Power management in co-phase traction power supply system with super capacitor energy storage for electrified railways

Increasing railway traffic and energy utilization issues prompt electrified railway systems to be more economical,efficient and sustainable.As regenerative braking energy in railway systems has huge potential for optimized utilization,a lot of research has been focusing on how to use the energy efficiently and gain sustainable benefits.The energy storage system is an alternative because it not only deals with regenerative braking energy but also smooths drastic fluctuation of load power profile and optimizes energy management.In this work,we propose a co-phase traction power supply system with super capacitor(CSS_SC)for the purpose of realizing the function of energy management and power quality management in electrified railways.Besides,the coordinated control strategy is presented to match four working modes,including traction,regenerative braking,peak shaving and valley filling.A corresponding simulation model is built in MATLAB/Simulink to verify the feasibility of the proposed system under dynamic working conditions.The results demonstrate that CSS_SC is flexible to deal with four different working conditions and can realize energy saving within the allowable voltage unbalance of 0.008%in simulation in contrast to 1.3%of the standard limit.With such a control strategy,the performance of super capacitor is controlled to comply with efficiency and safety constraints.Finally,a case study demonstrates the improvement in power fluctuation with the valley-to-peak ratio reduced by 20.3%and the daily load factor increased by 17.9%.

Traction power systems for electrified railways:evolution,state of the art,and future trends

Traction power systems(TPSs)play a vital role in the operation of electrified railways.The transformation of conventional railway TPSs to novel structures is not only a trend to promote the development of electrified railways toward high-efficiency and resilience but also an inevitable requirement to achieve carbon neutrality target.On the basis of sorting out the power supply structures of conventional AC and DC modes,this paper first reviews the characteristics of the existing TPSs,such as weak power supply flexibility and low-energy efficiency.Furthermore,the power supply structures of various TPSs for future electrified railways are described in detail,which satisfy longer distance,low-carbon,high-efficiency,high-reliability and high-quality power supply requirements.Meanwhile,the application prospects of different traction modes are discussed from both technical and economic aspects.Eventually,this paper introduces the research progress of mixed-system electrified railways and traction power supply technologies without catenary system,speculates on the future development trends and challenges of TPSs and predicts that TPSs will be based on the continuous power supply mode,employing power electronic equipment and intelligent information technology to construct a railway comprehensive energy system with renewable energy.

New generation traction power supply system and its key technologies for electrified railways

Unlike the traditional traction power supply system which enables the electrified railway traction sub- station to be connected to power grid in a way of phase rotation, a new generation traction power supply system without phase splits is proposed in this paper. Three key techniques used in this system have been discussed. First, a combined co-phase traction power supply system is applied at traction substations for compensating negative sequence current and eliminating phase splits at exits of substations; design method and procedure for this system are presented. Second, a new bilateral traction power supply technology is proposed to eliminate the phase split at section post and reduce the influence of equalizing current on the power grid. Meanwhile, power factor should be adjusted to ensure a proper voltage level of the traction network. Third, a seg- mental power supply technology of traction network is used to divide the power supply arms into several segments, and the synchronous measurement and control technology is applied to diagnose faults and their locations quickly and accurately. Thus, the fault impact can be limited to a min- imum degree. In addition, the economy and reliability of the new generation traction power supply system are analyzed.

A type of inverter power supply based on harmonic elimination PWM control

In order to output sine wave with small degree of distortion and improve stability,a type of inverter power supply is designed based on harmonic elimination pulse-width modulation(PWM)control.The rectifier and filter are added to input circuit of the inverter.Single-phrase full-bridge inverter performs the function of converting direct current into alternating current(DC/AC).In the control circuit,single chip micyoco(SCM)AT89C2051 is used for main control chip to accomplish the hardware design of the control system.A given value of output frequency of the inverter is input in the way of coding.According to the output frequency code which is read,SCM AT89C2051 defined harmonic elimination PWM control data which will be selected.Through internal timing control,the switches are switched under this provision of PWM control data.Then the driving signals of the switches in the inverter are output from I/O of SCM AT89C2051 to realize harmonic elimination PWM control.The results show that adding Newton homotopic algorithm of harmonic elimination PWM control to corresponding software of the control system can make the quality of output voltage of the inverter higher and it will have broad application prospects.

