【作者】 王卫安；

【导师】 桂卫华； 阳春华；

【作者基本信息】 中南大学 ， 控制科学与工程， 2014， 博士

【摘要】 铁路运输作为公认的能耗低、环境污染小的绿色交通运输方式,近年来在我国得到了快速发展,机车运行密度和单机功率均处于世界前列。然而,由于我国电网发展相对滞后,电气化铁路给这种相对薄弱电网带来的电能治理问题凸显。近年来,随着交-直-交电力机车的推广,负序电流和宽频域谐波已成为主要的电能质量问题。特别是交-直-交、交-直这两类机车混跑时,经常出现车网谐振和交-直机车阻容烧损等现象,这不仅威胁到机车自身的安全运行,更影响到同网其他用户的正常生产和生活；又由于交-直机车的保有量大,两类机车混跑局面将在我国长期存在,因此该类电能质量问题已成为业界学者研究的热点。众学者主要对采用降压变压器多重化H桥背靠背并联的铁路静止功率调节器(RPC)及其与静止无功补偿器(SVC)组成的混合方式展开研究,但是由于多绕组变压器带来了损耗高、占地面积大等问题,而且受单个开关器件通载能力的限制,难以实现大容量的功率调节和谐波抑制。为此,在总结现有技术的基础上,本文分析了两类机车混跑下的牵引网谐波和负序特性,对基于MMC的铁路静止功率调节器(MRPC)的运行原理及相关控制技术展开研究,其主要研究和创新性成果如下：(1)提出了MRPC新拓扑结构,其利用半桥级联技术实现了低压开关器件在高压系统中的直接应用,消除了变压器带来的延时、相移、占地多和成本高等问题；同时,牵引网之间的能量可通过MRPC的高压直流母线进行融通,双向传输的能量几乎不受限制,避免了传统RPC装置直流电流大而导致的散热问题和低感设计难题。另外,由于是多个逆变模块单元级联,MRPC的等效开关频率高,能方便实现对谐波的精确补偿。随后对两桥臂、三桥臂和四桥臂MRPC的工作原理进行了分析,并对其优缺点及适用场合进行了对比研究。(2)以V/v牵引变电所为对象,分析了RPC两个端口输出的电流幅值、相角与负序电流的关系,建立了在电压波动范围、总功率因数、装置容量、变压器容量、有功平衡约束下的负序电流模值最小的多维非线性约束数学模型,并提出了基于序列二次规划的牵引供电系统负序电流的自适应优化算法。该算法根据检测到的负载情况,自动获取RPC的指令电流最优解；该算法计算速度快、精度高,可以满足实时优化的需要。(3)分析了三桥臂MRPC补偿系统的电压、电流、功率电气量数学关系,对其控制关键技术进行了研究,然后提出了适用于电网不同工况的基于二阶广义积分器(SOGI)的系统负序和无功检测方法,进而提出了两相静止坐标系下基于比例谐振(PR)调节器的控制方案,在保证直流环节电压稳定的前提下,实现了对牵引网负序和无功的有效补偿,同时减小了MRPC的桥臂环流。(4)针对宽频域谐波问题,提出了基于MRPC与高通滤波器(HPF)的混合谐波抑制方法,利用MRPC对低次谐波进行抑制,而HPF对高次谐波进行吸收。针对MRPC的谐波抑制,在分析传统的SOGI控制方法对谐波检测分离及补偿原理的基础上,针对其不能单独提取某次谐波的不足,提出了改进型SOGI算法,并应用PR调节器,实现了对特定次谐波的精确提取和补偿。(5)根据某牵引变电所的参数,对两相三桥臂MRPC的支撑电容、输出电感、开关器件等关键部件参数进行了计算,并搭建了基于RT-LAB的MRPC实时仿真模型,对系统参数、检测方法和控制策略进行了验证。结果表明,本文所提出的MRPC系统能有效实现牵引网负序和谐波的综合治理,并具有良好的动态性能。更多还原

