In recent years, there have been many incidents around the world in which wind turbines were cut-off on a large scale due to severe wind conditions, resulting in huge impacts on the power system and seriously affecting the safe and stable operation of the grid. Accordingly, this paper proposes a novel wind turbine control strategy to maximize the load capacity in severe wind conditions, which can track the wind conditions and adjust the wind turbine load in real time to make full use of the transient survivability and power output capacity of wind turbines. Through simulation, it is confirmed that the proposed strategy can effectively reduce the risk of power steep drop in wind farms under severe wind conditions compared with traditional strategies.

在过风速工况下,现有的风机紧急控制策略极易造成风机大规模脱网,风能资源得不到充分利用.对此,提出一种基于等效载荷二维寻址的风机优化应急控制策略,该策略在保证风机本体安全的前提下,可实现过风速工况下风机输出功率平稳降低,避免剧烈的过渡过程导致电网安全问题.首先,分析在恶劣风况下风机的运行特性,建立风能利用系数与推力系数之间的数学关系式,并且推导风能利用系数对风机运行特性的影响;在此基础上,利用实时风速计算风机机械部件的等效载荷,并基此提出基于二维寻址的风机优化应急控制策略;最后,搭建风电场运行综合仿真平台,在不同运行场景下对所提的风机应急控制策略的适用性和优越性进行验证.

The peaceful development and utilization of pelagic island occupy vitally important position in the maritime development. For the rich resource islands that support the load center island by shipping, the efficient operation of off-shore renewable energy absorption facility (REAF) is of vital importance. Focusing on this issue, the hydrogen electrolyzer containing multiple energies (battery, hydrogen and cool) is designed in this paper. This design promotes the energy absorption efficiency of REAF significantly. On the other hand, the flexible-size decision tree pruning (FSP) and improved reinforced learning Monte-Carlo method (IRLMCM) are proposed in this paper, and the hierarchical dispatch strategy of REAF based on the above algorithms is designed. Case studies show that the dispatch strategies of REAF proposed in this paper can improve the energy absorption ability significantly. At last, the possible improvement methods of the dispatch strategies of REAF are discussed in this paper.

Under the current wind turbine control strategy, wind turbines are cut off to guarantee their safety for wind speeds exceeding 25 m/s. However, under severe wind conditions, power grids with high wind power penetration will suffer a catastrophic consequence due to the large-scale cut-off of wind turbines. To solve the problem, mechanical effects on a wind turbine from the aspect of airflow are analyzed in this paper; a numerical connection between the thrust coefficient and the wind power coefficient is proposed. On the basis of those analyses, the accumulated load on the blades and the tower of the wind turbine are analyzed, and a cohesive control strategy is proposed. The strategy uses real-time wind speed data to calculate the mechanical load on a wind turbine and realizes the maximum active power output under severe wind conditions. The results of case studies verify the effectiveness and superiority of the proposed strategy.

对于难以与大电网连接的偏远地区,如仅采用光伏发电,电网安全运行压力大,大规模弃光难以避免.含储热的光热电站具备良好的调度特性,是一种适用于离网型综合能源系统的电力供应形式.然而,相比于光伏,高昂的建设成本使得光热发电普及度有限.因此,该文提出含热电联供型光热电站与相变储能的离网型综合能源供给系统及其协调调度策略,背压式热电联供机组可以有效提升光热电站的综合能量产出效率,建筑相变储能的储热/冷能力则能够松弛机组自身的热电比约束,在满足系统综合能源需求的前提下,提高各机组的运行经济性,以降低综合能源系统的运行成本.算例仿真验证该文所提能源供给模式及协调调度策略的可行性与有效性.