FPGA-based Digital Implementation of Flexible Power Control for Three-phase to Single-phase MMC-based Advanced Co-phase Traction Power Supply System

A three-phase to single-phase modular multilevel converter based advanced co-phase traction power supply(MMC-ACTPS) system is an effective structure to address the concerns of phase splitting and poor power quality of the conventional electrified railway. Due to the large number of MMCACTPS system modules, I/O resources and computing speed have high requirements on processors. Moreover, the module capacitor balance is challenging because the sorting time is too long when the traditional sorting algorithm for voltage balance is used. To solve the above issues, a digital implementation scheme of flexible power control strategy for three-phase to single-phase MMC-ACTPS system based on field programmable gate array(FPGA), which has sufficient I/O resources, has been proposed. Due to the parallel execution characteristics of the FPGA, the execution time of the controller and the modulator can be greatly reduced compared with a digital signal processor(DSP) + FPGA or DSpace. In addition, an improved sorting algorithm is proposed to reduce the sorting time and the implementation steps are analyzed. Finally, simulation and experimental results are presented to demonstrate the effectiveness and correctness of the proposed control strategy.

贯通同相供电系统建模及运行特性分析

贯通同相供电系统可以取消全线电分相,实现牵引网不间断供电,对贯通同相供电系统进行建模和运行特性分析能够为系统的设计和优化提供理论依据。构建同相牵引变电所模型;建立能够灵活模拟不同拓扑结构和不同运行状态的贯通同相供电系统的链式电路模型;针对模型高效求解和导线载流量校验需求,提出一种改进的导体电流间接求解方法;基于构建的模型对贯通同相供电系统在空载和负载工况下的运行特性进行分析。研究结果表明,三相电压不平衡度的计算值与理论值相等,验证了模型的正确性;与既有导体电流计算方法相比,改进的导体电流间接求解方法的计算精度无差异,计算时间缩短为原来的1/3;潮流计算能够充分反映贯通同相供电系统的穿越功率以及牵引网电压、电流等特性。

城市轨道交通贯通供电方式牵引网分段供电方案及故障辨识方法

[目的]城市轨道交通线路采用贯通供电方式时,因牵引网结构复杂且无备用,牵引网发生故障时可能会扩大停电范围,为此需要对牵引网的分段供电方案进行优化。[方法]提出了一种适用于贯通供电方式的牵引网分段供电方案。基于牵引网分段供电拓扑特征,结合车-网耦合特性,提出了分段故障、过渡段故障的辨识方法。对牵引网分段短路和过渡区短路2个故障场景的控制方案进行了分析,描述了这2个故障场景下牵引网的自愈流程,并制定了这2个故障场景对应的断路器控制方案。以广州地铁18号线牵引供电系统为例,通过MATLAB/Simulink软件仿真,验证了所提分段供电方案及故障辨识方法的正确性和可靠性。[结果及结论]该方法可有效辨识故障区段。牵引网故障断路器控制方案可为分段和过渡区提供可靠的主保护,可保证广州地铁18号线牵引供电系统稳定、高效运行。

考虑负荷供电连续性的孤岛配电网负荷恢复策略

上级输电网发生故障停运后,配电网可依靠分布式电源维持运行,当分布式电源出力波动难以平抑时,需要通过投切负荷来平抑波动,这会造成非重要负荷频繁投入或切出电网,产生大量单时段或双时段的短时供电场景,进一步降低了非重要负荷供电的可靠性。针对此问题提出一种考虑负荷供电连续性的配电网负荷恢复优化方法,从单个负荷角度出发,引入单负荷供电连续性指标构建目标函数,并计及潮流、网络拓扑、连通性等约束构建模型,使得非重要负荷也尽量连续供电,提高供电的连续可靠性。采用PG&E69节点配电系统作为算例进行验证,模型结果与传统恢复相比供电连续性显著提高。供电连续性参数的引入使得负荷恢复更加趋向于连续,大大减小了因为分布式电源波动而产生的短时供电问题。

A compact bimorph rotary piezoelectric actuator with customized small power supply

Inertial piezoelectric actuators are widely applied in precision devices with simple structure and accurate movement.However,existing inertial piezoelectric actuators still face the challenges of rollback motion and bulky power supply.In this work,an alternate excitation strategy and a customized small power supply for a bimorph rotary piezoelectric actuator(BRPA)are proposed to solve the problems.The BRPA prototype is designed with a bipedal symmetrical structure,measuring 35 mm in height and 32 mm in diameter,which has a maximum rotation velocity of 0.247 rad/s and a resolution of 0.66μrad.Thanks to the bipedal symmetrical structure,the friction directions between the driving feet and the rotor can be coordinated to suppress the rollback.The rollback ratio is almost zero when the phase difference of the exciting signal is set as 180°.The customized power supply is designed and manufactured,whose size is 58 mm×56 mm×46 mm.It can output signals for the single step mode and the continuous mode,and they are adopted to excite BRPA to achieve a small stroke with one single step and a large stroke with continuous step,respectively.Then,an experimental system for optical fiber alignment is developed based on the BRPA and the customized small power supply,the experiment has verified the practicability of this work in the precision fields,especially in the miniaturized precision systems.