【Abstract】 As a green transportation way with low energy loss and low pollution, railway transportation has been developed rapidly in China, which makes its transportation density and unit-power at the forefront of the world. However, with comparatively slow development of China grid, it faces great challenge to electrified railway on power quality improvement. Currently, the negative-sequence current and wide-band frequency harmonic are coming as the main problems in power supply with the increasing of AC-DC-AC locomotives, which frequently leading to the damage of RC and circuit resonance, especially in the situation of two kinds of locomotive being mixed run. It not only threatens locomotives safe operating, but also influences the production and life of people who sharing the same grid. As there are a large number of AC-DC locomotives, the phenomenon of mixed-running will exist for a long time, as well as the problem of power quality. That’s why it has been a hotspot for many scholars in this field to research on. It mainly depends on the combination mode of railway static power conditioner (RPC, which is comprised by converter based on back to back parallel H-Bridge and step-up transformer) and Static Var Compensator (SVC). However multi winding transformer has the shortages of high loss and big volume, meanwhile with the current capacity limit of single switching device, it is hard to realize a large capacity power regulation and harmonic suppression. Therefore, based on the summary of current technologies, it analyzed the harmonic characteristic of two kinds of locomotive mixed run, and researched the operation principles and control techniques of the modular multi-level railway static power conditioner (MRPC).The main innovative results are listed as follows.(1) A new MRPC topology is proposed, which can realize the direct application of low voltage devices in high voltage system by adopting half-bridge cascaded technology, and the problems which brought by transformers such as time delay, phase shift, room occupation and cost can be resolved. Furthermore, because the energy transmission of MRPC is realized through high voltage DC bus, and its DC current is low and the energy of bi-directional transmission is almost unrestricted, the difficult problems of heat dissipation and low-inductance design caused by high DC current in traditional RPC are avoided. In addition, equivalent high frequency is obtained with the cascaded design of multiple converters, and utilization of low frequency device which is beneficial to realize compensation for harmonic and reactive power. Then the operating principles of two bridge-arm, three bridge-arm and four bridge-arm MRPC topologies are analyzed, and their advantages and disadvantages, applicable fields are comparatively studied in detail.(2) Taking V/V traction substation as a research object, the relationship between current amplitude and phase Angle of RPC and negative sequence current is analyzed, and the mathematic model of the minimum negative sequence current is established under the restraining conditions of voltage fluctuation, total power factor, device capacity, transformer capacity and active power balance. In order to resolve the multidimensional nonlinear constrained optimization problem, a self-adaptive optimization algorithm based on the sequence quadratic programming traction power supply negative sequence current is proposed. According to the load condition, the optimal value of RPC instruction current amplitude and phase angle is achieved based on the real-time optimization. The calculating speed was nearly to5ms every time, the efficiency of precise operations was satisfied for the need of real-time optimization.(3) Analysis of three MRPC engineering application focus on voltage, current, power, electrical mathematic relationships and make a research into its key control technology. Raised out detection methods suitable for grid applications based on SOGI system negative sequence and reactive power, also two-phase stationary coordinate of PR regulator control proposal has been introduced to actively compensate traction negative sequence and active power in guarantee of DC voltage stable, to reduce the MRPC leg circulation current. (4) Aiming at the problem of wide-band frequency harmonic, the combined harmonic suppression method based on MRPC and HPF is proposed, the former is used to suppress the low-order harmonic,and the latter is used to absorb the high-order harmonic. For the sake of improving the harmonic extraction accuracy based on traditional second-order generalized integrator, the upgrade method is consisting of the second-order generalized integrator and PR adjustor is proposed, which is beneficial to separate the specific form characteristic harmonic, and guarantee the precision of compensation.(5) According to the parameters of a certain traction substation, the parameters of three bridge-arm MRPC is calculated, including DC-link capacitance, sub-module capacitance, bridge-arm inductance, output inductance and switching devices, etc. The system parameter and control strategy are verified by the RT-LAB real-time simulation platform. The simulation results show that the mixed system of MRPC and HPF can realize the integrated compensation of harmonic and negative sequence current, together with a better dynamic performance.更多还原