A fast power control method based on high-speed communication for the continuous co-phase traction power system

Continuous co-phase traction power system is an effective method to eliminate neutral sections and provide high quality power for both the public grid and the catenary.The substations have the ability to provide cooperative support to each other to reduce capacity and improve system reliability.A fast power control method for substations is needed due to rapid load changes and low overload capability of the system.This paper proposes a fast power control method based on high-speed communication between substations,with additional transient power control to significantly improve the dynamic response of the system.

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%.

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.

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.

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.

电气化铁路贯通供电系统穿越功率的治理措施

为消除牵引供电系统穿越功率的影响,同时兼顾再生制动能量利用,提出一种穿越功率治理的新方法.首先,结合贯通供电系统结构推导不同工况下的功率潮流,分析穿越功率检测方法;其次,在单相组合式同相牵引变电所的基础上,设置功率转移与能量储存单元,分析改进后系统的工作机制;然后,通过功率分配与负序满意补偿的上层控制策略和变流器控制的底层控制策略相结合,提出穿越功率治理协同控制策略;最后,以某线路试验数据为例计算穿越功率大小,评估治理措施的经济性,同时通过仿真验证所提方案的正确性和有效性.研究结果表明:本文所提出的系统及其控制策略能够有效消纳穿越功率和再生制动能量,在考虑牵引变电所和牵引网损耗的情况下,功率转移与能量储存单元的穿越功率利用率在70%以上,具有良好的经济性和可行性.

基于机会约束的贯通式同相牵引供电系统分布式优化运行策略

贯通式同相牵引供电系统实现了电气化铁路“源-网-储-车”灵活运行,然而列车负荷功率不确定性强与集中式调度同步性要求高,使得系统内多牵引所协调运行面临巨大挑战。该文首先基于储能、潮流控制器运行特性,构建多座牵引所构成的贯通式同相牵引供电系统数学模型;其次,以牵引负荷功率为随机变量,形成刻画运行不确定性的潮流机会约束条件,采用场景法将机会约束转化为确定性约束求解,以电压不平衡补偿、系统安全运行边界为确定性约束,提出以日电费成本最低为目标的多牵引所协同随机优化方法;进而,基于同步型交替方向乘子法,以分区所节点为潮流耦合点,对贯通式同相牵引供电系统进行解耦和分布式求解。算例结果表明,所述方法实现了牵引所间的完全分散自治,各牵引所日电费成本降低超20%。

组群贯通供电方式牵引变电所进线继电保护方案研究

针对组群贯通供电,分析其牵引变电所电源进线牵引侧的故障类型和继电保护配置。对于进线牵引所侧来说,当发生各种类型短路故障时,电网侧提供的短路电流受到牵引变压器限制;通过接触网绕送的短路电流受到接触网阻抗限制,牵引侧的短路电流一般较小。进线发生各种单相和相间短路,差动保护均能启动。如果无法安装纵联差动保护,当单相牵引变压器连接在电源进线AB相间时,应配置低电压启动的A相和B相功率方向保护,其中A相功率参考正方向由牵引变压器指向进线;B相功率方向参考正方向由进线指向牵引变压器。

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。

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。

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。

旧区改造新建综合医院楼电气设计

依托某旧区改造新建综合医院楼项目,分析了该新建综合医院楼在电气系统设计的主要需求,包括持续供电、扩展性以及安全性需求。针对具体需求提出了相应的电气设计策略,其中涵盖了设计双路供电系统与紧急备用电源、采用模块化与智能化布线系统以及使用分级配电与加强安全防护等关键措施,实现了在保障医院日常运营和应对紧急情况下电力供应的可靠性、灵活性和安全性方面的目标,以此为相关人员提供实践参考。

基于电力电子变压器的新型贯通式同相供电变流器

本文在对同相供电系统分类研究的基础上提出了一种基于单相-单相电力电子变压器(PET)的新型贯通式同相供电变流器电路拓扑。相对于传统的基于工频变压器的同相供电变流器方案,该拓扑可以取消工频变压器,并大幅减少低频滤波电感数量;相对于模块化多电平变流器(MMC)的方案,所提出的拓扑所需储能电容和低频滤波电感数量均可减少60%以上,而功率半导体数量几乎不变,可显著提升系统功率密度,降低系统造价。此外,当单台PET故障时系统可继续降额运行,而非系统全部停运,可靠性高。本文分析了所提出拓扑的工作原理并设计了控制策略。在所搭建的基于单相-单相PET的20MV·A贯通式牵引同相供电变流器模型上的仿真结果验证了该拓扑的正确性和有效性。

电气化铁道贯通同相供电变电所控制策略研究

针对现行换相式和同相牵引供电系统的特点,分析一种采用直接三相-单相交直交变换型贯通同相供电系统方案。该方案既能解决牵引供电系统电能质量问题,又能取消掉牵引网上的薄弱环节"电分相",有利于高速、重载机车实现全线贯通运行。针对贯通供电变电所控制方式,提出采用直接功率控制策略。该方法以瞬时无功理论为基础,控制三相侧和单相侧功率交换。仿真结果表明,在有功和无功指令突变的情况下,变流器能够进行快速跟踪指令,有良好的控制效果。