老年人照料设施消防应急照明和疏散指示系统设计探讨

以老年人照料设施为例,对其中主要功能用房、走道等区域的消防应急照明和疏散指示系统设计要求进行分析,为设计同行提供一些设计思路。

持续供电下的医院配电增容方案研究

为了提升医院电力供应的可靠性和稳定性,满足日益增长的医疗服务需求,本文通过介绍持续供电下的医院配电增容方案研究,详细分析了工程概况、负荷预测与计算、变压器选择、高压室电气布置及配电房后台监控等核心内容。通过科学的负荷预测与计算,合理选择了变压器容量与数量,并优化了高压室的电气布置。同时,引入了配电房后台监控系统以实现智能化管理。研究结果表明,该配电增容方案能够显著提升医院电力系统的承载能力和应急响应速度,确保医院在各类情况下均能维持连续稳定的电力供应,为医疗工作的顺利进行提供坚实保障。

基于连续可导ESO的虚拟同步机控制策略

在高比例新能源接入的电网中,虚拟同步机技术被广泛应用,但当面对系统扰动时其稳定性较差,可能会存在电压过限、频率波动等问题。因此,为了提高电能质量,将扩张状态观测器引入虚拟同步机控制技术中,对扰动进行观测、估计与补偿,提高系统稳定性,从而在新能源电源波动及大功率负荷投切时得到更稳定的母线电压及系统频率。此外,进一步对扩张状态观测器中的分段函数fal进行矫正,提出一种连续可导的扩张状态观测器控制算法,免去运算过程中的判断环节,突出了“小误差大增益”的特点,并对算法进行稳定性分析和确定参数选择范围。仿真与实验结果验证了所提策略的有效性与可行性。

A级数据中心空调系统供配电探讨

以水冷空调系统为例,阐述A级数据中心空调系统的高压供配电系统架构,分析空调系统的供配电系统单点故障的解决方案、主机房空调风机“交叉”配电方式,介绍火灾时空调设备电源切除原则、双重电源中每路电源对应的供配电设备、母线槽、线缆的物理隔离。

一种高稳定大功率雷达电源系统的设计与实现

设计一种由主机、辅机和应急电源组成的电源系统,通过智能监测,以相互补偿的方式实现不间断供电。即使在全船电网失电或者主机故障停机等极端条件下,还能确保雷达等大功率通信导航设备得到可靠的交流供电。实测该电源的输入电压在AC90~280 V之间大幅变动下,电源输出可稳定为220 V±1.5%、输出电压谐波小于3%,雷达故障中电源占比从40%下降为5%,从而延长雷达重要部件的使用寿命,特别是能够满足工作环境相对恶劣,机动性要求高的舰船、渔船等船舶大功率通导设备工作需要。

考虑接触网-钢轨耦合关系及再生制动能量的新型电缆贯通供电系统电气特性

针对新型电缆贯通供电系统模型未准确反映接触网与钢轨之间的耦合关系、未考虑再生制动能量利用及环网加单边供电方案等问题,采用电流控制的电压源解耦方法反映接触网和钢轨之间的耦合关系,建立基于二端口网络的新型电缆贯通供电系统模型;在计算系统牵引网阻抗、电压损失及馈线电流的基础上,结合实际线路数据,提出3种电缆贯通供电方案,在不同运行工况下仿真分析各供电方案下系统的电气特性,并考虑再生能量利用设计牵引变压器容量,以达到降低牵引变压器容量和运营维护费用的目的。结果表明:新型电缆贯通供电系统在各种供电方案下的再生能量利用率均较高,普遍达到90%以上;在相同牵引变压器数目下,环网加单边供电方案电压损失、牵引网损耗等性能指标均优于单纯的环网结构;再生制动能量能够作为牵引变压器容量设计的参考因素。

