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.

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.

新型混合式贯通牵引供电系统及其复合控制策略

电分相与负序等电能质量问题是制约电气化铁路向高速化、重载化发展的桎梏。贯通牵引供电系统为消弭上述问题提供了契机,但既有贯通方案依然存在所需器件数目多、改造成本高、可靠性差等弊端。为此,在充分利用既有牵引变压器基础上,该文设计一种新型混合式贯通牵引供电装置。该装置通过共直流侧与功率均分手段有效抵消输入侧纹波功率,降低有源/无源器件数目与电容容量。同时,针对直流侧二次纹波与负荷功率冲击,提出一种输入端口复合控制策略,有效解决纹波传递与冲击波动问题。最后通过仿真与实验验证所提装置及其控制策略的可行性与可靠性。

考虑架构灵活重构的混合式贯通牵引供电装置应急管控与故障恢复策略

基于牵引变压器与两相交流输入至单相交流输出(两相-单相)变换单元的混合式贯通牵引供电系统(HATPSS)凭借其设备利用率高、改造成本低等优势而受到关注。然而,两相-单相变换单元作为系统中的薄弱环节,其任意端口故障会导致系统出现负序电流与功率缺失等问题,严重者将引发整个贯通系统失稳。此外,受HATPSS供电架构特殊性及其控制目标多样性的影响,传统牵引系统冗余备用方案与应急管控技术适用性差等问题突出。鉴于此,该文针对两相-单相变换单元的输入/输出端故障工况,综合考虑牵引站中既有设备应急管控潜能与两相-单相变换单元控制自由度的特点,分别提出面向HATPSS的应急管控与故障恢复策略。仅通过牵引变压器、联络开关、两相-单相变换单元等系统既有装置间的协同配合,实现在不同故障工况下HATPSS额定功率运行与负序电流抑制。最后,仿真与实验验证了在不同工况下该文所提应急管控策略的可行性与有效性。

高频隔离型两相-单相贯通牵引供电装置及其控制策略

基于电力电子技术的贯通牵引供电系统为同时解决负序电能质量与电分相问题提供了契机,然而,现行贯通改造方案依然存在功率密度低、改造成本高等问题。为此,文中提出一种高频隔离型两相-单相贯通牵引供电装置及其控制策略,所提装置在充分利用既有两相牵引变压器的基础上,采用三端口高频隔离型直流变换器连接输入输出侧,减小装置体积的同时提升系统功率密度,有效降低贯通系统改造成本。此外,针对贯通牵引供电装置内存在的电能质量问题,提出一种二次纹波消除与功率均分控制策略,在有效抑制直流侧二次纹波与负序电能质量问题的同时,进一步减小了装置直流侧电容容值的选型,最高可达94.95%。最后,通过仿真与实验验证所提装置及其控制策略的可行性与可靠性。

贯通式供电中三相-单相MMC及其控制

基于模块化多电平变换器(MMC)结构的五电平三相-单相变换器,研究了其在贯通式同相供电系统中的应用。以保证MMC子模块(SM)电容电压平衡为前提,在改进的d,q坐标系下分别建立了三相MMC-PWM变换器与单相MMC-PWM变换器系统数学模型,以能量均分和电压平衡为原则,给出了三相-单相MMC-PWM变换器详细控制策略,实现了输出有功无功解耦,输出电压频率、相位和幅值可控以及能灵活地向牵引网传递定量的有功与无功功率。最后通过系统仿真与原理样机实验充分验证了所提系统的合理性以及该系统在该控制方案下能保证正常工作且具备良好的动稳态性能。

基于级联-并联变换器的贯通式牵引变电所系统研究

为了解决既有电气化铁路存在的电分相、无功、负序与谐波问题,以及贯通式牵引变电所容量问题,提出一种基于级联-并联变换器的贯通式牵引变电所系统。牵引变电所采用二极管钳位型三电平NPC变换器作为基本结构,同时采用变换器级联和并联实现牵引变电所的容量提升,通过载波移相空间矢量脉宽调制SVPWM策略控制变换器输出电压。深入分析变电所内变换器并联产生环流的原因,设计了将双闭环控制与下垂控制策略结合的共享同步信号环流抑制策略,并首次应用于级联-并联变换器的牵引变电所系统,抑制系统内环流。通过仿真验证该结构的可行性,并通过小功率实验平台验证控制策略与调制策略的正确性。

基于ADPSS的电力系统和牵引供电系统机电–电磁暂态混合仿真

目前在牵引供电系统对电力系统的影响研究中,大多只单一对牵引供电系统建立详细仿真模型,而电力系统侧则是采用简化后的电路代替,缺乏一种实际电力系统与牵引供电系统的联合仿真模型,对电力系统–牵引供电系统的相互作用与影响认识不足。文中在牵引供电系统电磁仿真模型的基础上,基于电力系统全数字仿真装置(advanced digital power system simulator,ADPSS)搭建出了牵引供电系统与实际电网系统的机电–电磁暂态混合仿真模型,并将混合仿真计算结果与典型值相比较,验证了混合仿真的正确性,并研究分析了牵引供电系统负荷特性、牵引供电系统对电力系统的影响。

用于贯通式牵引供电系统变换器的谐波分析

研究目的:基于三相—单相变换器的贯通式牵引供电系统可以彻底取消牵引网电分相及其相关装置,并可极大地改善三相电网和牵引供电系统电能质量。本文针对用于该系统的核心设备三相—单相变换器的各部分谐波进行了理论计算,并利用Matlab/Simulink搭建了仿真模型,并完成了仿真验证。研究结论:(1)采用SPWM调制的单相变换器,若开关频率远高于牵引网电压频率,则可抑制和消除高次谐波,使输出单相电压谐波主要集中在3、5、7、9等低次谐波,但单相逆变器从直流侧吸取的电流必然含有二次谐波;(2)采用SVPWM调制的三相整流器,三相电网侧输入的电压中不含3倍频的谐波,输入电流总谐波随滤波电感的增大而降低,并随直流电压的增大而增大;(3)给出各部分谐波幅值的计算方法,可通过计算机编程计算得出;(4)本文的研究结论可为进一步研究贯通式牵引供电系统产生谐波、谐振及其抑制和交直交变换器谐波特性提供理论依据。

应用于贯通供电系统的两相–单相变换器直流电压纹波特性与功率均衡控制

传统牵引供电方式存在不平衡、无功及谐波等电能质量问题,且无法实现多变电所互联互通,严重制约高速、重载铁路的发展。为解决这些问题,该文在现有牵引变电所的基础上,提出一种基于两相–单相变换器构建贯通牵引供电的新方案。分析功率流动对所提拓扑直流电压的影响,给出直流电容容值设计边界的计算公式。为抑制两相变换器功率不平衡对三相电能质量的影响,提出一种两相功率均衡控制策略。最后,在YNvd牵引变压器的基础上,仿真和实验验证所提拓扑应用在贯通供电系统的可行性,并验证所提功率均衡控制策略降低三相电网电流不平衡度的有效性。