were classified with evaluations. Problems of generator reactive power reserve's research were proposed. Meanwhile, suggestions and key directions of further research were proposed from the author's point of view.

With the development of UHV (Ultra-High Voltage) transmission, great changes have occurred for the reactive power distribution. Especially the reactive power of UHV transmission varies with the different transmission power. Therefore, reactive power optimization considering penetration reactive power is presented in this paper. The estimation of the penetration reactive power is proposed in the paper. The optimization scheme can minimize the penetration reactive power of the UHV transmission and hence the voltage stability margin of the whole power system with UHV transmission. And the optimization is solved based on improved differential evolution algorithm. An example of Huadong power grid is discussed and analyzed. And it's proved that the present optimization control is effective and pratical.

为客观评价天然气电厂的功能,在充分考虑了天然气发电机组启停迅速、运行灵活、清洁环保的基础上,该文提出了天然气电厂综合效益的概念以及综合效益的整体模型评估方法,该方法通过有等效替代原则设计原始方案与替代方案,对两方案在满足相同的静、动态任务约束下采用机组组合进行运行模拟,两方案的运行成本之差即为天然气电厂的综合效益.77机系统和某实际发电系统规划的算例结果符合实际,验证了天然气电厂综合效益的存在,并分析了产生综合效益的机理以及影响因素.

目前风储联合系统综合效益评价方法多基于某一给定风电功率断面,忽略了风电出力的不确定性,导致评价结果与储能系统配置方案的局限性.为此提出一种计及风电出力不确定性与电网调峰能力限制的风储联合系统概率综合效益评价方法,利用风电功率预测误差反映风电出力的不确定性,可给出风储联合系统概率综合效益与储能系统最佳配置方案参考值.基于实际系统参数设计了算例,算例分析结果表明,风电预测出力下效益评价结果仅为给定预测误差分布下特定置信度的概率综合效益,而所提方法通过置信度量化风电出力不确定性带来的评价风险,可得到不同效益评价标准(置信度)下储能系统配置方案参考值.