远洋海岛远离大陆,现有研究考虑利用风、光等可再生能源进行远海海岛的能量供给,但并未考虑远洋海岛土地资源紧张等问题。针对这些问题,文中在充分评估海岛及其周边礁盘区域场景中风/光/波浪能资源状况的基础上,基于无桨叶风机、漂浮式太阳能电池板以及振荡浮子式波能捕集装置,提出了多能源礁盘电站的一体化建设布局方案。在等年值投资成本和布局约束下,以年总发电量最大为目标函数,建立布局优化和发电潜力勘探混合整数规划模型,利用CPLEX对模型算例进行求解,并与不同精确度下穷举法的计算结果进行对比。算例结果表明,所提建设布局方案合理可行,其发电潜力较大,能较为充分地满足对远洋海岛的电力供应,同时尽可能避免了对海岛土地的过多占用。

针对大型离网海岛供电系统的建立,提出了包含电网方、新能源发电系统方和储能系统方的供电策略,利用峰谷电价机制和出力惩罚机制引导新能源发电系统方和储能系统方合理运行,并设置储能系统SOC控制方式.在这一策略的基础上,该文建立新能源发电系统方与储能系统方的新型电能交易非合作博弈模型,研究各参与方的容量配置问题.在纳什均衡解存在的基础上,利用粒子群算法,基于最优反应分析策略,迭代搜索找出各参与方容量配置的纳什均衡点.基于均衡点,对各参与方的收益支出进行经济性分析.供电策略的提出和博弈模型的建立,既能提高新能源的渗透率,一定程度上解决新能源机组出力与负荷需求不平衡的问题,同时也能保证各方的收益,有效提高投资方参与投资建设新能源机组和储能系统的积极性,具备一定的现实意义.

目前面向min级风电柔性并网的储能系统一般由蓄电池组成,因蓄电池配置容量有限,在应对风电场长过程连续下调峰导致的风电功率波动越限问题时,其控制效果将大打折扣。为此,引入容量在日内调度可近似视为不受限的氢储能系统,与蓄电池共同组成混合储能系统,并基于其各自特点,设计了最大发挥2种储能优势的混合储能系统,建立混合储能协助下的风电场并网状态空间模型,并求解可实现风电场柔性并网最小化能量转换损耗的混合储能系统最优充放电功率决策,根据决策执行结果分析混合储能系统的能量转换特点。仿真结果表明,与采用单独蓄电池储能的控制策略相比,在相同的储能系统配置成本下,提出的优化模型可以结合氢储能系统的能量容量优势来提高储能系统的供电持续性,并且能够合理安排蓄电池和氢储能系统的工作顺序来尽量减小风电场能量损耗,由此实现相对最优的风电场柔性并网功能。

现有远洋海岛屿电网之间缺乏有效的联络,仅采用海底电缆的互联方式,工程可行性与经济性欠佳.因此,该文提出采用换电船舶(power exchanging watercraft,PEW)电能输运航路代替部分海底电缆的形式,构建远洋海岛群混合电能的传输网络.首先建立PEW航路电能传输模型,分析其能量传输效率与成本;然后结合多场景生成及聚类方法,以网络综合成本最小为目标,并计及极端气象场景下电能网络的额外供电成本,建立含PEW航路混合电能传输网络的规划模型,并采用混沌引力搜索算法优化求解,仿真结果验证了所提方法的可行性与有效性.

针对远洋海岛自治微网的负荷备用问题,提出基于概率性序列运算的双重化备用电源规划方案。首先,建立风机、光伏发电和负荷的概率分布函数模型,利用概率性序列运算方法求取电力不足概率这一可靠性指标。接下来,根据微型燃气轮机和柴油机各自的特性及相关的配置和燃料成本高低,研究最大化利用2种备用机组优势的备用策略。最后,结合远洋海岛资源补给及孤岛运行的实际情况,以最大程度满足可靠性为前提,求解备用机组及储气站的最优规划容量。仿真结果表明,所求解的机组及配套设备能够满足岛上日常以及极端天气的备用功能。与其他策略的对比分析表明,在考虑负荷惩罚因素后,该文提出的策略具有更优越的经济性。

