Reliability prediction of relay protection devices is an important technical means to improve the inherent reliability performance of relay protection devices. The current reliability prediction mainly adopts the GJB/Z 299C standard and the U.S. military standard MIL-HDBK-217, both of which consider each stress in a series model and do not consider the role of individual stresses on the overall failure rate, resulting in less accurate predicted values for the basic failure rate of components. Therefore, in this paper, a barrel theory analysis method is used to propose the calculation method of partial stress failure rate focusing on the failure mode of aluminum electrolytic capacitors on power supply boards, and a common coefficient to evaluate the interaction between each stress is given. The prediction results are also compared with the traditional reliability prediction standards, and it is found that the failure rate of aluminum electrolytic capacitors is greatly improved, and the life of relay protection devices is shortened to 12 years under normal environment and 6 years under the worst environment, which is consistent with the statement in the "Regulations for the Operation and Management of Microcomputer Relay Protection Devices" that the service life of re-lay protection devices should not be less than 12 years.

This paper mainly studies the model of electrolytic aluminum load and analyzes the regulation characteristics of the electrolytic aluminum load. Firstly, the electrical characteristics of the electrolysis cell, on-load tap-changer (OLTC) transformer, rectifier transformer and saturation reactor are analyzed, and the model of the electrolytic aluminum load system is established. Then, the control characteristics of the electrolytic aluminum load are studied, and a coordinated constant current control strategy of OLTC and saturation reactor is proposed, and the regulation capability of the electrolytic aluminum load is analyzed. Finally, a case of an electrolytic aluminum load is used to verify the proposed method. The results show that the method proposed in this paper can effectively improve the steady-state characteristics and regulation ability of the electrolytic aluminum load.

Driven by carbon peaking and carbon neutrality goals, sending-end power systems with high proportion renewable energy will become an important form of the future transmission grid. In order to solve the problem of insufficient and uneven inertia distribution of high proportional renewable energy system, this paper proposes an inertia configuration method for sending-end power systems with high proportion renewable energy based on frequency response characteristics. The method partitions the system to be studied according to the consistency of frequency response characteristics firstly, and then calculates the inertia demand of each partition and configures it according to the maximum unbalanced power of each partition. Finally, the effectiveness of the proposed inertia partitioning configuration method is verified in the modified IEEE 39-bus system.

The current development history of the drive-by-wire chassis is summarized, the composition and principle of the driveby- wire chassis are introduced, and the steering-by-wire system, the composition, working principle, control method and research status of the drive-by-wire system are analyzed in detail. The key technologies affecting the development of the drive-by-wire chassis are summarized, and the multi-sensor fusion positioning technology, fault-tolerant control technology, and vehicle wireless communication technology are reviewed.

针对单相感应电动机(SPIM)的非对称主、副绕组结构,提出了基于通用三相输出变频器的自整定优化变频调速控制方法.通过系统初始化,对定子绕组等效阻抗进行离线辨识,确认主、副绕组匝数比;再步进调节输出电压相位差,检测电流响应,搜索使主、副相电流与匝数成反比的最优输出电压相位差整定值,从而使变频器能够根据所控制的电动机自动优化输出电压的调制波形,保证生成圆形旋转磁场,驱动电动机平稳与高效运行.用多台参数差异较大的单相电动水泵进行了实验验证,结果表明自整定过程简单、性能良好,水泵运行稳定,扬水效率提高,并已在光伏扬水逆变器产品中得到应用.

新一代高频隔离级联式中高压变频器取消了传统的工频变压器的使用,并减少了全控型开关器件的数量,提高了系统的功率密度.在实际应用中常常存在负载不平衡以及电网不平衡等问题,因此提出了一种整流-逆变级双星型交错连接以及隔离级变换器的多绕组共铁芯变压器的新型结构方式,从系统协调的角度解决不平衡状况导致的直流电压不平衡的问题以及实现故障隔离.详细分析该结构拓扑的功率传输特性,最后,搭建仿真验证了所提结构的可行性.

This paper proposes a transient stability constrained optimal power flow model of VSC-MTDC transmission system. Using the concept of transient stability margin based on phase-plane trajectory concavity-convexity, the transient stability constraints are converted to generator active power constraints. Combined with the traditional optimal power flow model and constraints of VSC-MTDC system, the transient stability constrained optimal power flow model can be established. The optimization procedure is also given. According to the desired value of transient stability margin, the optimal generator active power output can be determined. The simulation results in the modified New England 39-bus system validate the effectiveness of the proposed method.

