基于无输出变压器的贯通式牵引供电系统控制策略研究

The traction power supply system is the power source of the electric railway, and also an important load of the power grid system. Its performance directly influences both the electric railway and the power grid. Due to the problems appeared on the existing traction power supply system, such as power quality and neutral section crossing, this project aims to take the diode-clamped multilevel three-phase to single-phase converter as an elementary unit; design a multilevel cascaded converter based traction substation structure ; build an advanced traction power supply system which contains no output transformers. Through the collaborative research of the control strategy of multilevel three-phase rectifier, the 2nd order rippled DC-link voltage rejection strategy, the phase-shift SVPWM modulation strategy of the single-phase multilevel H-bridge and the grid-connected control strategy of the cascaded converter, the cooperative control strategy of the cascaded converter is established. By means of the study on the circulation distribution character of the advanced traction power supply system, the circulation restrain strategy, the grid-built/connected control strategy, the load-flow comprehensive control strategy and the resonance restrain strategy, this project proposes an improved droop current-sharing control strategy, a faked master-slave grid built/connected control strategy and a load-flow comprehensive control strategy which is able to respond to the dynamic changes of the traction load, restrain the system's circulation and reduce the system loss. And then, a systematic structure and research frame are constructed which includes an advanced traction power supply system and its control strategy. This project provides theoretical support and experimental method for further study on the advanced traction power supply system. In addition, it is a pre-research of system's industrialization.

牵引供电系统是电气化铁路的动力源，是电力系统的重要负载，它的优劣直接影响此两系统。针对既有牵引供电系统电能质量和过分相等问题，项目以多电平二极管箝位三相-单相变换器为基本单元，设计基于多电平级联变换器的牵引变电所结构，建立基于无输出变压器的贯通式牵引供电系统。通过对多电平三相整流器控制、直流电压二次脉动抑制、H桥单相多电平相移SVPWM调制、级联变换器并网控制等核心问题的协同研究，建立级联变换器协调控制策略；通过对贯通式牵引供电系统环流分布特性、环流抑制策略、建网/并网控制策略、潮流综合控制策略以及谐振抑制策略的研究，提出改进型下垂均流控制策略、系统伪主从建网/并网控制策略、计及牵引负荷动态变化且可抑制系统环流和能减小系统损耗的潮流综合控制策略;构建贯通式牵引供电系统及其控制策略的体系结构和研究框架，为进一步研究贯通式牵引供电系统提供理论支撑和实验方法，为该系统的产业化进行前期预研。

本项目针对既有牵引供电系统中电能质量和电分相等问题，以多电平二极管箝位三相-单相变换器为基本单元，设计了基于多电平级联变换器的牵引变电所结构，建立了基于无输出变压器的贯通式牵引供电系统,可彻底解决电能质量和电分相等问题。重点研究了多电平三相整流器控制、直流电压二次脉动抑制、H 桥单相多电平相移SVPWM 调制、级联变换器并网控制等关键问题，建立了针对该系统的协调控制策略；深入分析了贯通式牵引供电系统环流分布特性，研究了环流抑制策略、建网/并网控制策略、潮流综合控制策略以及谐振抑制策略，并提出了改进型下垂均流控制策略、系统伪主从建网/并网控制策略、以及牵引负荷动态变化且可抑制系统环流和能减小系统损耗的潮流综合控制策略; 在理论分析的基础上，本项目搭建了基于多电平三相-单相变换器级联的小功率实验电路，通过HDL语言编写各控制算法的控制程序，基于现场可编程逻辑门列阵设计全数字控制器，完成了变电所系统的并网和贯通式供电系统的仿真和实验，验证了所提出的相关控制策略的有效性和正确性。因此，本项目的研究是贯通式牵引供电系统研究的最新探索，为其进一步科学研究、科技开发、工程化和产业化提供前期的理论研究和系统的实验验证奠定基础。