Due to its high sensitivity and fast operation rapidity, zero-sequence differential protection (ZSDP) has become the most frequently used main protection for EHV and UHV power transformers. It is generally assumed that extra restrain criterion is unnecessary for ZSDP since it is immune to the magnetizing inrush current in theory. However, it's found that the bias of zero sequence current in converter transformer due to core saturation may lead to the accumulation of magnetic bias within the core of CT, especially during external fault removal period. This may lead to the mal-operation of ZSDP. Based on the Hausdorff graphics recognition algorithm, an extra restrain criterion for ZSDP is proposed in this paper. Verified by simulation and theoretical analysis, the proposed criterion will not influence the performance of traditional ZSDP. However, the proposed criterion can correctly identify the fake differential current and effectively prevent the mal-operation of ZSDP caused by the recovery inrush.

独立海岛交直流微电网(independent island hybrid microgrid,IIHM)能有效解决海岛供电难题,但可再生能源出力的波动加剧了交直流子微网的功率不平衡情况,导致功率在传输变换过程中产生较大损耗。因此,该文设计了一种交直流无刷双馈风力发电机(hybrid brushless doubly-fedinduction generator,HBDFIG),通过主动调节发电机转速与控制绕组电流频率,可在发电侧将功率按一定比例直接分配到交流与直流子微网。在此基础上,以保障负荷全部供电为前提,以消耗海岛内发电燃料最少为目标,提出了含HBDFIG的IIHM优化发电调度策略。算例结果表明HBDFIG及其优化发电调度策略可减少功率在微网内的传输变换损耗,提高供电效率,延长常规燃料补给周期,降低海岛微网综合运行成本。

由于远洋海岛无法获得大陆主电网的支持,且其常规机组的燃料补给线超长,传统发电配置方法并不能直接适用于对远洋海岛可再生能源发电机组进行配置和方案优选。对此类远洋海岛而言,储量丰富的可再生能源应作为建设绿色海岛能源供应系统的主要依托。该文基于全清洁化远洋海岛能量供给系统的拓扑特性与基本框架,并计及远洋海岛自然环境和功能定位,分别建立契合海岛可再生能源出力及负荷短时间尺度波动规律的概率模型。在此基础上提出的基于归一化积相关算法(normalized product correlation,NPROD)能有效支撑长时间尺度基础负荷、并能实现海岛能量供给系统出力/电量—负荷最佳匹配的可再生能源机组配置方案优选策略。最后,通过算例仿真验证所提配置方案优选策略的合理性和优越性。

恶劣风况下,风电场将因风机过风速保护相继动作而发生功率陡降甚至风电机组大规模脱网,严重影响电网的安全稳定运行.针对此问题,构建了风电机组的安全运行载荷约束条件,提出一种计及等效损伤载荷约束的黏性控制策略.所提策略能够在不改变风机原有机械控制系统的基础上,根据运行风况实时调节风机功率,追踪风机等效损伤载荷约束,使载荷维持在相应风况下的安全边界内,在充分利用风机的载荷承受能力的前提下最大化维持风电场功率输出,以实现降低恶劣风况下风电场功率陡降风险的目标.通过算例仿真与策略对比,验证了所提策略的有效性和优越性.

电动汽车行业的高速发展带动海上交通工具电动化的革命浪潮.将全电船舶用于可再生能源丰富的远洋海岛,可高效利用岛内清洁能源,推动远洋海岛经济的绿色可持续发展.但与此同时,全电船舶充电负荷的增长也给海岛微网的规划运行带来新的挑战.针对含高渗透率可再生能源的远洋海岛场景,提出兼顾电能质量与化石能源消耗的全电船舶充电站多目标规划模型,并遍历全电船舶充电站可能出现的所有规划方案,在此基础上采用多目标粒子群算法获得相应Pareto最优解集.仿真结果验证所提规划策略集合的合理性和有效性.