随着可再生能源大量接入电网,其间歇性不稳定的出力特征对电网频率稳定提出了严峻挑战.电动汽车作为可控负荷,能够组成需求侧能效电厂参与系统辅助服务,为电网提供频率调节服务.为此,提出了一种基于电动汽车能效电厂的系统频率控制策略.首先,构建了单体电动汽车的可控域,用于判断汽车能否参与频率控制;其次,定义状态标识SOB (state of battery)来描述电动汽车的响应容量;最后,提出了基于SOB排序的频率控制策略.仿真结果表明,所提出的控制策略能够有效抑制风电出力造成的电网频率波动,同时满足电动汽车用户的交通出行需求.

针对海上风电场(OWF)经由电压源换流器型直流输电(VSC-HVDC)接入陆地电网的情景,提出了一种海上风电场陆地接入点的选择策略.该策略是在由系统规划者确定的多个备选接入方案中进行选择,这些备选接入方案能满足风电有功功率有效送出等要求.所提出的选择策略主要考察备选方案对陆地电网电压特性的影响.选择策略分为3步:(1)提出3个影响因素,分别为:岸上VSC换流站的交流电压支撑能力、由风电功率波动引起的岸上交流电压波动、VSC-HVDC输电系统的建造成本;(2)提出了与3个影响因素对应的评价公式;(3)针对这个多目标决策问题,建立一个线性加权模型,基于信息熵理论和层次分析法(AHP)获取各个指标的权重系数.使用PSS/E在中国浙江电网中进行仿真分析,结果表明,在最佳方案下,接入区域能在各个关键故障下保持电压稳定,说明该选择策略能够有效地选择海上风电场的接入点.

针对半波长输电中的几个原理性问题展开研究,包括稳态运行时的工频过电压问题、故障引起的工频过电压问题、静态功角同步稳定性问题和暂态功角同步稳定性问题等.文中首先建立了适用于稳态和暂态分析的远距离输电系统等效电路模型,模型中考虑了送端系统和受端系统.为方便描述系统特性,给出了一个采用实际线路参数的测试系统.基于等效电路模型,推导并计算了系统的谐振输电距离.之后,通过理论分析和数值计算寻找系统的可行输电距离范围.结果表明:在考虑暂态频率偏差的情况下,为满足稳态过电压和小干扰稳定性的要求,系统的输电距离应在大于谐振输电距离的一定范围内.当输电距离在上述范围内时,线路中某一特定点的三相短路故障会导致最严重的暂态工频过电压,同时系统很可能失去同步稳定.由于暂态工频过电压和暂态稳定性的约束,半波长输电系统不可能实际运行.

送端电网采用直流孤岛运行方式,能有效解决大容量直流双极闭锁后大规模潮流转移导致的交流主网暂态稳定问题,但缺陷是送端系统自身的短路比和等效惯性常数较联网时显著减小,承受扰动能力较弱,因此,定量评估这类直流孤岛送电系统的强弱对直流工程的规划与运行具有重要指导意义.基于直流孤岛送电系统等效模型,考虑发电机电压调节器的作用,详细阐述了不同时间尺度下送端交流系统的戴维南等效电压源与等效阻抗的取值原则,并在PSCAD/EMTDC中搭建简化系统验证其正确性.在此基础上,提出了交流系统暂态阻抗、交流系统稳态阻抗以及等效惯性常数3个指标,分别用来描述直流孤岛送电系统的暂态过电压水平、直流功率输送能力以及频率暂态性能.3个指标可以直观体现直流孤岛送电系统的一些运行特性,从而实现对直流孤岛送电系统强弱的定量评估.

This paper focuses on the control strategy of a VSC-HVDC system supplying power to offshore platforms consisted mainly of induction machines together with diesel engines. The offshore platform VSC emulates the dynamic behavior of a synchronous generator as well as the governor and field regulator to render similar voltage and frequency regulation. The utilization of droop control of dc voltage couples the frequency of onshore and offshore systems, so that the inertia of the offshore platform can be increased. Finally an equivalent of an offshore platform system is simulated in DIgSILENT/PowerFactory to validate the proposed control strategy. The simulation compared the dynamic response of the system with the proposed control strategy and with the conventional control strategy in some operation scenarios such as motor starting, load disturbance, onshore system faults and offshore system faults. The results show that the offshore platform system operates more stably and reliably with the proposed control strategy.

Aiming at non-parallel AC/DC systems, this paper studies the mechanism in system structure for HVDC power modulation to suppress low frequency oscillation. Through the equivalent circuit analysis of a typical non-parallel AC/DC system, the key factor that influences the HVDC modulation effectiveness is revealed. The paper introduces the extended residue ratio as the selection rule for the input signal of the HVDC supplementary controller. The design method for the HVDC supplementary controller is presented based on the phase compensation of the residue. Finally, a case study and an actual project study in China Northwest Power Grid are presented.