超导储能连续脉冲电源ICCOS模块参数分析

半导体反向换流(ICCOS)技术是解决电磁发射用电感储能脉冲电源换流困难的一种有效方法。以用于高温超导电感储能脉冲电源的反向换流模块为研究对象,对超导电感储能脉冲电源的特点和ICCOS模块在脉冲电源中的工作原理进行分析,根据主开关(晶闸管)关断条件推导了ICCOS模块中电容器最小预充电压的选取方法,针对连续工作过程中的电容器最大电压值进行分析。为验证电容器最小预充电压和连续工作过程最大电压计算方法的正确性和有效性,将计算结果与电路仿真结果进行对比,并得出电容器最小预充电压和连续工作过程最大电压随电容值变化的趋势。计算和仿真结果都表明,随着ICCOS模块中电容值的增大,其最小预充电压和主开关的最大电压均呈现下降趋势,且下降趋势逐渐平缓。搭建小型实验平台,对主开关进行关断实验和连续放电测试,实验结果初步验证了分析结果的有效性。

市域铁路贯通同相供电系统继电保护方案配置

针对市域铁路高客流量、高可靠性的要求,对市域铁路采用贯通同相供电方式中的组合式同相供电+分区所双边供电方案进行研究。根据该方案拓扑结构进行数学建模,对牵引变电所高压侧及牵引网不同位置进行短路故障分析,以某市域线路为例,对系统中不同位置的母线发生短路进行仿真分析。研究得出以下结论:当牵引供电系统发生故障时,需配置牵引供电系统的保护方案;而电力系统发生故障时,电力系统继电保护装置的动作不会受到影响,因此,无需调整电力系统的继电保护配置,验证了理论分析的正确性。根据故障分析结果,在传统继电保护方案上进行改进,配置继电保护新方案以确保市域铁路实施贯通同相供电运行的安全稳定。

新型电缆贯通供电系统的保护方案

为解决新型电缆贯通供电系统的接触网和牵引电缆使用现有分段保护方案会误动作的问题,研究负荷电流对接触网电流纵差保护的作用机理,提出接触网采用故障分量电流纵差保护方案;并利用相量法分析空载情况下电容电流对牵引电缆现有保护方案的影响,通过在每个分段回路牵引电缆的首、末两端空载时并联电抗器,及负载时切除电抗器,实现电流纵差的保护.研究结果表明:接触网中的负荷电流由两侧牵引变压器一起供给是引起接触网电流纵差保护误动作的原因,而提出的采用故障分量电流构成的接触网短路保护不受双边供电下正常负荷电流的影响;空载情况下,电容电流会使牵引电缆末端电流较首端电流的幅值和相角发生变化,导致保护误动作,提出的牵引电缆首末两端并联电抗器的方法可以解决这个问题.

FHD磁力仪台站供电系统研究

供电系统的稳定性和安全性在一定程度上决定了FHD磁力仪的数据质量和连续率,从FHD磁力仪供电设备开始,试验了市电、UPS、充电控制器、蓄电池组组合模式,通过长期实验结果选取适合FHD仪的供电系统,并在此基础上设计了FHD磁力仪台站供电系统,长期试运行结果表明,此供电系统极大提高了台站维护效率,节约了维护成本,保障了数据质量。

重载铁路树形贯通式同相供电系统的运行状态

重载铁路树形贯通式同相供电系统能够最大限度降低线路中电分相带来的安全隐患,提升牵引供电系统再生制动能量直接利用率、供电能力和供电品质.为保障树形贯通式同相供电系统的良好运行,从均衡电流、供电能力、负序评估、故障分析及保护配置4个方面研究该系统的运行状态.构建不同拓扑结构下双边供电系统均衡电流评估模型,揭示重载铁路树形贯通式同相供电系统的外部电源构成方式;以某重载铁路树形贯通式同相供电改造方案为例,探究正常和故障运行工况下系统的供电能力以及系统对外部电网的负序影响;对该系统不同类型的故障进行分析,并提出保护配置方案.研究结果表明:相较平行双边供电,当两相邻牵引变电所变压器变比相同时,树形贯通式同相供电系统不会产生均衡电流;改造方案上、下行牵引网最低网压为22.74 kV,满足牵引网电压要求;设置组合式同相供电装置后,系统的三相电压不平衡度95%概率大值和最大值分别为1.20%和1.65%;相较于传统保护装置方案,所提保护配置方案能够确保牵引网停电区间最小.