Zero-sequence differential protection has become one of the foremost protective countermeasures for EHV and UHV power transformers due to the advantages of high sensitivity and very fast operation speed. It is the common knowledge that it has no need to be equipped with extra countermeasure besides percentage restraint criterion since it is immune to the inrush in theory. However, according to the waveform analysis of the recovery inrush resulting from removal of external fault of converter transformer, it is disclosed that the current bias component due to core saturation of converter transformer may lead to the accumulation of magnetic bias component within the core of TA. In the extreme conditions, this would lead to the distortion of the current coming from TA, and make the zero-sequence differential protection mal-operate. According to the theoretical analysis and simulation tests, the risk of zero-sequence differential protection mal-operation resulting from the inrush due to fault removal does exist in some specific fault conditions. In this case, additional restraint countermeasures are necessary to guarantee the operation security of zero-sequence differential protection.

When high voltage direct current (HVDC)system operates in monopole ground return mode,DC current with high amplitude will penetrate into the earth via the grounding electrode. Such DC current can flow through the DC path which is composed of neutral-grounded transform-ers and the AC lines between transformers.It can increase the reactive power consumption as well <br> as occupy the capacity of reactive power compensation equipment in the substation,which can greatly threat the normal operation of the power grid.Thus,a simulation model of typical substa-tion system under DC magnetic bias condition was established with PSCAD software.By means of this model,a quantitative simulation analysis of the excitation current variation and the different condition of reactive power consumption under different biasing current inj ection were carried out. The simulation results show that,with the increase of the DC magnetic bias current,the excita-tion current suffers more serious distortion,and the consumption of reactive power increases more sharply,which will impact the voltage adj ustment and reactive power balance of power grid significantly .Moreover,this result is of significant reference value for researches on the reactive power characteristic of DC biasing as well as the support capability of short-circuit voltage under DC biasing condition.

As the "12th Five year development plan" of China is in progress, the new energy industry and tertiary industry has been developing rapidly, which sets a higher requirement for the power distribution network. In the foreseeable future, the connecting topology of civilian distribution network would become too complicated to the current protection method based on local information. Therefore, the multi-terminal differential protection which has a great operating experience in the main power network can be utilized to improve the performance of distribution network protection. However, attributed to financial affair, the communication system deployed on distribution network may not be as good as that on main network, which may lead to a time desynchronizing that would heavily influence the accuracy of multi-terminal differential protection. This paper introduced method that utilizes the optimal algorithm to calculate the possible error brought up by time desynchronizing, and verify it through computation examples of different kinds of conditions.

With the development of communication technology and artificial intelligence, the study of protection intelligent center is becoming the research focus. To make full use of the technology advance, the concept of protection intelligent center is proposed. The protection intelligent center is a remote center which can gather the electrical information of the whole network and give out tripping signals on the basis of analysis. In distribution network, the protection intelligent center could provide multiple protection with its local layer and center layer. This paper focuses on the cooperation method of different types of protection which protection intelligent center can participate in, and proposes a practical scheme which combines the protection deployed in local layer and central layer to reach an optimal protection performance. The protection method of the system proposed in this paper is complicated to achieve multi-space and multi-layer protection, so the verification of the protection cooperation is also provided in this paper.

Original last breaker protection based on arrester energy consumption characteristics might malfunction in light loaded power system. In this paper, we analyzes the relationship between the high side inlet voltage of converter transformer and the AC load, pointing out that the main reason of the arrester based last breaker protection maloperation is that the original protection strategy cannot distinguish light load state from isolation state of the AC line. This paper adds outlet head end voltage and output power to the original criterion, designs an improved one so that it can correctly distinguish what state the AC line and send the right signals for different action status. Simulate and analyze the act of original criterion and improved one in light loaded power system by using the simulation model which is built based on the actual operating parameters of Yunnan-Guangdong UHVDC project, validating the improvement of novel criterion.