分析了在基于电力系统仿真软件(PSS/E)实现含统一潮流控制器(UPFC)的电力系统潮流计算和动态仿真的过程中,常规含UPFC的潮流计算方法存在的问题,提出了一种两阶段的含UPFC的电力系统潮流计算方法,并在PSS/E中对所提出的含UPFC的潮流计算方法进行了验证.

Compared to the existing strategies of AC transmission line expanding conversion, the strategy of conversion AC transmission lines to DC transmission lines(AC-to-DC transmission lines conversion) can update the transmission capacity of the existing line to the maximum, which has good application prospect. We discuss the AC-to-DC lines conversion technique from three aspects, that is, the overhead line conversion, the cable line conversion, and multiple line conversion. For the overhead line conversion, several aspects about the operation characteristic, the topology structure, the transmission capacity, etc. of the tripole structure based HVDC(TPS-HVDC) and the three-wire bipole structure based HVDC(TWBS-HVDC) are described generally. In terms of the cable line conversion, the symmetric and asymmetric modulation methods are proposed, and two feasible topology structures are presented, which are the tripole type square wave AC(TPT-SWAC) and the three-phase bipole type SWAC(TPBT-SWAC). And for the variable resistor in the TPBT-SWAC, its resistance distribution scheme is studied and a general formula for resistance calculation is obtained. For the multiple line conversion, the multi-terminal HVDC structures based on TPS and TPT-SWAC or TWBS and TPBT-SWAC which are constructed from multiple lines are depicted. According to analysis, TWBS and TPBT-SWAC are more suitable for the multi-terminal HVDC than TPS and TPT-SWAC. The key technology for AC-to-DC lines conversion is analyzed from different aspects and different levels. The research and analysis results indicate that the existing and new proposed topologies play a role in promoting the study of AC-to-DC lines conversion, which can provide wider technical ideas for the conversion and promote innovation and development in this field.

由于半桥逆变器具有结构简单,无需隔离变压器和输入电流能够实现正弦等优点,因此在单相不间断电源(UPS)中应用广泛.这里介绍了一种应用在单相UPS系统中的新型双开关AC/DC/DC/DC变换电路,分析了其工作模式和原理.给出正常工作模式和蓄电池供电模式下各种仿真及实验波形,证明了该电路简单可靠,输入功率因数高,电流谐波失真小,可获得稳定的正负直流母线电压.

提出恒电压运行的概念并论证恒电压运行是电网发展的终极目标.从恒电压运行的效益、恒电压运行的实现手段和恒电压运行的成本估计3个方面展开论述.恒电压运行的效益包括4个方面,分别为恒电压运行是坚强智能电网的终极表现形式;恒电压运行能够最大程度地抵御故障扰动并提高系统稳定性;恒电压运行可彻底解决大规模可再生能源接入电网引起的电压波动问题;恒电压运行可实现网损最小化.恒电压运行的实现手段主要是采用基于模块化多电平换流器技术的静止同步补偿器(modular multilevel converter based STATCOM,MMC-STATCOM),目前技术水平下单个MMC-STATCOM的合理容量为500 MVA.对一个具有2万knn、500 kV输电线路的受端骨干网架进行了恒电压运行成本估计,表明所需要安装的MMC-STATCOM容量在3 000万kVA以下,其投资成本在100亿人民币以内.

建立分布式电源优化配置的线性规划模型,该模型以改进的综合负荷指标和全网有功网损增量作为目标函数,采用节点有功功率和无功功率的增量为待优化变量,约束条件均为增量表达形式.结合系统潮流方程线性化后的灵敏度矩阵,目标函数和约束条件均可写为带优化变量的线性表达式,从而使得分布式电源优化配置问题转化为线性规划问题,该问题可采用内点法进行求解.通过典型33节点系统的不同场景对该方法进行测试,结果表明该方法可通过优化配置分布式电源提高系统电压水平并减少系统有功网损.

The use of thyristor converters in existing tripole high voltage direct current (HVDC) transmission system suffers some inherent defects similar to those of the traditional HVDC transmission system. For this reason, this paper proposes an improved scheme which uses the modular multilevel converters (MMCs) based on full bridge sub-modules (FBSMs) to replace the thyristor converters in pole 3, and the converters in pole 1 and pole 2 are also replaced by the MMCs based on clamp double sub-modules (CDSMs). Meanwhile, the coordination control between the three poles is proposed. In order to suppress the transient overvoltage and minimize the grounding current and power fluctuation in the transition process, the voltage inverse control, power coordinated control and the control strategy of keeping current zero in pole 3 are also proposed. The performance of the proposed tripole HVDC transmission system is validated through time-domain simulation study in PSCAD/EMTDC. The results show that the tripole HVDC transmission system based on the proposed control strategy can achieve a satisfactory response characteristic, while maintaining the balance of capacitor voltage and minimizing the grounding current and power fluctuation. ? 2014 State Grid Electric Power Research Institute Press.